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gpgv
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gpgv is an OpenPGP signature verification tool. This program is actually a stripped-down version of gpg which is only able to check signatures. It is somewhat smaller than the fully-blown gpg and uses a different (and simpler) way to check that the public keys used to make the signature are valid. There are no configuration files and only a few options are implemented. gpgv assumes that all keys in the keyring are trustworthy. That does also mean that it does not check for expired or revoked keys. If no --keyring option is given, gpgv looks for a ``default'' keyring named ‘trustedkeys.kbx’ (preferred) or ‘trustedkeys.gpg’ in the home directory of GnuPG, either the default home directory or the one set by the --homedir option or the GNUPGHOME environment variable. If any --keyring option is used, gpgv will not look for the default keyring. The --keyring option may be used multiple times and all specified keyrings will be used together. RETURN VALUE The program returns 0 if everything is fine, 1 if at least one signature was bad, and other error codes for fatal errors.
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gpgv - Verify OpenPGP signatures
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gpgv [options] signed_files
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gpgv recognizes these options: --verbose -v Gives more information during processing. If used twice, the input data is listed in detail. --quiet -q Try to be as quiet as possible. --keyring file Add file to the list of keyrings. If file begins with a tilde and a slash, these are replaced by the HOME directory. If the filename does not contain a slash, it is assumed to be in the home-directory ("~/.gnupg" if --homedir is not used). --output file -o file Write output to file; to write to stdout use -. This option can be used to get the signed text from a cleartext or binary signature; it also works for detached signatures, but in that case this option is in general not useful. Note that an existing file will be overwritten. --status-fd n Write special status strings to the file descriptor n. See the file DETAILS in the documentation for a listing of them. --logger-fd n Write log output to file descriptor n and not to stderr. --log-file file Same as --logger-fd, except the logger data is written to file file. Use ‘socket://’ to log to socket. --ignore-time-conflict GnuPG normally checks that the timestamps associated with keys and signatures have plausible values. However, sometimes a signature seems to be older than the key due to clock problems. This option turns these checks into warnings. --homedir dir Set the name of the home directory to dir. If this option is not used, the home directory defaults to ‘~/.gnupg’. It is only recognized when given on the command line. It also overrides any home directory stated through the environment variable ‘GNUPGHOME’ or (on Windows systems) by means of the Registry entry HKCU\Software\GNU\GnuPG:HomeDir. On Windows systems it is possible to install GnuPG as a portable application. In this case only this command line option is considered, all other ways to set a home directory are ignored. --weak-digest name Treat the specified digest algorithm as weak. Signatures made over weak digests algorithms are normally rejected. This option can be supplied multiple times if multiple algorithms should be considered weak. MD5 is always considered weak, and does not need to be listed explicitly. --enable-special-filenames This option enables a mode in which filenames of the form ‘-&n’, where n is a non-negative decimal number, refer to the file descriptor n and not to a file with that name. --assert-pubkey-algo algolist This option works in the same way as described for gpg.
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gpgv pgpfile gpgv sigfile [datafile] Verify the signature of the file. The second form is used for detached signatures, where sigfile is the detached signature (either ASCII-armored or binary) and datafile contains the signed data; if datafile is "-" the signed data is expected on stdin; if datafile is not given the name of the file holding the signed data is constructed by cutting off the extension (".asc", ".sig" or ".sign") from sigfile. FILES ~/.gnupg/trustedkeys.gpg The default keyring with the allowed keys. ENVIRONMENT HOME Used to locate the default home directory. GNUPGHOME If set directory used instead of "~/.gnupg". SEE ALSO gpg(1) The full documentation for this tool is maintained as a Texinfo manual. If GnuPG and the info program are properly installed at your site, the command info gnupg should give you access to the complete manual including a menu structure and an index. GnuPG 2.4.5 2024-03-04 GPGV(1)
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gsha512sum
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Print or check SHA512 (512-bit) checksums. With no FILE, or when FILE is -, read standard input. -b, --binary read in binary mode -c, --check read checksums from the FILEs and check them --tag create a BSD-style checksum -t, --text read in text mode (default) -z, --zero end each output line with NUL, not newline, and disable file name escaping The following five options are useful only when verifying checksums: --ignore-missing don't fail or report status for missing files --quiet don't print OK for each successfully verified file --status don't output anything, status code shows success --strict exit non-zero for improperly formatted checksum lines -w, --warn warn about improperly formatted checksum lines --help display this help and exit --version output version information and exit The sums are computed as described in FIPS-180-2. When checking, the input should be a former output of this program. The default mode is to print a line with: checksum, a space, a character indicating input mode ('*' for binary, ' ' for text or where binary is insignificant), and name for each FILE. Note: There is no difference between binary mode and text mode on GNU systems. AUTHOR Written by Ulrich Drepper, Scott Miller, and David Madore. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO cksum(1) Full documentation <https://www.gnu.org/software/coreutils/sha512sum> or available locally via: info '(coreutils) sha2 utilities' GNU coreutils 9.3 April 2023 SHA512SUM(1)
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sha512sum - compute and check SHA512 message digest
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sha512sum [OPTION]... [FILE]...
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msgconv
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Converts a translation catalog to a different character encoding. Mandatory arguments to long options are mandatory for short options too. Input file location: INPUTFILE input PO file -D, --directory=DIRECTORY add DIRECTORY to list for input files search If no input file is given or if it is -, standard input is read. Output file location: -o, --output-file=FILE write output to specified file The results are written to standard output if no output file is specified or if it is -. Conversion target: -t, --to-code=NAME encoding for output The default encoding is the current locale's encoding. Input file syntax: -P, --properties-input input file is in Java .properties syntax --stringtable-input input file is in NeXTstep/GNUstep .strings syntax Output details: --color use colors and other text attributes always --color=WHEN use colors and other text attributes if WHEN. WHEN may be 'always', 'never', 'auto', or 'html'. --style=STYLEFILE specify CSS style rule file for --color -e, --no-escape do not use C escapes in output (default) -E, --escape use C escapes in output, no extended chars --force-po write PO file even if empty -i, --indent indented output style --no-location suppress '#: filename:line' lines -n, --add-location preserve '#: filename:line' lines (default) --strict strict Uniforum output style -p, --properties-output write out a Java .properties file --stringtable-output write out a NeXTstep/GNUstep .strings file -w, --width=NUMBER set output page width --no-wrap do not break long message lines, longer than the output page width, into several lines -s, --sort-output generate sorted output -F, --sort-by-file sort output by file location Informative output: -h, --help display this help and exit -V, --version output version information and exit AUTHOR Written by Bruno Haible. REPORTING BUGS Report bugs in the bug tracker at <https://savannah.gnu.org/projects/gettext> or by email to <bug-gettext@gnu.org>. COPYRIGHT Copyright © 2001-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO The full documentation for msgconv is maintained as a Texinfo manual. If the info and msgconv programs are properly installed at your site, the command info msgconv should give you access to the complete manual. GNU gettext-tools 0.22.5 February 2024 MSGCONV(1)
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msgconv - character set conversion for message catalog
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msgconv [OPTION] [INPUTFILE]
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z3
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rview
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Vim is a text editor that is upwards compatible to Vi. It can be used to edit all kinds of plain text. It is especially useful for editing programs. There are a lot of enhancements above Vi: multi level undo, multi windows and buffers, syntax highlighting, command line editing, filename completion, on-line help, visual selection, etc.. See ":help vi_diff.txt" for a summary of the differences between Vim and Vi. While running Vim a lot of help can be obtained from the on-line help system, with the ":help" command. See the ON-LINE HELP section below. Most often Vim is started to edit a single file with the command vim file More generally Vim is started with: vim [options] [filelist] If the filelist is missing, the editor will start with an empty buffer. Otherwise exactly one out of the following four may be used to choose one or more files to be edited. file .. A list of filenames. The first one will be the current file and read into the buffer. The cursor will be positioned on the first line of the buffer. You can get to the other files with the ":next" command. To edit a file that starts with a dash, precede the filelist with "--". - The file to edit is read from stdin. Commands are read from stderr, which should be a tty. -t {tag} The file to edit and the initial cursor position depends on a "tag", a sort of goto label. {tag} is looked up in the tags file, the associated file becomes the current file and the associated command is executed. Mostly this is used for C programs, in which case {tag} could be a function name. The effect is that the file containing that function becomes the current file and the cursor is positioned on the start of the function. See ":help tag-commands". -q [errorfile] Start in quickFix mode. The file [errorfile] is read and the first error is displayed. If [errorfile] is omitted, the filename is obtained from the 'errorfile' option (defaults to "AztecC.Err" for the Amiga, "errors.err" on other systems). Further errors can be jumped to with the ":cn" command. See ":help quickfix". Vim behaves differently, depending on the name of the command (the executable may still be the same file). vim The "normal" way, everything is default. ex Start in Ex mode. Go to Normal mode with the ":vi" command. Can also be done with the "-e" argument. view Start in read-only mode. You will be protected from writing the files. Can also be done with the "-R" argument. gvim gview The GUI version. Starts a new window. Can also be done with the "-g" argument. evim eview The GUI version in easy mode. Starts a new window. Can also be done with the "-y" argument. rvim rview rgvim rgview Like the above, but with restrictions. It will not be possible to start shell commands, or suspend Vim. Can also be done with the "-Z" argument.
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vim - Vi IMproved, a programmer's text editor
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vim [options] [file ..] vim [options] - vim [options] -t tag vim [options] -q [errorfile] ex view gvim gview evim eview rvim rview rgvim rgview
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The options may be given in any order, before or after filenames. Options without an argument can be combined after a single dash. +[num] For the first file the cursor will be positioned on line "num". If "num" is missing, the cursor will be positioned on the last line. +/{pat} For the first file the cursor will be positioned in the line with the first occurrence of {pat}. See ":help search-pattern" for the available search patterns. +{command} -c {command} {command} will be executed after the first file has been read. {command} is interpreted as an Ex command. If the {command} contains spaces it must be enclosed in double quotes (this depends on the shell that is used). Example: vim "+set si" main.c Note: You can use up to 10 "+" or "-c" commands. -S {file} {file} will be sourced after the first file has been read. This is equivalent to -c "source {file}". {file} cannot start with '-'. If {file} is omitted "Session.vim" is used (only works when -S is the last argument). --cmd {command} Like using "-c", but the command is executed just before processing any vimrc file. You can use up to 10 of these commands, independently from "-c" commands. -A If Vim has been compiled with ARABIC support for editing right-to-left oriented files and Arabic keyboard mapping, this option starts Vim in Arabic mode, i.e. 'arabic' is set. Otherwise an error message is given and Vim aborts. -b Binary mode. A few options will be set that makes it possible to edit a binary or executable file. -C Compatible. Set the 'compatible' option. This will make Vim behave mostly like Vi, even though a .vimrc file exists. -d Start in diff mode. There should between two to eight file name arguments. Vim will open all the files and show differences between them. Works like vimdiff(1). -d {device}, -dev {device} Open {device} for use as a terminal. Only on the Amiga. Example: "-d con:20/30/600/150". -D Debugging. Go to debugging mode when executing the first command from a script. -e Start Vim in Ex mode, just like the executable was called "ex". -E Start Vim in improved Ex mode, just like the executable was called "exim". -f Foreground. For the GUI version, Vim will not fork and detach from the shell it was started in. On the Amiga, Vim is not restarted to open a new window. This option should be used when Vim is executed by a program that will wait for the edit session to finish (e.g. mail). On the Amiga the ":sh" and ":!" commands will not work. --nofork Foreground. For the GUI version, Vim will not fork and detach from the shell it was started in. -F If Vim has been compiled with FKMAP support for editing right-to-left oriented files and Farsi keyboard mapping, this option starts Vim in Farsi mode, i.e. 'fkmap' and 'rightleft' are set. Otherwise an error message is given and Vim aborts. -g If Vim has been compiled with GUI support, this option enables the GUI. If no GUI support was compiled in, an error message is given and Vim aborts. --gui-dialog-file {name} When using the GUI, instead of showing a dialog, write the title and message of the dialog to file {name}. The file is created or appended to. Only useful for testing, to avoid that the test gets stuck on a dialog that can't be seen. Without the GUI the argument is ignored. --help, -h, -? Give a bit of help about the command line arguments and options. After this Vim exits. -H If Vim has been compiled with RIGHTLEFT support for editing right-to-left oriented files and Hebrew keyboard mapping, this option starts Vim in Hebrew mode, i.e. 'hkmap' and 'rightleft' are set. Otherwise an error message is given and Vim aborts. -i {viminfo} Specifies the filename to use when reading or writing the viminfo file, instead of the default "~/.viminfo". This can also be used to skip the use of the .viminfo file, by giving the name "NONE". -L Same as -r. -l Lisp mode. Sets the 'lisp' and 'showmatch' options on. -m Modifying files is disabled. Resets the 'write' option. You can still modify the buffer, but writing a file is not possible. -M Modifications not allowed. The 'modifiable' and 'write' options will be unset, so that changes are not allowed and files can not be written. Note that these options can be set to enable making modifications. -N No-compatible mode. Resets the 'compatible' option. This will make Vim behave a bit better, but less Vi compatible, even though a .vimrc file does not exist. -n No swap file will be used. Recovery after a crash will be impossible. Handy if you want to edit a file on a very slow medium (e.g. floppy). Can also be done with ":set uc=0". Can be undone with ":set uc=200". -nb Become an editor server for NetBeans. See the docs for details. -o[N] Open N windows stacked. When N is omitted, open one window for each file. -O[N] Open N windows side by side. When N is omitted, open one window for each file. -p[N] Open N tab pages. When N is omitted, open one tab page for each file. -P {parent-title} Win32 GUI only: Specify the title of the parent application. When possible, Vim will run in an MDI window inside the application. {parent-title} must appear in the window title of the parent application. Make sure that it is specific enough. Note that the implementation is still primitive. It won't work with all applications and the menu doesn't work. -R Read-only mode. The 'readonly' option will be set. You can still edit the buffer, but will be prevented from accidentally overwriting a file. If you do want to overwrite a file, add an exclamation mark to the Ex command, as in ":w!". The -R option also implies the -n option (see above). The 'readonly' option can be reset with ":set noro". See ":help 'readonly'". -r List swap files, with information about using them for recovery. -r {file} Recovery mode. The swap file is used to recover a crashed editing session. The swap file is a file with the same filename as the text file with ".swp" appended. See ":help recovery". -s Silent mode. Only when started as "Ex" or when the "-e" option was given before the "-s" option. -s {scriptin} The script file {scriptin} is read. The characters in the file are interpreted as if you had typed them. The same can be done with the command ":source! {scriptin}". If the end of the file is reached before the editor exits, further characters are read from the keyboard. -T {terminal} Tells Vim the name of the terminal you are using. Only required when the automatic way doesn't work. Should be a terminal known to Vim (builtin) or defined in the termcap or terminfo file. --not-a-term Tells Vim that the user knows that the input and/or output is not connected to a terminal. This will avoid the warning and the two second delay that would happen. --ttyfail When stdin or stdout is not a a terminal (tty) then exit right away. -u {vimrc} Use the commands in the file {vimrc} for initializations. All the other initializations are skipped. Use this to edit a special kind of files. It can also be used to skip all initializations by giving the name "NONE". See ":help initialization" within vim for more details. -U {gvimrc} Use the commands in the file {gvimrc} for GUI initializations. All the other GUI initializations are skipped. It can also be used to skip all GUI initializations by giving the name "NONE". See ":help gui-init" within vim for more details. -V[N] Verbose. Give messages about which files are sourced and for reading and writing a viminfo file. The optional number N is the value for 'verbose'. Default is 10. -V[N]{filename} Like -V and set 'verbosefile' to {filename}. The result is that messages are not displayed but written to the file {filename}. {filename} must not start with a digit. --log {filename} If Vim has been compiled with eval and channel feature, start logging and write entries to {filename}. This works like calling ch_logfile({filename}, 'ao') very early during startup. -v Start Vim in Vi mode, just like the executable was called "vi". This only has effect when the executable is called "ex". -w{number} Set the 'window' option to {number}. -w {scriptout} All the characters that you type are recorded in the file {scriptout}, until you exit Vim. This is useful if you want to create a script file to be used with "vim -s" or ":source!". If the {scriptout} file exists, characters are appended. -W {scriptout} Like -w, but an existing file is overwritten. -x Use encryption when writing files. Will prompt for a crypt key. -X Don't connect to the X server. Shortens startup time in a terminal, but the window title and clipboard will not be used. -y Start Vim in easy mode, just like the executable was called "evim" or "eview". Makes Vim behave like a click-and-type editor. -Z Restricted mode. Works like the executable starts with "r". -- Denotes the end of the options. Arguments after this will be handled as a file name. This can be used to edit a filename that starts with a '-'. --clean Do not use any personal configuration (vimrc, plugins, etc.). Useful to see if a problem reproduces with a clean Vim setup. --echo-wid GTK GUI only: Echo the Window ID on stdout. --literal Take file name arguments literally, do not expand wildcards. This has no effect on Unix where the shell expands wildcards. --noplugin Skip loading plugins. Implied by -u NONE. --remote Connect to a Vim server and make it edit the files given in the rest of the arguments. If no server is found a warning is given and the files are edited in the current Vim. --remote-expr {expr} Connect to a Vim server, evaluate {expr} in it and print the result on stdout. --remote-send {keys} Connect to a Vim server and send {keys} to it. --remote-silent As --remote, but without the warning when no server is found. --remote-wait As --remote, but Vim does not exit until the files have been edited. --remote-wait-silent As --remote-wait, but without the warning when no server is found. --serverlist List the names of all Vim servers that can be found. --servername {name} Use {name} as the server name. Used for the current Vim, unless used with a --remote argument, then it's the name of the server to connect to. --socketid {id} GTK GUI only: Use the GtkPlug mechanism to run gvim in another window. --startuptime {file} During startup write timing messages to the file {fname}. --version Print version information and exit. --windowid {id} Win32 GUI only: Make gvim try to use the window {id} as a parent, so that it runs inside that window. ON-LINE HELP Type ":help" in Vim to get started. Type ":help subject" to get help on a specific subject. For example: ":help ZZ" to get help for the "ZZ" command. Use <Tab> and CTRL-D to complete subjects (":help cmdline-completion"). Tags are present to jump from one place to another (sort of hypertext links, see ":help"). All documentation files can be viewed in this way, for example ":help syntax.txt". FILES /usr/local/share/vim/vim??/doc/*.txt The Vim documentation files. Use ":help doc-file-list" to get the complete list. vim?? is short version number, like vim91 for Vim 9.1 /usr/local/share/vim/vim??/doc/tags The tags file used for finding information in the documentation files. /usr/local/share/vim/vim??/syntax/syntax.vim System wide syntax initializations. /usr/local/share/vim/vim??/syntax/*.vim Syntax files for various languages. /usr/local/share/vim/vimrc System wide Vim initializations. ~/.vimrc, ~/.vim/vimrc, $XDG_CONFIG_HOME/vim/vimrc Your personal Vim initializations (first one found is used). /usr/local/share/vim/gvimrc System wide gvim initializations. ~/.gvimrc, ~/.vim/gvimrc, $XDG_CONFIG_HOME/vim/gvimrc Your personal gvim initializations (first one found is used). /usr/local/share/vim/vim??/optwin.vim Script used for the ":options" command, a nice way to view and set options. /usr/local/share/vim/vim??/menu.vim System wide menu initializations for gvim. /usr/local/share/vim/vim??/bugreport.vim Script to generate a bug report. See ":help bugs". /usr/local/share/vim/vim??/filetype.vim Script to detect the type of a file by its name. See ":help 'filetype'". /usr/local/share/vim/vim??/scripts.vim Script to detect the type of a file by its contents. See ":help 'filetype'". /usr/local/share/vim/vim??/print/*.ps Files used for PostScript printing. For recent info read the VIM home page: <URL:http://www.vim.org/> SEE ALSO vimtutor(1) AUTHOR Most of Vim was made by Bram Moolenaar, with a lot of help from others. See ":help credits" in Vim. Vim is based on Stevie, worked on by: Tim Thompson, Tony Andrews and G.R. (Fred) Walter. Although hardly any of the original code remains. BUGS Probably. See ":help todo" for a list of known problems. Note that a number of things that may be regarded as bugs by some, are in fact caused by a too-faithful reproduction of Vi's behaviour. And if you think other things are bugs "because Vi does it differently", you should take a closer look at the vi_diff.txt file (or type :help vi_diff.txt when in Vim). Also have a look at the 'compatible' and 'cpoptions' options. 2024 Jun 04 VIM(1)
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metatest
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event_rpcgen.py
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gusers
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Output who is currently logged in according to FILE. If FILE is not specified, use /var/run/utmpx. /var/log/wtmp as FILE is common. --help display this help and exit --version output version information and exit AUTHOR Written by Joseph Arceneaux and David MacKenzie. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO getent(1), who(1) Full documentation <https://www.gnu.org/software/coreutils/users> or available locally via: info '(coreutils) users invocation' GNU coreutils 9.3 April 2023 USERS(1)
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users - print the user names of users currently logged in to the current host
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users [OPTION]... [FILE]
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lame
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LAME is a program which can be used to create compressed audio files. (Lame ain't an MP3 encoder). These audio files can be played back by popular MP3 players such as mpg123 or madplay. To read from stdin, use "-" for <infile>. To write to stdout, use "-" for <outfile>.
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lame - create mp3 audio files
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lame [options] <infile> <outfile>
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Input options: -r Assume the input file is raw pcm. Sampling rate and mono/stereo/jstereo must be specified on the command line. For each stereo sample, LAME expects the input data to be ordered left channel first, then right channel. By default, LAME expects them to be signed integers with a bitwidth of 16 and stored in little-endian. Without -r, LAME will perform several fseek()'s on the input file looking for WAV and AIFF headers. Might not be available on your release. -x Swap bytes in the input file (or output file when using --decode). For sorting out little endian/big endian type problems. If your encodings sounds like static, try this first. Without using -x, LAME will treat input file as native endian. -s sfreq sfreq = 8/11.025/12/16/22.05/24/32/44.1/48 Required only for raw PCM input files. Otherwise it will be determined from the header of the input file. LAME will automatically resample the input file to one of the supported MP3 samplerates if necessary. --bitwidth n Input bit width per sample. n = 8, 16, 24, 32 (default 16) Required only for raw PCM input files. Otherwise it will be determined from the header of the input file. --signed Instructs LAME that the samples from the input are signed (the default for 16, 24 and 32 bits raw pcm data). Required only for raw PCM input files. --unsigned Instructs LAME that the samples from the input are unsigned (the default for 8 bits raw pcm data, where 0x80 is zero). Required only for raw PCM input files and only available at bitwidth 8. --little-endian Instructs LAME that the samples from the input are in little- endian form. Required only for raw PCM input files. --big-endian Instructs LAME that the samples from the input are in big-endian form. Required only for raw PCM input files. --mp1input Assume the input file is a MPEG Layer I (ie MP1) file. If the filename ends in ".mp1" LAME will assume it is a MPEG Layer I file. For stdin or Layer I files which do not end in .mp1 you need to use this switch. --mp2input Assume the input file is a MPEG Layer II (ie MP2) file. If the filename ends in ".mp2" LAME will assume it is a MPEG Layer II file. For stdin or Layer II files which do not end in .mp2 you need to use this switch. --mp3input Assume the input file is a MP3 file. Useful for downsampling from one mp3 to another. As an example, it can be useful for streaming through an IceCast server. If the filename ends in ".mp3" LAME will assume it is an MP3. For stdin or MP3 files which do not end in .mp3 you need to use this switch. --nogap file1 file2 ... gapless encoding for a set of contiguous files --nogapout dir output dir for gapless encoding (must precede --nogap) --out-dir dir If no explicit output file is specified, a file will be written at given path. Ignored when using piped/streamed input Operational options: -m mode mode = s, j, f, d, m, l, r Joint-stereo is the default mode for stereo files. (s)imple stereo (Forced LR) In this mode, the encoder makes no use of potentially existing correlations between the two input channels. It can, however, negotiate the bit demand between both channel, i.e. give one channel more bits if the other contains silence or needs less bits because of a lower complexity. (j)oint stereo In this mode, the encoder can use (on a frame by frame basis) either L/R stereo or mid/side stereo. In mid/side stereo, the mid (L+R) and side (L-R) channels are encoded, and more bits are allocated to the mid channel than the side channel. When there isn't too much stereo separation, this effectively increases the bandwidth, so having higher quality with the same amount of bits. Using mid/side stereo inappropriately can result in audible compression artifacts. Too much switching between mid/side and regular stereo can also sound bad. To determine when to switch to mid/side stereo, LAME uses a much more sophisticated algorithm than the one described in the ISO documentation. (f)orced MS stereo Forces all frames to be encoded with mid/side stereo. It should be used only if you are sure that every frame of the input file has very little stereo separation. (d)ual channel In this mode, the 2 channels will be totally independently encoded. Each channel will have exactly half of the bitrate. This mode is designed for applications like dual languages encoding (for example: English in one channel and French in the other). Using this encoding mode for regular stereo files will result in a lower quality encoding. (m)ono The input will be encoded as a mono signal. If it was a stereo signal, it will be downsampled to mono. The downmix is calculated as the sum of the left and right channel, attenuated by 6 dB. Also note that, if using a stereo RAW PCM stream, you need to use the -a parameter. (l)eft channel only The input will be encoded as a mono signal. If it was a stereo signal, the left channel will be encoded only. (r)ight channel only The input will be encoded as a mono signal. If it was a stereo signal, the right channel will be encoded only. -a Mix the stereo input file to mono and encode as mono. The downmix is calculated as the sum of the left and right channel, attenuated by 6 dB. This option is only needed in the case of raw PCM stereo input (because LAME cannot determine the number of channels in the input file). To encode a stereo RAW PCM input file as mono, use lame -a -m m For WAV and AIFF input files, using -m m will always produce a mono .mp3 file from both mono and stereo input. --freeformat Produces a free format bitstream. With this option, you can use -b with any bitrate higher than 8 kbps. However, even if an mp3 decoder is required to support free bitrates at least up to 320 kbps, many players are unable to deal with it. Tests have shown that the following decoders support free format: in_mpg123 up to 560 kbps l3dec up to 310 kbps LAME up to 640 kbps MAD up to 640 kbps --decode Uses LAME for decoding to a wav file. The input file can be any input type supported by encoding, including layer II files. LAME uses a fork of mpglib known as HIP for decoding. If -t is used (disable wav header), LAME will output raw pcm in native endian format. You can use -x to swap bytes order. This option is not usable if the MP3 decoder was explicitly disabled in the build of LAME. -t Disable writing of the INFO Tag on encoding. This tag is embedded in frame 0 of the MP3 file. It includes some information about the encoding options of the file, and in VBR it lets VBR aware players correctly seek and compute playing times of VBR files. When --decode is specified (decode to WAV), this flag will disable writing of the WAV header. The output will be raw pcm, native endian format. Use -x to swap bytes. --comp arg Instead of choosing bitrate, using this option, user can choose compression ratio to achieve. --scale n --scale-l n --scale-r n Scales input (every channel, only left channel or only right channel) by n. This just multiplies the PCM data (after it has been converted to floating point) by n. n > 1: increase volume n = 1: no effect n < 1: reduce volume Use with care, since most MP3 decoders will truncate data which decodes to values greater than 32768. --replaygain-fast Compute ReplayGain fast but slightly inaccurately. This computes "Radio" ReplayGain on the input data stream after user‐specified volume‐scaling and/or resampling. The ReplayGain analysis does not affect the content of a compressed data stream itself, it is a value stored in the header of a sound file. Information on the purpose of ReplayGain and the algorithms used is available from http://www.replaygain.org/. Only the "RadioGain" Replaygain value is computed, it is stored in the LAME tag. The analysis is performed with the reference volume equal to 89dB. Note: the reference volume has been changed from 83dB on transition from version 3.95 to 3.95.1. This switch is enabled by default. See also: --replaygain-accurate, --noreplaygain --replaygain-accurate Compute ReplayGain more accurately and find the peak sample. This computes "Radio" ReplayGain on the decoded data stream, finds the peak sample by decoding on the fly the encoded data stream and stores it in the file. The ReplayGain analysis does not affect the content of a compressed data stream itself, it is a value stored in the header of a sound file. Information on the purpose of ReplayGain and the algorithms used is available from http://www.replaygain.org/. By default, LAME performs ReplayGain analysis on the input data (after the user‐specified volume scaling). This behavior might give slightly inaccurate results because the data on the output of a lossy compression/decompression sequence differs from the initial input data. When --replaygain-accurate is specified the mp3 stream gets decoded on the fly and the analysis is performed on the decoded data stream. Although theoretically this method gives more accurate results, it has several disadvantages: * tests have shown that the difference between the ReplayGain values computed on the input data and decoded data is usually not greater than 0.5dB, although the minimum volume difference the human ear can perceive is about 1.0dB * decoding on the fly significantly slows down the encoding process The apparent advantage is that: * with --replaygain-accurate the real peak sample is determined and stored in the file. The knowledge of the peak sample can be useful to decoders (players) to prevent a negative effect called 'clipping' that introduces distortion into the sound. Only the "RadioGain" ReplayGain value is computed, it is stored in the LAME tag. The analysis is performed with the reference volume equal to 89dB. Note: the reference volume has been changed from 83dB on transition from version 3.95 to 3.95.1. This option is not usable if the MP3 decoder was explicitly disabled in the build of LAME. (Note: if LAME is compiled without the MP3 decoder, ReplayGain analysis is performed on the input data after user-specified volume scaling). See also: --replaygain-fast, --noreplaygain --clipdetect --noreplaygain Disable ReplayGain analysis. By default ReplayGain analysis is enabled. This switch disables it. See also: --replaygain-fast, --replaygain-accurate --clipdetect Clipping detection. Enable --replaygain-accurate and print a message whether clipping occurs and how far in dB the waveform is from full scale. This option is not usable if the MP3 decoder was explicitly disabled in the build of LAME. See also: --replaygain-accurate --preset type | [cbr] kbps Use one of the built-in presets. Have a look at the PRESETS section below. --preset help gives more infos about the the used options in these presets. --noasm type Disable specific assembly optimizations ( mmx / 3dnow / sse ). Quality will not increase, only speed will be reduced. If you have problems running Lame on a Cyrix/Via processor, disabling mmx optimizations might solve your problem. Verbosity: --disptime n Set the delay in seconds between two display updates. --nohist By default, LAME will display a bitrate histogram while producing VBR mp3 files. This will disable that feature. Histogram display might not be available on your release. -S --silent --quiet Do not print anything on the screen. --verbose Print a lot of information on the screen. --help Display a list of available options. Noise shaping & psycho acoustic algorithms: -q qual 0 <= qual <= 9 Bitrate is of course the main influence on quality. The higher the bitrate, the higher the quality. But for a given bitrate, we have a choice of algorithms to determine the best scalefactors and Huffman encoding (noise shaping). For CBR and ABR, the following table applies: -q 0: Use the best algorithms (Best Huffman coding search, full outer loop, and the highest precision of several parameters). -q 1 to q 4: Similar to -q 0 without the full outer loop and decreasing precision of parameters the further from q0. -q 3 is the default. -q 5 and -q 6: Same as -q 7, but enables noise shaping and increases subblock gain -q 7 to -q 9: Same as -f. Very fast, OK quality. Psychoacoustics are used for pre-echo and mid/side stereo, but no noise-shaping is done. For the default VBR mode since LAME 3.98, the following table applies : -q 0 to -q 4: include all features of the other modes and additionally use the best search when applying Huffman coding. -q 5 and -q 6: include all features of -q7, calculate and consider actual quantisation noise, and additionally enable subblock gain. -q 7 to -q 9 This level uses a psymodel but does not calculate quantisation noise when encoding: it takes a quick guess. -h Alias of -q 2 -f Alias of -q 7 CBR (constant bitrate, the default) options: -b n For MPEG-1 (sampling frequencies of 32, 44.1 and 48 kHz) n = 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 For MPEG-2 (sampling frequencies of 16, 22.05 and 24 kHz) n = 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 For MPEG-2.5 (sampling frequencies of 8, 11.025 and 12 kHz) n = 8, 16, 24, 32, 40, 48, 56, 64 Default is 128 for MPEG1 and 64 for MPEG2 and 32 for MPEG2.5 (64, 32 and 16 respectively in case of mono). --cbr enforce use of constant bitrate. Used to disable VBR or ABR encoding even if their settings are enabled. ABR (average bitrate) options: --abr n Turns on encoding with a targeted average bitrate of n kbits, allowing to use frames of different sizes. The allowed range of n is 8 - 310, you can use any integer value within that range. It can be combined with the -b and -B switches like: lame --abr 123 -b 64 -B 192 a.wav a.mp3 which would limit the allowed frame sizes between 64 and 192 kbits. The use of -B is NOT RECOMMENDED. A 128 kbps CBR bitstream, because of the bit reservoir, can actually have frames which use as many bits as a 320 kbps frame. VBR modes minimize the use of the bit reservoir, and thus need to allow 320 kbps frames to get the same flexibility as CBR streams. VBR (variable bitrate) options: -v use variable bitrate (--vbr-new) --vbr-old Invokes the oldest, most tested VBR algorithm. It produces very good quality files, though is not very fast. This has, up through v3.89, been considered the "workhorse" VBR algorithm. --vbr-new Invokes the newest VBR algorithm. During the development of version 3.90, considerable tuning was done on this algorithm, and it is now considered to be on par with the original --vbr-old. It has the added advantage of being very fast (over twice as fast as --vbr-old ). This is the default since 3.98. -V n 0 <= n <= 9.999 Enable VBR (Variable BitRate) and specifies the value of VBR quality (default = 4). Decimal values can be specified, like 4.51. 0 = highest quality. ABR and VBR options: -b bitrate For MPEG-1 (sampling frequencies of 32, 44.1 and 48 kHz) n = 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 For MPEG-2 (sampling frequencies of 16, 22.05 and 24 kHz) n = 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 For MPEG-2.5 (sampling frequencies of 8, 11.025 and 12 kHz) n = 8, 16, 24, 32, 40, 48, 56, 64 Specifies the minimum bitrate to be used. However, in order to avoid wasted space, the smallest frame size available will be used during silences. -B bitrate For MPEG-1 (sampling frequencies of 32, 44.1 and 48 kHz) n = 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 For MPEG-2 (sampling frequencies of 16, 22.05 and 24 kHz) n = 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 For MPEG-2.5 (sampling frequencies of 8, 11.025 and 12 kHz) n = 8, 16, 24, 32, 40, 48, 56, 64 Specifies the maximum allowed bitrate. Note: If you own an mp3 hardware player build upon a MAS 3503 chip, you must set maximum bitrate to no more than 224 kpbs. -F Strictly enforce the -b option. This is mainly for use with hardware players that do not support low bitrate mp3. Without this option, the minimum bitrate will be ignored for passages of analog silence, i.e. when the music level is below the absolute threshold of human hearing (ATH). Experimental options: -X n 0 <= n <= 7 When LAME searches for a "good" quantization, it has to compare the actual one with the best one found so far. The comparison says which one is better, the best so far or the actual. The -X parameter selects between different approaches to make this decision, -X0 being the default mode: -X0 The criteria are (in order of importance): * less distorted scalefactor bands * the sum of noise over the thresholds is lower * the total noise is lower -X1 The actual is better if the maximum noise over all scalefactor bands is less than the best so far. -X2 The actual is better if the total sum of noise is lower than the best so far. -X3 The actual is better if the total sum of noise is lower than the best so far and the maximum noise over all scalefactor bands is less than the best so far plus 2dB. -X4 Not yet documented. -X5 The criteria are (in order of importance): * the sum of noise over the thresholds is lower * the total sum of noise is lower -X6 The criteria are (in order of importance): * the sum of noise over the thresholds is lower * the maximum noise over all scalefactor bands is lower * the total sum of noise is lower -X7 The criteria are: * less distorted scalefactor bands or * the sum of noise over the thresholds is lower -Y lets LAME ignore noise in sfb21, like in CBR MP3 header/stream options: -e emp emp = n, 5, c n = (none, default) 5 = 0/15 microseconds c = citt j.17 All this does is set a flag in the bitstream. If you have a PCM input file where one of the above types of (obsolete) emphasis has been applied, you can set this flag in LAME. Then the mp3 decoder should de-emphasize the output during playback, although most decoders ignore this flag. A better solution would be to apply the de-emphasis with a standalone utility before encoding, and then encode without -e. -c Mark the encoded file as being copyrighted. -o Mark the encoded file as being a copy. -p Turn on CRC error protection. It will add a cyclic redundancy check (CRC) code in each frame, allowing to detect transmission errors that could occur on the MP3 stream. However, it takes 16 bits per frame that would otherwise be used for encoding, and then will slightly reduce the sound quality. --nores Disable the bit reservoir. Each frame will then become independent from previous ones, but the quality will be lower. --strictly-enforce-ISO With this option, LAME will enforce the 7680 bit limitation on total frame size. This results in many wasted bits for high bitrate encodings but will ensure strict ISO compatibility. This compatibility might be important for hardware players. Filter options: --lowpass freq Set a lowpass filtering frequency in kHz. Frequencies above the specified one will be cutoff. --lowpass-width freq Set the width of the lowpass filter. The default value is 15% of the lowpass frequency. --highpass freq Set an highpass filtering frequency in kHz. Frequencies below the specified one will be cutoff. --highpass-width freq Set the width of the highpass filter in kHz. The default value is 15% of the highpass frequency. --resample sfreq sfreq = 8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48 Select output sampling frequency (only supported for encoding). If not specified, LAME will automatically resample the input when using high compression ratios. ID3 tag options: --tt title audio/song title (max 30 chars for version 1 tag) --ta artist audio/song artist (max 30 chars for version 1 tag) --tl album audio/song album (max 30 chars for version 1 tag) --ty year audio/song year of issue (1 to 9999) --tc comment user-defined text (max 30 chars for v1 tag, 28 for v1.1) --tn track[/total] audio/song track number and (optionally) the total number of tracks on the original recording. (track and total each 1 to 255. Providing just the track number creates v1.1 tag, providing a total forces v2.0). --tg genre audio/song genre (name or number in list) --tv id=value Text or URL frame specified by id and value (v2.3 tag). User defined frame. Syntax: --tv "TXXX=description=content" --add-id3v2 force addition of version 2 tag --id3v1-only add only a version 1 tag --id3v2-only add only a version 2 tag --id3v2-latin1 add following options in ISO-8859-1 text encoding. --id3v2-utf16 add following options in unicode text encoding. --space-id3v1 pad version 1 tag with spaces instead of nulls --pad-id3v2 same as --pad-id3v2-size 128 --pad-id3v2-size num adds version 2 tag, pad with extra "num" bytes --genre-list print alphabetically sorted ID3 genre list and exit --ignore-tag-errors ignore errors in values passed for tags, use defaults in case an error occurs Analysis options: -g run graphical analysis on <infile>. <infile> can also be a .mp3 file. (This feature is a compile time option. Your binary may for speed reasons be compiled without this.) ID3 TAGS LAME is able to embed ID3 v1, v1.1 or v2 tags inside the encoded MP3 file. This allows to have some useful information about the music track included inside the file. Those data can be read by most MP3 players. Lame will smartly choose which tags to use. It will add ID3 v2 tags only if the input comments won't fit in v1 or v1.1 tags, i.e. if they are more than 30 characters. In this case, both v1 and v2 tags will be added, to ensure reading of tags by MP3 players which are unable to read ID3 v2 tags. ENCODING MODES LAME is able to encode your music using one of its 3 encoding modes: constant bitrate (CBR), average bitrate (ABR) and variable bitrate (VBR). Constant Bitrate (CBR) This is the default encoding mode, and also the most basic. In this mode, the bitrate will be the same for the whole file. It means that each part of your mp3 file will be using the same number of bits. The musical passage being a difficult one to encode or an easy one, the encoder will use the same bitrate, so the quality of your mp3 is variable. Complex parts will be of a lower quality than the easiest ones. The main advantage is that the final files size won't change and can be accurately predicted. Average Bitrate (ABR) In this mode, you choose the encoder will maintain an average bitrate while using higher bitrates for the parts of your music that need more bits. The result will be of higher quality than CBR encoding but the average file size will remain predictable, so this mode is highly recommended over CBR. This encoding mode is similar to what is referred as vbr in AAC or Liquid Audio (2 other compression technologies). Variable bitrate (VBR) In this mode, you choose the desired quality on a scale from 9 (lowest quality/biggest distortion) to 0 (highest quality/lowest distortion). Then encoder tries to maintain the given quality in the whole file by choosing the optimal number of bits to spend for each part of your music. The main advantage is that you are able to specify the quality level that you want to reach, but the inconvenient is that the final file size is totally unpredictable. PRESETS The --preset switches are aliases over LAME settings. To activate these presets: For VBR modes (generally highest quality): --preset medium This preset should provide near transparency to most people on most music. --preset standard This preset should generally be transparent to most people on most music and is already quite high in quality. --preset extreme If you have extremely good hearing and similar equipment, this preset will generally provide slightly higher quality than the standard mode. For CBR 320kbps (highest quality possible from the --preset switches): --preset insane This preset will usually be overkill for most people and most situations, but if you must have the absolute highest quality with no regard to filesize, this is the way to go. For ABR modes (high quality per given bitrate but not as high as VBR): --preset kbps Using this preset will usually give you good quality at a specified bitrate. Depending on the bitrate entered, this preset will determine the optimal settings for that particular situation. While this approach works, it is not nearly as flexible as VBR, and usually will not attain the same level of quality as VBR at higher bitrates. cbr If you use the ABR mode (read above) with a significant bitrate such as 80, 96, 112, 128, 160, 192, 224, 256, 320, you can use the --preset cbr kbps option to force CBR mode encoding instead of the standard ABR mode. ABR does provide higher quality but CBR may be useful in situations such as when streaming an MP3 over the Internet may be important.
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Fixed bit rate jstereo 128kbs encoding: lame -b 128 sample.wav sample.mp3 Fixed bit rate jstereo 128 kbps encoding, highest quality: lame -q 0 -b 128 sample.wav sample.mp3 To disable joint stereo encoding (slightly faster, but less quality at bitrates <= 128 kbps): lame -m s sample.wav sample.mp3 Variable bitrate (use -V n to adjust quality/filesize): lame -V 2 sample.wav sample.mp3 Streaming mono 22.05 kHz raw pcm, 24 kbps output: cat inputfile | lame -r -m m -b 24 -s 22.05 - - > output Streaming mono 44.1 kHz raw pcm, with downsampling to 22.05 kHz: cat inputfile | lame -r -m m -b 24 --resample 22.05 - - > output Encode with the standard preset: lame --preset standard sample.wav sample.mp3 BUGS Probably there are some. SEE ALSO mpg123(1), madplay(1), sox(1) AUTHORS LAME originally developed by Mike Cheng and now maintained by Mark Taylor, and the LAME team. GPSYCHO psycho-acoustic model by Mark Taylor. (See http://www.mp3dev.org/). mpglib by Michael Hipp Manual page by William Schelter, Nils Faerber, Alexander Leidinger, and Rogério Brito. LAME 3.99 December 8, 2013 lame(1)
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pkg-config
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The pkg-config program is used to retrieve information about installed libraries in the system. It is typically used to compile and link against one or more libraries. Here is a typical usage scenario in a Makefile: program: program.c cc program.c `pkg-config --cflags --libs gnomeui` pkg-config retrieves information about packages from special metadata files. These files are named after the package, and has a .pc extension. On most systems, pkg-config looks in /usr/lib/pkgconfig, /usr/share/pkgconfig, /usr/local/lib/pkgconfig and /usr/local/share/pkgconfig for these files. It will additionally look in the colon-separated (on Windows, semicolon-separated) list of directories specified by the PKG_CONFIG_PATH environment variable. The package name specified on the pkg-config command line is defined to be the name of the metadata file, minus the .pc extension. If a library can install multiple versions simultaneously, it must give each version its own name (for example, GTK 1.2 might have the package name "gtk+" while GTK 2.0 has "gtk+-2.0"). In addition to specifying a package name on the command line, the full path to a given .pc file may be given instead. This allows a user to directly query a particular .pc file.
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pkg-config - Return metainformation about installed libraries
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pkg-config [--modversion] [--version] [--help] [--atleast-pkgconfig- version=VERSION] [--print-errors] [--short-errors] [--silence-errors] [--errors-to-stdout] [--debug] [--cflags] [--libs] [--libs-only-L] [--libs-only-l] [--cflags-only-I] [--libs-only-other] [--cflags-only- other] [--variable=VARIABLENAME] [--define- variable=VARIABLENAME=VARIABLEVALUE] [--print-variables] [--uninstalled] [--exists] [--atleast-version=VERSION] [--exact- version=VERSION] [--max-version=VERSION] [--validate] [--list-all] [--print-provides] [--print-requires] [--print-requires-private] [LIBRARIES...]
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The following options are supported: --modversion Requests that the version information of the libraries specified on the command line be displayed. If pkg-config can find all the libraries on the command line, each library's version string is printed to stdout, one version per line. In this case pkg- config exits successfully. If one or more libraries is unknown, pkg-config exits with a nonzero code, and the contents of stdout are undefined. --version Displays the version of pkg-config and terminates. --atleast-pkgconfig-version=VERSION Requires at least the given version of pkg-config. --help Displays a help message and terminates. --print-errors If one or more of the modules on the command line, or their dependencies, are not found, or if an error occurs in parsing a .pc file, then this option will cause errors explaining the problem to be printed. With "predicate" options such as "--exists" pkg-config runs silently by default, because it's usually used in scripts that want to control what's output. This option can be used alone (to just print errors encountered locating modules on the command line) or with other options. The PKG_CONFIG_DEBUG_SPEW environment variable overrides this option. --short-errors Print short error messages. --silence-errors If one or more of the modules on the command line, or their dependencies, are not found, or if an error occurs in parsing a a .pc file, then this option will keep errors explaining the problem from being printed. With "predicate" options such as "--exists" pkg-config runs silently by default, because it's usually used in scripts that want to control what's output. So this option is only useful with options such as "--cflags" or "--modversion" that print errors by default. The PKG_CONFIG_DEBUG_SPEW environment variable overrides this option. --errors-to-stdout If printing errors, print them to stdout rather than the default stderr --debug Print debugging information. This is slightly different than the PKG_CONFIG_DEBUG_SPEW environment variable, which also enable "--print-errors". The following options are used to compile and link programs: --cflags This prints pre-processor and compile flags required to compile the packages on the command line, including flags for all their dependencies. Flags are "compressed" so that each identical flag appears only once. pkg-config exits with a nonzero code if it can't find metadata for one or more of the packages on the command line. --cflags-only-I This prints the -I part of "--cflags". That is, it defines the header search path but doesn't specify anything else. --cflags-only-other This prints parts of "--cflags" not covered by "--cflags-only- I". --libs This option is identical to "--cflags", only it prints the link flags. As with "--cflags", duplicate flags are merged (maintaining proper ordering), and flags for dependencies are included in the output. --libs-only-L This prints the -L/-R part of "--libs". That is, it defines the library search path but doesn't specify which libraries to link with. --libs-only-l This prints the -l part of "--libs" for the libraries specified on the command line. Note that the union of "--libs-only-l" and "--libs-only-L" may be smaller than "--libs", due to flags such as -rdynamic. --libs-only-other This prints the parts of "--libs" not covered by "--libs-only-L" and "--libs-only-l", such as "--pthread". --variable=VARIABLENAME This returns the value of a variable defined in a package's .pc file. Most packages define the variable "prefix", for example, so you can say: $ pkg-config --variable=prefix glib-2.0 /usr/ --define-variable=VARIABLENAME=VARIABLEVALUE This sets a global value for a variable, overriding the value in any .pc files. Most packages define the variable "prefix", for example, so you can say: $ pkg-config --print-errors --define-variable=prefix=/foo \ --variable=prefix glib-2.0 /foo --print-variables Returns a list of all variables defined in the package. --uninstalled Normally if you request the package "foo" and the package "foo- uninstalled" exists, pkg-config will prefer the "-uninstalled" variant. This allows compilation/linking against uninstalled packages. If you specify the "--uninstalled" option, pkg-config will return successfully if any "-uninstalled" packages are being used, and return failure (false) otherwise. (The PKG_CONFIG_DISABLE_UNINSTALLED environment variable keeps pkg-config from implicitly choosing "-uninstalled" packages, so if that variable is set, they will only have been used if you pass a name like "foo-uninstalled" on the command line explicitly.) --exists --atleast-version=VERSION --exact-version=VERSION --max-version=VERSION These options test whether the package or list of packages on the command line are known to pkg-config, and optionally whether the version number of a package meets certain constraints. If all packages exist and meet the specified version constraints, pkg-config exits successfully. Otherwise it exits unsuccessfully. Only the first VERSION comparing option will be honored. Subsequent options of this type will be ignored. Rather than using the version-test options, you can simply give a version constraint after each package name, for example: $ pkg-config --exists 'glib-2.0 >= 1.3.4 libxml = 1.8.3' Remember to use --print-errors if you want error messages. When no output options are supplied to pkg-config, --exists is implied. --validate Checks the syntax of a package's .pc file for validity. This is the same as --exists except that dependencies are not verified. This can be useful for package developers to test their .pc file prior to release: $ pkg-config --validate ./my-package.pc --msvc-syntax This option is available only on Windows. It causes pkg-config to output -l and -L flags in the form recognized by the Microsoft Visual C++ command-line compiler, cl. Specifically, instead of -Lx:/some/path it prints /libpath:x/some/path, and instead of -lfoo it prints foo.lib. Note that the --libs output consists of flags for the linker, and should be placed on the cl command line after a /link switch. --define-prefix --dont-define-prefix These options control whether pkg-config overrides the value of the variable prefix in each .pc file. With --define-prefix, pkg-config uses the installed location of the .pc file to determine the prefix. --dont-define-prefix prevents this behavior. The default is usually --define-prefix. When this feature is enabled and a .pc file is found in a directory named pkgconfig, the prefix for that package is assumed to be the grandparent of the directory where the file was found, and the prefix variable is overridden for that file accordingly. If the value of a variable in a .pc file begins with the original, non-overridden, value of the prefix variable, then the overridden value of prefix is used instead. This allows the feature to work even when the variables have been expanded in the .pc file. --prefix-variable=PREFIX Set the name of the variable that pkg-config overrides instead of prefix when using the --define-prefix feature. --static Output libraries suitable for static linking. That means including any private libraries in the output. This relies on proper tagging in the .pc files, else a too large number of libraries will ordinarily be output. --list-all List all modules found in the pkg-config path. --print-provides List all modules the given packages provides. --print-requires List all modules the given packages requires. --print-requires-private List all modules the given packages requires for static linking (see --static). ENVIRONMENT VARIABLES PKG_CONFIG_PATH A colon-separated (on Windows, semicolon-separated) list of directories to search for .pc files. The default directory will always be searched after searching the path; the default is libdir/pkgconfig:datadir/pkgconfig where libdir is the libdir for pkg-config and datadir is the datadir for pkg-config when it was installed. PKG_CONFIG_DEBUG_SPEW If set, causes pkg-config to print all kinds of debugging information and report all errors. PKG_CONFIG_TOP_BUILD_DIR A value to set for the magic variable pc_top_builddir which may appear in .pc files. If the environment variable is not set, the default value '$(top_builddir)' will be used. This variable should refer to the top builddir of the Makefile where the compile/link flags reported by pkg-config will be used. This only matters when compiling/linking against a package that hasn't yet been installed. PKG_CONFIG_DISABLE_UNINSTALLED Normally if you request the package "foo" and the package "foo- uninstalled" exists, pkg-config will prefer the "-uninstalled" variant. This allows compilation/linking against uninstalled packages. If this environment variable is set, it disables said behavior. PKG_CONFIG_SYSTEM_INCLUDE_PATH A path variable containing system directories searched by the compiler. This is normally /usr/include. CPATH C_INCLUDE_PATH CPLUS_INCLUDE_PATH Additional paths to append to PKG_CONFIG_SYSTEM_INCLUDE_PATH. These correspond to environment variables used by many compilers to affect the header search path. These are ignored on Windows builds when --msvc-syntax is in use. INCLUDE Additional paths to append to PKG_CONFIG_SYSTEM_INCLUDE_PATH on Windows builds when --msvc-syntax is in use. This corresponds to the environment variable used by MSVC to add directories to the include file search path. PKG_CONFIG_ALLOW_SYSTEM_CFLAGS Don't strip system paths out of Cflags. See PKG_CONFIG_SYSTEM_INCLUDE_PATH for the definition of system paths. PKG_CONFIG_SYSTEM_LIBRARY_PATH A path variable containing system directories searched by the linker. This is normally /usr/lib:/lib but is dependent on the pkg-config build and can contain other directories such as /usr/lib64. PKG_CONFIG_ALLOW_SYSTEM_LIBS Don't strip system paths out of Libs. See PKG_CONFIG_SYSTEM_LIBRARY_PATH for the definition of system paths. PKG_CONFIG_SYSROOT_DIR Modify -I and -L to use the directories located in target sysroot. this option is useful when cross-compiling packages that use pkg-config to determine CFLAGS and LDFLAGS. -I and -L are modified to point to the new system root. this means that a -I/usr/include/libfoo will become -I/var/target/usr/include/libfoo with a PKG_CONFIG_SYSROOT_DIR equal to /var/target (same rule apply to -L) PKG_CONFIG_LIBDIR Replaces the default pkg-config search directory, usually /usr/lib/pkgconfig:/usr/share/pkgconfig. PKG_CONFIG_$PACKAGE_$VARIABLE Overrides the variable VARIABLE in the package PACKAGE. The environment variable should have the package name and package variable upper cased with non-alphanumeric characters converted to underscores. For example, setting PKG_CONFIG_GLADEUI_2_0_CATALOGDIR will override the variable "catalogdir" in the "gladeui-2.0" package. PKG-CONFIG DERIVED VARIABLES pkg-config sets a few metadata variables that can be used in .pc files or queried at runtime. pc_path The default search path used by pkg-config when searching for .pc files. This can be used in a query for the pkg-config module itself itself: $ pkg-config --variable pc_path pkg-config pcfiledir The installed location of the .pc file. This can be used to query the location of the .pc file for a particular module, but it can also be used to make .pc files relocatable. For instance: prefix=${pcfiledir}/../.. exec_prefix=${prefix} libdir=${exec_prefix}/lib includedir=${prefix}/include pc_sysrootdir The sysroot directory set by the user. When the sysroot directory has not been set, this value is /. See the PKG_CONFIG_SYSROOT_DIR environment variable for more details. pc_top_builddir Location of the user's top build directory when calling pkg-config. This is useful to dynamically set paths in uninstalled .pc files. See the PKG_CONFIG_TOP_BUILD_DIR environment variable for more details. WINDOWS SPECIALITIES The pkg-config default search path is ignored on Windows. Instead, the search path is constructed by using the installed directory of pkg-config and then appending lib\pkgconfig and share\pkgconfig. This can be augmented or replaced using the standard environment variables described above. AUTOCONF MACROS PKG_CHECK_MODULES(VARIABLE-PREFIX, MODULES [,ACTION-IF-FOUND [,ACTION-IF-NOT-FOUND]]) The macro PKG_CHECK_MODULES can be used in configure.ac to check whether modules exist. A typical usage would be: PKG_CHECK_MODULES([MYSTUFF], [gtk+-2.0 >= 1.3.5 libxml = 1.8.4]) This would result in MYSTUFF_LIBS and MYSTUFF_CFLAGS substitution variables, set to the libs and cflags for the given module list. If a module is missing or has the wrong version, by default configure will abort with a message. To replace the default action, specify an ACTION-IF-NOT-FOUND. PKG_CHECK_MODULES will not print any error messages if you specify your own ACTION-IF-NOT-FOUND. However, it will set the variable MYSTUFF_PKG_ERRORS, which you can use to display what went wrong. Note that if there is a possibility the first call to PKG_CHECK_MODULES might not happen, you should be sure to include an explicit call to PKG_PROG_PKG_CONFIG in your configure.ac. Also note that repeated usage of VARIABLE-PREFIX is not recommended. After the first successful usage, subsequent calls with the same VARIABLE-PREFIX will simply use the _LIBS and _CFLAGS variables set from the previous usage without calling pkg-config again. PKG_PREREQ(MIN-VERSION) Checks that the version of the pkg-config autoconf macros in use is at least MIN-VERSION. This can be used to ensure a particular pkg-config macro will be available. PKG_PROG_PKG_CONFIG([MIN-VERSION]) Defines the PKG_CONFIG variable to the best pkg-config available, useful if you need pkg-config but don't want to use PKG_CHECK_MODULES. If the first call to PKG_PROG_PKG_CONFIG is conditional, then it will not work correctly in all cases. Since many of the other macros such as PKG_CHECK_MODULES require PKG_PROG_PKG_CONFIG to know which pkg-config program to run, PKG_PROG_PKG_CONFIG may be run for the first time from a conditional from one of these macros. Therefore, if any of the pkg-config macros will be used under a conditional, it's best to run PKG_PROG_PKG_CONFIG before any of the other macros are used. PKG_CHECK_MODULES_STATIC(VARIABLE-PREFIX, MODULES [,ACTION-IF-FOUND [,ACTION-IF-NOT-FOUND]]) Enables static linking through --static prior to calling PKG_CHECK_MODULES. PKG_CHECK_EXISTS(MODULES, [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND]) Check to see whether a particular set of modules exists. Similar to PKG_CHECK_MODULES(), but does not set variables or print errors. Similar to PKG_CHECK_MODULES, make sure that the first instance of this or PKG_CHECK_MODULES is called, or make sure to call PKG_PROG_PKGCONFIG manually. PKG_INSTALLDIR(DIRECTORY) Substitutes the variable pkgconfigdir as the location where a module should install pkg-config .pc files. By default the directory is $libdir/pkgconfig, but the default can be changed by passing DIRECTORY. The user can override through the --with- pkgconfigdir parameter. PKG_NOARCH_INSTALLDIR(DIRECTORY) Substitutes the variable noarch_pkgconfigdir as the location where a module should install arch-independent pkg-config .pc files. By default the directory is $datadir/pkgconfig, but the default can be changed by passing DIRECTORY. The user can override through the --with-noarch-pkgconfigdir parameter. PKG_CHECK_VAR(VARIABLE, MODULE, CONFIG-VARIABLE, [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND]) Retrieves the value of the pkg-config variable CONFIG-VARIABLE from MODULE and stores it in VARIABLE. Note that repeated usage of VARIABLE is not recommended as the check will be skipped if the variable is already set. METADATA FILE SYNTAX To add a library to the set of packages pkg-config knows about, simply install a .pc file. You should install this file to libdir/pkgconfig. Here is an example file: # This is a comment prefix=/home/hp/unst # this defines a variable exec_prefix=${prefix} # defining another variable in terms of the first libdir=${exec_prefix}/lib includedir=${prefix}/include Name: GObject # human-readable name Description: Object/type system for GLib # human-readable description Version: 1.3.1 URL: http://www.gtk.org Requires: glib-2.0 = 1.3.1 Conflicts: foobar <= 4.5 Libs: -L${libdir} -lgobject-1.3 Libs.private: -lm Cflags: -I${includedir}/glib-2.0 -I${libdir}/glib/include You would normally generate the file using configure, so that the prefix, etc. are set to the proper values. The GNU Autoconf manual recommends generating files like .pc files at build time rather than configure time, so when you build the .pc file is a matter of taste and preference. Files have two kinds of line: keyword lines start with a keyword plus a colon, and variable definitions start with an alphanumeric string plus an equals sign. Keywords are defined in advance and have special meaning to pkg-config; variables do not, you can have any variables that you wish (however, users may expect to retrieve the usual directory name variables). Note that variable references are written "${foo}"; you can escape literal "${" as "$${". Name: This field should be a human-readable name for the package. Note that it is not the name passed as an argument to pkg-config. Description: This should be a brief description of the package URL: An URL where people can get more information about and download the package Version: This should be the most-specific-possible package version string. Requires: This is a comma-separated list of packages that are required by your package. Flags from dependent packages will be merged in to the flags reported for your package. Optionally, you can specify the version of the required package (using the operators =, <, >, >=, <=); specifying a version allows pkg-config to perform extra sanity checks. You may only mention the same package one time on the Requires: line. If the version of a package is unspecified, any version will be used with no checking. Requires.private: A list of packages required by this package. The difference from Requires is that the packages listed under Requires.private are not taken into account when a flag list is computed for dynamically linked executable (i.e., when --static was not specified). In the situation where each .pc file corresponds to a library, Requires.private shall be used exclusively to specify the dependencies between the libraries. Conflicts: This optional line allows pkg-config to perform additional sanity checks, primarily to detect broken user installations. The syntax is the same as Requires: except that you can list the same package more than once here, for example "foobar = 1.2.3, foobar = 1.2.5, foobar >= 1.3", if you have reason to do so. If a version isn't specified, then your package conflicts with all versions of the mentioned package. If a user tries to use your package and a conflicting package at the same time, then pkg- config will complain. Libs: This line should give the link flags specific to your package. Don't add any flags for required packages; pkg-config will add those automatically. Libs.private: This line should list any private libraries in use. Private libraries are libraries which are not exposed through your library, but are needed in the case of static linking. This differs from Requires.private in that it references libraries that do not have package files installed. Cflags: This line should list the compile flags specific to your package. Don't add any flags for required packages; pkg-config will add those automatically. AUTHOR pkg-config was written by James Henstridge, rewritten by Martijn van Beers, and rewritten again by Havoc Pennington. Tim Janik, Owen Taylor, and Raja Harinath submitted suggestions and some code. gnome-config was written by Miguel de Icaza, Raja Harinath and various hackers in the GNOME team. It was inspired by Owen Taylor's gtk-config program. BUGS pkg-config does not handle mixing of parameters with and without = well. Stick with one. Bugs can be reported at http://bugs.freedesktop.org/ under the pkg-config component. pkg-config(1)
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lstmtraining
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bdftogd
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hwloc-compress-dir
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hwloc-compress-dir takes an input directory containing XML exports and tries to compress it by computing topology diffs between them (with the hwloc-diff program). Each file is copied in the output directory either as a diff if it could be compressed, or as its original entire file otherwise. hwloc-compress-dir may recompress a directory that was previously compressed. All input files that are already in the output directory, either compressed or not, are ignored. New input files are compressed as much as possible as usual. For each file of the directory, the output filename is the same as the original if not compressed, otherwise its extension is changed to .diff.xml. Compressed files are based on another non-compressed topology. Its name is stored in the refname topology diff attribute. The generated output diff files may be used with hwloc-patch just like any file generated by hwloc-diff.
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hwloc-compress-dir - Compress a directory of XML topologies
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hwloc-compress-dir [options] <inputdir> <outputdir>
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-R --reverse Uncompress a previously compressed directory. -v --verbose Display verbose messages. --version Report version and exit. -h --help Display help message and exit.
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To compress the input files from directory in into directory out: $ hwloc-compress-dir in out RETURN VALUE Upon successful execution, hwloc-compress-dir returns 0. hwloc-compress-dir will return nonzero if any kind of error occurs, such as (but not limited to) failure to parse the command line. SEE ALSO hwloc(7), lstopo(1), hwloc-diff(1), hwloc-patch(1) 2.10.0 December 4, 2023 HWLOC-COMPRESS-DIR(1)
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ruff
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grpc_node_plugin
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estimator_ckpt_converter
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mbedtls-selftest
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vim
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Vim is a text editor that is upwards compatible to Vi. It can be used to edit all kinds of plain text. It is especially useful for editing programs. There are a lot of enhancements above Vi: multi level undo, multi windows and buffers, syntax highlighting, command line editing, filename completion, on-line help, visual selection, etc.. See ":help vi_diff.txt" for a summary of the differences between Vim and Vi. While running Vim a lot of help can be obtained from the on-line help system, with the ":help" command. See the ON-LINE HELP section below. Most often Vim is started to edit a single file with the command vim file More generally Vim is started with: vim [options] [filelist] If the filelist is missing, the editor will start with an empty buffer. Otherwise exactly one out of the following four may be used to choose one or more files to be edited. file .. A list of filenames. The first one will be the current file and read into the buffer. The cursor will be positioned on the first line of the buffer. You can get to the other files with the ":next" command. To edit a file that starts with a dash, precede the filelist with "--". - The file to edit is read from stdin. Commands are read from stderr, which should be a tty. -t {tag} The file to edit and the initial cursor position depends on a "tag", a sort of goto label. {tag} is looked up in the tags file, the associated file becomes the current file and the associated command is executed. Mostly this is used for C programs, in which case {tag} could be a function name. The effect is that the file containing that function becomes the current file and the cursor is positioned on the start of the function. See ":help tag-commands". -q [errorfile] Start in quickFix mode. The file [errorfile] is read and the first error is displayed. If [errorfile] is omitted, the filename is obtained from the 'errorfile' option (defaults to "AztecC.Err" for the Amiga, "errors.err" on other systems). Further errors can be jumped to with the ":cn" command. See ":help quickfix". Vim behaves differently, depending on the name of the command (the executable may still be the same file). vim The "normal" way, everything is default. ex Start in Ex mode. Go to Normal mode with the ":vi" command. Can also be done with the "-e" argument. view Start in read-only mode. You will be protected from writing the files. Can also be done with the "-R" argument. gvim gview The GUI version. Starts a new window. Can also be done with the "-g" argument. evim eview The GUI version in easy mode. Starts a new window. Can also be done with the "-y" argument. rvim rview rgvim rgview Like the above, but with restrictions. It will not be possible to start shell commands, or suspend Vim. Can also be done with the "-Z" argument.
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vim - Vi IMproved, a programmer's text editor
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vim [options] [file ..] vim [options] - vim [options] -t tag vim [options] -q [errorfile] ex view gvim gview evim eview rvim rview rgvim rgview
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The options may be given in any order, before or after filenames. Options without an argument can be combined after a single dash. +[num] For the first file the cursor will be positioned on line "num". If "num" is missing, the cursor will be positioned on the last line. +/{pat} For the first file the cursor will be positioned in the line with the first occurrence of {pat}. See ":help search-pattern" for the available search patterns. +{command} -c {command} {command} will be executed after the first file has been read. {command} is interpreted as an Ex command. If the {command} contains spaces it must be enclosed in double quotes (this depends on the shell that is used). Example: vim "+set si" main.c Note: You can use up to 10 "+" or "-c" commands. -S {file} {file} will be sourced after the first file has been read. This is equivalent to -c "source {file}". {file} cannot start with '-'. If {file} is omitted "Session.vim" is used (only works when -S is the last argument). --cmd {command} Like using "-c", but the command is executed just before processing any vimrc file. You can use up to 10 of these commands, independently from "-c" commands. -A If Vim has been compiled with ARABIC support for editing right-to-left oriented files and Arabic keyboard mapping, this option starts Vim in Arabic mode, i.e. 'arabic' is set. Otherwise an error message is given and Vim aborts. -b Binary mode. A few options will be set that makes it possible to edit a binary or executable file. -C Compatible. Set the 'compatible' option. This will make Vim behave mostly like Vi, even though a .vimrc file exists. -d Start in diff mode. There should between two to eight file name arguments. Vim will open all the files and show differences between them. Works like vimdiff(1). -d {device}, -dev {device} Open {device} for use as a terminal. Only on the Amiga. Example: "-d con:20/30/600/150". -D Debugging. Go to debugging mode when executing the first command from a script. -e Start Vim in Ex mode, just like the executable was called "ex". -E Start Vim in improved Ex mode, just like the executable was called "exim". -f Foreground. For the GUI version, Vim will not fork and detach from the shell it was started in. On the Amiga, Vim is not restarted to open a new window. This option should be used when Vim is executed by a program that will wait for the edit session to finish (e.g. mail). On the Amiga the ":sh" and ":!" commands will not work. --nofork Foreground. For the GUI version, Vim will not fork and detach from the shell it was started in. -F If Vim has been compiled with FKMAP support for editing right-to-left oriented files and Farsi keyboard mapping, this option starts Vim in Farsi mode, i.e. 'fkmap' and 'rightleft' are set. Otherwise an error message is given and Vim aborts. -g If Vim has been compiled with GUI support, this option enables the GUI. If no GUI support was compiled in, an error message is given and Vim aborts. --gui-dialog-file {name} When using the GUI, instead of showing a dialog, write the title and message of the dialog to file {name}. The file is created or appended to. Only useful for testing, to avoid that the test gets stuck on a dialog that can't be seen. Without the GUI the argument is ignored. --help, -h, -? Give a bit of help about the command line arguments and options. After this Vim exits. -H If Vim has been compiled with RIGHTLEFT support for editing right-to-left oriented files and Hebrew keyboard mapping, this option starts Vim in Hebrew mode, i.e. 'hkmap' and 'rightleft' are set. Otherwise an error message is given and Vim aborts. -i {viminfo} Specifies the filename to use when reading or writing the viminfo file, instead of the default "~/.viminfo". This can also be used to skip the use of the .viminfo file, by giving the name "NONE". -L Same as -r. -l Lisp mode. Sets the 'lisp' and 'showmatch' options on. -m Modifying files is disabled. Resets the 'write' option. You can still modify the buffer, but writing a file is not possible. -M Modifications not allowed. The 'modifiable' and 'write' options will be unset, so that changes are not allowed and files can not be written. Note that these options can be set to enable making modifications. -N No-compatible mode. Resets the 'compatible' option. This will make Vim behave a bit better, but less Vi compatible, even though a .vimrc file does not exist. -n No swap file will be used. Recovery after a crash will be impossible. Handy if you want to edit a file on a very slow medium (e.g. floppy). Can also be done with ":set uc=0". Can be undone with ":set uc=200". -nb Become an editor server for NetBeans. See the docs for details. -o[N] Open N windows stacked. When N is omitted, open one window for each file. -O[N] Open N windows side by side. When N is omitted, open one window for each file. -p[N] Open N tab pages. When N is omitted, open one tab page for each file. -P {parent-title} Win32 GUI only: Specify the title of the parent application. When possible, Vim will run in an MDI window inside the application. {parent-title} must appear in the window title of the parent application. Make sure that it is specific enough. Note that the implementation is still primitive. It won't work with all applications and the menu doesn't work. -R Read-only mode. The 'readonly' option will be set. You can still edit the buffer, but will be prevented from accidentally overwriting a file. If you do want to overwrite a file, add an exclamation mark to the Ex command, as in ":w!". The -R option also implies the -n option (see above). The 'readonly' option can be reset with ":set noro". See ":help 'readonly'". -r List swap files, with information about using them for recovery. -r {file} Recovery mode. The swap file is used to recover a crashed editing session. The swap file is a file with the same filename as the text file with ".swp" appended. See ":help recovery". -s Silent mode. Only when started as "Ex" or when the "-e" option was given before the "-s" option. -s {scriptin} The script file {scriptin} is read. The characters in the file are interpreted as if you had typed them. The same can be done with the command ":source! {scriptin}". If the end of the file is reached before the editor exits, further characters are read from the keyboard. -T {terminal} Tells Vim the name of the terminal you are using. Only required when the automatic way doesn't work. Should be a terminal known to Vim (builtin) or defined in the termcap or terminfo file. --not-a-term Tells Vim that the user knows that the input and/or output is not connected to a terminal. This will avoid the warning and the two second delay that would happen. --ttyfail When stdin or stdout is not a a terminal (tty) then exit right away. -u {vimrc} Use the commands in the file {vimrc} for initializations. All the other initializations are skipped. Use this to edit a special kind of files. It can also be used to skip all initializations by giving the name "NONE". See ":help initialization" within vim for more details. -U {gvimrc} Use the commands in the file {gvimrc} for GUI initializations. All the other GUI initializations are skipped. It can also be used to skip all GUI initializations by giving the name "NONE". See ":help gui-init" within vim for more details. -V[N] Verbose. Give messages about which files are sourced and for reading and writing a viminfo file. The optional number N is the value for 'verbose'. Default is 10. -V[N]{filename} Like -V and set 'verbosefile' to {filename}. The result is that messages are not displayed but written to the file {filename}. {filename} must not start with a digit. --log {filename} If Vim has been compiled with eval and channel feature, start logging and write entries to {filename}. This works like calling ch_logfile({filename}, 'ao') very early during startup. -v Start Vim in Vi mode, just like the executable was called "vi". This only has effect when the executable is called "ex". -w{number} Set the 'window' option to {number}. -w {scriptout} All the characters that you type are recorded in the file {scriptout}, until you exit Vim. This is useful if you want to create a script file to be used with "vim -s" or ":source!". If the {scriptout} file exists, characters are appended. -W {scriptout} Like -w, but an existing file is overwritten. -x Use encryption when writing files. Will prompt for a crypt key. -X Don't connect to the X server. Shortens startup time in a terminal, but the window title and clipboard will not be used. -y Start Vim in easy mode, just like the executable was called "evim" or "eview". Makes Vim behave like a click-and-type editor. -Z Restricted mode. Works like the executable starts with "r". -- Denotes the end of the options. Arguments after this will be handled as a file name. This can be used to edit a filename that starts with a '-'. --clean Do not use any personal configuration (vimrc, plugins, etc.). Useful to see if a problem reproduces with a clean Vim setup. --echo-wid GTK GUI only: Echo the Window ID on stdout. --literal Take file name arguments literally, do not expand wildcards. This has no effect on Unix where the shell expands wildcards. --noplugin Skip loading plugins. Implied by -u NONE. --remote Connect to a Vim server and make it edit the files given in the rest of the arguments. If no server is found a warning is given and the files are edited in the current Vim. --remote-expr {expr} Connect to a Vim server, evaluate {expr} in it and print the result on stdout. --remote-send {keys} Connect to a Vim server and send {keys} to it. --remote-silent As --remote, but without the warning when no server is found. --remote-wait As --remote, but Vim does not exit until the files have been edited. --remote-wait-silent As --remote-wait, but without the warning when no server is found. --serverlist List the names of all Vim servers that can be found. --servername {name} Use {name} as the server name. Used for the current Vim, unless used with a --remote argument, then it's the name of the server to connect to. --socketid {id} GTK GUI only: Use the GtkPlug mechanism to run gvim in another window. --startuptime {file} During startup write timing messages to the file {fname}. --version Print version information and exit. --windowid {id} Win32 GUI only: Make gvim try to use the window {id} as a parent, so that it runs inside that window. ON-LINE HELP Type ":help" in Vim to get started. Type ":help subject" to get help on a specific subject. For example: ":help ZZ" to get help for the "ZZ" command. Use <Tab> and CTRL-D to complete subjects (":help cmdline-completion"). Tags are present to jump from one place to another (sort of hypertext links, see ":help"). All documentation files can be viewed in this way, for example ":help syntax.txt". FILES /usr/local/share/vim/vim??/doc/*.txt The Vim documentation files. Use ":help doc-file-list" to get the complete list. vim?? is short version number, like vim91 for Vim 9.1 /usr/local/share/vim/vim??/doc/tags The tags file used for finding information in the documentation files. /usr/local/share/vim/vim??/syntax/syntax.vim System wide syntax initializations. /usr/local/share/vim/vim??/syntax/*.vim Syntax files for various languages. /usr/local/share/vim/vimrc System wide Vim initializations. ~/.vimrc, ~/.vim/vimrc, $XDG_CONFIG_HOME/vim/vimrc Your personal Vim initializations (first one found is used). /usr/local/share/vim/gvimrc System wide gvim initializations. ~/.gvimrc, ~/.vim/gvimrc, $XDG_CONFIG_HOME/vim/gvimrc Your personal gvim initializations (first one found is used). /usr/local/share/vim/vim??/optwin.vim Script used for the ":options" command, a nice way to view and set options. /usr/local/share/vim/vim??/menu.vim System wide menu initializations for gvim. /usr/local/share/vim/vim??/bugreport.vim Script to generate a bug report. See ":help bugs". /usr/local/share/vim/vim??/filetype.vim Script to detect the type of a file by its name. See ":help 'filetype'". /usr/local/share/vim/vim??/scripts.vim Script to detect the type of a file by its contents. See ":help 'filetype'". /usr/local/share/vim/vim??/print/*.ps Files used for PostScript printing. For recent info read the VIM home page: <URL:http://www.vim.org/> SEE ALSO vimtutor(1) AUTHOR Most of Vim was made by Bram Moolenaar, with a lot of help from others. See ":help credits" in Vim. Vim is based on Stevie, worked on by: Tim Thompson, Tony Andrews and G.R. (Fred) Walter. Although hardly any of the original code remains. BUGS Probably. See ":help todo" for a list of known problems. Note that a number of things that may be regarded as bugs by some, are in fact caused by a too-faithful reproduction of Vi's behaviour. And if you think other things are bugs "because Vi does it differently", you should take a closer look at the vi_diff.txt file (or type :help vi_diff.txt when in Vim). Also have a look at the 'compatible' and 'cpoptions' options. 2024 Jun 04 VIM(1)
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gprintenv
|
Print the values of the specified environment VARIABLE(s). If no VARIABLE is specified, print name and value pairs for them all. -0, --null end each output line with NUL, not newline --help display this help and exit --version output version information and exit NOTE: your shell may have its own version of printenv, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports. AUTHOR Written by David MacKenzie and Richard Mlynarik. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO Full documentation <https://www.gnu.org/software/coreutils/printenv> or available locally via: info '(coreutils) printenv invocation' GNU coreutils 9.3 April 2023 PRINTENV(1)
|
printenv - print all or part of environment
|
printenv [OPTION]... [VARIABLE]...
| null | null |
merge_unicharsets
| null | null | null | null | null |
gif2rgb
| null |
gif2rgb - convert images saved as GIF to 24-bit RGB triplets
|
gif2rgb [-v] [-1] [-c colors] [-s width height] [-o outfile] [-h] [gif-file]
|
-v Verbose mode (show progress). Enables printout of running scan lines. -1 Only one file in the format of RGBRGB... triplets (Each of R, G,B is a byte) is being read or written. This file size is 3 * Width * Height. If stdin is used for input or stdout for output, this option is implicitly applied. The default (if not `-1') is 3 files with the names OutFileName.R, OutFileName.G, OutFileName.B, each of which is Width * Height bytes. -c colors Specifies number of colors to use in RGB-to-GIF conversions, in bits per pixels, so '-c 8' actually specifies 256 colors (maximum and default). -s width height Sets RGB-to-GIF conversion mode and specifies the size of the image to read. -o specifies the name of the out file (see also `-1' above). -h Print one line of command line help, similar to Usage above. By default, convert a GIF input file to RGB triplets. If -s is specified, convert RGB input to a GIF. If no input file is given, gif2rgb will try to read data from stdin. AUTHOR Gershon Elber. GIFLIB 2 May 2012 GIF2RGB(1)
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general_assembly.pl
| null | null | null | null | null |
gmknod
|
Create the special file NAME of the given TYPE. Mandatory arguments to long options are mandatory for short options too. -m, --mode=MODE set file permission bits to MODE, not a=rw - umask -Z set the SELinux security context to default type --context[=CTX] like -Z, or if CTX is specified then set the SELinux or SMACK security context to CTX --help display this help and exit --version output version information and exit Both MAJOR and MINOR must be specified when TYPE is b, c, or u, and they must be omitted when TYPE is p. If MAJOR or MINOR begins with 0x or 0X, it is interpreted as hexadecimal; otherwise, if it begins with 0, as octal; otherwise, as decimal. TYPE may be: b create a block (buffered) special file c, u create a character (unbuffered) special file p create a FIFO NOTE: your shell may have its own version of mknod, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports. AUTHOR Written by David MacKenzie. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO mknod(2) Full documentation <https://www.gnu.org/software/coreutils/mknod> or available locally via: info '(coreutils) mknod invocation' GNU coreutils 9.3 April 2023 MKNOD(1)
|
mknod - make block or character special files
|
mknod [OPTION]... NAME TYPE [MAJOR MINOR]
| null | null |
niceload
|
GNU niceload will slow down a program when the load average (or other system activity) is above a certain limit. When the limit is reached the program will be suspended for some time. Then resumed again for some time. Then the load average is checked again and we start over. Instead of load average niceload can also look at disk I/O, amount of free memory, or swapping activity. If the load is 3.00 then the default settings will run a program like this: run 1 second, suspend (3.00-1.00) seconds, run 1 second, suspend (3.00-1.00) seconds, run 1 second, ...
|
niceload - slow down a program when the load average is above a certain limit
|
niceload [-v] [-h] [-n nice] [-I io] [-L load] [-M mem] [-N] [--sensor program] [-t time] [-s time|-f factor] ( command | -p PID [-p PID ...] | --prg program )
|
-B --battery Suspend if the system is running on battery. Shorthand for: -l -1 --sensor 'cat /sys/class/power_supply/BAT0/status /proc/acpi/battery/BAT0/state 2>/dev/null | grep -i -q discharging; echo $?' -f FACTOR --factor FACTOR Suspend time factor. Dynamically set -s as amount over limit * factor. Default is 1. -H --hard Hard limit. --hard will suspend the process until the system is under the limits. The default is --soft. --io iolimit -I iolimit Limit for I/O. The amount of disk I/O will be computed as a value 0 - 10, where 0 is no I/O and 10 is at least one disk is 100% saturated. --io will set both --start-io and --run-io. --load loadlimit -L loadlimit Limit for load average. --load will set both --start-load and --run-load. --mem memlimit -M memlimit Limit for free memory. This is the amount of bytes available as free + cache. This limit is treated opposite other limits: If the system is above the limit the program will run, if it is below the limit the program will stop memlimit can be postfixed with K, M, G, T, or P which would multiply the size with 1024, 1048576, 1073741824, or 1099511627776 respectively. --mem will set both --start-mem and --run-mem. --noswap -N No swapping. If the system is swapping both in and out it is a good indication that the system is memory stressed. --noswap is over limit if the system is swapping both in and out. --noswap will set both --start-noswap and --run-noswap. --net Shorthand for --nethops 3. --nethops h Network nice. Pause if the internet connection is overloaded. niceload finds a router h hops closer to the internet. It pings this every second. If the latency is more than 50% bigger than the median, it is regarded as being over the limit. --nethops can be combined with --hard. Without --hard the program may be able to queue up so much traffic that it will take longer than the --suspend time to clear it. --hard is useful for traffic that does not break by being suspended for a longer time. --nethops can be combined with a high --suspend. This way a program can be allowed to do a bit of traffic now and then. This is useful to keep the connection alive. -n niceness --nice niceness Sets niceness. See nice(1). -p PID[,PID] --pid PID[,PID] Process IDs of processes to suspend. You can specify multiple process IDs with multiple -p PID or by separating the PIDs with comma. --prg program --program program Name of running program to suspend. You can specify multiple programs with multiple --prg program. If no processes with the name program is found, niceload with search for substrings containing program. --quote -q Quote the command line. Useful if the command contains chars like *, $, >, and " that should not be interpreted by the shell. --run-io iolimit --ri iolimit --run-load loadlimit --rl loadlimit --run-mem memlimit --rm memlimit Run limit. The running program will be slowed down if the system is above the limit. See: --io, --load, --mem, --noswap. --sensor sensor program Read sensor. Use sensor program to read a sensor. This will keep the CPU temperature below 80 deg C on GNU/Linux: niceload -l 80000 -f 0.001 --sensor 'sort -n /sys/devices/platform/coretemp*/temp*_input' gzip * This will stop if the disk space < 100000. niceload -H -l -100000 --sensor "df . | awk '{ print \$4 }'" echo --start-io iolimit --si iolimit --start-load loadlimit --sl loadlimit --start-mem memlimit --sm memlimit Start limit. The program will not start until the system is below the limit. See: --io, --load, --mem, --noswap. --soft -S Soft limit. niceload will suspend a process for a while and then let it run for a second thus only slowing down a process while the system is over one of the given limits. This is the default. --suspend SEC -s SEC Suspend time. Suspend the command this many seconds when the max load average is reached. --recheck SEC -t SEC Recheck load time. Sleep SEC seconds before checking load again. Default is 1 second. --verbose -v Verbose. Print some extra output on what is happening. Use -v until you know what your are doing. EXAMPLE: See niceload in action In terminal 1 run: top In terminal 2 run: niceload -q perl -e '$|=1;do{$l==$r or print "."; $l=$r}until(($r=time-$^T)>50)' This will print a '.' every second for 50 seconds and eat a lot of CPU. When the load rises to 1.0 the process is suspended. EXAMPLE: Run updatedb Running updatedb can often starve the system for disk I/O and thus result in a high load. Run updatedb but suspend updatedb if the load is above 2.00: niceload -L 2 updatedb EXAMPLE: Run rsync rsync can, just like updatedb, starve the system for disk I/O and thus result in a high load. Run rsync but keep load below 3.4. If load reaches 7 sleep for (7-3.4)*12 seconds: niceload -L 3.4 -f 12 rsync -Ha /home/ /backup/home/ EXAMPLE: Ensure enough disk cache Assume the program foo uses 2 GB files intensively. foo will run fast if the files are in disk cache and be slow as a crawl if they are not in the cache. To ensure 2 GB are reserved for disk cache run: niceload --hard --run-mem 2g foo This will not guarantee that the 2 GB memory will be used for the files for foo, but it will stop foo if the memory for disk cache is too low. ENVIRONMENT VARIABLES None. In future versions $NICELOAD will be able to contain default settings. EXIT STATUS Exit status should be the same as the command being run (untested). REPORTING BUGS Report bugs to <bug-parallel@gnu.org>. AUTHOR Copyright (C) 2004-11-19 Ole Tange, http://ole.tange.dk Copyright (C) 2005-2010 Ole Tange, http://ole.tange.dk Copyright (C) 2010-2024 Ole Tange, http://ole.tange.dk and Free Software Foundation, Inc. LICENSE This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or at your option any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. Documentation license I Permission is granted to copy, distribute and/or modify this documentation under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the file LICENSES/GFDL-1.3-or-later.txt. Documentation license II You are free: to Share to copy, distribute and transmit the work to Remix to adapt the work Under the following conditions: Attribution You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work). Share Alike If you alter, transform, or build upon this work, you may distribute the resulting work only under the same, similar or a compatible license. With the understanding that: Waiver Any of the above conditions can be waived if you get permission from the copyright holder. Public Domain Where the work or any of its elements is in the public domain under applicable law, that status is in no way affected by the license. Other Rights In no way are any of the following rights affected by the license: • Your fair dealing or fair use rights, or other applicable copyright exceptions and limitations; • The author's moral rights; • Rights other persons may have either in the work itself or in how the work is used, such as publicity or privacy rights. Notice For any reuse or distribution, you must make clear to others the license terms of this work. A copy of the full license is included in the file as LICENCES/CC-BY-SA-4.0.txt DEPENDENCIES GNU niceload uses Perl, and the Perl modules POSIX, and Getopt::Long. SEE ALSO parallel(1), nice(1), uptime(1) 20240522 2024-06-22 NICELOAD(1)
| null |
pktdumper
| null | null | null | null | null |
djxl
|
djxl decompresses a JPEG XL image or animation. The output format is determined by the extension of the output file, which can be .png, .jpg, .ppm, .pfm. If the JPEG XL input file contains an animation, multiple output files will be produced, with names of the form "output-framenumber.ext".
|
djxl - decompress JPEG XL images
|
djxl [options...] input.jxl [output]
|
-h, --help Displays the options that djxl supports. -j, --pixels_to_jpeg By default, if the input JPEG XL contains a recompressed JPEG file, djxl reconstructs the exact original JPEG file if the output file has the .jpg (or .jpeg) filename extension. This flag causes the decoder to instead decode the image to pixels and encode a new (lossy) JPEG in this case. -q quality, --jpeg_quality=quality When decoding to .jpg, use this output quality. This option implicitly enables the --pixels_to_jpeg option.
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# Decompress a JPEG XL file to PNG $ djxl input.jxl output.png # Reconstruct a losslessly-recompressed JPEG file $ djxl lossless-jpeg.jxl reconstructed.jpeg SEE ALSO cjxl(1) 06/27/2024 DJXL(1)
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msggrep
|
Extracts all messages of a translation catalog that match a given pattern or belong to some given source files. Mandatory arguments to long options are mandatory for short options too. Input file location: INPUTFILE input PO file -D, --directory=DIRECTORY add DIRECTORY to list for input files search If no input file is given or if it is -, standard input is read. Output file location: -o, --output-file=FILE write output to specified file The results are written to standard output if no output file is specified or if it is -. Message selection: [-N SOURCEFILE]... [-M DOMAINNAME]... [-J MSGCTXT-PATTERN] [-K MSGID-PATTERN] [-T MSGSTR-PATTERN] [-C COMMENT-PATTERN] [-X EXTRACTED-COMMENT-PATTERN] A message is selected if it comes from one of the specified source files, or if it comes from one of the specified domains, or if -J is given and its context (msgctxt) matches MSGCTXT-PATTERN, or if -K is given and its key (msgid or msgid_plural) matches MSGID-PATTERN, or if -T is given and its translation (msgstr) matches MSGSTR-PATTERN, or if -C is given and the translator's comment matches COMMENT-PATTERN, or if -X is given and the extracted comment matches EXTRACTED-COMMENT-PATTERN. When more than one selection criterion is specified, the set of selected messages is the union of the selected messages of each criterion. MSGCTXT-PATTERN or MSGID-PATTERN or MSGSTR-PATTERN or COMMENT-PATTERN or EXTRACTED-COMMENT-PATTERN syntax: [-E | -F] [-e PATTERN | -f FILE]... PATTERNs are basic regular expressions by default, or extended regular expressions if -E is given, or fixed strings if -F is given. -N, --location=SOURCEFILE select messages extracted from SOURCEFILE -M, --domain=DOMAINNAME select messages belonging to domain DOMAINNAME -J, --msgctxt start of patterns for the msgctxt -K, --msgid start of patterns for the msgid -T, --msgstr start of patterns for the msgstr -C, --comment start of patterns for the translator's comment -X, --extracted-comment start of patterns for the extracted comment -E, --extended-regexp PATTERN is an extended regular expression -F, --fixed-strings PATTERN is a set of newline-separated strings -e, --regexp=PATTERN use PATTERN as a regular expression -f, --file=FILE obtain PATTERN from FILE -i, --ignore-case ignore case distinctions -v, --invert-match output only the messages that do not match any selection criterion Input file syntax: -P, --properties-input input file is in Java .properties syntax --stringtable-input input file is in NeXTstep/GNUstep .strings syntax Output details: --color use colors and other text attributes always --color=WHEN use colors and other text attributes if WHEN. WHEN may be 'always', 'never', 'auto', or 'html'. --style=STYLEFILE specify CSS style rule file for --color --no-escape do not use C escapes in output (default) --escape use C escapes in output, no extended chars --force-po write PO file even if empty --indent indented output style --no-location suppress '#: filename:line' lines -n, --add-location preserve '#: filename:line' lines (default) --strict strict Uniforum output style -p, --properties-output write out a Java .properties file --stringtable-output write out a NeXTstep/GNUstep .strings file -w, --width=NUMBER set output page width --no-wrap do not break long message lines, longer than the output page width, into several lines --sort-output generate sorted output --sort-by-file sort output by file location Informative output: -h, --help display this help and exit -V, --version output version information and exit AUTHOR Written by Bruno Haible. REPORTING BUGS Report bugs in the bug tracker at <https://savannah.gnu.org/projects/gettext> or by email to <bug-gettext@gnu.org>. COPYRIGHT Copyright © 2001-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO The full documentation for msggrep is maintained as a Texinfo manual. If the info and msggrep programs are properly installed at your site, the command info msggrep should give you access to the complete manual. GNU gettext-tools 0.22.5 February 2024 MSGGREP(1)
|
msggrep - pattern matching on message catalog
|
msggrep [OPTION] [INPUTFILE]
| null | null |
srt-file-transmit
| null | null | null | null | null |
import_pb_to_tensorboard
| null | null | null | null | null |
idle3.11
| null | null | null | null | null |
shuf
|
Write a random permutation of the input lines to standard output. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. -e, --echo treat each ARG as an input line -i, --input-range=LO-HI treat each number LO through HI as an input line -n, --head-count=COUNT output at most COUNT lines -o, --output=FILE write result to FILE instead of standard output --random-source=FILE get random bytes from FILE -r, --repeat output lines can be repeated -z, --zero-terminated line delimiter is NUL, not newline --help display this help and exit --version output version information and exit AUTHOR Written by Paul Eggert. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO Full documentation <https://www.gnu.org/software/coreutils/shuf> or available locally via: info '(coreutils) shuf invocation' GNU coreutils 9.3 April 2023 SHUF(1)
|
shuf - generate random permutations
|
shuf [OPTION]... [FILE] shuf -e [OPTION]... [ARG]... shuf -i LO-HI [OPTION]...
| null | null |
gdd
|
Copy a file, converting and formatting according to the operands. bs=BYTES read and write up to BYTES bytes at a time (default: 512); overrides ibs and obs cbs=BYTES convert BYTES bytes at a time conv=CONVS convert the file as per the comma separated symbol list count=N copy only N input blocks ibs=BYTES read up to BYTES bytes at a time (default: 512) if=FILE read from FILE instead of stdin iflag=FLAGS read as per the comma separated symbol list obs=BYTES write BYTES bytes at a time (default: 512) of=FILE write to FILE instead of stdout oflag=FLAGS write as per the comma separated symbol list seek=N (or oseek=N) skip N obs-sized output blocks skip=N (or iseek=N) skip N ibs-sized input blocks status=LEVEL The LEVEL of information to print to stderr; 'none' suppresses everything but error messages, 'noxfer' suppresses the final transfer statistics, 'progress' shows periodic transfer statistics N and BYTES may be followed by the following multiplicative suffixes: c=1, w=2, b=512, kB=1000, K=1024, MB=1000*1000, M=1024*1024, xM=M, GB=1000*1000*1000, G=1024*1024*1024, and so on for T, P, E, Z, Y, R, Q. Binary prefixes can be used, too: KiB=K, MiB=M, and so on. If N ends in 'B', it counts bytes not blocks. Each CONV symbol may be: ascii from EBCDIC to ASCII ebcdic from ASCII to EBCDIC ibm from ASCII to alternate EBCDIC block pad newline-terminated records with spaces to cbs-size unblock replace trailing spaces in cbs-size records with newline lcase change upper case to lower case ucase change lower case to upper case sparse try to seek rather than write all-NUL output blocks swab swap every pair of input bytes sync pad every input block with NULs to ibs-size; when used with block or unblock, pad with spaces rather than NULs excl fail if the output file already exists nocreat do not create the output file notrunc do not truncate the output file noerror continue after read errors fdatasync physically write output file data before finishing fsync likewise, but also write metadata Each FLAG symbol may be: append append mode (makes sense only for output; conv=notrunc suggested) directory fail unless a directory dsync use synchronized I/O for data sync likewise, but also for metadata fullblock accumulate full blocks of input (iflag only) nonblock use non-blocking I/O noctty do not assign controlling terminal from file nofollow do not follow symlinks Sending a INFO signal to a running 'dd' process makes it print I/O statistics to standard error and then resume copying. Options are: --help display this help and exit --version output version information and exit AUTHOR Written by Paul Rubin, David MacKenzie, and Stuart Kemp. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO Full documentation <https://www.gnu.org/software/coreutils/dd> or available locally via: info '(coreutils) dd invocation' GNU coreutils 9.3 April 2023 DD(1)
|
dd - convert and copy a file
|
dd [OPERAND]... dd OPTION
| null | null |
webpng
| null | null | null | null | null |
phpize
|
phpize is a shell script to prepare PHP extension for compiling.
|
phpize - prepare a PHP extension for compiling
|
phpize [options]
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--clean Remove all created files --help Prints usage information --version -v Prints API version information SEE ALSO php(1) VERSION INFORMATION This manpage describes php, version 8.3.9. COPYRIGHT Copyright © The PHP Group This source file is subject to version 3.01 of the PHP license, that is bundled with this package in the file LICENSE, and is available through the world-wide-web at the following url: https://www.php.net/license/3_01.txt If you did not receive a copy of the PHP license and are unable to obtain it through the world-wide-web, please send a note to license@php.net so we can mail you a copy immediately. The PHP Group 2024 phpize(1)
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sndfile-cmp
|
sndfile-cmp compares the audio data of two sound files. For two files to compare as being the same, their channel counts, sample rate, audio data lengths and actual audio data must match. Other differences such as string metadata like song title, artist etc and their presence or absence are ignored. EXIT STATUS 0 The audio data is the same. 1 The audio data differs. SEE ALSO http://libsndfile.github.io/libsndfile/ AUTHORS Conrad Parker <conrad@metadecks.org> Erik de Castro Lopo <erikd@mega-nerd.com> macOS 14.5 November 2, 2014 macOS 14.5
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sndfile-cmp – compare two audio files
|
sndfile-cmp file1 file2
| null | null |
aclocal
| null | null | null | null | null |
gcc-13
|
When you invoke GCC, it normally does preprocessing, compilation, assembly and linking. The "overall options" allow you to stop this process at an intermediate stage. For example, the -c option says not to run the linker. Then the output consists of object files output by the assembler. Other options are passed on to one or more stages of processing. Some options control the preprocessor and others the compiler itself. Yet other options control the assembler and linker; most of these are not documented here, since you rarely need to use any of them. Most of the command-line options that you can use with GCC are useful for C programs; when an option is only useful with another language (usually C++), the explanation says so explicitly. If the description for a particular option does not mention a source language, you can use that option with all supported languages. The usual way to run GCC is to run the executable called gcc, or machine-gcc when cross-compiling, or machine-gcc-version to run a specific version of GCC. When you compile C++ programs, you should invoke GCC as g++ instead. The gcc program accepts options and file names as operands. Many options have multi-letter names; therefore multiple single-letter options may not be grouped: -dv is very different from -d -v. You can mix options and other arguments. For the most part, the order you use doesn't matter. Order does matter when you use several options of the same kind; for example, if you specify -L more than once, the directories are searched in the order specified. Also, the placement of the -l option is significant. Many options have long names starting with -f or with -W---for example, -fmove-loop-invariants, -Wformat and so on. Most of these have both positive and negative forms; the negative form of -ffoo is -fno-foo. This manual documents only one of these two forms, whichever one is not the default. Some options take one or more arguments typically separated either by a space or by the equals sign (=) from the option name. Unless documented otherwise, an argument can be either numeric or a string. Numeric arguments must typically be small unsigned decimal or hexadecimal integers. Hexadecimal arguments must begin with the 0x prefix. Arguments to options that specify a size threshold of some sort may be arbitrarily large decimal or hexadecimal integers followed by a byte size suffix designating a multiple of bytes such as "kB" and "KiB" for kilobyte and kibibyte, respectively, "MB" and "MiB" for megabyte and mebibyte, "GB" and "GiB" for gigabyte and gigibyte, and so on. Such arguments are designated by byte-size in the following text. Refer to the NIST, IEC, and other relevant national and international standards for the full listing and explanation of the binary and decimal byte size prefixes.
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gcc - GNU project C and C++ compiler
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gcc [-c|-S|-E] [-std=standard] [-g] [-pg] [-Olevel] [-Wwarn...] [-Wpedantic] [-Idir...] [-Ldir...] [-Dmacro[=defn]...] [-Umacro] [-foption...] [-mmachine-option...] [-o outfile] [@file] infile... Only the most useful options are listed here; see below for the remainder. g++ accepts mostly the same options as gcc.
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Option Summary Here is a summary of all the options, grouped by type. Explanations are in the following sections. Overall Options -c -S -E -o file -dumpbase dumpbase -dumpbase-ext auxdropsuf -dumpdir dumppfx -x language -v -### --help[=class[,...]] --target-help --version -pass-exit-codes -pipe -specs=file -wrapper @file -ffile-prefix-map=old=new -fcanon-prefix-map -fplugin=file -fplugin-arg-name=arg -fdump-ada-spec[-slim] -fada-spec-parent=unit -fdump-go-spec=file C Language Options -ansi -std=standard -aux-info filename -fno-asm -fno-builtin -fno-builtin-function -fcond-mismatch -ffreestanding -fgimple -fgnu-tm -fgnu89-inline -fhosted -flax-vector-conversions -fms-extensions -foffload=arg -foffload-options=arg -fopenacc -fopenacc-dim=geom -fopenmp -fopenmp-simd -fopenmp-target-simd-clone[=device-type] -fpermitted-flt-eval-methods=standard -fplan9-extensions -fsigned-bitfields -funsigned-bitfields -fsigned-char -funsigned-char -fstrict-flex-arrays[=n] -fsso-struct=endianness C++ Language Options -fabi-version=n -fno-access-control -faligned-new=n -fargs-in-order=n -fchar8_t -fcheck-new -fconstexpr-depth=n -fconstexpr-cache-depth=n -fconstexpr-loop-limit=n -fconstexpr-ops-limit=n -fno-elide-constructors -fno-enforce-eh-specs -fno-gnu-keywords -fno-implicit-templates -fno-implicit-inline-templates -fno-implement-inlines -fmodule-header[=kind] -fmodule-only -fmodules-ts -fmodule-implicit-inline -fno-module-lazy -fmodule-mapper=specification -fmodule-version-ignore -fms-extensions -fnew-inheriting-ctors -fnew-ttp-matching -fno-nonansi-builtins -fnothrow-opt -fno-operator-names -fno-optional-diags -fpermissive -fno-pretty-templates -fno-rtti -fsized-deallocation -ftemplate-backtrace-limit=n -ftemplate-depth=n -fno-threadsafe-statics -fuse-cxa-atexit -fno-weak -nostdinc++ -fvisibility-inlines-hidden -fvisibility-ms-compat -fext-numeric-literals -flang-info-include-translate[=header] -flang-info-include-translate-not -flang-info-module-cmi[=module] -stdlib=libstdc++,libc++ -Wabi-tag -Wcatch-value -Wcatch-value=n -Wno-class-conversion -Wclass-memaccess -Wcomma-subscript -Wconditionally-supported -Wno-conversion-null -Wctad-maybe-unsupported -Wctor-dtor-privacy -Wdangling-reference -Wno-delete-incomplete -Wdelete-non-virtual-dtor -Wno-deprecated-array-compare -Wdeprecated-copy -Wdeprecated-copy-dtor -Wno-deprecated-enum-enum-conversion -Wno-deprecated-enum-float-conversion -Weffc++ -Wno-exceptions -Wextra-semi -Wno-inaccessible-base -Wno-inherited-variadic-ctor -Wno-init-list-lifetime -Winvalid-constexpr -Winvalid-imported-macros -Wno-invalid-offsetof -Wno-literal-suffix -Wmismatched-new-delete -Wmismatched-tags -Wmultiple-inheritance -Wnamespaces -Wnarrowing -Wnoexcept -Wnoexcept-type -Wnon-virtual-dtor -Wpessimizing-move -Wno-placement-new -Wplacement-new=n -Wrange-loop-construct -Wredundant-move -Wredundant-tags -Wreorder -Wregister -Wstrict-null-sentinel -Wno-subobject-linkage -Wtemplates -Wno-non-template-friend -Wold-style-cast -Woverloaded-virtual -Wno-pmf-conversions -Wself-move -Wsign-promo -Wsized-deallocation -Wsuggest-final-methods -Wsuggest-final-types -Wsuggest-override -Wno-terminate -Wuseless-cast -Wno-vexing-parse -Wvirtual-inheritance -Wno-virtual-move-assign -Wvolatile -Wzero-as-null-pointer-constant Objective-C and Objective-C++ Language Options -fconstant-string-class=class-name -fgnu-runtime -fnext-runtime -fno-nil-receivers -fobjc-abi-version=n -fobjc-call-cxx-cdtors -fobjc-direct-dispatch -fobjc-exceptions -fobjc-gc -fobjc-nilcheck -fobjc-std=objc1 -fno-local-ivars -fivar-visibility=[public|protected|private|package] -freplace-objc-classes -fzero-link -gen-decls -Wassign-intercept -Wno-property-assign-default -Wno-protocol -Wobjc-root-class -Wselector -Wstrict-selector-match -Wundeclared-selector Diagnostic Message Formatting Options -fmessage-length=n -fdiagnostics-plain-output -fdiagnostics-show-location=[once|every-line] -fdiagnostics-color=[auto|never|always] -fdiagnostics-urls=[auto|never|always] -fdiagnostics-format=[text|sarif-stderr|sarif-file|json|json- stderr|json-file] -fno-diagnostics-show-option -fno-diagnostics-show-caret -fno-diagnostics-show-labels -fno-diagnostics-show-line-numbers -fno-diagnostics-show-cwe -fno-diagnostics-show-rule -fdiagnostics-minimum-margin-width=width -fdiagnostics-parseable-fixits -fdiagnostics-generate-patch -fdiagnostics-show-template-tree -fno-elide-type -fdiagnostics-path-format=[none|separate-events|inline-events] -fdiagnostics-show-path-depths -fno-show-column -fdiagnostics-column-unit=[display|byte] -fdiagnostics-column-origin=origin -fdiagnostics-escape-format=[unicode|bytes] Warning Options -fsyntax-only -fmax-errors=n -Wpedantic -pedantic-errors -w -Wextra -Wall -Wabi=n -Waddress -Wno-address-of-packed-member -Waggregate-return -Walloc-size-larger-than=byte-size -Walloc-zero -Walloca -Walloca-larger-than=byte-size -Wno-aggressive-loop-optimizations -Warith-conversion -Warray-bounds -Warray-bounds=n -Warray-compare -Wno-attributes -Wattribute-alias=n -Wno-attribute-alias -Wno-attribute-warning -Wbidi-chars=[none|unpaired|any|ucn] -Wbool-compare -Wbool-operation -Wno-builtin-declaration-mismatch -Wno-builtin-macro-redefined -Wc90-c99-compat -Wc99-c11-compat -Wc11-c2x-compat -Wc++-compat -Wc++11-compat -Wc++14-compat -Wc++17-compat -Wc++20-compat -Wno-c++11-extensions -Wno-c++14-extensions -Wno-c++17-extensions -Wno-c++20-extensions -Wno-c++23-extensions -Wcast-align -Wcast-align=strict -Wcast-function-type -Wcast-qual -Wchar-subscripts -Wclobbered -Wcomment -Wno-complain-wrong-lang -Wconversion -Wno-coverage-mismatch -Wno-cpp -Wdangling-else -Wdangling-pointer -Wdangling-pointer=n -Wdate-time -Wno-deprecated -Wno-deprecated-declarations -Wno-designated-init -Wdisabled-optimization -Wno-discarded-array-qualifiers -Wno-discarded-qualifiers -Wno-div-by-zero -Wdouble-promotion -Wduplicated-branches -Wduplicated-cond -Wempty-body -Wno-endif-labels -Wenum-compare -Wenum-conversion -Wenum-int-mismatch -Werror -Werror=* -Wexpansion-to-defined -Wfatal-errors -Wfloat-conversion -Wfloat-equal -Wformat -Wformat=2 -Wno-format-contains-nul -Wno-format-extra-args -Wformat-nonliteral -Wformat-overflow=n -Wformat-security -Wformat-signedness -Wformat-truncation=n -Wformat-y2k -Wframe-address -Wframe-larger-than=byte-size -Wno-free-nonheap-object -Wno-if-not-aligned -Wno-ignored-attributes -Wignored-qualifiers -Wno-incompatible-pointer-types -Wimplicit -Wimplicit-fallthrough -Wimplicit-fallthrough=n -Wno-implicit-function-declaration -Wno-implicit-int -Winfinite-recursion -Winit-self -Winline -Wno-int-conversion -Wint-in-bool-context -Wno-int-to-pointer-cast -Wno-invalid-memory-model -Winvalid-pch -Winvalid-utf8 -Wno-unicode -Wjump-misses-init -Wlarger-than=byte-size -Wlogical-not-parentheses -Wlogical-op -Wlong-long -Wno-lto-type-mismatch -Wmain -Wmaybe-uninitialized -Wmemset-elt-size -Wmemset-transposed-args -Wmisleading-indentation -Wmissing-attributes -Wmissing-braces -Wmissing-field-initializers -Wmissing-format-attribute -Wmissing-include-dirs -Wmissing-noreturn -Wno-missing-profile -Wno-multichar -Wmultistatement-macros -Wnonnull -Wnonnull-compare -Wnormalized=[none|id|nfc|nfkc] -Wnull-dereference -Wno-odr -Wopenacc-parallelism -Wopenmp-simd -Wno-overflow -Woverlength-strings -Wno-override-init-side-effects -Wpacked -Wno-packed-bitfield-compat -Wpacked-not-aligned -Wpadded -Wparentheses -Wno-pedantic-ms-format -Wpointer-arith -Wno-pointer-compare -Wno-pointer-to-int-cast -Wno-pragmas -Wno-prio-ctor-dtor -Wredundant-decls -Wrestrict -Wno-return-local-addr -Wreturn-type -Wno-scalar-storage-order -Wsequence-point -Wshadow -Wshadow=global -Wshadow=local -Wshadow=compatible-local -Wno-shadow-ivar -Wno-shift-count-negative -Wno-shift-count-overflow -Wshift-negative-value -Wno-shift-overflow -Wshift-overflow=n -Wsign-compare -Wsign-conversion -Wno-sizeof-array-argument -Wsizeof-array-div -Wsizeof-pointer-div -Wsizeof-pointer-memaccess -Wstack-protector -Wstack-usage=byte-size -Wstrict-aliasing -Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=n -Wstring-compare -Wno-stringop-overflow -Wno-stringop-overread -Wno-stringop-truncation -Wstrict-flex-arrays -Wsuggest-attribute=[pure|const|noreturn|format|malloc] -Wswitch -Wno-switch-bool -Wswitch-default -Wswitch-enum -Wno-switch-outside-range -Wno-switch-unreachable -Wsync-nand -Wsystem-headers -Wtautological-compare -Wtrampolines -Wtrigraphs -Wtrivial-auto-var-init -Wtsan -Wtype-limits -Wundef -Wuninitialized -Wunknown-pragmas -Wunsuffixed-float-constants -Wunused -Wunused-but-set-parameter -Wunused-but-set-variable -Wunused-const-variable -Wunused-const-variable=n -Wunused-function -Wunused-label -Wunused-local-typedefs -Wunused-macros -Wunused-parameter -Wno-unused-result -Wunused-value -Wunused-variable -Wno-varargs -Wvariadic-macros -Wvector-operation-performance -Wvla -Wvla-larger-than=byte-size -Wno-vla-larger-than -Wvolatile-register-var -Wwrite-strings -Wxor-used-as-pow -Wzero-length-bounds Static Analyzer Options -fanalyzer -fanalyzer-call-summaries -fanalyzer-checker=name -fno-analyzer-feasibility -fanalyzer-fine-grained -fno-analyzer-state-merge -fno-analyzer-state-purge -fno-analyzer-suppress-followups -fanalyzer-transitivity -fno-analyzer-undo-inlining -fanalyzer-verbose-edges -fanalyzer-verbose-state-changes -fanalyzer-verbosity=level -fdump-analyzer -fdump-analyzer-callgraph -fdump-analyzer-exploded-graph -fdump-analyzer-exploded-nodes -fdump-analyzer-exploded-nodes-2 -fdump-analyzer-exploded-nodes-3 -fdump-analyzer-exploded-paths -fdump-analyzer-feasibility -fdump-analyzer-json -fdump-analyzer-state-purge -fdump-analyzer-stderr -fdump-analyzer-supergraph -fdump-analyzer-untracked -Wno-analyzer-double-fclose -Wno-analyzer-double-free -Wno-analyzer-exposure-through-output-file -Wno-analyzer-exposure-through-uninit-copy -Wno-analyzer-fd-access-mode-mismatch -Wno-analyzer-fd-double-close -Wno-analyzer-fd-leak -Wno-analyzer-fd-phase-mismatch -Wno-analyzer-fd-type-mismatch -Wno-analyzer-fd-use-after-close -Wno-analyzer-fd-use-without-check -Wno-analyzer-file-leak -Wno-analyzer-free-of-non-heap -Wno-analyzer-imprecise-fp-arithmetic -Wno-analyzer-infinite-recursion -Wno-analyzer-jump-through-null -Wno-analyzer-malloc-leak -Wno-analyzer-mismatching-deallocation -Wno-analyzer-null-argument -Wno-analyzer-null-dereference -Wno-analyzer-out-of-bounds -Wno-analyzer-possible-null-argument -Wno-analyzer-possible-null-dereference -Wno-analyzer-putenv-of-auto-var -Wno-analyzer-shift-count-negative -Wno-analyzer-shift-count-overflow -Wno-analyzer-stale-setjmp-buffer -Wno-analyzer-tainted-allocation-size -Wno-analyzer-tainted-assertion -Wno-analyzer-tainted-array-index -Wno-analyzer-tainted-divisor -Wno-analyzer-tainted-offset -Wno-analyzer-tainted-size -Wanalyzer-too-complex -Wno-analyzer-unsafe-call-within-signal-handler -Wno-analyzer-use-after-free -Wno-analyzer-use-of-pointer-in-stale-stack-frame -Wno-analyzer-use-of-uninitialized-value -Wno-analyzer-va-arg-type-mismatch -Wno-analyzer-va-list-exhausted -Wno-analyzer-va-list-leak -Wno-analyzer-va-list-use-after-va-end -Wno-analyzer-write-to-const -Wno-analyzer-write-to-string-literal C and Objective-C-only Warning Options -Wbad-function-cast -Wmissing-declarations -Wmissing-parameter-type -Wmissing-prototypes -Wnested-externs -Wold-style-declaration -Wold-style-definition -Wstrict-prototypes -Wtraditional -Wtraditional-conversion -Wdeclaration-after-statement -Wpointer-sign Debugging Options -g -glevel -gdwarf -gdwarf-version -gbtf -gctf -gctflevel -ggdb -grecord-gcc-switches -gno-record-gcc-switches -gstrict-dwarf -gno-strict-dwarf -gas-loc-support -gno-as-loc-support -gas-locview-support -gno-as-locview-support -gcolumn-info -gno-column-info -gdwarf32 -gdwarf64 -gstatement-frontiers -gno-statement-frontiers -gvariable-location-views -gno-variable-location-views -ginternal-reset-location-views -gno-internal-reset-location-views -ginline-points -gno-inline-points -gvms -gz[=type] -gsplit-dwarf -gdescribe-dies -gno-describe-dies -fdebug-prefix-map=old=new -fdebug-types-section -fno-eliminate-unused-debug-types -femit-struct-debug-baseonly -femit-struct-debug-reduced -femit-struct-debug-detailed[=spec-list] -fno-eliminate-unused-debug-symbols -femit-class-debug-always -fno-merge-debug-strings -fno-dwarf2-cfi-asm -fvar-tracking -fvar-tracking-assignments Optimization Options -faggressive-loop-optimizations -falign-functions[=n[:m:[n2[:m2]]]] -falign-jumps[=n[:m:[n2[:m2]]]] -falign-labels[=n[:m:[n2[:m2]]]] -falign-loops[=n[:m:[n2[:m2]]]] -fno-allocation-dce -fallow-store-data-races -fassociative-math -fauto-profile -fauto-profile[=path] -fauto-inc-dec -fbranch-probabilities -fcaller-saves -fcombine-stack-adjustments -fconserve-stack -fcompare-elim -fcprop-registers -fcrossjumping -fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules -fcx-limited-range -fdata-sections -fdce -fdelayed-branch -fdelete-null-pointer-checks -fdevirtualize -fdevirtualize-speculatively -fdevirtualize-at-ltrans -fdse -fearly-inlining -fipa-sra -fexpensive-optimizations -ffat-lto-objects -ffast-math -ffinite-math-only -ffloat-store -fexcess-precision=style -ffinite-loops -fforward-propagate -ffp-contract=style -ffunction-sections -fgcse -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity -fgcse-sm -fhoist-adjacent-loads -fif-conversion -fif-conversion2 -findirect-inlining -finline-functions -finline-functions-called-once -finline-limit=n -finline-small-functions -fipa-modref -fipa-cp -fipa-cp-clone -fipa-bit-cp -fipa-vrp -fipa-pta -fipa-profile -fipa-pure-const -fipa-reference -fipa-reference-addressable -fipa-stack-alignment -fipa-icf -fira-algorithm=algorithm -flive-patching=level -fira-region=region -fira-hoist-pressure -fira-loop-pressure -fno-ira-share-save-slots -fno-ira-share-spill-slots -fisolate-erroneous-paths-dereference -fisolate-erroneous-paths-attribute -fivopts -fkeep-inline-functions -fkeep-static-functions -fkeep-static-consts -flimit-function-alignment -flive-range-shrinkage -floop-block -floop-interchange -floop-strip-mine -floop-unroll-and-jam -floop-nest-optimize -floop-parallelize-all -flra-remat -flto -flto-compression-level -flto-partition=alg -fmerge-all-constants -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves -fmove-loop-invariants -fmove-loop-stores -fno-branch-count-reg -fno-defer-pop -fno-fp-int-builtin-inexact -fno-function-cse -fno-guess-branch-probability -fno-inline -fno-math-errno -fno-peephole -fno-peephole2 -fno-printf-return-value -fno-sched-interblock -fno-sched-spec -fno-signed-zeros -fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss -fomit-frame-pointer -foptimize-sibling-calls -fpartial-inlining -fpeel-loops -fpredictive-commoning -fprefetch-loop-arrays -fprofile-correction -fprofile-use -fprofile-use=path -fprofile-partial-training -fprofile-values -fprofile-reorder-functions -freciprocal-math -free -frename-registers -freorder-blocks -freorder-blocks-algorithm=algorithm -freorder-blocks-and-partition -freorder-functions -frerun-cse-after-loop -freschedule-modulo-scheduled-loops -frounding-math -fsave-optimization-record -fsched2-use-superblocks -fsched-pressure -fsched-spec-load -fsched-spec-load-dangerous -fsched-stalled-insns-dep[=n] -fsched-stalled-insns[=n] -fsched-group-heuristic -fsched-critical-path-heuristic -fsched-spec-insn-heuristic -fsched-rank-heuristic -fsched-last-insn-heuristic -fsched-dep-count-heuristic -fschedule-fusion -fschedule-insns -fschedule-insns2 -fsection-anchors -fselective-scheduling -fselective-scheduling2 -fsel-sched-pipelining -fsel-sched-pipelining-outer-loops -fsemantic-interposition -fshrink-wrap -fshrink-wrap-separate -fsignaling-nans -fsingle-precision-constant -fsplit-ivs-in-unroller -fsplit-loops -fsplit-paths -fsplit-wide-types -fsplit-wide-types-early -fssa-backprop -fssa-phiopt -fstdarg-opt -fstore-merging -fstrict-aliasing -fipa-strict-aliasing -fthread-jumps -ftracer -ftree-bit-ccp -ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-coalesce-vars -ftree-copy-prop -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre -fcode-hoisting -ftree-loop-if-convert -ftree-loop-im -ftree-phiprop -ftree-loop-distribution -ftree-loop-distribute-patterns -ftree-loop-ivcanon -ftree-loop-linear -ftree-loop-optimize -ftree-loop-vectorize -ftree-parallelize-loops=n -ftree-pre -ftree-partial-pre -ftree-pta -ftree-reassoc -ftree-scev-cprop -ftree-sink -ftree-slsr -ftree-sra -ftree-switch-conversion -ftree-tail-merge -ftree-ter -ftree-vectorize -ftree-vrp -ftrivial-auto-var-init -funconstrained-commons -funit-at-a-time -funroll-all-loops -funroll-loops -funsafe-math-optimizations -funswitch-loops -fipa-ra -fvariable-expansion-in-unroller -fvect-cost-model -fvpt -fweb -fwhole-program -fwpa -fuse-linker-plugin -fzero-call-used-regs --param name=value -O -O0 -O1 -O2 -O3 -Os -Ofast -Og -Oz Program Instrumentation Options -p -pg -fprofile-arcs --coverage -ftest-coverage -fprofile-abs-path -fprofile-dir=path -fprofile-generate -fprofile-generate=path -fprofile-info-section -fprofile-info-section=name -fprofile-note=path -fprofile-prefix-path=path -fprofile-update=method -fprofile-filter-files=regex -fprofile-exclude-files=regex -fprofile-reproducible=[multithreaded|parallel-runs|serial] -fsanitize=style -fsanitize-recover -fsanitize-recover=style -fsanitize-trap -fsanitize-trap=style -fasan-shadow-offset=number -fsanitize-sections=s1,s2,... -fsanitize-undefined-trap-on-error -fbounds-check -fcf-protection=[full|branch|return|none|check] -fharden-compares -fharden-conditional-branches -fstack-protector -fstack-protector-all -fstack-protector-strong -fstack-protector-explicit -fstack-check -fstack-limit-register=reg -fstack-limit-symbol=sym -fno-stack-limit -fsplit-stack -fvtable-verify=[std|preinit|none] -fvtv-counts -fvtv-debug -finstrument-functions -finstrument-functions-once -finstrument-functions-exclude-function-list=sym,sym,... -finstrument-functions-exclude-file-list=file,file,... -fprofile-prefix-map=old=new Preprocessor Options -Aquestion=answer -A-question[=answer] -C -CC -Dmacro[=defn] -dD -dI -dM -dN -dU -fdebug-cpp -fdirectives-only -fdollars-in-identifiers -fexec-charset=charset -fextended-identifiers -finput-charset=charset -flarge-source-files -fmacro-prefix-map=old=new -fmax-include-depth=depth -fno-canonical-system-headers -fpch-deps -fpch-preprocess -fpreprocessed -ftabstop=width -ftrack-macro-expansion -fwide-exec-charset=charset -fworking-directory -H -imacros file -include file -M -MD -MF -MG -MM -MMD -MP -MQ -MT -Mno-modules -no-integrated-cpp -P -pthread -remap -traditional -traditional-cpp -trigraphs -Umacro -undef -Wp,option -Xpreprocessor option Assembler Options -Wa,option -Xassembler option Linker Options object-file-name -fuse-ld=linker -llibrary -nostartfiles -nodefaultlibs -nolibc -nostdlib -nostdlib++ -e entry --entry=entry -pie -pthread -r -rdynamic -s -static -static-pie -static-libgcc -static-libstdc++ -static-libasan -static-libtsan -static-liblsan -static-libubsan -shared -shared-libgcc -symbolic -T script -Wl,option -Xlinker option -u symbol -z keyword Directory Options -Bprefix -Idir -I- -idirafter dir -imacros file -imultilib dir -iplugindir=dir -iprefix file -iquote dir -isysroot dir -isystem dir -iwithprefix dir -iwithprefixbefore dir -Ldir -no-canonical-prefixes --no-sysroot-suffix -nostdinc -nostdinc++ --sysroot=dir Code Generation Options -fcall-saved-reg -fcall-used-reg -ffixed-reg -fexceptions -fnon-call-exceptions -fdelete-dead-exceptions -funwind-tables -fasynchronous-unwind-tables -fno-gnu-unique -finhibit-size-directive -fcommon -fno-ident -fpcc-struct-return -fpic -fPIC -fpie -fPIE -fno-plt -fno-jump-tables -fno-bit-tests -frecord-gcc-switches -freg-struct-return -fshort-enums -fshort-wchar -fverbose-asm -fpack-struct[=n] -fleading-underscore -ftls-model=model -fstack-reuse=reuse_level -fstack-use-cumulative-args -ftrampolines -foff-stack-trampolines -ftrapv -fwrapv -fvisibility=[default|internal|hidden|protected] -fstrict-volatile-bitfields -fsync-libcalls Developer Options -dletters -dumpspecs -dumpmachine -dumpversion -dumpfullversion -fcallgraph-info[=su,da] -fchecking -fchecking=n -fdbg-cnt-list -fdbg-cnt=counter-value-list -fdisable-ipa-pass_name -fdisable-rtl-pass_name -fdisable-rtl-pass-name=range-list -fdisable-tree-pass_name -fdisable-tree-pass-name=range-list -fdump-debug -fdump-earlydebug -fdump-noaddr -fdump-unnumbered -fdump-unnumbered-links -fdump-final-insns[=file] -fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline -fdump-lang-all -fdump-lang-switch -fdump-lang-switch-options -fdump-lang-switch-options=filename -fdump-passes -fdump-rtl-pass -fdump-rtl-pass=filename -fdump-statistics -fdump-tree-all -fdump-tree-switch -fdump-tree-switch-options -fdump-tree-switch-options=filename -fcompare-debug[=opts] -fcompare-debug-second -fenable-kind-pass -fenable-kind-pass=range- list -fira-verbose=n -flto-report -flto-report-wpa -fmem-report-wpa -fmem-report -fpre-ipa-mem-report -fpost-ipa-mem-report -fopt-info -fopt-info-options[=file] -fmultiflags -fprofile-report -frandom-seed=string -fsched-verbose=n -fsel-sched-verbose -fsel-sched-dump-cfg -fsel-sched-pipelining-verbose -fstats -fstack-usage -ftime-report -ftime-report-details -fvar-tracking-assignments-toggle -gtoggle -print-file-name=library -print-libgcc-file-name -print-multi-directory -print-multi-lib -print-multi-os-directory -print-prog-name=program -print-search-dirs -Q -print-sysroot -print-sysroot-headers-suffix -save-temps -save-temps=cwd -save-temps=obj -time[=file] Machine-Dependent Options AArch64 Options -mabi=name -mbig-endian -mlittle-endian -mgeneral-regs-only -mcmodel=tiny -mcmodel=small -mcmodel=large -mstrict-align -mno-strict-align -momit-leaf-frame-pointer -mtls-dialect=desc -mtls-dialect=traditional -mtls-size=size -mfix-cortex-a53-835769 -mfix-cortex-a53-843419 -mlow-precision-recip-sqrt -mlow-precision-sqrt -mlow-precision-div -mpc-relative-literal-loads -msign-return-address=scope -mbranch-protection=none|standard|pac- ret[+leaf +b-key]|bti -mharden-sls=opts -march=name -mcpu=name -mtune=name -moverride=string -mverbose-cost-dump -mstack-protector-guard=guard -mstack-protector-guard-reg=sysreg -mstack-protector-guard-offset=offset -mtrack-speculation -moutline-atomics Adapteva Epiphany Options -mhalf-reg-file -mprefer-short-insn-regs -mbranch-cost=num -mcmove -mnops=num -msoft-cmpsf -msplit-lohi -mpost-inc -mpost-modify -mstack-offset=num -mround-nearest -mlong-calls -mshort-calls -msmall16 -mfp-mode=mode -mvect-double -max-vect-align=num -msplit-vecmove-early -m1reg-reg AMD GCN Options -march=gpu -mtune=gpu -mstack-size=bytes ARC Options -mbarrel-shifter -mjli-always -mcpu=cpu -mA6 -mARC600 -mA7 -mARC700 -mdpfp -mdpfp-compact -mdpfp-fast -mno-dpfp-lrsr -mea -mno-mpy -mmul32x16 -mmul64 -matomic -mnorm -mspfp -mspfp-compact -mspfp-fast -msimd -msoft-float -mswap -mcrc -mdsp-packa -mdvbf -mlock -mmac-d16 -mmac-24 -mrtsc -mswape -mtelephony -mxy -misize -mannotate-align -marclinux -marclinux_prof -mlong-calls -mmedium-calls -msdata -mirq-ctrl-saved -mrgf-banked-regs -mlpc-width=width -G num -mvolatile-cache -mtp-regno=regno -malign-call -mauto-modify-reg -mbbit-peephole -mno-brcc -mcase-vector-pcrel -mcompact-casesi -mno-cond-exec -mearly-cbranchsi -mexpand-adddi -mindexed-loads -mlra -mlra-priority-none -mlra-priority-compact -mlra-priority-noncompact -mmillicode -mmixed-code -mq-class -mRcq -mRcw -msize-level=level -mtune=cpu -mmultcost=num -mcode-density-frame -munalign-prob-threshold=probability -mmpy-option=multo -mdiv-rem -mcode-density -mll64 -mfpu=fpu -mrf16 -mbranch-index ARM Options -mapcs-frame -mno-apcs-frame -mabi=name -mapcs-stack-check -mno-apcs-stack-check -mapcs-reentrant -mno-apcs-reentrant -mgeneral-regs-only -msched-prolog -mno-sched-prolog -mlittle-endian -mbig-endian -mbe8 -mbe32 -mfloat-abi=name -mfp16-format=name -mthumb-interwork -mno-thumb-interwork -mcpu=name -march=name -mfpu=name -mtune=name -mprint-tune-info -mstructure-size-boundary=n -mabort-on-noreturn -mlong-calls -mno-long-calls -msingle-pic-base -mno-single-pic-base -mpic-register=reg -mnop-fun-dllimport -mpoke-function-name -mthumb -marm -mflip-thumb -mtpcs-frame -mtpcs-leaf-frame -mcaller-super-interworking -mcallee-super-interworking -mtp=name -mtls-dialect=dialect -mword-relocations -mfix-cortex-m3-ldrd -mfix-cortex-a57-aes-1742098 -mfix-cortex-a72-aes-1655431 -munaligned-access -mneon-for-64bits -mslow-flash-data -masm-syntax-unified -mrestrict-it -mverbose-cost-dump -mpure-code -mcmse -mfix-cmse-cve-2021-35465 -mstack-protector-guard=guard -mstack-protector-guard-offset=offset -mfdpic -mbranch-protection=none|standard|pac-ret[+leaf] [+bti]|bti[+pac- ret[+leaf]] AVR Options -mmcu=mcu -mabsdata -maccumulate-args -mbranch-cost=cost -mcall-prologues -mgas-isr-prologues -mint8 -mdouble=bits -mlong-double=bits -mn_flash=size -mno-interrupts -mmain-is-OS_task -mrelax -mrmw -mstrict-X -mtiny-stack -mfract-convert-truncate -mshort-calls -nodevicelib -nodevicespecs -Waddr-space-convert -Wmisspelled-isr Blackfin Options -mcpu=cpu[-sirevision] -msim -momit-leaf-frame-pointer -mno-omit-leaf-frame-pointer -mspecld-anomaly -mno-specld-anomaly -mcsync-anomaly -mno-csync-anomaly -mlow-64k -mno-low64k -mstack-check-l1 -mid-shared-library -mno-id-shared-library -mshared-library-id=n -mleaf-id-shared-library -mno-leaf-id-shared-library -msep-data -mno-sep-data -mlong-calls -mno-long-calls -mfast-fp -minline-plt -mmulticore -mcorea -mcoreb -msdram -micplb C6X Options -mbig-endian -mlittle-endian -march=cpu -msim -msdata=sdata-type CRIS Options -mcpu=cpu -march=cpu -mtune=cpu -mmax-stack-frame=n -metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects -mstack-align -mdata-align -mconst-align -m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -melf -maout -sim -sim2 -mmul-bug-workaround -mno-mul-bug-workaround C-SKY Options -march=arch -mcpu=cpu -mbig-endian -EB -mlittle-endian -EL -mhard-float -msoft-float -mfpu=fpu -mdouble-float -mfdivdu -mfloat-abi=name -melrw -mistack -mmp -mcp -mcache -msecurity -mtrust -mdsp -medsp -mvdsp -mdiv -msmart -mhigh-registers -manchor -mpushpop -mmultiple-stld -mconstpool -mstack-size -mccrt -mbranch-cost=n -mcse-cc -msched-prolog -msim Darwin Options -all_load -allowable_client -arch -arch_errors_fatal -arch_only -bind_at_load -bundle -bundle_loader -client_name -compatibility_version -current_version -dead_strip -dependency-file -dylib_file -dylinker_install_name -dynamic -dynamiclib -exported_symbols_list -filelist -flat_namespace -force_cpusubtype_ALL -force_flat_namespace -headerpad_max_install_names -iframework -image_base -init -install_name -keep_private_externs -multi_module -multiply_defined -multiply_defined_unused -noall_load -no_dead_strip_inits_and_terms -nofixprebinding -nomultidefs -noprebind -noseglinkedit -pagezero_size -prebind -prebind_all_twolevel_modules -private_bundle -read_only_relocs -sectalign -sectobjectsymbols -whyload -seg1addr -sectcreate -sectobjectsymbols -sectorder -segaddr -segs_read_only_addr -segs_read_write_addr -seg_addr_table -seg_addr_table_filename -seglinkedit -segprot -segs_read_only_addr -segs_read_write_addr -single_module -static -sub_library -sub_umbrella -twolevel_namespace -umbrella -undefined -unexported_symbols_list -weak_reference_mismatches -whatsloaded -F -gused -gfull -mmacosx-version-min=version -mkernel -mone-byte-bool DEC Alpha Options -mno-fp-regs -msoft-float -mieee -mieee-with-inexact -mieee-conformant -mfp-trap-mode=mode -mfp-rounding-mode=mode -mtrap-precision=mode -mbuild-constants -mcpu=cpu-type -mtune=cpu-type -mbwx -mmax -mfix -mcix -mfloat-vax -mfloat-ieee -mexplicit-relocs -msmall-data -mlarge-data -msmall-text -mlarge-text -mmemory-latency=time eBPF Options -mbig-endian -mlittle-endian -mkernel=version -mframe-limit=bytes -mxbpf -mco-re -mno-co-re -mjmpext -mjmp32 -malu32 -mcpu=version FR30 Options -msmall-model -mno-lsim FT32 Options -msim -mlra -mnodiv -mft32b -mcompress -mnopm FRV Options -mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64 -mhard-float -msoft-float -malloc-cc -mfixed-cc -mdword -mno-dword -mdouble -mno-double -mmedia -mno-media -mmuladd -mno-muladd -mfdpic -minline-plt -mgprel-ro -multilib-library-pic -mlinked-fp -mlong-calls -malign-labels -mlibrary-pic -macc-4 -macc-8 -mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move -moptimize-membar -mno-optimize-membar -mscc -mno-scc -mcond-exec -mno-cond-exec -mvliw-branch -mno-vliw-branch -mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec -mno-nested-cond-exec -mtomcat-stats -mTLS -mtls -mcpu=cpu GNU/Linux Options -mglibc -muclibc -mmusl -mbionic -mandroid -tno-android-cc -tno-android-ld H8/300 Options -mrelax -mh -ms -mn -mexr -mno-exr -mint32 -malign-300 HPPA Options -march=architecture-type -matomic-libcalls -mbig-switch -mcaller-copies -mdisable-fpregs -mdisable-indexing -mordered -mfast-indirect-calls -mgas -mgnu-ld -mhp-ld -mfixed-range=register-range -mcoherent-ldcw -mjump-in-delay -mlinker-opt -mlong-calls -mlong-load-store -mno-atomic-libcalls -mno-disable-fpregs -mno-disable-indexing -mno-fast-indirect-calls -mno-gas -mno-jump-in-delay -mno-long-load-store -mno-portable-runtime -mno-soft-float -mno-space-regs -msoft-float -mpa-risc-1-0 -mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime -mschedule=cpu-type -mspace-regs -msoft-mult -msio -mwsio -munix=unix-std -nolibdld -static -threads IA-64 Options -mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic -mvolatile-asm-stop -mregister-names -msdata -mno-sdata -mconstant-gp -mauto-pic -mfused-madd -minline-float-divide-min-latency -minline-float-divide-max-throughput -mno-inline-float-divide -minline-int-divide-min-latency -minline-int-divide-max-throughput -mno-inline-int-divide -minline-sqrt-min-latency -minline-sqrt-max-throughput -mno-inline-sqrt -mdwarf2-asm -mearly-stop-bits -mfixed-range=register-range -mtls-size=tls-size -mtune=cpu-type -milp32 -mlp64 -msched-br-data-spec -msched-ar-data-spec -msched-control-spec -msched-br-in-data-spec -msched-ar-in-data-spec -msched-in-control-spec -msched-spec-ldc -msched-spec-control-ldc -msched-prefer-non-data-spec-insns -msched-prefer-non-control-spec-insns -msched-stop-bits-after-every-cycle -msched-count-spec-in-critical-path -msel-sched-dont-check-control-spec -msched-fp-mem-deps-zero-cost -msched-max-memory-insns-hard-limit -msched-max-memory-insns=max- insns LM32 Options -mbarrel-shift-enabled -mdivide-enabled -mmultiply-enabled -msign-extend-enabled -muser-enabled LoongArch Options -march=cpu-type -mtune=cpu-type -mabi=base-abi- type -mfpu=fpu-type -msoft-float -msingle-float -mdouble-float -mbranch-cost=n -mcheck-zero-division -mno-check-zero-division -mcond-move-int -mno-cond-move-int -mcond-move-float -mno-cond-move-float -memcpy -mno-memcpy -mstrict-align -mno-strict-align -mmax-inline-memcpy-size=n -mexplicit-relocs -mno-explicit-relocs -mdirect-extern-access -mno-direct-extern-access -mcmodel=code-model M32R/D Options -m32r2 -m32rx -m32r -mdebug -malign-loops -mno-align-loops -missue-rate=number -mbranch-cost=number -mmodel=code-size-model-type -msdata=sdata-type -mno-flush-func -mflush-func=name -mno-flush-trap -mflush-trap=number -G num M32C Options -mcpu=cpu -msim -memregs=number M680x0 Options -march=arch -mcpu=cpu -mtune=tune -m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 -m68060 -mcpu32 -m5200 -m5206e -m528x -m5307 -m5407 -mcfv4e -mbitfield -mno-bitfield -mc68000 -mc68020 -mnobitfield -mrtd -mno-rtd -mdiv -mno-div -mshort -mno-short -mhard-float -m68881 -msoft-float -mpcrel -malign-int -mstrict-align -msep-data -mno-sep-data -mshared-library-id=n -mid-shared-library -mno-id-shared-library -mxgot -mno-xgot -mlong-jump-table-offsets MCore Options -mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates -mno-relax-immediates -mwide-bitfields -mno-wide-bitfields -m4byte-functions -mno-4byte-functions -mcallgraph-data -mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim -mlittle-endian -mbig-endian -m210 -m340 -mstack-increment MicroBlaze Options -msoft-float -mhard-float -msmall-divides -mcpu=cpu -mmemcpy -mxl-soft-mul -mxl-soft-div -mxl-barrel-shift -mxl-pattern-compare -mxl-stack-check -mxl-gp-opt -mno-clearbss -mxl-multiply-high -mxl-float-convert -mxl-float-sqrt -mbig-endian -mlittle-endian -mxl-reorder -mxl-mode-app-model -mpic-data-is-text-relative MIPS Options -EL -EB -march=arch -mtune=arch -mips1 -mips2 -mips3 -mips4 -mips32 -mips32r2 -mips32r3 -mips32r5 -mips32r6 -mips64 -mips64r2 -mips64r3 -mips64r5 -mips64r6 -mips16 -mno-mips16 -mflip-mips16 -minterlink-compressed -mno-interlink-compressed -minterlink-mips16 -mno-interlink-mips16 -mabi=abi -mabicalls -mno-abicalls -mshared -mno-shared -mplt -mno-plt -mxgot -mno-xgot -mgp32 -mgp64 -mfp32 -mfpxx -mfp64 -mhard-float -msoft-float -mno-float -msingle-float -mdouble-float -modd-spreg -mno-odd-spreg -mabs=mode -mnan=encoding -mdsp -mno-dsp -mdspr2 -mno-dspr2 -mmcu -mmno-mcu -meva -mno-eva -mvirt -mno-virt -mxpa -mno-xpa -mcrc -mno-crc -mginv -mno-ginv -mmicromips -mno-micromips -mmsa -mno-msa -mloongson-mmi -mno-loongson-mmi -mloongson-ext -mno-loongson-ext -mloongson-ext2 -mno-loongson-ext2 -mfpu=fpu- type -msmartmips -mno-smartmips -mpaired-single -mno-paired-single -mdmx -mno-mdmx -mips3d -mno-mips3d -mmt -mno-mt -mllsc -mno-llsc -mlong64 -mlong32 -msym32 -mno-sym32 -Gnum -mlocal-sdata -mno-local-sdata -mextern-sdata -mno-extern-sdata -mgpopt -mno-gopt -membedded-data -mno-embedded-data -muninit-const-in-rodata -mno-uninit-const-in-rodata -mcode-readable=setting -msplit-addresses -mno-split-addresses -mexplicit-relocs -mno-explicit-relocs -mcheck-zero-division -mno-check-zero-division -mdivide-traps -mdivide-breaks -mload-store-pairs -mno-load-store-pairs -munaligned-access -mno-unaligned-access -mmemcpy -mno-memcpy -mlong-calls -mno-long-calls -mmad -mno-mad -mimadd -mno-imadd -mfused-madd -mno-fused-madd -nocpp -mfix-24k -mno-fix-24k -mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 -mfix-r5900 -mno-fix-r5900 -mfix-r10000 -mno-fix-r10000 -mfix-rm7000 -mno-fix-rm7000 -mfix-vr4120 -mno-fix-vr4120 -mfix-vr4130 -mno-fix-vr4130 -mfix-sb1 -mno-fix-sb1 -mflush-func=func -mno-flush-func -mbranch-cost=num -mbranch-likely -mno-branch-likely -mcompact-branches=policy -mfp-exceptions -mno-fp-exceptions -mvr4130-align -mno-vr4130-align -msynci -mno-synci -mlxc1-sxc1 -mno-lxc1-sxc1 -mmadd4 -mno-madd4 -mrelax-pic-calls -mno-relax-pic-calls -mmcount-ra-address -mframe-header-opt -mno-frame-header-opt MMIX Options -mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu -mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols -melf -mbranch-predict -mno-branch-predict -mbase-addresses -mno-base-addresses -msingle-exit -mno-single-exit MN10300 Options -mmult-bug -mno-mult-bug -mno-am33 -mam33 -mam33-2 -mam34 -mtune=cpu-type -mreturn-pointer-on-d0 -mno-crt0 -mrelax -mliw -msetlb Moxie Options -meb -mel -mmul.x -mno-crt0 MSP430 Options -msim -masm-hex -mmcu= -mcpu= -mlarge -msmall -mrelax -mwarn-mcu -mcode-region= -mdata-region= -msilicon-errata= -msilicon-errata-warn= -mhwmult= -minrt -mtiny-printf -mmax-inline-shift= NDS32 Options -mbig-endian -mlittle-endian -mreduced-regs -mfull-regs -mcmov -mno-cmov -mext-perf -mno-ext-perf -mext-perf2 -mno-ext-perf2 -mext-string -mno-ext-string -mv3push -mno-v3push -m16bit -mno-16bit -misr-vector-size=num -mcache-block-size=num -march=arch -mcmodel=code-model -mctor-dtor -mrelax Nios II Options -G num -mgpopt=option -mgpopt -mno-gpopt -mgprel-sec=regexp -mr0rel-sec=regexp -mel -meb -mno-bypass-cache -mbypass-cache -mno-cache-volatile -mcache-volatile -mno-fast-sw-div -mfast-sw-div -mhw-mul -mno-hw-mul -mhw-mulx -mno-hw-mulx -mno-hw-div -mhw-div -mcustom-insn=N -mno-custom-insn -mcustom-fpu-cfg=name -mhal -msmallc -msys-crt0=name -msys-lib=name -march=arch -mbmx -mno-bmx -mcdx -mno-cdx Nvidia PTX Options -m64 -mmainkernel -moptimize OpenRISC Options -mboard=name -mnewlib -mhard-mul -mhard-div -msoft-mul -msoft-div -msoft-float -mhard-float -mdouble-float -munordered-float -mcmov -mror -mrori -msext -msfimm -mshftimm -mcmodel=code-model PDP-11 Options -mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 -mint32 -mno-int16 -mint16 -mno-int32 -msplit -munix-asm -mdec-asm -mgnu-asm -mlra PowerPC Options See RS/6000 and PowerPC Options. PRU Options -mmcu=mcu -minrt -mno-relax -mloop -mabi=variant RISC-V Options -mbranch-cost=N-instruction -mplt -mno-plt -mabi=ABI-string -mfdiv -mno-fdiv -mdiv -mno-div -misa-spec=ISA- spec-string -march=ISA-string -mtune=processor-string -mpreferred-stack-boundary=num -msmall-data-limit=N-bytes -msave-restore -mno-save-restore -mshorten-memrefs -mno-shorten-memrefs -mstrict-align -mno-strict-align -mcmodel=medlow -mcmodel=medany -mexplicit-relocs -mno-explicit-relocs -mrelax -mno-relax -mriscv-attribute -mno-riscv-attribute -malign-data=type -mbig-endian -mlittle-endian -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset -mcsr-check -mno-csr-check -minline-atomics -mno-inline-atomics RL78 Options -msim -mmul=none -mmul=g13 -mmul=g14 -mallregs -mcpu=g10 -mcpu=g13 -mcpu=g14 -mg10 -mg13 -mg14 -m64bit-doubles -m32bit-doubles -msave-mduc-in-interrupts RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model -mpowerpc64 -maltivec -mno-altivec -mpowerpc-gpopt -mno-powerpc-gpopt -mpowerpc-gfxopt -mno-powerpc-gfxopt -mmfcrf -mno-mfcrf -mpopcntb -mno-popcntb -mpopcntd -mno-popcntd -mfprnd -mno-fprnd -mcmpb -mno-cmpb -mhard-dfp -mno-hard-dfp -mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc -m64 -m32 -mxl-compat -mno-xl-compat -mpe -malign-power -malign-natural -msoft-float -mhard-float -mmultiple -mno-multiple -mupdate -mno-update -mavoid-indexed-addresses -mno-avoid-indexed-addresses -mfused-madd -mno-fused-madd -mbit-align -mno-bit-align -mstrict-align -mno-strict-align -mrelocatable -mno-relocatable -mrelocatable-lib -mno-relocatable-lib -mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian -mdynamic-no-pic -mswdiv -msingle-pic-base -mprioritize-restricted-insns=priority -msched-costly-dep=dependence_type -minsert-sched-nops=scheme -mcall-aixdesc -mcall-eabi -mcall-freebsd -mcall-linux -mcall-netbsd -mcall-openbsd -mcall-sysv -mcall-sysv-eabi -mcall-sysv-noeabi -mtraceback=traceback_type -maix-struct-return -msvr4-struct-return -mabi=abi-type -msecure-plt -mbss-plt -mlongcall -mno-longcall -mpltseq -mno-pltseq -mblock-move-inline-limit=num -mblock-compare-inline-limit=num -mblock-compare-inline-loop-limit=num -mno-block-ops-unaligned-vsx -mstring-compare-inline-limit=num -misel -mno-isel -mvrsave -mno-vrsave -mmulhw -mno-mulhw -mdlmzb -mno-dlmzb -mprototype -mno-prototype -msim -mmvme -mads -myellowknife -memb -msdata -msdata=opt -mreadonly-in-sdata -mvxworks -G num -mrecip -mrecip=opt -mno-recip -mrecip-precision -mno-recip-precision -mveclibabi=type -mfriz -mno-friz -mpointers-to-nested-functions -mno-pointers-to-nested-functions -msave-toc-indirect -mno-save-toc-indirect -mpower8-fusion -mno-mpower8-fusion -mpower8-vector -mno-power8-vector -mcrypto -mno-crypto -mhtm -mno-htm -mquad-memory -mno-quad-memory -mquad-memory-atomic -mno-quad-memory-atomic -mcompat-align-parm -mno-compat-align-parm -mfloat128 -mno-float128 -mfloat128-hardware -mno-float128-hardware -mgnu-attribute -mno-gnu-attribute -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset -mprefixed -mno-prefixed -mpcrel -mno-pcrel -mmma -mno-mmma -mrop-protect -mno-rop-protect -mprivileged -mno-privileged RX Options -m64bit-doubles -m32bit-doubles -fpu -nofpu -mcpu= -mbig-endian-data -mlittle-endian-data -msmall-data -msim -mno-sim -mas100-syntax -mno-as100-syntax -mrelax -mmax-constant-size= -mint-register= -mpid -mallow-string-insns -mno-allow-string-insns -mjsr -mno-warn-multiple-fast-interrupts -msave-acc-in-interrupts S/390 and zSeries Options -mtune=cpu-type -march=cpu-type -mhard-float -msoft-float -mhard-dfp -mno-hard-dfp -mlong-double-64 -mlong-double-128 -mbackchain -mno-backchain -mpacked-stack -mno-packed-stack -msmall-exec -mno-small-exec -mmvcle -mno-mvcle -m64 -m31 -mdebug -mno-debug -mesa -mzarch -mhtm -mvx -mzvector -mtpf-trace -mno-tpf-trace -mtpf-trace-skip -mno-tpf-trace-skip -mfused-madd -mno-fused-madd -mwarn-framesize -mwarn-dynamicstack -mstack-size -mstack-guard -mhotpatch=halfwords,halfwords SH Options -m1 -m2 -m2e -m2a-nofpu -m2a-single-only -m2a-single -m2a -m3 -m3e -m4-nofpu -m4-single-only -m4-single -m4 -m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al -mb -ml -mdalign -mrelax -mbigtable -mfmovd -mrenesas -mno-renesas -mnomacsave -mieee -mno-ieee -mbitops -misize -minline-ic_invalidate -mpadstruct -mprefergot -musermode -multcost=number -mdiv=strategy -mdivsi3_libfunc=name -mfixed-range=register-range -maccumulate-outgoing-args -matomic-model=atomic-model -mbranch-cost=num -mzdcbranch -mno-zdcbranch -mcbranch-force-delay-slot -mfused-madd -mno-fused-madd -mfsca -mno-fsca -mfsrra -mno-fsrra -mpretend-cmove -mtas Solaris 2 Options -mclear-hwcap -mno-clear-hwcap -mimpure-text -mno-impure-text -pthreads SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model -mmemory-model=mem-model -m32 -m64 -mapp-regs -mno-app-regs -mfaster-structs -mno-faster-structs -mflat -mno-flat -mfpu -mno-fpu -mhard-float -msoft-float -mhard-quad-float -msoft-quad-float -mstack-bias -mno-stack-bias -mstd-struct-return -mno-std-struct-return -munaligned-doubles -mno-unaligned-doubles -muser-mode -mno-user-mode -mv8plus -mno-v8plus -mvis -mno-vis -mvis2 -mno-vis2 -mvis3 -mno-vis3 -mvis4 -mno-vis4 -mvis4b -mno-vis4b -mcbcond -mno-cbcond -mfmaf -mno-fmaf -mfsmuld -mno-fsmuld -mpopc -mno-popc -msubxc -mno-subxc -mfix-at697f -mfix-ut699 -mfix-ut700 -mfix-gr712rc -mlra -mno-lra System V Options -Qy -Qn -YP,paths -Ym,dir V850 Options -mlong-calls -mno-long-calls -mep -mno-ep -mprolog-function -mno-prolog-function -mspace -mtda=n -msda=n -mzda=n -mapp-regs -mno-app-regs -mdisable-callt -mno-disable-callt -mv850e2v3 -mv850e2 -mv850e1 -mv850es -mv850e -mv850 -mv850e3v5 -mloop -mrelax -mlong-jumps -msoft-float -mhard-float -mgcc-abi -mrh850-abi -mbig-switch VAX Options -mg -mgnu -munix -mlra Visium Options -mdebug -msim -mfpu -mno-fpu -mhard-float -msoft-float -mcpu=cpu-type -mtune=cpu-type -msv-mode -muser-mode VMS Options -mvms-return-codes -mdebug-main=prefix -mmalloc64 -mpointer-size=size VxWorks Options -mrtp -non-static -Bstatic -Bdynamic -Xbind-lazy -Xbind-now x86 Options -mtune=cpu-type -march=cpu-type -mtune-ctrl=feature- list -mdump-tune-features -mno-default -mfpmath=unit -masm=dialect -mno-fancy-math-387 -mno-fp-ret-in-387 -m80387 -mhard-float -msoft-float -mno-wide-multiply -mrtd -malign-double -mpreferred-stack-boundary=num -mincoming-stack-boundary=num -mcld -mcx16 -msahf -mmovbe -mcrc32 -mmwait -mrecip -mrecip=opt -mvzeroupper -mprefer-avx128 -mprefer-vector-width=opt -mmove-max=bits -mstore-max=bits -mmmx -msse -msse2 -msse3 -mssse3 -msse4.1 -msse4.2 -msse4 -mavx -mavx2 -mavx512f -mavx512pf -mavx512er -mavx512cd -mavx512vl -mavx512bw -mavx512dq -mavx512ifma -mavx512vbmi -msha -maes -mpclmul -mfsgsbase -mrdrnd -mf16c -mfma -mpconfig -mwbnoinvd -mptwrite -mprefetchwt1 -mclflushopt -mclwb -mxsavec -mxsaves -msse4a -m3dnow -m3dnowa -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop -madx -mlzcnt -mbmi2 -mfxsr -mxsave -mxsaveopt -mrtm -mhle -mlwp -mmwaitx -mclzero -mpku -mthreads -mgfni -mvaes -mwaitpkg -mshstk -mmanual-endbr -mcet-switch -mforce-indirect-call -mavx512vbmi2 -mavx512bf16 -menqcmd -mvpclmulqdq -mavx512bitalg -mmovdiri -mmovdir64b -mavx512vpopcntdq -mavx5124fmaps -mavx512vnni -mavx5124vnniw -mprfchw -mrdpid -mrdseed -msgx -mavx512vp2intersect -mserialize -mtsxldtrk -mamx-tile -mamx-int8 -mamx-bf16 -muintr -mhreset -mavxvnni -mavx512fp16 -mavxifma -mavxvnniint8 -mavxneconvert -mcmpccxadd -mamx-fp16 -mprefetchi -mraoint -mamx-complex -mcldemote -mms-bitfields -mno-align-stringops -minline-all-stringops -minline-stringops-dynamically -mstringop-strategy=alg -mkl -mwidekl -mmemcpy-strategy=strategy -mmemset-strategy=strategy -mpush-args -maccumulate-outgoing-args -m128bit-long-double -m96bit-long-double -mlong-double-64 -mlong-double-80 -mlong-double-128 -mregparm=num -msseregparm -mveclibabi=type -mvect8-ret-in-mem -mpc32 -mpc64 -mpc80 -mdaz-ftz -mstackrealign -momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs -mcmodel=code-model -mabi=name -maddress-mode=mode -m32 -m64 -mx32 -m16 -miamcu -mlarge-data-threshold=num -msse2avx -mfentry -mrecord-mcount -mnop-mcount -m8bit-idiv -minstrument-return=type -mfentry-name=name -mfentry-section=name -mavx256-split-unaligned-load -mavx256-split-unaligned-store -malign-data=type -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset -mstack-protector-guard-symbol=symbol -mgeneral-regs-only -mcall-ms2sysv-xlogues -mrelax-cmpxchg-loop -mindirect-branch=choice -mfunction-return=choice -mindirect-branch-register -mharden-sls=choice -mindirect-branch-cs-prefix -mneeded -mno-direct-extern-access -munroll-only-small-loops -mlam=choice x86 Windows Options -mconsole -mcygwin -mno-cygwin -mdll -mnop-fun-dllimport -mthread -municode -mwin32 -mwindows -fno-set-stack-executable Xstormy16 Options -msim Xtensa Options -mconst16 -mno-const16 -mfused-madd -mno-fused-madd -mforce-no-pic -mserialize-volatile -mno-serialize-volatile -mtext-section-literals -mno-text-section-literals -mauto-litpools -mno-auto-litpools -mtarget-align -mno-target-align -mlongcalls -mno-longcalls -mabi=abi-type -mextra-l32r-costs=cycles zSeries Options See S/390 and zSeries Options. Options Controlling the Kind of Output Compilation can involve up to four stages: preprocessing, compilation proper, assembly and linking, always in that order. GCC is capable of preprocessing and compiling several files either into several assembler input files, or into one assembler input file; then each assembler input file produces an object file, and linking combines all the object files (those newly compiled, and those specified as input) into an executable file. For any given input file, the file name suffix determines what kind of compilation is done: file.c C source code that must be preprocessed. file.i C source code that should not be preprocessed. file.ii C++ source code that should not be preprocessed. file.m Objective-C source code. Note that you must link with the libobjc library to make an Objective-C program work. file.mi Objective-C source code that should not be preprocessed. file.mm file.M Objective-C++ source code. Note that you must link with the libobjc library to make an Objective-C++ program work. Note that .M refers to a literal capital M. file.mii Objective-C++ source code that should not be preprocessed. file.h C, C++, Objective-C or Objective-C++ header file to be turned into a precompiled header (default), or C, C++ header file to be turned into an Ada spec (via the -fdump-ada-spec switch). file.cc file.cp file.cxx file.cpp file.CPP file.c++ file.C C++ source code that must be preprocessed. Note that in .cxx, the last two letters must both be literally x. Likewise, .C refers to a literal capital C. file.mm file.M Objective-C++ source code that must be preprocessed. file.mii Objective-C++ source code that should not be preprocessed. file.hh file.H file.hp file.hxx file.hpp file.HPP file.h++ file.tcc C++ header file to be turned into a precompiled header or Ada spec. file.f file.for file.ftn Fixed form Fortran source code that should not be preprocessed. file.F file.FOR file.fpp file.FPP file.FTN Fixed form Fortran source code that must be preprocessed (with the traditional preprocessor). file.f90 file.f95 file.f03 file.f08 Free form Fortran source code that should not be preprocessed. file.F90 file.F95 file.F03 file.F08 Free form Fortran source code that must be preprocessed (with the traditional preprocessor). file.go Go source code. file.d D source code. file.di D interface file. file.dd D documentation code (Ddoc). file.ads Ada source code file that contains a library unit declaration (a declaration of a package, subprogram, or generic, or a generic instantiation), or a library unit renaming declaration (a package, generic, or subprogram renaming declaration). Such files are also called specs. file.adb Ada source code file containing a library unit body (a subprogram or package body). Such files are also called bodies. file.s Assembler code. file.S file.sx Assembler code that must be preprocessed. other An object file to be fed straight into linking. Any file name with no recognized suffix is treated this way. You can specify the input language explicitly with the -x option: -x language Specify explicitly the language for the following input files (rather than letting the compiler choose a default based on the file name suffix). This option applies to all following input files until the next -x option. Possible values for language are: c c-header cpp-output c++ c++-header c++-system-header c++-user-header c++-cpp-output objective-c objective-c-header objective-c-cpp-output objective-c++ objective-c++-header objective-c++-cpp-output assembler assembler-with-cpp ada d f77 f77-cpp-input f95 f95-cpp-input go -x none Turn off any specification of a language, so that subsequent files are handled according to their file name suffixes (as they are if -x has not been used at all). If you only want some of the stages of compilation, you can use -x (or filename suffixes) to tell gcc where to start, and one of the options -c, -S, or -E to say where gcc is to stop. Note that some combinations (for example, -x cpp-output -E) instruct gcc to do nothing at all. -c Compile or assemble the source files, but do not link. The linking stage simply is not done. The ultimate output is in the form of an object file for each source file. By default, the object file name for a source file is made by replacing the suffix .c, .i, .s, etc., with .o. Unrecognized input files, not requiring compilation or assembly, are ignored. -S Stop after the stage of compilation proper; do not assemble. The output is in the form of an assembler code file for each non- assembler input file specified. By default, the assembler file name for a source file is made by replacing the suffix .c, .i, etc., with .s. Input files that don't require compilation are ignored. -E Stop after the preprocessing stage; do not run the compiler proper. The output is in the form of preprocessed source code, which is sent to the standard output. Input files that don't require preprocessing are ignored. -o file Place the primary output in file file. This applies to whatever sort of output is being produced, whether it be an executable file, an object file, an assembler file or preprocessed C code. If -o is not specified, the default is to put an executable file in a.out, the object file for source.suffix in source.o, its assembler file in source.s, a precompiled header file in source.suffix.gch, and all preprocessed C source on standard output. Though -o names only the primary output, it also affects the naming of auxiliary and dump outputs. See the examples below. Unless overridden, both auxiliary outputs and dump outputs are placed in the same directory as the primary output. In auxiliary outputs, the suffix of the input file is replaced with that of the auxiliary output file type; in dump outputs, the suffix of the dump file is appended to the input file suffix. In compilation commands, the base name of both auxiliary and dump outputs is that of the primary output; in compile and link commands, the primary output name, minus the executable suffix, is combined with the input file name. If both share the same base name, disregarding the suffix, the result of the combination is that base name, otherwise, they are concatenated, separated by a dash. gcc -c foo.c ... will use foo.o as the primary output, and place aux outputs and dumps next to it, e.g., aux file foo.dwo for -gsplit-dwarf, and dump file foo.c.???r.final for -fdump-rtl-final. If a non-linker output file is explicitly specified, aux and dump files by default take the same base name: gcc -c foo.c -o dir/foobar.o ... will name aux outputs dir/foobar.* and dump outputs dir/foobar.c.*. A linker output will instead prefix aux and dump outputs: gcc foo.c bar.c -o dir/foobar ... will generally name aux outputs dir/foobar-foo.* and dir/foobar-bar.*, and dump outputs dir/foobar-foo.c.* and dir/foobar-bar.c.*. The one exception to the above is when the executable shares the base name with the single input: gcc foo.c -o dir/foo ... in which case aux outputs are named dir/foo.* and dump outputs named dir/foo.c.*. The location and the names of auxiliary and dump outputs can be adjusted by the options -dumpbase, -dumpbase-ext, -dumpdir, -save-temps=cwd, and -save-temps=obj. -dumpbase dumpbase This option sets the base name for auxiliary and dump output files. It does not affect the name of the primary output file. Intermediate outputs, when preserved, are not regarded as primary outputs, but as auxiliary outputs: gcc -save-temps -S foo.c saves the (no longer) temporary preprocessed file in foo.i, and then compiles to the (implied) output file foo.s, whereas: gcc -save-temps -dumpbase save-foo -c foo.c preprocesses to in save-foo.i, compiles to save-foo.s (now an intermediate, thus auxiliary output), and then assembles to the (implied) output file foo.o. Absent this option, dump and aux files take their names from the input file, or from the (non-linker) output file, if one is explicitly specified: dump output files (e.g. those requested by -fdump-* options) with the input name suffix, and aux output files (those requested by other non-dump options, e.g. "-save-temps", "-gsplit-dwarf", "-fcallgraph-info") without it. Similar suffix differentiation of dump and aux outputs can be attained for explicitly-given -dumpbase basename.suf by also specifying -dumpbase-ext .suf. If dumpbase is explicitly specified with any directory component, any dumppfx specification (e.g. -dumpdir or -save-temps=*) is ignored, and instead of appending to it, dumpbase fully overrides it: gcc foo.c -c -o dir/foo.o -dumpbase alt/foo \ -dumpdir pfx- -save-temps=cwd ... creates auxiliary and dump outputs named alt/foo.*, disregarding dir/ in -o, the ./ prefix implied by -save-temps=cwd, and pfx- in -dumpdir. When -dumpbase is specified in a command that compiles multiple inputs, or that compiles and then links, it may be combined with dumppfx, as specified under -dumpdir. Then, each input file is compiled using the combined dumppfx, and default values for dumpbase and auxdropsuf are computed for each input file: gcc foo.c bar.c -c -dumpbase main ... creates foo.o and bar.o as primary outputs, and avoids overwriting the auxiliary and dump outputs by using the dumpbase as a prefix, creating auxiliary and dump outputs named main-foo.* and main-bar.*. An empty string specified as dumpbase avoids the influence of the output basename in the naming of auxiliary and dump outputs during compilation, computing default values : gcc -c foo.c -o dir/foobar.o -dumpbase " ... will name aux outputs dir/foo.* and dump outputs dir/foo.c.*. Note how their basenames are taken from the input name, but the directory still defaults to that of the output. The empty-string dumpbase does not prevent the use of the output basename for outputs during linking: gcc foo.c bar.c -o dir/foobar -dumpbase " -flto ... The compilation of the source files will name auxiliary outputs dir/foo.* and dir/bar.*, and dump outputs dir/foo.c.* and dir/bar.c.*. LTO recompilation during linking will use dir/foobar. as the prefix for dumps and auxiliary files. -dumpbase-ext auxdropsuf When forming the name of an auxiliary (but not a dump) output file, drop trailing auxdropsuf from dumpbase before appending any suffixes. If not specified, this option defaults to the suffix of a default dumpbase, i.e., the suffix of the input file when -dumpbase is not present in the command line, or dumpbase is combined with dumppfx. gcc foo.c -c -o dir/foo.o -dumpbase x-foo.c -dumpbase-ext .c ... creates dir/foo.o as the main output, and generates auxiliary outputs in dir/x-foo.*, taking the location of the primary output, and dropping the .c suffix from the dumpbase. Dump outputs retain the suffix: dir/x-foo.c.*. This option is disregarded if it does not match the suffix of a specified dumpbase, except as an alternative to the executable suffix when appending the linker output base name to dumppfx, as specified below: gcc foo.c bar.c -o main.out -dumpbase-ext .out ... creates main.out as the primary output, and avoids overwriting the auxiliary and dump outputs by using the executable name minus auxdropsuf as a prefix, creating auxiliary outputs named main-foo.* and main-bar.* and dump outputs named main-foo.c.* and main-bar.c.*. -dumpdir dumppfx When forming the name of an auxiliary or dump output file, use dumppfx as a prefix: gcc -dumpdir pfx- -c foo.c ... creates foo.o as the primary output, and auxiliary outputs named pfx-foo.*, combining the given dumppfx with the default dumpbase derived from the default primary output, derived in turn from the input name. Dump outputs also take the input name suffix: pfx-foo.c.*. If dumppfx is to be used as a directory name, it must end with a directory separator: gcc -dumpdir dir/ -c foo.c -o obj/bar.o ... creates obj/bar.o as the primary output, and auxiliary outputs named dir/bar.*, combining the given dumppfx with the default dumpbase derived from the primary output name. Dump outputs also take the input name suffix: dir/bar.c.*. It defaults to the location of the output file, unless the output file is a special file like "/dev/null". Options -save-temps=cwd and -save-temps=obj override this default, just like an explicit -dumpdir option. In case multiple such options are given, the last one prevails: gcc -dumpdir pfx- -c foo.c -save-temps=obj ... outputs foo.o, with auxiliary outputs named foo.* because -save-temps=* overrides the dumppfx given by the earlier -dumpdir option. It does not matter that =obj is the default for -save-temps, nor that the output directory is implicitly the current directory. Dump outputs are named foo.c.*. When compiling from multiple input files, if -dumpbase is specified, dumpbase, minus a auxdropsuf suffix, and a dash are appended to (or override, if containing any directory components) an explicit or defaulted dumppfx, so that each of the multiple compilations gets differently-named aux and dump outputs. gcc foo.c bar.c -c -dumpdir dir/pfx- -dumpbase main ... outputs auxiliary dumps to dir/pfx-main-foo.* and dir/pfx-main-bar.*, appending dumpbase- to dumppfx. Dump outputs retain the input file suffix: dir/pfx-main-foo.c.* and dir/pfx-main-bar.c.*, respectively. Contrast with the single-input compilation: gcc foo.c -c -dumpdir dir/pfx- -dumpbase main ... that, applying -dumpbase to a single source, does not compute and append a separate dumpbase per input file. Its auxiliary and dump outputs go in dir/pfx-main.*. When compiling and then linking from multiple input files, a defaulted or explicitly specified dumppfx also undergoes the dumpbase- transformation above (e.g. the compilation of foo.c and bar.c above, but without -c). If neither -dumpdir nor -dumpbase are given, the linker output base name, minus auxdropsuf, if specified, or the executable suffix otherwise, plus a dash is appended to the default dumppfx instead. Note, however, that unlike earlier cases of linking: gcc foo.c bar.c -dumpdir dir/pfx- -o main ... does not append the output name main to dumppfx, because -dumpdir is explicitly specified. The goal is that the explicitly-specified dumppfx may contain the specified output name as part of the prefix, if desired; only an explicitly-specified -dumpbase would be combined with it, in order to avoid simply discarding a meaningful option. When compiling and then linking from a single input file, the linker output base name will only be appended to the default dumppfx as above if it does not share the base name with the single input file name. This has been covered in single-input linking cases above, but not with an explicit -dumpdir that inhibits the combination, even if overridden by -save-temps=*: gcc foo.c -dumpdir alt/pfx- -o dir/main.exe -save-temps=cwd ... Auxiliary outputs are named foo.*, and dump outputs foo.c.*, in the current working directory as ultimately requested by -save-temps=cwd. Summing it all up for an intuitive though slightly imprecise data flow: the primary output name is broken into a directory part and a basename part; dumppfx is set to the former, unless overridden by -dumpdir or -save-temps=*, and dumpbase is set to the latter, unless overriden by -dumpbase. If there are multiple inputs or linking, this dumpbase may be combined with dumppfx and taken from each input file. Auxiliary output names for each input are formed by combining dumppfx, dumpbase minus suffix, and the auxiliary output suffix; dump output names are only different in that the suffix from dumpbase is retained. When it comes to auxiliary and dump outputs created during LTO recompilation, a combination of dumppfx and dumpbase, as given or as derived from the linker output name but not from inputs, even in cases in which this combination would not otherwise be used as such, is passed down with a trailing period replacing the compiler- added dash, if any, as a -dumpdir option to lto-wrapper; being involved in linking, this program does not normally get any -dumpbase and -dumpbase-ext, and it ignores them. When running sub-compilers, lto-wrapper appends LTO stage names to the received dumppfx, ensures it contains a directory component so that it overrides any -dumpdir, and passes that as -dumpbase to sub-compilers. -v Print (on standard error output) the commands executed to run the stages of compilation. Also print the version number of the compiler driver program and of the preprocessor and the compiler proper. -### Like -v except the commands are not executed and arguments are quoted unless they contain only alphanumeric characters or "./-_". This is useful for shell scripts to capture the driver-generated command lines. --help Print (on the standard output) a description of the command-line options understood by gcc. If the -v option is also specified then --help is also passed on to the various processes invoked by gcc, so that they can display the command-line options they accept. If the -Wextra option has also been specified (prior to the --help option), then command-line options that have no documentation associated with them are also displayed. --target-help Print (on the standard output) a description of target-specific command-line options for each tool. For some targets extra target- specific information may also be printed. --help={class|[^]qualifier}[,...] Print (on the standard output) a description of the command-line options understood by the compiler that fit into all specified classes and qualifiers. These are the supported classes: optimizers Display all of the optimization options supported by the compiler. warnings Display all of the options controlling warning messages produced by the compiler. target Display target-specific options. Unlike the --target-help option however, target-specific options of the linker and assembler are not displayed. This is because those tools do not currently support the extended --help= syntax. params Display the values recognized by the --param option. language Display the options supported for language, where language is the name of one of the languages supported in this version of GCC. If an option is supported by all languages, one needs to select common class. common Display the options that are common to all languages. These are the supported qualifiers: undocumented Display only those options that are undocumented. joined Display options taking an argument that appears after an equal sign in the same continuous piece of text, such as: --help=target. separate Display options taking an argument that appears as a separate word following the original option, such as: -o output-file. Thus for example to display all the undocumented target-specific switches supported by the compiler, use: --help=target,undocumented The sense of a qualifier can be inverted by prefixing it with the ^ character, so for example to display all binary warning options (i.e., ones that are either on or off and that do not take an argument) that have a description, use: --help=warnings,^joined,^undocumented The argument to --help= should not consist solely of inverted qualifiers. Combining several classes is possible, although this usually restricts the output so much that there is nothing to display. One case where it does work, however, is when one of the classes is target. For example, to display all the target-specific optimization options, use: --help=target,optimizers The --help= option can be repeated on the command line. Each successive use displays its requested class of options, skipping those that have already been displayed. If --help is also specified anywhere on the command line then this takes precedence over any --help= option. If the -Q option appears on the command line before the --help= option, then the descriptive text displayed by --help= is changed. Instead of describing the displayed options, an indication is given as to whether the option is enabled, disabled or set to a specific value (assuming that the compiler knows this at the point where the --help= option is used). Here is a truncated example from the ARM port of gcc: % gcc -Q -mabi=2 --help=target -c The following options are target specific: -mabi= 2 -mabort-on-noreturn [disabled] -mapcs [disabled] The output is sensitive to the effects of previous command-line options, so for example it is possible to find out which optimizations are enabled at -O2 by using: -Q -O2 --help=optimizers Alternatively you can discover which binary optimizations are enabled by -O3 by using: gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts diff /tmp/O2-opts /tmp/O3-opts | grep enabled --version Display the version number and copyrights of the invoked GCC. -pass-exit-codes Normally the gcc program exits with the code of 1 if any phase of the compiler returns a non-success return code. If you specify -pass-exit-codes, the gcc program instead returns with the numerically highest error produced by any phase returning an error indication. The C, C++, and Fortran front ends return 4 if an internal compiler error is encountered. -pipe Use pipes rather than temporary files for communication between the various stages of compilation. This fails to work on some systems where the assembler is unable to read from a pipe; but the GNU assembler has no trouble. -specs=file Process file after the compiler reads in the standard specs file, in order to override the defaults which the gcc driver program uses when determining what switches to pass to cc1, cc1plus, as, ld, etc. More than one -specs=file can be specified on the command line, and they are processed in order, from left to right. -wrapper Invoke all subcommands under a wrapper program. The name of the wrapper program and its parameters are passed as a comma separated list. gcc -c t.c -wrapper gdb,--args This invokes all subprograms of gcc under gdb --args, thus the invocation of cc1 is gdb --args cc1 .... -ffile-prefix-map=old=new When compiling files residing in directory old, record any references to them in the result of the compilation as if the files resided in directory new instead. Specifying this option is equivalent to specifying all the individual -f*-prefix-map options. This can be used to make reproducible builds that are location independent. Directories referenced by directives are not affected by these options. See also -fmacro-prefix-map, -fdebug-prefix-map, -fprofile-prefix-map and -fcanon-prefix-map. -fcanon-prefix-map For the -f*-prefix-map options normally comparison of old prefix against the filename that would be normally referenced in the result of the compilation is done using textual comparison of the prefixes, or ignoring character case for case insensitive filesystems and considering slashes and backslashes as equal on DOS based filesystems. The -fcanon-prefix-map causes such comparisons to be done on canonicalized paths of old and the referenced filename. -fplugin=name.so Load the plugin code in file name.so, assumed to be a shared object to be dlopen'd by the compiler. The base name of the shared object file is used to identify the plugin for the purposes of argument parsing (See -fplugin-arg-name-key=value below). Each plugin should define the callback functions specified in the Plugins API. -fplugin-arg-name-key=value Define an argument called key with a value of value for the plugin called name. -fdump-ada-spec[-slim] For C and C++ source and include files, generate corresponding Ada specs. -fada-spec-parent=unit In conjunction with -fdump-ada-spec[-slim] above, generate Ada specs as child units of parent unit. -fdump-go-spec=file For input files in any language, generate corresponding Go declarations in file. This generates Go "const", "type", "var", and "func" declarations which may be a useful way to start writing a Go interface to code written in some other language. @file Read command-line options from file. The options read are inserted in place of the original @file option. If file does not exist, or cannot be read, then the option will be treated literally, and not removed. Options in file are separated by whitespace. A whitespace character may be included in an option by surrounding the entire option in either single or double quotes. Any character (including a backslash) may be included by prefixing the character to be included with a backslash. The file may itself contain additional @file options; any such options will be processed recursively. Compiling C++ Programs C++ source files conventionally use one of the suffixes .C, .cc, .cpp, .CPP, .c++, .cp, or .cxx; C++ header files often use .hh, .hpp, .H, or (for shared template code) .tcc; and preprocessed C++ files use the suffix .ii. GCC recognizes files with these names and compiles them as C++ programs even if you call the compiler the same way as for compiling C programs (usually with the name gcc). However, the use of gcc does not add the C++ library. g++ is a program that calls GCC and automatically specifies linking against the C++ library. It treats .c, .h and .i files as C++ source files instead of C source files unless -x is used. This program is also useful when precompiling a C header file with a .h extension for use in C++ compilations. On many systems, g++ is also installed with the name c++. When you compile C++ programs, you may specify many of the same command-line options that you use for compiling programs in any language; or command-line options meaningful for C and related languages; or options that are meaningful only for C++ programs. Options Controlling C Dialect The following options control the dialect of C (or languages derived from C, such as C++, Objective-C and Objective-C++) that the compiler accepts: -ansi In C mode, this is equivalent to -std=c90. In C++ mode, it is equivalent to -std=c++98. This turns off certain features of GCC that are incompatible with ISO C90 (when compiling C code), or of standard C++ (when compiling C++ code), such as the "asm" and "typeof" keywords, and predefined macros such as "unix" and "vax" that identify the type of system you are using. It also enables the undesirable and rarely used ISO trigraph feature. For the C compiler, it disables recognition of C++ style // comments as well as the "inline" keyword. The alternate keywords "__asm__", "__extension__", "__inline__" and "__typeof__" continue to work despite -ansi. You would not want to use them in an ISO C program, of course, but it is useful to put them in header files that might be included in compilations done with -ansi. Alternate predefined macros such as "__unix__" and "__vax__" are also available, with or without -ansi. The -ansi option does not cause non-ISO programs to be rejected gratuitously. For that, -Wpedantic is required in addition to -ansi. The macro "__STRICT_ANSI__" is predefined when the -ansi option is used. Some header files may notice this macro and refrain from declaring certain functions or defining certain macros that the ISO standard doesn't call for; this is to avoid interfering with any programs that might use these names for other things. Functions that are normally built in but do not have semantics defined by ISO C (such as "alloca" and "ffs") are not built-in functions when -ansi is used. -std= Determine the language standard. This option is currently only supported when compiling C or C++. The compiler can accept several base standards, such as c90 or c++98, and GNU dialects of those standards, such as gnu90 or gnu++98. When a base standard is specified, the compiler accepts all programs following that standard plus those using GNU extensions that do not contradict it. For example, -std=c90 turns off certain features of GCC that are incompatible with ISO C90, such as the "asm" and "typeof" keywords, but not other GNU extensions that do not have a meaning in ISO C90, such as omitting the middle term of a "?:" expression. On the other hand, when a GNU dialect of a standard is specified, all features supported by the compiler are enabled, even when those features change the meaning of the base standard. As a result, some strict-conforming programs may be rejected. The particular standard is used by -Wpedantic to identify which features are GNU extensions given that version of the standard. For example -std=gnu90 -Wpedantic warns about C++ style // comments, while -std=gnu99 -Wpedantic does not. A value for this option must be provided; possible values are c90 c89 iso9899:1990 Support all ISO C90 programs (certain GNU extensions that conflict with ISO C90 are disabled). Same as -ansi for C code. iso9899:199409 ISO C90 as modified in amendment 1. c99 c9x iso9899:1999 iso9899:199x ISO C99. This standard is substantially completely supported, modulo bugs and floating-point issues (mainly but not entirely relating to optional C99 features from Annexes F and G). See <https://gcc.gnu.org/c99status.html> for more information. The names c9x and iso9899:199x are deprecated. c11 c1x iso9899:2011 ISO C11, the 2011 revision of the ISO C standard. This standard is substantially completely supported, modulo bugs, floating-point issues (mainly but not entirely relating to optional C11 features from Annexes F and G) and the optional Annexes K (Bounds-checking interfaces) and L (Analyzability). The name c1x is deprecated. c17 c18 iso9899:2017 iso9899:2018 ISO C17, the 2017 revision of the ISO C standard (published in 2018). This standard is same as C11 except for corrections of defects (all of which are also applied with -std=c11) and a new value of "__STDC_VERSION__", and so is supported to the same extent as C11. c2x The next version of the ISO C standard, still under development. The support for this version is experimental and incomplete. gnu90 gnu89 GNU dialect of ISO C90 (including some C99 features). gnu99 gnu9x GNU dialect of ISO C99. The name gnu9x is deprecated. gnu11 gnu1x GNU dialect of ISO C11. The name gnu1x is deprecated. gnu17 gnu18 GNU dialect of ISO C17. This is the default for C code. gnu2x The next version of the ISO C standard, still under development, plus GNU extensions. The support for this version is experimental and incomplete. c++98 c++03 The 1998 ISO C++ standard plus the 2003 technical corrigendum and some additional defect reports. Same as -ansi for C++ code. gnu++98 gnu++03 GNU dialect of -std=c++98. c++11 c++0x The 2011 ISO C++ standard plus amendments. The name c++0x is deprecated. gnu++11 gnu++0x GNU dialect of -std=c++11. The name gnu++0x is deprecated. c++14 c++1y The 2014 ISO C++ standard plus amendments. The name c++1y is deprecated. gnu++14 gnu++1y GNU dialect of -std=c++14. The name gnu++1y is deprecated. c++17 c++1z The 2017 ISO C++ standard plus amendments. The name c++1z is deprecated. gnu++17 gnu++1z GNU dialect of -std=c++17. This is the default for C++ code. The name gnu++1z is deprecated. c++20 c++2a The 2020 ISO C++ standard plus amendments. Support is experimental, and could change in incompatible ways in future releases. The name c++2a is deprecated. gnu++20 gnu++2a GNU dialect of -std=c++20. Support is experimental, and could change in incompatible ways in future releases. The name gnu++2a is deprecated. c++2b c++23 The next revision of the ISO C++ standard, planned for 2023. Support is highly experimental, and will almost certainly change in incompatible ways in future releases. gnu++2b gnu++23 GNU dialect of -std=c++2b. Support is highly experimental, and will almost certainly change in incompatible ways in future releases. -aux-info filename Output to the given filename prototyped declarations for all functions declared and/or defined in a translation unit, including those in header files. This option is silently ignored in any language other than C. Besides declarations, the file indicates, in comments, the origin of each declaration (source file and line), whether the declaration was implicit, prototyped or unprototyped (I, N for new or O for old, respectively, in the first character after the line number and the colon), and whether it came from a declaration or a definition (C or F, respectively, in the following character). In the case of function definitions, a K&R-style list of arguments followed by their declarations is also provided, inside comments, after the declaration. -fno-asm Do not recognize "asm", "inline" or "typeof" as a keyword, so that code can use these words as identifiers. You can use the keywords "__asm__", "__inline__" and "__typeof__" instead. In C, -ansi implies -fno-asm. In C++, "inline" is a standard keyword and is not affected by this switch. You may want to use the -fno-gnu-keywords flag instead, which disables "typeof" but not "asm" and "inline". In C99 mode (-std=c99 or -std=gnu99), this switch only affects the "asm" and "typeof" keywords, since "inline" is a standard keyword in ISO C99. In C2X mode (-std=c2x or -std=gnu2x), this switch only affects the "asm" keyword, since "typeof" is a standard keyword in ISO C2X. -fno-builtin -fno-builtin-function Don't recognize built-in functions that do not begin with __builtin_ as prefix. GCC normally generates special code to handle certain built-in functions more efficiently; for instance, calls to "alloca" may become single instructions which adjust the stack directly, and calls to "memcpy" may become inline copy loops. The resulting code is often both smaller and faster, but since the function calls no longer appear as such, you cannot set a breakpoint on those calls, nor can you change the behavior of the functions by linking with a different library. In addition, when a function is recognized as a built-in function, GCC may use information about that function to warn about problems with calls to that function, or to generate more efficient code, even if the resulting code still contains calls to that function. For example, warnings are given with -Wformat for bad calls to "printf" when "printf" is built in and "strlen" is known not to modify global memory. With the -fno-builtin-function option only the built-in function function is disabled. function must not begin with __builtin_. If a function is named that is not built-in in this version of GCC, this option is ignored. There is no corresponding -fbuiltin-function option; if you wish to enable built-in functions selectively when using -fno-builtin or -ffreestanding, you may define macros such as: #define abs(n) __builtin_abs ((n)) #define strcpy(d, s) __builtin_strcpy ((d), (s)) -fcond-mismatch Allow conditional expressions with mismatched types in the second and third arguments. The value of such an expression is void. This option is not supported for C++. -ffreestanding Assert that compilation targets a freestanding environment. This implies -fno-builtin. A freestanding environment is one in which the standard library may not exist, and program startup may not necessarily be at "main". The most obvious example is an OS kernel. This is equivalent to -fno-hosted. -fgimple Enable parsing of function definitions marked with "__GIMPLE". This is an experimental feature that allows unit testing of GIMPLE passes. -fgnu-tm When the option -fgnu-tm is specified, the compiler generates code for the Linux variant of Intel's current Transactional Memory ABI specification document (Revision 1.1, May 6 2009). This is an experimental feature whose interface may change in future versions of GCC, as the official specification changes. Please note that not all architectures are supported for this feature. For more information on GCC's support for transactional memory, Note that the transactional memory feature is not supported with non-call exceptions (-fnon-call-exceptions). -fgnu89-inline The option -fgnu89-inline tells GCC to use the traditional GNU semantics for "inline" functions when in C99 mode. Using this option is roughly equivalent to adding the "gnu_inline" function attribute to all inline functions. The option -fno-gnu89-inline explicitly tells GCC to use the C99 semantics for "inline" when in C99 or gnu99 mode (i.e., it specifies the default behavior). This option is not supported in -std=c90 or -std=gnu90 mode. The preprocessor macros "__GNUC_GNU_INLINE__" and "__GNUC_STDC_INLINE__" may be used to check which semantics are in effect for "inline" functions. -fhosted Assert that compilation targets a hosted environment. This implies -fbuiltin. A hosted environment is one in which the entire standard library is available, and in which "main" has a return type of "int". Examples are nearly everything except a kernel. This is equivalent to -fno-freestanding. -flax-vector-conversions Allow implicit conversions between vectors with differing numbers of elements and/or incompatible element types. This option should not be used for new code. -fms-extensions Accept some non-standard constructs used in Microsoft header files. In C++ code, this allows member names in structures to be similar to previous types declarations. typedef int UOW; struct ABC { UOW UOW; }; Some cases of unnamed fields in structures and unions are only accepted with this option. Note that this option is off for all targets except for x86 targets using ms-abi. -foffload=disable -foffload=default -foffload=target-list Specify for which OpenMP and OpenACC offload targets code should be generated. The default behavior, equivalent to -foffload=default, is to generate code for all supported offload targets. The -foffload=disable form generates code only for the host fallback, while -foffload=target-list generates code only for the specified comma-separated list of offload targets. Offload targets are specified in GCC's internal target-triplet format. You can run the compiler with -v to show the list of configured offload targets under "OFFLOAD_TARGET_NAMES". -foffload-options=options -foffload-options=target-triplet-list=options With -foffload-options=options, GCC passes the specified options to the compilers for all enabled offloading targets. You can specify options that apply only to a specific target or targets by using the -foffload-options=target-list=options form. The target-list is a comma-separated list in the same format as for the -foffload= option. Typical command lines are -foffload-options=-lgfortran -foffload-options=-lm -foffload-options="-lgfortran -lm" -foffload-options=nvptx-none=-latomic -foffload-options=amdgcn-amdhsa=-march=gfx906 -foffload-options=-lm -fopenacc Enable handling of OpenACC directives "#pragma acc" in C/C++ and "!$acc" in Fortran. When -fopenacc is specified, the compiler generates accelerated code according to the OpenACC Application Programming Interface v2.6 <https://www.openacc.org>. This option implies -pthread, and thus is only supported on targets that have support for -pthread. -fopenacc-dim=geom Specify default compute dimensions for parallel offload regions that do not explicitly specify. The geom value is a triple of ':'-separated sizes, in order 'gang', 'worker' and, 'vector'. A size can be omitted, to use a target-specific default value. -fopenmp Enable handling of OpenMP directives "#pragma omp" in C/C++, "[[omp::directive(...)]]" and "[[omp::sequence(...)]]" in C++ and "!$omp" in Fortran. When -fopenmp is specified, the compiler generates parallel code according to the OpenMP Application Program Interface v4.5 <https://www.openmp.org>. This option implies -pthread, and thus is only supported on targets that have support for -pthread. -fopenmp implies -fopenmp-simd. -fopenmp-simd Enable handling of OpenMP's "simd", "declare simd", "declare reduction", "assume", "ordered", "scan", "loop" directives and combined or composite directives with "simd" as constituent with "#pragma omp" in C/C++, "[[omp::directive(...)]]" and "[[omp::sequence(...)]]" in C++ and "!$omp" in Fortran. Other OpenMP directives are ignored. -fopenmp-target-simd-clone -fopenmp-target-simd-clone=device-type In addition to generating SIMD clones for functions marked with the "declare simd" directive, GCC also generates clones for functions marked with the OpenMP "declare target" directive that are suitable for vectorization when this option is in effect. The device-type may be one of "none", "host", "nohost", and "any", which correspond to keywords for the "device_type" clause of the "declare target" directive; clones are generated for the intersection of devices specified. -fopenmp-target-simd-clone is equivalent to -fopenmp-target-simd-clone=any and -fno-openmp-target-simd-clone is equivalent to -fopenmp-target-simd-clone=none. At -O2 and higher (but not -Os or -Og) this optimization defaults to -fopenmp-target-simd-clone=nohost; otherwise it is disabled by default. -fpermitted-flt-eval-methods=style ISO/IEC TS 18661-3 defines new permissible values for "FLT_EVAL_METHOD" that indicate that operations and constants with a semantic type that is an interchange or extended format should be evaluated to the precision and range of that type. These new values are a superset of those permitted under C99/C11, which does not specify the meaning of other positive values of "FLT_EVAL_METHOD". As such, code conforming to C11 may not have been written expecting the possibility of the new values. -fpermitted-flt-eval-methods specifies whether the compiler should allow only the values of "FLT_EVAL_METHOD" specified in C99/C11, or the extended set of values specified in ISO/IEC TS 18661-3. style is either "c11" or "ts-18661-3" as appropriate. The default when in a standards compliant mode (-std=c11 or similar) is -fpermitted-flt-eval-methods=c11. The default when in a GNU dialect (-std=gnu11 or similar) is -fpermitted-flt-eval-methods=ts-18661-3. -fplan9-extensions Accept some non-standard constructs used in Plan 9 code. This enables -fms-extensions, permits passing pointers to structures with anonymous fields to functions that expect pointers to elements of the type of the field, and permits referring to anonymous fields declared using a typedef. This is only supported for C, not C++. -fsigned-bitfields -funsigned-bitfields -fno-signed-bitfields -fno-unsigned-bitfields These options control whether a bit-field is signed or unsigned, when the declaration does not use either "signed" or "unsigned". By default, such a bit-field is signed, because this is consistent: the basic integer types such as "int" are signed types. -fsigned-char Let the type "char" be signed, like "signed char". Note that this is equivalent to -fno-unsigned-char, which is the negative form of -funsigned-char. Likewise, the option -fno-signed-char is equivalent to -funsigned-char. -funsigned-char Let the type "char" be unsigned, like "unsigned char". Each kind of machine has a default for what "char" should be. It is either like "unsigned char" by default or like "signed char" by default. Ideally, a portable program should always use "signed char" or "unsigned char" when it depends on the signedness of an object. But many programs have been written to use plain "char" and expect it to be signed, or expect it to be unsigned, depending on the machines they were written for. This option, and its inverse, let you make such a program work with the opposite default. The type "char" is always a distinct type from each of "signed char" or "unsigned char", even though its behavior is always just like one of those two. -fstrict-flex-arrays Control when to treat the trailing array of a structure as a flexible array member for the purpose of accessing the elements of such an array. The positive form is equivalent to -fstrict-flex-arrays=3, which is the strictest. A trailing array is treated as a flexible array member only when it is declared as a flexible array member per C99 standard onwards. The negative form is equivalent to -fstrict-flex-arrays=0, which is the least strict. All trailing arrays of structures are treated as flexible array members. -fstrict-flex-arrays=level Control when to treat the trailing array of a structure as a flexible array member for the purpose of accessing the elements of such an array. The value of level controls the level of strictness. The possible values of level are the same as for the "strict_flex_array" attribute. You can control this behavior for a specific trailing array field of a structure by using the variable attribute "strict_flex_array" attribute. -fsso-struct=endianness Set the default scalar storage order of structures and unions to the specified endianness. The accepted values are big-endian, little-endian and native for the native endianness of the target (the default). This option is not supported for C++. Warning: the -fsso-struct switch causes GCC to generate code that is not binary compatible with code generated without it if the specified endianness is not the native endianness of the target. Options Controlling C++ Dialect This section describes the command-line options that are only meaningful for C++ programs. You can also use most of the GNU compiler options regardless of what language your program is in. For example, you might compile a file firstClass.C like this: g++ -g -fstrict-enums -O -c firstClass.C In this example, only -fstrict-enums is an option meant only for C++ programs; you can use the other options with any language supported by GCC. Some options for compiling C programs, such as -std, are also relevant for C++ programs. Here is a list of options that are only for compiling C++ programs: -fabi-version=n Use version n of the C++ ABI. The default is version 0. Version 0 refers to the version conforming most closely to the C++ ABI specification. Therefore, the ABI obtained using version 0 will change in different versions of G++ as ABI bugs are fixed. Version 1 is the version of the C++ ABI that first appeared in G++ 3.2. Version 2 is the version of the C++ ABI that first appeared in G++ 3.4, and was the default through G++ 4.9. Version 3 corrects an error in mangling a constant address as a template argument. Version 4, which first appeared in G++ 4.5, implements a standard mangling for vector types. Version 5, which first appeared in G++ 4.6, corrects the mangling of attribute const/volatile on function pointer types, decltype of a plain decl, and use of a function parameter in the declaration of another parameter. Version 6, which first appeared in G++ 4.7, corrects the promotion behavior of C++11 scoped enums and the mangling of template argument packs, const/static_cast, prefix ++ and --, and a class scope function used as a template argument. Version 7, which first appeared in G++ 4.8, that treats nullptr_t as a builtin type and corrects the mangling of lambdas in default argument scope. Version 8, which first appeared in G++ 4.9, corrects the substitution behavior of function types with function-cv- qualifiers. Version 9, which first appeared in G++ 5.2, corrects the alignment of "nullptr_t". Version 10, which first appeared in G++ 6.1, adds mangling of attributes that affect type identity, such as ia32 calling convention attributes (e.g. stdcall). Version 11, which first appeared in G++ 7, corrects the mangling of sizeof... expressions and operator names. For multiple entities with the same name within a function, that are declared in different scopes, the mangling now changes starting with the twelfth occurrence. It also implies -fnew-inheriting-ctors. Version 12, which first appeared in G++ 8, corrects the calling conventions for empty classes on the x86_64 target and for classes with only deleted copy/move constructors. It accidentally changes the calling convention for classes with a deleted copy constructor and a trivial move constructor. Version 13, which first appeared in G++ 8.2, fixes the accidental change in version 12. Version 14, which first appeared in G++ 10, corrects the mangling of the nullptr expression. Version 15, which first appeared in G++ 10.3, corrects G++ 10 ABI tag regression. Version 16, which first appeared in G++ 11, changes the mangling of "__alignof__" to be distinct from that of "alignof", and dependent operator names. Version 17, which first appeared in G++ 12, fixes layout of classes that inherit from aggregate classes with default member initializers in C++14 and up. Version 18, which first appeard in G++ 13, fixes manglings of lambdas that have additional context. See also -Wabi. -fabi-compat-version=n On targets that support strong aliases, G++ works around mangling changes by creating an alias with the correct mangled name when defining a symbol with an incorrect mangled name. This switch specifies which ABI version to use for the alias. With -fabi-version=0 (the default), this defaults to 13 (GCC 8.2 compatibility). If another ABI version is explicitly selected, this defaults to 0. For compatibility with GCC versions 3.2 through 4.9, use -fabi-compat-version=2. If this option is not provided but -Wabi=n is, that version is used for compatibility aliases. If this option is provided along with -Wabi (without the version), the version from this option is used for the warning. -fno-access-control Turn off all access checking. This switch is mainly useful for working around bugs in the access control code. -faligned-new Enable support for C++17 "new" of types that require more alignment than "void* ::operator new(std::size_t)" provides. A numeric argument such as "-faligned-new=32" can be used to specify how much alignment (in bytes) is provided by that function, but few users will need to override the default of "alignof(std::max_align_t)". This flag is enabled by default for -std=c++17. -fchar8_t -fno-char8_t Enable support for "char8_t" as adopted for C++20. This includes the addition of a new "char8_t" fundamental type, changes to the types of UTF-8 string and character literals, new signatures for user-defined literals, associated standard library updates, and new "__cpp_char8_t" and "__cpp_lib_char8_t" feature test macros. This option enables functions to be overloaded for ordinary and UTF-8 strings: int f(const char *); // #1 int f(const char8_t *); // #2 int v1 = f("text"); // Calls #1 int v2 = f(u8"text"); // Calls #2 and introduces new signatures for user-defined literals: int operator""_udl1(char8_t); int v3 = u8'x'_udl1; int operator""_udl2(const char8_t*, std::size_t); int v4 = u8"text"_udl2; template<typename T, T...> int operator""_udl3(); int v5 = u8"text"_udl3; The change to the types of UTF-8 string and character literals introduces incompatibilities with ISO C++11 and later standards. For example, the following code is well-formed under ISO C++11, but is ill-formed when -fchar8_t is specified. const char *cp = u8"xx";// error: invalid conversion from // `const char8_t*' to `const char*' int f(const char*); auto v = f(u8"xx"); // error: invalid conversion from // `const char8_t*' to `const char*' std::string s{u8"xx"}; // error: no matching function for call to // `std::basic_string<char>::basic_string()' using namespace std::literals; s = u8"xx"s; // error: conversion from // `basic_string<char8_t>' to non-scalar // type `basic_string<char>' requested -fcheck-new Check that the pointer returned by "operator new" is non-null before attempting to modify the storage allocated. This check is normally unnecessary because the C++ standard specifies that "operator new" only returns 0 if it is declared "throw()", in which case the compiler always checks the return value even without this option. In all other cases, when "operator new" has a non-empty exception specification, memory exhaustion is signalled by throwing "std::bad_alloc". See also new (nothrow). -fconcepts -fconcepts-ts Enable support for the C++ Concepts feature for constraining template arguments. With -std=c++20 and above, Concepts are part of the language standard, so -fconcepts defaults to on. Some constructs that were allowed by the earlier C++ Extensions for Concepts Technical Specification, ISO 19217 (2015), but didn't make it into the standard, can additionally be enabled by -fconcepts-ts. -fconstexpr-depth=n Set the maximum nested evaluation depth for C++11 constexpr functions to n. A limit is needed to detect endless recursion during constant expression evaluation. The minimum specified by the standard is 512. -fconstexpr-cache-depth=n Set the maximum level of nested evaluation depth for C++11 constexpr functions that will be cached to n. This is a heuristic that trades off compilation speed (when the cache avoids repeated calculations) against memory consumption (when the cache grows very large from highly recursive evaluations). The default is 8. Very few users are likely to want to adjust it, but if your code does heavy constexpr calculations you might want to experiment to find which value works best for you. -fconstexpr-fp-except Annex F of the C standard specifies that IEC559 floating point exceptions encountered at compile time should not stop compilation. C++ compilers have historically not followed this guidance, instead treating floating point division by zero as non-constant even though it has a well defined value. This flag tells the compiler to give Annex F priority over other rules saying that a particular operation is undefined. constexpr float inf = 1./0.; // OK with -fconstexpr-fp-except -fconstexpr-loop-limit=n Set the maximum number of iterations for a loop in C++14 constexpr functions to n. A limit is needed to detect infinite loops during constant expression evaluation. The default is 262144 (1<<18). -fconstexpr-ops-limit=n Set the maximum number of operations during a single constexpr evaluation. Even when number of iterations of a single loop is limited with the above limit, if there are several nested loops and each of them has many iterations but still smaller than the above limit, or if in a body of some loop or even outside of a loop too many expressions need to be evaluated, the resulting constexpr evaluation might take too long. The default is 33554432 (1<<25). -fcontracts Enable experimental support for the C++ Contracts feature, as briefly added to and then removed from the C++20 working paper (N4820). The implementation also includes proposed enhancements from papers P1290, P1332, and P1429. This functionality is intended mostly for those interested in experimentation towards refining the feature to get it into shape for a future C++ standard. On violation of a checked contract, the violation handler is called. Users can replace the violation handler by defining void handle_contract_violation (const std::experimental::contract_violation&); There are different sets of additional flags that can be used together to specify which contracts will be checked and how, for N4820 contracts, P1332 contracts, or P1429 contracts; these sets cannot be used together. -fcontract-mode=[on|off] Control whether any contracts have any semantics at all. Defaults to on. -fcontract-assumption-mode=[on|off] [N4820] Control whether contracts with level axiom should have the assume semantic. Defaults to on. -fcontract-build-level=[off|default|audit] [N4820] Specify which level of contracts to generate checks for. Defaults to default. -fcontract-continuation-mode=[on|off] [N4820] Control whether to allow the program to continue executing after a contract violation. That is, do checked contracts have the maybe semantic described below rather than the never semantic. Defaults to off. -fcontract-role=<name>:<default>,<audit>,<axiom> [P1332] Specify the concrete semantics for each contract level of a particular contract role. -fcontract-semantic=[default|audit|axiom]:<semantic> [P1429] Specify the concrete semantic for a particular contract level. -fcontract-strict-declarations=[on|off] Control whether to reject adding contracts to a function after its first declaration. Defaults to off. The possible concrete semantics for that can be specified with -fcontract-role or -fcontract-semantic are: "ignore" This contract has no effect. "assume" This contract is treated like C++23 "[[assume]]". "check_never_continue" "never" "abort" This contract is checked. If it fails, the violation handler is called. If the handler returns, "std::terminate" is called. "check_maybe_continue" "maybe" This contract is checked. If it fails, the violation handler is called. If the handler returns, execution continues normally. -fcoroutines Enable support for the C++ coroutines extension (experimental). -fno-elide-constructors The C++ standard allows an implementation to omit creating a temporary that is only used to initialize another object of the same type. Specifying this option disables that optimization, and forces G++ to call the copy constructor in all cases. This option also causes G++ to call trivial member functions which otherwise would be expanded inline. In C++17, the compiler is required to omit these temporaries, but this option still affects trivial member functions. -fno-enforce-eh-specs Don't generate code to check for violation of exception specifications at run time. This option violates the C++ standard, but may be useful for reducing code size in production builds, much like defining "NDEBUG". This does not give user code permission to throw exceptions in violation of the exception specifications; the compiler still optimizes based on the specifications, so throwing an unexpected exception results in undefined behavior at run time. -fextern-tls-init -fno-extern-tls-init The C++11 and OpenMP standards allow "thread_local" and "threadprivate" variables to have dynamic (runtime) initialization. To support this, any use of such a variable goes through a wrapper function that performs any necessary initialization. When the use and definition of the variable are in the same translation unit, this overhead can be optimized away, but when the use is in a different translation unit there is significant overhead even if the variable doesn't actually need dynamic initialization. If the programmer can be sure that no use of the variable in a non- defining TU needs to trigger dynamic initialization (either because the variable is statically initialized, or a use of the variable in the defining TU will be executed before any uses in another TU), they can avoid this overhead with the -fno-extern-tls-init option. On targets that support symbol aliases, the default is -fextern-tls-init. On targets that do not support symbol aliases, the default is -fno-extern-tls-init. -ffold-simple-inlines -fno-fold-simple-inlines Permit the C++ frontend to fold calls to "std::move", "std::forward", "std::addressof" and "std::as_const". In contrast to inlining, this means no debug information will be generated for such calls. Since these functions are rarely interesting to debug, this flag is enabled by default unless -fno-inline is active. -fno-gnu-keywords Do not recognize "typeof" as a keyword, so that code can use this word as an identifier. You can use the keyword "__typeof__" instead. This option is implied by the strict ISO C++ dialects: -ansi, -std=c++98, -std=c++11, etc. -fimplicit-constexpr Make inline functions implicitly constexpr, if they satisfy the requirements for a constexpr function. This option can be used in C++14 mode or later. This can result in initialization changing from dynamic to static and other optimizations. -fno-implicit-templates Never emit code for non-inline templates that are instantiated implicitly (i.e. by use); only emit code for explicit instantiations. If you use this option, you must take care to structure your code to include all the necessary explicit instantiations to avoid getting undefined symbols at link time. -fno-implicit-inline-templates Don't emit code for implicit instantiations of inline templates, either. The default is to handle inlines differently so that compiles with and without optimization need the same set of explicit instantiations. -fno-implement-inlines To save space, do not emit out-of-line copies of inline functions controlled by "#pragma implementation". This causes linker errors if these functions are not inlined everywhere they are called. -fmodules-ts -fno-modules-ts Enable support for C++20 modules. The -fno-modules-ts is usually not needed, as that is the default. Even though this is a C++20 feature, it is not currently implicitly enabled by selecting that standard version. -fmodule-header -fmodule-header=user -fmodule-header=system Compile a header file to create an importable header unit. -fmodule-implicit-inline Member functions defined in their class definitions are not implicitly inline for modular code. This is different to traditional C++ behavior, for good reasons. However, it may result in a difficulty during code porting. This option makes such function definitions implicitly inline. It does however generate an ABI incompatibility, so you must use it everywhere or nowhere. (Such definitions outside of a named module remain implicitly inline, regardless.) -fno-module-lazy Disable lazy module importing and module mapper creation. -fmodule-mapper=[hostname]:port[?ident] -fmodule-mapper=|program[?ident] args... -fmodule-mapper==socket[?ident] -fmodule-mapper=<>[inout][?ident] -fmodule-mapper=<in>out[?ident] -fmodule-mapper=file[?ident] An oracle to query for module name to filename mappings. If unspecified the CXX_MODULE_MAPPER environment variable is used, and if that is unset, an in-process default is provided. -fmodule-only Only emit the Compiled Module Interface, inhibiting any object file. -fms-extensions Disable Wpedantic warnings about constructs used in MFC, such as implicit int and getting a pointer to member function via non- standard syntax. -fnew-inheriting-ctors Enable the P0136 adjustment to the semantics of C++11 constructor inheritance. This is part of C++17 but also considered to be a Defect Report against C++11 and C++14. This flag is enabled by default unless -fabi-version=10 or lower is specified. -fnew-ttp-matching Enable the P0522 resolution to Core issue 150, template template parameters and default arguments: this allows a template with default template arguments as an argument for a template template parameter with fewer template parameters. This flag is enabled by default for -std=c++17. -fno-nonansi-builtins Disable built-in declarations of functions that are not mandated by ANSI/ISO C. These include "ffs", "alloca", "_exit", "index", "bzero", "conjf", and other related functions. -fnothrow-opt Treat a "throw()" exception specification as if it were a "noexcept" specification to reduce or eliminate the text size overhead relative to a function with no exception specification. If the function has local variables of types with non-trivial destructors, the exception specification actually makes the function smaller because the EH cleanups for those variables can be optimized away. The semantic effect is that an exception thrown out of a function with such an exception specification results in a call to "terminate" rather than "unexpected". -fno-operator-names Do not treat the operator name keywords "and", "bitand", "bitor", "compl", "not", "or" and "xor" as synonyms as keywords. -fno-optional-diags Disable diagnostics that the standard says a compiler does not need to issue. Currently, the only such diagnostic issued by G++ is the one for a name having multiple meanings within a class. -fpermissive Downgrade some diagnostics about nonconformant code from errors to warnings. Thus, using -fpermissive allows some nonconforming code to compile. -fno-pretty-templates When an error message refers to a specialization of a function template, the compiler normally prints the signature of the template followed by the template arguments and any typedefs or typenames in the signature (e.g. "void f(T) [with T = int]" rather than "void f(int)") so that it's clear which template is involved. When an error message refers to a specialization of a class template, the compiler omits any template arguments that match the default template arguments for that template. If either of these behaviors make it harder to understand the error message rather than easier, you can use -fno-pretty-templates to disable them. -fno-rtti Disable generation of information about every class with virtual functions for use by the C++ run-time type identification features ("dynamic_cast" and "typeid"). If you don't use those parts of the language, you can save some space by using this flag. Note that exception handling uses the same information, but G++ generates it as needed. The "dynamic_cast" operator can still be used for casts that do not require run-time type information, i.e. casts to "void *" or to unambiguous base classes. Mixing code compiled with -frtti with that compiled with -fno-rtti may not work. For example, programs may fail to link if a class compiled with -fno-rtti is used as a base for a class compiled with -frtti. -fsized-deallocation Enable the built-in global declarations void operator delete (void *, std::size_t) noexcept; void operator delete[] (void *, std::size_t) noexcept; as introduced in C++14. This is useful for user-defined replacement deallocation functions that, for example, use the size of the object to make deallocation faster. Enabled by default under -std=c++14 and above. The flag -Wsized-deallocation warns about places that might want to add a definition. -fstrict-enums Allow the compiler to optimize using the assumption that a value of enumerated type can only be one of the values of the enumeration (as defined in the C++ standard; basically, a value that can be represented in the minimum number of bits needed to represent all the enumerators). This assumption may not be valid if the program uses a cast to convert an arbitrary integer value to the enumerated type. -fstrong-eval-order Evaluate member access, array subscripting, and shift expressions in left-to-right order, and evaluate assignment in right-to-left order, as adopted for C++17. Enabled by default with -std=c++17. -fstrong-eval-order=some enables just the ordering of member access and shift expressions, and is the default without -std=c++17. -ftemplate-backtrace-limit=n Set the maximum number of template instantiation notes for a single warning or error to n. The default value is 10. -ftemplate-depth=n Set the maximum instantiation depth for template classes to n. A limit on the template instantiation depth is needed to detect endless recursions during template class instantiation. ANSI/ISO C++ conforming programs must not rely on a maximum depth greater than 17 (changed to 1024 in C++11). The default value is 900, as the compiler can run out of stack space before hitting 1024 in some situations. -fno-threadsafe-statics Do not emit the extra code to use the routines specified in the C++ ABI for thread-safe initialization of local statics. You can use this option to reduce code size slightly in code that doesn't need to be thread-safe. -fuse-cxa-atexit Register destructors for objects with static storage duration with the "__cxa_atexit" function rather than the "atexit" function. This option is required for fully standards-compliant handling of static destructors, but only works if your C library supports "__cxa_atexit". -fno-use-cxa-get-exception-ptr Don't use the "__cxa_get_exception_ptr" runtime routine. This causes "std::uncaught_exception" to be incorrect, but is necessary if the runtime routine is not available. -fvisibility-inlines-hidden This switch declares that the user does not attempt to compare pointers to inline functions or methods where the addresses of the two functions are taken in different shared objects. The effect of this is that GCC may, effectively, mark inline methods with "__attribute__ ((visibility ("hidden")))" so that they do not appear in the export table of a DSO and do not require a PLT indirection when used within the DSO. Enabling this option can have a dramatic effect on load and link times of a DSO as it massively reduces the size of the dynamic export table when the library makes heavy use of templates. The behavior of this switch is not quite the same as marking the methods as hidden directly, because it does not affect static variables local to the function or cause the compiler to deduce that the function is defined in only one shared object. You may mark a method as having a visibility explicitly to negate the effect of the switch for that method. For example, if you do want to compare pointers to a particular inline method, you might mark it as having default visibility. Marking the enclosing class with explicit visibility has no effect. Explicitly instantiated inline methods are unaffected by this option as their linkage might otherwise cross a shared library boundary. -fvisibility-ms-compat This flag attempts to use visibility settings to make GCC's C++ linkage model compatible with that of Microsoft Visual Studio. The flag makes these changes to GCC's linkage model: 1. It sets the default visibility to "hidden", like -fvisibility=hidden. 2. Types, but not their members, are not hidden by default. 3. The One Definition Rule is relaxed for types without explicit visibility specifications that are defined in more than one shared object: those declarations are permitted if they are permitted when this option is not used. In new code it is better to use -fvisibility=hidden and export those classes that are intended to be externally visible. Unfortunately it is possible for code to rely, perhaps accidentally, on the Visual Studio behavior. Among the consequences of these changes are that static data members of the same type with the same name but defined in different shared objects are different, so changing one does not change the other; and that pointers to function members defined in different shared objects may not compare equal. When this flag is given, it is a violation of the ODR to define types with the same name differently. -fno-weak Do not use weak symbol support, even if it is provided by the linker. By default, G++ uses weak symbols if they are available. This option exists only for testing, and should not be used by end- users; it results in inferior code and has no benefits. This option may be removed in a future release of G++. -fext-numeric-literals (C++ and Objective-C++ only) Accept imaginary, fixed-point, or machine-defined literal number suffixes as GNU extensions. When this option is turned off these suffixes are treated as C++11 user-defined literal numeric suffixes. This is on by default for all pre-C++11 dialects and all GNU dialects: -std=c++98, -std=gnu++98, -std=gnu++11, -std=gnu++14. This option is off by default for ISO C++11 onwards (-std=c++11, ...). -nostdinc++ Do not search for header files in the standard directories specific to C++, but do still search the other standard directories. (This option is used when building the C++ library.) -flang-info-include-translate -flang-info-include-translate-not -flang-info-include-translate=header Inform of include translation events. The first will note accepted include translations, the second will note declined include translations. The header form will inform of include translations relating to that specific header. If header is of the form "user" or "<system>" it will be resolved to a specific user or system header using the include path. -flang-info-module-cmi -flang-info-module-cmi=module Inform of Compiled Module Interface pathnames. The first will note all read CMI pathnames. The module form will not reading a specific module's CMI. module may be a named module or a header- unit (the latter indicated by either being a pathname containing directory separators or enclosed in "<>" or ""). -stdlib=libstdc++,libc++ When G++ is configured to support this option, it allows specification of alternate C++ runtime libraries. Two options are available: libstdc++ (the default, native C++ runtime for G++) and libc++ which is the C++ runtime installed on some operating systems (e.g. Darwin versions from Darwin11 onwards). The option switches G++ to use the headers from the specified library and to emit "-lstdc++" or "-lc++" respectively, when a C++ runtime is required for linking. In addition, these warning options have meanings only for C++ programs: -Wabi-tag (C++ and Objective-C++ only) Warn when a type with an ABI tag is used in a context that does not have that ABI tag. See C++ Attributes for more information about ABI tags. -Wcomma-subscript (C++ and Objective-C++ only) Warn about uses of a comma expression within a subscripting expression. This usage was deprecated in C++20 and is going to be removed in C++23. However, a comma expression wrapped in "( )" is not deprecated. Example: void f(int *a, int b, int c) { a[b,c]; // deprecated in C++20, invalid in C++23 a[(b,c)]; // OK } In C++23 it is valid to have comma separated expressions in a subscript when an overloaded subscript operator is found and supports the right number and types of arguments. G++ will accept the formerly valid syntax for code that is not valid in C++23 but used to be valid but deprecated in C++20 with a pedantic warning that can be disabled with -Wno-comma-subscript. Enabled by default with -std=c++20 unless -Wno-deprecated, and with -std=c++23 regardless of -Wno-deprecated. -Wctad-maybe-unsupported (C++ and Objective-C++ only) Warn when performing class template argument deduction (CTAD) on a type with no explicitly written deduction guides. This warning will point out cases where CTAD succeeded only because the compiler synthesized the implicit deduction guides, which might not be what the programmer intended. Certain style guides allow CTAD only on types that specifically "opt-in"; i.e., on types that are designed to support CTAD. This warning can be suppressed with the following pattern: struct allow_ctad_t; // any name works template <typename T> struct S { S(T) { } }; // Guide with incomplete parameter type will never be considered. S(allow_ctad_t) -> S<void>; -Wctor-dtor-privacy (C++ and Objective-C++ only) Warn when a class seems unusable because all the constructors or destructors in that class are private, and it has neither friends nor public static member functions. Also warn if there are no non- private methods, and there's at least one private member function that isn't a constructor or destructor. -Wdangling-reference (C++ and Objective-C++ only) Warn when a reference is bound to a temporary whose lifetime has ended. For example: int n = 1; const int& r = std::max(n - 1, n + 1); // r is dangling In the example above, two temporaries are created, one for each argument, and a reference to one of the temporaries is returned. However, both temporaries are destroyed at the end of the full expression, so the reference "r" is dangling. This warning also detects dangling references in member initializer lists: const int& f(const int& i) { return i; } struct S { const int &r; // r is dangling S() : r(f(10)) { } }; Member functions are checked as well, but only their object argument: struct S { const S& self () { return *this; } }; const S& s = S().self(); // s is dangling Certain functions are safe in this respect, for example "std::use_facet": they take and return a reference, but they don't return one of its arguments, which can fool the warning. Such functions can be excluded from the warning by wrapping them in a "#pragma": #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wdangling-reference" const T& foo (const T&) { ... } #pragma GCC diagnostic pop -Wdangling-reference also warns about code like auto p = std::minmax(1, 2); where "std::minmax" returns "std::pair<const int&, const int&>", and both references dangle after the end of the full expression that contains the call to "std::minmax". This warning is enabled by -Wextra. -Wdelete-non-virtual-dtor (C++ and Objective-C++ only) Warn when "delete" is used to destroy an instance of a class that has virtual functions and non-virtual destructor. It is unsafe to delete an instance of a derived class through a pointer to a base class if the base class does not have a virtual destructor. This warning is enabled by -Wall. -Wdeprecated-copy (C++ and Objective-C++ only) Warn that the implicit declaration of a copy constructor or copy assignment operator is deprecated if the class has a user-provided copy constructor or copy assignment operator, in C++11 and up. This warning is enabled by -Wextra. With -Wdeprecated-copy-dtor, also deprecate if the class has a user-provided destructor. -Wno-deprecated-enum-enum-conversion (C++ and Objective-C++ only) Disable the warning about the case when the usual arithmetic conversions are applied on operands where one is of enumeration type and the other is of a different enumeration type. This conversion was deprecated in C++20. For example: enum E1 { e }; enum E2 { f }; int k = f - e; -Wdeprecated-enum-enum-conversion is enabled by default with -std=c++20. In pre-C++20 dialects, this warning can be enabled by -Wenum-conversion. -Wno-deprecated-enum-float-conversion (C++ and Objective-C++ only) Disable the warning about the case when the usual arithmetic conversions are applied on operands where one is of enumeration type and the other is of a floating-point type. This conversion was deprecated in C++20. For example: enum E1 { e }; enum E2 { f }; bool b = e <= 3.7; -Wdeprecated-enum-float-conversion is enabled by default with -std=c++20. In pre-C++20 dialects, this warning can be enabled by -Wenum-conversion. -Wno-init-list-lifetime (C++ and Objective-C++ only) Do not warn about uses of "std::initializer_list" that are likely to result in dangling pointers. Since the underlying array for an "initializer_list" is handled like a normal C++ temporary object, it is easy to inadvertently keep a pointer to the array past the end of the array's lifetime. For example: * If a function returns a temporary "initializer_list", or a local "initializer_list" variable, the array's lifetime ends at the end of the return statement, so the value returned has a dangling pointer. * If a new-expression creates an "initializer_list", the array only lives until the end of the enclosing full-expression, so the "initializer_list" in the heap has a dangling pointer. * When an "initializer_list" variable is assigned from a brace- enclosed initializer list, the temporary array created for the right side of the assignment only lives until the end of the full-expression, so at the next statement the "initializer_list" variable has a dangling pointer. // li's initial underlying array lives as long as li std::initializer_list<int> li = { 1,2,3 }; // assignment changes li to point to a temporary array li = { 4, 5 }; // now the temporary is gone and li has a dangling pointer int i = li.begin()[0] // undefined behavior * When a list constructor stores the "begin" pointer from the "initializer_list" argument, this doesn't extend the lifetime of the array, so if a class variable is constructed from a temporary "initializer_list", the pointer is left dangling by the end of the variable declaration statement. -Winvalid-constexpr Warn when a function never produces a constant expression. In C++20 and earlier, for every "constexpr" function and function template, there must be at least one set of function arguments in at least one instantiation such that an invocation of the function or constructor could be an evaluated subexpression of a core constant expression. C++23 removed this restriction, so it's possible to have a function or a function template marked "constexpr" for which no invocation satisfies the requirements of a core constant expression. This warning is enabled as a pedantic warning by default in C++20 and earlier. In C++23, -Winvalid-constexpr can be turned on, in which case it will be an ordinary warning. For example: void f (int& i); constexpr void g (int& i) { // Warns by default in C++20, in C++23 only with -Winvalid-constexpr. f(i); } -Winvalid-imported-macros Verify all imported macro definitions are valid at the end of compilation. This is not enabled by default, as it requires additional processing to determine. It may be useful when preparing sets of header-units to ensure consistent macros. -Wno-literal-suffix (C++ and Objective-C++ only) Do not warn when a string or character literal is followed by a ud- suffix which does not begin with an underscore. As a conforming extension, GCC treats such suffixes as separate preprocessing tokens in order to maintain backwards compatibility with code that uses formatting macros from "<inttypes.h>". For example: #define __STDC_FORMAT_MACROS #include <inttypes.h> #include <stdio.h> int main() { int64_t i64 = 123; printf("My int64: %" PRId64"\n", i64); } In this case, "PRId64" is treated as a separate preprocessing token. This option also controls warnings when a user-defined literal operator is declared with a literal suffix identifier that doesn't begin with an underscore. Literal suffix identifiers that don't begin with an underscore are reserved for future standardization. These warnings are enabled by default. -Wno-narrowing (C++ and Objective-C++ only) For C++11 and later standards, narrowing conversions are diagnosed by default, as required by the standard. A narrowing conversion from a constant produces an error, and a narrowing conversion from a non-constant produces a warning, but -Wno-narrowing suppresses the diagnostic. Note that this does not affect the meaning of well-formed code; narrowing conversions are still considered ill- formed in SFINAE contexts. With -Wnarrowing in C++98, warn when a narrowing conversion prohibited by C++11 occurs within { }, e.g. int i = { 2.2 }; // error: narrowing from double to int This flag is included in -Wall and -Wc++11-compat. -Wnoexcept (C++ and Objective-C++ only) Warn when a noexcept-expression evaluates to false because of a call to a function that does not have a non-throwing exception specification (i.e. "throw()" or "noexcept") but is known by the compiler to never throw an exception. -Wnoexcept-type (C++ and Objective-C++ only) Warn if the C++17 feature making "noexcept" part of a function type changes the mangled name of a symbol relative to C++14. Enabled by -Wabi and -Wc++17-compat. As an example: template <class T> void f(T t) { t(); }; void g() noexcept; void h() { f(g); } In C++14, "f" calls "f<void(*)()>", but in C++17 it calls "f<void(*)()noexcept>". -Wclass-memaccess (C++ and Objective-C++ only) Warn when the destination of a call to a raw memory function such as "memset" or "memcpy" is an object of class type, and when writing into such an object might bypass the class non-trivial or deleted constructor or copy assignment, violate const-correctness or encapsulation, or corrupt virtual table pointers. Modifying the representation of such objects may violate invariants maintained by member functions of the class. For example, the call to "memset" below is undefined because it modifies a non-trivial class object and is, therefore, diagnosed. The safe way to either initialize or clear the storage of objects of such types is by using the appropriate constructor or assignment operator, if one is available. std::string str = "abc"; memset (&str, 0, sizeof str); The -Wclass-memaccess option is enabled by -Wall. Explicitly casting the pointer to the class object to "void *" or to a type that can be safely accessed by the raw memory function suppresses the warning. -Wnon-virtual-dtor (C++ and Objective-C++ only) Warn when a class has virtual functions and an accessible non- virtual destructor itself or in an accessible polymorphic base class, in which case it is possible but unsafe to delete an instance of a derived class through a pointer to the class itself or base class. This warning is automatically enabled if -Weffc++ is specified. The -Wdelete-non-virtual-dtor option (enabled by -Wall) should be preferred because it warns about the unsafe cases without false positives. -Wregister (C++ and Objective-C++ only) Warn on uses of the "register" storage class specifier, except when it is part of the GNU Explicit Register Variables extension. The use of the "register" keyword as storage class specifier has been deprecated in C++11 and removed in C++17. Enabled by default with -std=c++17. -Wreorder (C++ and Objective-C++ only) Warn when the order of member initializers given in the code does not match the order in which they must be executed. For instance: struct A { int i; int j; A(): j (0), i (1) { } }; The compiler rearranges the member initializers for "i" and "j" to match the declaration order of the members, emitting a warning to that effect. This warning is enabled by -Wall. -Wno-pessimizing-move (C++ and Objective-C++ only) This warning warns when a call to "std::move" prevents copy elision. A typical scenario when copy elision can occur is when returning in a function with a class return type, when the expression being returned is the name of a non-volatile automatic object, and is not a function parameter, and has the same type as the function return type. struct T { ... }; T fn() { T t; ... return std::move (t); } But in this example, the "std::move" call prevents copy elision. This warning is enabled by -Wall. -Wno-redundant-move (C++ and Objective-C++ only) This warning warns about redundant calls to "std::move"; that is, when a move operation would have been performed even without the "std::move" call. This happens because the compiler is forced to treat the object as if it were an rvalue in certain situations such as returning a local variable, where copy elision isn't applicable. Consider: struct T { ... }; T fn(T t) { ... return std::move (t); } Here, the "std::move" call is redundant. Because G++ implements Core Issue 1579, another example is: struct T { // convertible to U ... }; struct U { ... }; U fn() { T t; ... return std::move (t); } In this example, copy elision isn't applicable because the type of the expression being returned and the function return type differ, yet G++ treats the return value as if it were designated by an rvalue. This warning is enabled by -Wextra. -Wrange-loop-construct (C++ and Objective-C++ only) This warning warns when a C++ range-based for-loop is creating an unnecessary copy. This can happen when the range declaration is not a reference, but probably should be. For example: struct S { char arr[128]; }; void fn () { S arr[5]; for (const auto x : arr) { ... } } It does not warn when the type being copied is a trivially-copyable type whose size is less than 64 bytes. This warning also warns when a loop variable in a range-based for- loop is initialized with a value of a different type resulting in a copy. For example: void fn() { int arr[10]; for (const double &x : arr) { ... } } In the example above, in every iteration of the loop a temporary value of type "double" is created and destroyed, to which the reference "const double &" is bound. This warning is enabled by -Wall. -Wredundant-tags (C++ and Objective-C++ only) Warn about redundant class-key and enum-key in references to class types and enumerated types in contexts where the key can be eliminated without causing an ambiguity. For example: struct foo; struct foo *p; // warn that keyword struct can be eliminated On the other hand, in this example there is no warning: struct foo; void foo (); // "hides" struct foo void bar (struct foo&); // no warning, keyword struct is necessary -Wno-subobject-linkage (C++ and Objective-C++ only) Do not warn if a class type has a base or a field whose type uses the anonymous namespace or depends on a type with no linkage. If a type A depends on a type B with no or internal linkage, defining it in multiple translation units would be an ODR violation because the meaning of B is different in each translation unit. If A only appears in a single translation unit, the best way to silence the warning is to give it internal linkage by putting it in an anonymous namespace as well. The compiler doesn't give this warning for types defined in the main .C file, as those are unlikely to have multiple definitions. -Wsubobject-linkage is enabled by default. -Weffc++ (C++ and Objective-C++ only) Warn about violations of the following style guidelines from Scott Meyers' Effective C++ series of books: * Define a copy constructor and an assignment operator for classes with dynamically-allocated memory. * Prefer initialization to assignment in constructors. * Have "operator=" return a reference to *this. * Don't try to return a reference when you must return an object. * Distinguish between prefix and postfix forms of increment and decrement operators. * Never overload "&&", "||", or ",". This option also enables -Wnon-virtual-dtor, which is also one of the effective C++ recommendations. However, the check is extended to warn about the lack of virtual destructor in accessible non- polymorphic bases classes too. When selecting this option, be aware that the standard library headers do not obey all of these guidelines; use grep -v to filter out those warnings. -Wno-exceptions (C++ and Objective-C++ only) Disable the warning about the case when an exception handler is shadowed by another handler, which can point out a wrong ordering of exception handlers. -Wstrict-null-sentinel (C++ and Objective-C++ only) Warn about the use of an uncasted "NULL" as sentinel. When compiling only with GCC this is a valid sentinel, as "NULL" is defined to "__null". Although it is a null pointer constant rather than a null pointer, it is guaranteed to be of the same size as a pointer. But this use is not portable across different compilers. -Wno-non-template-friend (C++ and Objective-C++ only) Disable warnings when non-template friend functions are declared within a template. In very old versions of GCC that predate implementation of the ISO standard, declarations such as friend int foo(int), where the name of the friend is an unqualified-id, could be interpreted as a particular specialization of a template function; the warning exists to diagnose compatibility problems, and is enabled by default. -Wold-style-cast (C++ and Objective-C++ only) Warn if an old-style (C-style) cast to a non-void type is used within a C++ program. The new-style casts ("dynamic_cast", "static_cast", "reinterpret_cast", and "const_cast") are less vulnerable to unintended effects and much easier to search for. -Woverloaded-virtual (C++ and Objective-C++ only) -Woverloaded-virtual=n Warn when a function declaration hides virtual functions from a base class. For example, in: struct A { virtual void f(); }; struct B: public A { void f(int); // does not override }; the "A" class version of "f" is hidden in "B", and code like: B* b; b->f(); fails to compile. In cases where the different signatures are not an accident, the simplest solution is to add a using-declaration to the derived class to un-hide the base function, e.g. add "using A::f;" to "B". The optional level suffix controls the behavior when all the declarations in the derived class override virtual functions in the base class, even if not all of the base functions are overridden: struct C { virtual void f(); virtual void f(int); }; struct D: public C { void f(int); // does override } This pattern is less likely to be a mistake; if D is only used virtually, the user might have decided that the base class semantics for some of the overloads are fine. At level 1, this case does not warn; at level 2, it does. -Woverloaded-virtual by itself selects level 2. Level 1 is included in -Wall. -Wno-pmf-conversions (C++ and Objective-C++ only) Disable the diagnostic for converting a bound pointer to member function to a plain pointer. -Wsign-promo (C++ and Objective-C++ only) Warn when overload resolution chooses a promotion from unsigned or enumerated type to a signed type, over a conversion to an unsigned type of the same size. Previous versions of G++ tried to preserve unsignedness, but the standard mandates the current behavior. -Wtemplates (C++ and Objective-C++ only) Warn when a primary template declaration is encountered. Some coding rules disallow templates, and this may be used to enforce that rule. The warning is inactive inside a system header file, such as the STL, so one can still use the STL. One may also instantiate or specialize templates. -Wmismatched-new-delete (C++ and Objective-C++ only) Warn for mismatches between calls to "operator new" or "operator delete" and the corresponding call to the allocation or deallocation function. This includes invocations of C++ "operator delete" with pointers returned from either mismatched forms of "operator new", or from other functions that allocate objects for which the "operator delete" isn't a suitable deallocator, as well as calls to other deallocation functions with pointers returned from "operator new" for which the deallocation function isn't suitable. For example, the "delete" expression in the function below is diagnosed because it doesn't match the array form of the "new" expression the pointer argument was returned from. Similarly, the call to "free" is also diagnosed. void f () { int *a = new int[n]; delete a; // warning: mismatch in array forms of expressions char *p = new char[n]; free (p); // warning: mismatch between new and free } The related option -Wmismatched-dealloc diagnoses mismatches involving allocation and deallocation functions other than "operator new" and "operator delete". -Wmismatched-new-delete is included in -Wall. -Wmismatched-tags (C++ and Objective-C++ only) Warn for declarations of structs, classes, and class templates and their specializations with a class-key that does not match either the definition or the first declaration if no definition is provided. For example, the declaration of "struct Object" in the argument list of "draw" triggers the warning. To avoid it, either remove the redundant class-key "struct" or replace it with "class" to match its definition. class Object { public: virtual ~Object () = 0; }; void draw (struct Object*); It is not wrong to declare a class with the class-key "struct" as the example above shows. The -Wmismatched-tags option is intended to help achieve a consistent style of class declarations. In code that is intended to be portable to Windows-based compilers the warning helps prevent unresolved references due to the difference in the mangling of symbols declared with different class-keys. The option can be used either on its own or in conjunction with -Wredundant-tags. -Wmultiple-inheritance (C++ and Objective-C++ only) Warn when a class is defined with multiple direct base classes. Some coding rules disallow multiple inheritance, and this may be used to enforce that rule. The warning is inactive inside a system header file, such as the STL, so one can still use the STL. One may also define classes that indirectly use multiple inheritance. -Wvirtual-inheritance Warn when a class is defined with a virtual direct base class. Some coding rules disallow multiple inheritance, and this may be used to enforce that rule. The warning is inactive inside a system header file, such as the STL, so one can still use the STL. One may also define classes that indirectly use virtual inheritance. -Wno-virtual-move-assign Suppress warnings about inheriting from a virtual base with a non- trivial C++11 move assignment operator. This is dangerous because if the virtual base is reachable along more than one path, it is moved multiple times, which can mean both objects end up in the moved-from state. If the move assignment operator is written to avoid moving from a moved-from object, this warning can be disabled. -Wnamespaces Warn when a namespace definition is opened. Some coding rules disallow namespaces, and this may be used to enforce that rule. The warning is inactive inside a system header file, such as the STL, so one can still use the STL. One may also use using directives and qualified names. -Wno-terminate (C++ and Objective-C++ only) Disable the warning about a throw-expression that will immediately result in a call to "terminate". -Wno-vexing-parse (C++ and Objective-C++ only) Warn about the most vexing parse syntactic ambiguity. This warns about the cases when a declaration looks like a variable definition, but the C++ language requires it to be interpreted as a function declaration. For instance: void f(double a) { int i(); // extern int i (void); int n(int(a)); // extern int n (int); } Another example: struct S { S(int); }; void f(double a) { S x(int(a)); // extern struct S x (int); S y(int()); // extern struct S y (int (*) (void)); S z(); // extern struct S z (void); } The warning will suggest options how to deal with such an ambiguity; e.g., it can suggest removing the parentheses or using braces instead. This warning is enabled by default. -Wno-class-conversion (C++ and Objective-C++ only) Do not warn when a conversion function converts an object to the same type, to a base class of that type, or to void; such a conversion function will never be called. -Wvolatile (C++ and Objective-C++ only) Warn about deprecated uses of the "volatile" qualifier. This includes postfix and prefix "++" and "--" expressions of "volatile"-qualified types, using simple assignments where the left operand is a "volatile"-qualified non-class type for their value, compound assignments where the left operand is a "volatile"-qualified non-class type, "volatile"-qualified function return type, "volatile"-qualified parameter type, and structured bindings of a "volatile"-qualified type. This usage was deprecated in C++20. Enabled by default with -std=c++20. -Wzero-as-null-pointer-constant (C++ and Objective-C++ only) Warn when a literal 0 is used as null pointer constant. This can be useful to facilitate the conversion to "nullptr" in C++11. -Waligned-new Warn about a new-expression of a type that requires greater alignment than the "alignof(std::max_align_t)" but uses an allocation function without an explicit alignment parameter. This option is enabled by -Wall. Normally this only warns about global allocation functions, but -Waligned-new=all also warns about class member allocation functions. -Wno-placement-new -Wplacement-new=n Warn about placement new expressions with undefined behavior, such as constructing an object in a buffer that is smaller than the type of the object. For example, the placement new expression below is diagnosed because it attempts to construct an array of 64 integers in a buffer only 64 bytes large. char buf [64]; new (buf) int[64]; This warning is enabled by default. -Wplacement-new=1 This is the default warning level of -Wplacement-new. At this level the warning is not issued for some strictly undefined constructs that GCC allows as extensions for compatibility with legacy code. For example, the following "new" expression is not diagnosed at this level even though it has undefined behavior according to the C++ standard because it writes past the end of the one-element array. struct S { int n, a[1]; }; S *s = (S *)malloc (sizeof *s + 31 * sizeof s->a[0]); new (s->a)int [32](); -Wplacement-new=2 At this level, in addition to diagnosing all the same constructs as at level 1, a diagnostic is also issued for placement new expressions that construct an object in the last member of structure whose type is an array of a single element and whose size is less than the size of the object being constructed. While the previous example would be diagnosed, the following construct makes use of the flexible member array extension to avoid the warning at level 2. struct S { int n, a[]; }; S *s = (S *)malloc (sizeof *s + 32 * sizeof s->a[0]); new (s->a)int [32](); -Wcatch-value -Wcatch-value=n (C++ and Objective-C++ only) Warn about catch handlers that do not catch via reference. With -Wcatch-value=1 (or -Wcatch-value for short) warn about polymorphic class types that are caught by value. With -Wcatch-value=2 warn about all class types that are caught by value. With -Wcatch-value=3 warn about all types that are not caught by reference. -Wcatch-value is enabled by -Wall. -Wconditionally-supported (C++ and Objective-C++ only) Warn for conditionally-supported (C++11 [intro.defs]) constructs. -Wno-delete-incomplete (C++ and Objective-C++ only) Do not warn when deleting a pointer to incomplete type, which may cause undefined behavior at runtime. This warning is enabled by default. -Wextra-semi (C++, Objective-C++ only) Warn about redundant semicolons after in-class function definitions. -Wno-inaccessible-base (C++, Objective-C++ only) This option controls warnings when a base class is inaccessible in a class derived from it due to ambiguity. The warning is enabled by default. Note that the warning for ambiguous virtual bases is enabled by the -Wextra option. struct A { int a; }; struct B : A { }; struct C : B, A { }; -Wno-inherited-variadic-ctor Suppress warnings about use of C++11 inheriting constructors when the base class inherited from has a C variadic constructor; the warning is on by default because the ellipsis is not inherited. -Wno-invalid-offsetof (C++ and Objective-C++ only) Suppress warnings from applying the "offsetof" macro to a non-POD type. According to the 2014 ISO C++ standard, applying "offsetof" to a non-standard-layout type is undefined. In existing C++ implementations, however, "offsetof" typically gives meaningful results. This flag is for users who are aware that they are writing nonportable code and who have deliberately chosen to ignore the warning about it. The restrictions on "offsetof" may be relaxed in a future version of the C++ standard. -Wsized-deallocation (C++ and Objective-C++ only) Warn about a definition of an unsized deallocation function void operator delete (void *) noexcept; void operator delete[] (void *) noexcept; without a definition of the corresponding sized deallocation function void operator delete (void *, std::size_t) noexcept; void operator delete[] (void *, std::size_t) noexcept; or vice versa. Enabled by -Wextra along with -fsized-deallocation. -Wsuggest-final-types Warn about types with virtual methods where code quality would be improved if the type were declared with the C++11 "final" specifier, or, if possible, declared in an anonymous namespace. This allows GCC to more aggressively devirtualize the polymorphic calls. This warning is more effective with link-time optimization, where the information about the class hierarchy graph is more complete. -Wsuggest-final-methods Warn about virtual methods where code quality would be improved if the method were declared with the C++11 "final" specifier, or, if possible, its type were declared in an anonymous namespace or with the "final" specifier. This warning is more effective with link- time optimization, where the information about the class hierarchy graph is more complete. It is recommended to first consider suggestions of -Wsuggest-final-types and then rebuild with new annotations. -Wsuggest-override Warn about overriding virtual functions that are not marked with the "override" keyword. -Wuse-after-free -Wuse-after-free=n Warn about uses of pointers to dynamically allocated objects that have been rendered indeterminate by a call to a deallocation function. The warning is enabled at all optimization levels but may yield different results with optimization than without. -Wuse-after-free=1 At level 1 the warning attempts to diagnose only unconditional uses of pointers made indeterminate by a deallocation call or a successful call to "realloc", regardless of whether or not the call resulted in an actual reallocatio of memory. This includes double-"free" calls as well as uses in arithmetic and relational expressions. Although undefined, uses of indeterminate pointers in equality (or inequality) expressions are not diagnosed at this level. -Wuse-after-free=2 At level 2, in addition to unconditional uses, the warning also diagnoses conditional uses of pointers made indeterminate by a deallocation call. As at level 2, uses in equality (or inequality) expressions are not diagnosed. For example, the second call to "free" in the following function is diagnosed at this level: struct A { int refcount; void *data; }; void release (struct A *p) { int refcount = --p->refcount; free (p); if (refcount == 0) free (p->data); // warning: p may be used after free } -Wuse-after-free=3 At level 3, the warning also diagnoses uses of indeterminate pointers in equality expressions. All uses of indeterminate pointers are undefined but equality tests sometimes appear after calls to "realloc" as an attempt to determine whether the call resulted in relocating the object to a different address. They are diagnosed at a separate level to aid legacy code gradually transition to safe alternatives. For example, the equality test in the function below is diagnosed at this level: void adjust_pointers (int**, int); void grow (int **p, int n) { int **q = (int**)realloc (p, n *= 2); if (q == p) return; adjust_pointers ((int**)q, n); } To avoid the warning at this level, store offsets into allocated memory instead of pointers. This approach obviates needing to adjust the stored pointers after reallocation. -Wuse-after-free=2 is included in -Wall. -Wuseless-cast (C++ and Objective-C++ only) Warn when an expression is cast to its own type. This warning does not occur when a class object is converted to a non-reference type as that is a way to create a temporary: struct S { }; void g (S&&); void f (S&& arg) { g (S(arg)); // make arg prvalue so that it can bind to S&& } -Wno-conversion-null (C++ and Objective-C++ only) Do not warn for conversions between "NULL" and non-pointer types. -Wconversion-null is enabled by default. Options Controlling Objective-C and Objective-C++ Dialects (NOTE: This manual does not describe the Objective-C and Objective-C++ languages themselves. This section describes the command-line options that are only meaningful for Objective-C and Objective-C++ programs. You can also use most of the language-independent GNU compiler options. For example, you might compile a file some_class.m like this: gcc -g -fgnu-runtime -O -c some_class.m In this example, -fgnu-runtime is an option meant only for Objective-C and Objective-C++ programs; you can use the other options with any language supported by GCC. Note that since Objective-C is an extension of the C language, Objective-C compilations may also use options specific to the C front- end (e.g., -Wtraditional). Similarly, Objective-C++ compilations may use C++-specific options (e.g., -Wabi). Here is a list of options that are only for compiling Objective-C and Objective-C++ programs: -fconstant-string-class=class-name Use class-name as the name of the class to instantiate for each literal string specified with the syntax "@"..."". The default class name is "NXConstantString" if the GNU runtime is being used, and "NSConstantString" if the NeXT runtime is being used (see below). On Darwin (macOS, MacOS X) platforms, the -fconstant-cfstrings option, if also present, overrides the -fconstant-string-class setting and cause "@"..."" literals to be laid out as constant CoreFoundation strings. Note that -fconstant-cfstrings is an alias for the target-specific -mconstant-cfstrings equivalent. -fgnu-runtime Generate object code compatible with the standard GNU Objective-C runtime. This is the default for most types of systems. -fnext-runtime Generate output compatible with the NeXT runtime. This is the default for NeXT-based systems, including Darwin and Mac OS X. The macro "__NEXT_RUNTIME__" is predefined if (and only if) this option is used. -fno-nil-receivers Assume that all Objective-C message dispatches ("[receiver message:arg]") in this translation unit ensure that the receiver is not "nil". This allows for more efficient entry points in the runtime to be used. This option is only available in conjunction with the NeXT runtime and ABI version 0 or 1. -fobjc-abi-version=n Use version n of the Objective-C ABI for the selected runtime. This option is currently supported only for the NeXT runtime. In that case, Version 0 is the traditional (32-bit) ABI without support for properties and other Objective-C 2.0 additions. Version 1 is the traditional (32-bit) ABI with support for properties and other Objective-C 2.0 additions. Version 2 is the modern (64-bit) ABI. If nothing is specified, the default is Version 0 on 32-bit target machines, and Version 2 on 64-bit target machines. -fobjc-call-cxx-cdtors For each Objective-C class, check if any of its instance variables is a C++ object with a non-trivial default constructor. If so, synthesize a special "- (id) .cxx_construct" instance method which runs non-trivial default constructors on any such instance variables, in order, and then return "self". Similarly, check if any instance variable is a C++ object with a non-trivial destructor, and if so, synthesize a special "- (void) .cxx_destruct" method which runs all such default destructors, in reverse order. The "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods thusly generated only operate on instance variables declared in the current Objective-C class, and not those inherited from superclasses. It is the responsibility of the Objective-C runtime to invoke all such methods in an object's inheritance hierarchy. The "- (id) .cxx_construct" methods are invoked by the runtime immediately after a new object instance is allocated; the "- (void) .cxx_destruct" methods are invoked immediately before the runtime deallocates an object instance. As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has support for invoking the "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods. -fobjc-direct-dispatch Allow fast jumps to the message dispatcher. On Darwin this is accomplished via the comm page. -fobjc-exceptions Enable syntactic support for structured exception handling in Objective-C, similar to what is offered by C++. This option is required to use the Objective-C keywords @try, @throw, @catch, @finally and @synchronized. This option is available with both the GNU runtime and the NeXT runtime (but not available in conjunction with the NeXT runtime on Mac OS X 10.2 and earlier). -fobjc-gc Enable garbage collection (GC) in Objective-C and Objective-C++ programs. This option is only available with the NeXT runtime; the GNU runtime has a different garbage collection implementation that does not require special compiler flags. -fobjc-nilcheck For the NeXT runtime with version 2 of the ABI, check for a nil receiver in method invocations before doing the actual method call. This is the default and can be disabled using -fno-objc-nilcheck. Class methods and super calls are never checked for nil in this way no matter what this flag is set to. Currently this flag does nothing when the GNU runtime, or an older version of the NeXT runtime ABI, is used. -fobjc-std=objc1 Conform to the language syntax of Objective-C 1.0, the language recognized by GCC 4.0. This only affects the Objective-C additions to the C/C++ language; it does not affect conformance to C/C++ standards, which is controlled by the separate C/C++ dialect option flags. When this option is used with the Objective-C or Objective-C++ compiler, any Objective-C syntax that is not recognized by GCC 4.0 is rejected. This is useful if you need to make sure that your Objective-C code can be compiled with older versions of GCC. -freplace-objc-classes Emit a special marker instructing ld(1) not to statically link in the resulting object file, and allow dyld(1) to load it in at run time instead. This is used in conjunction with the Fix-and- Continue debugging mode, where the object file in question may be recompiled and dynamically reloaded in the course of program execution, without the need to restart the program itself. Currently, Fix-and-Continue functionality is only available in conjunction with the NeXT runtime on Mac OS X 10.3 and later. -fzero-link When compiling for the NeXT runtime, the compiler ordinarily replaces calls to "objc_getClass("...")" (when the name of the class is known at compile time) with static class references that get initialized at load time, which improves run-time performance. Specifying the -fzero-link flag suppresses this behavior and causes calls to "objc_getClass("...")" to be retained. This is useful in Zero-Link debugging mode, since it allows for individual class implementations to be modified during program execution. The GNU runtime currently always retains calls to "objc_get_class("...")" regardless of command-line options. -fno-local-ivars By default instance variables in Objective-C can be accessed as if they were local variables from within the methods of the class they're declared in. This can lead to shadowing between instance variables and other variables declared either locally inside a class method or globally with the same name. Specifying the -fno-local-ivars flag disables this behavior thus avoiding variable shadowing issues. -fivar-visibility=[public|protected|private|package] Set the default instance variable visibility to the specified option so that instance variables declared outside the scope of any access modifier directives default to the specified visibility. -gen-decls Dump interface declarations for all classes seen in the source file to a file named sourcename.decl. -Wassign-intercept (Objective-C and Objective-C++ only) Warn whenever an Objective-C assignment is being intercepted by the garbage collector. -Wno-property-assign-default (Objective-C and Objective-C++ only) Do not warn if a property for an Objective-C object has no assign semantics specified. -Wno-protocol (Objective-C and Objective-C++ only) If a class is declared to implement a protocol, a warning is issued for every method in the protocol that is not implemented by the class. The default behavior is to issue a warning for every method not explicitly implemented in the class, even if a method implementation is inherited from the superclass. If you use the -Wno-protocol option, then methods inherited from the superclass are considered to be implemented, and no warning is issued for them. -Wobjc-root-class (Objective-C and Objective-C++ only) Warn if a class interface lacks a superclass. Most classes will inherit from "NSObject" (or "Object") for example. When declaring classes intended to be root classes, the warning can be suppressed by marking their interfaces with "__attribute__((objc_root_class))". -Wselector (Objective-C and Objective-C++ only) Warn if multiple methods of different types for the same selector are found during compilation. The check is performed on the list of methods in the final stage of compilation. Additionally, a check is performed for each selector appearing in a "@selector(...)" expression, and a corresponding method for that selector has been found during compilation. Because these checks scan the method table only at the end of compilation, these warnings are not produced if the final stage of compilation is not reached, for example because an error is found during compilation, or because the -fsyntax-only option is being used. -Wstrict-selector-match (Objective-C and Objective-C++ only) Warn if multiple methods with differing argument and/or return types are found for a given selector when attempting to send a message using this selector to a receiver of type "id" or "Class". When this flag is off (which is the default behavior), the compiler omits such warnings if any differences found are confined to types that share the same size and alignment. -Wundeclared-selector (Objective-C and Objective-C++ only) Warn if a "@selector(...)" expression referring to an undeclared selector is found. A selector is considered undeclared if no method with that name has been declared before the "@selector(...)" expression, either explicitly in an @interface or @protocol declaration, or implicitly in an @implementation section. This option always performs its checks as soon as a "@selector(...)" expression is found, while -Wselector only performs its checks in the final stage of compilation. This also enforces the coding style convention that methods and selectors must be declared before being used. -print-objc-runtime-info Generate C header describing the largest structure that is passed by value, if any. Options to Control Diagnostic Messages Formatting Traditionally, diagnostic messages have been formatted irrespective of the output device's aspect (e.g. its width, ...). You can use the options described below to control the formatting algorithm for diagnostic messages, e.g. how many characters per line, how often source location information should be reported. Note that some language front ends may not honor these options. -fmessage-length=n Try to format error messages so that they fit on lines of about n characters. If n is zero, then no line-wrapping is done; each error message appears on a single line. This is the default for all front ends. Note - this option also affects the display of the #error and #warning pre-processor directives, and the deprecated function/type/variable attribute. It does not however affect the pragma GCC warning and pragma GCC error pragmas. -fdiagnostics-plain-output This option requests that diagnostic output look as plain as possible, which may be useful when running dejagnu or other utilities that need to parse diagnostics output and prefer that it remain more stable over time. -fdiagnostics-plain-output is currently equivalent to the following options: -fno-diagnostics-show-caret -fno-diagnostics-show-line-numbers -fdiagnostics-color=never -fdiagnostics-urls=never -fdiagnostics-path-format=separate-events In the future, if GCC changes the default appearance of its diagnostics, the corresponding option to disable the new behavior will be added to this list. -fdiagnostics-show-location=once Only meaningful in line-wrapping mode. Instructs the diagnostic messages reporter to emit source location information once; that is, in case the message is too long to fit on a single physical line and has to be wrapped, the source location won't be emitted (as prefix) again, over and over, in subsequent continuation lines. This is the default behavior. -fdiagnostics-show-location=every-line Only meaningful in line-wrapping mode. Instructs the diagnostic messages reporter to emit the same source location information (as prefix) for physical lines that result from the process of breaking a message which is too long to fit on a single line. -fdiagnostics-color[=WHEN] -fno-diagnostics-color Use color in diagnostics. WHEN is never, always, or auto. The default depends on how the compiler has been configured, it can be any of the above WHEN options or also never if GCC_COLORS environment variable isn't present in the environment, and auto otherwise. auto makes GCC use color only when the standard error is a terminal, and when not executing in an emacs shell. The forms -fdiagnostics-color and -fno-diagnostics-color are aliases for -fdiagnostics-color=always and -fdiagnostics-color=never, respectively. The colors are defined by the environment variable GCC_COLORS. Its value is a colon-separated list of capabilities and Select Graphic Rendition (SGR) substrings. SGR commands are interpreted by the terminal or terminal emulator. (See the section in the documentation of your text terminal for permitted values and their meanings as character attributes.) These substring values are integers in decimal representation and can be concatenated with semicolons. Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. The default GCC_COLORS is error=01;31:warning=01;35:note=01;36:range1=32:range2=34:locus=01:\ quote=01:path=01;36:fixit-insert=32:fixit-delete=31:\ diff-filename=01:diff-hunk=32:diff-delete=31:diff-insert=32:\ type-diff=01;32:fnname=01;32:targs=35 where 01;31 is bold red, 01;35 is bold magenta, 01;36 is bold cyan, 32 is green, 34 is blue, 01 is bold, and 31 is red. Setting GCC_COLORS to the empty string disables colors. Supported capabilities are as follows. "error=" SGR substring for error: markers. "warning=" SGR substring for warning: markers. "note=" SGR substring for note: markers. "path=" SGR substring for colorizing paths of control-flow events as printed via -fdiagnostics-path-format=, such as the identifiers of individual events and lines indicating interprocedural calls and returns. "range1=" SGR substring for first additional range. "range2=" SGR substring for second additional range. "locus=" SGR substring for location information, file:line or file:line:column etc. "quote=" SGR substring for information printed within quotes. "fnname=" SGR substring for names of C++ functions. "targs=" SGR substring for C++ function template parameter bindings. "fixit-insert=" SGR substring for fix-it hints suggesting text to be inserted or replaced. "fixit-delete=" SGR substring for fix-it hints suggesting text to be deleted. "diff-filename=" SGR substring for filename headers within generated patches. "diff-hunk=" SGR substring for the starts of hunks within generated patches. "diff-delete=" SGR substring for deleted lines within generated patches. "diff-insert=" SGR substring for inserted lines within generated patches. "type-diff=" SGR substring for highlighting mismatching types within template arguments in the C++ frontend. -fdiagnostics-urls[=WHEN] Use escape sequences to embed URLs in diagnostics. For example, when -fdiagnostics-show-option emits text showing the command-line option controlling a diagnostic, embed a URL for documentation of that option. WHEN is never, always, or auto. auto makes GCC use URL escape sequences only when the standard error is a terminal, and when not executing in an emacs shell or any graphical terminal which is known to be incompatible with this feature, see below. The default depends on how the compiler has been configured. It can be any of the above WHEN options. GCC can also be configured (via the --with-diagnostics-urls=auto-if-env configure-time option) so that the default is affected by environment variables. Under such a configuration, GCC defaults to using auto if either GCC_URLS or TERM_URLS environment variables are present and non-empty in the environment of the compiler, or never if neither are. However, even with -fdiagnostics-urls=always the behavior is dependent on those environment variables: If GCC_URLS is set to empty or no, do not embed URLs in diagnostics. If set to st, URLs use ST escape sequences. If set to bel, the default, URLs use BEL escape sequences. Any other non-empty value enables the feature. If GCC_URLS is not set, use TERM_URLS as a fallback. Note: ST is an ANSI escape sequence, string terminator ESC \, BEL is an ASCII character, CTRL-G that usually sounds like a beep. At this time GCC tries to detect also a few terminals that are known to not implement the URL feature, and have bugs or at least had bugs in some versions that are still in use, where the URL escapes are likely to misbehave, i.e. print garbage on the screen. That list is currently xfce4-terminal, certain known to be buggy gnome-terminal versions, the linux console, and mingw. This check can be skipped with the -fdiagnostics-urls=always. -fno-diagnostics-show-option By default, each diagnostic emitted includes text indicating the command-line option that directly controls the diagnostic (if such an option is known to the diagnostic machinery). Specifying the -fno-diagnostics-show-option flag suppresses that behavior. -fno-diagnostics-show-caret By default, each diagnostic emitted includes the original source line and a caret ^ indicating the column. This option suppresses this information. The source line is truncated to n characters, if the -fmessage-length=n option is given. When the output is done to the terminal, the width is limited to the width given by the COLUMNS environment variable or, if not set, to the terminal width. -fno-diagnostics-show-labels By default, when printing source code (via -fdiagnostics-show-caret), diagnostics can label ranges of source code with pertinent information, such as the types of expressions: printf ("foo %s bar", long_i + long_j); ~^ ~~~~~~~~~~~~~~~ | | char * long int This option suppresses the printing of these labels (in the example above, the vertical bars and the "char *" and "long int" text). -fno-diagnostics-show-cwe Diagnostic messages can optionally have an associated CWE ("https://cwe.mitre.org/index.html") identifier. GCC itself only provides such metadata for some of the -fanalyzer diagnostics. GCC plugins may also provide diagnostics with such metadata. By default, if this information is present, it will be printed with the diagnostic. This option suppresses the printing of this metadata. -fno-diagnostics-show-rules Diagnostic messages can optionally have rules associated with them, such as from a coding standard, or a specification. GCC itself does not do this for any of its diagnostics, but plugins may do so. By default, if this information is present, it will be printed with the diagnostic. This option suppresses the printing of this metadata. -fno-diagnostics-show-line-numbers By default, when printing source code (via -fdiagnostics-show-caret), a left margin is printed, showing line numbers. This option suppresses this left margin. -fdiagnostics-minimum-margin-width=width This option controls the minimum width of the left margin printed by -fdiagnostics-show-line-numbers. It defaults to 6. -fdiagnostics-parseable-fixits Emit fix-it hints in a machine-parseable format, suitable for consumption by IDEs. For each fix-it, a line will be printed after the relevant diagnostic, starting with the string "fix-it:". For example: fix-it:"test.c":{45:3-45:21}:"gtk_widget_show_all" The location is expressed as a half-open range, expressed as a count of bytes, starting at byte 1 for the initial column. In the above example, bytes 3 through 20 of line 45 of "test.c" are to be replaced with the given string: 00000000011111111112222222222 12345678901234567890123456789 gtk_widget_showall (dlg); ^^^^^^^^^^^^^^^^^^ gtk_widget_show_all The filename and replacement string escape backslash as "\\", tab as "\t", newline as "\n", double quotes as "\"", non-printable characters as octal (e.g. vertical tab as "\013"). An empty replacement string indicates that the given range is to be removed. An empty range (e.g. "45:3-45:3") indicates that the string is to be inserted at the given position. -fdiagnostics-generate-patch Print fix-it hints to stderr in unified diff format, after any diagnostics are printed. For example: --- test.c +++ test.c @ -42,5 +42,5 @ void show_cb(GtkDialog *dlg) { - gtk_widget_showall(dlg); + gtk_widget_show_all(dlg); } The diff may or may not be colorized, following the same rules as for diagnostics (see -fdiagnostics-color). -fdiagnostics-show-template-tree In the C++ frontend, when printing diagnostics showing mismatching template types, such as: could not convert 'std::map<int, std::vector<double> >()' from 'map<[...],vector<double>>' to 'map<[...],vector<float>> the -fdiagnostics-show-template-tree flag enables printing a tree- like structure showing the common and differing parts of the types, such as: map< [...], vector< [double != float]>> The parts that differ are highlighted with color ("double" and "float" in this case). -fno-elide-type By default when the C++ frontend prints diagnostics showing mismatching template types, common parts of the types are printed as "[...]" to simplify the error message. For example: could not convert 'std::map<int, std::vector<double> >()' from 'map<[...],vector<double>>' to 'map<[...],vector<float>> Specifying the -fno-elide-type flag suppresses that behavior. This flag also affects the output of the -fdiagnostics-show-template-tree flag. -fdiagnostics-path-format=KIND Specify how to print paths of control-flow events for diagnostics that have such a path associated with them. KIND is none, separate-events, or inline-events, the default. none means to not print diagnostic paths. separate-events means to print a separate "note" diagnostic for each event within the diagnostic. For example: test.c:29:5: error: passing NULL as argument 1 to 'PyList_Append' which requires a non-NULL parameter test.c:25:10: note: (1) when 'PyList_New' fails, returning NULL test.c:27:3: note: (2) when 'i < count' test.c:29:5: note: (3) when calling 'PyList_Append', passing NULL from (1) as argument 1 inline-events means to print the events "inline" within the source code. This view attempts to consolidate the events into runs of sufficiently-close events, printing them as labelled ranges within the source. For example, the same events as above might be printed as: 'test': events 1-3 | | 25 | list = PyList_New(0); | | ^~~~~~~~~~~~~ | | | | | (1) when 'PyList_New' fails, returning NULL | 26 | | 27 | for (i = 0; i < count; i++) { | | ~~~ | | | | | (2) when 'i < count' | 28 | item = PyLong_FromLong(random()); | 29 | PyList_Append(list, item); | | ~~~~~~~~~~~~~~~~~~~~~~~~~ | | | | | (3) when calling 'PyList_Append', passing NULL from (1) as argument 1 | Interprocedural control flow is shown by grouping the events by stack frame, and using indentation to show how stack frames are nested, pushed, and popped. For example: 'test': events 1-2 | | 133 | { | | ^ | | | | | (1) entering 'test' | 134 | boxed_int *obj = make_boxed_int (i); | | ~~~~~~~~~~~~~~~~~~ | | | | | (2) calling 'make_boxed_int' | +--> 'make_boxed_int': events 3-4 | | 120 | { | | ^ | | | | | (3) entering 'make_boxed_int' | 121 | boxed_int *result = (boxed_int *)wrapped_malloc (sizeof (boxed_int)); | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | | | | | (4) calling 'wrapped_malloc' | +--> 'wrapped_malloc': events 5-6 | | 7 | { | | ^ | | | | | (5) entering 'wrapped_malloc' | 8 | return malloc (size); | | ~~~~~~~~~~~~~ | | | | | (6) calling 'malloc' | <-------------+ | 'test': event 7 | | 138 | free_boxed_int (obj); | | ^~~~~~~~~~~~~~~~~~~~ | | | | | (7) calling 'free_boxed_int' | (etc) -fdiagnostics-show-path-depths This option provides additional information when printing control- flow paths associated with a diagnostic. If this is option is provided then the stack depth will be printed for each run of events within -fdiagnostics-path-format=inline-events. If provided with -fdiagnostics-path-format=separate-events, then the stack depth and function declaration will be appended when printing each event. This is intended for use by GCC developers and plugin developers when debugging diagnostics that report interprocedural control flow. -fno-show-column Do not print column numbers in diagnostics. This may be necessary if diagnostics are being scanned by a program that does not understand the column numbers, such as dejagnu. -fdiagnostics-column-unit=UNIT Select the units for the column number. This affects traditional diagnostics (in the absence of -fno-show-column), as well as JSON format diagnostics if requested. The default UNIT, display, considers the number of display columns occupied by each character. This may be larger than the number of bytes required to encode the character, in the case of tab characters, or it may be smaller, in the case of multibyte characters. For example, the character "GREEK SMALL LETTER PI (U+03C0)" occupies one display column, and its UTF-8 encoding requires two bytes; the character "SLIGHTLY SMILING FACE (U+1F642)" occupies two display columns, and its UTF-8 encoding requires four bytes. Setting UNIT to byte changes the column number to the raw byte count in all cases, as was traditionally output by GCC prior to version 11.1.0. -fdiagnostics-column-origin=ORIGIN Select the origin for column numbers, i.e. the column number assigned to the first column. The default value of 1 corresponds to traditional GCC behavior and to the GNU style guide. Some utilities may perform better with an origin of 0; any non-negative value may be specified. -fdiagnostics-escape-format=FORMAT When GCC prints pertinent source lines for a diagnostic it normally attempts to print the source bytes directly. However, some diagnostics relate to encoding issues in the source file, such as malformed UTF-8, or issues with Unicode normalization. These diagnostics are flagged so that GCC will escape bytes that are not printable ASCII when printing their pertinent source lines. This option controls how such bytes should be escaped. The default FORMAT, unicode displays Unicode characters that are not printable ASCII in the form <U+XXXX>, and bytes that do not correspond to a Unicode character validly-encoded in UTF-8-encoded will be displayed as hexadecimal in the form <XX>. For example, a source line containing the string before followed by the Unicode character U+03C0 ("GREEK SMALL LETTER PI", with UTF-8 encoding 0xCF 0x80) followed by the byte 0xBF (a stray UTF-8 trailing byte), followed by the string after will be printed for such a diagnostic as: before<U+03C0><BF>after Setting FORMAT to bytes will display all non-printable-ASCII bytes in the form <XX>, thus showing the underlying encoding of non-ASCII Unicode characters. For the example above, the following will be printed: before<CF><80><BF>after -fdiagnostics-format=FORMAT Select a different format for printing diagnostics. FORMAT is text, sarif-stderr, sarif-file, json, json-stderr, or json-file. The default is text. The sarif-stderr and sarif-file formats both emit diagnostics in SARIF Version 2.1.0 format, either to stderr, or to a file named source.sarif, respectively. The json format is a synonym for json-stderr. The json-stderr and json-file formats are identical, apart from where the JSON is emitted to - with the former, the JSON is emitted to stderr, whereas with json-file it is written to source.gcc.json. The emitted JSON consists of a top-level JSON array containing JSON objects representing the diagnostics. The JSON is emitted as one line, without formatting; the examples below have been formatted for clarity. Diagnostics can have child diagnostics. For example, this error and note: misleading-indentation.c:15:3: warning: this 'if' clause does not guard... [-Wmisleading-indentation] 15 | if (flag) | ^~ misleading-indentation.c:17:5: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if' 17 | y = 2; | ^ might be printed in JSON form (after formatting) like this: [ { "kind": "warning", "locations": [ { "caret": { "display-column": 3, "byte-column": 3, "column": 3, "file": "misleading-indentation.c", "line": 15 }, "finish": { "display-column": 4, "byte-column": 4, "column": 4, "file": "misleading-indentation.c", "line": 15 } } ], "message": "this \u2018if\u2019 clause does not guard...", "option": "-Wmisleading-indentation", "option_url": "https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmisleading-indentation", "children": [ { "kind": "note", "locations": [ { "caret": { "display-column": 5, "byte-column": 5, "column": 5, "file": "misleading-indentation.c", "line": 17 } } ], "escape-source": false, "message": "...this statement, but the latter is ..." } ] "escape-source": false, "column-origin": 1, } ] where the "note" is a child of the "warning". A diagnostic has a "kind". If this is "warning", then there is an "option" key describing the command-line option controlling the warning. A diagnostic can contain zero or more locations. Each location has an optional "label" string and up to three positions within it: a "caret" position and optional "start" and "finish" positions. A position is described by a "file" name, a "line" number, and three numbers indicating a column position: * "display-column" counts display columns, accounting for tabs and multibyte characters. * "byte-column" counts raw bytes. * "column" is equal to one of the previous two, as dictated by the -fdiagnostics-column-unit option. All three columns are relative to the origin specified by -fdiagnostics-column-origin, which is typically equal to 1 but may be set, for instance, to 0 for compatibility with other utilities that number columns from 0. The column origin is recorded in the JSON output in the "column-origin" tag. In the remaining examples below, the extra column number outputs have been omitted for brevity. For example, this error: bad-binary-ops.c:64:23: error: invalid operands to binary + (have 'S' {aka 'struct s'} and 'T' {aka 'struct t'}) 64 | return callee_4a () + callee_4b (); | ~~~~~~~~~~~~ ^ ~~~~~~~~~~~~ | | | | | T {aka struct t} | S {aka struct s} has three locations. Its primary location is at the "+" token at column 23. It has two secondary locations, describing the left and right-hand sides of the expression, which have labels. It might be printed in JSON form as: { "children": [], "kind": "error", "locations": [ { "caret": { "column": 23, "file": "bad-binary-ops.c", "line": 64 } }, { "caret": { "column": 10, "file": "bad-binary-ops.c", "line": 64 }, "finish": { "column": 21, "file": "bad-binary-ops.c", "line": 64 }, "label": "S {aka struct s}" }, { "caret": { "column": 25, "file": "bad-binary-ops.c", "line": 64 }, "finish": { "column": 36, "file": "bad-binary-ops.c", "line": 64 }, "label": "T {aka struct t}" } ], "escape-source": false, "message": "invalid operands to binary + ..." } If a diagnostic contains fix-it hints, it has a "fixits" array, consisting of half-open intervals, similar to the output of -fdiagnostics-parseable-fixits. For example, this diagnostic with a replacement fix-it hint: demo.c:8:15: error: 'struct s' has no member named 'colour'; did you mean 'color'? 8 | return ptr->colour; | ^~~~~~ | color might be printed in JSON form as: { "children": [], "fixits": [ { "next": { "column": 21, "file": "demo.c", "line": 8 }, "start": { "column": 15, "file": "demo.c", "line": 8 }, "string": "color" } ], "kind": "error", "locations": [ { "caret": { "column": 15, "file": "demo.c", "line": 8 }, "finish": { "column": 20, "file": "demo.c", "line": 8 } } ], "escape-source": false, "message": "\u2018struct s\u2019 has no member named ..." } where the fix-it hint suggests replacing the text from "start" up to but not including "next" with "string"'s value. Deletions are expressed via an empty value for "string", insertions by having "start" equal "next". If the diagnostic has a path of control-flow events associated with it, it has a "path" array of objects representing the events. Each event object has a "description" string, a "location" object, along with a "function" string and a "depth" number for representing interprocedural paths. The "function" represents the current function at that event, and the "depth" represents the stack depth relative to some baseline: the higher, the more frames are within the stack. For example, the intraprocedural example shown for -fdiagnostics-path-format= might have this JSON for its path: "path": [ { "depth": 0, "description": "when 'PyList_New' fails, returning NULL", "function": "test", "location": { "column": 10, "file": "test.c", "line": 25 } }, { "depth": 0, "description": "when 'i < count'", "function": "test", "location": { "column": 3, "file": "test.c", "line": 27 } }, { "depth": 0, "description": "when calling 'PyList_Append', passing NULL from (1) as argument 1", "function": "test", "location": { "column": 5, "file": "test.c", "line": 29 } } ] Diagnostics have a boolean attribute "escape-source", hinting whether non-ASCII bytes should be escaped when printing the pertinent lines of source code ("true" for diagnostics involving source encoding issues). Options to Request or Suppress Warnings Warnings are diagnostic messages that report constructions that are not inherently erroneous but that are risky or suggest there may have been an error. The following language-independent options do not enable specific warnings but control the kinds of diagnostics produced by GCC. -fsyntax-only Check the code for syntax errors, but don't do anything beyond that. -fmax-errors=n Limits the maximum number of error messages to n, at which point GCC bails out rather than attempting to continue processing the source code. If n is 0 (the default), there is no limit on the number of error messages produced. If -Wfatal-errors is also specified, then -Wfatal-errors takes precedence over this option. -w Inhibit all warning messages. -Werror Make all warnings into errors. -Werror= Make the specified warning into an error. The specifier for a warning is appended; for example -Werror=switch turns the warnings controlled by -Wswitch into errors. This switch takes a negative form, to be used to negate -Werror for specific warnings; for example -Wno-error=switch makes -Wswitch warnings not be errors, even when -Werror is in effect. The warning message for each controllable warning includes the option that controls the warning. That option can then be used with -Werror= and -Wno-error= as described above. (Printing of the option in the warning message can be disabled using the -fno-diagnostics-show-option flag.) Note that specifying -Werror=foo automatically implies -Wfoo. However, -Wno-error=foo does not imply anything. -Wfatal-errors This option causes the compiler to abort compilation on the first error occurred rather than trying to keep going and printing further error messages. You can request many specific warnings with options beginning with -W, for example -Wimplicit to request warnings on implicit declarations. Each of these specific warning options also has a negative form beginning -Wno- to turn off warnings; for example, -Wno-implicit. This manual lists only one of the two forms, whichever is not the default. For further language-specific options also refer to C++ Dialect Options and Objective-C and Objective-C++ Dialect Options. Additional warnings can be produced by enabling the static analyzer; Some options, such as -Wall and -Wextra, turn on other options, such as -Wunused, which may turn on further options, such as -Wunused-value. The combined effect of positive and negative forms is that more specific options have priority over less specific ones, independently of their position in the command-line. For options of the same specificity, the last one takes effect. Options enabled or disabled via pragmas take effect as if they appeared at the end of the command-line. When an unrecognized warning option is requested (e.g., -Wunknown-warning), GCC emits a diagnostic stating that the option is not recognized. However, if the -Wno- form is used, the behavior is slightly different: no diagnostic is produced for -Wno-unknown-warning unless other diagnostics are being produced. This allows the use of new -Wno- options with old compilers, but if something goes wrong, the compiler warns that an unrecognized option is present. The effectiveness of some warnings depends on optimizations also being enabled. For example -Wsuggest-final-types is more effective with link- time optimization and some instances of other warnings may not be issued at all unless optimization is enabled. While optimization in general improves the efficacy of control and data flow sensitive warnings, in some cases it may also cause false positives. -Wpedantic -pedantic Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that use forbidden extensions, and some other programs that do not follow ISO C and ISO C++. For ISO C, follows the version of the ISO C standard specified by any -std option used. Valid ISO C and ISO C++ programs should compile properly with or without this option (though a rare few require -ansi or a -std option specifying the required version of ISO C). However, without this option, certain GNU extensions and traditional C and C++ features are supported as well. With this option, they are rejected. -Wpedantic does not cause warning messages for use of the alternate keywords whose names begin and end with __. This alternate format can also be used to disable warnings for non-ISO __intN types, i.e. __intN__. Pedantic warnings are also disabled in the expression that follows "__extension__". However, only system header files should use these escape routes; application programs should avoid them. Some users try to use -Wpedantic to check programs for strict ISO C conformance. They soon find that it does not do quite what they want: it finds some non-ISO practices, but not all---only those for which ISO C requires a diagnostic, and some others for which diagnostics have been added. A feature to report any failure to conform to ISO C might be useful in some instances, but would require considerable additional work and would be quite different from -Wpedantic. We don't have plans to support such a feature in the near future. Where the standard specified with -std represents a GNU extended dialect of C, such as gnu90 or gnu99, there is a corresponding base standard, the version of ISO C on which the GNU extended dialect is based. Warnings from -Wpedantic are given where they are required by the base standard. (It does not make sense for such warnings to be given only for features not in the specified GNU C dialect, since by definition the GNU dialects of C include all features the compiler supports with the given option, and there would be nothing to warn about.) -pedantic-errors Give an error whenever the base standard (see -Wpedantic) requires a diagnostic, in some cases where there is undefined behavior at compile-time and in some other cases that do not prevent compilation of programs that are valid according to the standard. This is not equivalent to -Werror=pedantic, since there are errors enabled by this option and not enabled by the latter and vice versa. -Wall This enables all the warnings about constructions that some users consider questionable, and that are easy to avoid (or modify to prevent the warning), even in conjunction with macros. This also enables some language-specific warnings described in C++ Dialect Options and Objective-C and Objective-C++ Dialect Options. -Wall turns on the following warning flags: -Waddress -Warray-bounds=1 (only with -O2) -Warray-compare -Warray-parameter=2 (C and Objective-C only) -Wbool-compare -Wbool-operation -Wc++11-compat -Wc++14-compat -Wcatch-value (C++ and Objective-C++ only) -Wchar-subscripts -Wcomment -Wdangling-pointer=2 -Wduplicate-decl-specifier (C and Objective-C only) -Wenum-compare (in C/ObjC; this is on by default in C++) -Wenum-int-mismatch (C and Objective-C only) -Wformat -Wformat-overflow -Wformat-truncation -Wint-in-bool-context -Wimplicit (C and Objective-C only) -Wimplicit-int (C and Objective-C only) -Wimplicit-function-declaration (C and Objective- C only) -Winit-self (only for C++) -Wlogical-not-parentheses -Wmain (only for C/ObjC and unless -ffreestanding) -Wmaybe-uninitialized -Wmemset-elt-size -Wmemset-transposed-args -Wmisleading-indentation (only for C/C++) -Wmismatched-dealloc -Wmismatched-new-delete (only for C/C++) -Wmissing-attributes -Wmissing-braces (only for C/ObjC) -Wmultistatement-macros -Wnarrowing (only for C++) -Wnonnull -Wnonnull-compare -Wopenmp-simd -Wparentheses -Wpessimizing-move (only for C++) -Wpointer-sign -Wrange-loop-construct (only for C++) -Wreorder -Wrestrict -Wreturn-type -Wself-move (only for C++) -Wsequence-point -Wsign-compare (only in C++) -Wsizeof-array-div -Wsizeof-pointer-div -Wsizeof-pointer-memaccess -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch -Wtautological-compare -Wtrigraphs -Wuninitialized -Wunknown-pragmas -Wunused-function -Wunused-label -Wunused-value -Wunused-variable -Wuse-after-free=2 -Wvla-parameter (C and Objective-C only) -Wvolatile-register-var -Wzero-length-bounds Note that some warning flags are not implied by -Wall. Some of them warn about constructions that users generally do not consider questionable, but which occasionally you might wish to check for; others warn about constructions that are necessary or hard to avoid in some cases, and there is no simple way to modify the code to suppress the warning. Some of them are enabled by -Wextra but many of them must be enabled individually. -Wextra This enables some extra warning flags that are not enabled by -Wall. (This option used to be called -W. The older name is still supported, but the newer name is more descriptive.) -Wclobbered -Wcast-function-type -Wdangling-reference (C++ only) -Wdeprecated-copy (C++ only) -Wempty-body -Wenum-conversion (C only) -Wignored-qualifiers -Wimplicit-fallthrough=3 -Wmissing-field-initializers -Wmissing-parameter-type (C only) -Wold-style-declaration (C only) -Woverride-init -Wsign-compare (C only) -Wstring-compare -Wredundant-move (only for C++) -Wtype-limits -Wuninitialized -Wshift-negative-value (in C++11 to C++17 and in C99 and newer) -Wunused-parameter (only with -Wunused or -Wall) -Wunused-but-set-parameter (only with -Wunused or -Wall) The option -Wextra also prints warning messages for the following cases: * A pointer is compared against integer zero with "<", "<=", ">", or ">=". * (C++ only) An enumerator and a non-enumerator both appear in a conditional expression. * (C++ only) Ambiguous virtual bases. * (C++ only) Subscripting an array that has been declared "register". * (C++ only) Taking the address of a variable that has been declared "register". * (C++ only) A base class is not initialized in the copy constructor of a derived class. -Wabi (C, Objective-C, C++ and Objective-C++ only) Warn about code affected by ABI changes. This includes code that may not be compatible with the vendor-neutral C++ ABI as well as the psABI for the particular target. Since G++ now defaults to updating the ABI with each major release, normally -Wabi warns only about C++ ABI compatibility problems if there is a check added later in a release series for an ABI issue discovered since the initial release. -Wabi warns about more things if an older ABI version is selected (with -fabi-version=n). -Wabi can also be used with an explicit version number to warn about C++ ABI compatibility with a particular -fabi-version level, e.g. -Wabi=2 to warn about changes relative to -fabi-version=2. If an explicit version number is provided and -fabi-compat-version is not specified, the version number from this option is used for compatibility aliases. If no explicit version number is provided with this option, but -fabi-compat-version is specified, that version number is used for C++ ABI warnings. Although an effort has been made to warn about all such cases, there are probably some cases that are not warned about, even though G++ is generating incompatible code. There may also be cases where warnings are emitted even though the code that is generated is compatible. You should rewrite your code to avoid these warnings if you are concerned about the fact that code generated by G++ may not be binary compatible with code generated by other compilers. Known incompatibilities in -fabi-version=2 (which was the default from GCC 3.4 to 4.9) include: * A template with a non-type template parameter of reference type was mangled incorrectly: extern int N; template <int &> struct S {}; void n (S<N>) {2} This was fixed in -fabi-version=3. * SIMD vector types declared using "__attribute ((vector_size))" were mangled in a non-standard way that does not allow for overloading of functions taking vectors of different sizes. The mangling was changed in -fabi-version=4. * "__attribute ((const))" and "noreturn" were mangled as type qualifiers, and "decltype" of a plain declaration was folded away. These mangling issues were fixed in -fabi-version=5. * Scoped enumerators passed as arguments to a variadic function are promoted like unscoped enumerators, causing "va_arg" to complain. On most targets this does not actually affect the parameter passing ABI, as there is no way to pass an argument smaller than "int". Also, the ABI changed the mangling of template argument packs, "const_cast", "static_cast", prefix increment/decrement, and a class scope function used as a template argument. These issues were corrected in -fabi-version=6. * Lambdas in default argument scope were mangled incorrectly, and the ABI changed the mangling of "nullptr_t". These issues were corrected in -fabi-version=7. * When mangling a function type with function-cv-qualifiers, the un-qualified function type was incorrectly treated as a substitution candidate. This was fixed in -fabi-version=8, the default for GCC 5.1. * "decltype(nullptr)" incorrectly had an alignment of 1, leading to unaligned accesses. Note that this did not affect the ABI of a function with a "nullptr_t" parameter, as parameters have a minimum alignment. This was fixed in -fabi-version=9, the default for GCC 5.2. * Target-specific attributes that affect the identity of a type, such as ia32 calling conventions on a function type (stdcall, regparm, etc.), did not affect the mangled name, leading to name collisions when function pointers were used as template arguments. This was fixed in -fabi-version=10, the default for GCC 6.1. This option also enables warnings about psABI-related changes. The known psABI changes at this point include: * For SysV/x86-64, unions with "long double" members are passed in memory as specified in psABI. Prior to GCC 4.4, this was not the case. For example: union U { long double ld; int i; }; "union U" is now always passed in memory. -Wno-changes-meaning (C++ and Objective-C++ only) C++ requires that unqualified uses of a name within a class have the same meaning in the complete scope of the class, so declaring the name after using it is ill-formed: struct A; struct B1 { A a; typedef A A; }; // warning, 'A' changes meaning struct B2 { A a; struct A { }; }; // error, 'A' changes meaning By default, the B1 case is only a warning because the two declarations have the same type, while the B2 case is an error. Both diagnostics can be disabled with -Wno-changes-meaning. Alternately, the error case can be reduced to a warning with -Wno-error=changes-meaning or -fpermissive. Both diagnostics are also suppressed by -fms-extensions. -Wchar-subscripts Warn if an array subscript has type "char". This is a common cause of error, as programmers often forget that this type is signed on some machines. This warning is enabled by -Wall. -Wno-coverage-mismatch Warn if feedback profiles do not match when using the -fprofile-use option. If a source file is changed between compiling with -fprofile-generate and with -fprofile-use, the files with the profile feedback can fail to match the source file and GCC cannot use the profile feedback information. By default, this warning is enabled and is treated as an error. -Wno-coverage-mismatch can be used to disable the warning or -Wno-error=coverage-mismatch can be used to disable the error. Disabling the error for this warning can result in poorly optimized code and is useful only in the case of very minor changes such as bug fixes to an existing code-base. Completely disabling the warning is not recommended. -Wno-coverage-invalid-line-number Warn in case a function ends earlier than it begins due to an invalid linenum macros. The warning is emitted only with --coverage enabled. By default, this warning is enabled and is treated as an error. -Wno-coverage-invalid-line-number can be used to disable the warning or -Wno-error=coverage-invalid-line-number can be used to disable the error. -Wno-cpp (C, Objective-C, C++, Objective-C++ and Fortran only) Suppress warning messages emitted by "#warning" directives. -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only) Give a warning when a value of type "float" is implicitly promoted to "double". CPUs with a 32-bit "single-precision" floating-point unit implement "float" in hardware, but emulate "double" in software. On such a machine, doing computations using "double" values is much more expensive because of the overhead required for software emulation. It is easy to accidentally do computations with "double" because floating-point literals are implicitly of type "double". For example, in: float area(float radius) { return 3.14159 * radius * radius; } the compiler performs the entire computation with "double" because the floating-point literal is a "double". -Wduplicate-decl-specifier (C and Objective-C only) Warn if a declaration has duplicate "const", "volatile", "restrict" or "_Atomic" specifier. This warning is enabled by -Wall. -Wformat -Wformat=n Check calls to "printf" and "scanf", etc., to make sure that the arguments supplied have types appropriate to the format string specified, and that the conversions specified in the format string make sense. This includes standard functions, and others specified by format attributes, in the "printf", "scanf", "strftime" and "strfmon" (an X/Open extension, not in the C standard) families (or other target-specific families). Which functions are checked without format attributes having been specified depends on the standard version selected, and such checks of functions without the attribute specified are disabled by -ffreestanding or -fno-builtin. The formats are checked against the format features supported by GNU libc version 2.2. These include all ISO C90 and C99 features, as well as features from the Single Unix Specification and some BSD and GNU extensions. Other library implementations may not support all these features; GCC does not support warning about features that go beyond a particular library's limitations. However, if -Wpedantic is used with -Wformat, warnings are given about format features not in the selected standard version (but not for "strfmon" formats, since those are not in any version of the C standard). -Wformat=1 -Wformat Option -Wformat is equivalent to -Wformat=1, and -Wno-format is equivalent to -Wformat=0. Since -Wformat also checks for null format arguments for several functions, -Wformat also implies -Wnonnull. Some aspects of this level of format checking can be disabled by the options: -Wno-format-contains-nul, -Wno-format-extra-args, and -Wno-format-zero-length. -Wformat is enabled by -Wall. -Wformat=2 Enable -Wformat plus additional format checks. Currently equivalent to -Wformat -Wformat-nonliteral -Wformat-security -Wformat-y2k. -Wno-format-contains-nul If -Wformat is specified, do not warn about format strings that contain NUL bytes. -Wno-format-extra-args If -Wformat is specified, do not warn about excess arguments to a "printf" or "scanf" format function. The C standard specifies that such arguments are ignored. Where the unused arguments lie between used arguments that are specified with $ operand number specifications, normally warnings are still given, since the implementation could not know what type to pass to "va_arg" to skip the unused arguments. However, in the case of "scanf" formats, this option suppresses the warning if the unused arguments are all pointers, since the Single Unix Specification says that such unused arguments are allowed. -Wformat-overflow -Wformat-overflow=level Warn about calls to formatted input/output functions such as "sprintf" and "vsprintf" that might overflow the destination buffer. When the exact number of bytes written by a format directive cannot be determined at compile-time it is estimated based on heuristics that depend on the level argument and on optimization. While enabling optimization will in most cases improve the accuracy of the warning, it may also result in false positives. -Wformat-overflow -Wformat-overflow=1 Level 1 of -Wformat-overflow enabled by -Wformat employs a conservative approach that warns only about calls that most likely overflow the buffer. At this level, numeric arguments to format directives with unknown values are assumed to have the value of one, and strings of unknown length to be empty. Numeric arguments that are known to be bounded to a subrange of their type, or string arguments whose output is bounded either by their directive's precision or by a finite set of string literals, are assumed to take on the value within the range that results in the most bytes on output. For example, the call to "sprintf" below is diagnosed because even with both a and b equal to zero, the terminating NUL character ('\0') appended by the function to the destination buffer will be written past its end. Increasing the size of the buffer by a single byte is sufficient to avoid the warning, though it may not be sufficient to avoid the overflow. void f (int a, int b) { char buf [13]; sprintf (buf, "a = %i, b = %i\n", a, b); } -Wformat-overflow=2 Level 2 warns also about calls that might overflow the destination buffer given an argument of sufficient length or magnitude. At level 2, unknown numeric arguments are assumed to have the minimum representable value for signed types with a precision greater than 1, and the maximum representable value otherwise. Unknown string arguments whose length cannot be assumed to be bounded either by the directive's precision, or by a finite set of string literals they may evaluate to, or the character array they may point to, are assumed to be 1 character long. At level 2, the call in the example above is again diagnosed, but this time because with a equal to a 32-bit "INT_MIN" the first %i directive will write some of its digits beyond the end of the destination buffer. To make the call safe regardless of the values of the two variables, the size of the destination buffer must be increased to at least 34 bytes. GCC includes the minimum size of the buffer in an informational note following the warning. An alternative to increasing the size of the destination buffer is to constrain the range of formatted values. The maximum length of string arguments can be bounded by specifying the precision in the format directive. When numeric arguments of format directives can be assumed to be bounded by less than the precision of their type, choosing an appropriate length modifier to the format specifier will reduce the required buffer size. For example, if a and b in the example above can be assumed to be within the precision of the "short int" type then using either the %hi format directive or casting the argument to "short" reduces the maximum required size of the buffer to 24 bytes. void f (int a, int b) { char buf [23]; sprintf (buf, "a = %hi, b = %i\n", a, (short)b); } -Wno-format-zero-length If -Wformat is specified, do not warn about zero-length formats. The C standard specifies that zero-length formats are allowed. -Wformat-nonliteral If -Wformat is specified, also warn if the format string is not a string literal and so cannot be checked, unless the format function takes its format arguments as a "va_list". -Wformat-security If -Wformat is specified, also warn about uses of format functions that represent possible security problems. At present, this warns about calls to "printf" and "scanf" functions where the format string is not a string literal and there are no format arguments, as in "printf (foo);". This may be a security hole if the format string came from untrusted input and contains %n. (This is currently a subset of what -Wformat-nonliteral warns about, but in future warnings may be added to -Wformat-security that are not included in -Wformat-nonliteral.) -Wformat-signedness If -Wformat is specified, also warn if the format string requires an unsigned argument and the argument is signed and vice versa. -Wformat-truncation -Wformat-truncation=level Warn about calls to formatted input/output functions such as "snprintf" and "vsnprintf" that might result in output truncation. When the exact number of bytes written by a format directive cannot be determined at compile-time it is estimated based on heuristics that depend on the level argument and on optimization. While enabling optimization will in most cases improve the accuracy of the warning, it may also result in false positives. Except as noted otherwise, the option uses the same logic -Wformat-overflow. -Wformat-truncation -Wformat-truncation=1 Level 1 of -Wformat-truncation enabled by -Wformat employs a conservative approach that warns only about calls to bounded functions whose return value is unused and that will most likely result in output truncation. -Wformat-truncation=2 Level 2 warns also about calls to bounded functions whose return value is used and that might result in truncation given an argument of sufficient length or magnitude. -Wformat-y2k If -Wformat is specified, also warn about "strftime" formats that may yield only a two-digit year. -Wnonnull Warn about passing a null pointer for arguments marked as requiring a non-null value by the "nonnull" function attribute. -Wnonnull is included in -Wall and -Wformat. It can be disabled with the -Wno-nonnull option. -Wnonnull-compare Warn when comparing an argument marked with the "nonnull" function attribute against null inside the function. -Wnonnull-compare is included in -Wall. It can be disabled with the -Wno-nonnull-compare option. -Wnull-dereference Warn if the compiler detects paths that trigger erroneous or undefined behavior due to dereferencing a null pointer. This option is only active when -fdelete-null-pointer-checks is active, which is enabled by optimizations in most targets. The precision of the warnings depends on the optimization options used. -Winfinite-recursion Warn about infinitely recursive calls. The warning is effective at all optimization levels but requires optimization in order to detect infinite recursion in calls between two or more functions. -Winfinite-recursion is included in -Wall. Compare with -Wanalyzer-infinite-recursion which provides a similar diagnostic, but is implemented in a different way (as part of -fanalyzer). -Winit-self (C, C++, Objective-C and Objective-C++ only) Warn about uninitialized variables that are initialized with themselves. Note this option can only be used with the -Wuninitialized option. For example, GCC warns about "i" being uninitialized in the following snippet only when -Winit-self has been specified: int f() { int i = i; return i; } This warning is enabled by -Wall in C++. -Wno-implicit-int (C and Objective-C only) This option controls warnings when a declaration does not specify a type. This warning is enabled by default in C99 and later dialects of C, and also by -Wall. -Wno-implicit-function-declaration (C and Objective-C only) This option controls warnings when a function is used before being declared. This warning is enabled by default in C99 and later dialects of C, and also by -Wall. The warning is made into an error by -pedantic-errors. -Wimplicit (C and Objective-C only) Same as -Wimplicit-int and -Wimplicit-function-declaration. This warning is enabled by -Wall. -Wimplicit-fallthrough -Wimplicit-fallthrough is the same as -Wimplicit-fallthrough=3 and -Wno-implicit-fallthrough is the same as -Wimplicit-fallthrough=0. -Wimplicit-fallthrough=n Warn when a switch case falls through. For example: switch (cond) { case 1: a = 1; break; case 2: a = 2; case 3: a = 3; break; } This warning does not warn when the last statement of a case cannot fall through, e.g. when there is a return statement or a call to function declared with the noreturn attribute. -Wimplicit-fallthrough= also takes into account control flow statements, such as ifs, and only warns when appropriate. E.g. switch (cond) { case 1: if (i > 3) { bar (5); break; } else if (i < 1) { bar (0); } else return; default: ... } Since there are occasions where a switch case fall through is desirable, GCC provides an attribute, "__attribute__ ((fallthrough))", that is to be used along with a null statement to suppress this warning that would normally occur: switch (cond) { case 1: bar (0); __attribute__ ((fallthrough)); default: ... } C++17 provides a standard way to suppress the -Wimplicit-fallthrough warning using "[[fallthrough]];" instead of the GNU attribute. In C++11 or C++14 users can use "[[gnu::fallthrough]];", which is a GNU extension. Instead of these attributes, it is also possible to add a fallthrough comment to silence the warning. The whole body of the C or C++ style comment should match the given regular expressions listed below. The option argument n specifies what kind of comments are accepted: *<-Wimplicit-fallthrough=0 disables the warning altogether.> *<-Wimplicit-fallthrough=1 matches ".*" regular> expression, any comment is used as fallthrough comment. *<-Wimplicit-fallthrough=2 case insensitively matches> ".*falls?[ \t-]*thr(ough|u).*" regular expression. *<-Wimplicit-fallthrough=3 case sensitively matches one of the> following regular expressions: *<"-fallthrough"> *<"@fallthrough@"> *<"lint -fallthrough[ \t]*"> *<"[ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?FALL(S | |-)?THR(OUGH|U)[ \t.!]*(-[^\n\r]*)?"> *<"[ \t.!]*(Else,? |Intentional(ly)? )?Fall((s | |-)[Tt]|t)hr(ough|u)[ \t.!]*(-[^\n\r]*)?"> *<"[ \t.!]*([Ee]lse,? |[Ii]ntentional(ly)? )?fall(s | |-)?thr(ough|u)[ \t.!]*(-[^\n\r]*)?"> *<-Wimplicit-fallthrough=4 case sensitively matches one of the> following regular expressions: *<"-fallthrough"> *<"@fallthrough@"> *<"lint -fallthrough[ \t]*"> *<"[ \t]*FALLTHR(OUGH|U)[ \t]*"> *<-Wimplicit-fallthrough=5 doesn't recognize any comments as> fallthrough comments, only attributes disable the warning. The comment needs to be followed after optional whitespace and other comments by "case" or "default" keywords or by a user label that precedes some "case" or "default" label. switch (cond) { case 1: bar (0); /* FALLTHRU */ default: ... } The -Wimplicit-fallthrough=3 warning is enabled by -Wextra. -Wno-if-not-aligned (C, C++, Objective-C and Objective-C++ only) Control if warnings triggered by the "warn_if_not_aligned" attribute should be issued. These warnings are enabled by default. -Wignored-qualifiers (C and C++ only) Warn if the return type of a function has a type qualifier such as "const". For ISO C such a type qualifier has no effect, since the value returned by a function is not an lvalue. For C++, the warning is only emitted for scalar types or "void". ISO C prohibits qualified "void" return types on function definitions, so such return types always receive a warning even without this option. This warning is also enabled by -Wextra. -Wno-ignored-attributes (C and C++ only) This option controls warnings when an attribute is ignored. This is different from the -Wattributes option in that it warns whenever the compiler decides to drop an attribute, not that the attribute is either unknown, used in a wrong place, etc. This warning is enabled by default. -Wmain Warn if the type of "main" is suspicious. "main" should be a function with external linkage, returning int, taking either zero arguments, two, or three arguments of appropriate types. This warning is enabled by default in C++ and is enabled by either -Wall or -Wpedantic. -Wmisleading-indentation (C and C++ only) Warn when the indentation of the code does not reflect the block structure. Specifically, a warning is issued for "if", "else", "while", and "for" clauses with a guarded statement that does not use braces, followed by an unguarded statement with the same indentation. In the following example, the call to "bar" is misleadingly indented as if it were guarded by the "if" conditional. if (some_condition ()) foo (); bar (); /* Gotcha: this is not guarded by the "if". */ In the case of mixed tabs and spaces, the warning uses the -ftabstop= option to determine if the statements line up (defaulting to 8). The warning is not issued for code involving multiline preprocessor logic such as the following example. if (flagA) foo (0); #if SOME_CONDITION_THAT_DOES_NOT_HOLD if (flagB) #endif foo (1); The warning is not issued after a "#line" directive, since this typically indicates autogenerated code, and no assumptions can be made about the layout of the file that the directive references. This warning is enabled by -Wall in C and C++. -Wmissing-attributes Warn when a declaration of a function is missing one or more attributes that a related function is declared with and whose absence may adversely affect the correctness or efficiency of generated code. For example, the warning is issued for declarations of aliases that use attributes to specify less restrictive requirements than those of their targets. This typically represents a potential optimization opportunity. By contrast, the -Wattribute-alias=2 option controls warnings issued when the alias is more restrictive than the target, which could lead to incorrect code generation. Attributes considered include "alloc_align", "alloc_size", "cold", "const", "hot", "leaf", "malloc", "nonnull", "noreturn", "nothrow", "pure", "returns_nonnull", and "returns_twice". In C++, the warning is issued when an explicit specialization of a primary template declared with attribute "alloc_align", "alloc_size", "assume_aligned", "format", "format_arg", "malloc", or "nonnull" is declared without it. Attributes "deprecated", "error", and "warning" suppress the warning.. You can use the "copy" attribute to apply the same set of attributes to a declaration as that on another declaration without explicitly enumerating the attributes. This attribute can be applied to declarations of functions, variables, or types. -Wmissing-attributes is enabled by -Wall. For example, since the declaration of the primary function template below makes use of both attribute "malloc" and "alloc_size" the declaration of the explicit specialization of the template is diagnosed because it is missing one of the attributes. template <class T> T* __attribute__ ((malloc, alloc_size (1))) allocate (size_t); template <> void* __attribute__ ((malloc)) // missing alloc_size allocate<void> (size_t); -Wmissing-braces Warn if an aggregate or union initializer is not fully bracketed. In the following example, the initializer for "a" is not fully bracketed, but that for "b" is fully bracketed. int a[2][2] = { 0, 1, 2, 3 }; int b[2][2] = { { 0, 1 }, { 2, 3 } }; This warning is enabled by -Wall. -Wmissing-include-dirs (C, C++, Objective-C, Objective-C++ and Fortran only) Warn if a user-supplied include directory does not exist. This option is disabled by default for C, C++, Objective-C and Objective-C++. For Fortran, it is partially enabled by default by warning for -I and -J, only. -Wno-missing-profile This option controls warnings if feedback profiles are missing when using the -fprofile-use option. This option diagnoses those cases where a new function or a new file is added between compiling with -fprofile-generate and with -fprofile-use, without regenerating the profiles. In these cases, the profile feedback data files do not contain any profile feedback information for the newly added function or file respectively. Also, in the case when profile count data (.gcda) files are removed, GCC cannot use any profile feedback information. In all these cases, warnings are issued to inform you that a profile generation step is due. Ignoring the warning can result in poorly optimized code. -Wno-missing-profile can be used to disable the warning, but this is not recommended and should be done only when non-existent profile data is justified. -Wmismatched-dealloc Warn for calls to deallocation functions with pointer arguments returned from from allocations functions for which the former isn't a suitable deallocator. A pair of functions can be associated as matching allocators and deallocators by use of attribute "malloc". Unless disabled by the -fno-builtin option the standard functions "calloc", "malloc", "realloc", and "free", as well as the corresponding forms of C++ "operator new" and "operator delete" are implicitly associated as matching allocators and deallocators. In the following example "mydealloc" is the deallocator for pointers returned from "myalloc". void mydealloc (void*); __attribute__ ((malloc (mydealloc, 1))) void* myalloc (size_t); void f (void) { void *p = myalloc (32); // ...use p... free (p); // warning: not a matching deallocator for myalloc mydealloc (p); // ok } In C++, the related option -Wmismatched-new-delete diagnoses mismatches involving either "operator new" or "operator delete". Option -Wmismatched-dealloc is included in -Wall. -Wmultistatement-macros Warn about unsafe multiple statement macros that appear to be guarded by a clause such as "if", "else", "for", "switch", or "while", in which only the first statement is actually guarded after the macro is expanded. For example: #define DOIT x++; y++ if (c) DOIT; will increment "y" unconditionally, not just when "c" holds. The can usually be fixed by wrapping the macro in a do-while loop: #define DOIT do { x++; y++; } while (0) if (c) DOIT; This warning is enabled by -Wall in C and C++. -Wparentheses Warn if parentheses are omitted in certain contexts, such as when there is an assignment in a context where a truth value is expected, or when operators are nested whose precedence people often get confused about. Also warn if a comparison like "x<=y<=z" appears; this is equivalent to "(x<=y ? 1 : 0) <= z", which is a different interpretation from that of ordinary mathematical notation. Also warn for dangerous uses of the GNU extension to "?:" with omitted middle operand. When the condition in the "?": operator is a boolean expression, the omitted value is always 1. Often programmers expect it to be a value computed inside the conditional expression instead. For C++ this also warns for some cases of unnecessary parentheses in declarations, which can indicate an attempt at a function call instead of a declaration: { // Declares a local variable called mymutex. std::unique_lock<std::mutex> (mymutex); // User meant std::unique_lock<std::mutex> lock (mymutex); } This warning is enabled by -Wall. -Wno-self-move (C++ and Objective-C++ only) This warning warns when a value is moved to itself with "std::move". Such a "std::move" typically has no effect. struct T { ... }; void fn() { T t; ... t = std::move (t); } This warning is enabled by -Wall. -Wsequence-point Warn about code that may have undefined semantics because of violations of sequence point rules in the C and C++ standards. The C and C++ standards define the order in which expressions in a C/C++ program are evaluated in terms of sequence points, which represent a partial ordering between the execution of parts of the program: those executed before the sequence point, and those executed after it. These occur after the evaluation of a full expression (one which is not part of a larger expression), after the evaluation of the first operand of a "&&", "||", "? :" or "," (comma) operator, before a function is called (but after the evaluation of its arguments and the expression denoting the called function), and in certain other places. Other than as expressed by the sequence point rules, the order of evaluation of subexpressions of an expression is not specified. All these rules describe only a partial order rather than a total order, since, for example, if two functions are called within one expression with no sequence point between them, the order in which the functions are called is not specified. However, the standards committee have ruled that function calls do not overlap. It is not specified when between sequence points modifications to the values of objects take effect. Programs whose behavior depends on this have undefined behavior; the C and C++ standards specify that "Between the previous and next sequence point an object shall have its stored value modified at most once by the evaluation of an expression. Furthermore, the prior value shall be read only to determine the value to be stored.". If a program breaks these rules, the results on any particular implementation are entirely unpredictable. Examples of code with undefined behavior are "a = a++;", "a[n] = b[n++]" and "a[i++] = i;". Some more complicated cases are not diagnosed by this option, and it may give an occasional false positive result, but in general it has been found fairly effective at detecting this sort of problem in programs. The C++17 standard will define the order of evaluation of operands in more cases: in particular it requires that the right-hand side of an assignment be evaluated before the left-hand side, so the above examples are no longer undefined. But this option will still warn about them, to help people avoid writing code that is undefined in C and earlier revisions of C++. The standard is worded confusingly, therefore there is some debate over the precise meaning of the sequence point rules in subtle cases. Links to discussions of the problem, including proposed formal definitions, may be found on the GCC readings page, at <https://gcc.gnu.org/readings.html>. This warning is enabled by -Wall for C and C++. -Wno-return-local-addr Do not warn about returning a pointer (or in C++, a reference) to a variable that goes out of scope after the function returns. -Wreturn-type Warn whenever a function is defined with a return type that defaults to "int". Also warn about any "return" statement with no return value in a function whose return type is not "void" (falling off the end of the function body is considered returning without a value). For C only, warn about a "return" statement with an expression in a function whose return type is "void", unless the expression type is also "void". As a GNU extension, the latter case is accepted without a warning unless -Wpedantic is used. Attempting to use the return value of a non-"void" function other than "main" that flows off the end by reaching the closing curly brace that terminates the function is undefined. Unlike in C, in C++, flowing off the end of a non-"void" function other than "main" results in undefined behavior even when the value of the function is not used. This warning is enabled by default in C++ and by -Wall otherwise. -Wno-shift-count-negative Controls warnings if a shift count is negative. This warning is enabled by default. -Wno-shift-count-overflow Controls warnings if a shift count is greater than or equal to the bit width of the type. This warning is enabled by default. -Wshift-negative-value Warn if left shifting a negative value. This warning is enabled by -Wextra in C99 (and newer) and C++11 to C++17 modes. -Wno-shift-overflow -Wshift-overflow=n These options control warnings about left shift overflows. -Wshift-overflow=1 This is the warning level of -Wshift-overflow and is enabled by default in C99 and C++11 modes (and newer). This warning level does not warn about left-shifting 1 into the sign bit. (However, in C, such an overflow is still rejected in contexts where an integer constant expression is required.) No warning is emitted in C++20 mode (and newer), as signed left shifts always wrap. -Wshift-overflow=2 This warning level also warns about left-shifting 1 into the sign bit, unless C++14 mode (or newer) is active. -Wswitch Warn whenever a "switch" statement has an index of enumerated type and lacks a "case" for one or more of the named codes of that enumeration. (The presence of a "default" label prevents this warning.) "case" labels outside the enumeration range also provoke warnings when this option is used (even if there is a "default" label). This warning is enabled by -Wall. -Wswitch-default Warn whenever a "switch" statement does not have a "default" case. -Wswitch-enum Warn whenever a "switch" statement has an index of enumerated type and lacks a "case" for one or more of the named codes of that enumeration. "case" labels outside the enumeration range also provoke warnings when this option is used. The only difference between -Wswitch and this option is that this option gives a warning about an omitted enumeration code even if there is a "default" label. -Wno-switch-bool Do not warn when a "switch" statement has an index of boolean type and the case values are outside the range of a boolean type. It is possible to suppress this warning by casting the controlling expression to a type other than "bool". For example: switch ((int) (a == 4)) { ... } This warning is enabled by default for C and C++ programs. -Wno-switch-outside-range This option controls warnings when a "switch" case has a value that is outside of its respective type range. This warning is enabled by default for C and C++ programs. -Wno-switch-unreachable Do not warn when a "switch" statement contains statements between the controlling expression and the first case label, which will never be executed. For example: switch (cond) { i = 15; ... case 5: ... } -Wswitch-unreachable does not warn if the statement between the controlling expression and the first case label is just a declaration: switch (cond) { int i; ... case 5: i = 5; ... } This warning is enabled by default for C and C++ programs. -Wsync-nand (C and C++ only) Warn when "__sync_fetch_and_nand" and "__sync_nand_and_fetch" built-in functions are used. These functions changed semantics in GCC 4.4. -Wtrivial-auto-var-init Warn when "-ftrivial-auto-var-init" cannot initialize the automatic variable. A common situation is an automatic variable that is declared between the controlling expression and the first case label of a "switch" statement. -Wunused-but-set-parameter Warn whenever a function parameter is assigned to, but otherwise unused (aside from its declaration). To suppress this warning use the "unused" attribute. This warning is also enabled by -Wunused together with -Wextra. -Wunused-but-set-variable Warn whenever a local variable is assigned to, but otherwise unused (aside from its declaration). This warning is enabled by -Wall. To suppress this warning use the "unused" attribute. This warning is also enabled by -Wunused, which is enabled by -Wall. -Wunused-function Warn whenever a static function is declared but not defined or a non-inline static function is unused. This warning is enabled by -Wall. -Wunused-label Warn whenever a label is declared but not used. This warning is enabled by -Wall. To suppress this warning use the "unused" attribute. -Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only) Warn when a typedef locally defined in a function is not used. This warning is enabled by -Wall. -Wunused-parameter Warn whenever a function parameter is unused aside from its declaration. To suppress this warning use the "unused" attribute. -Wno-unused-result Do not warn if a caller of a function marked with attribute "warn_unused_result" does not use its return value. The default is -Wunused-result. -Wunused-variable Warn whenever a local or static variable is unused aside from its declaration. This option implies -Wunused-const-variable=1 for C, but not for C++. This warning is enabled by -Wall. To suppress this warning use the "unused" attribute. -Wunused-const-variable -Wunused-const-variable=n Warn whenever a constant static variable is unused aside from its declaration. -Wunused-const-variable=1 is enabled by -Wunused-variable for C, but not for C++. In C this declares variable storage, but in C++ this is not an error since const variables take the place of "#define"s. To suppress this warning use the "unused" attribute. -Wunused-const-variable=1 This is the warning level that is enabled by -Wunused-variable for C. It warns only about unused static const variables defined in the main compilation unit, but not about static const variables declared in any header included. -Wunused-const-variable=2 This warning level also warns for unused constant static variables in headers (excluding system headers). This is the warning level of -Wunused-const-variable and must be explicitly requested since in C++ this isn't an error and in C it might be harder to clean up all headers included. -Wunused-value Warn whenever a statement computes a result that is explicitly not used. To suppress this warning cast the unused expression to "void". This includes an expression-statement or the left-hand side of a comma expression that contains no side effects. For example, an expression such as "x[i,j]" causes a warning, while "x[(void)i,j]" does not. This warning is enabled by -Wall. -Wunused All the above -Wunused options combined. In order to get a warning about an unused function parameter, you must either specify -Wextra -Wunused (note that -Wall implies -Wunused), or separately specify -Wunused-parameter. -Wuninitialized Warn if an object with automatic or allocated storage duration is used without having been initialized. In C++, also warn if a non- static reference or non-static "const" member appears in a class without constructors. In addition, passing a pointer (or in C++, a reference) to an uninitialized object to a "const"-qualified argument of a built-in function known to read the object is also diagnosed by this warning. (-Wmaybe-uninitialized is issued for ordinary functions.) If you want to warn about code that uses the uninitialized value of the variable in its own initializer, use the -Winit-self option. These warnings occur for individual uninitialized elements of structure, union or array variables as well as for variables that are uninitialized as a whole. They do not occur for variables or elements declared "volatile". Because these warnings depend on optimization, the exact variables or elements for which there are warnings depend on the precise optimization options and version of GCC used. Note that there may be no warning about a variable that is used only to compute a value that itself is never used, because such computations may be deleted by data flow analysis before the warnings are printed. In C++, this warning also warns about using uninitialized objects in member-initializer-lists. For example, GCC warns about "b" being uninitialized in the following snippet: struct A { int a; int b; A() : a(b) { } }; -Wno-invalid-memory-model This option controls warnings for invocations of __atomic Builtins, __sync Builtins, and the C11 atomic generic functions with a memory consistency argument that is either invalid for the operation or outside the range of values of the "memory_order" enumeration. For example, since the "__atomic_store" and "__atomic_store_n" built- ins are only defined for the relaxed, release, and sequentially consistent memory orders the following code is diagnosed: void store (int *i) { __atomic_store_n (i, 0, memory_order_consume); } -Winvalid-memory-model is enabled by default. -Wmaybe-uninitialized For an object with automatic or allocated storage duration, if there exists a path from the function entry to a use of the object that is initialized, but there exist some other paths for which the object is not initialized, the compiler emits a warning if it cannot prove the uninitialized paths are not executed at run time. In addition, passing a pointer (or in C++, a reference) to an uninitialized object to a "const"-qualified function argument is also diagnosed by this warning. (-Wuninitialized is issued for built-in functions known to read the object.) Annotating the function with attribute "access (none)" indicates that the argument isn't used to access the object and avoids the warning. These warnings are only possible in optimizing compilation, because otherwise GCC does not keep track of the state of variables. These warnings are made optional because GCC may not be able to determine when the code is correct in spite of appearing to have an error. Here is one example of how this can happen: { int x; switch (y) { case 1: x = 1; break; case 2: x = 4; break; case 3: x = 5; } foo (x); } If the value of "y" is always 1, 2 or 3, then "x" is always initialized, but GCC doesn't know this. To suppress the warning, you need to provide a default case with assert(0) or similar code. This option also warns when a non-volatile automatic variable might be changed by a call to "longjmp". The compiler sees only the calls to "setjmp". It cannot know where "longjmp" will be called; in fact, a signal handler could call it at any point in the code. As a result, you may get a warning even when there is in fact no problem because "longjmp" cannot in fact be called at the place that would cause a problem. Some spurious warnings can be avoided if you declare all the functions you use that never return as "noreturn". This warning is enabled by -Wall or -Wextra. -Wunknown-pragmas Warn when a "#pragma" directive is encountered that is not understood by GCC. If this command-line option is used, warnings are even issued for unknown pragmas in system header files. This is not the case if the warnings are only enabled by the -Wall command-line option. -Wno-pragmas Do not warn about misuses of pragmas, such as incorrect parameters, invalid syntax, or conflicts between pragmas. See also -Wunknown-pragmas. -Wno-prio-ctor-dtor Do not warn if a priority from 0 to 100 is used for constructor or destructor. The use of constructor and destructor attributes allow you to assign a priority to the constructor/destructor to control its order of execution before "main" is called or after it returns. The priority values must be greater than 100 as the compiler reserves priority values between 0--100 for the implementation. -Wstrict-aliasing This option is only active when -fstrict-aliasing is active. It warns about code that might break the strict aliasing rules that the compiler is using for optimization. The warning does not catch all cases, but does attempt to catch the more common pitfalls. It is included in -Wall. It is equivalent to -Wstrict-aliasing=3 -Wstrict-aliasing=n This option is only active when -fstrict-aliasing is active. It warns about code that might break the strict aliasing rules that the compiler is using for optimization. Higher levels correspond to higher accuracy (fewer false positives). Higher levels also correspond to more effort, similar to the way -O works. -Wstrict-aliasing is equivalent to -Wstrict-aliasing=3. Level 1: Most aggressive, quick, least accurate. Possibly useful when higher levels do not warn but -fstrict-aliasing still breaks the code, as it has very few false negatives. However, it has many false positives. Warns for all pointer conversions between possibly incompatible types, even if never dereferenced. Runs in the front end only. Level 2: Aggressive, quick, not too precise. May still have many false positives (not as many as level 1 though), and few false negatives (but possibly more than level 1). Unlike level 1, it only warns when an address is taken. Warns about incomplete types. Runs in the front end only. Level 3 (default for -Wstrict-aliasing): Should have very few false positives and few false negatives. Slightly slower than levels 1 or 2 when optimization is enabled. Takes care of the common pun+dereference pattern in the front end: "*(int*)&some_float". If optimization is enabled, it also runs in the back end, where it deals with multiple statement cases using flow-sensitive points-to information. Only warns when the converted pointer is dereferenced. Does not warn about incomplete types. -Wstrict-overflow -Wstrict-overflow=n This option is only active when signed overflow is undefined. It warns about cases where the compiler optimizes based on the assumption that signed overflow does not occur. Note that it does not warn about all cases where the code might overflow: it only warns about cases where the compiler implements some optimization. Thus this warning depends on the optimization level. An optimization that assumes that signed overflow does not occur is perfectly safe if the values of the variables involved are such that overflow never does, in fact, occur. Therefore this warning can easily give a false positive: a warning about code that is not actually a problem. To help focus on important issues, several warning levels are defined. No warnings are issued for the use of undefined signed overflow when estimating how many iterations a loop requires, in particular when determining whether a loop will be executed at all. -Wstrict-overflow=1 Warn about cases that are both questionable and easy to avoid. For example the compiler simplifies "x + 1 > x" to 1. This level of -Wstrict-overflow is enabled by -Wall; higher levels are not, and must be explicitly requested. -Wstrict-overflow=2 Also warn about other cases where a comparison is simplified to a constant. For example: "abs (x) >= 0". This can only be simplified when signed integer overflow is undefined, because "abs (INT_MIN)" overflows to "INT_MIN", which is less than zero. -Wstrict-overflow (with no level) is the same as -Wstrict-overflow=2. -Wstrict-overflow=3 Also warn about other cases where a comparison is simplified. For example: "x + 1 > 1" is simplified to "x > 0". -Wstrict-overflow=4 Also warn about other simplifications not covered by the above cases. For example: "(x * 10) / 5" is simplified to "x * 2". -Wstrict-overflow=5 Also warn about cases where the compiler reduces the magnitude of a constant involved in a comparison. For example: "x + 2 > y" is simplified to "x + 1 >= y". This is reported only at the highest warning level because this simplification applies to many comparisons, so this warning level gives a very large number of false positives. -Wstring-compare Warn for calls to "strcmp" and "strncmp" whose result is determined to be either zero or non-zero in tests for such equality owing to the length of one argument being greater than the size of the array the other argument is stored in (or the bound in the case of "strncmp"). Such calls could be mistakes. For example, the call to "strcmp" below is diagnosed because its result is necessarily non-zero irrespective of the contents of the array "a". extern char a[4]; void f (char *d) { strcpy (d, "string"); ... if (0 == strcmp (a, d)) // cannot be true puts ("a and d are the same"); } -Wstring-compare is enabled by -Wextra. -Wno-stringop-overflow -Wstringop-overflow -Wstringop-overflow=type Warn for calls to string manipulation functions such as "memcpy" and "strcpy" that are determined to overflow the destination buffer. The optional argument is one greater than the type of Object Size Checking to perform to determine the size of the destination. The argument is meaningful only for functions that operate on character arrays but not for raw memory functions like "memcpy" which always make use of Object Size type-0. The option also warns for calls that specify a size in excess of the largest possible object or at most "SIZE_MAX / 2" bytes. The option produces the best results with optimization enabled but can detect a small subset of simple buffer overflows even without optimization in calls to the GCC built-in functions like "__builtin_memcpy" that correspond to the standard functions. In any case, the option warns about just a subset of buffer overflows detected by the corresponding overflow checking built-ins. For example, the option issues a warning for the "strcpy" call below because it copies at least 5 characters (the string "blue" including the terminating NUL) into the buffer of size 4. enum Color { blue, purple, yellow }; const char* f (enum Color clr) { static char buf [4]; const char *str; switch (clr) { case blue: str = "blue"; break; case purple: str = "purple"; break; case yellow: str = "yellow"; break; } return strcpy (buf, str); // warning here } Option -Wstringop-overflow=2 is enabled by default. -Wstringop-overflow -Wstringop-overflow=1 The -Wstringop-overflow=1 option uses type-zero Object Size Checking to determine the sizes of destination objects. At this setting the option does not warn for writes past the end of subobjects of larger objects accessed by pointers unless the size of the largest surrounding object is known. When the destination may be one of several objects it is assumed to be the largest one of them. On Linux systems, when optimization is enabled at this setting the option warns for the same code as when the "_FORTIFY_SOURCE" macro is defined to a non-zero value. -Wstringop-overflow=2 The -Wstringop-overflow=2 option uses type-one Object Size Checking to determine the sizes of destination objects. At this setting the option warns about overflows when writing to members of the largest complete objects whose exact size is known. However, it does not warn for excessive writes to the same members of unknown objects referenced by pointers since they may point to arrays containing unknown numbers of elements. This is the default setting of the option. -Wstringop-overflow=3 The -Wstringop-overflow=3 option uses type-two Object Size Checking to determine the sizes of destination objects. At this setting the option warns about overflowing the smallest object or data member. This is the most restrictive setting of the option that may result in warnings for safe code. -Wstringop-overflow=4 The -Wstringop-overflow=4 option uses type-three Object Size Checking to determine the sizes of destination objects. At this setting the option warns about overflowing any data members, and when the destination is one of several objects it uses the size of the largest of them to decide whether to issue a warning. Similarly to -Wstringop-overflow=3 this setting of the option may result in warnings for benign code. -Wno-stringop-overread Warn for calls to string manipulation functions such as "memchr", or "strcpy" that are determined to read past the end of the source sequence. Option -Wstringop-overread is enabled by default. -Wno-stringop-truncation Do not warn for calls to bounded string manipulation functions such as "strncat", "strncpy", and "stpncpy" that may either truncate the copied string or leave the destination unchanged. In the following example, the call to "strncat" specifies a bound that is less than the length of the source string. As a result, the copy of the source will be truncated and so the call is diagnosed. To avoid the warning use "bufsize - strlen (buf) - 1)" as the bound. void append (char *buf, size_t bufsize) { strncat (buf, ".txt", 3); } As another example, the following call to "strncpy" results in copying to "d" just the characters preceding the terminating NUL, without appending the NUL to the end. Assuming the result of "strncpy" is necessarily a NUL-terminated string is a common mistake, and so the call is diagnosed. To avoid the warning when the result is not expected to be NUL-terminated, call "memcpy" instead. void copy (char *d, const char *s) { strncpy (d, s, strlen (s)); } In the following example, the call to "strncpy" specifies the size of the destination buffer as the bound. If the length of the source string is equal to or greater than this size the result of the copy will not be NUL-terminated. Therefore, the call is also diagnosed. To avoid the warning, specify "sizeof buf - 1" as the bound and set the last element of the buffer to "NUL". void copy (const char *s) { char buf[80]; strncpy (buf, s, sizeof buf); ... } In situations where a character array is intended to store a sequence of bytes with no terminating "NUL" such an array may be annotated with attribute "nonstring" to avoid this warning. Such arrays, however, are not suitable arguments to functions that expect "NUL"-terminated strings. To help detect accidental misuses of such arrays GCC issues warnings unless it can prove that the use is safe. -Wstrict-flex-arrays Warn about inproper usages of flexible array members according to the level of the "strict_flex_array (level)" attribute attached to the trailing array field of a structure if it's available, otherwise according to the level of the option -fstrict-flex-arrays=level. This option is effective only when level is bigger than 0. Otherwise, it will be ignored with a warning. when level=1, warnings will be issued for a trailing array reference of a structure that have 2 or more elements if the trailing array is referenced as a flexible array member. when level=2, in addition to level=1, additional warnings will be issued for a trailing one-element array reference of a structure if the array is referenced as a flexible array member. when level=3, in addition to level=2, additional warnings will be issued for a trailing zero-length array reference of a structure if the array is referenced as a flexible array member. -Wsuggest-attribute=[pure|const|noreturn|format|cold|malloc] Warn for cases where adding an attribute may be beneficial. The attributes currently supported are listed below. -Wsuggest-attribute=pure -Wsuggest-attribute=const -Wsuggest-attribute=noreturn -Wmissing-noreturn -Wsuggest-attribute=malloc Warn about functions that might be candidates for attributes "pure", "const" or "noreturn" or "malloc". The compiler only warns for functions visible in other compilation units or (in the case of "pure" and "const") if it cannot prove that the function returns normally. A function returns normally if it doesn't contain an infinite loop or return abnormally by throwing, calling "abort" or trapping. This analysis requires option -fipa-pure-const, which is enabled by default at -O and higher. Higher optimization levels improve the accuracy of the analysis. -Wsuggest-attribute=format -Wmissing-format-attribute Warn about function pointers that might be candidates for "format" attributes. Note these are only possible candidates, not absolute ones. GCC guesses that function pointers with "format" attributes that are used in assignment, initialization, parameter passing or return statements should have a corresponding "format" attribute in the resulting type. I.e. the left-hand side of the assignment or initialization, the type of the parameter variable, or the return type of the containing function respectively should also have a "format" attribute to avoid the warning. GCC also warns about function definitions that might be candidates for "format" attributes. Again, these are only possible candidates. GCC guesses that "format" attributes might be appropriate for any function that calls a function like "vprintf" or "vscanf", but this might not always be the case, and some functions for which "format" attributes are appropriate may not be detected. -Wsuggest-attribute=cold Warn about functions that might be candidates for "cold" attribute. This is based on static detection and generally only warns about functions which always leads to a call to another "cold" function such as wrappers of C++ "throw" or fatal error reporting functions leading to "abort". -Walloc-zero Warn about calls to allocation functions decorated with attribute "alloc_size" that specify zero bytes, including those to the built- in forms of the functions "aligned_alloc", "alloca", "calloc", "malloc", and "realloc". Because the behavior of these functions when called with a zero size differs among implementations (and in the case of "realloc" has been deprecated) relying on it may result in subtle portability bugs and should be avoided. -Walloc-size-larger-than=byte-size Warn about calls to functions decorated with attribute "alloc_size" that attempt to allocate objects larger than the specified number of bytes, or where the result of the size computation in an integer type with infinite precision would exceed the value of PTRDIFF_MAX on the target. -Walloc-size-larger-than=PTRDIFF_MAX is enabled by default. Warnings controlled by the option can be disabled either by specifying byte-size of SIZE_MAX or more or by -Wno-alloc-size-larger-than. -Wno-alloc-size-larger-than Disable -Walloc-size-larger-than= warnings. The option is equivalent to -Walloc-size-larger-than=SIZE_MAX or larger. -Walloca This option warns on all uses of "alloca" in the source. -Walloca-larger-than=byte-size This option warns on calls to "alloca" with an integer argument whose value is either zero, or that is not bounded by a controlling predicate that limits its value to at most byte-size. It also warns for calls to "alloca" where the bound value is unknown. Arguments of non-integer types are considered unbounded even if they appear to be constrained to the expected range. For example, a bounded case of "alloca" could be: void func (size_t n) { void *p; if (n <= 1000) p = alloca (n); else p = malloc (n); f (p); } In the above example, passing "-Walloca-larger-than=1000" would not issue a warning because the call to "alloca" is known to be at most 1000 bytes. However, if "-Walloca-larger-than=500" were passed, the compiler would emit a warning. Unbounded uses, on the other hand, are uses of "alloca" with no controlling predicate constraining its integer argument. For example: void func () { void *p = alloca (n); f (p); } If "-Walloca-larger-than=500" were passed, the above would trigger a warning, but this time because of the lack of bounds checking. Note, that even seemingly correct code involving signed integers could cause a warning: void func (signed int n) { if (n < 500) { p = alloca (n); f (p); } } In the above example, n could be negative, causing a larger than expected argument to be implicitly cast into the "alloca" call. This option also warns when "alloca" is used in a loop. -Walloca-larger-than=PTRDIFF_MAX is enabled by default but is usually only effective when -ftree-vrp is active (default for -O2 and above). See also -Wvla-larger-than=byte-size. -Wno-alloca-larger-than Disable -Walloca-larger-than= warnings. The option is equivalent to -Walloca-larger-than=SIZE_MAX or larger. -Warith-conversion Do warn about implicit conversions from arithmetic operations even when conversion of the operands to the same type cannot change their values. This affects warnings from -Wconversion, -Wfloat-conversion, and -Wsign-conversion. void f (char c, int i) { c = c + i; // warns with B<-Wconversion> c = c + 1; // only warns with B<-Warith-conversion> } -Warray-bounds -Warray-bounds=n Warn about out of bounds subscripts or offsets into arrays. This warning is enabled by -Wall. It is more effective when -ftree-vrp is active (the default for -O2 and above) but a subset of instances are issued even without optimization. By default, the trailing array of a structure will be treated as a flexible array member by -Warray-bounds or -Warray-bounds=n if it is declared as either a flexible array member per C99 standard onwards ([]), a GCC zero-length array extension ([0]), or an one- element array ([1]). As a result, out of bounds subscripts or offsets into zero-length arrays or one-element arrays are not warned by default. You can add the option -fstrict-flex-arrays or -fstrict-flex-arrays=level to control how this option treat trailing array of a structure as a flexible array member: when level<=1, no change to the default behavior. when level=2, additional warnings will be issued for out of bounds subscripts or offsets into one-element arrays; when level=3, in addition to level=2, additional warnings will be issued for out of bounds subscripts or offsets into zero-length arrays. -Warray-bounds=1 This is the default warning level of -Warray-bounds and is enabled by -Wall; higher levels are not, and must be explicitly requested. -Warray-bounds=2 This warning level also warns about the intermediate results of pointer arithmetic that may yield out of bounds values. This warning level may give a larger number of false positives and is deactivated by default. -Warray-compare Warn about equality and relational comparisons between two operands of array type. This comparison was deprecated in C++20. For example: int arr1[5]; int arr2[5]; bool same = arr1 == arr2; -Warray-compare is enabled by -Wall. -Warray-parameter -Warray-parameter=n Warn about redeclarations of functions involving arguments of array or pointer types of inconsistent kinds or forms, and enable the detection of out-of-bounds accesses to such parameters by warnings such as -Warray-bounds. If the first function declaration uses the array form the bound specified in the array is assumed to be the minimum number of elements expected to be provided in calls to the function and the maximum number of elements accessed by it. Failing to provide arguments of sufficient size or accessing more than the maximum number of elements may be diagnosed by warnings such as -Warray-bounds. At level 1 the warning diagnoses inconsistencies involving array parameters declared using the "T[static N]" form. For example, the warning triggers for the following redeclarations because the first one allows an array of any size to be passed to "f" while the second one with the keyword "static" specifies that the array argument must have at least four elements. void f (int[static 4]); void f (int[]); // warning (inconsistent array form) void g (void) { int *p = (int *)malloc (4); f (p); // warning (array too small) ... } At level 2 the warning also triggers for redeclarations involving any other inconsistency in array or pointer argument forms denoting array sizes. Pointers and arrays of unspecified bound are considered equivalent and do not trigger a warning. void g (int*); void g (int[]); // no warning void g (int[8]); // warning (inconsistent array bound) -Warray-parameter=2 is included in -Wall. The -Wvla-parameter option triggers warnings for similar inconsistencies involving Variable Length Array arguments. -Wattribute-alias=n -Wno-attribute-alias Warn about declarations using the "alias" and similar attributes whose target is incompatible with the type of the alias. -Wattribute-alias=1 The default warning level of the -Wattribute-alias option diagnoses incompatibilities between the type of the alias declaration and that of its target. Such incompatibilities are typically indicative of bugs. -Wattribute-alias=2 At this level -Wattribute-alias also diagnoses cases where the attributes of the alias declaration are more restrictive than the attributes applied to its target. These mismatches can potentially result in incorrect code generation. In other cases they may be benign and could be resolved simply by adding the missing attribute to the target. For comparison, see the -Wmissing-attributes option, which controls diagnostics when the alias declaration is less restrictive than the target, rather than more restrictive. Attributes considered include "alloc_align", "alloc_size", "cold", "const", "hot", "leaf", "malloc", "nonnull", "noreturn", "nothrow", "pure", "returns_nonnull", and "returns_twice". -Wattribute-alias is equivalent to -Wattribute-alias=1. This is the default. You can disable these warnings with either -Wno-attribute-alias or -Wattribute-alias=0. -Wbidi-chars=[none|unpaired|any|ucn] Warn about possibly misleading UTF-8 bidirectional control characters in comments, string literals, character constants, and identifiers. Such characters can change left-to-right writing direction into right-to-left (and vice versa), which can cause confusion between the logical order and visual order. This may be dangerous; for instance, it may seem that a piece of code is not commented out, whereas it in fact is. There are three levels of warning supported by GCC. The default is -Wbidi-chars=unpaired, which warns about improperly terminated bidi contexts. -Wbidi-chars=none turns the warning off. -Wbidi-chars=any warns about any use of bidirectional control characters. By default, this warning does not warn about UCNs. It is, however, possible to turn on such checking by using -Wbidi-chars=unpaired,ucn or -Wbidi-chars=any,ucn. Using -Wbidi-chars=ucn is valid, and is equivalent to -Wbidi-chars=unpaired,ucn, if no previous -Wbidi-chars=any was specified. -Wbool-compare Warn about boolean expression compared with an integer value different from "true"/"false". For instance, the following comparison is always false: int n = 5; ... if ((n > 1) == 2) { ... } This warning is enabled by -Wall. -Wbool-operation Warn about suspicious operations on expressions of a boolean type. For instance, bitwise negation of a boolean is very likely a bug in the program. For C, this warning also warns about incrementing or decrementing a boolean, which rarely makes sense. (In C++, decrementing a boolean is always invalid. Incrementing a boolean is invalid in C++17, and deprecated otherwise.) This warning is enabled by -Wall. -Wduplicated-branches Warn when an if-else has identical branches. This warning detects cases like if (p != NULL) return 0; else return 0; It doesn't warn when both branches contain just a null statement. This warning also warn for conditional operators: int i = x ? *p : *p; -Wduplicated-cond Warn about duplicated conditions in an if-else-if chain. For instance, warn for the following code: if (p->q != NULL) { ... } else if (p->q != NULL) { ... } -Wframe-address Warn when the __builtin_frame_address or __builtin_return_address is called with an argument greater than 0. Such calls may return indeterminate values or crash the program. The warning is included in -Wall. -Wno-discarded-qualifiers (C and Objective-C only) Do not warn if type qualifiers on pointers are being discarded. Typically, the compiler warns if a "const char *" variable is passed to a function that takes a "char *" parameter. This option can be used to suppress such a warning. -Wno-discarded-array-qualifiers (C and Objective-C only) Do not warn if type qualifiers on arrays which are pointer targets are being discarded. Typically, the compiler warns if a "const int (*)[]" variable is passed to a function that takes a "int (*)[]" parameter. This option can be used to suppress such a warning. -Wno-incompatible-pointer-types (C and Objective-C only) Do not warn when there is a conversion between pointers that have incompatible types. This warning is for cases not covered by -Wno-pointer-sign, which warns for pointer argument passing or assignment with different signedness. -Wno-int-conversion (C and Objective-C only) Do not warn about incompatible integer to pointer and pointer to integer conversions. This warning is about implicit conversions; for explicit conversions the warnings -Wno-int-to-pointer-cast and -Wno-pointer-to-int-cast may be used. -Wzero-length-bounds Warn about accesses to elements of zero-length array members that might overlap other members of the same object. Declaring interior zero-length arrays is discouraged because accesses to them are undefined. For example, the first two stores in function "bad" are diagnosed because the array elements overlap the subsequent members "b" and "c". The third store is diagnosed by -Warray-bounds because it is beyond the bounds of the enclosing object. struct X { int a[0]; int b, c; }; struct X x; void bad (void) { x.a[0] = 0; // -Wzero-length-bounds x.a[1] = 1; // -Wzero-length-bounds x.a[2] = 2; // -Warray-bounds } Option -Wzero-length-bounds is enabled by -Warray-bounds. -Wno-div-by-zero Do not warn about compile-time integer division by zero. Floating- point division by zero is not warned about, as it can be a legitimate way of obtaining infinities and NaNs. -Wsystem-headers Print warning messages for constructs found in system header files. Warnings from system headers are normally suppressed, on the assumption that they usually do not indicate real problems and would only make the compiler output harder to read. Using this command-line option tells GCC to emit warnings from system headers as if they occurred in user code. However, note that using -Wall in conjunction with this option does not warn about unknown pragmas in system headers---for that, -Wunknown-pragmas must also be used. -Wtautological-compare Warn if a self-comparison always evaluates to true or false. This warning detects various mistakes such as: int i = 1; ... if (i > i) { ... } This warning also warns about bitwise comparisons that always evaluate to true or false, for instance: if ((a & 16) == 10) { ... } will always be false. This warning is enabled by -Wall. -Wtrampolines Warn about trampolines generated for pointers to nested functions. A trampoline is a small piece of data or code that is created at run time on the stack when the address of a nested function is taken, and is used to call the nested function indirectly. For some targets, it is made up of data only and thus requires no special treatment. But, for most targets, it is made up of code and thus requires the stack to be made executable in order for the program to work properly. -Wfloat-equal Warn if floating-point values are used in equality comparisons. The idea behind this is that sometimes it is convenient (for the programmer) to consider floating-point values as approximations to infinitely precise real numbers. If you are doing this, then you need to compute (by analyzing the code, or in some other way) the maximum or likely maximum error that the computation introduces, and allow for it when performing comparisons (and when producing output, but that's a different problem). In particular, instead of testing for equality, you should check to see whether the two values have ranges that overlap; and this is done with the relational operators, so equality comparisons are probably mistaken. -Wtraditional (C and Objective-C only) Warn about certain constructs that behave differently in traditional and ISO C. Also warn about ISO C constructs that have no traditional C equivalent, and/or problematic constructs that should be avoided. * Macro parameters that appear within string literals in the macro body. In traditional C macro replacement takes place within string literals, but in ISO C it does not. * In traditional C, some preprocessor directives did not exist. Traditional preprocessors only considered a line to be a directive if the # appeared in column 1 on the line. Therefore -Wtraditional warns about directives that traditional C understands but ignores because the # does not appear as the first character on the line. It also suggests you hide directives like "#pragma" not understood by traditional C by indenting them. Some traditional implementations do not recognize "#elif", so this option suggests avoiding it altogether. * A function-like macro that appears without arguments. * The unary plus operator. * The U integer constant suffix, or the F or L floating-point constant suffixes. (Traditional C does support the L suffix on integer constants.) Note, these suffixes appear in macros defined in the system headers of most modern systems, e.g. the _MIN/_MAX macros in "<limits.h>". Use of these macros in user code might normally lead to spurious warnings, however GCC's integrated preprocessor has enough context to avoid warning in these cases. * A function declared external in one block and then used after the end of the block. * A "switch" statement has an operand of type "long". * A non-"static" function declaration follows a "static" one. This construct is not accepted by some traditional C compilers. * The ISO type of an integer constant has a different width or signedness from its traditional type. This warning is only issued if the base of the constant is ten. I.e. hexadecimal or octal values, which typically represent bit patterns, are not warned about. * Usage of ISO string concatenation is detected. * Initialization of automatic aggregates. * Identifier conflicts with labels. Traditional C lacks a separate namespace for labels. * Initialization of unions. If the initializer is zero, the warning is omitted. This is done under the assumption that the zero initializer in user code appears conditioned on e.g. "__STDC__" to avoid missing initializer warnings and relies on default initialization to zero in the traditional C case. * Conversions by prototypes between fixed/floating-point values and vice versa. The absence of these prototypes when compiling with traditional C causes serious problems. This is a subset of the possible conversion warnings; for the full set use -Wtraditional-conversion. * Use of ISO C style function definitions. This warning intentionally is not issued for prototype declarations or variadic functions because these ISO C features appear in your code when using libiberty's traditional C compatibility macros, "PARAMS" and "VPARAMS". This warning is also bypassed for nested functions because that feature is already a GCC extension and thus not relevant to traditional C compatibility. -Wtraditional-conversion (C and Objective-C only) Warn if a prototype causes a type conversion that is different from what would happen to the same argument in the absence of a prototype. This includes conversions of fixed point to floating and vice versa, and conversions changing the width or signedness of a fixed-point argument except when the same as the default promotion. -Wdeclaration-after-statement (C and Objective-C only) Warn when a declaration is found after a statement in a block. This construct, known from C++, was introduced with ISO C99 and is by default allowed in GCC. It is not supported by ISO C90. -Wshadow Warn whenever a local variable or type declaration shadows another variable, parameter, type, class member (in C++), or instance variable (in Objective-C) or whenever a built-in function is shadowed. Note that in C++, the compiler warns if a local variable shadows an explicit typedef, but not if it shadows a struct/class/enum. If this warning is enabled, it includes also all instances of local shadowing. This means that -Wno-shadow=local and -Wno-shadow=compatible-local are ignored when -Wshadow is used. Same as -Wshadow=global. -Wno-shadow-ivar (Objective-C only) Do not warn whenever a local variable shadows an instance variable in an Objective-C method. -Wshadow=global Warn for any shadowing. Same as -Wshadow. -Wshadow=local Warn when a local variable shadows another local variable or parameter. -Wshadow=compatible-local Warn when a local variable shadows another local variable or parameter whose type is compatible with that of the shadowing variable. In C++, type compatibility here means the type of the shadowing variable can be converted to that of the shadowed variable. The creation of this flag (in addition to -Wshadow=local) is based on the idea that when a local variable shadows another one of incompatible type, it is most likely intentional, not a bug or typo, as shown in the following example: for (SomeIterator i = SomeObj.begin(); i != SomeObj.end(); ++i) { for (int i = 0; i < N; ++i) { ... } ... } Since the two variable "i" in the example above have incompatible types, enabling only -Wshadow=compatible-local does not emit a warning. Because their types are incompatible, if a programmer accidentally uses one in place of the other, type checking is expected to catch that and emit an error or warning. Use of this flag instead of -Wshadow=local can possibly reduce the number of warnings triggered by intentional shadowing. Note that this also means that shadowing "const char *i" by "char *i" does not emit a warning. This warning is also enabled by -Wshadow=local. -Wlarger-than=byte-size Warn whenever an object is defined whose size exceeds byte-size. -Wlarger-than=PTRDIFF_MAX is enabled by default. Warnings controlled by the option can be disabled either by specifying byte- size of SIZE_MAX or more or by -Wno-larger-than. Also warn for calls to bounded functions such as "memchr" or "strnlen" that specify a bound greater than the largest possible object, which is PTRDIFF_MAX bytes by default. These warnings can only be disabled by -Wno-larger-than. -Wno-larger-than Disable -Wlarger-than= warnings. The option is equivalent to -Wlarger-than=SIZE_MAX or larger. -Wframe-larger-than=byte-size Warn if the size of a function frame exceeds byte-size. The computation done to determine the stack frame size is approximate and not conservative. The actual requirements may be somewhat greater than byte-size even if you do not get a warning. In addition, any space allocated via "alloca", variable-length arrays, or related constructs is not included by the compiler when determining whether or not to issue a warning. -Wframe-larger-than=PTRDIFF_MAX is enabled by default. Warnings controlled by the option can be disabled either by specifying byte- size of SIZE_MAX or more or by -Wno-frame-larger-than. -Wno-frame-larger-than Disable -Wframe-larger-than= warnings. The option is equivalent to -Wframe-larger-than=SIZE_MAX or larger. -Wfree-nonheap-object Warn when attempting to deallocate an object that was either not allocated on the heap, or by using a pointer that was not returned from a prior call to the corresponding allocation function. For example, because the call to "stpcpy" returns a pointer to the terminating nul character and not to the beginning of the object, the call to "free" below is diagnosed. void f (char *p) { p = stpcpy (p, "abc"); // ... free (p); // warning } -Wfree-nonheap-object is included in -Wall. -Wstack-usage=byte-size Warn if the stack usage of a function might exceed byte-size. The computation done to determine the stack usage is conservative. Any space allocated via "alloca", variable-length arrays, or related constructs is included by the compiler when determining whether or not to issue a warning. The message is in keeping with the output of -fstack-usage. * If the stack usage is fully static but exceeds the specified amount, it's: warning: stack usage is 1120 bytes * If the stack usage is (partly) dynamic but bounded, it's: warning: stack usage might be 1648 bytes * If the stack usage is (partly) dynamic and not bounded, it's: warning: stack usage might be unbounded -Wstack-usage=PTRDIFF_MAX is enabled by default. Warnings controlled by the option can be disabled either by specifying byte- size of SIZE_MAX or more or by -Wno-stack-usage. -Wno-stack-usage Disable -Wstack-usage= warnings. The option is equivalent to -Wstack-usage=SIZE_MAX or larger. -Wunsafe-loop-optimizations Warn if the loop cannot be optimized because the compiler cannot assume anything on the bounds of the loop indices. With -funsafe-loop-optimizations warn if the compiler makes such assumptions. -Wno-pedantic-ms-format (MinGW targets only) When used in combination with -Wformat and -pedantic without GNU extensions, this option disables the warnings about non-ISO "printf" / "scanf" format width specifiers "I32", "I64", and "I" used on Windows targets, which depend on the MS runtime. -Wpointer-arith Warn about anything that depends on the "size of" a function type or of "void". GNU C assigns these types a size of 1, for convenience in calculations with "void *" pointers and pointers to functions. In C++, warn also when an arithmetic operation involves "NULL". This warning is also enabled by -Wpedantic. -Wno-pointer-compare Do not warn if a pointer is compared with a zero character constant. This usually means that the pointer was meant to be dereferenced. For example: const char *p = foo (); if (p == '\0') return 42; Note that the code above is invalid in C++11. This warning is enabled by default. -Wtsan Warn about unsupported features in ThreadSanitizer. ThreadSanitizer does not support "std::atomic_thread_fence" and can report false positives. This warning is enabled by default. -Wtype-limits Warn if a comparison is always true or always false due to the limited range of the data type, but do not warn for constant expressions. For example, warn if an unsigned variable is compared against zero with "<" or ">=". This warning is also enabled by -Wextra. -Wabsolute-value (C and Objective-C only) Warn for calls to standard functions that compute the absolute value of an argument when a more appropriate standard function is available. For example, calling "abs(3.14)" triggers the warning because the appropriate function to call to compute the absolute value of a double argument is "fabs". The option also triggers warnings when the argument in a call to such a function has an unsigned type. This warning can be suppressed with an explicit type cast and it is also enabled by -Wextra. -Wcomment -Wcomments Warn whenever a comment-start sequence /* appears in a /* comment, or whenever a backslash-newline appears in a // comment. This warning is enabled by -Wall. -Wtrigraphs Warn if any trigraphs are encountered that might change the meaning of the program. Trigraphs within comments are not warned about, except those that would form escaped newlines. This option is implied by -Wall. If -Wall is not given, this option is still enabled unless trigraphs are enabled. To get trigraph conversion without warnings, but get the other -Wall warnings, use -trigraphs -Wall -Wno-trigraphs. -Wundef Warn if an undefined identifier is evaluated in an "#if" directive. Such identifiers are replaced with zero. -Wexpansion-to-defined Warn whenever defined is encountered in the expansion of a macro (including the case where the macro is expanded by an #if directive). Such usage is not portable. This warning is also enabled by -Wpedantic and -Wextra. -Wunused-macros Warn about macros defined in the main file that are unused. A macro is used if it is expanded or tested for existence at least once. The preprocessor also warns if the macro has not been used at the time it is redefined or undefined. Built-in macros, macros defined on the command line, and macros defined in include files are not warned about. Note: If a macro is actually used, but only used in skipped conditional blocks, then the preprocessor reports it as unused. To avoid the warning in such a case, you might improve the scope of the macro's definition by, for example, moving it into the first skipped block. Alternatively, you could provide a dummy use with something like: #if defined the_macro_causing_the_warning #endif -Wno-endif-labels Do not warn whenever an "#else" or an "#endif" are followed by text. This sometimes happens in older programs with code of the form #if FOO ... #else FOO ... #endif FOO The second and third "FOO" should be in comments. This warning is on by default. -Wbad-function-cast (C and Objective-C only) Warn when a function call is cast to a non-matching type. For example, warn if a call to a function returning an integer type is cast to a pointer type. -Wc90-c99-compat (C and Objective-C only) Warn about features not present in ISO C90, but present in ISO C99. For instance, warn about use of variable length arrays, "long long" type, "bool" type, compound literals, designated initializers, and so on. This option is independent of the standards mode. Warnings are disabled in the expression that follows "__extension__". -Wc99-c11-compat (C and Objective-C only) Warn about features not present in ISO C99, but present in ISO C11. For instance, warn about use of anonymous structures and unions, "_Atomic" type qualifier, "_Thread_local" storage-class specifier, "_Alignas" specifier, "Alignof" operator, "_Generic" keyword, and so on. This option is independent of the standards mode. Warnings are disabled in the expression that follows "__extension__". -Wc11-c2x-compat (C and Objective-C only) Warn about features not present in ISO C11, but present in ISO C2X. For instance, warn about omitting the string in "_Static_assert", use of [[]] syntax for attributes, use of decimal floating-point types, and so on. This option is independent of the standards mode. Warnings are disabled in the expression that follows "__extension__". -Wc++-compat (C and Objective-C only) Warn about ISO C constructs that are outside of the common subset of ISO C and ISO C++, e.g. request for implicit conversion from "void *" to a pointer to non-"void" type. -Wc++11-compat (C++ and Objective-C++ only) Warn about C++ constructs whose meaning differs between ISO C++ 1998 and ISO C++ 2011, e.g., identifiers in ISO C++ 1998 that are keywords in ISO C++ 2011. This warning turns on -Wnarrowing and is enabled by -Wall. -Wc++14-compat (C++ and Objective-C++ only) Warn about C++ constructs whose meaning differs between ISO C++ 2011 and ISO C++ 2014. This warning is enabled by -Wall. -Wc++17-compat (C++ and Objective-C++ only) Warn about C++ constructs whose meaning differs between ISO C++ 2014 and ISO C++ 2017. This warning is enabled by -Wall. -Wc++20-compat (C++ and Objective-C++ only) Warn about C++ constructs whose meaning differs between ISO C++ 2017 and ISO C++ 2020. This warning is enabled by -Wall. -Wno-c++11-extensions (C++ and Objective-C++ only) Do not warn about C++11 constructs in code being compiled using an older C++ standard. Even without this option, some C++11 constructs will only be diagnosed if -Wpedantic is used. -Wno-c++14-extensions (C++ and Objective-C++ only) Do not warn about C++14 constructs in code being compiled using an older C++ standard. Even without this option, some C++14 constructs will only be diagnosed if -Wpedantic is used. -Wno-c++17-extensions (C++ and Objective-C++ only) Do not warn about C++17 constructs in code being compiled using an older C++ standard. Even without this option, some C++17 constructs will only be diagnosed if -Wpedantic is used. -Wno-c++20-extensions (C++ and Objective-C++ only) Do not warn about C++20 constructs in code being compiled using an older C++ standard. Even without this option, some C++20 constructs will only be diagnosed if -Wpedantic is used. -Wno-c++23-extensions (C++ and Objective-C++ only) Do not warn about C++23 constructs in code being compiled using an older C++ standard. Even without this option, some C++23 constructs will only be diagnosed if -Wpedantic is used. -Wcast-qual Warn whenever a pointer is cast so as to remove a type qualifier from the target type. For example, warn if a "const char *" is cast to an ordinary "char *". Also warn when making a cast that introduces a type qualifier in an unsafe way. For example, casting "char **" to "const char **" is unsafe, as in this example: /* p is char ** value. */ const char **q = (const char **) p; /* Assignment of readonly string to const char * is OK. */ *q = "string"; /* Now char** pointer points to read-only memory. */ **p = 'b'; -Wcast-align Warn whenever a pointer is cast such that the required alignment of the target is increased. For example, warn if a "char *" is cast to an "int *" on machines where integers can only be accessed at two- or four-byte boundaries. -Wcast-align=strict Warn whenever a pointer is cast such that the required alignment of the target is increased. For example, warn if a "char *" is cast to an "int *" regardless of the target machine. -Wcast-function-type Warn when a function pointer is cast to an incompatible function pointer. In a cast involving function types with a variable argument list only the types of initial arguments that are provided are considered. Any parameter of pointer-type matches any other pointer-type. Any benign differences in integral types are ignored, like "int" vs. "long" on ILP32 targets. Likewise type qualifiers are ignored. The function type "void (*) (void)" is special and matches everything, which can be used to suppress this warning. In a cast involving pointer to member types this warning warns whenever the type cast is changing the pointer to member type. This warning is enabled by -Wextra. -Wwrite-strings When compiling C, give string constants the type "const char[length]" so that copying the address of one into a non-"const" "char *" pointer produces a warning. These warnings help you find at compile time code that can try to write into a string constant, but only if you have been very careful about using "const" in declarations and prototypes. Otherwise, it is just a nuisance. This is why we did not make -Wall request these warnings. When compiling C++, warn about the deprecated conversion from string literals to "char *". This warning is enabled by default for C++ programs. -Wclobbered Warn for variables that might be changed by "longjmp" or "vfork". This warning is also enabled by -Wextra. -Wno-complain-wrong-lang By default, language front ends complain when a command-line option is valid, but not applicable to that front end. This may be disabled with -Wno-complain-wrong-lang, which is mostly useful when invoking a single compiler driver for multiple source files written in different languages, for example: $ g++ -fno-rtti a.cc b.f90 The driver g++ invokes the C++ front end to compile a.cc and the Fortran front end to compile b.f90. The latter front end diagnoses f951: Warning: command-line option '-fno-rtti' is valid for C++/D/ObjC++ but not for Fortran, which may be disabled with -Wno-complain-wrong-lang. -Wconversion Warn for implicit conversions that may alter a value. This includes conversions between real and integer, like "abs (x)" when "x" is "double"; conversions between signed and unsigned, like "unsigned ui = -1"; and conversions to smaller types, like "sqrtf (M_PI)". Do not warn for explicit casts like "abs ((int) x)" and "ui = (unsigned) -1", or if the value is not changed by the conversion like in "abs (2.0)". Warnings about conversions between signed and unsigned integers can be disabled by using -Wno-sign-conversion. For C++, also warn for confusing overload resolution for user- defined conversions; and conversions that never use a type conversion operator: conversions to "void", the same type, a base class or a reference to them. Warnings about conversions between signed and unsigned integers are disabled by default in C++ unless -Wsign-conversion is explicitly enabled. Warnings about conversion from arithmetic on a small type back to that type are only given with -Warith-conversion. -Wdangling-else Warn about constructions where there may be confusion to which "if" statement an "else" branch belongs. Here is an example of such a case: { if (a) if (b) foo (); else bar (); } In C/C++, every "else" branch belongs to the innermost possible "if" statement, which in this example is "if (b)". This is often not what the programmer expected, as illustrated in the above example by indentation the programmer chose. When there is the potential for this confusion, GCC issues a warning when this flag is specified. To eliminate the warning, add explicit braces around the innermost "if" statement so there is no way the "else" can belong to the enclosing "if". The resulting code looks like this: { if (a) { if (b) foo (); else bar (); } } This warning is enabled by -Wparentheses. -Wdangling-pointer -Wdangling-pointer=n Warn about uses of pointers (or C++ references) to objects with automatic storage duration after their lifetime has ended. This includes local variables declared in nested blocks, compound literals and other unnamed temporary objects. In addition, warn about storing the address of such objects in escaped pointers. The warning is enabled at all optimization levels but may yield different results with optimization than without. -Wdangling-pointer=1 At level 1 the warning diagnoses only unconditional uses of dangling pointers. For example int f (int c1, int c2, x) { char *p = strchr ((char[]){ c1, c2 }, c3); // warning: dangling pointer to a compound literal return p ? *p : 'x'; } In the following function the store of the address of the local variable "x" in the escaped pointer *p also triggers the warning. void g (int **p) { int x = 7; // warning: storing the address of a local variable in *p *p = &x; } -Wdangling-pointer=2 At level 2, in addition to unconditional uses the warning also diagnoses conditional uses of dangling pointers. For example, because the array a in the following function is out of scope when the pointer s that was set to point is used, the warning triggers at this level. void f (char *s) { if (!s) { char a[12] = "tmpname"; s = a; } // warning: dangling pointer to a may be used strcat (s, ".tmp"); ... } -Wdangling-pointer=2 is included in -Wall. -Wdate-time Warn when macros "__TIME__", "__DATE__" or "__TIMESTAMP__" are encountered as they might prevent bit-wise-identical reproducible compilations. -Wempty-body Warn if an empty body occurs in an "if", "else" or "do while" statement. This warning is also enabled by -Wextra. -Wno-endif-labels Do not warn about stray tokens after "#else" and "#endif". -Wenum-compare Warn about a comparison between values of different enumerated types. In C++ enumerated type mismatches in conditional expressions are also diagnosed and the warning is enabled by default. In C this warning is enabled by -Wall. -Wenum-conversion Warn when a value of enumerated type is implicitly converted to a different enumerated type. This warning is enabled by -Wextra in C. -Wenum-int-mismatch (C and Objective-C only) Warn about mismatches between an enumerated type and an integer type in declarations. For example: enum E { l = -1, z = 0, g = 1 }; int foo(void); enum E foo(void); In C, an enumerated type is compatible with "char", a signed integer type, or an unsigned integer type. However, since the choice of the underlying type of an enumerated type is implementation-defined, such mismatches may cause portability issues. In C++, such mismatches are an error. In C, this warning is enabled by -Wall and -Wc++-compat. -Wjump-misses-init (C, Objective-C only) Warn if a "goto" statement or a "switch" statement jumps forward across the initialization of a variable, or jumps backward to a label after the variable has been initialized. This only warns about variables that are initialized when they are declared. This warning is only supported for C and Objective-C; in C++ this sort of branch is an error in any case. -Wjump-misses-init is included in -Wc++-compat. It can be disabled with the -Wno-jump-misses-init option. -Wsign-compare Warn when a comparison between signed and unsigned values could produce an incorrect result when the signed value is converted to unsigned. In C++, this warning is also enabled by -Wall. In C, it is also enabled by -Wextra. -Wsign-conversion Warn for implicit conversions that may change the sign of an integer value, like assigning a signed integer expression to an unsigned integer variable. An explicit cast silences the warning. In C, this option is enabled also by -Wconversion. -Wfloat-conversion Warn for implicit conversions that reduce the precision of a real value. This includes conversions from real to integer, and from higher precision real to lower precision real values. This option is also enabled by -Wconversion. -Wno-scalar-storage-order Do not warn on suspicious constructs involving reverse scalar storage order. -Wsizeof-array-div Warn about divisions of two sizeof operators when the first one is applied to an array and the divisor does not equal the size of the array element. In such a case, the computation will not yield the number of elements in the array, which is likely what the user intended. This warning warns e.g. about int fn () { int arr[10]; return sizeof (arr) / sizeof (short); } This warning is enabled by -Wall. -Wsizeof-pointer-div Warn for suspicious divisions of two sizeof expressions that divide the pointer size by the element size, which is the usual way to compute the array size but won't work out correctly with pointers. This warning warns e.g. about "sizeof (ptr) / sizeof (ptr[0])" if "ptr" is not an array, but a pointer. This warning is enabled by -Wall. -Wsizeof-pointer-memaccess Warn for suspicious length parameters to certain string and memory built-in functions if the argument uses "sizeof". This warning triggers for example for "memset (ptr, 0, sizeof (ptr));" if "ptr" is not an array, but a pointer, and suggests a possible fix, or about "memcpy (&foo, ptr, sizeof (&foo));". -Wsizeof-pointer-memaccess also warns about calls to bounded string copy functions like "strncat" or "strncpy" that specify as the bound a "sizeof" expression of the source array. For example, in the following function the call to "strncat" specifies the size of the source string as the bound. That is almost certainly a mistake and so the call is diagnosed. void make_file (const char *name) { char path[PATH_MAX]; strncpy (path, name, sizeof path - 1); strncat (path, ".text", sizeof ".text"); ... } The -Wsizeof-pointer-memaccess option is enabled by -Wall. -Wno-sizeof-array-argument Do not warn when the "sizeof" operator is applied to a parameter that is declared as an array in a function definition. This warning is enabled by default for C and C++ programs. -Wmemset-elt-size Warn for suspicious calls to the "memset" built-in function, if the first argument references an array, and the third argument is a number equal to the number of elements, but not equal to the size of the array in memory. This indicates that the user has omitted a multiplication by the element size. This warning is enabled by -Wall. -Wmemset-transposed-args Warn for suspicious calls to the "memset" built-in function where the second argument is not zero and the third argument is zero. For example, the call "memset (buf, sizeof buf, 0)" is diagnosed because "memset (buf, 0, sizeof buf)" was meant instead. The diagnostic is only emitted if the third argument is a literal zero. Otherwise, if it is an expression that is folded to zero, or a cast of zero to some type, it is far less likely that the arguments have been mistakenly transposed and no warning is emitted. This warning is enabled by -Wall. -Waddress Warn about suspicious uses of address expressions. These include comparing the address of a function or a declared object to the null pointer constant such as in void f (void); void g (void) { if (!f) // warning: expression evaluates to false abort (); } comparisons of a pointer to a string literal, such as in void f (const char *x) { if (x == "abc") // warning: expression evaluates to false puts ("equal"); } and tests of the results of pointer addition or subtraction for equality to null, such as in void f (const int *p, int i) { return p + i == NULL; } Such uses typically indicate a programmer error: the address of most functions and objects necessarily evaluates to true (the exception are weak symbols), so their use in a conditional might indicate missing parentheses in a function call or a missing dereference in an array expression. The subset of the warning for object pointers can be suppressed by casting the pointer operand to an integer type such as "intptr_t" or "uintptr_t". Comparisons against string literals result in unspecified behavior and are not portable, and suggest the intent was to call "strcmp". The warning is suppressed if the suspicious expression is the result of macro expansion. -Waddress warning is enabled by -Wall. -Wno-address-of-packed-member Do not warn when the address of packed member of struct or union is taken, which usually results in an unaligned pointer value. This is enabled by default. -Wlogical-op Warn about suspicious uses of logical operators in expressions. This includes using logical operators in contexts where a bit-wise operator is likely to be expected. Also warns when the operands of a logical operator are the same: extern int a; if (a < 0 && a < 0) { ... } -Wlogical-not-parentheses Warn about logical not used on the left hand side operand of a comparison. This option does not warn if the right operand is considered to be a boolean expression. Its purpose is to detect suspicious code like the following: int a; ... if (!a > 1) { ... } It is possible to suppress the warning by wrapping the LHS into parentheses: if ((!a) > 1) { ... } This warning is enabled by -Wall. -Waggregate-return Warn if any functions that return structures or unions are defined or called. (In languages where you can return an array, this also elicits a warning.) -Wno-aggressive-loop-optimizations Warn if in a loop with constant number of iterations the compiler detects undefined behavior in some statement during one or more of the iterations. -Wno-attributes Do not warn if an unexpected "__attribute__" is used, such as unrecognized attributes, function attributes applied to variables, etc. This does not stop errors for incorrect use of supported attributes. Additionally, using -Wno-attributes=, it is possible to suppress warnings about unknown scoped attributes (in C++11 and C2X). For example, -Wno-attributes=vendor::attr disables warning about the following declaration: [[vendor::attr]] void f(); It is also possible to disable warning about all attributes in a namespace using -Wno-attributes=vendor:: which prevents warning about both of these declarations: [[vendor::safe]] void f(); [[vendor::unsafe]] void f2(); Note that -Wno-attributes= does not imply -Wno-attributes. -Wno-builtin-declaration-mismatch Warn if a built-in function is declared with an incompatible signature or as a non-function, or when a built-in function declared with a type that does not include a prototype is called with arguments whose promoted types do not match those expected by the function. When -Wextra is specified, also warn when a built-in function that takes arguments is declared without a prototype. The -Wbuiltin-declaration-mismatch warning is enabled by default. To avoid the warning include the appropriate header to bring the prototypes of built-in functions into scope. For example, the call to "memset" below is diagnosed by the warning because the function expects a value of type "size_t" as its argument but the type of 32 is "int". With -Wextra, the declaration of the function is diagnosed as well. extern void* memset (); void f (void *d) { memset (d, '\0', 32); } -Wno-builtin-macro-redefined Do not warn if certain built-in macros are redefined. This suppresses warnings for redefinition of "__TIMESTAMP__", "__TIME__", "__DATE__", "__FILE__", and "__BASE_FILE__". -Wstrict-prototypes (C and Objective-C only) Warn if a function is declared or defined without specifying the argument types. (An old-style function definition is permitted without a warning if preceded by a declaration that specifies the argument types.) -Wold-style-declaration (C and Objective-C only) Warn for obsolescent usages, according to the C Standard, in a declaration. For example, warn if storage-class specifiers like "static" are not the first things in a declaration. This warning is also enabled by -Wextra. -Wold-style-definition (C and Objective-C only) Warn if an old-style function definition is used. A warning is given even if there is a previous prototype. A definition using () is not considered an old-style definition in C2X mode, because it is equivalent to (void) in that case, but is considered an old- style definition for older standards. -Wmissing-parameter-type (C and Objective-C only) A function parameter is declared without a type specifier in K&R-style functions: void foo(bar) { } This warning is also enabled by -Wextra. -Wmissing-prototypes (C and Objective-C only) Warn if a global function is defined without a previous prototype declaration. This warning is issued even if the definition itself provides a prototype. Use this option to detect global functions that do not have a matching prototype declaration in a header file. This option is not valid for C++ because all function declarations provide prototypes and a non-matching declaration declares an overload rather than conflict with an earlier declaration. Use -Wmissing-declarations to detect missing declarations in C++. -Wmissing-declarations Warn if a global function is defined without a previous declaration. Do so even if the definition itself provides a prototype. Use this option to detect global functions that are not declared in header files. In C, no warnings are issued for functions with previous non-prototype declarations; use -Wmissing-prototypes to detect missing prototypes. In C++, no warnings are issued for function templates, or for inline functions, or for functions in anonymous namespaces. -Wmissing-field-initializers Warn if a structure's initializer has some fields missing. For example, the following code causes such a warning, because "x.h" is implicitly zero: struct s { int f, g, h; }; struct s x = { 3, 4 }; This option does not warn about designated initializers, so the following modification does not trigger a warning: struct s { int f, g, h; }; struct s x = { .f = 3, .g = 4 }; In C this option does not warn about the universal zero initializer { 0 }: struct s { int f, g, h; }; struct s x = { 0 }; Likewise, in C++ this option does not warn about the empty { } initializer, for example: struct s { int f, g, h; }; s x = { }; This warning is included in -Wextra. To get other -Wextra warnings without this one, use -Wextra -Wno-missing-field-initializers. -Wno-missing-requires By default, the compiler warns about a concept-id appearing as a C++20 simple-requirement: bool satisfied = requires { C<T> }; Here satisfied will be true if C<T> is a valid expression, which it is for all T. Presumably the user meant to write bool satisfied = requires { requires C<T> }; so satisfied is only true if concept C is satisfied for type T. This warning can be disabled with -Wno-missing-requires. -Wno-missing-template-keyword The member access tokens ., -> and :: must be followed by the "template" keyword if the parent object is dependent and the member being named is a template. template <class X> void DoStuff (X x) { x.template DoSomeOtherStuff<X>(); // Good. x.DoMoreStuff<X>(); // Warning, x is dependent. } In rare cases it is possible to get false positives. To silence this, wrap the expression in parentheses. For example, the following is treated as a template, even where m and N are integers: void NotATemplate (my_class t) { int N = 5; bool test = t.m < N > (0); // Treated as a template. test = (t.m < N) > (0); // Same meaning, but not treated as a template. } This warning can be disabled with -Wno-missing-template-keyword. -Wno-multichar Do not warn if a multicharacter constant ('FOOF') is used. Usually they indicate a typo in the user's code, as they have implementation-defined values, and should not be used in portable code. -Wnormalized=[none|id|nfc|nfkc] In ISO C and ISO C++, two identifiers are different if they are different sequences of characters. However, sometimes when characters outside the basic ASCII character set are used, you can have two different character sequences that look the same. To avoid confusion, the ISO 10646 standard sets out some normalization rules which when applied ensure that two sequences that look the same are turned into the same sequence. GCC can warn you if you are using identifiers that have not been normalized; this option controls that warning. There are four levels of warning supported by GCC. The default is -Wnormalized=nfc, which warns about any identifier that is not in the ISO 10646 "C" normalized form, NFC. NFC is the recommended form for most uses. It is equivalent to -Wnormalized. Unfortunately, there are some characters allowed in identifiers by ISO C and ISO C++ that, when turned into NFC, are not allowed in identifiers. That is, there's no way to use these symbols in portable ISO C or C++ and have all your identifiers in NFC. -Wnormalized=id suppresses the warning for these characters. It is hoped that future versions of the standards involved will correct this, which is why this option is not the default. You can switch the warning off for all characters by writing -Wnormalized=none or -Wno-normalized. You should only do this if you are using some other normalization scheme (like "D"), because otherwise you can easily create bugs that are literally impossible to see. Some characters in ISO 10646 have distinct meanings but look identical in some fonts or display methodologies, especially once formatting has been applied. For instance "\u207F", "SUPERSCRIPT LATIN SMALL LETTER N", displays just like a regular "n" that has been placed in a superscript. ISO 10646 defines the NFKC normalization scheme to convert all these into a standard form as well, and GCC warns if your code is not in NFKC if you use -Wnormalized=nfkc. This warning is comparable to warning about every identifier that contains the letter O because it might be confused with the digit 0, and so is not the default, but may be useful as a local coding convention if the programming environment cannot be fixed to display these characters distinctly. -Wno-attribute-warning Do not warn about usage of functions declared with "warning" attribute. By default, this warning is enabled. -Wno-attribute-warning can be used to disable the warning or -Wno-error=attribute-warning can be used to disable the error when compiled with -Werror flag. -Wno-deprecated Do not warn about usage of deprecated features. -Wno-deprecated-declarations Do not warn about uses of functions, variables, and types marked as deprecated by using the "deprecated" attribute. -Wno-overflow Do not warn about compile-time overflow in constant expressions. -Wno-odr Warn about One Definition Rule violations during link-time optimization. Enabled by default. -Wopenacc-parallelism Warn about potentially suboptimal choices related to OpenACC parallelism. -Wopenmp-simd Warn if the vectorizer cost model overrides the OpenMP simd directive set by user. The -fsimd-cost-model=unlimited option can be used to relax the cost model. -Woverride-init (C and Objective-C only) Warn if an initialized field without side effects is overridden when using designated initializers. This warning is included in -Wextra. To get other -Wextra warnings without this one, use -Wextra -Wno-override-init. -Wno-override-init-side-effects (C and Objective-C only) Do not warn if an initialized field with side effects is overridden when using designated initializers. This warning is enabled by default. -Wpacked Warn if a structure is given the packed attribute, but the packed attribute has no effect on the layout or size of the structure. Such structures may be mis-aligned for little benefit. For instance, in this code, the variable "f.x" in "struct bar" is misaligned even though "struct bar" does not itself have the packed attribute: struct foo { int x; char a, b, c, d; } __attribute__((packed)); struct bar { char z; struct foo f; }; -Wnopacked-bitfield-compat The 4.1, 4.2 and 4.3 series of GCC ignore the "packed" attribute on bit-fields of type "char". This was fixed in GCC 4.4 but the change can lead to differences in the structure layout. GCC informs you when the offset of such a field has changed in GCC 4.4. For example there is no longer a 4-bit padding between field "a" and "b" in this structure: struct foo { char a:4; char b:8; } __attribute__ ((packed)); This warning is enabled by default. Use -Wno-packed-bitfield-compat to disable this warning. -Wpacked-not-aligned (C, C++, Objective-C and Objective-C++ only) Warn if a structure field with explicitly specified alignment in a packed struct or union is misaligned. For example, a warning will be issued on "struct S", like, "warning: alignment 1 of 'struct S' is less than 8", in this code: struct __attribute__ ((aligned (8))) S8 { char a[8]; }; struct __attribute__ ((packed)) S { struct S8 s8; }; This warning is enabled by -Wall. -Wpadded Warn if padding is included in a structure, either to align an element of the structure or to align the whole structure. Sometimes when this happens it is possible to rearrange the fields of the structure to reduce the padding and so make the structure smaller. -Wredundant-decls Warn if anything is declared more than once in the same scope, even in cases where multiple declaration is valid and changes nothing. -Wrestrict Warn when an object referenced by a "restrict"-qualified parameter (or, in C++, a "__restrict"-qualified parameter) is aliased by another argument, or when copies between such objects overlap. For example, the call to the "strcpy" function below attempts to truncate the string by replacing its initial characters with the last four. However, because the call writes the terminating NUL into "a[4]", the copies overlap and the call is diagnosed. void foo (void) { char a[] = "abcd1234"; strcpy (a, a + 4); ... } The -Wrestrict option detects some instances of simple overlap even without optimization but works best at -O2 and above. It is included in -Wall. -Wnested-externs (C and Objective-C only) Warn if an "extern" declaration is encountered within a function. -Winline Warn if a function that is declared as inline cannot be inlined. Even with this option, the compiler does not warn about failures to inline functions declared in system headers. The compiler uses a variety of heuristics to determine whether or not to inline a function. For example, the compiler takes into account the size of the function being inlined and the amount of inlining that has already been done in the current function. Therefore, seemingly insignificant changes in the source program can cause the warnings produced by -Winline to appear or disappear. -Winterference-size Warn about use of C++17 "std::hardware_destructive_interference_size" without specifying its value with --param destructive-interference-size. Also warn about questionable values for that option. This variable is intended to be used for controlling class layout, to avoid false sharing in concurrent code: struct independent_fields { alignas(std::hardware_destructive_interference_size) std::atomic<int> one; alignas(std::hardware_destructive_interference_size) std::atomic<int> two; }; Here one and two are intended to be far enough apart that stores to one won't require accesses to the other to reload the cache line. By default, --param destructive-interference-size and --param constructive-interference-size are set based on the current -mtune option, typically to the L1 cache line size for the particular target CPU, sometimes to a range if tuning for a generic target. So all translation units that depend on ABI compatibility for the use of these variables must be compiled with the same -mtune (or -mcpu). If ABI stability is important, such as if the use is in a header for a library, you should probably not use the hardware interference size variables at all. Alternatively, you can force a particular value with --param. If you are confident that your use of the variable does not affect ABI outside a single build of your project, you can turn off the warning with -Wno-interference-size. -Wint-in-bool-context Warn for suspicious use of integer values where boolean values are expected, such as conditional expressions (?:) using non-boolean integer constants in boolean context, like "if (a <= b ? 2 : 3)". Or left shifting of signed integers in boolean context, like "for (a = 0; 1 << a; a++);". Likewise for all kinds of multiplications regardless of the data type. This warning is enabled by -Wall. -Wno-int-to-pointer-cast Suppress warnings from casts to pointer type of an integer of a different size. In C++, casting to a pointer type of smaller size is an error. Wint-to-pointer-cast is enabled by default. -Wno-pointer-to-int-cast (C and Objective-C only) Suppress warnings from casts from a pointer to an integer type of a different size. -Winvalid-pch Warn if a precompiled header is found in the search path but cannot be used. -Winvalid-utf8 Warn if an invalid UTF-8 character is found. This warning is on by default for C++23 if -finput-charset=UTF-8 is used and turned into error with -pedantic-errors. -Wno-unicode Don't diagnose invalid forms of delimited or named escape sequences which are treated as separate tokens. Wunicode is enabled by default. -Wlong-long Warn if "long long" type is used. This is enabled by either -Wpedantic or -Wtraditional in ISO C90 and C++98 modes. To inhibit the warning messages, use -Wno-long-long. -Wvariadic-macros Warn if variadic macros are used in ISO C90 mode, or if the GNU alternate syntax is used in ISO C99 mode. This is enabled by either -Wpedantic or -Wtraditional. To inhibit the warning messages, use -Wno-variadic-macros. -Wno-varargs Do not warn upon questionable usage of the macros used to handle variable arguments like "va_start". These warnings are enabled by default. -Wvector-operation-performance Warn if vector operation is not implemented via SIMD capabilities of the architecture. Mainly useful for the performance tuning. Vector operation can be implemented "piecewise", which means that the scalar operation is performed on every vector element; "in parallel", which means that the vector operation is implemented using scalars of wider type, which normally is more performance efficient; and "as a single scalar", which means that vector fits into a scalar type. -Wvla Warn if a variable-length array is used in the code. -Wno-vla prevents the -Wpedantic warning of the variable-length array. -Wvla-larger-than=byte-size If this option is used, the compiler warns for declarations of variable-length arrays whose size is either unbounded, or bounded by an argument that allows the array size to exceed byte-size bytes. This is similar to how -Walloca-larger-than=byte-size works, but with variable-length arrays. Note that GCC may optimize small variable-length arrays of a known value into plain arrays, so this warning may not get triggered for such arrays. -Wvla-larger-than=PTRDIFF_MAX is enabled by default but is typically only effective when -ftree-vrp is active (default for -O2 and above). See also -Walloca-larger-than=byte-size. -Wno-vla-larger-than Disable -Wvla-larger-than= warnings. The option is equivalent to -Wvla-larger-than=SIZE_MAX or larger. -Wvla-parameter Warn about redeclarations of functions involving arguments of Variable Length Array types of inconsistent kinds or forms, and enable the detection of out-of-bounds accesses to such parameters by warnings such as -Warray-bounds. If the first function declaration uses the VLA form the bound specified in the array is assumed to be the minimum number of elements expected to be provided in calls to the function and the maximum number of elements accessed by it. Failing to provide arguments of sufficient size or accessing more than the maximum number of elements may be diagnosed. For example, the warning triggers for the following redeclarations because the first one allows an array of any size to be passed to "f" while the second one specifies that the array argument must have at least "n" elements. In addition, calling "f" with the associated VLA bound parameter in excess of the actual VLA bound triggers a warning as well. void f (int n, int[n]); // warning: argument 2 previously declared as a VLA void f (int, int[]); void g (int n) { if (n > 4) return; int a[n]; // warning: access to a by f may be out of bounds f (sizeof a, a); ... } -Wvla-parameter is included in -Wall. The -Warray-parameter option triggers warnings for similar problems involving ordinary array arguments. -Wvolatile-register-var Warn if a register variable is declared volatile. The volatile modifier does not inhibit all optimizations that may eliminate reads and/or writes to register variables. This warning is enabled by -Wall. -Wxor-used-as-pow (C, C++, Objective-C and Objective-C++ only) Warn about uses of "^", the exclusive or operator, where it appears the user meant exponentiation. Specifically, the warning occurs when the left-hand side is the decimal constant 2 or 10 and the right-hand side is also a decimal constant. In C and C++, "^" means exclusive or, whereas in some other languages (e.g. TeX and some versions of BASIC) it means exponentiation. This warning is enabled by default. It can be silenced by converting one of the operands to hexadecimal. -Wdisabled-optimization Warn if a requested optimization pass is disabled. This warning does not generally indicate that there is anything wrong with your code; it merely indicates that GCC's optimizers are unable to handle the code effectively. Often, the problem is that your code is too big or too complex; GCC refuses to optimize programs when the optimization itself is likely to take inordinate amounts of time. -Wpointer-sign (C and Objective-C only) Warn for pointer argument passing or assignment with different signedness. This option is only supported for C and Objective-C. It is implied by -Wall and by -Wpedantic, which can be disabled with -Wno-pointer-sign. -Wstack-protector This option is only active when -fstack-protector is active. It warns about functions that are not protected against stack smashing. -Woverlength-strings Warn about string constants that are longer than the "minimum maximum" length specified in the C standard. Modern compilers generally allow string constants that are much longer than the standard's minimum limit, but very portable programs should avoid using longer strings. The limit applies after string constant concatenation, and does not count the trailing NUL. In C90, the limit was 509 characters; in C99, it was raised to 4095. C++98 does not specify a normative minimum maximum, so we do not diagnose overlength strings in C++. This option is implied by -Wpedantic, and can be disabled with -Wno-overlength-strings. -Wunsuffixed-float-constants (C and Objective-C only) Issue a warning for any floating constant that does not have a suffix. When used together with -Wsystem-headers it warns about such constants in system header files. This can be useful when preparing code to use with the "FLOAT_CONST_DECIMAL64" pragma from the decimal floating-point extension to C99. -Wno-lto-type-mismatch During the link-time optimization, do not warn about type mismatches in global declarations from different compilation units. Requires -flto to be enabled. Enabled by default. -Wno-designated-init (C and Objective-C only) Suppress warnings when a positional initializer is used to initialize a structure that has been marked with the "designated_init" attribute. Options That Control Static Analysis -fanalyzer This option enables an static analysis of program flow which looks for "interesting" interprocedural paths through the code, and issues warnings for problems found on them. This analysis is much more expensive than other GCC warnings. In technical terms, it performs coverage-guided symbolic execution of the code being compiled. It is neither sound nor complete: it can have false positives and false negatives. It is a bug-finding tool, rather than a tool for proving program correctness. The analyzer is only suitable for use on C code in this release. Enabling this option effectively enables the following warnings: -Wanalyzer-allocation-size -Wanalyzer-deref-before-check -Wanalyzer-double-fclose -Wanalyzer-double-free -Wanalyzer-exposure-through-output-file -Wanalyzer-exposure-through-uninit-copy -Wanalyzer-fd-access-mode-mismatch -Wanalyzer-fd-double-close -Wanalyzer-fd-leak -Wanalyzer-fd-phase-mismatch -Wanalyzer-fd-type-mismatch -Wanalyzer-fd-use-after-close -Wanalyzer-fd-use-without-check -Wanalyzer-file-leak -Wanalyzer-free-of-non-heap -Wanalyzer-imprecise-fp-arithmetic -Wanalyzer-infinite-recursion -Wanalyzer-jump-through-null -Wanalyzer-malloc-leak -Wanalyzer-mismatching-deallocation -Wanalyzer-null-argument -Wanalyzer-null-dereference -Wanalyzer-out-of-bounds -Wanalyzer-possible-null-argument -Wanalyzer-possible-null-dereference -Wanalyzer-putenv-of-auto-var -Wanalyzer-shift-count-negative -Wanalyzer-shift-count-overflow -Wanalyzer-stale-setjmp-buffer -Wanalyzer-unsafe-call-within-signal-handler -Wanalyzer-use-after-free -Wanalyzer-use-of-pointer-in-stale-stack-frame -Wanalyzer-use-of-uninitialized-value -Wanalyzer-va-arg-type-mismatch -Wanalyzer-va-list-exhausted -Wanalyzer-va-list-leak -Wanalyzer-va-list-use-after-va-end -Wanalyzer-write-to-const -Wanalyzer-write-to-string-literal This option is only available if GCC was configured with analyzer support enabled. -Wanalyzer-too-complex If -fanalyzer is enabled, the analyzer uses various heuristics to attempt to explore the control flow and data flow in the program, but these can be defeated by sufficiently complicated code. By default, the analysis silently stops if the code is too complicated for the analyzer to fully explore and it reaches an internal limit. The -Wanalyzer-too-complex option warns if this occurs. -Wno-analyzer-allocation-size This warning requires -fanalyzer, which enables it; to disable it, use -Wno-analyzer-allocation-size. This diagnostic warns for paths through the code in which a pointer to a buffer is assigned to point at a buffer with a size that is not a multiple of "sizeof (*pointer)". See CWE-131: Incorrect Calculation of Buffer Size ("https://cwe.mitre.org/data/definitions/131.html"). -Wno-analyzer-deref-before-check This warning requires -fanalyzer, which enables it; use -Wno-analyzer-deref-before-check to disable it. This diagnostic warns for paths through the code in which a pointer is checked for "NULL" *after* it has already been dereferenced, suggesting that the pointer could have been NULL. Such cases suggest that the check for NULL is either redundant, or that it needs to be moved to before the pointer is dereferenced. This diagnostic also considers values passed to a function argument marked with "__attribute__((nonnull))" as requiring a non-NULL value, and thus will complain if such values are checked for "NULL" after returning from such a function call. This diagnostic is unlikely to be reported when any level of optimization is enabled, as GCC's optimization logic will typically consider such checks for NULL as being redundant, and optimize them away before the analyzer "sees" them. Hence optimization should be disabled when attempting to trigger this diagnostic. -Wno-analyzer-double-fclose This warning requires -fanalyzer, which enables it; use -Wno-analyzer-double-fclose to disable it. This diagnostic warns for paths through the code in which a "FILE *" can have "fclose" called on it more than once. See CWE-1341: Multiple Releases of Same Resource or Handle ("https://cwe.mitre.org/data/definitions/1341.html"). -Wno-analyzer-double-free This warning requires -fanalyzer, which enables it; use -Wno-analyzer-double-free to disable it. This diagnostic warns for paths through the code in which a pointer can have a deallocator called on it more than once, either "free", or a deallocator referenced by attribute "malloc". See CWE-415: Double Free ("https://cwe.mitre.org/data/definitions/415.html"). -Wno-analyzer-exposure-through-output-file This warning requires -fanalyzer, which enables it; use -Wno-analyzer-exposure-through-output-file to disable it. This diagnostic warns for paths through the code in which a security-sensitive value is written to an output file (such as writing a password to a log file). See CWE-532: Information Exposure Through Log Files ("https://cwe.mitre.org/data/definitions/532.html"). -Wanalyzer-exposure-through-uninit-copy This warning requires both -fanalyzer and the use of a plugin to specify a function that copies across a "trust boundary". Use -Wno-analyzer-exposure-through-uninit-copy to disable it. This diagnostic warns for "infoleaks" - paths through the code in which uninitialized values are copied across a security boundary (such as code within an OS kernel that copies a partially- initialized struct on the stack to user space). See CWE-200: Exposure of Sensitive Information to an Unauthorized Actor ("https://cwe.mitre.org/data/definitions/200.html"). -Wno-analyzer-fd-access-mode-mismatch This warning requires -fanalyzer, which enables it; use -Wno-analyzer-fd-access-mode-mismatch to disable it. This diagnostic warns for paths through code in which a "read" on a write-only file descriptor is attempted, or vice versa. This diagnostic also warns for code paths in a which a function with attribute "fd_arg_read (N)" is called with a file descriptor opened with "O_WRONLY" at referenced argument "N" or a function with attribute "fd_arg_write (N)" is called with a file descriptor opened with "O_RDONLY" at referenced argument N. -Wno-analyzer-fd-double-close This warning requires -fanalyzer, which enables it; use -Wno-analyzer-fd-double-close to disable it. This diagnostic warns for paths through code in which a file descriptor can be closed more than once. See CWE-1341: Multiple Releases of Same Resource or Handle ("https://cwe.mitre.org/data/definitions/1341.html"). -Wno-analyzer-fd-leak This warning requires -fanalyzer, which enables it; use -Wno-analyzer-fd-leak to disable it. This diagnostic warns for paths through code in which an open file descriptor is leaked. See CWE-775: Missing Release of File Descriptor or Handle after Effective Lifetime ("https://cwe.mitre.org/data/definitions/775.html"). -Wno-analyzer-fd-phase-mismatch This warning requires -fanalyzer, which enables it; use -Wno-analyzer-fd-phase-mismatch to disable it. This diagnostic warns for paths through code in which an operation is attempted in the wrong phase of a file descriptor's lifetime. For example, it will warn on attempts to call "accept" on a stream socket that has not yet had "listen" successfully called on it. See CWE-666: Operation on Resource in Wrong Phase of Lifetime ("https://cwe.mitre.org/data/definitions/666.html"). -Wno-analyzer-fd-type-mismatch This warning requires -fanalyzer, which enables it; use -Wno-analyzer-fd-type-mismatch to disable it. This diagnostic warns for paths through code in which an operation is attempted on the wrong type of file descriptor. For example, it will warn on attempts to use socket operations on a file descriptor obtained via "open", or when attempting to use a stream socket operation on a datagram socket. -Wno-analyzer-fd-use-after-close This warning requires -fanalyzer, which enables it; use -Wno-analyzer-fd-use-after-close to disable it. This diagnostic warns for paths through code in which a read or write is called on a closed file descriptor. This diagnostic also warns for paths through code in which a function with attribute "fd_arg (N)" or "fd_arg_read (N)" or "fd_arg_write (N)" is called with a closed file descriptor at referenced argument "N". -Wno-analyzer-fd-use-without-check This warning requires -fanalyzer, which enables it; use -Wno-analyzer-fd-use-without-check to disable it. This diagnostic warns for paths through code in which a file descriptor is used without being checked for validity. This diagnostic also warns for paths through code in which a function with attribute "fd_arg (N)" or "fd_arg_read (N)" or "fd_arg_write (N)" is called with a file descriptor, at referenced argument "N", without being checked for validity. -Wno-analyzer-file-leak This warning requires -fanalyzer, which enables it; use -Wno-analyzer-file-leak to disable it. This diagnostic warns for paths through the code in which a "<stdio.h>" "FILE *" stream object is leaked. See CWE-775: Missing Release of File Descriptor or Handle after Effective Lifetime ("https://cwe.mitre.org/data/definitions/775.html"). -Wno-analyzer-free-of-non-heap This warning requires -fanalyzer, which enables it; use -Wno-analyzer-free-of-non-heap to disable it. This diagnostic warns for paths through the code in which "free" is called on a non-heap pointer (e.g. an on-stack buffer, or a global). See CWE-590: Free of Memory not on the Heap ("https://cwe.mitre.org/data/definitions/590.html"). -Wno-analyzer-imprecise-fp-arithmetic This warning requires -fanalyzer, which enables it; use -Wno-analyzer-imprecise-fp-arithmetic to disable it. This diagnostic warns for paths through the code in which floating- point arithmetic is used in locations where precise computation is needed. This diagnostic only warns on use of floating-point operands inside the calculation of an allocation size at the moment. -Wno-analyzer-infinite-recursion This warning requires -fanalyzer, which enables it; use -Wno-analyzer-infinite-recursion to disable it. This diagnostics warns for paths through the code which appear to lead to infinite recursion. Specifically, when the analyzer "sees" a recursive call, it will compare the state of memory at the entry to the new frame with that at the entry to the previous frame of that function on the stack. The warning is issued if nothing in memory appears to be changing; any changes observed to parameters or globals are assumed to lead to termination of the recursion and thus suppress the warning. This diagnostic is likely to miss cases of infinite recursion that are convered to iteration by the optimizer before the analyzer "sees" them. Hence optimization should be disabled when attempting to trigger this diagnostic. Compare with -Winfinite-recursion, which provides a similar diagnostic, but is implemented in a different way. -Wno-analyzer-jump-through-null This warning requires -fanalyzer, which enables it; use -Wno-analyzer-jump-through-null to disable it. This diagnostic warns for paths through the code in which a "NULL" function pointer is called. -Wno-analyzer-malloc-leak This warning requires -fanalyzer, which enables it; use -Wno-analyzer-malloc-leak to disable it. This diagnostic warns for paths through the code in which a pointer allocated via an allocator is leaked: either "malloc", or a function marked with attribute "malloc". See CWE-401: Missing Release of Memory after Effective Lifetime ("https://cwe.mitre.org/data/definitions/401.html"). -Wno-analyzer-mismatching-deallocation This warning requires -fanalyzer, which enables it; use -Wno-analyzer-mismatching-deallocation to disable it. This diagnostic warns for paths through the code in which the wrong deallocation function is called on a pointer value, based on which function was used to allocate the pointer value. The diagnostic will warn about mismatches between "free", scalar "delete" and vector "delete[]", and those marked as allocator/deallocator pairs using attribute "malloc". See CWE-762: Mismatched Memory Management Routines ("https://cwe.mitre.org/data/definitions/762.html"). -Wno-analyzer-out-of-bounds This warning requires -fanalyzer, which enables it; use -Wno-analyzer-out-of-bounds to disable it. This diagnostic warns for paths through the code in which a buffer is definitely read or written out-of-bounds. The diagnostic applies for cases where the analyzer is able to determine a constant offset and for accesses past the end of a buffer, also a constant capacity. Further, the diagnostic does limited checking for accesses past the end when the offset as well as the capacity is symbolic. See CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer ("https://cwe.mitre.org/data/definitions/119.html"). -Wno-analyzer-possible-null-argument This warning requires -fanalyzer, which enables it; use -Wno-analyzer-possible-null-argument to disable it. This diagnostic warns for paths through the code in which a possibly-NULL value is passed to a function argument marked with "__attribute__((nonnull))" as requiring a non-NULL value. See CWE-690: Unchecked Return Value to NULL Pointer Dereference ("https://cwe.mitre.org/data/definitions/690.html"). -Wno-analyzer-possible-null-dereference This warning requires -fanalyzer, which enables it; use -Wno-analyzer-possible-null-dereference to disable it. This diagnostic warns for paths through the code in which a possibly-NULL value is dereferenced. See CWE-690: Unchecked Return Value to NULL Pointer Dereference ("https://cwe.mitre.org/data/definitions/690.html"). -Wno-analyzer-null-argument This warning requires -fanalyzer, which enables it; use -Wno-analyzer-null-argument to disable it. This diagnostic warns for paths through the code in which a value known to be NULL is passed to a function argument marked with "__attribute__((nonnull))" as requiring a non-NULL value. See CWE-476: NULL Pointer Dereference ("https://cwe.mitre.org/data/definitions/476.html"). -Wno-analyzer-null-dereference This warning requires -fanalyzer, which enables it; use -Wno-analyzer-null-dereference to disable it. This diagnostic warns for paths through the code in which a value known to be NULL is dereferenced. See CWE-476: NULL Pointer Dereference ("https://cwe.mitre.org/data/definitions/476.html"). -Wno-analyzer-putenv-of-auto-var This warning requires -fanalyzer, which enables it; use -Wno-analyzer-putenv-of-auto-var to disable it. This diagnostic warns for paths through the code in which a call to "putenv" is passed a pointer to an automatic variable or an on- stack buffer. See POS34-C. Do not call putenv() with a pointer to an automatic variable as the argument ("https://wiki.sei.cmu.edu/confluence/x/6NYxBQ"). -Wno-analyzer-shift-count-negative This warning requires -fanalyzer, which enables it; use -Wno-analyzer-shift-count-negative to disable it. This diagnostic warns for paths through the code in which a shift is attempted with a negative count. It is analogous to the -Wshift-count-negative diagnostic implemented in the C/C++ front ends, but is implemented based on analyzing interprocedural paths, rather than merely parsing the syntax tree. However, the analyzer does not prioritize detection of such paths, so false negatives are more likely relative to other warnings. -Wno-analyzer-shift-count-overflow This warning requires -fanalyzer, which enables it; use -Wno-analyzer-shift-count-overflow to disable it. This diagnostic warns for paths through the code in which a shift is attempted with a count greater than or equal to the precision of the operand's type. It is analogous to the -Wshift-count-overflow diagnostic implemented in the C/C++ front ends, but is implemented based on analyzing interprocedural paths, rather than merely parsing the syntax tree. However, the analyzer does not prioritize detection of such paths, so false negatives are more likely relative to other warnings. -Wno-analyzer-stale-setjmp-buffer This warning requires -fanalyzer, which enables it; use -Wno-analyzer-stale-setjmp-buffer to disable it. This diagnostic warns for paths through the code in which "longjmp" is called to rewind to a "jmp_buf" relating to a "setjmp" call in a function that has returned. When "setjmp" is called on a "jmp_buf" to record a rewind location, it records the stack frame. The stack frame becomes invalid when the function containing the "setjmp" call returns. Attempting to rewind to it via "longjmp" would reference a stack frame that no longer exists, and likely lead to a crash (or worse). -Wno-analyzer-tainted-allocation-size This warning requires both -fanalyzer and -fanalyzer-checker=taint to enable it; use -Wno-analyzer-tainted-allocation-size to disable it. This diagnostic warns for paths through the code in which a value that could be under an attacker's control is used as the size of an allocation without being sanitized, so that an attacker could inject an excessively large allocation and potentially cause a denial of service attack. See CWE-789: Memory Allocation with Excessive Size Value ("https://cwe.mitre.org/data/definitions/789.html"). -Wno-analyzer-tainted-assertion This warning requires both -fanalyzer and -fanalyzer-checker=taint to enable it; use -Wno-analyzer-tainted-assertion to disable it. This diagnostic warns for paths through the code in which a value that could be under an attacker's control is used as part of a condition without being first sanitized, and that condition guards a call to a function marked with attribute "noreturn" (such as the function "__builtin_unreachable"). Such functions typically indicate abnormal termination of the program, such as for assertion failure handlers. For example: assert (some_tainted_value < SOME_LIMIT); In such cases: * when assertion-checking is enabled: an attacker could trigger a denial of service by injecting an assertion failure * when assertion-checking is disabled, such as by defining "NDEBUG", an attacker could inject data that subverts the process, since it presumably violates a precondition that is being assumed by the code. Note that when assertion-checking is disabled, the assertions are typically removed by the preprocessor before the analyzer has a chance to "see" them, so this diagnostic can only generate warnings on builds in which assertion-checking is enabled. For the purpose of this warning, any function marked with attribute "noreturn" is considered as a possible assertion failure handler, including "__builtin_unreachable". Note that these functions are sometimes removed by the optimizer before the analyzer "sees" them. Hence optimization should be disabled when attempting to trigger this diagnostic. See CWE-617: Reachable Assertion ("https://cwe.mitre.org/data/definitions/617.html"). The warning can also report problematic constructions such as switch (some_tainted_value) { case 0: /* [...etc; various valid cases omitted...] */ break; default: __builtin_unreachable (); /* BUG: attacker can trigger this */ } despite the above not being an assertion failure, strictly speaking. -Wno-analyzer-tainted-array-index This warning requires both -fanalyzer and -fanalyzer-checker=taint to enable it; use -Wno-analyzer-tainted-array-index to disable it. This diagnostic warns for paths through the code in which a value that could be under an attacker's control is used as the index of an array access without being sanitized, so that an attacker could inject an out-of-bounds access. See CWE-129: Improper Validation of Array Index ("https://cwe.mitre.org/data/definitions/129.html"). -Wno-analyzer-tainted-divisor This warning requires both -fanalyzer and -fanalyzer-checker=taint to enable it; use -Wno-analyzer-tainted-divisor to disable it. This diagnostic warns for paths through the code in which a value that could be under an attacker's control is used as the divisor in a division or modulus operation without being sanitized, so that an attacker could inject a division-by-zero. See CWE-369: Divide By Zero ("https://cwe.mitre.org/data/definitions/369.html"). -Wno-analyzer-tainted-offset This warning requires both -fanalyzer and -fanalyzer-checker=taint to enable it; use -Wno-analyzer-tainted-offset to disable it. This diagnostic warns for paths through the code in which a value that could be under an attacker's control is used as a pointer offset without being sanitized, so that an attacker could inject an out-of-bounds access. See CWE-823: Use of Out-of-range Pointer Offset ("https://cwe.mitre.org/data/definitions/823.html"). -Wno-analyzer-tainted-size This warning requires both -fanalyzer and -fanalyzer-checker=taint to enable it; use -Wno-analyzer-tainted-size to disable it. This diagnostic warns for paths through the code in which a value that could be under an attacker's control is used as the size of an operation such as "memset" without being sanitized, so that an attacker could inject an out-of-bounds access. See CWE-129: Improper Validation of Array Index ("https://cwe.mitre.org/data/definitions/129.html"). -Wno-analyzer-unsafe-call-within-signal-handler This warning requires -fanalyzer, which enables it; use -Wno-analyzer-unsafe-call-within-signal-handler to disable it. This diagnostic warns for paths through the code in which a function known to be async-signal-unsafe (such as "fprintf") is called from a signal handler. See CWE-479: Signal Handler Use of a Non-reentrant Function ("https://cwe.mitre.org/data/definitions/479.html"). -Wno-analyzer-use-after-free This warning requires -fanalyzer, which enables it; use -Wno-analyzer-use-after-free to disable it. This diagnostic warns for paths through the code in which a pointer is used after a deallocator is called on it: either "free", or a deallocator referenced by attribute "malloc". See CWE-416: Use After Free ("https://cwe.mitre.org/data/definitions/416.html"). -Wno-analyzer-use-of-pointer-in-stale-stack-frame This warning requires -fanalyzer, which enables it; use -Wno-analyzer-use-of-pointer-in-stale-stack-frame to disable it. This diagnostic warns for paths through the code in which a pointer is dereferenced that points to a variable in a stale stack frame. -Wno-analyzer-va-arg-type-mismatch This warning requires -fanalyzer, which enables it; use -Wno-analyzer-va-arg-type-mismatch to disable it. This diagnostic warns for interprocedural paths through the code for which the analyzer detects an attempt to use "va_arg" to extract a value passed to a variadic call, but uses a type that does not match that of the expression passed to the call. See CWE-686: Function Call With Incorrect Argument Type ("https://cwe.mitre.org/data/definitions/686.html"). -Wno-analyzer-va-list-exhausted This warning requires -fanalyzer, which enables it; use -Wno-analyzer-va-list-exhausted to disable it. This diagnostic warns for interprocedural paths through the code for which the analyzer detects an attempt to use "va_arg" to access the next value passed to a variadic call, but all of the values in the "va_list" have already been consumed. See CWE-685: Function Call With Incorrect Number of Arguments ("https://cwe.mitre.org/data/definitions/685.html"). -Wno-analyzer-va-list-leak This warning requires -fanalyzer, which enables it; use -Wno-analyzer-va-list-leak to disable it. This diagnostic warns for interprocedural paths through the code for which the analyzer detects that "va_start" or "va_copy" has been called on a "va_list" without a corresponding call to "va_end". -Wno-analyzer-va-list-use-after-va-end This warning requires -fanalyzer, which enables it; use -Wno-analyzer-va-list-use-after-va-end to disable it. This diagnostic warns for interprocedural paths through the code for which the analyzer detects an attempt to use a "va_list" after "va_end" has been called on it. "va_list". -Wno-analyzer-write-to-const This warning requires -fanalyzer, which enables it; use -Wno-analyzer-write-to-const to disable it. This diagnostic warns for paths through the code in which the analyzer detects an attempt to write through a pointer to a "const" object. However, the analyzer does not prioritize detection of such paths, so false negatives are more likely relative to other warnings. -Wno-analyzer-write-to-string-literal This warning requires -fanalyzer, which enables it; use -Wno-analyzer-write-to-string-literal to disable it. This diagnostic warns for paths through the code in which the analyzer detects an attempt to write through a pointer to a string literal. However, the analyzer does not prioritize detection of such paths, so false negatives are more likely relative to other warnings. -Wno-analyzer-use-of-uninitialized-value This warning requires -fanalyzer, which enables it; use -Wno-analyzer-use-of-uninitialized-value to disable it. This diagnostic warns for paths through the code in which an uninitialized value is used. See CWE-457: Use of Uninitialized Variable ("https://cwe.mitre.org/data/definitions/457.html"). The analyzer has hardcoded knowledge about the behavior of the following memory-management functions: *<"alloca"> *<The built-in functions "__builtin_alloc",> "__builtin_alloc_with_align", @item "__builtin_calloc", "__builtin_free", "__builtin_malloc", "__builtin_memcpy", "__builtin_memcpy_chk", "__builtin_memset", "__builtin_memset_chk", "__builtin_realloc", "__builtin_stack_restore", and "__builtin_stack_save" *<"calloc"> *<"free"> *<"malloc"> *<"memset"> *<"operator delete"> *<"operator delete []"> *<"operator new"> *<"operator new []"> *<"realloc"> *<"strdup"> *<"strndup"> of the following functions for working with file descriptors: *<"open"> *<"close"> *<"creat"> *<"dup", "dup2" and "dup3"> *<"isatty"> *<"pipe", and "pipe2"> *<"read"> *<"write"> *<"socket", "bind", "listen", "accept", and "connect"> of the following functions for working with "<stdio.h>" streams: *<The built-in functions "__builtin_fprintf",> "__builtin_fprintf_unlocked", "__builtin_fputc", "__builtin_fputc_unlocked", "__builtin_fputs", "__builtin_fputs_unlocked", "__builtin_fwrite", "__builtin_fwrite_unlocked", "__builtin_printf", "__builtin_printf_unlocked", "__builtin_putc", "__builtin_putchar", "__builtin_putchar_unlocked", "__builtin_putc_unlocked", "__builtin_puts", "__builtin_puts_unlocked", "__builtin_vfprintf", and "__builtin_vprintf" *<"fopen"> *<"fclose"> *<"ferror"> *<"fgets"> *<"fgets_unlocked"> *<"fileno"> *<"fread"> *<"getc"> *<"getchar"> *<"fprintf"> *<"printf"> *<"fwrite"> and of the following functions: *<The built-in functions "__builtin_expect",> "__builtin_expect_with_probability", "__builtin_strchr", "__builtin_strcpy", "__builtin_strcpy_chk", "__builtin_strlen", "__builtin_va_copy", and "__builtin_va_start" *<The GNU extensions "error" and "error_at_line"> *<"getpass"> *<"longjmp"> *<"putenv"> *<"setjmp"> *<"siglongjmp"> *<"signal"> *<"sigsetjmp"> *<"strchr"> *<"strlen"> In addition, various functions with an "__analyzer_" prefix have special meaning to the analyzer, described in the GCC Internals manual. Pertinent parameters for controlling the exploration are: *<--param analyzer-bb-explosion-factor=value> *<--param analyzer-max-enodes-per-program-point=value> *<--param analyzer-max-recursion-depth=value> *<--param analyzer-min-snodes-for-call-summary=value> The following options control the analyzer. -fanalyzer-call-summaries Simplify interprocedural analysis by computing the effect of certain calls, rather than exploring all paths through the function from callsite to each possible return. If enabled, call summaries are only used for functions with more than one call site, and that are sufficiently complicated (as per --param analyzer-min-snodes-for-call-summary=value). -fanalyzer-checker=name Restrict the analyzer to run just the named checker, and enable it. Some checkers are disabled by default (even with -fanalyzer), such as the "taint" checker that implements -Wanalyzer-tainted-array-index, and this option is required to enable them. Note: currently, -fanalyzer-checker=taint disables the following warnings from -fanalyzer: -Wanalyzer-deref-before-check -Wanalyzer-double-fclose -Wanalyzer-double-free -Wanalyzer-exposure-through-output-file -Wanalyzer-fd-access-mode-mismatch -Wanalyzer-fd-double-close -Wanalyzer-fd-leak -Wanalyzer-fd-use-after-close -Wanalyzer-fd-use-without-check -Wanalyzer-file-leak -Wanalyzer-free-of-non-heap -Wanalyzer-malloc-leak -Wanalyzer-mismatching-deallocation -Wanalyzer-null-argument -Wanalyzer-null-dereference -Wanalyzer-possible-null-argument -Wanalyzer-possible-null-dereference -Wanalyzer-unsafe-call-within-signal-handler -Wanalyzer-use-after-free -Wanalyzer-va-list-leak -Wanalyzer-va-list-use-after-va-end -fno-analyzer-feasibility This option is intended for analyzer developers. By default the analyzer verifies that there is a feasible control flow path for each diagnostic it emits: that the conditions that hold are not mutually exclusive. Diagnostics for which no feasible path can be found are rejected. This filtering can be suppressed with -fno-analyzer-feasibility, for debugging issues in this code. -fanalyzer-fine-grained This option is intended for analyzer developers. Internally the analyzer builds an "exploded graph" that combines control flow graphs with data flow information. By default, an edge in this graph can contain the effects of a run of multiple statements within a basic block. With -fanalyzer-fine-grained, each statement gets its own edge. -fanalyzer-show-duplicate-count This option is intended for analyzer developers: if multiple diagnostics have been detected as being duplicates of each other, it emits a note when reporting the best diagnostic, giving the number of additional diagnostics that were suppressed by the deduplication logic. -fno-analyzer-state-merge This option is intended for analyzer developers. By default the analyzer attempts to simplify analysis by merging sufficiently similar states at each program point as it builds its "exploded graph". With -fno-analyzer-state-merge this merging can be suppressed, for debugging state-handling issues. -fno-analyzer-state-purge This option is intended for analyzer developers. By default the analyzer attempts to simplify analysis by purging aspects of state at a program point that appear to no longer be relevant e.g. the values of locals that aren't accessed later in the function and which aren't relevant to leak analysis. With -fno-analyzer-state-purge this purging of state can be suppressed, for debugging state-handling issues. -fno-analyzer-suppress-followups This option is intended for analyzer developers. By default the analyzer will stop exploring an execution path after encountering certain diagnostics, in order to avoid potentially issuing a cascade of follow-up diagnostics. The diagnostics that terminate analysis along a path are: *<-Wanalyzer-null-argument> *<-Wanalyzer-null-dereference> *<-Wanalyzer-use-after-free> *<-Wanalyzer-use-of-pointer-in-stale-stack-frame> *<-Wanalyzer-use-of-uninitialized-value> With -fno-analyzer-suppress-followups the analyzer will continue to explore such paths even after such diagnostics, which may be helpful for debugging issues in the analyzer, or for microbenchmarks for detecting undefined behavior. -fanalyzer-transitivity This option enables transitivity of constraints within the analyzer. -fno-analyzer-undo-inlining This option is intended for analyzer developers. -fanalyzer runs relatively late compared to other code analysis tools, and some optimizations have already been applied to the code. In particular function inlining may have occurred, leading to the interprocedural execution paths emitted by the analyzer containing function frames that don't correspond to those in the original source code. By default the analyzer attempts to reconstruct the original function frames, and to emit events showing the inlined calls. With -fno-analyzer-undo-inlining this attempt to reconstruct the original frame information can be be disabled, which may be of help when debugging issues in the analyzer. -fanalyzer-verbose-edges This option is intended for analyzer developers. It enables more verbose, lower-level detail in the descriptions of control flow within diagnostic paths. -fanalyzer-verbose-state-changes This option is intended for analyzer developers. It enables more verbose, lower-level detail in the descriptions of events relating to state machines within diagnostic paths. -fanalyzer-verbosity=level This option controls the complexity of the control flow paths that are emitted for analyzer diagnostics. The level can be one of: 0 At this level, interprocedural call and return events are displayed, along with the most pertinent state-change events relating to a diagnostic. For example, for a double-"free" diagnostic, both calls to "free" will be shown. 1 As per the previous level, but also show events for the entry to each function. 2 As per the previous level, but also show events relating to control flow that are significant to triggering the issue (e.g. "true path taken" at a conditional). This level is the default. 3 As per the previous level, but show all control flow events, not just significant ones. 4 This level is intended for analyzer developers; it adds various other events intended for debugging the analyzer. -fdump-analyzer Dump internal details about what the analyzer is doing to file.analyzer.txt. -fdump-analyzer-stderr overrides this option. -fdump-analyzer-stderr Dump internal details about what the analyzer is doing to stderr. This option overrides -fdump-analyzer. -fdump-analyzer-callgraph Dump a representation of the call graph suitable for viewing with GraphViz to file.callgraph.dot. -fdump-analyzer-exploded-graph Dump a representation of the "exploded graph" suitable for viewing with GraphViz to file.eg.dot. Nodes are color-coded based on state-machine states to emphasize state changes. -fdump-analyzer-exploded-nodes Emit diagnostics showing where nodes in the "exploded graph" are in relation to the program source. -fdump-analyzer-exploded-nodes-2 Dump a textual representation of the "exploded graph" to file.eg.txt. -fdump-analyzer-exploded-nodes-3 Dump a textual representation of the "exploded graph" to one dump file per node, to file.eg-id.txt. This is typically a large number of dump files. -fdump-analyzer-exploded-paths Dump a textual representation of the "exploded path" for each diagnostic to file.idx.kind.epath.txt. -fdump-analyzer-feasibility Dump internal details about the analyzer's search for feasible paths. The details are written in a form suitable for viewing with GraphViz to filenames of the form file.*.fg.dot, file.*.tg.dot, and file.*.fpath.txt. -fdump-analyzer-json Dump a compressed JSON representation of analyzer internals to file.analyzer.json.gz. The precise format is subject to change. -fdump-analyzer-state-purge As per -fdump-analyzer-supergraph, dump a representation of the "supergraph" suitable for viewing with GraphViz, but annotate the graph with information on what state will be purged at each node. The graph is written to file.state-purge.dot. -fdump-analyzer-supergraph Dump representations of the "supergraph" suitable for viewing with GraphViz to file.supergraph.dot and to file.supergraph-eg.dot. These show all of the control flow graphs in the program, with interprocedural edges for calls and returns. The second dump contains annotations showing nodes in the "exploded graph" and diagnostics associated with them. -fdump-analyzer-untracked Emit custom warnings with internal details intended for analyzer developers. Options for Debugging Your Program To tell GCC to emit extra information for use by a debugger, in almost all cases you need only to add -g to your other options. Some debug formats can co-exist (like DWARF with CTF) when each of them is enabled explicitly by adding the respective command line option to your other options. GCC allows you to use -g with -O. The shortcuts taken by optimized code may occasionally be surprising: some variables you declared may not exist at all; flow of control may briefly move where you did not expect it; some statements may not be executed because they compute constant results or their values are already at hand; some statements may execute in different places because they have been moved out of loops. Nevertheless it is possible to debug optimized output. This makes it reasonable to use the optimizer for programs that might have bugs. If you are not using some other optimization option, consider using -Og with -g. With no -O option at all, some compiler passes that collect information useful for debugging do not run at all, so that -Og may result in a better debugging experience. -g Produce debugging information in the operating system's native format (stabs, COFF, XCOFF, or DWARF). GDB can work with this debugging information. On most systems that use stabs format, -g enables use of extra debugging information that only GDB can use; this extra information makes debugging work better in GDB but probably makes other debuggers crash or refuse to read the program. If you want to control for certain whether to generate the extra information, use -gvms (see below). -ggdb Produce debugging information for use by GDB. This means to use the most expressive format available (DWARF, stabs, or the native format if neither of those are supported), including GDB extensions if at all possible. -gdwarf -gdwarf-version Produce debugging information in DWARF format (if that is supported). The value of version may be either 2, 3, 4 or 5; the default version for most targets is 5 (with the exception of VxWorks, TPF and Darwin/Mac OS X, which default to version 2, and AIX, which defaults to version 4). Note that with DWARF Version 2, some ports require and always use some non-conflicting DWARF 3 extensions in the unwind tables. Version 4 may require GDB 7.0 and -fvar-tracking-assignments for maximum benefit. Version 5 requires GDB 8.0 or higher. GCC no longer supports DWARF Version 1, which is substantially different than Version 2 and later. For historical reasons, some other DWARF-related options such as -fno-dwarf2-cfi-asm) retain a reference to DWARF Version 2 in their names, but apply to all currently-supported versions of DWARF. -gbtf Request BTF debug information. BTF is the default debugging format for the eBPF target. On other targets, like x86, BTF debug information can be generated along with DWARF debug information when both of the debug formats are enabled explicitly via their respective command line options. -gctf -gctflevel Request CTF debug information and use level to specify how much CTF debug information should be produced. If -gctf is specified without a value for level, the default level of CTF debug information is 2. CTF debug information can be generated along with DWARF debug information when both of the debug formats are enabled explicitly via their respective command line options. Level 0 produces no CTF debug information at all. Thus, -gctf0 negates -gctf. Level 1 produces CTF information for tracebacks only. This includes callsite information, but does not include type information. Level 2 produces type information for entities (functions, data objects etc.) at file-scope or global-scope only. -gvms Produce debugging information in Alpha/VMS debug format (if that is supported). This is the format used by DEBUG on Alpha/VMS systems. -glevel -ggdblevel -gvmslevel Request debugging information and also use level to specify how much information. The default level is 2. Level 0 produces no debug information at all. Thus, -g0 negates -g. Level 1 produces minimal information, enough for making backtraces in parts of the program that you don't plan to debug. This includes descriptions of functions and external variables, and line number tables, but no information about local variables. Level 3 includes extra information, such as all the macro definitions present in the program. Some debuggers support macro expansion when you use -g3. If you use multiple -g options, with or without level numbers, the last such option is the one that is effective. -gdwarf does not accept a concatenated debug level, to avoid confusion with -gdwarf-level. Instead use an additional -glevel option to change the debug level for DWARF. -fno-eliminate-unused-debug-symbols By default, no debug information is produced for symbols that are not actually used. Use this option if you want debug information for all symbols. -femit-class-debug-always Instead of emitting debugging information for a C++ class in only one object file, emit it in all object files using the class. This option should be used only with debuggers that are unable to handle the way GCC normally emits debugging information for classes because using this option increases the size of debugging information by as much as a factor of two. -fno-merge-debug-strings Direct the linker to not merge together strings in the debugging information that are identical in different object files. Merging is not supported by all assemblers or linkers. Merging decreases the size of the debug information in the output file at the cost of increasing link processing time. Merging is enabled by default. -fdebug-prefix-map=old=new When compiling files residing in directory old, record debugging information describing them as if the files resided in directory new instead. This can be used to replace a build-time path with an install-time path in the debug info. It can also be used to change an absolute path to a relative path by using . for new. This can give more reproducible builds, which are location independent, but may require an extra command to tell GDB where to find the source files. See also -ffile-prefix-map and -fcanon-prefix-map. -fvar-tracking Run variable tracking pass. It computes where variables are stored at each position in code. Better debugging information is then generated (if the debugging information format supports this information). It is enabled by default when compiling with optimization (-Os, -O, -O2, ...), debugging information (-g) and the debug info format supports it. -fvar-tracking-assignments Annotate assignments to user variables early in the compilation and attempt to carry the annotations over throughout the compilation all the way to the end, in an attempt to improve debug information while optimizing. Use of -gdwarf-4 is recommended along with it. It can be enabled even if var-tracking is disabled, in which case annotations are created and maintained, but discarded at the end. By default, this flag is enabled together with -fvar-tracking, except when selective scheduling is enabled. -gsplit-dwarf If DWARF debugging information is enabled, separate as much debugging information as possible into a separate output file with the extension .dwo. This option allows the build system to avoid linking files with debug information. To be useful, this option requires a debugger capable of reading .dwo files. -gdwarf32 -gdwarf64 If DWARF debugging information is enabled, the -gdwarf32 selects the 32-bit DWARF format and the -gdwarf64 selects the 64-bit DWARF format. The default is target specific, on most targets it is -gdwarf32 though. The 32-bit DWARF format is smaller, but can't support more than 2GiB of debug information in any of the DWARF debug information sections. The 64-bit DWARF format allows larger debug information and might not be well supported by all consumers yet. -gdescribe-dies Add description attributes to some DWARF DIEs that have no name attribute, such as artificial variables, external references and call site parameter DIEs. -gpubnames Generate DWARF ".debug_pubnames" and ".debug_pubtypes" sections. -ggnu-pubnames Generate ".debug_pubnames" and ".debug_pubtypes" sections in a format suitable for conversion into a GDB index. This option is only useful with a linker that can produce GDB index version 7. -fdebug-types-section When using DWARF Version 4 or higher, type DIEs can be put into their own ".debug_types" section instead of making them part of the ".debug_info" section. It is more efficient to put them in a separate comdat section since the linker can then remove duplicates. But not all DWARF consumers support ".debug_types" sections yet and on some objects ".debug_types" produces larger instead of smaller debugging information. -grecord-gcc-switches -gno-record-gcc-switches This switch causes the command-line options used to invoke the compiler that may affect code generation to be appended to the DW_AT_producer attribute in DWARF debugging information. The options are concatenated with spaces separating them from each other and from the compiler version. It is enabled by default. See also -frecord-gcc-switches for another way of storing compiler options into the object file. -gstrict-dwarf Disallow using extensions of later DWARF standard version than selected with -gdwarf-version. On most targets using non- conflicting DWARF extensions from later standard versions is allowed. -gno-strict-dwarf Allow using extensions of later DWARF standard version than selected with -gdwarf-version. -gas-loc-support Inform the compiler that the assembler supports ".loc" directives. It may then use them for the assembler to generate DWARF2+ line number tables. This is generally desirable, because assembler-generated line- number tables are a lot more compact than those the compiler can generate itself. This option will be enabled by default if, at GCC configure time, the assembler was found to support such directives. -gno-as-loc-support Force GCC to generate DWARF2+ line number tables internally, if DWARF2+ line number tables are to be generated. -gas-locview-support Inform the compiler that the assembler supports "view" assignment and reset assertion checking in ".loc" directives. This option will be enabled by default if, at GCC configure time, the assembler was found to support them. -gno-as-locview-support Force GCC to assign view numbers internally, if -gvariable-location-views are explicitly requested. -gcolumn-info -gno-column-info Emit location column information into DWARF debugging information, rather than just file and line. This option is enabled by default. -gstatement-frontiers -gno-statement-frontiers This option causes GCC to create markers in the internal representation at the beginning of statements, and to keep them roughly in place throughout compilation, using them to guide the output of "is_stmt" markers in the line number table. This is enabled by default when compiling with optimization (-Os, -O1, -O2, ...), and outputting DWARF 2 debug information at the normal level. -gvariable-location-views -gvariable-location-views=incompat5 -gno-variable-location-views Augment variable location lists with progressive view numbers implied from the line number table. This enables debug information consumers to inspect state at certain points of the program, even if no instructions associated with the corresponding source locations are present at that point. If the assembler lacks support for view numbers in line number tables, this will cause the compiler to emit the line number table, which generally makes them somewhat less compact. The augmented line number tables and location lists are fully backward-compatible, so they can be consumed by debug information consumers that are not aware of these augmentations, but they won't derive any benefit from them either. This is enabled by default when outputting DWARF 2 debug information at the normal level, as long as there is assembler support, -fvar-tracking-assignments is enabled and -gstrict-dwarf is not. When assembler support is not available, this may still be enabled, but it will force GCC to output internal line number tables, and if -ginternal-reset-location-views is not enabled, that will most certainly lead to silently mismatching location views. There is a proposed representation for view numbers that is not backward compatible with the location list format introduced in DWARF 5, that can be enabled with -gvariable-location-views=incompat5. This option may be removed in the future, is only provided as a reference implementation of the proposed representation. Debug information consumers are not expected to support this extended format, and they would be rendered unable to decode location lists using it. -ginternal-reset-location-views -gno-internal-reset-location-views Attempt to determine location views that can be omitted from location view lists. This requires the compiler to have very accurate insn length estimates, which isn't always the case, and it may cause incorrect view lists to be generated silently when using an assembler that does not support location view lists. The GNU assembler will flag any such error as a "view number mismatch". This is only enabled on ports that define a reliable estimation function. -ginline-points -gno-inline-points Generate extended debug information for inlined functions. Location view tracking markers are inserted at inlined entry points, so that address and view numbers can be computed and output in debug information. This can be enabled independently of location views, in which case the view numbers won't be output, but it can only be enabled along with statement frontiers, and it is only enabled by default if location views are enabled. -gz[=type] Produce compressed debug sections in DWARF format, if that is supported. If type is not given, the default type depends on the capabilities of the assembler and linker used. type may be one of none (don't compress debug sections), or zlib (use zlib compression in ELF gABI format). If the linker doesn't support writing compressed debug sections, the option is rejected. Otherwise, if the assembler does not support them, -gz is silently ignored when producing object files. -femit-struct-debug-baseonly Emit debug information for struct-like types only when the base name of the compilation source file matches the base name of file in which the struct is defined. This option substantially reduces the size of debugging information, but at significant potential loss in type information to the debugger. See -femit-struct-debug-reduced for a less aggressive option. See -femit-struct-debug-detailed for more detailed control. This option works only with DWARF debug output. -femit-struct-debug-reduced Emit debug information for struct-like types only when the base name of the compilation source file matches the base name of file in which the type is defined, unless the struct is a template or defined in a system header. This option significantly reduces the size of debugging information, with some potential loss in type information to the debugger. See -femit-struct-debug-baseonly for a more aggressive option. See -femit-struct-debug-detailed for more detailed control. This option works only with DWARF debug output. -femit-struct-debug-detailed[=spec-list] Specify the struct-like types for which the compiler generates debug information. The intent is to reduce duplicate struct debug information between different object files within the same program. This option is a detailed version of -femit-struct-debug-reduced and -femit-struct-debug-baseonly, which serves for most needs. A specification has the syntax[dir:|ind:][ord:|gen:](any|sys|base|none) The optional first word limits the specification to structs that are used directly (dir:) or used indirectly (ind:). A struct type is used directly when it is the type of a variable, member. Indirect uses arise through pointers to structs. That is, when use of an incomplete struct is valid, the use is indirect. An example is struct one direct; struct two * indirect;. The optional second word limits the specification to ordinary structs (ord:) or generic structs (gen:). Generic structs are a bit complicated to explain. For C++, these are non-explicit specializations of template classes, or non-template classes within the above. Other programming languages have generics, but -femit-struct-debug-detailed does not yet implement them. The third word specifies the source files for those structs for which the compiler should emit debug information. The values none and any have the normal meaning. The value base means that the base of name of the file in which the type declaration appears must match the base of the name of the main compilation file. In practice, this means that when compiling foo.c, debug information is generated for types declared in that file and foo.h, but not other header files. The value sys means those types satisfying base or declared in system or compiler headers. You may need to experiment to determine the best settings for your application. The default is -femit-struct-debug-detailed=all. This option works only with DWARF debug output. -fno-dwarf2-cfi-asm Emit DWARF unwind info as compiler generated ".eh_frame" section instead of using GAS ".cfi_*" directives. -fno-eliminate-unused-debug-types Normally, when producing DWARF output, GCC avoids producing debug symbol output for types that are nowhere used in the source file being compiled. Sometimes it is useful to have GCC emit debugging information for all types declared in a compilation unit, regardless of whether or not they are actually used in that compilation unit, for example if, in the debugger, you want to cast a value to a type that is not actually used in your program (but is declared). More often, however, this results in a significant amount of wasted space. Options That Control Optimization These options control various sorts of optimizations. Without any optimization option, the compiler's goal is to reduce the cost of compilation and to make debugging produce the expected results. Statements are independent: if you stop the program with a breakpoint between statements, you can then assign a new value to any variable or change the program counter to any other statement in the function and get exactly the results you expect from the source code. Turning on optimization flags makes the compiler attempt to improve the performance and/or code size at the expense of compilation time and possibly the ability to debug the program. The compiler performs optimization based on the knowledge it has of the program. Compiling multiple files at once to a single output file mode allows the compiler to use information gained from all of the files when compiling each of them. Not all optimizations are controlled directly by a flag. Only optimizations that have a flag are listed in this section. Most optimizations are completely disabled at -O0 or if an -O level is not set on the command line, even if individual optimization flags are specified. Similarly, -Og suppresses many optimization passes. Depending on the target and how GCC was configured, a slightly different set of optimizations may be enabled at each -O level than those listed here. You can invoke GCC with -Q --help=optimizers to find out the exact set of optimizations that are enabled at each level. -O -O1 Optimize. Optimizing compilation takes somewhat more time, and a lot more memory for a large function. With -O, the compiler tries to reduce code size and execution time, without performing any optimizations that take a great deal of compilation time. -O turns on the following optimization flags: -fauto-inc-dec -fbranch-count-reg -fcombine-stack-adjustments -fcompare-elim -fcprop-registers -fdce -fdefer-pop -fdelayed-branch -fdse -fforward-propagate -fguess-branch-probability -fif-conversion -fif-conversion2 -finline-functions-called-once -fipa-modref -fipa-profile -fipa-pure-const -fipa-reference -fipa-reference-addressable -fmerge-constants -fmove-loop-invariants -fmove-loop-stores -fomit-frame-pointer -freorder-blocks -fshrink-wrap -fshrink-wrap-separate -fsplit-wide-types -fssa-backprop -fssa-phiopt -ftree-bit-ccp -ftree-ccp -ftree-ch -ftree-coalesce-vars -ftree-copy-prop -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre -ftree-phiprop -ftree-pta -ftree-scev-cprop -ftree-sink -ftree-slsr -ftree-sra -ftree-ter -funit-at-a-time -O2 Optimize even more. GCC performs nearly all supported optimizations that do not involve a space-speed tradeoff. As compared to -O, this option increases both compilation time and the performance of the generated code. -O2 turns on all optimization flags specified by -O1. It also turns on the following optimization flags: -falign-functions -falign-jumps -falign-labels -falign-loops -fcaller-saves -fcode-hoisting -fcrossjumping -fcse-follow-jumps -fcse-skip-blocks -fdelete-null-pointer-checks -fdevirtualize -fdevirtualize-speculatively -fexpensive-optimizations -ffinite-loops -fgcse -fgcse-lm -fhoist-adjacent-loads -finline-functions -finline-small-functions -findirect-inlining -fipa-bit-cp -fipa-cp -fipa-icf -fipa-ra -fipa-sra -fipa-vrp -fisolate-erroneous-paths-dereference -flra-remat -foptimize-sibling-calls -foptimize-strlen -fpartial-inlining -fpeephole2 -freorder-blocks-algorithm=stc -freorder-blocks-and-partition -freorder-functions -frerun-cse-after-loop -fschedule-insns -fschedule-insns2 -fsched-interblock -fsched-spec -fstore-merging -fstrict-aliasing -fthread-jumps -ftree-builtin-call-dce -ftree-loop-vectorize -ftree-pre -ftree-slp-vectorize -ftree-switch-conversion -ftree-tail-merge -ftree-vrp -fvect-cost-model=very-cheap Please note the warning under -fgcse about invoking -O2 on programs that use computed gotos. -O3 Optimize yet more. -O3 turns on all optimizations specified by -O2 and also turns on the following optimization flags: -fgcse-after-reload -fipa-cp-clone -floop-interchange -floop-unroll-and-jam -fpeel-loops -fpredictive-commoning -fsplit-loops -fsplit-paths -ftree-loop-distribution -ftree-partial-pre -funswitch-loops -fvect-cost-model=dynamic -fversion-loops-for-strides -O0 Reduce compilation time and make debugging produce the expected results. This is the default. -Os Optimize for size. -Os enables all -O2 optimizations except those that often increase code size: -falign-functions -falign-jumps -falign-labels -falign-loops -fprefetch-loop-arrays -freorder-blocks-algorithm=stc It also enables -finline-functions, causes the compiler to tune for code size rather than execution speed, and performs further optimizations designed to reduce code size. -Ofast Disregard strict standards compliance. -Ofast enables all -O3 optimizations. It also enables optimizations that are not valid for all standard-compliant programs. It turns on -ffast-math, -fallow-store-data-races and the Fortran-specific -fstack-arrays, unless -fmax-stack-var-size is specified, and -fno-protect-parens. It turns off -fsemantic-interposition. -Og Optimize debugging experience. -Og should be the optimization level of choice for the standard edit-compile-debug cycle, offering a reasonable level of optimization while maintaining fast compilation and a good debugging experience. It is a better choice than -O0 for producing debuggable code because some compiler passes that collect debug information are disabled at -O0. Like -O0, -Og completely disables a number of optimization passes so that individual options controlling them have no effect. Otherwise -Og enables all -O1 optimization flags except for those that may interfere with debugging: -fbranch-count-reg -fdelayed-branch -fdse -fif-conversion -fif-conversion2 -finline-functions-called-once -fmove-loop-invariants -fmove-loop-stores -fssa-phiopt -ftree-bit-ccp -ftree-dse -ftree-pta -ftree-sra -Oz Optimize aggressively for size rather than speed. This may increase the number of instructions executed if those instructions require fewer bytes to encode. -Oz behaves similarly to -Os including enabling most -O2 optimizations. If you use multiple -O options, with or without level numbers, the last such option is the one that is effective. Options of the form -fflag specify machine-independent flags. Most flags have both positive and negative forms; the negative form of -ffoo is -fno-foo. In the table below, only one of the forms is listed---the one you typically use. You can figure out the other form by either removing no- or adding it. The following options control specific optimizations. They are either activated by -O options or are related to ones that are. You can use the following flags in the rare cases when "fine-tuning" of optimizations to be performed is desired. -fno-defer-pop For machines that must pop arguments after a function call, always pop the arguments as soon as each function returns. At levels -O1 and higher, -fdefer-pop is the default; this allows the compiler to let arguments accumulate on the stack for several function calls and pop them all at once. -fforward-propagate Perform a forward propagation pass on RTL. The pass tries to combine two instructions and checks if the result can be simplified. If loop unrolling is active, two passes are performed and the second is scheduled after loop unrolling. This option is enabled by default at optimization levels -O1, -O2, -O3, -Os. -ffp-contract=style -ffp-contract=off disables floating-point expression contraction. -ffp-contract=fast enables floating-point expression contraction such as forming of fused multiply-add operations if the target has native support for them. -ffp-contract=on enables floating-point expression contraction if allowed by the language standard. This is currently not implemented and treated equal to -ffp-contract=off. The default is -ffp-contract=fast. -fomit-frame-pointer Omit the frame pointer in functions that don't need one. This avoids the instructions to save, set up and restore the frame pointer; on many targets it also makes an extra register available. On some targets this flag has no effect because the standard calling sequence always uses a frame pointer, so it cannot be omitted. Note that -fno-omit-frame-pointer doesn't guarantee the frame pointer is used in all functions. Several targets always omit the frame pointer in leaf functions. Enabled by default at -O1 and higher. -foptimize-sibling-calls Optimize sibling and tail recursive calls. Enabled at levels -O2, -O3, -Os. -foptimize-strlen Optimize various standard C string functions (e.g. "strlen", "strchr" or "strcpy") and their "_FORTIFY_SOURCE" counterparts into faster alternatives. Enabled at levels -O2, -O3. -fno-inline Do not expand any functions inline apart from those marked with the "always_inline" attribute. This is the default when not optimizing. Single functions can be exempted from inlining by marking them with the "noinline" attribute. -finline-small-functions Integrate functions into their callers when their body is smaller than expected function call code (so overall size of program gets smaller). The compiler heuristically decides which functions are simple enough to be worth integrating in this way. This inlining applies to all functions, even those not declared inline. Enabled at levels -O2, -O3, -Os. -findirect-inlining Inline also indirect calls that are discovered to be known at compile time thanks to previous inlining. This option has any effect only when inlining itself is turned on by the -finline-functions or -finline-small-functions options. Enabled at levels -O2, -O3, -Os. -finline-functions Consider all functions for inlining, even if they are not declared inline. The compiler heuristically decides which functions are worth integrating in this way. If all calls to a given function are integrated, and the function is declared "static", then the function is normally not output as assembler code in its own right. Enabled at levels -O2, -O3, -Os. Also enabled by -fprofile-use and -fauto-profile. -finline-functions-called-once Consider all "static" functions called once for inlining into their caller even if they are not marked "inline". If a call to a given function is integrated, then the function is not output as assembler code in its own right. Enabled at levels -O1, -O2, -O3 and -Os, but not -Og. -fearly-inlining Inline functions marked by "always_inline" and functions whose body seems smaller than the function call overhead early before doing -fprofile-generate instrumentation and real inlining pass. Doing so makes profiling significantly cheaper and usually inlining faster on programs having large chains of nested wrapper functions. Enabled by default. -fipa-sra Perform interprocedural scalar replacement of aggregates, removal of unused parameters and replacement of parameters passed by reference by parameters passed by value. Enabled at levels -O2, -O3 and -Os. -finline-limit=n By default, GCC limits the size of functions that can be inlined. This flag allows coarse control of this limit. n is the size of functions that can be inlined in number of pseudo instructions. Inlining is actually controlled by a number of parameters, which may be specified individually by using --param name=value. The -finline-limit=n option sets some of these parameters as follows: max-inline-insns-single is set to n/2. max-inline-insns-auto is set to n/2. See below for a documentation of the individual parameters controlling inlining and for the defaults of these parameters. Note: there may be no value to -finline-limit that results in default behavior. Note: pseudo instruction represents, in this particular context, an abstract measurement of function's size. In no way does it represent a count of assembly instructions and as such its exact meaning might change from one release to an another. -fno-keep-inline-dllexport This is a more fine-grained version of -fkeep-inline-functions, which applies only to functions that are declared using the "dllexport" attribute or declspec. -fkeep-inline-functions In C, emit "static" functions that are declared "inline" into the object file, even if the function has been inlined into all of its callers. This switch does not affect functions using the "extern inline" extension in GNU C90. In C++, emit any and all inline functions into the object file. -fkeep-static-functions Emit "static" functions into the object file, even if the function is never used. -fkeep-static-consts Emit variables declared "static const" when optimization isn't turned on, even if the variables aren't referenced. GCC enables this option by default. If you want to force the compiler to check if a variable is referenced, regardless of whether or not optimization is turned on, use the -fno-keep-static-consts option. -fmerge-constants Attempt to merge identical constants (string constants and floating-point constants) across compilation units. This option is the default for optimized compilation if the assembler and linker support it. Use -fno-merge-constants to inhibit this behavior. Enabled at levels -O1, -O2, -O3, -Os. -fmerge-all-constants Attempt to merge identical constants and identical variables. This option implies -fmerge-constants. In addition to -fmerge-constants this considers e.g. even constant initialized arrays or initialized constant variables with integral or floating- point types. Languages like C or C++ require each variable, including multiple instances of the same variable in recursive calls, to have distinct locations, so using this option results in non-conforming behavior. -fmodulo-sched Perform swing modulo scheduling immediately before the first scheduling pass. This pass looks at innermost loops and reorders their instructions by overlapping different iterations. -fmodulo-sched-allow-regmoves Perform more aggressive SMS-based modulo scheduling with register moves allowed. By setting this flag certain anti-dependences edges are deleted, which triggers the generation of reg-moves based on the life-range analysis. This option is effective only with -fmodulo-sched enabled. -fno-branch-count-reg Disable the optimization pass that scans for opportunities to use "decrement and branch" instructions on a count register instead of instruction sequences that decrement a register, compare it against zero, and then branch based upon the result. This option is only meaningful on architectures that support such instructions, which include x86, PowerPC, IA-64 and S/390. Note that the -fno-branch-count-reg option doesn't remove the decrement and branch instructions from the generated instruction stream introduced by other optimization passes. The default is -fbranch-count-reg at -O1 and higher, except for -Og. -fno-function-cse Do not put function addresses in registers; make each instruction that calls a constant function contain the function's address explicitly. This option results in less efficient code, but some strange hacks that alter the assembler output may be confused by the optimizations performed when this option is not used. The default is -ffunction-cse -fno-zero-initialized-in-bss If the target supports a BSS section, GCC by default puts variables that are initialized to zero into BSS. This can save space in the resulting code. This option turns off this behavior because some programs explicitly rely on variables going to the data section---e.g., so that the resulting executable can find the beginning of that section and/or make assumptions based on that. The default is -fzero-initialized-in-bss. -fthread-jumps Perform optimizations that check to see if a jump branches to a location where another comparison subsumed by the first is found. If so, the first branch is redirected to either the destination of the second branch or a point immediately following it, depending on whether the condition is known to be true or false. Enabled at levels -O1, -O2, -O3, -Os. -fsplit-wide-types When using a type that occupies multiple registers, such as "long long" on a 32-bit system, split the registers apart and allocate them independently. This normally generates better code for those types, but may make debugging more difficult. Enabled at levels -O1, -O2, -O3, -Os. -fsplit-wide-types-early Fully split wide types early, instead of very late. This option has no effect unless -fsplit-wide-types is turned on. This is the default on some targets. -fcse-follow-jumps In common subexpression elimination (CSE), scan through jump instructions when the target of the jump is not reached by any other path. For example, when CSE encounters an "if" statement with an "else" clause, CSE follows the jump when the condition tested is false. Enabled at levels -O2, -O3, -Os. -fcse-skip-blocks This is similar to -fcse-follow-jumps, but causes CSE to follow jumps that conditionally skip over blocks. When CSE encounters a simple "if" statement with no else clause, -fcse-skip-blocks causes CSE to follow the jump around the body of the "if". Enabled at levels -O2, -O3, -Os. -frerun-cse-after-loop Re-run common subexpression elimination after loop optimizations are performed. Enabled at levels -O2, -O3, -Os. -fgcse Perform a global common subexpression elimination pass. This pass also performs global constant and copy propagation. Note: When compiling a program using computed gotos, a GCC extension, you may get better run-time performance if you disable the global common subexpression elimination pass by adding -fno-gcse to the command line. Enabled at levels -O2, -O3, -Os. -fgcse-lm When -fgcse-lm is enabled, global common subexpression elimination attempts to move loads that are only killed by stores into themselves. This allows a loop containing a load/store sequence to be changed to a load outside the loop, and a copy/store within the loop. Enabled by default when -fgcse is enabled. -fgcse-sm When -fgcse-sm is enabled, a store motion pass is run after global common subexpression elimination. This pass attempts to move stores out of loops. When used in conjunction with -fgcse-lm, loops containing a load/store sequence can be changed to a load before the loop and a store after the loop. Not enabled at any optimization level. -fgcse-las When -fgcse-las is enabled, the global common subexpression elimination pass eliminates redundant loads that come after stores to the same memory location (both partial and full redundancies). Not enabled at any optimization level. -fgcse-after-reload When -fgcse-after-reload is enabled, a redundant load elimination pass is performed after reload. The purpose of this pass is to clean up redundant spilling. Enabled by -O3, -fprofile-use and -fauto-profile. -faggressive-loop-optimizations This option tells the loop optimizer to use language constraints to derive bounds for the number of iterations of a loop. This assumes that loop code does not invoke undefined behavior by for example causing signed integer overflows or out-of-bound array accesses. The bounds for the number of iterations of a loop are used to guide loop unrolling and peeling and loop exit test optimizations. This option is enabled by default. -funconstrained-commons This option tells the compiler that variables declared in common blocks (e.g. Fortran) may later be overridden with longer trailing arrays. This prevents certain optimizations that depend on knowing the array bounds. -fcrossjumping Perform cross-jumping transformation. This transformation unifies equivalent code and saves code size. The resulting code may or may not perform better than without cross-jumping. Enabled at levels -O2, -O3, -Os. -fauto-inc-dec Combine increments or decrements of addresses with memory accesses. This pass is always skipped on architectures that do not have instructions to support this. Enabled by default at -O1 and higher on architectures that support this. -fdce Perform dead code elimination (DCE) on RTL. Enabled by default at -O1 and higher. -fdse Perform dead store elimination (DSE) on RTL. Enabled by default at -O1 and higher. -fif-conversion Attempt to transform conditional jumps into branch-less equivalents. This includes use of conditional moves, min, max, set flags and abs instructions, and some tricks doable by standard arithmetics. The use of conditional execution on chips where it is available is controlled by -fif-conversion2. Enabled at levels -O1, -O2, -O3, -Os, but not with -Og. -fif-conversion2 Use conditional execution (where available) to transform conditional jumps into branch-less equivalents. Enabled at levels -O1, -O2, -O3, -Os, but not with -Og. -fdeclone-ctor-dtor The C++ ABI requires multiple entry points for constructors and destructors: one for a base subobject, one for a complete object, and one for a virtual destructor that calls operator delete afterwards. For a hierarchy with virtual bases, the base and complete variants are clones, which means two copies of the function. With this option, the base and complete variants are changed to be thunks that call a common implementation. Enabled by -Os. -fdelete-null-pointer-checks Assume that programs cannot safely dereference null pointers, and that no code or data element resides at address zero. This option enables simple constant folding optimizations at all optimization levels. In addition, other optimization passes in GCC use this flag to control global dataflow analyses that eliminate useless checks for null pointers; these assume that a memory access to address zero always results in a trap, so that if a pointer is checked after it has already been dereferenced, it cannot be null. Note however that in some environments this assumption is not true. Use -fno-delete-null-pointer-checks to disable this optimization for programs that depend on that behavior. This option is enabled by default on most targets. On Nios II ELF, it defaults to off. On AVR and MSP430, this option is completely disabled. Passes that use the dataflow information are enabled independently at different optimization levels. -fdevirtualize Attempt to convert calls to virtual functions to direct calls. This is done both within a procedure and interprocedurally as part of indirect inlining (-findirect-inlining) and interprocedural constant propagation (-fipa-cp). Enabled at levels -O2, -O3, -Os. -fdevirtualize-speculatively Attempt to convert calls to virtual functions to speculative direct calls. Based on the analysis of the type inheritance graph, determine for a given call the set of likely targets. If the set is small, preferably of size 1, change the call into a conditional deciding between direct and indirect calls. The speculative calls enable more optimizations, such as inlining. When they seem useless after further optimization, they are converted back into original form. -fdevirtualize-at-ltrans Stream extra information needed for aggressive devirtualization when running the link-time optimizer in local transformation mode. This option enables more devirtualization but significantly increases the size of streamed data. For this reason it is disabled by default. -fexpensive-optimizations Perform a number of minor optimizations that are relatively expensive. Enabled at levels -O2, -O3, -Os. -free Attempt to remove redundant extension instructions. This is especially helpful for the x86-64 architecture, which implicitly zero-extends in 64-bit registers after writing to their lower 32-bit half. Enabled for Alpha, AArch64 and x86 at levels -O2, -O3, -Os. -fno-lifetime-dse In C++ the value of an object is only affected by changes within its lifetime: when the constructor begins, the object has an indeterminate value, and any changes during the lifetime of the object are dead when the object is destroyed. Normally dead store elimination will take advantage of this; if your code relies on the value of the object storage persisting beyond the lifetime of the object, you can use this flag to disable this optimization. To preserve stores before the constructor starts (e.g. because your operator new clears the object storage) but still treat the object as dead after the destructor, you can use -flifetime-dse=1. The default behavior can be explicitly selected with -flifetime-dse=2. -flifetime-dse=0 is equivalent to -fno-lifetime-dse. -flive-range-shrinkage Attempt to decrease register pressure through register live range shrinkage. This is helpful for fast processors with small or moderate size register sets. -fira-algorithm=algorithm Use the specified coloring algorithm for the integrated register allocator. The algorithm argument can be priority, which specifies Chow's priority coloring, or CB, which specifies Chaitin-Briggs coloring. Chaitin-Briggs coloring is not implemented for all architectures, but for those targets that do support it, it is the default because it generates better code. -fira-region=region Use specified regions for the integrated register allocator. The region argument should be one of the following: all Use all loops as register allocation regions. This can give the best results for machines with a small and/or irregular register set. mixed Use all loops except for loops with small register pressure as the regions. This value usually gives the best results in most cases and for most architectures, and is enabled by default when compiling with optimization for speed (-O, -O2, ...). one Use all functions as a single region. This typically results in the smallest code size, and is enabled by default for -Os or -O0. -fira-hoist-pressure Use IRA to evaluate register pressure in the code hoisting pass for decisions to hoist expressions. This option usually results in smaller code, but it can slow the compiler down. This option is enabled at level -Os for all targets. -fira-loop-pressure Use IRA to evaluate register pressure in loops for decisions to move loop invariants. This option usually results in generation of faster and smaller code on machines with large register files (>= 32 registers), but it can slow the compiler down. This option is enabled at level -O3 for some targets. -fno-ira-share-save-slots Disable sharing of stack slots used for saving call-used hard registers living through a call. Each hard register gets a separate stack slot, and as a result function stack frames are larger. -fno-ira-share-spill-slots Disable sharing of stack slots allocated for pseudo-registers. Each pseudo-register that does not get a hard register gets a separate stack slot, and as a result function stack frames are larger. -flra-remat Enable CFG-sensitive rematerialization in LRA. Instead of loading values of spilled pseudos, LRA tries to rematerialize (recalculate) values if it is profitable. Enabled at levels -O2, -O3, -Os. -fdelayed-branch If supported for the target machine, attempt to reorder instructions to exploit instruction slots available after delayed branch instructions. Enabled at levels -O1, -O2, -O3, -Os, but not at -Og. -fschedule-insns If supported for the target machine, attempt to reorder instructions to eliminate execution stalls due to required data being unavailable. This helps machines that have slow floating point or memory load instructions by allowing other instructions to be issued until the result of the load or floating-point instruction is required. Enabled at levels -O2, -O3. -fschedule-insns2 Similar to -fschedule-insns, but requests an additional pass of instruction scheduling after register allocation has been done. This is especially useful on machines with a relatively small number of registers and where memory load instructions take more than one cycle. Enabled at levels -O2, -O3, -Os. -fno-sched-interblock Disable instruction scheduling across basic blocks, which is normally enabled when scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher. -fno-sched-spec Disable speculative motion of non-load instructions, which is normally enabled when scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher. -fsched-pressure Enable register pressure sensitive insn scheduling before register allocation. This only makes sense when scheduling before register allocation is enabled, i.e. with -fschedule-insns or at -O2 or higher. Usage of this option can improve the generated code and decrease its size by preventing register pressure increase above the number of available hard registers and subsequent spills in register allocation. -fsched-spec-load Allow speculative motion of some load instructions. This only makes sense when scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher. -fsched-spec-load-dangerous Allow speculative motion of more load instructions. This only makes sense when scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher. -fsched-stalled-insns -fsched-stalled-insns=n Define how many insns (if any) can be moved prematurely from the queue of stalled insns into the ready list during the second scheduling pass. -fno-sched-stalled-insns means that no insns are moved prematurely, -fsched-stalled-insns=0 means there is no limit on how many queued insns can be moved prematurely. -fsched-stalled-insns without a value is equivalent to -fsched-stalled-insns=1. -fsched-stalled-insns-dep -fsched-stalled-insns-dep=n Define how many insn groups (cycles) are examined for a dependency on a stalled insn that is a candidate for premature removal from the queue of stalled insns. This has an effect only during the second scheduling pass, and only if -fsched-stalled-insns is used. -fno-sched-stalled-insns-dep is equivalent to -fsched-stalled-insns-dep=0. -fsched-stalled-insns-dep without a value is equivalent to -fsched-stalled-insns-dep=1. -fsched2-use-superblocks When scheduling after register allocation, use superblock scheduling. This allows motion across basic block boundaries, resulting in faster schedules. This option is experimental, as not all machine descriptions used by GCC model the CPU closely enough to avoid unreliable results from the algorithm. This only makes sense when scheduling after register allocation, i.e. with -fschedule-insns2 or at -O2 or higher. -fsched-group-heuristic Enable the group heuristic in the scheduler. This heuristic favors the instruction that belongs to a schedule group. This is enabled by default when scheduling is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at -O2 or higher. -fsched-critical-path-heuristic Enable the critical-path heuristic in the scheduler. This heuristic favors instructions on the critical path. This is enabled by default when scheduling is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at -O2 or higher. -fsched-spec-insn-heuristic Enable the speculative instruction heuristic in the scheduler. This heuristic favors speculative instructions with greater dependency weakness. This is enabled by default when scheduling is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at -O2 or higher. -fsched-rank-heuristic Enable the rank heuristic in the scheduler. This heuristic favors the instruction belonging to a basic block with greater size or frequency. This is enabled by default when scheduling is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at -O2 or higher. -fsched-last-insn-heuristic Enable the last-instruction heuristic in the scheduler. This heuristic favors the instruction that is less dependent on the last instruction scheduled. This is enabled by default when scheduling is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at -O2 or higher. -fsched-dep-count-heuristic Enable the dependent-count heuristic in the scheduler. This heuristic favors the instruction that has more instructions depending on it. This is enabled by default when scheduling is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at -O2 or higher. -freschedule-modulo-scheduled-loops Modulo scheduling is performed before traditional scheduling. If a loop is modulo scheduled, later scheduling passes may change its schedule. Use this option to control that behavior. -fselective-scheduling Schedule instructions using selective scheduling algorithm. Selective scheduling runs instead of the first scheduler pass. -fselective-scheduling2 Schedule instructions using selective scheduling algorithm. Selective scheduling runs instead of the second scheduler pass. -fsel-sched-pipelining Enable software pipelining of innermost loops during selective scheduling. This option has no effect unless one of -fselective-scheduling or -fselective-scheduling2 is turned on. -fsel-sched-pipelining-outer-loops When pipelining loops during selective scheduling, also pipeline outer loops. This option has no effect unless -fsel-sched-pipelining is turned on. -fsemantic-interposition Some object formats, like ELF, allow interposing of symbols by the dynamic linker. This means that for symbols exported from the DSO, the compiler cannot perform interprocedural propagation, inlining and other optimizations in anticipation that the function or variable in question may change. While this feature is useful, for example, to rewrite memory allocation functions by a debugging implementation, it is expensive in the terms of code quality. With -fno-semantic-interposition the compiler assumes that if interposition happens for functions the overwriting function will have precisely the same semantics (and side effects). Similarly if interposition happens for variables, the constructor of the variable will be the same. The flag has no effect for functions explicitly declared inline (where it is never allowed for interposition to change semantics) and for symbols explicitly declared weak. -fshrink-wrap Emit function prologues only before parts of the function that need it, rather than at the top of the function. This flag is enabled by default at -O and higher. -fshrink-wrap-separate Shrink-wrap separate parts of the prologue and epilogue separately, so that those parts are only executed when needed. This option is on by default, but has no effect unless -fshrink-wrap is also turned on and the target supports this. -fcaller-saves Enable allocation of values to registers that are clobbered by function calls, by emitting extra instructions to save and restore the registers around such calls. Such allocation is done only when it seems to result in better code. This option is always enabled by default on certain machines, usually those which have no call-preserved registers to use instead. Enabled at levels -O2, -O3, -Os. -fcombine-stack-adjustments Tracks stack adjustments (pushes and pops) and stack memory references and then tries to find ways to combine them. Enabled by default at -O1 and higher. -fipa-ra Use caller save registers for allocation if those registers are not used by any called function. In that case it is not necessary to save and restore them around calls. This is only possible if called functions are part of same compilation unit as current function and they are compiled before it. Enabled at levels -O2, -O3, -Os, however the option is disabled if generated code will be instrumented for profiling (-p, or -pg) or if callee's register usage cannot be known exactly (this happens on targets that do not expose prologues and epilogues in RTL). -fconserve-stack Attempt to minimize stack usage. The compiler attempts to use less stack space, even if that makes the program slower. This option implies setting the large-stack-frame parameter to 100 and the large-stack-frame-growth parameter to 400. -ftree-reassoc Perform reassociation on trees. This flag is enabled by default at -O1 and higher. -fcode-hoisting Perform code hoisting. Code hoisting tries to move the evaluation of expressions executed on all paths to the function exit as early as possible. This is especially useful as a code size optimization, but it often helps for code speed as well. This flag is enabled by default at -O2 and higher. -ftree-pre Perform partial redundancy elimination (PRE) on trees. This flag is enabled by default at -O2 and -O3. -ftree-partial-pre Make partial redundancy elimination (PRE) more aggressive. This flag is enabled by default at -O3. -ftree-forwprop Perform forward propagation on trees. This flag is enabled by default at -O1 and higher. -ftree-fre Perform full redundancy elimination (FRE) on trees. The difference between FRE and PRE is that FRE only considers expressions that are computed on all paths leading to the redundant computation. This analysis is faster than PRE, though it exposes fewer redundancies. This flag is enabled by default at -O1 and higher. -ftree-phiprop Perform hoisting of loads from conditional pointers on trees. This pass is enabled by default at -O1 and higher. -fhoist-adjacent-loads Speculatively hoist loads from both branches of an if-then-else if the loads are from adjacent locations in the same structure and the target architecture has a conditional move instruction. This flag is enabled by default at -O2 and higher. -ftree-copy-prop Perform copy propagation on trees. This pass eliminates unnecessary copy operations. This flag is enabled by default at -O1 and higher. -fipa-pure-const Discover which functions are pure or constant. Enabled by default at -O1 and higher. -fipa-reference Discover which static variables do not escape the compilation unit. Enabled by default at -O1 and higher. -fipa-reference-addressable Discover read-only, write-only and non-addressable static variables. Enabled by default at -O1 and higher. -fipa-stack-alignment Reduce stack alignment on call sites if possible. Enabled by default. -fipa-pta Perform interprocedural pointer analysis and interprocedural modification and reference analysis. This option can cause excessive memory and compile-time usage on large compilation units. It is not enabled by default at any optimization level. -fipa-profile Perform interprocedural profile propagation. The functions called only from cold functions are marked as cold. Also functions executed once (such as "cold", "noreturn", static constructors or destructors) are identified. Cold functions and loop less parts of functions executed once are then optimized for size. Enabled by default at -O1 and higher. -fipa-modref Perform interprocedural mod/ref analysis. This optimization analyzes the side effects of functions (memory locations that are modified or referenced) and enables better optimization across the function call boundary. This flag is enabled by default at -O1 and higher. -fipa-cp Perform interprocedural constant propagation. This optimization analyzes the program to determine when values passed to functions are constants and then optimizes accordingly. This optimization can substantially increase performance if the application has constants passed to functions. This flag is enabled by default at -O2, -Os and -O3. It is also enabled by -fprofile-use and -fauto-profile. -fipa-cp-clone Perform function cloning to make interprocedural constant propagation stronger. When enabled, interprocedural constant propagation performs function cloning when externally visible function can be called with constant arguments. Because this optimization can create multiple copies of functions, it may significantly increase code size (see --param ipa-cp-unit-growth=value). This flag is enabled by default at -O3. It is also enabled by -fprofile-use and -fauto-profile. -fipa-bit-cp When enabled, perform interprocedural bitwise constant propagation. This flag is enabled by default at -O2 and by -fprofile-use and -fauto-profile. It requires that -fipa-cp is enabled. -fipa-vrp When enabled, perform interprocedural propagation of value ranges. This flag is enabled by default at -O2. It requires that -fipa-cp is enabled. -fipa-icf Perform Identical Code Folding for functions and read-only variables. The optimization reduces code size and may disturb unwind stacks by replacing a function by equivalent one with a different name. The optimization works more effectively with link- time optimization enabled. Although the behavior is similar to the Gold Linker's ICF optimization, GCC ICF works on different levels and thus the optimizations are not same - there are equivalences that are found only by GCC and equivalences found only by Gold. This flag is enabled by default at -O2 and -Os. -flive-patching=level Control GCC's optimizations to produce output suitable for live- patching. If the compiler's optimization uses a function's body or information extracted from its body to optimize/change another function, the latter is called an impacted function of the former. If a function is patched, its impacted functions should be patched too. The impacted functions are determined by the compiler's interprocedural optimizations. For example, a caller is impacted when inlining a function into its caller, cloning a function and changing its caller to call this new clone, or extracting a function's pureness/constness information to optimize its direct or indirect callers, etc. Usually, the more IPA optimizations enabled, the larger the number of impacted functions for each function. In order to control the number of impacted functions and more easily compute the list of impacted function, IPA optimizations can be partially enabled at two different levels. The level argument should be one of the following: inline-clone Only enable inlining and cloning optimizations, which includes inlining, cloning, interprocedural scalar replacement of aggregates and partial inlining. As a result, when patching a function, all its callers and its clones' callers are impacted, therefore need to be patched as well. -flive-patching=inline-clone disables the following optimization flags: -fwhole-program -fipa-pta -fipa-reference -fipa-ra -fipa-icf -fipa-icf-functions -fipa-icf-variables -fipa-bit-cp -fipa-vrp -fipa-pure-const -fipa-reference-addressable -fipa-stack-alignment -fipa-modref inline-only-static Only enable inlining of static functions. As a result, when patching a static function, all its callers are impacted and so need to be patched as well. In addition to all the flags that -flive-patching=inline-clone disables, -flive-patching=inline-only-static disables the following additional optimization flags: -fipa-cp-clone -fipa-sra -fpartial-inlining -fipa-cp When -flive-patching is specified without any value, the default value is inline-clone. This flag is disabled by default. Note that -flive-patching is not supported with link-time optimization (-flto). -fisolate-erroneous-paths-dereference Detect paths that trigger erroneous or undefined behavior due to dereferencing a null pointer. Isolate those paths from the main control flow and turn the statement with erroneous or undefined behavior into a trap. This flag is enabled by default at -O2 and higher and depends on -fdelete-null-pointer-checks also being enabled. -fisolate-erroneous-paths-attribute Detect paths that trigger erroneous or undefined behavior due to a null value being used in a way forbidden by a "returns_nonnull" or "nonnull" attribute. Isolate those paths from the main control flow and turn the statement with erroneous or undefined behavior into a trap. This is not currently enabled, but may be enabled by -O2 in the future. -ftree-sink Perform forward store motion on trees. This flag is enabled by default at -O1 and higher. -ftree-bit-ccp Perform sparse conditional bit constant propagation on trees and propagate pointer alignment information. This pass only operates on local scalar variables and is enabled by default at -O1 and higher, except for -Og. It requires that -ftree-ccp is enabled. -ftree-ccp Perform sparse conditional constant propagation (CCP) on trees. This pass only operates on local scalar variables and is enabled by default at -O1 and higher. -fssa-backprop Propagate information about uses of a value up the definition chain in order to simplify the definitions. For example, this pass strips sign operations if the sign of a value never matters. The flag is enabled by default at -O1 and higher. -fssa-phiopt Perform pattern matching on SSA PHI nodes to optimize conditional code. This pass is enabled by default at -O1 and higher, except for -Og. -ftree-switch-conversion Perform conversion of simple initializations in a switch to initializations from a scalar array. This flag is enabled by default at -O2 and higher. -ftree-tail-merge Look for identical code sequences. When found, replace one with a jump to the other. This optimization is known as tail merging or cross jumping. This flag is enabled by default at -O2 and higher. The compilation time in this pass can be limited using max-tail- merge-comparisons parameter and max-tail-merge-iterations parameter. -ftree-dce Perform dead code elimination (DCE) on trees. This flag is enabled by default at -O1 and higher. -ftree-builtin-call-dce Perform conditional dead code elimination (DCE) for calls to built- in functions that may set "errno" but are otherwise free of side effects. This flag is enabled by default at -O2 and higher if -Os is not also specified. -ffinite-loops Assume that a loop with an exit will eventually take the exit and not loop indefinitely. This allows the compiler to remove loops that otherwise have no side-effects, not considering eventual endless looping as such. This option is enabled by default at -O2 for C++ with -std=c++11 or higher. -ftree-dominator-opts Perform a variety of simple scalar cleanups (constant/copy propagation, redundancy elimination, range propagation and expression simplification) based on a dominator tree traversal. This also performs jump threading (to reduce jumps to jumps). This flag is enabled by default at -O1 and higher. -ftree-dse Perform dead store elimination (DSE) on trees. A dead store is a store into a memory location that is later overwritten by another store without any intervening loads. In this case the earlier store can be deleted. This flag is enabled by default at -O1 and higher. -ftree-ch Perform loop header copying on trees. This is beneficial since it increases effectiveness of code motion optimizations. It also saves one jump. This flag is enabled by default at -O1 and higher. It is not enabled for -Os, since it usually increases code size. -ftree-loop-optimize Perform loop optimizations on trees. This flag is enabled by default at -O1 and higher. -ftree-loop-linear -floop-strip-mine -floop-block Perform loop nest optimizations. Same as -floop-nest-optimize. To use this code transformation, GCC has to be configured with --with-isl to enable the Graphite loop transformation infrastructure. -fgraphite-identity Enable the identity transformation for graphite. For every SCoP we generate the polyhedral representation and transform it back to gimple. Using -fgraphite-identity we can check the costs or benefits of the GIMPLE -> GRAPHITE -> GIMPLE transformation. Some minimal optimizations are also performed by the code generator isl, like index splitting and dead code elimination in loops. -floop-nest-optimize Enable the isl based loop nest optimizer. This is a generic loop nest optimizer based on the Pluto optimization algorithms. It calculates a loop structure optimized for data-locality and parallelism. This option is experimental. -floop-parallelize-all Use the Graphite data dependence analysis to identify loops that can be parallelized. Parallelize all the loops that can be analyzed to not contain loop carried dependences without checking that it is profitable to parallelize the loops. -ftree-coalesce-vars While transforming the program out of the SSA representation, attempt to reduce copying by coalescing versions of different user- defined variables, instead of just compiler temporaries. This may severely limit the ability to debug an optimized program compiled with -fno-var-tracking-assignments. In the negated form, this flag prevents SSA coalescing of user variables. This option is enabled by default if optimization is enabled, and it does very little otherwise. -ftree-loop-if-convert Attempt to transform conditional jumps in the innermost loops to branch-less equivalents. The intent is to remove control-flow from the innermost loops in order to improve the ability of the vectorization pass to handle these loops. This is enabled by default if vectorization is enabled. -ftree-loop-distribution Perform loop distribution. This flag can improve cache performance on big loop bodies and allow further loop optimizations, like parallelization or vectorization, to take place. For example, the loop DO I = 1, N A(I) = B(I) + C D(I) = E(I) * F ENDDO is transformed to DO I = 1, N A(I) = B(I) + C ENDDO DO I = 1, N D(I) = E(I) * F ENDDO This flag is enabled by default at -O3. It is also enabled by -fprofile-use and -fauto-profile. -ftree-loop-distribute-patterns Perform loop distribution of patterns that can be code generated with calls to a library. This flag is enabled by default at -O2 and higher, and by -fprofile-use and -fauto-profile. This pass distributes the initialization loops and generates a call to memset zero. For example, the loop DO I = 1, N A(I) = 0 B(I) = A(I) + I ENDDO is transformed to DO I = 1, N A(I) = 0 ENDDO DO I = 1, N B(I) = A(I) + I ENDDO and the initialization loop is transformed into a call to memset zero. This flag is enabled by default at -O3. It is also enabled by -fprofile-use and -fauto-profile. -floop-interchange Perform loop interchange outside of graphite. This flag can improve cache performance on loop nest and allow further loop optimizations, like vectorization, to take place. For example, the loop for (int i = 0; i < N; i++) for (int j = 0; j < N; j++) for (int k = 0; k < N; k++) c[i][j] = c[i][j] + a[i][k]*b[k][j]; is transformed to for (int i = 0; i < N; i++) for (int k = 0; k < N; k++) for (int j = 0; j < N; j++) c[i][j] = c[i][j] + a[i][k]*b[k][j]; This flag is enabled by default at -O3. It is also enabled by -fprofile-use and -fauto-profile. -floop-unroll-and-jam Apply unroll and jam transformations on feasible loops. In a loop nest this unrolls the outer loop by some factor and fuses the resulting multiple inner loops. This flag is enabled by default at -O3. It is also enabled by -fprofile-use and -fauto-profile. -ftree-loop-im Perform loop invariant motion on trees. This pass moves only invariants that are hard to handle at RTL level (function calls, operations that expand to nontrivial sequences of insns). With -funswitch-loops it also moves operands of conditions that are invariant out of the loop, so that we can use just trivial invariantness analysis in loop unswitching. The pass also includes store motion. -ftree-loop-ivcanon Create a canonical counter for number of iterations in loops for which determining number of iterations requires complicated analysis. Later optimizations then may determine the number easily. Useful especially in connection with unrolling. -ftree-scev-cprop Perform final value replacement. If a variable is modified in a loop in such a way that its value when exiting the loop can be determined using only its initial value and the number of loop iterations, replace uses of the final value by such a computation, provided it is sufficiently cheap. This reduces data dependencies and may allow further simplifications. Enabled by default at -O1 and higher. -fivopts Perform induction variable optimizations (strength reduction, induction variable merging and induction variable elimination) on trees. -ftree-parallelize-loops=n Parallelize loops, i.e., split their iteration space to run in n threads. This is only possible for loops whose iterations are independent and can be arbitrarily reordered. The optimization is only profitable on multiprocessor machines, for loops that are CPU- intensive, rather than constrained e.g. by memory bandwidth. This option implies -pthread, and thus is only supported on targets that have support for -pthread. -ftree-pta Perform function-local points-to analysis on trees. This flag is enabled by default at -O1 and higher, except for -Og. -ftree-sra Perform scalar replacement of aggregates. This pass replaces structure references with scalars to prevent committing structures to memory too early. This flag is enabled by default at -O1 and higher, except for -Og. -fstore-merging Perform merging of narrow stores to consecutive memory addresses. This pass merges contiguous stores of immediate values narrower than a word into fewer wider stores to reduce the number of instructions. This is enabled by default at -O2 and higher as well as -Os. -ftree-ter Perform temporary expression replacement during the SSA->normal phase. Single use/single def temporaries are replaced at their use location with their defining expression. This results in non- GIMPLE code, but gives the expanders much more complex trees to work on resulting in better RTL generation. This is enabled by default at -O1 and higher. -ftree-slsr Perform straight-line strength reduction on trees. This recognizes related expressions involving multiplications and replaces them by less expensive calculations when possible. This is enabled by default at -O1 and higher. -ftree-vectorize Perform vectorization on trees. This flag enables -ftree-loop-vectorize and -ftree-slp-vectorize if not explicitly specified. -ftree-loop-vectorize Perform loop vectorization on trees. This flag is enabled by default at -O2 and by -ftree-vectorize, -fprofile-use, and -fauto-profile. -ftree-slp-vectorize Perform basic block vectorization on trees. This flag is enabled by default at -O2 and by -ftree-vectorize, -fprofile-use, and -fauto-profile. -ftrivial-auto-var-init=choice Initialize automatic variables with either a pattern or with zeroes to increase the security and predictability of a program by preventing uninitialized memory disclosure and use. GCC still considers an automatic variable that doesn't have an explicit initializer as uninitialized, -Wuninitialized and -Wanalyzer-use-of-uninitialized-value will still report warning messages on such automatic variables and the compiler will perform optimization as if the variable were uninitialized. With this option, GCC will also initialize any padding of automatic variables that have structure or union types to zeroes. However, the current implementation cannot initialize automatic variables that are declared between the controlling expression and the first case of a "switch" statement. Using -Wtrivial-auto-var-init to report all such cases. The three values of choice are: * uninitialized doesn't initialize any automatic variables. This is C and C++'s default. * pattern Initialize automatic variables with values which will likely transform logic bugs into crashes down the line, are easily recognized in a crash dump and without being values that programmers can rely on for useful program semantics. The current value is byte-repeatable pattern with byte "0xFE". The values used for pattern initialization might be changed in the future. * zero Initialize automatic variables with zeroes. The default is uninitialized. You can control this behavior for a specific variable by using the variable attribute "uninitialized". -fvect-cost-model=model Alter the cost model used for vectorization. The model argument should be one of unlimited, dynamic, cheap or very-cheap. With the unlimited model the vectorized code-path is assumed to be profitable while with the dynamic model a runtime check guards the vectorized code-path to enable it only for iteration counts that will likely execute faster than when executing the original scalar loop. The cheap model disables vectorization of loops where doing so would be cost prohibitive for example due to required runtime checks for data dependence or alignment but otherwise is equal to the dynamic model. The very-cheap model only allows vectorization if the vector code would entirely replace the scalar code that is being vectorized. For example, if each iteration of a vectorized loop would only be able to handle exactly four iterations of the scalar loop, the very-cheap model would only allow vectorization if the scalar iteration count is known to be a multiple of four. The default cost model depends on other optimization flags and is either dynamic or cheap. -fsimd-cost-model=model Alter the cost model used for vectorization of loops marked with the OpenMP simd directive. The model argument should be one of unlimited, dynamic, cheap. All values of model have the same meaning as described in -fvect-cost-model and by default a cost model defined with -fvect-cost-model is used. -ftree-vrp Perform Value Range Propagation on trees. This is similar to the constant propagation pass, but instead of values, ranges of values are propagated. This allows the optimizers to remove unnecessary range checks like array bound checks and null pointer checks. This is enabled by default at -O2 and higher. Null pointer check elimination is only done if -fdelete-null-pointer-checks is enabled. -fsplit-paths Split paths leading to loop backedges. This can improve dead code elimination and common subexpression elimination. This is enabled by default at -O3 and above. -fsplit-ivs-in-unroller Enables expression of values of induction variables in later iterations of the unrolled loop using the value in the first iteration. This breaks long dependency chains, thus improving efficiency of the scheduling passes. A combination of -fweb and CSE is often sufficient to obtain the same effect. However, that is not reliable in cases where the loop body is more complicated than a single basic block. It also does not work at all on some architectures due to restrictions in the CSE pass. This optimization is enabled by default. -fvariable-expansion-in-unroller With this option, the compiler creates multiple copies of some local variables when unrolling a loop, which can result in superior code. This optimization is enabled by default for PowerPC targets, but disabled by default otherwise. -fpartial-inlining Inline parts of functions. This option has any effect only when inlining itself is turned on by the -finline-functions or -finline-small-functions options. Enabled at levels -O2, -O3, -Os. -fpredictive-commoning Perform predictive commoning optimization, i.e., reusing computations (especially memory loads and stores) performed in previous iterations of loops. This option is enabled at level -O3. It is also enabled by -fprofile-use and -fauto-profile. -fprefetch-loop-arrays If supported by the target machine, generate instructions to prefetch memory to improve the performance of loops that access large arrays. This option may generate better or worse code; results are highly dependent on the structure of loops within the source code. Disabled at level -Os. -fno-printf-return-value Do not substitute constants for known return value of formatted output functions such as "sprintf", "snprintf", "vsprintf", and "vsnprintf" (but not "printf" of "fprintf"). This transformation allows GCC to optimize or even eliminate branches based on the known return value of these functions called with arguments that are either constant, or whose values are known to be in a range that makes determining the exact return value possible. For example, when -fprintf-return-value is in effect, both the branch and the body of the "if" statement (but not the call to "snprint") can be optimized away when "i" is a 32-bit or smaller integer because the return value is guaranteed to be at most 8. char buf[9]; if (snprintf (buf, "%08x", i) >= sizeof buf) ... The -fprintf-return-value option relies on other optimizations and yields best results with -O2 and above. It works in tandem with the -Wformat-overflow and -Wformat-truncation options. The -fprintf-return-value option is enabled by default. -fno-peephole -fno-peephole2 Disable any machine-specific peephole optimizations. The difference between -fno-peephole and -fno-peephole2 is in how they are implemented in the compiler; some targets use one, some use the other, a few use both. -fpeephole is enabled by default. -fpeephole2 enabled at levels -O2, -O3, -Os. -fno-guess-branch-probability Do not guess branch probabilities using heuristics. GCC uses heuristics to guess branch probabilities if they are not provided by profiling feedback (-fprofile-arcs). These heuristics are based on the control flow graph. If some branch probabilities are specified by "__builtin_expect", then the heuristics are used to guess branch probabilities for the rest of the control flow graph, taking the "__builtin_expect" info into account. The interactions between the heuristics and "__builtin_expect" can be complex, and in some cases, it may be useful to disable the heuristics so that the effects of "__builtin_expect" are easier to understand. It is also possible to specify expected probability of the expression with "__builtin_expect_with_probability" built-in function. The default is -fguess-branch-probability at levels -O, -O2, -O3, -Os. -freorder-blocks Reorder basic blocks in the compiled function in order to reduce number of taken branches and improve code locality. Enabled at levels -O1, -O2, -O3, -Os. -freorder-blocks-algorithm=algorithm Use the specified algorithm for basic block reordering. The algorithm argument can be simple, which does not increase code size (except sometimes due to secondary effects like alignment), or stc, the "software trace cache" algorithm, which tries to put all often executed code together, minimizing the number of branches executed by making extra copies of code. The default is simple at levels -O1, -Os, and stc at levels -O2, -O3. -freorder-blocks-and-partition In addition to reordering basic blocks in the compiled function, in order to reduce number of taken branches, partitions hot and cold basic blocks into separate sections of the assembly and .o files, to improve paging and cache locality performance. This optimization is automatically turned off in the presence of exception handling or unwind tables (on targets using setjump/longjump or target specific scheme), for linkonce sections, for functions with a user-defined section attribute and on any architecture that does not support named sections. When -fsplit-stack is used this option is not enabled by default (to avoid linker errors), but may be enabled explicitly (if using a working linker). Enabled for x86 at levels -O2, -O3, -Os. -freorder-functions Reorder functions in the object file in order to improve code locality. This is implemented by using special subsections ".text.hot" for most frequently executed functions and ".text.unlikely" for unlikely executed functions. Reordering is done by the linker so object file format must support named sections and linker must place them in a reasonable way. This option isn't effective unless you either provide profile feedback (see -fprofile-arcs for details) or manually annotate functions with "hot" or "cold" attributes. Enabled at levels -O2, -O3, -Os. -fstrict-aliasing Allow the compiler to assume the strictest aliasing rules applicable to the language being compiled. For C (and C++), this activates optimizations based on the type of expressions. In particular, an object of one type is assumed never to reside at the same address as an object of a different type, unless the types are almost the same. For example, an "unsigned int" can alias an "int", but not a "void*" or a "double". A character type may alias any other type. Pay special attention to code like this: union a_union { int i; double d; }; int f() { union a_union t; t.d = 3.0; return t.i; } The practice of reading from a different union member than the one most recently written to (called "type-punning") is common. Even with -fstrict-aliasing, type-punning is allowed, provided the memory is accessed through the union type. So, the code above works as expected. However, this code might not: int f() { union a_union t; int* ip; t.d = 3.0; ip = &t.i; return *ip; } Similarly, access by taking the address, casting the resulting pointer and dereferencing the result has undefined behavior, even if the cast uses a union type, e.g.: int f() { double d = 3.0; return ((union a_union *) &d)->i; } The -fstrict-aliasing option is enabled at levels -O2, -O3, -Os. -fipa-strict-aliasing Controls whether rules of -fstrict-aliasing are applied across function boundaries. Note that if multiple functions gets inlined into a single function the memory accesses are no longer considered to be crossing a function boundary. The -fipa-strict-aliasing option is enabled by default and is effective only in combination with -fstrict-aliasing. -falign-functions -falign-functions=n -falign-functions=n:m -falign-functions=n:m:n2 -falign-functions=n:m:n2:m2 Align the start of functions to the next power-of-two greater than or equal to n, skipping up to m-1 bytes. This ensures that at least the first m bytes of the function can be fetched by the CPU without crossing an n-byte alignment boundary. If m is not specified, it defaults to n. Examples: -falign-functions=32 aligns functions to the next 32-byte boundary, -falign-functions=24 aligns to the next 32-byte boundary only if this can be done by skipping 23 bytes or less, -falign-functions=32:7 aligns to the next 32-byte boundary only if this can be done by skipping 6 bytes or less. The second pair of n2:m2 values allows you to specify a secondary alignment: -falign-functions=64:7:32:3 aligns to the next 64-byte boundary if this can be done by skipping 6 bytes or less, otherwise aligns to the next 32-byte boundary if this can be done by skipping 2 bytes or less. If m2 is not specified, it defaults to n2. Some assemblers only support this flag when n is a power of two; in that case, it is rounded up. -fno-align-functions and -falign-functions=1 are equivalent and mean that functions are not aligned. If n is not specified or is zero, use a machine-dependent default. The maximum allowed n option value is 65536. Enabled at levels -O2, -O3. -flimit-function-alignment If this option is enabled, the compiler tries to avoid unnecessarily overaligning functions. It attempts to instruct the assembler to align by the amount specified by -falign-functions, but not to skip more bytes than the size of the function. -falign-labels -falign-labels=n -falign-labels=n:m -falign-labels=n:m:n2 -falign-labels=n:m:n2:m2 Align all branch targets to a power-of-two boundary. Parameters of this option are analogous to the -falign-functions option. -fno-align-labels and -falign-labels=1 are equivalent and mean that labels are not aligned. If -falign-loops or -falign-jumps are applicable and are greater than this value, then their values are used instead. If n is not specified or is zero, use a machine-dependent default which is very likely to be 1, meaning no alignment. The maximum allowed n option value is 65536. Enabled at levels -O2, -O3. -falign-loops -falign-loops=n -falign-loops=n:m -falign-loops=n:m:n2 -falign-loops=n:m:n2:m2 Align loops to a power-of-two boundary. If the loops are executed many times, this makes up for any execution of the dummy padding instructions. If -falign-labels is greater than this value, then its value is used instead. Parameters of this option are analogous to the -falign-functions option. -fno-align-loops and -falign-loops=1 are equivalent and mean that loops are not aligned. The maximum allowed n option value is 65536. If n is not specified or is zero, use a machine-dependent default. Enabled at levels -O2, -O3. -falign-jumps -falign-jumps=n -falign-jumps=n:m -falign-jumps=n:m:n2 -falign-jumps=n:m:n2:m2 Align branch targets to a power-of-two boundary, for branch targets where the targets can only be reached by jumping. In this case, no dummy operations need be executed. If -falign-labels is greater than this value, then its value is used instead. Parameters of this option are analogous to the -falign-functions option. -fno-align-jumps and -falign-jumps=1 are equivalent and mean that loops are not aligned. If n is not specified or is zero, use a machine-dependent default. The maximum allowed n option value is 65536. Enabled at levels -O2, -O3. -fno-allocation-dce Do not remove unused C++ allocations in dead code elimination. -fallow-store-data-races Allow the compiler to perform optimizations that may introduce new data races on stores, without proving that the variable cannot be concurrently accessed by other threads. Does not affect optimization of local data. It is safe to use this option if it is known that global data will not be accessed by multiple threads. Examples of optimizations enabled by -fallow-store-data-races include hoisting or if-conversions that may cause a value that was already in memory to be re-written with that same value. Such re- writing is safe in a single threaded context but may be unsafe in a multi-threaded context. Note that on some processors, if- conversions may be required in order to enable vectorization. Enabled at level -Ofast. -funit-at-a-time This option is left for compatibility reasons. -funit-at-a-time has no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder and -fno-section-anchors. Enabled by default. -fno-toplevel-reorder Do not reorder top-level functions, variables, and "asm" statements. Output them in the same order that they appear in the input file. When this option is used, unreferenced static variables are not removed. This option is intended to support existing code that relies on a particular ordering. For new code, it is better to use attributes when possible. -ftoplevel-reorder is the default at -O1 and higher, and also at -O0 if -fsection-anchors is explicitly requested. Additionally -fno-toplevel-reorder implies -fno-section-anchors. -funreachable-traps With this option, the compiler turns calls to "__builtin_unreachable" into traps, instead of using them for optimization. This also affects any such calls implicitly generated by the compiler. This option has the same effect as -fsanitize=unreachable -fsanitize-trap=unreachable, but does not affect the values of those options. If -fsanitize=unreachable is enabled, that option takes priority over this one. This option is enabled by default at -O0 and -Og. -fweb Constructs webs as commonly used for register allocation purposes and assign each web individual pseudo register. This allows the register allocation pass to operate on pseudos directly, but also strengthens several other optimization passes, such as CSE, loop optimizer and trivial dead code remover. It can, however, make debugging impossible, since variables no longer stay in a "home register". Enabled by default with -funroll-loops. -fwhole-program Assume that the current compilation unit represents the whole program being compiled. All public functions and variables with the exception of "main" and those merged by attribute "externally_visible" become static functions and in effect are optimized more aggressively by interprocedural optimizers. With -flto this option has a limited use. In most cases the precise list of symbols used or exported from the binary is known the resolution info passed to the link-time optimizer by the linker plugin. It is still useful if no linker plugin is used or during incremental link step when final code is produced (with -flto -flinker-output=nolto-rel). -flto[=n] This option runs the standard link-time optimizer. When invoked with source code, it generates GIMPLE (one of GCC's internal representations) and writes it to special ELF sections in the object file. When the object files are linked together, all the function bodies are read from these ELF sections and instantiated as if they had been part of the same translation unit. To use the link-time optimizer, -flto and optimization options should be specified at compile time and during the final link. It is recommended that you compile all the files participating in the same link with the same options and also specify those options at link time. For example: gcc -c -O2 -flto foo.c gcc -c -O2 -flto bar.c gcc -o myprog -flto -O2 foo.o bar.o The first two invocations to GCC save a bytecode representation of GIMPLE into special ELF sections inside foo.o and bar.o. The final invocation reads the GIMPLE bytecode from foo.o and bar.o, merges the two files into a single internal image, and compiles the result as usual. Since both foo.o and bar.o are merged into a single image, this causes all the interprocedural analyses and optimizations in GCC to work across the two files as if they were a single one. This means, for example, that the inliner is able to inline functions in bar.o into functions in foo.o and vice-versa. Another (simpler) way to enable link-time optimization is: gcc -o myprog -flto -O2 foo.c bar.c The above generates bytecode for foo.c and bar.c, merges them together into a single GIMPLE representation and optimizes them as usual to produce myprog. The important thing to keep in mind is that to enable link-time optimizations you need to use the GCC driver to perform the link step. GCC automatically performs link-time optimization if any of the objects involved were compiled with the -flto command-line option. You can always override the automatic decision to do link- time optimization by passing -fno-lto to the link command. To make whole program optimization effective, it is necessary to make certain whole program assumptions. The compiler needs to know what functions and variables can be accessed by libraries and runtime outside of the link-time optimized unit. When supported by the linker, the linker plugin (see -fuse-linker-plugin) passes information to the compiler about used and externally visible symbols. When the linker plugin is not available, -fwhole-program should be used to allow the compiler to make these assumptions, which leads to more aggressive optimization decisions. When a file is compiled with -flto without -fuse-linker-plugin, the generated object file is larger than a regular object file because it contains GIMPLE bytecodes and the usual final code (see -ffat-lto-objects). This means that object files with LTO information can be linked as normal object files; if -fno-lto is passed to the linker, no interprocedural optimizations are applied. Note that when -fno-fat-lto-objects is enabled the compile stage is faster but you cannot perform a regular, non-LTO link on them. When producing the final binary, GCC only applies link-time optimizations to those files that contain bytecode. Therefore, you can mix and match object files and libraries with GIMPLE bytecodes and final object code. GCC automatically selects which files to optimize in LTO mode and which files to link without further processing. Generally, options specified at link time override those specified at compile time, although in some cases GCC attempts to infer link- time options from the settings used to compile the input files. If you do not specify an optimization level option -O at link time, then GCC uses the highest optimization level used when compiling the object files. Note that it is generally ineffective to specify an optimization level option only at link time and not at compile time, for two reasons. First, compiling without optimization suppresses compiler passes that gather information needed for effective optimization at link time. Second, some early optimization passes can be performed only at compile time and not at link time. There are some code generation flags preserved by GCC when generating bytecodes, as they need to be used during the final link. Currently, the following options and their settings are taken from the first object file that explicitly specifies them: -fcommon, -fexceptions, -fnon-call-exceptions, -fgnu-tm and all the -m target flags. The following options -fPIC, -fpic, -fpie and -fPIE are combined based on the following scheme: B<-fPIC> + B<-fpic> = B<-fpic> B<-fPIC> + B<-fno-pic> = B<-fno-pic> B<-fpic/-fPIC> + (no option) = (no option) B<-fPIC> + B<-fPIE> = B<-fPIE> B<-fpic> + B<-fPIE> = B<-fpie> B<-fPIC/-fpic> + B<-fpie> = B<-fpie> Certain ABI-changing flags are required to match in all compilation units, and trying to override this at link time with a conflicting value is ignored. This includes options such as -freg-struct-return and -fpcc-struct-return. Other options such as -ffp-contract, -fno-strict-overflow, -fwrapv, -fno-trapv or -fno-strict-aliasing are passed through to the link stage and merged conservatively for conflicting translation units. Specifically -fno-strict-overflow, -fwrapv and -fno-trapv take precedence; and for example -ffp-contract=off takes precedence over -ffp-contract=fast. You can override them at link time. Diagnostic options such as -Wstringop-overflow are passed through to the link stage and their setting matches that of the compile- step at function granularity. Note that this matters only for diagnostics emitted during optimization. Note that code transforms such as inlining can lead to warnings being enabled or disabled for regions if code not consistent with the setting at compile time. When you need to pass options to the assembler via -Wa or -Xassembler make sure to either compile such translation units with -fno-lto or consistently use the same assembler options on all translation units. You can alternatively also specify assembler options at LTO link time. To enable debug info generation you need to supply -g at compile time. If any of the input files at link time were built with debug info generation enabled the link will enable debug info generation as well. Any elaborate debug info settings like the dwarf level -gdwarf-5 need to be explicitly repeated at the linker command line and mixing different settings in different translation units is discouraged. If LTO encounters objects with C linkage declared with incompatible types in separate translation units to be linked together (undefined behavior according to ISO C99 6.2.7), a non-fatal diagnostic may be issued. The behavior is still undefined at run time. Similar diagnostics may be raised for other languages. Another feature of LTO is that it is possible to apply interprocedural optimizations on files written in different languages: gcc -c -flto foo.c g++ -c -flto bar.cc gfortran -c -flto baz.f90 g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran Notice that the final link is done with g++ to get the C++ runtime libraries and -lgfortran is added to get the Fortran runtime libraries. In general, when mixing languages in LTO mode, you should use the same link command options as when mixing languages in a regular (non-LTO) compilation. If object files containing GIMPLE bytecode are stored in a library archive, say libfoo.a, it is possible to extract and use them in an LTO link if you are using a linker with plugin support. To create static libraries suitable for LTO, use gcc-ar and gcc-ranlib instead of ar and ranlib; to show the symbols of object files with GIMPLE bytecode, use gcc-nm. Those commands require that ar, ranlib and nm have been compiled with plugin support. At link time, use the flag -fuse-linker-plugin to ensure that the library participates in the LTO optimization process: gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo With the linker plugin enabled, the linker extracts the needed GIMPLE files from libfoo.a and passes them on to the running GCC to make them part of the aggregated GIMPLE image to be optimized. If you are not using a linker with plugin support and/or do not enable the linker plugin, then the objects inside libfoo.a are extracted and linked as usual, but they do not participate in the LTO optimization process. In order to make a static library suitable for both LTO optimization and usual linkage, compile its object files with -flto -ffat-lto-objects. Link-time optimizations do not require the presence of the whole program to operate. If the program does not require any symbols to be exported, it is possible to combine -flto and -fwhole-program to allow the interprocedural optimizers to use more aggressive assumptions which may lead to improved optimization opportunities. Use of -fwhole-program is not needed when linker plugin is active (see -fuse-linker-plugin). The current implementation of LTO makes no attempt to generate bytecode that is portable between different types of hosts. The bytecode files are versioned and there is a strict version check, so bytecode files generated in one version of GCC do not work with an older or newer version of GCC. Link-time optimization does not work well with generation of debugging information on systems other than those using a combination of ELF and DWARF. If you specify the optional n, the optimization and code generation done at link time is executed in parallel using n parallel jobs by utilizing an installed make program. The environment variable MAKE may be used to override the program used. You can also specify -flto=jobserver to use GNU make's job server mode to determine the number of parallel jobs. This is useful when the Makefile calling GCC is already executing in parallel. You must prepend a + to the command recipe in the parent Makefile for this to work. This option likely only works if MAKE is GNU make. Even without the option value, GCC tries to automatically detect a running GNU make's job server. Use -flto=auto to use GNU make's job server, if available, or otherwise fall back to autodetection of the number of CPU threads present in your system. -flto-partition=alg Specify the partitioning algorithm used by the link-time optimizer. The value is either 1to1 to specify a partitioning mirroring the original source files or balanced to specify partitioning into equally sized chunks (whenever possible) or max to create new partition for every symbol where possible. Specifying none as an algorithm disables partitioning and streaming completely. The default value is balanced. While 1to1 can be used as an workaround for various code ordering issues, the max partitioning is intended for internal testing only. The value one specifies that exactly one partition should be used while the value none bypasses partitioning and executes the link-time optimization step directly from the WPA phase. -flto-compression-level=n This option specifies the level of compression used for intermediate language written to LTO object files, and is only meaningful in conjunction with LTO mode (-flto). GCC currently supports two LTO compression algorithms. For zstd, valid values are 0 (no compression) to 19 (maximum compression), while zlib supports values from 0 to 9. Values outside this range are clamped to either minimum or maximum of the supported values. If the option is not given, a default balanced compression setting is used. -fuse-linker-plugin Enables the use of a linker plugin during link-time optimization. This option relies on plugin support in the linker, which is available in gold or in GNU ld 2.21 or newer. This option enables the extraction of object files with GIMPLE bytecode out of library archives. This improves the quality of optimization by exposing more code to the link-time optimizer. This information specifies what symbols can be accessed externally (by non-LTO object or during dynamic linking). Resulting code quality improvements on binaries (and shared libraries that use hidden visibility) are similar to -fwhole-program. See -flto for a description of the effect of this flag and how to use it. This option is enabled by default when LTO support in GCC is enabled and GCC was configured for use with a linker supporting plugins (GNU ld 2.21 or newer or gold). -ffat-lto-objects Fat LTO objects are object files that contain both the intermediate language and the object code. This makes them usable for both LTO linking and normal linking. This option is effective only when compiling with -flto and is ignored at link time. -fno-fat-lto-objects improves compilation time over plain LTO, but requires the complete toolchain to be aware of LTO. It requires a linker with linker plugin support for basic functionality. Additionally, nm, ar and ranlib need to support linker plugins to allow a full-featured build environment (capable of building static libraries etc). GCC provides the gcc-ar, gcc-nm, gcc-ranlib wrappers to pass the right options to these tools. With non fat LTO makefiles need to be modified to use them. Note that modern binutils provide plugin auto-load mechanism. Installing the linker plugin into $libdir/bfd-plugins has the same effect as usage of the command wrappers (gcc-ar, gcc-nm and gcc- ranlib). The default is -fno-fat-lto-objects on targets with linker plugin support. -fcompare-elim After register allocation and post-register allocation instruction splitting, identify arithmetic instructions that compute processor flags similar to a comparison operation based on that arithmetic. If possible, eliminate the explicit comparison operation. This pass only applies to certain targets that cannot explicitly represent the comparison operation before register allocation is complete. Enabled at levels -O1, -O2, -O3, -Os. -fcprop-registers After register allocation and post-register allocation instruction splitting, perform a copy-propagation pass to try to reduce scheduling dependencies and occasionally eliminate the copy. Enabled at levels -O1, -O2, -O3, -Os. -fprofile-correction Profiles collected using an instrumented binary for multi-threaded programs may be inconsistent due to missed counter updates. When this option is specified, GCC uses heuristics to correct or smooth out such inconsistencies. By default, GCC emits an error message when an inconsistent profile is detected. This option is enabled by -fauto-profile. -fprofile-partial-training With "-fprofile-use" all portions of programs not executed during train run are optimized agressively for size rather than speed. In some cases it is not practical to train all possible hot paths in the program. (For example, program may contain functions specific for a given hardware and trianing may not cover all hardware configurations program is run on.) With "-fprofile-partial-training" profile feedback will be ignored for all functions not executed during the train run leading them to be optimized as if they were compiled without profile feedback. This leads to better performance when train run is not representative but also leads to significantly bigger code. -fprofile-use -fprofile-use=path Enable profile feedback-directed optimizations, and the following optimizations, many of which are generally profitable only with profile feedback available: -fbranch-probabilities -fprofile-values -funroll-loops -fpeel-loops -ftracer -fvpt -finline-functions -fipa-cp -fipa-cp-clone -fipa-bit-cp -fpredictive-commoning -fsplit-loops -funswitch-loops -fgcse-after-reload -ftree-loop-vectorize -ftree-slp-vectorize -fvect-cost-model=dynamic -ftree-loop-distribute-patterns -fprofile-reorder-functions Before you can use this option, you must first generate profiling information. By default, GCC emits an error message if the feedback profiles do not match the source code. This error can be turned into a warning by using -Wno-error=coverage-mismatch. Note this may result in poorly optimized code. Additionally, by default, GCC also emits a warning message if the feedback profiles do not exist (see -Wmissing-profile). If path is specified, GCC looks at the path to find the profile feedback data files. See -fprofile-dir. -fauto-profile -fauto-profile=path Enable sampling-based feedback-directed optimizations, and the following optimizations, many of which are generally profitable only with profile feedback available: -fbranch-probabilities -fprofile-values -funroll-loops -fpeel-loops -ftracer -fvpt -finline-functions -fipa-cp -fipa-cp-clone -fipa-bit-cp -fpredictive-commoning -fsplit-loops -funswitch-loops -fgcse-after-reload -ftree-loop-vectorize -ftree-slp-vectorize -fvect-cost-model=dynamic -ftree-loop-distribute-patterns -fprofile-correction path is the name of a file containing AutoFDO profile information. If omitted, it defaults to fbdata.afdo in the current directory. Producing an AutoFDO profile data file requires running your program with the perf utility on a supported GNU/Linux target system. For more information, see <https://perf.wiki.kernel.org/>. E.g. perf record -e br_inst_retired:near_taken -b -o perf.data \ -- your_program Then use the create_gcov tool to convert the raw profile data to a format that can be used by GCC. You must also supply the unstripped binary for your program to this tool. See <https://github.com/google/autofdo>. E.g. create_gcov --binary=your_program.unstripped --profile=perf.data \ --gcov=profile.afdo The following options control compiler behavior regarding floating- point arithmetic. These options trade off between speed and correctness. All must be specifically enabled. -ffloat-store Do not store floating-point variables in registers, and inhibit other options that might change whether a floating-point value is taken from a register or memory. This option prevents undesirable excess precision on machines such as the 68000 where the floating registers (of the 68881) keep more precision than a "double" is supposed to have. Similarly for the x86 architecture. For most programs, the excess precision does only good, but a few programs rely on the precise definition of IEEE floating point. Use -ffloat-store for such programs, after modifying them to store all pertinent intermediate computations into variables. -fexcess-precision=style This option allows further control over excess precision on machines where floating-point operations occur in a format with more precision or range than the IEEE standard and interchange floating-point types. By default, -fexcess-precision=fast is in effect; this means that operations may be carried out in a wider precision than the types specified in the source if that would result in faster code, and it is unpredictable when rounding to the types specified in the source code takes place. When compiling C or C++, if -fexcess-precision=standard is specified then excess precision follows the rules specified in ISO C99 or C++; in particular, both casts and assignments cause values to be rounded to their semantic types (whereas -ffloat-store only affects assignments). This option is enabled by default for C or C++ if a strict conformance option such as -std=c99 or -std=c++17 is used. -ffast-math enables -fexcess-precision=fast by default regardless of whether a strict conformance option is used. -fexcess-precision=standard is not implemented for languages other than C or C++. On the x86, it has no effect if -mfpmath=sse or -mfpmath=sse+387 is specified; in the former case, IEEE semantics apply without excess precision, and in the latter, rounding is unpredictable. -ffast-math Sets the options -fno-math-errno, -funsafe-math-optimizations, -ffinite-math-only, -fno-rounding-math, -fno-signaling-nans, -fcx-limited-range and -fexcess-precision=fast. This option causes the preprocessor macro "__FAST_MATH__" to be defined. This option is not turned on by any -O option besides -Ofast since it can result in incorrect output for programs that depend on an exact implementation of IEEE or ISO rules/specifications for math functions. It may, however, yield faster code for programs that do not require the guarantees of these specifications. -fno-math-errno Do not set "errno" after calling math functions that are executed with a single instruction, e.g., "sqrt". A program that relies on IEEE exceptions for math error handling may want to use this flag for speed while maintaining IEEE arithmetic compatibility. This option is not turned on by any -O option since it can result in incorrect output for programs that depend on an exact implementation of IEEE or ISO rules/specifications for math functions. It may, however, yield faster code for programs that do not require the guarantees of these specifications. The default is -fmath-errno. On Darwin systems, the math library never sets "errno". There is therefore no reason for the compiler to consider the possibility that it might, and -fno-math-errno is the default. -funsafe-math-optimizations Allow optimizations for floating-point arithmetic that (a) assume that arguments and results are valid and (b) may violate IEEE or ANSI standards. When used at link time, it may include libraries or startup files that change the default FPU control word or other similar optimizations. This option is not turned on by any -O option since it can result in incorrect output for programs that depend on an exact implementation of IEEE or ISO rules/specifications for math functions. It may, however, yield faster code for programs that do not require the guarantees of these specifications. Enables -fno-signed-zeros, -fno-trapping-math, -fassociative-math and -freciprocal-math. The default is -fno-unsafe-math-optimizations. -fassociative-math Allow re-association of operands in series of floating-point operations. This violates the ISO C and C++ language standard by possibly changing computation result. NOTE: re-ordering may change the sign of zero as well as ignore NaNs and inhibit or create underflow or overflow (and thus cannot be used on code that relies on rounding behavior like "(x + 2**52) - 2**52". May also reorder floating-point comparisons and thus may not be used when ordered comparisons are required. This option requires that both -fno-signed-zeros and -fno-trapping-math be in effect. Moreover, it doesn't make much sense with -frounding-math. For Fortran the option is automatically enabled when both -fno-signed-zeros and -fno-trapping-math are in effect. The default is -fno-associative-math. -freciprocal-math Allow the reciprocal of a value to be used instead of dividing by the value if this enables optimizations. For example "x / y" can be replaced with "x * (1/y)", which is useful if "(1/y)" is subject to common subexpression elimination. Note that this loses precision and increases the number of flops operating on the value. The default is -fno-reciprocal-math. -ffinite-math-only Allow optimizations for floating-point arithmetic that assume that arguments and results are not NaNs or +-Infs. This option is not turned on by any -O option since it can result in incorrect output for programs that depend on an exact implementation of IEEE or ISO rules/specifications for math functions. It may, however, yield faster code for programs that do not require the guarantees of these specifications. The default is -fno-finite-math-only. -fno-signed-zeros Allow optimizations for floating-point arithmetic that ignore the signedness of zero. IEEE arithmetic specifies the behavior of distinct +0.0 and -0.0 values, which then prohibits simplification of expressions such as x+0.0 or 0.0*x (even with -ffinite-math-only). This option implies that the sign of a zero result isn't significant. The default is -fsigned-zeros. -fno-trapping-math Compile code assuming that floating-point operations cannot generate user-visible traps. These traps include division by zero, overflow, underflow, inexact result and invalid operation. This option requires that -fno-signaling-nans be in effect. Setting this option may allow faster code if one relies on "non-stop" IEEE arithmetic, for example. This option should never be turned on by any -O option since it can result in incorrect output for programs that depend on an exact implementation of IEEE or ISO rules/specifications for math functions. The default is -ftrapping-math. Future versions of GCC may provide finer control of this setting using C99's "FENV_ACCESS" pragma. This command-line option will be used along with -frounding-math to specify the default state for "FENV_ACCESS". -frounding-math Disable transformations and optimizations that assume default floating-point rounding behavior. This is round-to-zero for all floating point to integer conversions, and round-to-nearest for all other arithmetic truncations. This option should be specified for programs that change the FP rounding mode dynamically, or that may be executed with a non-default rounding mode. This option disables constant folding of floating-point expressions at compile time (which may be affected by rounding mode) and arithmetic transformations that are unsafe in the presence of sign-dependent rounding modes. The default is -fno-rounding-math. This option is experimental and does not currently guarantee to disable all GCC optimizations that are affected by rounding mode. Future versions of GCC may provide finer control of this setting using C99's "FENV_ACCESS" pragma. This command-line option will be used along with -ftrapping-math to specify the default state for "FENV_ACCESS". -fsignaling-nans Compile code assuming that IEEE signaling NaNs may generate user- visible traps during floating-point operations. Setting this option disables optimizations that may change the number of exceptions visible with signaling NaNs. This option implies -ftrapping-math. This option causes the preprocessor macro "__SUPPORT_SNAN__" to be defined. The default is -fno-signaling-nans. This option is experimental and does not currently guarantee to disable all GCC optimizations that affect signaling NaN behavior. -fno-fp-int-builtin-inexact Do not allow the built-in functions "ceil", "floor", "round" and "trunc", and their "float" and "long double" variants, to generate code that raises the "inexact" floating-point exception for noninteger arguments. ISO C99 and C11 allow these functions to raise the "inexact" exception, but ISO/IEC TS 18661-1:2014, the C bindings to IEEE 754-2008, as integrated into ISO C2X, does not allow these functions to do so. The default is -ffp-int-builtin-inexact, allowing the exception to be raised, unless C2X or a later C standard is selected. This option does nothing unless -ftrapping-math is in effect. Even if -fno-fp-int-builtin-inexact is used, if the functions generate a call to a library function then the "inexact" exception may be raised if the library implementation does not follow TS 18661. -fsingle-precision-constant Treat floating-point constants as single precision instead of implicitly converting them to double-precision constants. -fcx-limited-range When enabled, this option states that a range reduction step is not needed when performing complex division. Also, there is no checking whether the result of a complex multiplication or division is "NaN + I*NaN", with an attempt to rescue the situation in that case. The default is -fno-cx-limited-range, but is enabled by -ffast-math. This option controls the default setting of the ISO C99 "CX_LIMITED_RANGE" pragma. Nevertheless, the option applies to all languages. -fcx-fortran-rules Complex multiplication and division follow Fortran rules. Range reduction is done as part of complex division, but there is no checking whether the result of a complex multiplication or division is "NaN + I*NaN", with an attempt to rescue the situation in that case. The default is -fno-cx-fortran-rules. The following options control optimizations that may improve performance, but are not enabled by any -O options. This section includes experimental options that may produce broken code. -fbranch-probabilities After running a program compiled with -fprofile-arcs, you can compile it a second time using -fbranch-probabilities, to improve optimizations based on the number of times each branch was taken. When a program compiled with -fprofile-arcs exits, it saves arc execution counts to a file called sourcename.gcda for each source file. The information in this data file is very dependent on the structure of the generated code, so you must use the same source code and the same optimization options for both compilations. See details about the file naming in -fprofile-arcs. With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each JUMP_INSN and CALL_INSN. These can be used to improve optimization. Currently, they are only used in one place: in reorg.cc, instead of guessing which path a branch is most likely to take, the REG_BR_PROB values are used to exactly determine which path is taken more often. Enabled by -fprofile-use and -fauto-profile. -fprofile-values If combined with -fprofile-arcs, it adds code so that some data about values of expressions in the program is gathered. With -fbranch-probabilities, it reads back the data gathered from profiling values of expressions for usage in optimizations. Enabled by -fprofile-generate, -fprofile-use, and -fauto-profile. -fprofile-reorder-functions Function reordering based on profile instrumentation collects first time of execution of a function and orders these functions in ascending order. Enabled with -fprofile-use. -fvpt If combined with -fprofile-arcs, this option instructs the compiler to add code to gather information about values of expressions. With -fbranch-probabilities, it reads back the data gathered and actually performs the optimizations based on them. Currently the optimizations include specialization of division operations using the knowledge about the value of the denominator. Enabled with -fprofile-use and -fauto-profile. -frename-registers Attempt to avoid false dependencies in scheduled code by making use of registers left over after register allocation. This optimization most benefits processors with lots of registers. Depending on the debug information format adopted by the target, however, it can make debugging impossible, since variables no longer stay in a "home register". Enabled by default with -funroll-loops. -fschedule-fusion Performs a target dependent pass over the instruction stream to schedule instructions of same type together because target machine can execute them more efficiently if they are adjacent to each other in the instruction flow. Enabled at levels -O2, -O3, -Os. -ftracer Perform tail duplication to enlarge superblock size. This transformation simplifies the control flow of the function allowing other optimizations to do a better job. Enabled by -fprofile-use and -fauto-profile. -funroll-loops Unroll loops whose number of iterations can be determined at compile time or upon entry to the loop. -funroll-loops implies -frerun-cse-after-loop, -fweb and -frename-registers. It also turns on complete loop peeling (i.e. complete removal of loops with a small constant number of iterations). This option makes code larger, and may or may not make it run faster. Enabled by -fprofile-use and -fauto-profile. -funroll-all-loops Unroll all loops, even if their number of iterations is uncertain when the loop is entered. This usually makes programs run more slowly. -funroll-all-loops implies the same options as -funroll-loops. -fpeel-loops Peels loops for which there is enough information that they do not roll much (from profile feedback or static analysis). It also turns on complete loop peeling (i.e. complete removal of loops with small constant number of iterations). Enabled by -O3, -fprofile-use, and -fauto-profile. -fmove-loop-invariants Enables the loop invariant motion pass in the RTL loop optimizer. Enabled at level -O1 and higher, except for -Og. -fmove-loop-stores Enables the loop store motion pass in the GIMPLE loop optimizer. This moves invariant stores to after the end of the loop in exchange for carrying the stored value in a register across the iteration. Note for this option to have an effect -ftree-loop-im has to be enabled as well. Enabled at level -O1 and higher, except for -Og. -fsplit-loops Split a loop into two if it contains a condition that's always true for one side of the iteration space and false for the other. Enabled by -fprofile-use and -fauto-profile. -funswitch-loops Move branches with loop invariant conditions out of the loop, with duplicates of the loop on both branches (modified according to result of the condition). Enabled by -fprofile-use and -fauto-profile. -fversion-loops-for-strides If a loop iterates over an array with a variable stride, create another version of the loop that assumes the stride is always one. For example: for (int i = 0; i < n; ++i) x[i * stride] = ...; becomes: if (stride == 1) for (int i = 0; i < n; ++i) x[i] = ...; else for (int i = 0; i < n; ++i) x[i * stride] = ...; This is particularly useful for assumed-shape arrays in Fortran where (for example) it allows better vectorization assuming contiguous accesses. This flag is enabled by default at -O3. It is also enabled by -fprofile-use and -fauto-profile. -ffunction-sections -fdata-sections Place each function or data item into its own section in the output file if the target supports arbitrary sections. The name of the function or the name of the data item determines the section's name in the output file. Use these options on systems where the linker can perform optimizations to improve locality of reference in the instruction space. Most systems using the ELF object format have linkers with such optimizations. On AIX, the linker rearranges sections (CSECTs) based on the call graph. The performance impact varies. Together with a linker garbage collection (linker --gc-sections option) these options may lead to smaller statically-linked executables (after stripping). On ELF/DWARF systems these options do not degenerate the quality of the debug information. There could be issues with other object files/debug info formats. Only use these options when there are significant benefits from doing so. When you specify these options, the assembler and linker create larger object and executable files and are also slower. These options affect code generation. They prevent optimizations by the compiler and assembler using relative locations inside a translation unit since the locations are unknown until link time. An example of such an optimization is relaxing calls to short call instructions. -fstdarg-opt Optimize the prologue of variadic argument functions with respect to usage of those arguments. -fsection-anchors Try to reduce the number of symbolic address calculations by using shared "anchor" symbols to address nearby objects. This transformation can help to reduce the number of GOT entries and GOT accesses on some targets. For example, the implementation of the following function "foo": static int a, b, c; int foo (void) { return a + b + c; } usually calculates the addresses of all three variables, but if you compile it with -fsection-anchors, it accesses the variables from a common anchor point instead. The effect is similar to the following pseudocode (which isn't valid C): int foo (void) { register int *xr = &x; return xr[&a - &x] + xr[&b - &x] + xr[&c - &x]; } Not all targets support this option. -fzero-call-used-regs=choice Zero call-used registers at function return to increase program security by either mitigating Return-Oriented Programming (ROP) attacks or preventing information leakage through registers. The possible values of choice are the same as for the "zero_call_used_regs" attribute. The default is skip. You can control this behavior for a specific function by using the function attribute "zero_call_used_regs". --param name=value In some places, GCC uses various constants to control the amount of optimization that is done. For example, GCC does not inline functions that contain more than a certain number of instructions. You can control some of these constants on the command line using the --param option. The names of specific parameters, and the meaning of the values, are tied to the internals of the compiler, and are subject to change without notice in future releases. In order to get the minimal, maximal and default values of a parameter, use the --help=param -Q options. In each case, the value is an integer. The following choices of name are recognized for all targets: predictable-branch-outcome When branch is predicted to be taken with probability lower than this threshold (in percent), then it is considered well predictable. max-rtl-if-conversion-insns RTL if-conversion tries to remove conditional branches around a block and replace them with conditionally executed instructions. This parameter gives the maximum number of instructions in a block which should be considered for if- conversion. The compiler will also use other heuristics to decide whether if-conversion is likely to be profitable. max-rtl-if-conversion-predictable-cost RTL if-conversion will try to remove conditional branches around a block and replace them with conditionally executed instructions. These parameters give the maximum permissible cost for the sequence that would be generated by if-conversion depending on whether the branch is statically determined to be predictable or not. The units for this parameter are the same as those for the GCC internal seq_cost metric. The compiler will try to provide a reasonable default for this parameter using the BRANCH_COST target macro. max-crossjump-edges The maximum number of incoming edges to consider for cross- jumping. The algorithm used by -fcrossjumping is O(N^2) in the number of edges incoming to each block. Increasing values mean more aggressive optimization, making the compilation time increase with probably small improvement in executable size. min-crossjump-insns The minimum number of instructions that must be matched at the end of two blocks before cross-jumping is performed on them. This value is ignored in the case where all instructions in the block being cross-jumped from are matched. max-grow-copy-bb-insns The maximum code size expansion factor when copying basic blocks instead of jumping. The expansion is relative to a jump instruction. max-goto-duplication-insns The maximum number of instructions to duplicate to a block that jumps to a computed goto. To avoid O(N^2) behavior in a number of passes, GCC factors computed gotos early in the compilation process, and unfactors them as late as possible. Only computed jumps at the end of a basic blocks with no more than max-goto- duplication-insns are unfactored. max-delay-slot-insn-search The maximum number of instructions to consider when looking for an instruction to fill a delay slot. If more than this arbitrary number of instructions are searched, the time savings from filling the delay slot are minimal, so stop searching. Increasing values mean more aggressive optimization, making the compilation time increase with probably small improvement in execution time. max-delay-slot-live-search When trying to fill delay slots, the maximum number of instructions to consider when searching for a block with valid live register information. Increasing this arbitrarily chosen value means more aggressive optimization, increasing the compilation time. This parameter should be removed when the delay slot code is rewritten to maintain the control-flow graph. max-gcse-memory The approximate maximum amount of memory in "kB" that can be allocated in order to perform the global common subexpression elimination optimization. If more memory than specified is required, the optimization is not done. max-gcse-insertion-ratio If the ratio of expression insertions to deletions is larger than this value for any expression, then RTL PRE inserts or removes the expression and thus leaves partially redundant computations in the instruction stream. max-pending-list-length The maximum number of pending dependencies scheduling allows before flushing the current state and starting over. Large functions with few branches or calls can create excessively large lists which needlessly consume memory and resources. max-modulo-backtrack-attempts The maximum number of backtrack attempts the scheduler should make when modulo scheduling a loop. Larger values can exponentially increase compilation time. max-inline-functions-called-once-loop-depth Maximal loop depth of a call considered by inline heuristics that tries to inline all functions called once. max-inline-functions-called-once-insns Maximal estimated size of functions produced while inlining functions called once. max-inline-insns-single Several parameters control the tree inliner used in GCC. This number sets the maximum number of instructions (counted in GCC's internal representation) in a single function that the tree inliner considers for inlining. This only affects functions declared inline and methods implemented in a class declaration (C++). max-inline-insns-auto When you use -finline-functions (included in -O3), a lot of functions that would otherwise not be considered for inlining by the compiler are investigated. To those functions, a different (more restrictive) limit compared to functions declared inline can be applied (--param max-inline-insns-auto). max-inline-insns-small This is bound applied to calls which are considered relevant with -finline-small-functions. max-inline-insns-size This is bound applied to calls which are optimized for size. Small growth may be desirable to anticipate optimization oppurtunities exposed by inlining. uninlined-function-insns Number of instructions accounted by inliner for function overhead such as function prologue and epilogue. uninlined-function-time Extra time accounted by inliner for function overhead such as time needed to execute function prologue and epilogue. inline-heuristics-hint-percent The scale (in percents) applied to inline-insns-single, inline-insns-single-O2, inline-insns-auto when inline heuristics hints that inlining is very profitable (will enable later optimizations). uninlined-thunk-insns uninlined-thunk-time Same as --param uninlined-function-insns and --param uninlined- function-time but applied to function thunks. inline-min-speedup When estimated performance improvement of caller + callee runtime exceeds this threshold (in percent), the function can be inlined regardless of the limit on --param max-inline-insns- single and --param max-inline-insns-auto. large-function-insns The limit specifying really large functions. For functions larger than this limit after inlining, inlining is constrained by --param large-function-growth. This parameter is useful primarily to avoid extreme compilation time caused by non- linear algorithms used by the back end. large-function-growth Specifies maximal growth of large function caused by inlining in percents. For example, parameter value 100 limits large function growth to 2.0 times the original size. large-unit-insns The limit specifying large translation unit. Growth caused by inlining of units larger than this limit is limited by --param inline-unit-growth. For small units this might be too tight. For example, consider a unit consisting of function A that is inline and B that just calls A three times. If B is small relative to A, the growth of unit is 300\% and yet such inlining is very sane. For very large units consisting of small inlineable functions, however, the overall unit growth limit is needed to avoid exponential explosion of code size. Thus for smaller units, the size is increased to --param large- unit-insns before applying --param inline-unit-growth. lazy-modules Maximum number of concurrently open C++ module files when lazy loading. inline-unit-growth Specifies maximal overall growth of the compilation unit caused by inlining. For example, parameter value 20 limits unit growth to 1.2 times the original size. Cold functions (either marked cold via an attribute or by profile feedback) are not accounted into the unit size. ipa-cp-unit-growth Specifies maximal overall growth of the compilation unit caused by interprocedural constant propagation. For example, parameter value 10 limits unit growth to 1.1 times the original size. ipa-cp-large-unit-insns The size of translation unit that IPA-CP pass considers large. large-stack-frame The limit specifying large stack frames. While inlining the algorithm is trying to not grow past this limit too much. large-stack-frame-growth Specifies maximal growth of large stack frames caused by inlining in percents. For example, parameter value 1000 limits large stack frame growth to 11 times the original size. max-inline-insns-recursive max-inline-insns-recursive-auto Specifies the maximum number of instructions an out-of-line copy of a self-recursive inline function can grow into by performing recursive inlining. --param max-inline-insns-recursive applies to functions declared inline. For functions not declared inline, recursive inlining happens only when -finline-functions (included in -O3) is enabled; --param max-inline-insns-recursive-auto applies instead. max-inline-recursive-depth max-inline-recursive-depth-auto Specifies the maximum recursion depth used for recursive inlining. --param max-inline-recursive-depth applies to functions declared inline. For functions not declared inline, recursive inlining happens only when -finline-functions (included in -O3) is enabled; --param max-inline-recursive-depth-auto applies instead. min-inline-recursive-probability Recursive inlining is profitable only for function having deep recursion in average and can hurt for function having little recursion depth by increasing the prologue size or complexity of function body to other optimizers. When profile feedback is available (see -fprofile-generate) the actual recursion depth can be guessed from the probability that function recurses via a given call expression. This parameter limits inlining only to call expressions whose probability exceeds the given threshold (in percents). early-inlining-insns Specify growth that the early inliner can make. In effect it increases the amount of inlining for code having a large abstraction penalty. max-early-inliner-iterations Limit of iterations of the early inliner. This basically bounds the number of nested indirect calls the early inliner can resolve. Deeper chains are still handled by late inlining. comdat-sharing-probability Probability (in percent) that C++ inline function with comdat visibility are shared across multiple compilation units. modref-max-bases modref-max-refs modref-max-accesses Specifies the maximal number of base pointers, references and accesses stored for a single function by mod/ref analysis. modref-max-tests Specifies the maxmal number of tests alias oracle can perform to disambiguate memory locations using the mod/ref information. This parameter ought to be bigger than --param modref-max-bases and --param modref-max-refs. modref-max-depth Specifies the maximum depth of DFS walk used by modref escape analysis. Setting to 0 disables the analysis completely. modref-max-escape-points Specifies the maximum number of escape points tracked by modref per SSA-name. modref-max-adjustments Specifies the maximum number the access range is enlarged during modref dataflow analysis. profile-func-internal-id A parameter to control whether to use function internal id in profile database lookup. If the value is 0, the compiler uses an id that is based on function assembler name and filename, which makes old profile data more tolerant to source changes such as function reordering etc. min-vect-loop-bound The minimum number of iterations under which loops are not vectorized when -ftree-vectorize is used. The number of iterations after vectorization needs to be greater than the value specified by this option to allow vectorization. gcse-cost-distance-ratio Scaling factor in calculation of maximum distance an expression can be moved by GCSE optimizations. This is currently supported only in the code hoisting pass. The bigger the ratio, the more aggressive code hoisting is with simple expressions, i.e., the expressions that have cost less than gcse-unrestricted-cost. Specifying 0 disables hoisting of simple expressions. gcse-unrestricted-cost Cost, roughly measured as the cost of a single typical machine instruction, at which GCSE optimizations do not constrain the distance an expression can travel. This is currently supported only in the code hoisting pass. The lesser the cost, the more aggressive code hoisting is. Specifying 0 allows all expressions to travel unrestricted distances. max-hoist-depth The depth of search in the dominator tree for expressions to hoist. This is used to avoid quadratic behavior in hoisting algorithm. The value of 0 does not limit on the search, but may slow down compilation of huge functions. max-tail-merge-comparisons The maximum amount of similar bbs to compare a bb with. This is used to avoid quadratic behavior in tree tail merging. max-tail-merge-iterations The maximum amount of iterations of the pass over the function. This is used to limit compilation time in tree tail merging. store-merging-allow-unaligned Allow the store merging pass to introduce unaligned stores if it is legal to do so. max-stores-to-merge The maximum number of stores to attempt to merge into wider stores in the store merging pass. max-store-chains-to-track The maximum number of store chains to track at the same time in the attempt to merge them into wider stores in the store merging pass. max-stores-to-track The maximum number of stores to track at the same time in the attemt to to merge them into wider stores in the store merging pass. max-unrolled-insns The maximum number of instructions that a loop may have to be unrolled. If a loop is unrolled, this parameter also determines how many times the loop code is unrolled. max-average-unrolled-insns The maximum number of instructions biased by probabilities of their execution that a loop may have to be unrolled. If a loop is unrolled, this parameter also determines how many times the loop code is unrolled. max-unroll-times The maximum number of unrollings of a single loop. max-peeled-insns The maximum number of instructions that a loop may have to be peeled. If a loop is peeled, this parameter also determines how many times the loop code is peeled. max-peel-times The maximum number of peelings of a single loop. max-peel-branches The maximum number of branches on the hot path through the peeled sequence. max-completely-peeled-insns The maximum number of insns of a completely peeled loop. max-completely-peel-times The maximum number of iterations of a loop to be suitable for complete peeling. max-completely-peel-loop-nest-depth The maximum depth of a loop nest suitable for complete peeling. max-unswitch-insns The maximum number of insns of an unswitched loop. max-unswitch-depth The maximum depth of a loop nest to be unswitched. lim-expensive The minimum cost of an expensive expression in the loop invariant motion. min-loop-cond-split-prob When FDO profile information is available, min-loop-cond-split- prob specifies minimum threshold for probability of semi- invariant condition statement to trigger loop split. iv-consider-all-candidates-bound Bound on number of candidates for induction variables, below which all candidates are considered for each use in induction variable optimizations. If there are more candidates than this, only the most relevant ones are considered to avoid quadratic time complexity. iv-max-considered-uses The induction variable optimizations give up on loops that contain more induction variable uses. iv-always-prune-cand-set-bound If the number of candidates in the set is smaller than this value, always try to remove unnecessary ivs from the set when adding a new one. avg-loop-niter Average number of iterations of a loop. dse-max-object-size Maximum size (in bytes) of objects tracked bytewise by dead store elimination. Larger values may result in larger compilation times. dse-max-alias-queries-per-store Maximum number of queries into the alias oracle per store. Larger values result in larger compilation times and may result in more removed dead stores. scev-max-expr-size Bound on size of expressions used in the scalar evolutions analyzer. Large expressions slow the analyzer. scev-max-expr-complexity Bound on the complexity of the expressions in the scalar evolutions analyzer. Complex expressions slow the analyzer. max-tree-if-conversion-phi-args Maximum number of arguments in a PHI supported by TREE if conversion unless the loop is marked with simd pragma. vect-max-layout-candidates The maximum number of possible vector layouts (such as permutations) to consider when optimizing to-be-vectorized code. vect-max-version-for-alignment-checks The maximum number of run-time checks that can be performed when doing loop versioning for alignment in the vectorizer. vect-max-version-for-alias-checks The maximum number of run-time checks that can be performed when doing loop versioning for alias in the vectorizer. vect-max-peeling-for-alignment The maximum number of loop peels to enhance access alignment for vectorizer. Value -1 means no limit. max-iterations-to-track The maximum number of iterations of a loop the brute-force algorithm for analysis of the number of iterations of the loop tries to evaluate. hot-bb-count-fraction The denominator n of fraction 1/n of the maximal execution count of a basic block in the entire program that a basic block needs to at least have in order to be considered hot. The default is 10000, which means that a basic block is considered hot if its execution count is greater than 1/10000 of the maximal execution count. 0 means that it is never considered hot. Used in non-LTO mode. hot-bb-count-ws-permille The number of most executed permilles, ranging from 0 to 1000, of the profiled execution of the entire program to which the execution count of a basic block must be part of in order to be considered hot. The default is 990, which means that a basic block is considered hot if its execution count contributes to the upper 990 permilles, or 99.0%, of the profiled execution of the entire program. 0 means that it is never considered hot. Used in LTO mode. hot-bb-frequency-fraction The denominator n of fraction 1/n of the execution frequency of the entry block of a function that a basic block of this function needs to at least have in order to be considered hot. The default is 1000, which means that a basic block is considered hot in a function if it is executed more frequently than 1/1000 of the frequency of the entry block of the function. 0 means that it is never considered hot. unlikely-bb-count-fraction The denominator n of fraction 1/n of the number of profiled runs of the entire program below which the execution count of a basic block must be in order for the basic block to be considered unlikely executed. The default is 20, which means that a basic block is considered unlikely executed if it is executed in fewer than 1/20, or 5%, of the runs of the program. 0 means that it is always considered unlikely executed. max-predicted-iterations The maximum number of loop iterations we predict statically. This is useful in cases where a function contains a single loop with known bound and another loop with unknown bound. The known number of iterations is predicted correctly, while the unknown number of iterations average to roughly 10. This means that the loop without bounds appears artificially cold relative to the other one. builtin-expect-probability Control the probability of the expression having the specified value. This parameter takes a percentage (i.e. 0 ... 100) as input. builtin-string-cmp-inline-length The maximum length of a constant string for a builtin string cmp call eligible for inlining. align-threshold Select fraction of the maximal frequency of executions of a basic block in a function to align the basic block. align-loop-iterations A loop expected to iterate at least the selected number of iterations is aligned. tracer-dynamic-coverage tracer-dynamic-coverage-feedback This value is used to limit superblock formation once the given percentage of executed instructions is covered. This limits unnecessary code size expansion. The tracer-dynamic-coverage-feedback parameter is used only when profile feedback is available. The real profiles (as opposed to statically estimated ones) are much less balanced allowing the threshold to be larger value. tracer-max-code-growth Stop tail duplication once code growth has reached given percentage. This is a rather artificial limit, as most of the duplicates are eliminated later in cross jumping, so it may be set to much higher values than is the desired code growth. tracer-min-branch-ratio Stop reverse growth when the reverse probability of best edge is less than this threshold (in percent). tracer-min-branch-probability tracer-min-branch-probability-feedback Stop forward growth if the best edge has probability lower than this threshold. Similarly to tracer-dynamic-coverage two parameters are provided. tracer-min-branch-probability-feedback is used for compilation with profile feedback and tracer-min-branch- probability compilation without. The value for compilation with profile feedback needs to be more conservative (higher) in order to make tracer effective. stack-clash-protection-guard-size Specify the size of the operating system provided stack guard as 2 raised to num bytes. Higher values may reduce the number of explicit probes, but a value larger than the operating system provided guard will leave code vulnerable to stack clash style attacks. stack-clash-protection-probe-interval Stack clash protection involves probing stack space as it is allocated. This param controls the maximum distance between probes into the stack as 2 raised to num bytes. Higher values may reduce the number of explicit probes, but a value larger than the operating system provided guard will leave code vulnerable to stack clash style attacks. max-cse-path-length The maximum number of basic blocks on path that CSE considers. max-cse-insns The maximum number of instructions CSE processes before flushing. ggc-min-expand GCC uses a garbage collector to manage its own memory allocation. This parameter specifies the minimum percentage by which the garbage collector's heap should be allowed to expand between collections. Tuning this may improve compilation speed; it has no effect on code generation. The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when RAM >= 1GB. If "getrlimit" is available, the notion of "RAM" is the smallest of actual RAM and "RLIMIT_DATA" or "RLIMIT_AS". If GCC is not able to calculate RAM on a particular platform, the lower bound of 30% is used. Setting this parameter and ggc-min-heapsize to zero causes a full collection to occur at every opportunity. This is extremely slow, but can be useful for debugging. ggc-min-heapsize Minimum size of the garbage collector's heap before it begins bothering to collect garbage. The first collection occurs after the heap expands by ggc-min-expand% beyond ggc-min- heapsize. Again, tuning this may improve compilation speed, and has no effect on code generation. The default is the smaller of RAM/8, RLIMIT_RSS, or a limit that tries to ensure that RLIMIT_DATA or RLIMIT_AS are not exceeded, but with a lower bound of 4096 (four megabytes) and an upper bound of 131072 (128 megabytes). If GCC is not able to calculate RAM on a particular platform, the lower bound is used. Setting this parameter very large effectively disables garbage collection. Setting this parameter and ggc-min-expand to zero causes a full collection to occur at every opportunity. max-reload-search-insns The maximum number of instruction reload should look backward for equivalent register. Increasing values mean more aggressive optimization, making the compilation time increase with probably slightly better performance. max-cselib-memory-locations The maximum number of memory locations cselib should take into account. Increasing values mean more aggressive optimization, making the compilation time increase with probably slightly better performance. max-sched-ready-insns The maximum number of instructions ready to be issued the scheduler should consider at any given time during the first scheduling pass. Increasing values mean more thorough searches, making the compilation time increase with probably little benefit. max-sched-region-blocks The maximum number of blocks in a region to be considered for interblock scheduling. max-pipeline-region-blocks The maximum number of blocks in a region to be considered for pipelining in the selective scheduler. max-sched-region-insns The maximum number of insns in a region to be considered for interblock scheduling. max-pipeline-region-insns The maximum number of insns in a region to be considered for pipelining in the selective scheduler. min-spec-prob The minimum probability (in percents) of reaching a source block for interblock speculative scheduling. max-sched-extend-regions-iters The maximum number of iterations through CFG to extend regions. A value of 0 disables region extensions. max-sched-insn-conflict-delay The maximum conflict delay for an insn to be considered for speculative motion. sched-spec-prob-cutoff The minimal probability of speculation success (in percents), so that speculative insns are scheduled. sched-state-edge-prob-cutoff The minimum probability an edge must have for the scheduler to save its state across it. sched-mem-true-dep-cost Minimal distance (in CPU cycles) between store and load targeting same memory locations. selsched-max-lookahead The maximum size of the lookahead window of selective scheduling. It is a depth of search for available instructions. selsched-max-sched-times The maximum number of times that an instruction is scheduled during selective scheduling. This is the limit on the number of iterations through which the instruction may be pipelined. selsched-insns-to-rename The maximum number of best instructions in the ready list that are considered for renaming in the selective scheduler. sms-min-sc The minimum value of stage count that swing modulo scheduler generates. max-last-value-rtl The maximum size measured as number of RTLs that can be recorded in an expression in combiner for a pseudo register as last known value of that register. max-combine-insns The maximum number of instructions the RTL combiner tries to combine. integer-share-limit Small integer constants can use a shared data structure, reducing the compiler's memory usage and increasing its speed. This sets the maximum value of a shared integer constant. ssp-buffer-size The minimum size of buffers (i.e. arrays) that receive stack smashing protection when -fstack-protector is used. min-size-for-stack-sharing The minimum size of variables taking part in stack slot sharing when not optimizing. max-jump-thread-duplication-stmts Maximum number of statements allowed in a block that needs to be duplicated when threading jumps. max-jump-thread-paths The maximum number of paths to consider when searching for jump threading opportunities. When arriving at a block, incoming edges are only considered if the number of paths to be searched so far multiplied by the number of incoming edges does not exhaust the specified maximum number of paths to consider. max-fields-for-field-sensitive Maximum number of fields in a structure treated in a field sensitive manner during pointer analysis. prefetch-latency Estimate on average number of instructions that are executed before prefetch finishes. The distance prefetched ahead is proportional to this constant. Increasing this number may also lead to less streams being prefetched (see simultaneous- prefetches). simultaneous-prefetches Maximum number of prefetches that can run at the same time. l1-cache-line-size The size of cache line in L1 data cache, in bytes. l1-cache-size The size of L1 data cache, in kilobytes. l2-cache-size The size of L2 data cache, in kilobytes. prefetch-dynamic-strides Whether the loop array prefetch pass should issue software prefetch hints for strides that are non-constant. In some cases this may be beneficial, though the fact the stride is non-constant may make it hard to predict when there is clear benefit to issuing these hints. Set to 1 if the prefetch hints should be issued for non- constant strides. Set to 0 if prefetch hints should be issued only for strides that are known to be constant and below prefetch-minimum-stride. prefetch-minimum-stride Minimum constant stride, in bytes, to start using prefetch hints for. If the stride is less than this threshold, prefetch hints will not be issued. This setting is useful for processors that have hardware prefetchers, in which case there may be conflicts between the hardware prefetchers and the software prefetchers. If the hardware prefetchers have a maximum stride they can handle, it should be used here to improve the use of software prefetchers. A value of -1 means we don't have a threshold and therefore prefetch hints can be issued for any constant stride. This setting is only useful for strides that are known and constant. destructive-interference-size constructive-interference-size The values for the C++17 variables "std::hardware_destructive_interference_size" and "std::hardware_constructive_interference_size". The destructive interference size is the minimum recommended offset between two independent concurrently-accessed objects; the constructive interference size is the maximum recommended size of contiguous memory accessed together. Typically both will be the size of an L1 cache line for the target, in bytes. For a generic target covering a range of L1 cache line sizes, typically the constructive interference size will be the small end of the range and the destructive size will be the large end. The destructive interference size is intended to be used for layout, and thus has ABI impact. The default value is not expected to be stable, and on some targets varies with -mtune, so use of this variable in a context where ABI stability is important, such as the public interface of a library, is strongly discouraged; if it is used in that context, users can stabilize the value using this option. The constructive interference size is less sensitive, as it is typically only used in a static_assert to make sure that a type fits within a cache line. See also -Winterference-size. loop-interchange-max-num-stmts The maximum number of stmts in a loop to be interchanged. loop-interchange-stride-ratio The minimum ratio between stride of two loops for interchange to be profitable. min-insn-to-prefetch-ratio The minimum ratio between the number of instructions and the number of prefetches to enable prefetching in a loop. prefetch-min-insn-to-mem-ratio The minimum ratio between the number of instructions and the number of memory references to enable prefetching in a loop. use-canonical-types Whether the compiler should use the "canonical" type system. Should always be 1, which uses a more efficient internal mechanism for comparing types in C++ and Objective-C++. However, if bugs in the canonical type system are causing compilation failures, set this value to 0 to disable canonical types. switch-conversion-max-branch-ratio Switch initialization conversion refuses to create arrays that are bigger than switch-conversion-max-branch-ratio times the number of branches in the switch. max-partial-antic-length Maximum length of the partial antic set computed during the tree partial redundancy elimination optimization (-ftree-pre) when optimizing at -O3 and above. For some sorts of source code the enhanced partial redundancy elimination optimization can run away, consuming all of the memory available on the host machine. This parameter sets a limit on the length of the sets that are computed, which prevents the runaway behavior. Setting a value of 0 for this parameter allows an unlimited set length. rpo-vn-max-loop-depth Maximum loop depth that is value-numbered optimistically. When the limit hits the innermost rpo-vn-max-loop-depth loops and the outermost loop in the loop nest are value-numbered optimistically and the remaining ones not. sccvn-max-alias-queries-per-access Maximum number of alias-oracle queries we perform when looking for redundancies for loads and stores. If this limit is hit the search is aborted and the load or store is not considered redundant. The number of queries is algorithmically limited to the number of stores on all paths from the load to the function entry. ira-max-loops-num IRA uses regional register allocation by default. If a function contains more loops than the number given by this parameter, only at most the given number of the most frequently-executed loops form regions for regional register allocation. ira-max-conflict-table-size Although IRA uses a sophisticated algorithm to compress the conflict table, the table can still require excessive amounts of memory for huge functions. If the conflict table for a function could be more than the size in MB given by this parameter, the register allocator instead uses a faster, simpler, and lower-quality algorithm that does not require building a pseudo-register conflict table. ira-loop-reserved-regs IRA can be used to evaluate more accurate register pressure in loops for decisions to move loop invariants (see -O3). The number of available registers reserved for some other purposes is given by this parameter. Default of the parameter is the best found from numerous experiments. ira-consider-dup-in-all-alts Make IRA to consider matching constraint (duplicated operand number) heavily in all available alternatives for preferred register class. If it is set as zero, it means IRA only respects the matching constraint when it's in the only available alternative with an appropriate register class. Otherwise, it means IRA will check all available alternatives for preferred register class even if it has found some choice with an appropriate register class and respect the found qualified matching constraint. ira-simple-lra-insn-threshold Approximate function insn number in 1K units triggering simple local RA. lra-inheritance-ebb-probability-cutoff LRA tries to reuse values reloaded in registers in subsequent insns. This optimization is called inheritance. EBB is used as a region to do this optimization. The parameter defines a minimal fall-through edge probability in percentage used to add BB to inheritance EBB in LRA. The default value was chosen from numerous runs of SPEC2000 on x86-64. loop-invariant-max-bbs-in-loop Loop invariant motion can be very expensive, both in compilation time and in amount of needed compile-time memory, with very large loops. Loops with more basic blocks than this parameter won't have loop invariant motion optimization performed on them. loop-max-datarefs-for-datadeps Building data dependencies is expensive for very large loops. This parameter limits the number of data references in loops that are considered for data dependence analysis. These large loops are no handled by the optimizations using loop data dependencies. max-vartrack-size Sets a maximum number of hash table slots to use during variable tracking dataflow analysis of any function. If this limit is exceeded with variable tracking at assignments enabled, analysis for that function is retried without it, after removing all debug insns from the function. If the limit is exceeded even without debug insns, var tracking analysis is completely disabled for the function. Setting the parameter to zero makes it unlimited. max-vartrack-expr-depth Sets a maximum number of recursion levels when attempting to map variable names or debug temporaries to value expressions. This trades compilation time for more complete debug information. If this is set too low, value expressions that are available and could be represented in debug information may end up not being used; setting this higher may enable the compiler to find more complex debug expressions, but compile time and memory use may grow. max-debug-marker-count Sets a threshold on the number of debug markers (e.g. begin stmt markers) to avoid complexity explosion at inlining or expanding to RTL. If a function has more such gimple stmts than the set limit, such stmts will be dropped from the inlined copy of a function, and from its RTL expansion. min-nondebug-insn-uid Use uids starting at this parameter for nondebug insns. The range below the parameter is reserved exclusively for debug insns created by -fvar-tracking-assignments, but debug insns may get (non-overlapping) uids above it if the reserved range is exhausted. ipa-sra-deref-prob-threshold IPA-SRA replaces a pointer which is known not be NULL with one or more new parameters only when the probability (in percent, relative to function entry) of it being dereferenced is higher than this parameter. ipa-sra-ptr-growth-factor IPA-SRA replaces a pointer to an aggregate with one or more new parameters only when their cumulative size is less or equal to ipa-sra-ptr-growth-factor times the size of the original pointer parameter. ipa-sra-ptrwrap-growth-factor Additional maximum allowed growth of total size of new parameters that ipa-sra replaces a pointer to an aggregate with, if it points to a local variable that the caller only writes to and passes it as an argument to other functions. ipa-sra-max-replacements Maximum pieces of an aggregate that IPA-SRA tracks. As a consequence, it is also the maximum number of replacements of a formal parameter. sra-max-scalarization-size-Ospeed sra-max-scalarization-size-Osize The two Scalar Reduction of Aggregates passes (SRA and IPA-SRA) aim to replace scalar parts of aggregates with uses of independent scalar variables. These parameters control the maximum size, in storage units, of aggregate which is considered for replacement when compiling for speed (sra-max- scalarization-size-Ospeed) or size (sra-max-scalarization-size- Osize) respectively. sra-max-propagations The maximum number of artificial accesses that Scalar Replacement of Aggregates (SRA) will track, per one local variable, in order to facilitate copy propagation. tm-max-aggregate-size When making copies of thread-local variables in a transaction, this parameter specifies the size in bytes after which variables are saved with the logging functions as opposed to save/restore code sequence pairs. This option only applies when using -fgnu-tm. graphite-max-nb-scop-params To avoid exponential effects in the Graphite loop transforms, the number of parameters in a Static Control Part (SCoP) is bounded. A value of zero can be used to lift the bound. A variable whose value is unknown at compilation time and defined outside a SCoP is a parameter of the SCoP. loop-block-tile-size Loop blocking or strip mining transforms, enabled with -floop-block or -floop-strip-mine, strip mine each loop in the loop nest by a given number of iterations. The strip length can be changed using the loop-block-tile-size parameter. ipa-jump-function-lookups Specifies number of statements visited during jump function offset discovery. ipa-cp-value-list-size IPA-CP attempts to track all possible values and types passed to a function's parameter in order to propagate them and perform devirtualization. ipa-cp-value-list-size is the maximum number of values and types it stores per one formal parameter of a function. ipa-cp-eval-threshold IPA-CP calculates its own score of cloning profitability heuristics and performs those cloning opportunities with scores that exceed ipa-cp-eval-threshold. ipa-cp-max-recursive-depth Maximum depth of recursive cloning for self-recursive function. ipa-cp-min-recursive-probability Recursive cloning only when the probability of call being executed exceeds the parameter. ipa-cp-profile-count-base When using -fprofile-use option, IPA-CP will consider the measured execution count of a call graph edge at this percentage position in their histogram as the basis for its heuristics calculation. ipa-cp-recursive-freq-factor The number of times interprocedural copy propagation expects recursive functions to call themselves. ipa-cp-recursion-penalty Percentage penalty the recursive functions will receive when they are evaluated for cloning. ipa-cp-single-call-penalty Percentage penalty functions containing a single call to another function will receive when they are evaluated for cloning. ipa-max-agg-items IPA-CP is also capable to propagate a number of scalar values passed in an aggregate. ipa-max-agg-items controls the maximum number of such values per one parameter. ipa-cp-loop-hint-bonus When IPA-CP determines that a cloning candidate would make the number of iterations of a loop known, it adds a bonus of ipa- cp-loop-hint-bonus to the profitability score of the candidate. ipa-max-loop-predicates The maximum number of different predicates IPA will use to describe when loops in a function have known properties. ipa-max-aa-steps During its analysis of function bodies, IPA-CP employs alias analysis in order to track values pointed to by function parameters. In order not spend too much time analyzing huge functions, it gives up and consider all memory clobbered after examining ipa-max-aa-steps statements modifying memory. ipa-max-switch-predicate-bounds Maximal number of boundary endpoints of case ranges of switch statement. For switch exceeding this limit, IPA-CP will not construct cloning cost predicate, which is used to estimate cloning benefit, for default case of the switch statement. ipa-max-param-expr-ops IPA-CP will analyze conditional statement that references some function parameter to estimate benefit for cloning upon certain constant value. But if number of operations in a parameter expression exceeds ipa-max-param-expr-ops, the expression is treated as complicated one, and is not handled by IPA analysis. lto-partitions Specify desired number of partitions produced during WHOPR compilation. The number of partitions should exceed the number of CPUs used for compilation. lto-min-partition Size of minimal partition for WHOPR (in estimated instructions). This prevents expenses of splitting very small programs into too many partitions. lto-max-partition Size of max partition for WHOPR (in estimated instructions). to provide an upper bound for individual size of partition. Meant to be used only with balanced partitioning. lto-max-streaming-parallelism Maximal number of parallel processes used for LTO streaming. cxx-max-namespaces-for-diagnostic-help The maximum number of namespaces to consult for suggestions when C++ name lookup fails for an identifier. sink-frequency-threshold The maximum relative execution frequency (in percents) of the target block relative to a statement's original block to allow statement sinking of a statement. Larger numbers result in more aggressive statement sinking. A small positive adjustment is applied for statements with memory operands as those are even more profitable so sink. max-stores-to-sink The maximum number of conditional store pairs that can be sunk. Set to 0 if either vectorization (-ftree-vectorize) or if- conversion (-ftree-loop-if-convert) is disabled. case-values-threshold The smallest number of different values for which it is best to use a jump-table instead of a tree of conditional branches. If the value is 0, use the default for the machine. jump-table-max-growth-ratio-for-size The maximum code size growth ratio when expanding into a jump table (in percent). The parameter is used when optimizing for size. jump-table-max-growth-ratio-for-speed The maximum code size growth ratio when expanding into a jump table (in percent). The parameter is used when optimizing for speed. tree-reassoc-width Set the maximum number of instructions executed in parallel in reassociated tree. This parameter overrides target dependent heuristics used by default if has non zero value. sched-pressure-algorithm Choose between the two available implementations of -fsched-pressure. Algorithm 1 is the original implementation and is the more likely to prevent instructions from being reordered. Algorithm 2 was designed to be a compromise between the relatively conservative approach taken by algorithm 1 and the rather aggressive approach taken by the default scheduler. It relies more heavily on having a regular register file and accurate register pressure classes. See haifa-sched.cc in the GCC sources for more details. The default choice depends on the target. max-slsr-cand-scan Set the maximum number of existing candidates that are considered when seeking a basis for a new straight-line strength reduction candidate. asan-globals Enable buffer overflow detection for global objects. This kind of protection is enabled by default if you are using -fsanitize=address option. To disable global objects protection use --param asan-globals=0. asan-stack Enable buffer overflow detection for stack objects. This kind of protection is enabled by default when using -fsanitize=address. To disable stack protection use --param asan-stack=0 option. asan-instrument-reads Enable buffer overflow detection for memory reads. This kind of protection is enabled by default when using -fsanitize=address. To disable memory reads protection use --param asan-instrument-reads=0. asan-instrument-writes Enable buffer overflow detection for memory writes. This kind of protection is enabled by default when using -fsanitize=address. To disable memory writes protection use --param asan-instrument-writes=0 option. asan-memintrin Enable detection for built-in functions. This kind of protection is enabled by default when using -fsanitize=address. To disable built-in functions protection use --param asan-memintrin=0. asan-use-after-return Enable detection of use-after-return. This kind of protection is enabled by default when using the -fsanitize=address option. To disable it use --param asan-use-after-return=0. Note: By default the check is disabled at run time. To enable it, add "detect_stack_use_after_return=1" to the environment variable ASAN_OPTIONS. asan-instrumentation-with-call-threshold If number of memory accesses in function being instrumented is greater or equal to this number, use callbacks instead of inline checks. E.g. to disable inline code use --param asan-instrumentation-with-call-threshold=0. asan-kernel-mem-intrinsic-prefix If nonzero, prefix calls to "memcpy", "memset" and "memmove" with __asan_ or __hwasan_ for -fsanitize=kernel-address or -fsanitize=kernel-hwaddress, respectively. hwasan-instrument-stack Enable hwasan instrumentation of statically sized stack- allocated variables. This kind of instrumentation is enabled by default when using -fsanitize=hwaddress and disabled by default when using -fsanitize=kernel-hwaddress. To disable stack instrumentation use --param hwasan-instrument-stack=0, and to enable it use --param hwasan-instrument-stack=1. hwasan-random-frame-tag When using stack instrumentation, decide tags for stack variables using a deterministic sequence beginning at a random tag for each frame. With this parameter unset tags are chosen using the same sequence but beginning from 1. This is enabled by default for -fsanitize=hwaddress and unavailable for -fsanitize=kernel-hwaddress. To disable it use --param hwasan-random-frame-tag=0. hwasan-instrument-allocas Enable hwasan instrumentation of dynamically sized stack- allocated variables. This kind of instrumentation is enabled by default when using -fsanitize=hwaddress and disabled by default when using -fsanitize=kernel-hwaddress. To disable instrumentation of such variables use --param hwasan-instrument-allocas=0, and to enable it use --param hwasan-instrument-allocas=1. hwasan-instrument-reads Enable hwasan checks on memory reads. Instrumentation of reads is enabled by default for both -fsanitize=hwaddress and -fsanitize=kernel-hwaddress. To disable checking memory reads use --param hwasan-instrument-reads=0. hwasan-instrument-writes Enable hwasan checks on memory writes. Instrumentation of writes is enabled by default for both -fsanitize=hwaddress and -fsanitize=kernel-hwaddress. To disable checking memory writes use --param hwasan-instrument-writes=0. hwasan-instrument-mem-intrinsics Enable hwasan instrumentation of builtin functions. Instrumentation of these builtin functions is enabled by default for both -fsanitize=hwaddress and -fsanitize=kernel-hwaddress. To disable instrumentation of builtin functions use --param hwasan-instrument-mem-intrinsics=0. use-after-scope-direct-emission-threshold If the size of a local variable in bytes is smaller or equal to this number, directly poison (or unpoison) shadow memory instead of using run-time callbacks. tsan-distinguish-volatile Emit special instrumentation for accesses to volatiles. tsan-instrument-func-entry-exit Emit instrumentation calls to __tsan_func_entry() and __tsan_func_exit(). max-fsm-thread-path-insns Maximum number of instructions to copy when duplicating blocks on a finite state automaton jump thread path. threader-debug threader-debug=[none|all] Enables verbose dumping of the threader solver. parloops-chunk-size Chunk size of omp schedule for loops parallelized by parloops. parloops-schedule Schedule type of omp schedule for loops parallelized by parloops (static, dynamic, guided, auto, runtime). parloops-min-per-thread The minimum number of iterations per thread of an innermost parallelized loop for which the parallelized variant is preferred over the single threaded one. Note that for a parallelized loop nest the minimum number of iterations of the outermost loop per thread is two. max-ssa-name-query-depth Maximum depth of recursion when querying properties of SSA names in things like fold routines. One level of recursion corresponds to following a use-def chain. max-speculative-devirt-maydefs The maximum number of may-defs we analyze when looking for a must-def specifying the dynamic type of an object that invokes a virtual call we may be able to devirtualize speculatively. evrp-sparse-threshold Maximum number of basic blocks before EVRP uses a sparse cache. ranger-debug Specifies the type of debug output to be issued for ranges. evrp-switch-limit Specifies the maximum number of switch cases before EVRP ignores a switch. unroll-jam-min-percent The minimum percentage of memory references that must be optimized away for the unroll-and-jam transformation to be considered profitable. unroll-jam-max-unroll The maximum number of times the outer loop should be unrolled by the unroll-and-jam transformation. max-rtl-if-conversion-unpredictable-cost Maximum permissible cost for the sequence that would be generated by the RTL if-conversion pass for a branch that is considered unpredictable. max-variable-expansions-in-unroller If -fvariable-expansion-in-unroller is used, the maximum number of times that an individual variable will be expanded during loop unrolling. partial-inlining-entry-probability Maximum probability of the entry BB of split region (in percent relative to entry BB of the function) to make partial inlining happen. max-tracked-strlens Maximum number of strings for which strlen optimization pass will track string lengths. gcse-after-reload-partial-fraction The threshold ratio for performing partial redundancy elimination after reload. gcse-after-reload-critical-fraction The threshold ratio of critical edges execution count that permit performing redundancy elimination after reload. max-loop-header-insns The maximum number of insns in loop header duplicated by the copy loop headers pass. vect-epilogues-nomask Enable loop epilogue vectorization using smaller vector size. vect-partial-vector-usage Controls when the loop vectorizer considers using partial vector loads and stores as an alternative to falling back to scalar code. 0 stops the vectorizer from ever using partial vector loads and stores. 1 allows partial vector loads and stores if vectorization removes the need for the code to iterate. 2 allows partial vector loads and stores in all loops. The parameter only has an effect on targets that support partial vector loads and stores. vect-inner-loop-cost-factor The maximum factor which the loop vectorizer applies to the cost of statements in an inner loop relative to the loop being vectorized. The factor applied is the maximum of the estimated number of iterations of the inner loop and this parameter. The default value of this parameter is 50. vect-induction-float Enable loop vectorization of floating point inductions. avoid-fma-max-bits Maximum number of bits for which we avoid creating FMAs. sms-loop-average-count-threshold A threshold on the average loop count considered by the swing modulo scheduler. sms-dfa-history The number of cycles the swing modulo scheduler considers when checking conflicts using DFA. graphite-allow-codegen-errors Whether codegen errors should be ICEs when -fchecking. sms-max-ii-factor A factor for tuning the upper bound that swing modulo scheduler uses for scheduling a loop. lra-max-considered-reload-pseudos The max number of reload pseudos which are considered during spilling a non-reload pseudo. max-pow-sqrt-depth Maximum depth of sqrt chains to use when synthesizing exponentiation by a real constant. max-dse-active-local-stores Maximum number of active local stores in RTL dead store elimination. asan-instrument-allocas Enable asan allocas/VLAs protection. max-iterations-computation-cost Bound on the cost of an expression to compute the number of iterations. max-isl-operations Maximum number of isl operations, 0 means unlimited. graphite-max-arrays-per-scop Maximum number of arrays per scop. max-vartrack-reverse-op-size Max. size of loc list for which reverse ops should be added. fsm-scale-path-stmts Scale factor to apply to the number of statements in a threading path crossing a loop backedge when comparing to --param=max-jump-thread-duplication-stmts. uninit-control-dep-attempts Maximum number of nested calls to search for control dependencies during uninitialized variable analysis. sched-autopref-queue-depth Hardware autoprefetcher scheduler model control flag. Number of lookahead cycles the model looks into; at ' ' only enable instruction sorting heuristic. loop-versioning-max-inner-insns The maximum number of instructions that an inner loop can have before the loop versioning pass considers it too big to copy. loop-versioning-max-outer-insns The maximum number of instructions that an outer loop can have before the loop versioning pass considers it too big to copy, discounting any instructions in inner loops that directly benefit from versioning. ssa-name-def-chain-limit The maximum number of SSA_NAME assignments to follow in determining a property of a variable such as its value. This limits the number of iterations or recursive calls GCC performs when optimizing certain statements or when determining their validity prior to issuing diagnostics. store-merging-max-size Maximum size of a single store merging region in bytes. hash-table-verification-limit The number of elements for which hash table verification is done for each searched element. max-find-base-term-values Maximum number of VALUEs handled during a single find_base_term call. analyzer-max-enodes-per-program-point The maximum number of exploded nodes per program point within the analyzer, before terminating analysis of that point. analyzer-max-constraints The maximum number of constraints per state. analyzer-min-snodes-for-call-summary The minimum number of supernodes within a function for the analyzer to consider summarizing its effects at call sites. analyzer-max-enodes-for-full-dump The maximum depth of exploded nodes that should appear in a dot dump before switching to a less verbose format. analyzer-max-recursion-depth The maximum number of times a callsite can appear in a call stack within the analyzer, before terminating analysis of a call that would recurse deeper. analyzer-max-svalue-depth The maximum depth of a symbolic value, before approximating the value as unknown. analyzer-max-infeasible-edges The maximum number of infeasible edges to reject before declaring a diagnostic as infeasible. gimple-fe-computed-hot-bb-threshold The number of executions of a basic block which is considered hot. The parameter is used only in GIMPLE FE. analyzer-bb-explosion-factor The maximum number of 'after supernode' exploded nodes within the analyzer per supernode, before terminating analysis. ranger-logical-depth Maximum depth of logical expression evaluation ranger will look through when evaluating outgoing edge ranges. ranger-recompute-depth Maximum depth of instruction chains to consider for recomputation in the outgoing range calculator. relation-block-limit Maximum number of relations the oracle will register in a basic block. min-pagesize Minimum page size for warning purposes. openacc-kernels Specify mode of OpenACC `kernels' constructs handling. With --param=openacc-kernels=decompose, OpenACC `kernels' constructs are decomposed into parts, a sequence of compute constructs, each then handled individually. This is work in progress. With --param=openacc-kernels=parloops, OpenACC `kernels' constructs are handled by the parloops pass, en bloc. This is the current default. openacc-privatization Control whether the -fopt-info-omp-note and applicable -fdump-tree-*-details options emit OpenACC privatization diagnostics. With --param=openacc-privatization=quiet, don't diagnose. This is the current default. With --param=openacc-privatization=noisy, do diagnose. The following choices of name are available on AArch64 targets: aarch64-sve-compare-costs When vectorizing for SVE, consider using "unpacked" vectors for smaller elements and use the cost model to pick the cheapest approach. Also use the cost model to choose between SVE and Advanced SIMD vectorization. Using unpacked vectors includes storing smaller elements in larger containers and accessing elements with extending loads and truncating stores. aarch64-float-recp-precision The number of Newton iterations for calculating the reciprocal for float type. The precision of division is proportional to this param when division approximation is enabled. The default value is 1. aarch64-double-recp-precision The number of Newton iterations for calculating the reciprocal for double type. The precision of division is propotional to this param when division approximation is enabled. The default value is 2. aarch64-autovec-preference Force an ISA selection strategy for auto-vectorization. Accepts values from 0 to 4, inclusive. 0 Use the default heuristics. 1 Use only Advanced SIMD for auto-vectorization. 2 Use only SVE for auto-vectorization. 3 Use both Advanced SIMD and SVE. Prefer Advanced SIMD when the costs are deemed equal. 4 Use both Advanced SIMD and SVE. Prefer SVE when the costs are deemed equal. The default value is 0. aarch64-loop-vect-issue-rate-niters The tuning for some AArch64 CPUs tries to take both latencies and issue rates into account when deciding whether a loop should be vectorized using SVE, vectorized using Advanced SIMD, or not vectorized at all. If this parameter is set to n, GCC will not use this heuristic for loops that are known to execute in fewer than n Advanced SIMD iterations. aarch64-vect-unroll-limit The vectorizer will use available tuning information to determine whether it would be beneficial to unroll the main vectorized loop and by how much. This parameter set's the upper bound of how much the vectorizer will unroll the main loop. The default value is four. The following choices of name are available on i386 and x86_64 targets: x86-stlf-window-ninsns Instructions number above which STFL stall penalty can be compensated. x86-stv-max-visits The maximum number of use and def visits when discovering a STV chain before the discovery is aborted. Program Instrumentation Options GCC supports a number of command-line options that control adding run- time instrumentation to the code it normally generates. For example, one purpose of instrumentation is collect profiling statistics for use in finding program hot spots, code coverage analysis, or profile-guided optimizations. Another class of program instrumentation is adding run- time checking to detect programming errors like invalid pointer dereferences or out-of-bounds array accesses, as well as deliberately hostile attacks such as stack smashing or C++ vtable hijacking. There is also a general hook which can be used to implement other forms of tracing or function-level instrumentation for debug or program analysis purposes. -p -pg Generate extra code to write profile information suitable for the analysis program prof (for -p) or gprof (for -pg). You must use this option when compiling the source files you want data about, and you must also use it when linking. You can use the function attribute "no_instrument_function" to suppress profiling of individual functions when compiling with these options. -fprofile-arcs Add code so that program flow arcs are instrumented. During execution the program records how many times each branch and call is executed and how many times it is taken or returns. On targets that support constructors with priority support, profiling properly handles constructors, destructors and C++ constructors (and destructors) of classes which are used as a type of a global variable. When the compiled program exits it saves this data to a file called auxname.gcda for each source file. The data may be used for profile-directed optimizations (-fbranch-probabilities), or for test coverage analysis (-ftest-coverage). Each object file's auxname is generated from the name of the output file, if explicitly specified and it is not the final executable, otherwise it is the basename of the source file. In both cases any suffix is removed (e.g. foo.gcda for input file dir/foo.c, or dir/foo.gcda for output file specified as -o dir/foo.o). Note that if a command line directly links source files, the corresponding .gcda files will be prefixed with the unsuffixed name of the output file. E.g. "gcc a.c b.c -o binary" would generate binary-a.gcda and binary-b.gcda files. --coverage This option is used to compile and link code instrumented for coverage analysis. The option is a synonym for -fprofile-arcs -ftest-coverage (when compiling) and -lgcov (when linking). See the documentation for those options for more details. * Compile the source files with -fprofile-arcs plus optimization and code generation options. For test coverage analysis, use the additional -ftest-coverage option. You do not need to profile every source file in a program. * Compile the source files additionally with -fprofile-abs-path to create absolute path names in the .gcno files. This allows gcov to find the correct sources in projects where compilations occur with different working directories. * Link your object files with -lgcov or -fprofile-arcs (the latter implies the former). * Run the program on a representative workload to generate the arc profile information. This may be repeated any number of times. You can run concurrent instances of your program, and provided that the file system supports locking, the data files will be correctly updated. Unless a strict ISO C dialect option is in effect, "fork" calls are detected and correctly handled without double counting. Moreover, an object file can be recompiled multiple times and the corresponding .gcda file merges as long as the source file and the compiler options are unchanged. * For profile-directed optimizations, compile the source files again with the same optimization and code generation options plus -fbranch-probabilities. * For test coverage analysis, use gcov to produce human readable information from the .gcno and .gcda files. Refer to the gcov documentation for further information. With -fprofile-arcs, for each function of your program GCC creates a program flow graph, then finds a spanning tree for the graph. Only arcs that are not on the spanning tree have to be instrumented: the compiler adds code to count the number of times that these arcs are executed. When an arc is the only exit or only entrance to a block, the instrumentation code can be added to the block; otherwise, a new basic block must be created to hold the instrumentation code. -ftest-coverage Produce a notes file that the gcov code-coverage utility can use to show program coverage. Each source file's note file is called auxname.gcno. Refer to the -fprofile-arcs option above for a description of auxname and instructions on how to generate test coverage data. Coverage data matches the source files more closely if you do not optimize. -fprofile-abs-path Automatically convert relative source file names to absolute path names in the .gcno files. This allows gcov to find the correct sources in projects where compilations occur with different working directories. -fprofile-dir=path Set the directory to search for the profile data files in to path. This option affects only the profile data generated by -fprofile-generate, -ftest-coverage, -fprofile-arcs and used by -fprofile-use and -fbranch-probabilities and its related options. Both absolute and relative paths can be used. By default, GCC uses the current directory as path, thus the profile data file appears in the same directory as the object file. In order to prevent the file name clashing, if the object file name is not an absolute path, we mangle the absolute path of the sourcename.gcda file and use it as the file name of a .gcda file. See details about the file naming in -fprofile-arcs. See similar option -fprofile-note. When an executable is run in a massive parallel environment, it is recommended to save profile to different folders. That can be done with variables in path that are exported during run-time: %p process ID. %q{VAR} value of environment variable VAR -fprofile-generate -fprofile-generate=path Enable options usually used for instrumenting application to produce profile useful for later recompilation with profile feedback based optimization. You must use -fprofile-generate both when compiling and when linking your program. The following options are enabled: -fprofile-arcs, -fprofile-values, -finline-functions, and -fipa-bit-cp. If path is specified, GCC looks at the path to find the profile feedback data files. See -fprofile-dir. To optimize the program based on the collected profile information, use -fprofile-use. -fprofile-info-section -fprofile-info-section=name Register the profile information in the specified section instead of using a constructor/destructor. The section name is name if it is specified, otherwise the section name defaults to ".gcov_info". A pointer to the profile information generated by -fprofile-arcs is placed in the specified section for each translation unit. This option disables the profile information registration through a constructor and it disables the profile information processing through a destructor. This option is not intended to be used in hosted environments such as GNU/Linux. It targets freestanding environments (for example embedded systems) with limited resources which do not support constructors/destructors or the C library file I/O. The linker could collect the input sections in a continuous memory block and define start and end symbols. A GNU linker script example which defines a linker output section follows: .gcov_info : { PROVIDE (__gcov_info_start = .); KEEP (*(.gcov_info)) PROVIDE (__gcov_info_end = .); } The program could dump the profiling information registered in this linker set for example like this: #include <gcov.h> #include <stdio.h> #include <stdlib.h> extern const struct gcov_info *const __gcov_info_start[]; extern const struct gcov_info *const __gcov_info_end[]; static void dump (const void *d, unsigned n, void *arg) { const unsigned char *c = d; for (unsigned i = 0; i < n; ++i) printf ("%02x", c[i]); } static void filename (const char *f, void *arg) { __gcov_filename_to_gcfn (f, dump, arg ); } static void * allocate (unsigned length, void *arg) { return malloc (length); } static void dump_gcov_info (void) { const struct gcov_info *const *info = __gcov_info_start; const struct gcov_info *const *end = __gcov_info_end; /* Obfuscate variable to prevent compiler optimizations. */ __asm__ ("" : "+r" (info)); while (info != end) { void *arg = NULL; __gcov_info_to_gcda (*info, filename, dump, allocate, arg); putchar ('\n'); ++info; } } int main (void) { dump_gcov_info (); return 0; } The merge-stream subcommand of gcov-tool may be used to deserialize the data stream generated by the "__gcov_filename_to_gcfn" and "__gcov_info_to_gcda" functions and merge the profile information into .gcda files on the host filesystem. -fprofile-note=path If path is specified, GCC saves .gcno file into path location. If you combine the option with multiple source files, the .gcno file will be overwritten. -fprofile-prefix-path=path This option can be used in combination with profile-generate=profile_dir and profile-use=profile_dir to inform GCC where is the base directory of built source tree. By default profile_dir will contain files with mangled absolute paths of all object files in the built project. This is not desirable when directory used to build the instrumented binary differs from the directory used to build the binary optimized with profile feedback because the profile data will not be found during the optimized build. In such setups -fprofile-prefix-path=path with path pointing to the base directory of the build can be used to strip the irrelevant part of the path and keep all file names relative to the main build directory. -fprofile-prefix-map=old=new When compiling files residing in directory old, record profiling information (with --coverage) describing them as if the files resided in directory new instead. See also -ffile-prefix-map and -fcanon-prefix-map. -fprofile-update=method Alter the update method for an application instrumented for profile feedback based optimization. The method argument should be one of single, atomic or prefer-atomic. The first one is useful for single-threaded applications, while the second one prevents profile corruption by emitting thread-safe code. Warning: When an application does not properly join all threads (or creates an detached thread), a profile file can be still corrupted. Using prefer-atomic would be transformed either to atomic, when supported by a target, or to single otherwise. The GCC driver automatically selects prefer-atomic when -pthread is present in the command line. -fprofile-filter-files=regex Instrument only functions from files whose name matches any of the regular expressions (separated by semi-colons). For example, -fprofile-filter-files=main\.c;module.*\.c will instrument only main.c and all C files starting with 'module'. -fprofile-exclude-files=regex Instrument only functions from files whose name does not match any of the regular expressions (separated by semi-colons). For example, -fprofile-exclude-files=/usr/.* will prevent instrumentation of all files that are located in the /usr/ folder. -fprofile-reproducible=[multithreaded|parallel-runs|serial] Control level of reproducibility of profile gathered by "-fprofile-generate". This makes it possible to rebuild program with same outcome which is useful, for example, for distribution packages. With -fprofile-reproducible=serial the profile gathered by -fprofile-generate is reproducible provided the trained program behaves the same at each invocation of the train run, it is not multi-threaded and profile data streaming is always done in the same order. Note that profile streaming happens at the end of program run but also before "fork" function is invoked. Note that it is quite common that execution counts of some part of programs depends, for example, on length of temporary file names or memory space randomization (that may affect hash-table collision rate). Such non-reproducible part of programs may be annotated by "no_instrument_function" function attribute. gcov-dump with -l can be used to dump gathered data and verify that they are indeed reproducible. With -fprofile-reproducible=parallel-runs collected profile stays reproducible regardless the order of streaming of the data into gcda files. This setting makes it possible to run multiple instances of instrumented program in parallel (such as with "make -j"). This reduces quality of gathered data, in particular of indirect call profiling. -fsanitize=address Enable AddressSanitizer, a fast memory error detector. Memory access instructions are instrumented to detect out-of-bounds and use-after-free bugs. The option enables -fsanitize-address-use-after-scope. See <https://github.com/google/sanitizers/wiki/AddressSanitizer> for more details. The run-time behavior can be influenced using the ASAN_OPTIONS environment variable. When set to "help=1", the available options are shown at startup of the instrumented program. See <https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags> for a list of supported options. The option cannot be combined with -fsanitize=thread or -fsanitize=hwaddress. Note that the only target -fsanitize=hwaddress is currently supported on is AArch64. To get more accurate stack traces, it is possible to use options such as -O0, -O1, or -Og (which, for instance, prevent most function inlining), -fno-optimize-sibling-calls (which prevents optimizing sibling and tail recursive calls; this option is implicit for -O0, -O1, or -Og), or -fno-ipa-icf (which disables Identical Code Folding for functions). Since multiple runs of the program may yield backtraces with different addresses due to ASLR (Address Space Layout Randomization), it may be desirable to turn ASLR off. On Linux, this can be achieved with setarch `uname -m` -R ./prog. -fsanitize=kernel-address Enable AddressSanitizer for Linux kernel. See <https://github.com/google/kernel-sanitizers> for more details. -fsanitize=hwaddress Enable Hardware-assisted AddressSanitizer, which uses a hardware ability to ignore the top byte of a pointer to allow the detection of memory errors with a low memory overhead. Memory access instructions are instrumented to detect out-of-bounds and use- after-free bugs. The option enables -fsanitize-address-use-after-scope. See <https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html> for more details. The run-time behavior can be influenced using the HWASAN_OPTIONS environment variable. When set to "help=1", the available options are shown at startup of the instrumented program. The option cannot be combined with -fsanitize=thread or -fsanitize=address, and is currently only available on AArch64. -fsanitize=kernel-hwaddress Enable Hardware-assisted AddressSanitizer for compilation of the Linux kernel. Similar to -fsanitize=kernel-address but using an alternate instrumentation method, and similar to -fsanitize=hwaddress but with instrumentation differences necessary for compiling the Linux kernel. These differences are to avoid hwasan library initialization calls and to account for the stack pointer having a different value in its top byte. Note: This option has different defaults to the -fsanitize=hwaddress. Instrumenting the stack and alloca calls are not on by default but are still possible by specifying the command- line options --param hwasan-instrument-stack=1 and --param hwasan-instrument-allocas=1 respectively. Using a random frame tag is not implemented for kernel instrumentation. -fsanitize=pointer-compare Instrument comparison operation (<, <=, >, >=) with pointer operands. The option must be combined with either -fsanitize=kernel-address or -fsanitize=address The option cannot be combined with -fsanitize=thread. Note: By default the check is disabled at run time. To enable it, add "detect_invalid_pointer_pairs=2" to the environment variable ASAN_OPTIONS. Using "detect_invalid_pointer_pairs=1" detects invalid operation only when both pointers are non-null. -fsanitize=pointer-subtract Instrument subtraction with pointer operands. The option must be combined with either -fsanitize=kernel-address or -fsanitize=address The option cannot be combined with -fsanitize=thread. Note: By default the check is disabled at run time. To enable it, add "detect_invalid_pointer_pairs=2" to the environment variable ASAN_OPTIONS. Using "detect_invalid_pointer_pairs=1" detects invalid operation only when both pointers are non-null. -fsanitize=shadow-call-stack Enable ShadowCallStack, a security enhancement mechanism used to protect programs against return address overwrites (e.g. stack buffer overflows.) It works by saving a function's return address to a separately allocated shadow call stack in the function prologue and restoring the return address from the shadow call stack in the function epilogue. Instrumentation only occurs in functions that need to save the return address to the stack. Currently it only supports the aarch64 platform. It is specifically designed for linux kernels that enable the CONFIG_SHADOW_CALL_STACK option. For the user space programs, runtime support is not currently provided in libc and libgcc. Users who want to use this feature in user space need to provide their own support for the runtime. It should be noted that this may cause the ABI rules to be broken. On aarch64, the instrumentation makes use of the platform register "x18". This generally means that any code that may run on the same thread as code compiled with ShadowCallStack must be compiled with the flag -ffixed-x18, otherwise functions compiled without -ffixed-x18 might clobber "x18" and so corrupt the shadow stack pointer. Also, because there is no userspace runtime support, code compiled with ShadowCallStack cannot use exception handling. Use -fno-exceptions to turn off exceptions. See <https://clang.llvm.org/docs/ShadowCallStack.html> for more details. -fsanitize=thread Enable ThreadSanitizer, a fast data race detector. Memory access instructions are instrumented to detect data race bugs. See <https://github.com/google/sanitizers/wiki#threadsanitizer> for more details. The run-time behavior can be influenced using the TSAN_OPTIONS environment variable; see <https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags> for a list of supported options. The option cannot be combined with -fsanitize=address, -fsanitize=leak. Note that sanitized atomic builtins cannot throw exceptions when operating on invalid memory addresses with non-call exceptions (-fnon-call-exceptions). -fsanitize=leak Enable LeakSanitizer, a memory leak detector. This option only matters for linking of executables. The executable is linked against a library that overrides "malloc" and other allocator functions. See <https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer> for more details. The run-time behavior can be influenced using the LSAN_OPTIONS environment variable. The option cannot be combined with -fsanitize=thread. -fsanitize=undefined Enable UndefinedBehaviorSanitizer, a fast undefined behavior detector. Various computations are instrumented to detect undefined behavior at runtime. See <https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html> for more details. The run-time behavior can be influenced using the UBSAN_OPTIONS environment variable. Current suboptions are: -fsanitize=shift This option enables checking that the result of a shift operation is not undefined. Note that what exactly is considered undefined differs slightly between C and C++, as well as between ISO C90 and C99, etc. This option has two suboptions, -fsanitize=shift-base and -fsanitize=shift-exponent. -fsanitize=shift-exponent This option enables checking that the second argument of a shift operation is not negative and is smaller than the precision of the promoted first argument. -fsanitize=shift-base If the second argument of a shift operation is within range, check that the result of a shift operation is not undefined. Note that what exactly is considered undefined differs slightly between C and C++, as well as between ISO C90 and C99, etc. -fsanitize=integer-divide-by-zero Detect integer division by zero. -fsanitize=unreachable With this option, the compiler turns the "__builtin_unreachable" call into a diagnostics message call instead. When reaching the "__builtin_unreachable" call, the behavior is undefined. -fsanitize=vla-bound This option instructs the compiler to check that the size of a variable length array is positive. -fsanitize=null This option enables pointer checking. Particularly, the application built with this option turned on will issue an error message when it tries to dereference a NULL pointer, or if a reference (possibly an rvalue reference) is bound to a NULL pointer, or if a method is invoked on an object pointed by a NULL pointer. -fsanitize=return This option enables return statement checking. Programs built with this option turned on will issue an error message when the end of a non-void function is reached without actually returning a value. This option works in C++ only. -fsanitize=signed-integer-overflow This option enables signed integer overflow checking. We check that the result of "+", "*", and both unary and binary "-" does not overflow in the signed arithmetics. This also detects "INT_MIN / -1" signed division. Note, integer promotion rules must be taken into account. That is, the following is not an overflow: signed char a = SCHAR_MAX; a++; -fsanitize=bounds This option enables instrumentation of array bounds. Various out of bounds accesses are detected. Flexible array members, flexible array member-like arrays, and initializers of variables with static storage are not instrumented, with the exception of flexible array member-like arrays for which "-fstrict-flex-arrays" or "-fstrict-flex-arrays=" options or "strict_flex_array" attributes say they shouldn't be treated like flexible array member-like arrays. -fsanitize=bounds-strict This option enables strict instrumentation of array bounds. Most out of bounds accesses are detected, including flexible array member-like arrays. Initializers of variables with static storage are not instrumented. -fsanitize=alignment This option enables checking of alignment of pointers when they are dereferenced, or when a reference is bound to insufficiently aligned target, or when a method or constructor is invoked on insufficiently aligned object. -fsanitize=object-size This option enables instrumentation of memory references using the "__builtin_dynamic_object_size" function. Various out of bounds pointer accesses are detected. -fsanitize=float-divide-by-zero Detect floating-point division by zero. Unlike other similar options, -fsanitize=float-divide-by-zero is not enabled by -fsanitize=undefined, since floating-point division by zero can be a legitimate way of obtaining infinities and NaNs. -fsanitize=float-cast-overflow This option enables floating-point type to integer conversion checking. We check that the result of the conversion does not overflow. Unlike other similar options, -fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined. This option does not work well with "FE_INVALID" exceptions enabled. -fsanitize=nonnull-attribute This option enables instrumentation of calls, checking whether null values are not passed to arguments marked as requiring a non-null value by the "nonnull" function attribute. -fsanitize=returns-nonnull-attribute This option enables instrumentation of return statements in functions marked with "returns_nonnull" function attribute, to detect returning of null values from such functions. -fsanitize=bool This option enables instrumentation of loads from bool. If a value other than 0/1 is loaded, a run-time error is issued. -fsanitize=enum This option enables instrumentation of loads from an enum type. If a value outside the range of values for the enum type is loaded, a run-time error is issued. -fsanitize=vptr This option enables instrumentation of C++ member function calls, member accesses and some conversions between pointers to base and derived classes, to verify the referenced object has the correct dynamic type. -fsanitize=pointer-overflow This option enables instrumentation of pointer arithmetics. If the pointer arithmetics overflows, a run-time error is issued. -fsanitize=builtin This option enables instrumentation of arguments to selected builtin functions. If an invalid value is passed to such arguments, a run-time error is issued. E.g. passing 0 as the argument to "__builtin_ctz" or "__builtin_clz" invokes undefined behavior and is diagnosed by this option. Note that sanitizers tend to increase the rate of false positive warnings, most notably those around -Wmaybe-uninitialized. We recommend against combining -Werror and [the use of] sanitizers. While -ftrapv causes traps for signed overflows to be emitted, -fsanitize=undefined gives a diagnostic message. This currently works only for the C family of languages. -fno-sanitize=all This option disables all previously enabled sanitizers. -fsanitize=all is not allowed, as some sanitizers cannot be used together. -fasan-shadow-offset=number This option forces GCC to use custom shadow offset in AddressSanitizer checks. It is useful for experimenting with different shadow memory layouts in Kernel AddressSanitizer. -fsanitize-sections=s1,s2,... Sanitize global variables in selected user-defined sections. si may contain wildcards. -fsanitize-recover[=opts] -fsanitize-recover= controls error recovery mode for sanitizers mentioned in comma-separated list of opts. Enabling this option for a sanitizer component causes it to attempt to continue running the program as if no error happened. This means multiple runtime errors can be reported in a single program run, and the exit code of the program may indicate success even when errors have been reported. The -fno-sanitize-recover= option can be used to alter this behavior: only the first detected error is reported and program then exits with a non-zero exit code. Currently this feature only works for -fsanitize=undefined (and its suboptions except for -fsanitize=unreachable and -fsanitize=return), -fsanitize=float-cast-overflow, -fsanitize=float-divide-by-zero, -fsanitize=bounds-strict, -fsanitize=kernel-address and -fsanitize=address. For these sanitizers error recovery is turned on by default, except -fsanitize=address, for which this feature is experimental. -fsanitize-recover=all and -fno-sanitize-recover=all is also accepted, the former enables recovery for all sanitizers that support it, the latter disables recovery for all sanitizers that support it. Even if a recovery mode is turned on the compiler side, it needs to be also enabled on the runtime library side, otherwise the failures are still fatal. The runtime library defaults to "halt_on_error=0" for ThreadSanitizer and UndefinedBehaviorSanitizer, while default value for AddressSanitizer is "halt_on_error=1". This can be overridden through setting the "halt_on_error" flag in the corresponding environment variable. Syntax without an explicit opts parameter is deprecated. It is equivalent to specifying an opts list of: undefined,float-cast-overflow,float-divide-by-zero,bounds-strict -fsanitize-address-use-after-scope Enable sanitization of local variables to detect use-after-scope bugs. The option sets -fstack-reuse to none. -fsanitize-trap[=opts] The -fsanitize-trap= option instructs the compiler to report for sanitizers mentioned in comma-separated list of opts undefined behavior using "__builtin_trap" rather than a "libubsan" library routine. If this option is enabled for certain sanitizer, it takes precedence over the -fsanitizer-recover= for that sanitizer, "__builtin_trap" will be emitted and be fatal regardless of whether recovery is enabled or disabled using -fsanitize-recover=. The advantage of this is that the "libubsan" library is not needed and is not linked in, so this is usable even in freestanding environments. Currently this feature works with -fsanitize=undefined (and its suboptions except for -fsanitize=vptr), -fsanitize=float-cast-overflow, -fsanitize=float-divide-by-zero and -fsanitize=bounds-strict. "-fsanitize-trap=all" can be also specified, which enables it for "undefined" suboptions, -fsanitize=float-cast-overflow, -fsanitize=float-divide-by-zero and -fsanitize=bounds-strict. If "-fsanitize-trap=undefined" or "-fsanitize-trap=all" is used and "-fsanitize=vptr" is enabled on the command line, the instrumentation is silently ignored as the instrumentation always needs "libubsan" support, -fsanitize-trap=vptr is not allowed. -fsanitize-undefined-trap-on-error The -fsanitize-undefined-trap-on-error option is deprecated equivalent of -fsanitize-trap=all. -fsanitize-coverage=trace-pc Enable coverage-guided fuzzing code instrumentation. Inserts a call to "__sanitizer_cov_trace_pc" into every basic block. -fsanitize-coverage=trace-cmp Enable dataflow guided fuzzing code instrumentation. Inserts a call to "__sanitizer_cov_trace_cmp1", "__sanitizer_cov_trace_cmp2", "__sanitizer_cov_trace_cmp4" or "__sanitizer_cov_trace_cmp8" for integral comparison with both operands variable or "__sanitizer_cov_trace_const_cmp1", "__sanitizer_cov_trace_const_cmp2", "__sanitizer_cov_trace_const_cmp4" or "__sanitizer_cov_trace_const_cmp8" for integral comparison with one operand constant, "__sanitizer_cov_trace_cmpf" or "__sanitizer_cov_trace_cmpd" for float or double comparisons and "__sanitizer_cov_trace_switch" for switch statements. -fcf-protection=[full|branch|return|none|check] Enable code instrumentation of control-flow transfers to increase program security by checking that target addresses of control-flow transfer instructions (such as indirect function call, function return, indirect jump) are valid. This prevents diverting the flow of control to an unexpected target. This is intended to protect against such threats as Return-oriented Programming (ROP), and similarly call/jmp-oriented programming (COP/JOP). The value "branch" tells the compiler to implement checking of validity of control-flow transfer at the point of indirect branch instructions, i.e. call/jmp instructions. The value "return" implements checking of validity at the point of returning from a function. The value "full" is an alias for specifying both "branch" and "return". The value "none" turns off instrumentation. The value "check" is used for the final link with link-time optimization (LTO). An error is issued if LTO object files are compiled with different -fcf-protection values. The value "check" is ignored at the compile time. The macro "__CET__" is defined when -fcf-protection is used. The first bit of "__CET__" is set to 1 for the value "branch" and the second bit of "__CET__" is set to 1 for the "return". You can also use the "nocf_check" attribute to identify which functions and calls should be skipped from instrumentation. Currently the x86 GNU/Linux target provides an implementation based on Intel Control-flow Enforcement Technology (CET) which works for i686 processor or newer. -fharden-compares For every logical test that survives gimple optimizations and is not the condition in a conditional branch (for example, conditions tested for conditional moves, or to store in boolean variables), emit extra code to compute and verify the reversed condition, and to call "__builtin_trap" if the results do not match. Use with -fharden-conditional-branches to cover all conditionals. -fharden-conditional-branches For every non-vectorized conditional branch that survives gimple optimizations, emit extra code to compute and verify the reversed condition, and to call "__builtin_trap" if the result is unexpected. Use with -fharden-compares to cover all conditionals. -fstack-protector Emit extra code to check for buffer overflows, such as stack smashing attacks. This is done by adding a guard variable to functions with vulnerable objects. This includes functions that call "alloca", and functions with buffers larger than or equal to 8 bytes. The guards are initialized when a function is entered and then checked when the function exits. If a guard check fails, an error message is printed and the program exits. Only variables that are actually allocated on the stack are considered, optimized away variables or variables allocated in registers don't count. -fstack-protector-all Like -fstack-protector except that all functions are protected. -fstack-protector-strong Like -fstack-protector but includes additional functions to be protected --- those that have local array definitions, or have references to local frame addresses. Only variables that are actually allocated on the stack are considered, optimized away variables or variables allocated in registers don't count. -fstack-protector-explicit Like -fstack-protector but only protects those functions which have the "stack_protect" attribute. -fstack-check Generate code to verify that you do not go beyond the boundary of the stack. You should specify this flag if you are running in an environment with multiple threads, but you only rarely need to specify it in a single-threaded environment since stack overflow is automatically detected on nearly all systems if there is only one stack. Note that this switch does not actually cause checking to be done; the operating system or the language runtime must do that. The switch causes generation of code to ensure that they see the stack being extended. You can additionally specify a string parameter: no means no checking, generic means force the use of old-style checking, specific means use the best checking method and is equivalent to bare -fstack-check. Old-style checking is a generic mechanism that requires no specific target support in the compiler but comes with the following drawbacks: 1. Modified allocation strategy for large objects: they are always allocated dynamically if their size exceeds a fixed threshold. Note this may change the semantics of some code. 2. Fixed limit on the size of the static frame of functions: when it is topped by a particular function, stack checking is not reliable and a warning is issued by the compiler. 3. Inefficiency: because of both the modified allocation strategy and the generic implementation, code performance is hampered. Note that old-style stack checking is also the fallback method for specific if no target support has been added in the compiler. -fstack-check= is designed for Ada's needs to detect infinite recursion and stack overflows. specific is an excellent choice when compiling Ada code. It is not generally sufficient to protect against stack-clash attacks. To protect against those you want -fstack-clash-protection. -fstack-clash-protection Generate code to prevent stack clash style attacks. When this option is enabled, the compiler will only allocate one page of stack space at a time and each page is accessed immediately after allocation. Thus, it prevents allocations from jumping over any stack guard page provided by the operating system. Most targets do not fully support stack clash protection. However, on those targets -fstack-clash-protection will protect dynamic stack allocations. -fstack-clash-protection may also provide limited protection for static stack allocations if the target supports -fstack-check=specific. -fstack-limit-register=reg -fstack-limit-symbol=sym -fno-stack-limit Generate code to ensure that the stack does not grow beyond a certain value, either the value of a register or the address of a symbol. If a larger stack is required, a signal is raised at run time. For most targets, the signal is raised before the stack overruns the boundary, so it is possible to catch the signal without taking special precautions. For instance, if the stack starts at absolute address 0x80000000 and grows downwards, you can use the flags -fstack-limit-symbol=__stack_limit and -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of 128KB. Note that this may only work with the GNU linker. You can locally override stack limit checking by using the "no_stack_limit" function attribute. -fsplit-stack Generate code to automatically split the stack before it overflows. The resulting program has a discontiguous stack which can only overflow if the program is unable to allocate any more memory. This is most useful when running threaded programs, as it is no longer necessary to calculate a good stack size to use for each thread. This is currently only implemented for the x86 targets running GNU/Linux. When code compiled with -fsplit-stack calls code compiled without -fsplit-stack, there may not be much stack space available for the latter code to run. If compiling all code, including library code, with -fsplit-stack is not an option, then the linker can fix up these calls so that the code compiled without -fsplit-stack always has a large stack. Support for this is implemented in the gold linker in GNU binutils release 2.21 and later. -fvtable-verify=[std|preinit|none] This option is only available when compiling C++ code. It turns on (or off, if using -fvtable-verify=none) the security feature that verifies at run time, for every virtual call, that the vtable pointer through which the call is made is valid for the type of the object, and has not been corrupted or overwritten. If an invalid vtable pointer is detected at run time, an error is reported and execution of the program is immediately halted. This option causes run-time data structures to be built at program startup, which are used for verifying the vtable pointers. The options std and preinit control the timing of when these data structures are built. In both cases the data structures are built before execution reaches "main". Using -fvtable-verify=std causes the data structures to be built after shared libraries have been loaded and initialized. -fvtable-verify=preinit causes them to be built before shared libraries have been loaded and initialized. If this option appears multiple times in the command line with different values specified, none takes highest priority over both std and preinit; preinit takes priority over std. -fvtv-debug When used in conjunction with -fvtable-verify=std or -fvtable-verify=preinit, causes debug versions of the runtime functions for the vtable verification feature to be called. This flag also causes the compiler to log information about which vtable pointers it finds for each class. This information is written to a file named vtv_set_ptr_data.log in the directory named by the environment variable VTV_LOGS_DIR if that is defined or the current working directory otherwise. Note: This feature appends data to the log file. If you want a fresh log file, be sure to delete any existing one. -fvtv-counts This is a debugging flag. When used in conjunction with -fvtable-verify=std or -fvtable-verify=preinit, this causes the compiler to keep track of the total number of virtual calls it encounters and the number of verifications it inserts. It also counts the number of calls to certain run-time library functions that it inserts and logs this information for each compilation unit. The compiler writes this information to a file named vtv_count_data.log in the directory named by the environment variable VTV_LOGS_DIR if that is defined or the current working directory otherwise. It also counts the size of the vtable pointer sets for each class, and writes this information to vtv_class_set_sizes.log in the same directory. Note: This feature appends data to the log files. To get fresh log files, be sure to delete any existing ones. -finstrument-functions Generate instrumentation calls for entry and exit to functions. Just after function entry and just before function exit, the following profiling functions are called with the address of the current function and its call site. (On some platforms, "__builtin_return_address" does not work beyond the current function, so the call site information may not be available to the profiling functions otherwise.) void __cyg_profile_func_enter (void *this_fn, void *call_site); void __cyg_profile_func_exit (void *this_fn, void *call_site); The first argument is the address of the start of the current function, which may be looked up exactly in the symbol table. This instrumentation is also done for functions expanded inline in other functions. The profiling calls indicate where, conceptually, the inline function is entered and exited. This means that addressable versions of such functions must be available. If all your uses of a function are expanded inline, this may mean an additional expansion of code size. If you use "extern inline" in your C code, an addressable version of such functions must be provided. (This is normally the case anyway, but if you get lucky and the optimizer always expands the functions inline, you might have gotten away without providing static copies.) A function may be given the attribute "no_instrument_function", in which case this instrumentation is not done. This can be used, for example, for the profiling functions listed above, high-priority interrupt routines, and any functions from which the profiling functions cannot safely be called (perhaps signal handlers, if the profiling routines generate output or allocate memory). -finstrument-functions-once This is similar to -finstrument-functions, but the profiling functions are called only once per instrumented function, i.e. the first profiling function is called after the first entry into the instrumented function and the second profiling function is called before the exit corresponding to this first entry. The definition of "once" for the purpose of this option is a little vague because the implementation is not protected against data races. As a result, the implementation only guarantees that the profiling functions are called at least once per process and at most once per thread, but the calls are always paired, that is to say, if a thread calls the first function, then it will call the second function, unless it never reaches the exit of the instrumented function. -finstrument-functions-exclude-file-list=file,file,... Set the list of functions that are excluded from instrumentation (see the description of -finstrument-functions). If the file that contains a function definition matches with one of file, then that function is not instrumented. The match is done on substrings: if the file parameter is a substring of the file name, it is considered to be a match. For example: -finstrument-functions-exclude-file-list=/bits/stl,include/sys excludes any inline function defined in files whose pathnames contain /bits/stl or include/sys. If, for some reason, you want to include letter , in one of sym, write ,. For example, -finstrument-functions-exclude-file-list=',,tmp' (note the single quote surrounding the option). -finstrument-functions-exclude-function-list=sym,sym,... This is similar to -finstrument-functions-exclude-file-list, but this option sets the list of function names to be excluded from instrumentation. The function name to be matched is its user- visible name, such as "vector<int> blah(const vector<int> &)", not the internal mangled name (e.g., "_Z4blahRSt6vectorIiSaIiEE"). The match is done on substrings: if the sym parameter is a substring of the function name, it is considered to be a match. For C99 and C++ extended identifiers, the function name must be given in UTF-8, not using universal character names. -fpatchable-function-entry=N[,M] Generate N NOPs right at the beginning of each function, with the function entry point before the Mth NOP. If M is omitted, it defaults to 0 so the function entry points to the address just at the first NOP. The NOP instructions reserve extra space which can be used to patch in any desired instrumentation at run time, provided that the code segment is writable. The amount of space is controllable indirectly via the number of NOPs; the NOP instruction used corresponds to the instruction emitted by the internal GCC back-end interface "gen_nop". This behavior is target-specific and may also depend on the architecture variant and/or other compilation options. For run-time identification, the starting addresses of these areas, which correspond to their respective function entries minus M, are additionally collected in the "__patchable_function_entries" section of the resulting binary. Note that the value of "__attribute__ ((patchable_function_entry (N,M)))" takes precedence over command-line option -fpatchable-function-entry=N,M. This can be used to increase the area size or to remove it completely on a single function. If "N=0", no pad location is recorded. The NOP instructions are inserted at---and maybe before, depending on M---the function entry address, even before the prologue. On PowerPC with the ELFv2 ABI, for a function with dual entry points, the local entry point is this function entry address. The maximum value of N and M is 65535. On PowerPC with the ELFv2 ABI, for a function with dual entry points, the supported values for M are 0, 2, 6 and 14. Options Controlling the Preprocessor These options control the C preprocessor, which is run on each C source file before actual compilation. If you use the -E option, nothing is done except preprocessing. Some of these options make sense only together with -E because they cause the preprocessor output to be unsuitable for actual compilation. In addition to the options listed here, there are a number of options to control search paths for include files documented in Directory Options. Options to control preprocessor diagnostics are listed in Warning Options. -D name Predefine name as a macro, with definition 1. -D name=definition The contents of definition are tokenized and processed as if they appeared during translation phase three in a #define directive. In particular, the definition is truncated by embedded newline characters. If you are invoking the preprocessor from a shell or shell-like program you may need to use the shell's quoting syntax to protect characters such as spaces that have a meaning in the shell syntax. If you wish to define a function-like macro on the command line, write its argument list with surrounding parentheses before the equals sign (if any). Parentheses are meaningful to most shells, so you should quote the option. With sh and csh, -D'name(args...)=definition' works. -D and -U options are processed in the order they are given on the command line. All -imacros file and -include file options are processed after all -D and -U options. -U name Cancel any previous definition of name, either built in or provided with a -D option. -include file Process file as if "#include "file"" appeared as the first line of the primary source file. However, the first directory searched for file is the preprocessor's working directory instead of the directory containing the main source file. If not found there, it is searched for in the remainder of the "#include "..."" search chain as normal. If multiple -include options are given, the files are included in the order they appear on the command line. -imacros file Exactly like -include, except that any output produced by scanning file is thrown away. Macros it defines remain defined. This allows you to acquire all the macros from a header without also processing its declarations. All files specified by -imacros are processed before all files specified by -include. -undef Do not predefine any system-specific or GCC-specific macros. The standard predefined macros remain defined. -pthread Define additional macros required for using the POSIX threads library. You should use this option consistently for both compilation and linking. This option is supported on GNU/Linux targets, most other Unix derivatives, and also on x86 Cygwin and MinGW targets. -M Instead of outputting the result of preprocessing, output a rule suitable for make describing the dependencies of the main source file. The preprocessor outputs one make rule containing the object file name for that source file, a colon, and the names of all the included files, including those coming from -include or -imacros command-line options. Unless specified explicitly (with -MT or -MQ), the object file name consists of the name of the source file with any suffix replaced with object file suffix and with any leading directory parts removed. If there are many included files then the rule is split into several lines using \-newline. The rule has no commands. This option does not suppress the preprocessor's debug output, such as -dM. To avoid mixing such debug output with the dependency rules you should explicitly specify the dependency output file with -MF, or use an environment variable like DEPENDENCIES_OUTPUT. Debug output is still sent to the regular output stream as normal. Passing -M to the driver implies -E, and suppresses warnings with an implicit -w. -MM Like -M but do not mention header files that are found in system header directories, nor header files that are included, directly or indirectly, from such a header. This implies that the choice of angle brackets or double quotes in an #include directive does not in itself determine whether that header appears in -MM dependency output. -MF file When used with -M or -MM, specifies a file to write the dependencies to. If no -MF switch is given the preprocessor sends the rules to the same place it would send preprocessed output. When used with the driver options -MD or -MMD, -MF overrides the default dependency output file. If file is -, then the dependencies are written to stdout. -MG In conjunction with an option such as -M requesting dependency generation, -MG assumes missing header files are generated files and adds them to the dependency list without raising an error. The dependency filename is taken directly from the "#include" directive without prepending any path. -MG also suppresses preprocessed output, as a missing header file renders this useless. This feature is used in automatic updating of makefiles. -Mno-modules Disable dependency generation for compiled module interfaces. -MP This option instructs CPP to add a phony target for each dependency other than the main file, causing each to depend on nothing. These dummy rules work around errors make gives if you remove header files without updating the Makefile to match. This is typical output: test.o: test.c test.h test.h: -MT target Change the target of the rule emitted by dependency generation. By default CPP takes the name of the main input file, deletes any directory components and any file suffix such as .c, and appends the platform's usual object suffix. The result is the target. An -MT option sets the target to be exactly the string you specify. If you want multiple targets, you can specify them as a single argument to -MT, or use multiple -MT options. For example, -MT '$(objpfx)foo.o' might give $(objpfx)foo.o: foo.c -MQ target Same as -MT, but it quotes any characters which are special to Make. -MQ '$(objpfx)foo.o' gives $$(objpfx)foo.o: foo.c The default target is automatically quoted, as if it were given with -MQ. -MD -MD is equivalent to -M -MF file, except that -E is not implied. The driver determines file based on whether an -o option is given. If it is, the driver uses its argument but with a suffix of .d, otherwise it takes the name of the input file, removes any directory components and suffix, and applies a .d suffix. If -MD is used in conjunction with -E, any -o switch is understood to specify the dependency output file, but if used without -E, each -o is understood to specify a target object file. Since -E is not implied, -MD can be used to generate a dependency output file as a side effect of the compilation process. -MMD Like -MD except mention only user header files, not system header files. -fpreprocessed Indicate to the preprocessor that the input file has already been preprocessed. This suppresses things like macro expansion, trigraph conversion, escaped newline splicing, and processing of most directives. The preprocessor still recognizes and removes comments, so that you can pass a file preprocessed with -C to the compiler without problems. In this mode the integrated preprocessor is little more than a tokenizer for the front ends. -fpreprocessed is implicit if the input file has one of the extensions .i, .ii or .mi. These are the extensions that GCC uses for preprocessed files created by -save-temps. -fdirectives-only When preprocessing, handle directives, but do not expand macros. The option's behavior depends on the -E and -fpreprocessed options. With -E, preprocessing is limited to the handling of directives such as "#define", "#ifdef", and "#error". Other preprocessor operations, such as macro expansion and trigraph conversion are not performed. In addition, the -dD option is implicitly enabled. With -fpreprocessed, predefinition of command line and most builtin macros is disabled. Macros such as "__LINE__", which are contextually dependent, are handled normally. This enables compilation of files previously preprocessed with "-E -fdirectives-only". With both -E and -fpreprocessed, the rules for -fpreprocessed take precedence. This enables full preprocessing of files previously preprocessed with "-E -fdirectives-only". -fdollars-in-identifiers Accept $ in identifiers. -fextended-identifiers Accept universal character names and extended characters in identifiers. This option is enabled by default for C99 (and later C standard versions) and C++. -fno-canonical-system-headers When preprocessing, do not shorten system header paths with canonicalization. -fmax-include-depth=depth Set the maximum depth of the nested #include. The default is 200. -ftabstop=width Set the distance between tab stops. This helps the preprocessor report correct column numbers in warnings or errors, even if tabs appear on the line. If the value is less than 1 or greater than 100, the option is ignored. The default is 8. -ftrack-macro-expansion[=level] Track locations of tokens across macro expansions. This allows the compiler to emit diagnostic about the current macro expansion stack when a compilation error occurs in a macro expansion. Using this option makes the preprocessor and the compiler consume more memory. The level parameter can be used to choose the level of precision of token location tracking thus decreasing the memory consumption if necessary. Value 0 of level de-activates this option. Value 1 tracks tokens locations in a degraded mode for the sake of minimal memory overhead. In this mode all tokens resulting from the expansion of an argument of a function-like macro have the same location. Value 2 tracks tokens locations completely. This value is the most memory hungry. When this option is given no argument, the default parameter value is 2. Note that "-ftrack-macro-expansion=2" is activated by default. -fmacro-prefix-map=old=new When preprocessing files residing in directory old, expand the "__FILE__" and "__BASE_FILE__" macros as if the files resided in directory new instead. This can be used to change an absolute path to a relative path by using . for new which can result in more reproducible builds that are location independent. This option also affects "__builtin_FILE()" during compilation. See also -ffile-prefix-map and -fcanon-prefix-map. -fexec-charset=charset Set the execution character set, used for string and character constants. The default is UTF-8. charset can be any encoding supported by the system's "iconv" library routine. -fwide-exec-charset=charset Set the wide execution character set, used for wide string and character constants. The default is one of UTF-32BE, UTF-32LE, UTF-16BE, or UTF-16LE, whichever corresponds to the width of "wchar_t" and the big-endian or little-endian byte order being used for code generation. As with -fexec-charset, charset can be any encoding supported by the system's "iconv" library routine; however, you will have problems with encodings that do not fit exactly in "wchar_t". -finput-charset=charset Set the input character set, used for translation from the character set of the input file to the source character set used by GCC. If the locale does not specify, or GCC cannot get this information from the locale, the default is UTF-8. This can be overridden by either the locale or this command-line option. Currently the command-line option takes precedence if there's a conflict. charset can be any encoding supported by the system's "iconv" library routine. -fpch-deps When using precompiled headers, this flag causes the dependency- output flags to also list the files from the precompiled header's dependencies. If not specified, only the precompiled header are listed and not the files that were used to create it, because those files are not consulted when a precompiled header is used. -fpch-preprocess This option allows use of a precompiled header together with -E. It inserts a special "#pragma", "#pragma GCC pch_preprocess "filename"" in the output to mark the place where the precompiled header was found, and its filename. When -fpreprocessed is in use, GCC recognizes this "#pragma" and loads the PCH. This option is off by default, because the resulting preprocessed output is only really suitable as input to GCC. It is switched on by -save-temps. You should not write this "#pragma" in your own code, but it is safe to edit the filename if the PCH file is available in a different location. The filename may be absolute or it may be relative to GCC's current directory. -fworking-directory Enable generation of linemarkers in the preprocessor output that let the compiler know the current working directory at the time of preprocessing. When this option is enabled, the preprocessor emits, after the initial linemarker, a second linemarker with the current working directory followed by two slashes. GCC uses this directory, when it's present in the preprocessed input, as the directory emitted as the current working directory in some debugging information formats. This option is implicitly enabled if debugging information is enabled, but this can be inhibited with the negated form -fno-working-directory. If the -P flag is present in the command line, this option has no effect, since no "#line" directives are emitted whatsoever. -A predicate=answer Make an assertion with the predicate predicate and answer answer. This form is preferred to the older form -A predicate(answer), which is still supported, because it does not use shell special characters. -A -predicate=answer Cancel an assertion with the predicate predicate and answer answer. -C Do not discard comments. All comments are passed through to the output file, except for comments in processed directives, which are deleted along with the directive. You should be prepared for side effects when using -C; it causes the preprocessor to treat comments as tokens in their own right. For example, comments appearing at the start of what would be a directive line have the effect of turning that line into an ordinary source line, since the first token on the line is no longer a #. -CC Do not discard comments, including during macro expansion. This is like -C, except that comments contained within macros are also passed through to the output file where the macro is expanded. In addition to the side effects of the -C option, the -CC option causes all C++-style comments inside a macro to be converted to C-style comments. This is to prevent later use of that macro from inadvertently commenting out the remainder of the source line. The -CC option is generally used to support lint comments. -P Inhibit generation of linemarkers in the output from the preprocessor. This might be useful when running the preprocessor on something that is not C code, and will be sent to a program which might be confused by the linemarkers. -traditional -traditional-cpp Try to imitate the behavior of pre-standard C preprocessors, as opposed to ISO C preprocessors. See the GNU CPP manual for details. Note that GCC does not otherwise attempt to emulate a pre-standard C compiler, and these options are only supported with the -E switch, or when invoking CPP explicitly. -trigraphs Support ISO C trigraphs. These are three-character sequences, all starting with ??, that are defined by ISO C to stand for single characters. For example, ??/ stands for \, so '??/n' is a character constant for a newline. The nine trigraphs and their replacements are Trigraph: ??( ??) ??< ??> ??= ??/ ??' ??! ??- Replacement: [ ] { } # \ ^ | ~ By default, GCC ignores trigraphs, but in standard-conforming modes it converts them. See the -std and -ansi options. -remap Enable special code to work around file systems which only permit very short file names, such as MS-DOS. -H Print the name of each header file used, in addition to other normal activities. Each name is indented to show how deep in the #include stack it is. Precompiled header files are also printed, even if they are found to be invalid; an invalid precompiled header file is printed with ...x and a valid one with ...! . -dletters Says to make debugging dumps during compilation as specified by letters. The flags documented here are those relevant to the preprocessor. Other letters are interpreted by the compiler proper, or reserved for future versions of GCC, and so are silently ignored. If you specify letters whose behavior conflicts, the result is undefined. -dM Instead of the normal output, generate a list of #define directives for all the macros defined during the execution of the preprocessor, including predefined macros. This gives you a way of finding out what is predefined in your version of the preprocessor. Assuming you have no file foo.h, the command touch foo.h; cpp -dM foo.h shows all the predefined macros. If you use -dM without the -E option, -dM is interpreted as a synonym for -fdump-rtl-mach. -dD Like -dM except in two respects: it does not include the predefined macros, and it outputs both the #define directives and the result of preprocessing. Both kinds of output go to the standard output file. -dN Like -dD, but emit only the macro names, not their expansions. -dI Output #include directives in addition to the result of preprocessing. -dU Like -dD except that only macros that are expanded, or whose definedness is tested in preprocessor directives, are output; the output is delayed until the use or test of the macro; and #undef directives are also output for macros tested but undefined at the time. -fdebug-cpp This option is only useful for debugging GCC. When used from CPP or with -E, it dumps debugging information about location maps. Every token in the output is preceded by the dump of the map its location belongs to. When used from GCC without -E, this option has no effect. -Wp,option You can use -Wp,option to bypass the compiler driver and pass option directly through to the preprocessor. If option contains commas, it is split into multiple options at the commas. However, many options are modified, translated or interpreted by the compiler driver before being passed to the preprocessor, and -Wp forcibly bypasses this phase. The preprocessor's direct interface is undocumented and subject to change, so whenever possible you should avoid using -Wp and let the driver handle the options instead. -Xpreprocessor option Pass option as an option to the preprocessor. You can use this to supply system-specific preprocessor options that GCC does not recognize. If you want to pass an option that takes an argument, you must use -Xpreprocessor twice, once for the option and once for the argument. -no-integrated-cpp Perform preprocessing as a separate pass before compilation. By default, GCC performs preprocessing as an integrated part of input tokenization and parsing. If this option is provided, the appropriate language front end (cc1, cc1plus, or cc1obj for C, C++, and Objective-C, respectively) is instead invoked twice, once for preprocessing only and once for actual compilation of the preprocessed input. This option may be useful in conjunction with the -B or -wrapper options to specify an alternate preprocessor or perform additional processing of the program source between normal preprocessing and compilation. -flarge-source-files Adjust GCC to expect large source files, at the expense of slower compilation and higher memory usage. Specifically, GCC normally tracks both column numbers and line numbers within source files and it normally prints both of these numbers in diagnostics. However, once it has processed a certain number of source lines, it stops tracking column numbers and only tracks line numbers. This means that diagnostics for later lines do not include column numbers. It also means that options like -Wmisleading-indentation cease to work at that point, although the compiler prints a note if this happens. Passing -flarge-source-files significantly increases the number of source lines that GCC can process before it stops tracking columns. Passing Options to the Assembler You can pass options to the assembler. -Wa,option Pass option as an option to the assembler. If option contains commas, it is split into multiple options at the commas. -Xassembler option Pass option as an option to the assembler. You can use this to supply system-specific assembler options that GCC does not recognize. If you want to pass an option that takes an argument, you must use -Xassembler twice, once for the option and once for the argument. Options for Linking These options come into play when the compiler links object files into an executable output file. They are meaningless if the compiler is not doing a link step. object-file-name A file name that does not end in a special recognized suffix is considered to name an object file or library. (Object files are distinguished from libraries by the linker according to the file contents.) If linking is done, these object files are used as input to the linker. -c -S -E If any of these options is used, then the linker is not run, and object file names should not be used as arguments. -flinker-output=type This option controls code generation of the link-time optimizer. By default the linker output is automatically determined by the linker plugin. For debugging the compiler and if incremental linking with a non-LTO object file is desired, it may be useful to control the type manually. If type is exec, code generation produces a static binary. In this case -fpic and -fpie are both disabled. If type is dyn, code generation produces a shared library. In this case -fpic or -fPIC is preserved, but not enabled automatically. This allows to build shared libraries without position-independent code on architectures where this is possible, i.e. on x86. If type is pie, code generation produces an -fpie executable. This results in similar optimizations as exec except that -fpie is not disabled if specified at compilation time. If type is rel, the compiler assumes that incremental linking is done. The sections containing intermediate code for link-time optimization are merged, pre-optimized, and output to the resulting object file. In addition, if -ffat-lto-objects is specified, binary code is produced for future non-LTO linking. The object file produced by incremental linking is smaller than a static library produced from the same object files. At link time the result of incremental linking also loads faster than a static library assuming that the majority of objects in the library are used. Finally nolto-rel configures the compiler for incremental linking where code generation is forced, a final binary is produced, and the intermediate code for later link-time optimization is stripped. When multiple object files are linked together the resulting code is better optimized than with link-time optimizations disabled (for example, cross-module inlining happens), but most of benefits of whole program optimizations are lost. During the incremental link (by -r) the linker plugin defaults to rel. With current interfaces to GNU Binutils it is however not possible to incrementally link LTO objects and non-LTO objects into a single mixed object file. If any of object files in incremental link cannot be used for link-time optimization, the linker plugin issues a warning and uses nolto-rel. To maintain whole program optimization, it is recommended to link such objects into static library instead. Alternatively it is possible to use H.J. Lu's binutils with support for mixed objects. -fuse-ld=bfd Use the bfd linker instead of the default linker. -fuse-ld=gold Use the gold linker instead of the default linker. -fuse-ld=lld Use the LLVM lld linker instead of the default linker. -fuse-ld=mold Use the Modern Linker (mold) instead of the default linker. -llibrary -l library Search the library named library when linking. (The second alternative with the library as a separate argument is only for POSIX compliance and is not recommended.) The -l option is passed directly to the linker by GCC. Refer to your linker documentation for exact details. The general description below applies to the GNU linker. The linker searches a standard list of directories for the library. The directories searched include several standard system directories plus any that you specify with -L. Static libraries are archives of object files, and have file names like liblibrary.a. Some targets also support shared libraries, which typically have names like liblibrary.so. If both static and shared libraries are found, the linker gives preference to linking with the shared library unless the -static option is used. It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, foo.o -lz bar.o searches library z after file foo.o but before bar.o. If bar.o refers to functions in z, those functions may not be loaded. -lobjc You need this special case of the -l option in order to link an Objective-C or Objective-C++ program. -nostartfiles Do not use the standard system startup files when linking. The standard system libraries are used normally, unless -nostdlib, -nolibc, or -nodefaultlibs is used. -nodefaultlibs Do not use the standard system libraries when linking. Only the libraries you specify are passed to the linker, and options specifying linkage of the system libraries, such as -static-libgcc or -shared-libgcc, are ignored. The standard startup files are used normally, unless -nostartfiles is used. The compiler may generate calls to "memcmp", "memset", "memcpy" and "memmove". These entries are usually resolved by entries in libc. These entry points should be supplied through some other mechanism when this option is specified. -nolibc Do not use the C library or system libraries tightly coupled with it when linking. Still link with the startup files, libgcc or toolchain provided language support libraries such as libgnat, libgfortran or libstdc++ unless options preventing their inclusion are used as well. This typically removes -lc from the link command line, as well as system libraries that normally go with it and become meaningless when absence of a C library is assumed, for example -lpthread or -lm in some configurations. This is intended for bare-board targets when there is indeed no C library available. -nostdlib Do not use the standard system startup files or libraries when linking. No startup files and only the libraries you specify are passed to the linker, and options specifying linkage of the system libraries, such as -static-libgcc or -shared-libgcc, are ignored. The compiler may generate calls to "memcmp", "memset", "memcpy" and "memmove". These entries are usually resolved by entries in libc. These entry points should be supplied through some other mechanism when this option is specified. One of the standard libraries bypassed by -nostdlib and -nodefaultlibs is libgcc.a, a library of internal subroutines which GCC uses to overcome shortcomings of particular machines, or special needs for some languages. In most cases, you need libgcc.a even when you want to avoid other standard libraries. In other words, when you specify -nostdlib or -nodefaultlibs you should usually specify -lgcc as well. This ensures that you have no unresolved references to internal GCC library subroutines. (An example of such an internal subroutine is "__main", used to ensure C++ constructors are called.) -nostdlib++ Do not implicitly link with standard C++ libraries. -e entry --entry=entry Specify that the program entry point is entry. The argument is interpreted by the linker; the GNU linker accepts either a symbol name or an address. -pie Produce a dynamically linked position independent executable on targets that support it. For predictable results, you must also specify the same set of options used for compilation (-fpie, -fPIE, or model suboptions) when you specify this linker option. -no-pie Don't produce a dynamically linked position independent executable. -static-pie Produce a static position independent executable on targets that support it. A static position independent executable is similar to a static executable, but can be loaded at any address without a dynamic linker. For predictable results, you must also specify the same set of options used for compilation (-fpie, -fPIE, or model suboptions) when you specify this linker option. -pthread Link with the POSIX threads library. This option is supported on GNU/Linux targets, most other Unix derivatives, and also on x86 Cygwin and MinGW targets. On some targets this option also sets flags for the preprocessor, so it should be used consistently for both compilation and linking. -r Produce a relocatable object as output. This is also known as partial linking. -rdynamic Pass the flag -export-dynamic to the ELF linker, on targets that support it. This instructs the linker to add all symbols, not only used ones, to the dynamic symbol table. This option is needed for some uses of "dlopen" or to allow obtaining backtraces from within a program. -s Remove all symbol table and relocation information from the executable. -static On systems that support dynamic linking, this overrides -pie and prevents linking with the shared libraries. On other systems, this option has no effect. -shared Produce a shared object which can then be linked with other objects to form an executable. Not all systems support this option. For predictable results, you must also specify the same set of options used for compilation (-fpic, -fPIC, or model suboptions) when you specify this linker option.[1] -shared-libgcc -static-libgcc On systems that provide libgcc as a shared library, these options force the use of either the shared or static version, respectively. If no shared version of libgcc was built when the compiler was configured, these options have no effect. There are several situations in which an application should use the shared libgcc instead of the static version. The most common of these is when the application wishes to throw and catch exceptions across different shared libraries. In that case, each of the libraries as well as the application itself should use the shared libgcc. Therefore, the G++ driver automatically adds -shared-libgcc whenever you build a shared library or a main executable, because C++ programs typically use exceptions, so this is the right thing to do. If, instead, you use the GCC driver to create shared libraries, you may find that they are not always linked with the shared libgcc. If GCC finds, at its configuration time, that you have a non-GNU linker or a GNU linker that does not support option --eh-frame-hdr, it links the shared version of libgcc into shared libraries by default. Otherwise, it takes advantage of the linker and optimizes away the linking with the shared version of libgcc, linking with the static version of libgcc by default. This allows exceptions to propagate through such shared libraries, without incurring relocation costs at library load time. However, if a library or main executable is supposed to throw or catch exceptions, you must link it using the G++ driver, or using the option -shared-libgcc, such that it is linked with the shared libgcc. -static-libasan When the -fsanitize=address option is used to link a program, the GCC driver automatically links against libasan. If libasan is available as a shared library, and the -static option is not used, then this links against the shared version of libasan. The -static-libasan option directs the GCC driver to link libasan statically, without necessarily linking other libraries statically. -static-libtsan When the -fsanitize=thread option is used to link a program, the GCC driver automatically links against libtsan. If libtsan is available as a shared library, and the -static option is not used, then this links against the shared version of libtsan. The -static-libtsan option directs the GCC driver to link libtsan statically, without necessarily linking other libraries statically. -static-liblsan When the -fsanitize=leak option is used to link a program, the GCC driver automatically links against liblsan. If liblsan is available as a shared library, and the -static option is not used, then this links against the shared version of liblsan. The -static-liblsan option directs the GCC driver to link liblsan statically, without necessarily linking other libraries statically. -static-libubsan When the -fsanitize=undefined option is used to link a program, the GCC driver automatically links against libubsan. If libubsan is available as a shared library, and the -static option is not used, then this links against the shared version of libubsan. The -static-libubsan option directs the GCC driver to link libubsan statically, without necessarily linking other libraries statically. -static-libstdc++ When the g++ program is used to link a C++ program, it normally automatically links against libstdc++. If libstdc++ is available as a shared library, and the -static option is not used, then this links against the shared version of libstdc++. That is normally fine. However, it is sometimes useful to freeze the version of libstdc++ used by the program without going all the way to a fully static link. The -static-libstdc++ option directs the g++ driver to link libstdc++ statically, without necessarily linking other libraries statically. -symbolic Bind references to global symbols when building a shared object. Warn about any unresolved references (unless overridden by the link editor option -Xlinker -z -Xlinker defs). Only a few systems support this option. -T script Use script as the linker script. This option is supported by most systems using the GNU linker. On some targets, such as bare-board targets without an operating system, the -T option may be required when linking to avoid references to undefined symbols. -Xlinker option Pass option as an option to the linker. You can use this to supply system-specific linker options that GCC does not recognize. If you want to pass an option that takes a separate argument, you must use -Xlinker twice, once for the option and once for the argument. For example, to pass -assert definitions, you must write -Xlinker -assert -Xlinker definitions. It does not work to write -Xlinker "-assert definitions", because this passes the entire string as a single argument, which is not what the linker expects. When using the GNU linker, it is usually more convenient to pass arguments to linker options using the option=value syntax than as separate arguments. For example, you can specify -Xlinker -Map=output.map rather than -Xlinker -Map -Xlinker output.map. Other linkers may not support this syntax for command-line options. -Wl,option Pass option as an option to the linker. If option contains commas, it is split into multiple options at the commas. You can use this syntax to pass an argument to the option. For example, -Wl,-Map,output.map passes -Map output.map to the linker. When using the GNU linker, you can also get the same effect with -Wl,-Map=output.map. -u symbol Pretend the symbol symbol is undefined, to force linking of library modules to define it. You can use -u multiple times with different symbols to force loading of additional library modules. -z keyword -z is passed directly on to the linker along with the keyword keyword. See the section in the documentation of your linker for permitted values and their meanings. Options for Directory Search These options specify directories to search for header files, for libraries and for parts of the compiler: -I dir -iquote dir -isystem dir -idirafter dir Add the directory dir to the list of directories to be searched for header files during preprocessing. If dir begins with = or $SYSROOT, then the = or $SYSROOT is replaced by the sysroot prefix; see --sysroot and -isysroot. Directories specified with -iquote apply only to the quote form of the directive, "#include "file"". Directories specified with -I, -isystem, or -idirafter apply to lookup for both the "#include "file"" and "#include <file>" directives. You can specify any number or combination of these options on the command line to search for header files in several directories. The lookup order is as follows: 1. For the quote form of the include directive, the directory of the current file is searched first. 2. For the quote form of the include directive, the directories specified by -iquote options are searched in left-to-right order, as they appear on the command line. 3. Directories specified with -I options are scanned in left-to- right order. 4. Directories specified with -isystem options are scanned in left-to-right order. 5. Standard system directories are scanned. 6. Directories specified with -idirafter options are scanned in left-to-right order. You can use -I to override a system header file, substituting your own version, since these directories are searched before the standard system header file directories. However, you should not use this option to add directories that contain vendor-supplied system header files; use -isystem for that. The -isystem and -idirafter options also mark the directory as a system directory, so that it gets the same special treatment that is applied to the standard system directories. If a standard system include directory, or a directory specified with -isystem, is also specified with -I, the -I option is ignored. The directory is still searched but as a system directory at its normal position in the system include chain. This is to ensure that GCC's procedure to fix buggy system headers and the ordering for the "#include_next" directive are not inadvertently changed. If you really need to change the search order for system directories, use the -nostdinc and/or -isystem options. -I- Split the include path. This option has been deprecated. Please use -iquote instead for -I directories before the -I- and remove the -I- option. Any directories specified with -I options before -I- are searched only for headers requested with "#include "file""; they are not searched for "#include <file>". If additional directories are specified with -I options after the -I-, those directories are searched for all #include directives. In addition, -I- inhibits the use of the directory of the current file directory as the first search directory for "#include "file"". There is no way to override this effect of -I-. -iprefix prefix Specify prefix as the prefix for subsequent -iwithprefix options. If the prefix represents a directory, you should include the final /. -iwithprefix dir -iwithprefixbefore dir Append dir to the prefix specified previously with -iprefix, and add the resulting directory to the include search path. -iwithprefixbefore puts it in the same place -I would; -iwithprefix puts it where -idirafter would. -isysroot dir This option is like the --sysroot option, but applies only to header files (except for Darwin targets, where it applies to both header files and libraries). See the --sysroot option for more information. -imultilib dir Use dir as a subdirectory of the directory containing target- specific C++ headers. -nostdinc Do not search the standard system directories for header files. Only the directories explicitly specified with -I, -iquote, -isystem, and/or -idirafter options (and the directory of the current file, if appropriate) are searched. -nostdinc++ Do not search for header files in the C++-specific standard directories, but do still search the other standard directories. (This option is used when building the C++ library.) -iplugindir=dir Set the directory to search for plugins that are passed by -fplugin=name instead of -fplugin=path/name.so. This option is not meant to be used by the user, but only passed by the driver. -Ldir Add directory dir to the list of directories to be searched for -l. -Bprefix This option specifies where to find the executables, libraries, include files, and data files of the compiler itself. The compiler driver program runs one or more of the subprograms cpp, cc1, as and ld. It tries prefix as a prefix for each program it tries to run, both with and without machine/version/ for the corresponding target machine and compiler version. For each subprogram to be run, the compiler driver first tries the -B prefix, if any. If that name is not found, or if -B is not specified, the driver tries two standard prefixes, /usr/lib/gcc/ and /usr/local/lib/gcc/. If neither of those results in a file name that is found, the unmodified program name is searched for using the directories specified in your PATH environment variable. The compiler checks to see if the path provided by -B refers to a directory, and if necessary it adds a directory separator character at the end of the path. -B prefixes that effectively specify directory names also apply to libraries in the linker, because the compiler translates these options into -L options for the linker. They also apply to include files in the preprocessor, because the compiler translates these options into -isystem options for the preprocessor. In this case, the compiler appends include to the prefix. The runtime support file libgcc.a can also be searched for using the -B prefix, if needed. If it is not found there, the two standard prefixes above are tried, and that is all. The file is left out of the link if it is not found by those means. Another way to specify a prefix much like the -B prefix is to use the environment variable GCC_EXEC_PREFIX. As a special kludge, if the path provided by -B is [dir/]stageN/, where N is a number in the range 0 to 9, then it is replaced by [dir/]include. This is to help with boot-strapping the compiler. -no-canonical-prefixes Do not expand any symbolic links, resolve references to /../ or /./, or make the path absolute when generating a relative prefix. --sysroot=dir Use dir as the logical root directory for headers and libraries. For example, if the compiler normally searches for headers in /usr/include and libraries in /usr/lib, it instead searches dir/usr/include and dir/usr/lib. If you use both this option and the -isysroot option, then the --sysroot option applies to libraries, but the -isysroot option applies to header files. The GNU linker (beginning with version 2.16) has the necessary support for this option. If your linker does not support this option, the header file aspect of --sysroot still works, but the library aspect does not. --no-sysroot-suffix For some targets, a suffix is added to the root directory specified with --sysroot, depending on the other options used, so that headers may for example be found in dir/suffix/usr/include instead of dir/usr/include. This option disables the addition of such a suffix. Options for Code Generation Conventions These machine-independent options control the interface conventions used in code generation. Most of them have both positive and negative forms; the negative form of -ffoo is -fno-foo. In the table below, only one of the forms is listed---the one that is not the default. You can figure out the other form by either removing no- or adding it. -fstack-reuse=reuse-level This option controls stack space reuse for user declared local/auto variables and compiler generated temporaries. reuse_level can be all, named_vars, or none. all enables stack reuse for all local variables and temporaries, named_vars enables the reuse only for user defined local variables with names, and none disables stack reuse completely. The default value is all. The option is needed when the program extends the lifetime of a scoped local variable or a compiler generated temporary beyond the end point defined by the language. When a lifetime of a variable ends, and if the variable lives in memory, the optimizing compiler has the freedom to reuse its stack space with other temporaries or scoped local variables whose live range does not overlap with it. Legacy code extending local lifetime is likely to break with the stack reuse optimization. For example, int *p; { int local1; p = &local1; local1 = 10; .... } { int local2; local2 = 20; ... } if (*p == 10) // out of scope use of local1 { } Another example: struct A { A(int k) : i(k), j(k) { } int i; int j; }; A *ap; void foo(const A& ar) { ap = &ar; } void bar() { foo(A(10)); // temp object's lifetime ends when foo returns { A a(20); .... } ap->i+= 10; // ap references out of scope temp whose space // is reused with a. What is the value of ap->i? } The lifetime of a compiler generated temporary is well defined by the C++ standard. When a lifetime of a temporary ends, and if the temporary lives in memory, the optimizing compiler has the freedom to reuse its stack space with other temporaries or scoped local variables whose live range does not overlap with it. However some of the legacy code relies on the behavior of older compilers in which temporaries' stack space is not reused, the aggressive stack reuse can lead to runtime errors. This option is used to control the temporary stack reuse optimization. -fstack-use-cumulative-args This option instructs the compiler to use the "cumulative_args_t"-based stack layout target hooks, "TARGET_FUNCTION_ARG_BOUNDARY_CA" and "TARGET_FUNCTION_ARG_ROUND_BOUNDARY_CA". If a given target does not define these hooks, the default behaviour is to fallback to using the standard non-"_CA" variants instead. Certain targets (such as AArch64 Darwin) require using the more advanced "_CA"-based hooks: For these targets this option should be enabled by default. -ftrapv This option generates traps for signed overflow on addition, subtraction, multiplication operations. The options -ftrapv and -fwrapv override each other, so using -ftrapv -fwrapv on the command-line results in -fwrapv being effective. Note that only active options override, so using -ftrapv -fwrapv -fno-wrapv on the command-line results in -ftrapv being effective. -fwrapv This option instructs the compiler to assume that signed arithmetic overflow of addition, subtraction and multiplication wraps around using twos-complement representation. This flag enables some optimizations and disables others. The options -ftrapv and -fwrapv override each other, so using -ftrapv -fwrapv on the command-line results in -fwrapv being effective. Note that only active options override, so using -ftrapv -fwrapv -fno-wrapv on the command-line results in -ftrapv being effective. -fwrapv-pointer This option instructs the compiler to assume that pointer arithmetic overflow on addition and subtraction wraps around using twos-complement representation. This flag disables some optimizations which assume pointer overflow is invalid. -fstrict-overflow This option implies -fno-wrapv -fno-wrapv-pointer and when negated implies -fwrapv -fwrapv-pointer. -fexceptions Enable exception handling. Generates extra code needed to propagate exceptions. For some targets, this implies GCC generates frame unwind information for all functions, which can produce significant data size overhead, although it does not affect execution. If you do not specify this option, GCC enables it by default for languages like C++ that normally require exception handling, and disables it for languages like C that do not normally require it. However, you may need to enable this option when compiling C code that needs to interoperate properly with exception handlers written in C++. You may also wish to disable this option if you are compiling older C++ programs that don't use exception handling. -fnon-call-exceptions Generate code that allows trapping instructions to throw exceptions. Note that this requires platform-specific runtime support that does not exist everywhere. Moreover, it only allows trapping instructions to throw exceptions, i.e. memory references or floating-point instructions. It does not allow exceptions to be thrown from arbitrary signal handlers such as "SIGALRM". This enables -fexceptions. -foff-stack-trampolines Certain platforms (such as the Apple M1) do not permit an executable stack. Generate calls to "__builtin_nested_func_ptr_created" and "__builtin_nested_func_ptr_deleted" in order to allocate and deallocate trampoline space on the executable heap. Please note that these functions are implemented in libgcc, and will not be compiled in unless you provide --enable-off-stack-trampolines when building gcc. PLEASE NOTE: The trampolines are not guaranteed to be correctly deallocated if you "setjmp", instantiate nested functions, and then "longjmp" back to a state prior to having allocated those nested functions. -fdelete-dead-exceptions Consider that instructions that may throw exceptions but don't otherwise contribute to the execution of the program can be optimized away. This does not affect calls to functions except those with the "pure" or "const" attributes. This option is enabled by default for the Ada and C++ compilers, as permitted by the language specifications. Optimization passes that cause dead exceptions to be removed are enabled independently at different optimization levels. -funwind-tables Similar to -fexceptions, except that it just generates any needed static data, but does not affect the generated code in any other way. You normally do not need to enable this option; instead, a language processor that needs this handling enables it on your behalf. -fasynchronous-unwind-tables Generate unwind table in DWARF format, if supported by target machine. The table is exact at each instruction boundary, so it can be used for stack unwinding from asynchronous events (such as debugger or garbage collector). -fno-gnu-unique On systems with recent GNU assembler and C library, the C++ compiler uses the "STB_GNU_UNIQUE" binding to make sure that definitions of template static data members and static local variables in inline functions are unique even in the presence of "RTLD_LOCAL"; this is necessary to avoid problems with a library used by two different "RTLD_LOCAL" plugins depending on a definition in one of them and therefore disagreeing with the other one about the binding of the symbol. But this causes "dlclose" to be ignored for affected DSOs; if your program relies on reinitialization of a DSO via "dlclose" and "dlopen", you can use -fno-gnu-unique. -fpcc-struct-return Return "short" "struct" and "union" values in memory like longer ones, rather than in registers. This convention is less efficient, but it has the advantage of allowing intercallability between GCC- compiled files and files compiled with other compilers, particularly the Portable C Compiler (pcc). The precise convention for returning structures in memory depends on the target configuration macros. Short structures and unions are those whose size and alignment match that of some integer type. Warning: code compiled with the -fpcc-struct-return switch is not binary compatible with code compiled with the -freg-struct-return switch. Use it to conform to a non-default application binary interface. -freg-struct-return Return "struct" and "union" values in registers when possible. This is more efficient for small structures than -fpcc-struct-return. If you specify neither -fpcc-struct-return nor -freg-struct-return, GCC defaults to whichever convention is standard for the target. If there is no standard convention, GCC defaults to -fpcc-struct-return, except on targets where GCC is the principal compiler. In those cases, we can choose the standard, and we chose the more efficient register return alternative. Warning: code compiled with the -freg-struct-return switch is not binary compatible with code compiled with the -fpcc-struct-return switch. Use it to conform to a non-default application binary interface. -fshort-enums Allocate to an "enum" type only as many bytes as it needs for the declared range of possible values. Specifically, the "enum" type is equivalent to the smallest integer type that has enough room. Warning: the -fshort-enums switch causes GCC to generate code that is not binary compatible with code generated without that switch. Use it to conform to a non-default application binary interface. -fshort-wchar Override the underlying type for "wchar_t" to be "short unsigned int" instead of the default for the target. This option is useful for building programs to run under WINE. Warning: the -fshort-wchar switch causes GCC to generate code that is not binary compatible with code generated without that switch. Use it to conform to a non-default application binary interface. -fcommon In C code, this option controls the placement of global variables defined without an initializer, known as tentative definitions in the C standard. Tentative definitions are distinct from declarations of a variable with the "extern" keyword, which do not allocate storage. The default is -fno-common, which specifies that the compiler places uninitialized global variables in the BSS section of the object file. This inhibits the merging of tentative definitions by the linker so you get a multiple-definition error if the same variable is accidentally defined in more than one compilation unit. The -fcommon places uninitialized global variables in a common block. This allows the linker to resolve all tentative definitions of the same variable in different compilation units to the same object, or to a non-tentative definition. This behavior is inconsistent with C++, and on many targets implies a speed and code size penalty on global variable references. It is mainly useful to enable legacy code to link without errors. -fno-ident Ignore the "#ident" directive. -finhibit-size-directive Don't output a ".size" assembler directive, or anything else that would cause trouble if the function is split in the middle, and the two halves are placed at locations far apart in memory. This option is used when compiling crtstuff.c; you should not need to use it for anything else. -fverbose-asm Put extra commentary information in the generated assembly code to make it more readable. This option is generally only of use to those who actually need to read the generated assembly code (perhaps while debugging the compiler itself). -fno-verbose-asm, the default, causes the extra information to be omitted and is useful when comparing two assembler files. The added comments include: * information on the compiler version and command-line options, * the source code lines associated with the assembly instructions, in the form FILENAME:LINENUMBER:CONTENT OF LINE, * hints on which high-level expressions correspond to the various assembly instruction operands. For example, given this C source file: int test (int n) { int i; int total = 0; for (i = 0; i < n; i++) total += i * i; return total; } compiling to (x86_64) assembly via -S and emitting the result direct to stdout via -o - gcc -S test.c -fverbose-asm -Os -o - gives output similar to this: .file "test.c" # GNU C11 (GCC) version 7.0.0 20160809 (experimental) (x86_64-pc-linux-gnu) [...snip...] # options passed: [...snip...] .text .globl test .type test, @function test: .LFB0: .cfi_startproc # test.c:4: int total = 0; xorl %eax, %eax # <retval> # test.c:6: for (i = 0; i < n; i++) xorl %edx, %edx # i .L2: # test.c:6: for (i = 0; i < n; i++) cmpl %edi, %edx # n, i jge .L5 #, # test.c:7: total += i * i; movl %edx, %ecx # i, tmp92 imull %edx, %ecx # i, tmp92 # test.c:6: for (i = 0; i < n; i++) incl %edx # i # test.c:7: total += i * i; addl %ecx, %eax # tmp92, <retval> jmp .L2 # .L5: # test.c:10: } ret .cfi_endproc .LFE0: .size test, .-test .ident "GCC: (GNU) 7.0.0 20160809 (experimental)" .section .note.GNU-stack,"",@progbits The comments are intended for humans rather than machines and hence the precise format of the comments is subject to change. -frecord-gcc-switches This switch causes the command line used to invoke the compiler to be recorded into the object file that is being created. This switch is only implemented on some targets and the exact format of the recording is target and binary file format dependent, but it usually takes the form of a section containing ASCII text. This switch is related to the -fverbose-asm switch, but that switch only records information in the assembler output file as comments, so it never reaches the object file. See also -grecord-gcc-switches for another way of storing compiler options into the object file. -fpic Generate position-independent code (PIC) suitable for use in a shared library, if supported for the target machine. Such code accesses all constant addresses through a global offset table (GOT). The dynamic loader resolves the GOT entries when the program starts (the dynamic loader is not part of GCC; it is part of the operating system). If the GOT size for the linked executable exceeds a machine-specific maximum size, you get an error message from the linker indicating that -fpic does not work; in that case, recompile with -fPIC instead. (These maximums are 8k on the SPARC, 28k on AArch64 and 32k on the m68k and RS/6000. The x86 has no such limit.) Position-independent code requires special support, and therefore works only on certain machines. For the x86, GCC supports PIC for System V but not for the Sun 386i. Code generated for the IBM RS/6000 is always position-independent. When this flag is set, the macros "__pic__" and "__PIC__" are defined to 1. -fPIC If supported for the target machine, emit position-independent code, suitable for dynamic linking and avoiding any limit on the size of the global offset table. This option makes a difference on AArch64, m68k, PowerPC and SPARC. Position-independent code requires special support, and therefore works only on certain machines. When this flag is set, the macros "__pic__" and "__PIC__" are defined to 2. -fpie -fPIE These options are similar to -fpic and -fPIC, but the generated position-independent code can be only linked into executables. Usually these options are used to compile code that will be linked using the -pie GCC option. -fpie and -fPIE both define the macros "__pie__" and "__PIE__". The macros have the value 1 for -fpie and 2 for -fPIE. -fno-plt Do not use the PLT for external function calls in position- independent code. Instead, load the callee address at call sites from the GOT and branch to it. This leads to more efficient code by eliminating PLT stubs and exposing GOT loads to optimizations. On architectures such as 32-bit x86 where PLT stubs expect the GOT pointer in a specific register, this gives more register allocation freedom to the compiler. Lazy binding requires use of the PLT; with -fno-plt all external symbols are resolved at load time. Alternatively, the function attribute "noplt" can be used to avoid calls through the PLT for specific external functions. In position-dependent code, a few targets also convert calls to functions that are marked to not use the PLT to use the GOT instead. -fno-jump-tables Do not use jump tables for switch statements even where it would be more efficient than other code generation strategies. This option is of use in conjunction with -fpic or -fPIC for building code that forms part of a dynamic linker and cannot reference the address of a jump table. On some targets, jump tables do not require a GOT and this option is not needed. -fno-bit-tests Do not use bit tests for switch statements even where it would be more efficient than other code generation strategies. -ffixed-reg Treat the register named reg as a fixed register; generated code should never refer to it (except perhaps as a stack pointer, frame pointer or in some other fixed role). reg must be the name of a register. The register names accepted are machine-specific and are defined in the "REGISTER_NAMES" macro in the machine description macro file. This flag does not have a negative form, because it specifies a three-way choice. -fcall-used-reg Treat the register named reg as an allocable register that is clobbered by function calls. It may be allocated for temporaries or variables that do not live across a call. Functions compiled this way do not save and restore the register reg. It is an error to use this flag with the frame pointer or stack pointer. Use of this flag for other registers that have fixed pervasive roles in the machine's execution model produces disastrous results. This flag does not have a negative form, because it specifies a three-way choice. -fcall-saved-reg Treat the register named reg as an allocable register saved by functions. It may be allocated even for temporaries or variables that live across a call. Functions compiled this way save and restore the register reg if they use it. It is an error to use this flag with the frame pointer or stack pointer. Use of this flag for other registers that have fixed pervasive roles in the machine's execution model produces disastrous results. A different sort of disaster results from the use of this flag for a register in which function values may be returned. This flag does not have a negative form, because it specifies a three-way choice. -fpack-struct[=n] Without a value specified, pack all structure members together without holes. When a value is specified (which must be a small power of two), pack structure members according to this value, representing the maximum alignment (that is, objects with default alignment requirements larger than this are output potentially unaligned at the next fitting location. Warning: the -fpack-struct switch causes GCC to generate code that is not binary compatible with code generated without that switch. Additionally, it makes the code suboptimal. Use it to conform to a non-default application binary interface. -fleading-underscore This option and its counterpart, -fno-leading-underscore, forcibly change the way C symbols are represented in the object file. One use is to help link with legacy assembly code. Warning: the -fleading-underscore switch causes GCC to generate code that is not binary compatible with code generated without that switch. Use it to conform to a non-default application binary interface. Not all targets provide complete support for this switch. -ftls-model=model Alter the thread-local storage model to be used. The model argument should be one of global-dynamic, local-dynamic, initial- exec or local-exec. Note that the choice is subject to optimization: the compiler may use a more efficient model for symbols not visible outside of the translation unit, or if -fpic is not given on the command line. The default without -fpic is initial-exec; with -fpic the default is global-dynamic. -ftrampolines For targets that normally need trampolines for nested functions, always generate them instead of using descriptors. Otherwise, for targets that do not need them, like for example HP-PA or IA-64, do nothing. A trampoline is a small piece of code that is created at run time on the stack when the address of a nested function is taken, and is used to call the nested function indirectly. Therefore, it requires the stack to be made executable in order for the program to work properly. -fno-trampolines is enabled by default on a language by language basis to let the compiler avoid generating them, if it computes that this is safe, and replace them with descriptors. Descriptors are made up of data only, but the generated code must be prepared to deal with them. As of this writing, -fno-trampolines is enabled by default only for Ada. Moreover, code compiled with -ftrampolines and code compiled with -fno-trampolines are not binary compatible if nested functions are present. This option must therefore be used on a program-wide basis and be manipulated with extreme care. For languages other than Ada, the "-ftrampolines" and "-fno-trampolines" options currently have no effect, and trampolines are always generated on platforms that need them for nested functions. -fvisibility=[default|internal|hidden|protected] Set the default ELF image symbol visibility to the specified option---all symbols are marked with this unless overridden within the code. Using this feature can very substantially improve linking and load times of shared object libraries, produce more optimized code, provide near-perfect API export and prevent symbol clashes. It is strongly recommended that you use this in any shared objects you distribute. Despite the nomenclature, default always means public; i.e., available to be linked against from outside the shared object. protected and internal are pretty useless in real-world usage so the only other commonly used option is hidden. The default if -fvisibility isn't specified is default, i.e., make every symbol public. A good explanation of the benefits offered by ensuring ELF symbols have the correct visibility is given by "How To Write Shared Libraries" by Ulrich Drepper (which can be found at <https://www.akkadia.org/drepper/>)---however a superior solution made possible by this option to marking things hidden when the default is public is to make the default hidden and mark things public. This is the norm with DLLs on Windows and with -fvisibility=hidden and "__attribute__ ((visibility("default")))" instead of "__declspec(dllexport)" you get almost identical semantics with identical syntax. This is a great boon to those working with cross-platform projects. For those adding visibility support to existing code, you may find "#pragma GCC visibility" of use. This works by you enclosing the declarations you wish to set visibility for with (for example) "#pragma GCC visibility push(hidden)" and "#pragma GCC visibility pop". Bear in mind that symbol visibility should be viewed as part of the API interface contract and thus all new code should always specify visibility when it is not the default; i.e., declarations only for use within the local DSO should always be marked explicitly as hidden as so to avoid PLT indirection overheads---making this abundantly clear also aids readability and self-documentation of the code. Note that due to ISO C++ specification requirements, "operator new" and "operator delete" must always be of default visibility. Be aware that headers from outside your project, in particular system headers and headers from any other library you use, may not be expecting to be compiled with visibility other than the default. You may need to explicitly say "#pragma GCC visibility push(default)" before including any such headers. "extern" declarations are not affected by -fvisibility, so a lot of code can be recompiled with -fvisibility=hidden with no modifications. However, this means that calls to "extern" functions with no explicit visibility use the PLT, so it is more effective to use "__attribute ((visibility))" and/or "#pragma GCC visibility" to tell the compiler which "extern" declarations should be treated as hidden. Note that -fvisibility does affect C++ vague linkage entities. This means that, for instance, an exception class that is be thrown between DSOs must be explicitly marked with default visibility so that the type_info nodes are unified between the DSOs. An overview of these techniques, their benefits and how to use them is at <https://gcc.gnu.org/wiki/Visibility>. -fstrict-volatile-bitfields This option should be used if accesses to volatile bit-fields (or other structure fields, although the compiler usually honors those types anyway) should use a single access of the width of the field's type, aligned to a natural alignment if possible. For example, targets with memory-mapped peripheral registers might require all such accesses to be 16 bits wide; with this flag you can declare all peripheral bit-fields as "unsigned short" (assuming short is 16 bits on these targets) to force GCC to use 16-bit accesses instead of, perhaps, a more efficient 32-bit access. If this option is disabled, the compiler uses the most efficient instruction. In the previous example, that might be a 32-bit load instruction, even though that accesses bytes that do not contain any portion of the bit-field, or memory-mapped registers unrelated to the one being updated. In some cases, such as when the "packed" attribute is applied to a structure field, it may not be possible to access the field with a single read or write that is correctly aligned for the target machine. In this case GCC falls back to generating multiple accesses rather than code that will fault or truncate the result at run time. Note: Due to restrictions of the C/C++11 memory model, write accesses are not allowed to touch non bit-field members. It is therefore recommended to define all bits of the field's type as bit-field members. The default value of this option is determined by the application binary interface for the target processor. -fsync-libcalls This option controls whether any out-of-line instance of the "__sync" family of functions may be used to implement the C++11 "__atomic" family of functions. The default value of this option is enabled, thus the only useful form of the option is -fno-sync-libcalls. This option is used in the implementation of the libatomic runtime library. GCC Developer Options This section describes command-line options that are primarily of interest to GCC developers, including options to support compiler testing and investigation of compiler bugs and compile-time performance problems. This includes options that produce debug dumps at various points in the compilation; that print statistics such as memory use and execution time; and that print information about GCC's configuration, such as where it searches for libraries. You should rarely need to use any of these options for ordinary compilation and linking tasks. Many developer options that cause GCC to dump output to a file take an optional =filename suffix. You can specify stdout or - to dump to standard output, and stderr for standard error. If =filename is omitted, a default dump file name is constructed by concatenating the base dump file name, a pass number, phase letter, and pass name. The base dump file name is the name of output file produced by the compiler if explicitly specified and not an executable; otherwise it is the source file name. The pass number is determined by the order passes are registered with the compiler's pass manager. This is generally the same as the order of execution, but passes registered by plugins, target-specific passes, or passes that are otherwise registered late are numbered higher than the pass named final, even if they are executed earlier. The phase letter is one of i (inter- procedural analysis), l (language-specific), r (RTL), or t (tree). The files are created in the directory of the output file. -fcallgraph-info -fcallgraph-info=MARKERS Makes the compiler output callgraph information for the program, on a per-object-file basis. The information is generated in the common VCG format. It can be decorated with additional, per-node and/or per-edge information, if a list of comma-separated markers is additionally specified. When the "su" marker is specified, the callgraph is decorated with stack usage information; it is equivalent to -fstack-usage. When the "da" marker is specified, the callgraph is decorated with information about dynamically allocated objects. When compiling with -flto, no callgraph information is output along with the object file. At LTO link time, -fcallgraph-info may generate multiple callgraph information files next to intermediate LTO output files. -dletters -fdump-rtl-pass -fdump-rtl-pass=filename Says to make debugging dumps during compilation at times specified by letters. This is used for debugging the RTL-based passes of the compiler. Some -dletters switches have different meaning when -E is used for preprocessing. Debug dumps can be enabled with a -fdump-rtl switch or some -d option letters. Here are the possible letters for use in pass and letters, and their meanings: -fdump-rtl-alignments Dump after branch alignments have been computed. -fdump-rtl-asmcons Dump after fixing rtl statements that have unsatisfied in/out constraints. -fdump-rtl-auto_inc_dec Dump after auto-inc-dec discovery. This pass is only run on architectures that have auto inc or auto dec instructions. -fdump-rtl-barriers Dump after cleaning up the barrier instructions. -fdump-rtl-bbpart Dump after partitioning hot and cold basic blocks. -fdump-rtl-bbro Dump after block reordering. -fdump-rtl-btl1 -fdump-rtl-btl2 -fdump-rtl-btl1 and -fdump-rtl-btl2 enable dumping after the two branch target load optimization passes. -fdump-rtl-bypass Dump after jump bypassing and control flow optimizations. -fdump-rtl-combine Dump after the RTL instruction combination pass. -fdump-rtl-compgotos Dump after duplicating the computed gotos. -fdump-rtl-ce1 -fdump-rtl-ce2 -fdump-rtl-ce3 -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3 enable dumping after the three if conversion passes. -fdump-rtl-cprop_hardreg Dump after hard register copy propagation. -fdump-rtl-csa Dump after combining stack adjustments. -fdump-rtl-cse1 -fdump-rtl-cse2 -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping after the two common subexpression elimination passes. -fdump-rtl-dce Dump after the standalone dead code elimination passes. -fdump-rtl-dbr Dump after delayed branch scheduling. -fdump-rtl-dce1 -fdump-rtl-dce2 -fdump-rtl-dce1 and -fdump-rtl-dce2 enable dumping after the two dead store elimination passes. -fdump-rtl-eh Dump after finalization of EH handling code. -fdump-rtl-eh_ranges Dump after conversion of EH handling range regions. -fdump-rtl-expand Dump after RTL generation. -fdump-rtl-fwprop1 -fdump-rtl-fwprop2 -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable dumping after the two forward propagation passes. -fdump-rtl-gcse1 -fdump-rtl-gcse2 -fdump-rtl-gcse1 and -fdump-rtl-gcse2 enable dumping after global common subexpression elimination. -fdump-rtl-init-regs Dump after the initialization of the registers. -fdump-rtl-initvals Dump after the computation of the initial value sets. -fdump-rtl-into_cfglayout Dump after converting to cfglayout mode. -fdump-rtl-ira Dump after iterated register allocation. -fdump-rtl-jump Dump after the second jump optimization. -fdump-rtl-loop2 -fdump-rtl-loop2 enables dumping after the rtl loop optimization passes. -fdump-rtl-mach Dump after performing the machine dependent reorganization pass, if that pass exists. -fdump-rtl-mode_sw Dump after removing redundant mode switches. -fdump-rtl-rnreg Dump after register renumbering. -fdump-rtl-outof_cfglayout Dump after converting from cfglayout mode. -fdump-rtl-peephole2 Dump after the peephole pass. -fdump-rtl-postreload Dump after post-reload optimizations. -fdump-rtl-pro_and_epilogue Dump after generating the function prologues and epilogues. -fdump-rtl-sched1 -fdump-rtl-sched2 -fdump-rtl-sched1 and -fdump-rtl-sched2 enable dumping after the basic block scheduling passes. -fdump-rtl-ree Dump after sign/zero extension elimination. -fdump-rtl-seqabstr Dump after common sequence discovery. -fdump-rtl-shorten Dump after shortening branches. -fdump-rtl-sibling Dump after sibling call optimizations. -fdump-rtl-split1 -fdump-rtl-split2 -fdump-rtl-split3 -fdump-rtl-split4 -fdump-rtl-split5 These options enable dumping after five rounds of instruction splitting. -fdump-rtl-sms Dump after modulo scheduling. This pass is only run on some architectures. -fdump-rtl-stack Dump after conversion from GCC's "flat register file" registers to the x87's stack-like registers. This pass is only run on x86 variants. -fdump-rtl-subreg1 -fdump-rtl-subreg2 -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable dumping after the two subreg expansion passes. -fdump-rtl-unshare Dump after all rtl has been unshared. -fdump-rtl-vartrack Dump after variable tracking. -fdump-rtl-vregs Dump after converting virtual registers to hard registers. -fdump-rtl-web Dump after live range splitting. -fdump-rtl-regclass -fdump-rtl-subregs_of_mode_init -fdump-rtl-subregs_of_mode_finish -fdump-rtl-dfinit -fdump-rtl-dfinish These dumps are defined but always produce empty files. -da -fdump-rtl-all Produce all the dumps listed above. -dA Annotate the assembler output with miscellaneous debugging information. -dD Dump all macro definitions, at the end of preprocessing, in addition to normal output. -dH Produce a core dump whenever an error occurs. -dp Annotate the assembler output with a comment indicating which pattern and alternative is used. The length and cost of each instruction are also printed. -dP Dump the RTL in the assembler output as a comment before each instruction. Also turns on -dp annotation. -dx Just generate RTL for a function instead of compiling it. Usually used with -fdump-rtl-expand. -fdump-debug Dump debugging information generated during the debug generation phase. -fdump-earlydebug Dump debugging information generated during the early debug generation phase. -fdump-noaddr When doing debugging dumps, suppress address output. This makes it more feasible to use diff on debugging dumps for compiler invocations with different compiler binaries and/or different text / bss / data / heap / stack / dso start locations. -freport-bug Collect and dump debug information into a temporary file if an internal compiler error (ICE) occurs. -fdump-unnumbered When doing debugging dumps, suppress instruction numbers and address output. This makes it more feasible to use diff on debugging dumps for compiler invocations with different options, in particular with and without -g. -fdump-unnumbered-links When doing debugging dumps (see -d option above), suppress instruction numbers for the links to the previous and next instructions in a sequence. -fdump-ipa-switch -fdump-ipa-switch-options Control the dumping at various stages of inter-procedural analysis language tree to a file. The file name is generated by appending a switch specific suffix to the source file name, and the file is created in the same directory as the output file. The following dumps are possible: all Enables all inter-procedural analysis dumps. cgraph Dumps information about call-graph optimization, unused function removal, and inlining decisions. inline Dump after function inlining. Additionally, the options -optimized, -missed, -note, and -all can be provided, with the same meaning as for -fopt-info, defaulting to -optimized. For example, -fdump-ipa-inline-optimized-missed will emit information on callsites that were inlined, along with callsites that were not inlined. By default, the dump will contain messages about successful optimizations (equivalent to -optimized) together with low-level details about the analysis. -fdump-lang Dump language-specific information. The file name is made by appending .lang to the source file name. -fdump-lang-all -fdump-lang-switch -fdump-lang-switch-options -fdump-lang-switch-options=filename Control the dumping of language-specific information. The options and filename portions behave as described in the -fdump-tree option. The following switch values are accepted: all Enable all language-specific dumps. class Dump class hierarchy information. Virtual table information is emitted unless 'slim' is specified. This option is applicable to C++ only. module Dump module information. Options lineno (locations), graph (reachability), blocks (clusters), uid (serialization), alias (mergeable), asmname (Elrond), eh (mapper) & vops (macros) may provide additional information. This option is applicable to C++ only. raw Dump the raw internal tree data. This option is applicable to C++ only. -fdump-passes Print on stderr the list of optimization passes that are turned on and off by the current command-line options. -fdump-statistics-option Enable and control dumping of pass statistics in a separate file. The file name is generated by appending a suffix ending in .statistics to the source file name, and the file is created in the same directory as the output file. If the -option form is used, -stats causes counters to be summed over the whole compilation unit while -details dumps every event as the passes generate them. The default with no option is to sum counters for each function compiled. -fdump-tree-all -fdump-tree-switch -fdump-tree-switch-options -fdump-tree-switch-options=filename Control the dumping at various stages of processing the intermediate language tree to a file. If the -options form is used, options is a list of - separated options which control the details of the dump. Not all options are applicable to all dumps; those that are not meaningful are ignored. The following options are available address Print the address of each node. Usually this is not meaningful as it changes according to the environment and source file. Its primary use is for tying up a dump file with a debug environment. asmname If "DECL_ASSEMBLER_NAME" has been set for a given decl, use that in the dump instead of "DECL_NAME". Its primary use is ease of use working backward from mangled names in the assembly file. slim When dumping front-end intermediate representations, inhibit dumping of members of a scope or body of a function merely because that scope has been reached. Only dump such items when they are directly reachable by some other path. When dumping pretty-printed trees, this option inhibits dumping the bodies of control structures. When dumping RTL, print the RTL in slim (condensed) form instead of the default LISP-like representation. raw Print a raw representation of the tree. By default, trees are pretty-printed into a C-like representation. details Enable more detailed dumps (not honored by every dump option). Also include information from the optimization passes. stats Enable dumping various statistics about the pass (not honored by every dump option). blocks Enable showing basic block boundaries (disabled in raw dumps). graph For each of the other indicated dump files (-fdump-rtl-pass), dump a representation of the control flow graph suitable for viewing with GraphViz to file.passid.pass.dot. Each function in the file is pretty-printed as a subgraph, so that GraphViz can render them all in a single plot. This option currently only works for RTL dumps, and the RTL is always dumped in slim form. vops Enable showing virtual operands for every statement. lineno Enable showing line numbers for statements. uid Enable showing the unique ID ("DECL_UID") for each variable. verbose Enable showing the tree dump for each statement. eh Enable showing the EH region number holding each statement. scev Enable showing scalar evolution analysis details. optimized Enable showing optimization information (only available in certain passes). missed Enable showing missed optimization information (only available in certain passes). note Enable other detailed optimization information (only available in certain passes). all Turn on all options, except raw, slim, verbose and lineno. optall Turn on all optimization options, i.e., optimized, missed, and note. To determine what tree dumps are available or find the dump for a pass of interest follow the steps below. 1. Invoke GCC with -fdump-passes and in the stderr output look for a code that corresponds to the pass you are interested in. For example, the codes "tree-evrp", "tree-vrp1", and "tree-vrp2" correspond to the three Value Range Propagation passes. The number at the end distinguishes distinct invocations of the same pass. 2. To enable the creation of the dump file, append the pass code to the -fdump- option prefix and invoke GCC with it. For example, to enable the dump from the Early Value Range Propagation pass, invoke GCC with the -fdump-tree-evrp option. Optionally, you may specify the name of the dump file. If you don't specify one, GCC creates as described below. 3. Find the pass dump in a file whose name is composed of three components separated by a period: the name of the source file GCC was invoked to compile, a numeric suffix indicating the pass number followed by the letter t for tree passes (and the letter r for RTL passes), and finally the pass code. For example, the Early VRP pass dump might be in a file named myfile.c.038t.evrp in the current working directory. Note that the numeric codes are not stable and may change from one version of GCC to another. -fopt-info -fopt-info-options -fopt-info-options=filename Controls optimization dumps from various optimization passes. If the -options form is used, options is a list of - separated option keywords to select the dump details and optimizations. The options can be divided into three groups: 1. options describing what kinds of messages should be emitted, 2. options describing the verbosity of the dump, and 3. options describing which optimizations should be included. The options from each group can be freely mixed as they are non- overlapping. However, in case of any conflicts, the later options override the earlier options on the command line. The following options control which kinds of messages should be emitted: optimized Print information when an optimization is successfully applied. It is up to a pass to decide which information is relevant. For example, the vectorizer passes print the source location of loops which are successfully vectorized. missed Print information about missed optimizations. Individual passes control which information to include in the output. note Print verbose information about optimizations, such as certain transformations, more detailed messages about decisions etc. all Print detailed optimization information. This includes optimized, missed, and note. The following option controls the dump verbosity: internals By default, only "high-level" messages are emitted. This option enables additional, more detailed, messages, which are likely to only be of interest to GCC developers. One or more of the following option keywords can be used to describe a group of optimizations: ipa Enable dumps from all interprocedural optimizations. loop Enable dumps from all loop optimizations. inline Enable dumps from all inlining optimizations. omp Enable dumps from all OMP (Offloading and Multi Processing) optimizations. vec Enable dumps from all vectorization optimizations. optall Enable dumps from all optimizations. This is a superset of the optimization groups listed above. If options is omitted, it defaults to optimized-optall, which means to dump messages about successful optimizations from all the passes, omitting messages that are treated as "internals". If the filename is provided, then the dumps from all the applicable optimizations are concatenated into the filename. Otherwise the dump is output onto stderr. Though multiple -fopt-info options are accepted, only one of them can include a filename. If other filenames are provided then all but the first such option are ignored. Note that the output filename is overwritten in case of multiple translation units. If a combined output from multiple translation units is desired, stderr should be used instead. In the following example, the optimization info is output to stderr: gcc -O3 -fopt-info This example: gcc -O3 -fopt-info-missed=missed.all outputs missed optimization report from all the passes into missed.all, and this one: gcc -O2 -ftree-vectorize -fopt-info-vec-missed prints information about missed optimization opportunities from vectorization passes on stderr. Note that -fopt-info-vec-missed is equivalent to -fopt-info-missed-vec. The order of the optimization group names and message types listed after -fopt-info does not matter. As another example, gcc -O3 -fopt-info-inline-optimized-missed=inline.txt outputs information about missed optimizations as well as optimized locations from all the inlining passes into inline.txt. Finally, consider: gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt Here the two output filenames vec.miss and loop.opt are in conflict since only one output file is allowed. In this case, only the first option takes effect and the subsequent options are ignored. Thus only vec.miss is produced which contains dumps from the vectorizer about missed opportunities. -fsave-optimization-record Write a SRCFILE.opt-record.json.gz file detailing what optimizations were performed, for those optimizations that support -fopt-info. This option is experimental and the format of the data within the compressed JSON file is subject to change. It is roughly equivalent to a machine-readable version of -fopt-info-all, as a collection of messages with source file, line number and column number, with the following additional data for each message: * the execution count of the code being optimized, along with metadata about whether this was from actual profile data, or just an estimate, allowing consumers to prioritize messages by code hotness, * the function name of the code being optimized, where applicable, * the "inlining chain" for the code being optimized, so that when a function is inlined into several different places (which might themselves be inlined), the reader can distinguish between the copies, * objects identifying those parts of the message that refer to expressions, statements or symbol-table nodes, which of these categories they are, and, when available, their source code location, * the GCC pass that emitted the message, and * the location in GCC's own code from which the message was emitted Additionally, some messages are logically nested within other messages, reflecting implementation details of the optimization passes. -fsched-verbose=n On targets that use instruction scheduling, this option controls the amount of debugging output the scheduler prints to the dump files. For n greater than zero, -fsched-verbose outputs the same information as -fdump-rtl-sched1 and -fdump-rtl-sched2. For n greater than one, it also output basic block probabilities, detailed ready list information and unit/insn info. For n greater than two, it includes RTL at abort point, control-flow and regions info. And for n over four, -fsched-verbose also includes dependence info. -fenable-kind-pass -fdisable-kind-pass=range-list This is a set of options that are used to explicitly disable/enable optimization passes. These options are intended for use for debugging GCC. Compiler users should use regular options for enabling/disabling passes instead. -fdisable-ipa-pass Disable IPA pass pass. pass is the pass name. If the same pass is statically invoked in the compiler multiple times, the pass name should be appended with a sequential number starting from 1. -fdisable-rtl-pass -fdisable-rtl-pass=range-list Disable RTL pass pass. pass is the pass name. If the same pass is statically invoked in the compiler multiple times, the pass name should be appended with a sequential number starting from 1. range-list is a comma-separated list of function ranges or assembler names. Each range is a number pair separated by a colon. The range is inclusive in both ends. If the range is trivial, the number pair can be simplified as a single number. If the function's call graph node's uid falls within one of the specified ranges, the pass is disabled for that function. The uid is shown in the function header of a dump file, and the pass names can be dumped by using option -fdump-passes. -fdisable-tree-pass -fdisable-tree-pass=range-list Disable tree pass pass. See -fdisable-rtl for the description of option arguments. -fenable-ipa-pass Enable IPA pass pass. pass is the pass name. If the same pass is statically invoked in the compiler multiple times, the pass name should be appended with a sequential number starting from 1. -fenable-rtl-pass -fenable-rtl-pass=range-list Enable RTL pass pass. See -fdisable-rtl for option argument description and examples. -fenable-tree-pass -fenable-tree-pass=range-list Enable tree pass pass. See -fdisable-rtl for the description of option arguments. Here are some examples showing uses of these options. # disable ccp1 for all functions -fdisable-tree-ccp1 # disable complete unroll for function whose cgraph node uid is 1 -fenable-tree-cunroll=1 # disable gcse2 for functions at the following ranges [1,1], # [300,400], and [400,1000] # disable gcse2 for functions foo and foo2 -fdisable-rtl-gcse2=foo,foo2 # disable early inlining -fdisable-tree-einline # disable ipa inlining -fdisable-ipa-inline # enable tree full unroll -fenable-tree-unroll -fchecking -fchecking=n Enable internal consistency checking. The default depends on the compiler configuration. -fchecking=2 enables further internal consistency checking that might affect code generation. -frandom-seed=string This option provides a seed that GCC uses in place of random numbers in generating certain symbol names that have to be different in every compiled file. It is also used to place unique stamps in coverage data files and the object files that produce them. You can use the -frandom-seed option to produce reproducibly identical object files. The string can either be a number (decimal, octal or hex) or an arbitrary string (in which case it's converted to a number by computing CRC32). The string should be different for every file you compile. -save-temps Store the usual "temporary" intermediate files permanently; name them as auxiliary output files, as specified described under -dumpbase and -dumpdir. When used in combination with the -x command-line option, -save-temps is sensible enough to avoid overwriting an input source file with the same extension as an intermediate file. The corresponding intermediate file may be obtained by renaming the source file before using -save-temps. -save-temps=cwd Equivalent to -save-temps -dumpdir ./. -save-temps=obj Equivalent to -save-temps -dumpdir outdir/, where outdir/ is the directory of the output file specified after the -o option, including any directory separators. If the -o option is not used, the -save-temps=obj switch behaves like -save-temps=cwd. -time[=file] Report the CPU time taken by each subprocess in the compilation sequence. For C source files, this is the compiler proper and assembler (plus the linker if linking is done). Without the specification of an output file, the output looks like this: # cc1 0.12 0.01 # as 0.00 0.01 The first number on each line is the "user time", that is time spent executing the program itself. The second number is "system time", time spent executing operating system routines on behalf of the program. Both numbers are in seconds. With the specification of an output file, the output is appended to the named file, and it looks like this: 0.12 0.01 cc1 <options> 0.00 0.01 as <options> The "user time" and the "system time" are moved before the program name, and the options passed to the program are displayed, so that one can later tell what file was being compiled, and with which options. -fdump-final-insns[=file] Dump the final internal representation (RTL) to file. If the optional argument is omitted (or if file is "."), the name of the dump file is determined by appending ".gkd" to the dump base name, see -dumpbase. -fcompare-debug[=opts] If no error occurs during compilation, run the compiler a second time, adding opts and -fcompare-debug-second to the arguments passed to the second compilation. Dump the final internal representation in both compilations, and print an error if they differ. If the equal sign is omitted, the default -gtoggle is used. The environment variable GCC_COMPARE_DEBUG, if defined, non-empty and nonzero, implicitly enables -fcompare-debug. If GCC_COMPARE_DEBUG is defined to a string starting with a dash, then it is used for opts, otherwise the default -gtoggle is used. -fcompare-debug=, with the equal sign but without opts, is equivalent to -fno-compare-debug, which disables the dumping of the final representation and the second compilation, preventing even GCC_COMPARE_DEBUG from taking effect. To verify full coverage during -fcompare-debug testing, set GCC_COMPARE_DEBUG to say -fcompare-debug-not-overridden, which GCC rejects as an invalid option in any actual compilation (rather than preprocessing, assembly or linking). To get just a warning, setting GCC_COMPARE_DEBUG to -w%n-fcompare-debug not overridden will do. -fcompare-debug-second This option is implicitly passed to the compiler for the second compilation requested by -fcompare-debug, along with options to silence warnings, and omitting other options that would cause the compiler to produce output to files or to standard output as a side effect. Dump files and preserved temporary files are renamed so as to contain the ".gk" additional extension during the second compilation, to avoid overwriting those generated by the first. When this option is passed to the compiler driver, it causes the first compilation to be skipped, which makes it useful for little other than debugging the compiler proper. -gtoggle Turn off generation of debug info, if leaving out this option generates it, or turn it on at level 2 otherwise. The position of this argument in the command line does not matter; it takes effect after all other options are processed, and it does so only once, no matter how many times it is given. This is mainly intended to be used with -fcompare-debug. -fvar-tracking-assignments-toggle Toggle -fvar-tracking-assignments, in the same way that -gtoggle toggles -g. -Q Makes the compiler print out each function name as it is compiled, and print some statistics about each pass when it finishes. -ftime-report Makes the compiler print some statistics about the time consumed by each pass when it finishes. -ftime-report-details Record the time consumed by infrastructure parts separately for each pass. -fira-verbose=n Control the verbosity of the dump file for the integrated register allocator. The default value is 5. If the value n is greater or equal to 10, the dump output is sent to stderr using the same format as n minus 10. -flto-report Prints a report with internal details on the workings of the link- time optimizer. The contents of this report vary from version to version. It is meant to be useful to GCC developers when processing object files in LTO mode (via -flto). Disabled by default. -flto-report-wpa Like -flto-report, but only print for the WPA phase of link-time optimization. -fmem-report Makes the compiler print some statistics about permanent memory allocation when it finishes. -fmem-report-wpa Makes the compiler print some statistics about permanent memory allocation for the WPA phase only. -fpre-ipa-mem-report -fpost-ipa-mem-report Makes the compiler print some statistics about permanent memory allocation before or after interprocedural optimization. -fmultiflags This option enables multilib-aware "TFLAGS" to be used to build target libraries with options different from those the compiler is configured to use by default, through the use of specs Like "TFLAGS", this allows the target libraries to be built for portable baseline environments, while the compiler defaults to more demanding ones. That's useful because users can easily override the defaults the compiler is configured to use to build their own programs, if the defaults are not ideal for their target environment, whereas rebuilding the runtime libraries is usually not as easy or desirable. Unlike "TFLAGS", the use of specs enables different flags to be selected for different multilibs. The way to accomplish that is to build with make TFLAGS=-fmultiflags, after configuring --with-specs=%{fmultiflags:...}. This option is discarded by the driver once it's done processing driver self spec. It is also useful to check that "TFLAGS" are being used to build all target libraries, by configuring a non-bootstrap compiler --with-specs='%{!fmultiflags:%emissing TFLAGS}' and building the compiler and target libraries. -fprofile-report Makes the compiler print some statistics about consistency of the (estimated) profile and effect of individual passes. -fstack-usage Makes the compiler output stack usage information for the program, on a per-function basis. The filename for the dump is made by appending .su to the auxname. auxname is generated from the name of the output file, if explicitly specified and it is not an executable, otherwise it is the basename of the source file. An entry is made up of three fields: * The name of the function. * A number of bytes. * One or more qualifiers: "static", "dynamic", "bounded". The qualifier "static" means that the function manipulates the stack statically: a fixed number of bytes are allocated for the frame on function entry and released on function exit; no stack adjustments are otherwise made in the function. The second field is this fixed number of bytes. The qualifier "dynamic" means that the function manipulates the stack dynamically: in addition to the static allocation described above, stack adjustments are made in the body of the function, for example to push/pop arguments around function calls. If the qualifier "bounded" is also present, the amount of these adjustments is bounded at compile time and the second field is an upper bound of the total amount of stack used by the function. If it is not present, the amount of these adjustments is not bounded at compile time and the second field only represents the bounded part. -fstats Emit statistics about front-end processing at the end of the compilation. This option is supported only by the C++ front end, and the information is generally only useful to the G++ development team. -fdbg-cnt-list Print the name and the counter upper bound for all debug counters. -fdbg-cnt=counter-value-list Set the internal debug counter lower and upper bound. counter- value-list is a comma-separated list of name:lower_bound1-upper_bound1 [:lower_bound2-upper_bound2...] tuples which sets the name of the counter and list of closed intervals. The lower_bound is optional and is zero initialized if not set. For example, with -fdbg-cnt=dce:2-4:10-11,tail_call:10, "dbg_cnt(dce)" returns true only for second, third, fourth, tenth and eleventh invocation. For "dbg_cnt(tail_call)" true is returned for first 10 invocations. -print-file-name=library Print the full absolute name of the library file library that would be used when linking---and don't do anything else. With this option, GCC does not compile or link anything; it just prints the file name. -print-multi-directory Print the directory name corresponding to the multilib selected by any other switches present in the command line. This directory is supposed to exist in GCC_EXEC_PREFIX. -print-multi-lib Print the mapping from multilib directory names to compiler switches that enable them. The directory name is separated from the switches by ;, and each switch starts with an @ instead of the -, without spaces between multiple switches. This is supposed to ease shell processing. -print-multi-os-directory Print the path to OS libraries for the selected multilib, relative to some lib subdirectory. If OS libraries are present in the lib subdirectory and no multilibs are used, this is usually just ., if OS libraries are present in libsuffix sibling directories this prints e.g. ../lib64, ../lib or ../lib32, or if OS libraries are present in lib/subdir subdirectories it prints e.g. amd64, sparcv9 or ev6. -print-multiarch Print the path to OS libraries for the selected multiarch, relative to some lib subdirectory. -print-prog-name=program Like -print-file-name, but searches for a program such as cpp. -print-libgcc-file-name Same as -print-file-name=libgcc.a. This is useful when you use -nostdlib or -nodefaultlibs but you do want to link with libgcc.a. You can do: gcc -nostdlib <files>... `gcc -print-libgcc-file-name` -print-search-dirs Print the name of the configured installation directory and a list of program and library directories gcc searches---and don't do anything else. This is useful when gcc prints the error message installation problem, cannot exec cpp0: No such file or directory. To resolve this you either need to put cpp0 and the other compiler components where gcc expects to find them, or you can set the environment variable GCC_EXEC_PREFIX to the directory where you installed them. Don't forget the trailing /. -print-sysroot Print the target sysroot directory that is used during compilation. This is the target sysroot specified either at configure time or using the --sysroot option, possibly with an extra suffix that depends on compilation options. If no target sysroot is specified, the option prints nothing. -print-sysroot-headers-suffix Print the suffix added to the target sysroot when searching for headers, or give an error if the compiler is not configured with such a suffix---and don't do anything else. -dumpmachine Print the compiler's target machine (for example, i686-pc-linux-gnu)---and don't do anything else. -dumpversion Print the compiler version (for example, 3.0, 6.3.0 or 7)---and don't do anything else. This is the compiler version used in filesystem paths and specs. Depending on how the compiler has been configured it can be just a single number (major version), two numbers separated by a dot (major and minor version) or three numbers separated by dots (major, minor and patchlevel version). -dumpfullversion Print the full compiler version---and don't do anything else. The output is always three numbers separated by dots, major, minor and patchlevel version. -dumpspecs Print the compiler's built-in specs---and don't do anything else. (This is used when GCC itself is being built.) Machine-Dependent Options Each target machine supported by GCC can have its own options---for example, to allow you to compile for a particular processor variant or ABI, or to control optimizations specific to that machine. By convention, the names of machine-specific options start with -m. Some configurations of the compiler also support additional target- specific options, usually for compatibility with other compilers on the same platform. AArch64 Options These options are defined for AArch64 implementations: -mabi=name Generate code for the specified data model. Permissible values are ilp32 for SysV-like data model where int, long int and pointers are 32 bits, and lp64 for SysV-like data model where int is 32 bits, but long int and pointers are 64 bits. The default depends on the specific target configuration. Note that the LP64 and ILP32 ABIs are not link-compatible; you must compile your entire program with the same ABI, and link with a compatible set of libraries. -mbig-endian Generate big-endian code. This is the default when GCC is configured for an aarch64_be-*-* target. -mgeneral-regs-only Generate code which uses only the general-purpose registers. This will prevent the compiler from using floating-point and Advanced SIMD registers but will not impose any restrictions on the assembler. -mlittle-endian Generate little-endian code. This is the default when GCC is configured for an aarch64-*-* but not an aarch64_be-*-* target. -mcmodel=tiny Generate code for the tiny code model. The program and its statically defined symbols must be within 1MB of each other. Programs can be statically or dynamically linked. -mcmodel=small Generate code for the small code model. The program and its statically defined symbols must be within 4GB of each other. Programs can be statically or dynamically linked. This is the default code model. -mcmodel=large Generate code for the large code model. This makes no assumptions about addresses and sizes of sections. Programs can be statically linked only. The -mcmodel=large option is incompatible with -mabi=ilp32, -fpic and -fPIC. -mstrict-align -mno-strict-align Avoid or allow generating memory accesses that may not be aligned on a natural object boundary as described in the architecture specification. -momit-leaf-frame-pointer -mno-omit-leaf-frame-pointer Omit or keep the frame pointer in leaf functions. The former behavior is the default. -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset Generate stack protection code using canary at guard. Supported locations are global for a global canary or sysreg for a canary in an appropriate system register. With the latter choice the options -mstack-protector-guard-reg=reg and -mstack-protector-guard-offset=offset furthermore specify which system register to use as base register for reading the canary, and from what offset from that base register. There is no default register or offset as this is entirely for use within the Linux kernel. -mtls-dialect=desc Use TLS descriptors as the thread-local storage mechanism for dynamic accesses of TLS variables. This is the default. -mtls-dialect=traditional Use traditional TLS as the thread-local storage mechanism for dynamic accesses of TLS variables. -mtls-size=size Specify bit size of immediate TLS offsets. Valid values are 12, 24, 32, 48. This option requires binutils 2.26 or newer. -mfix-cortex-a53-835769 -mno-fix-cortex-a53-835769 Enable or disable the workaround for the ARM Cortex-A53 erratum number 835769. This involves inserting a NOP instruction between memory instructions and 64-bit integer multiply-accumulate instructions. -mfix-cortex-a53-843419 -mno-fix-cortex-a53-843419 Enable or disable the workaround for the ARM Cortex-A53 erratum number 843419. This erratum workaround is made at link time and this will only pass the corresponding flag to the linker. -mlow-precision-recip-sqrt -mno-low-precision-recip-sqrt Enable or disable the reciprocal square root approximation. This option only has an effect if -ffast-math or -funsafe-math-optimizations is used as well. Enabling this reduces precision of reciprocal square root results to about 16 bits for single precision and to 32 bits for double precision. -mlow-precision-sqrt -mno-low-precision-sqrt Enable or disable the square root approximation. This option only has an effect if -ffast-math or -funsafe-math-optimizations is used as well. Enabling this reduces precision of square root results to about 16 bits for single precision and to 32 bits for double precision. If enabled, it implies -mlow-precision-recip-sqrt. -mlow-precision-div -mno-low-precision-div Enable or disable the division approximation. This option only has an effect if -ffast-math or -funsafe-math-optimizations is used as well. Enabling this reduces precision of division results to about 16 bits for single precision and to 32 bits for double precision. -mtrack-speculation -mno-track-speculation Enable or disable generation of additional code to track speculative execution through conditional branches. The tracking state can then be used by the compiler when expanding calls to "__builtin_speculation_safe_copy" to permit a more efficient code sequence to be generated. -moutline-atomics -mno-outline-atomics Enable or disable calls to out-of-line helpers to implement atomic operations. These helpers will, at runtime, determine if the LSE instructions from ARMv8.1-A can be used; if not, they will use the load/store-exclusive instructions that are present in the base ARMv8.0 ISA. This option is only applicable when compiling for the base ARMv8.0 instruction set. If using a later revision, e.g. -march=armv8.1-a or -march=armv8-a+lse, the ARMv8.1-Atomics instructions will be used directly. The same applies when using -mcpu= when the selected cpu supports the lse feature. This option is on by default. -march=name Specify the name of the target architecture and, optionally, one or more feature modifiers. This option has the form -march=arch{+[no]feature}*. The table below summarizes the permissible values for arch and the features that they enable by default: arch value : Architecture : Includes by default armv8-a : Armv8-A : +fp, +simd armv8.1-a : Armv8.1-A : armv8-a, +crc, +lse, +rdma armv8.2-a : Armv8.2-A : armv8.1-a armv8.3-a : Armv8.3-A : armv8.2-a, +pauth armv8.4-a : Armv8.4-A : armv8.3-a, +flagm, +fp16fml, +dotprod armv8.5-a : Armv8.5-A : armv8.4-a, +sb, +ssbs, +predres armv8.6-a : Armv8.6-A : armv8.5-a, +bf16, +i8mm armv8.7-a : Armv8.7-A : armv8.6-a, +ls64 armv8.8-a : Armv8.8-a : armv8.7-a, +mops armv9-a : Armv9-A : armv8.5-a, +sve, +sve2 armv9.1-a : Armv9.1-A : armv9-a, +bf16, +i8mm armv9.2-a : Armv9.2-A : armv9.1-a, +ls64 armv9.3-a : Armv9.3-A : armv9.2-a, +mops armv8-r : Armv8-R : armv8-r The value native is available on native AArch64 GNU/Linux and causes the compiler to pick the architecture of the host system. This option has no effect if the compiler is unable to recognize the architecture of the host system, The permissible values for feature are listed in the sub-section on aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers. Where conflicting feature modifiers are specified, the right-most feature is used. GCC uses name to determine what kind of instructions it can emit when generating assembly code. If -march is specified without either of -mtune or -mcpu also being specified, the code is tuned to perform well across a range of target processors implementing the target architecture. -mtune=name Specify the name of the target processor for which GCC should tune the performance of the code. Permissible values for this option are: generic, cortex-a35, cortex-a53, cortex-a55, cortex-a57, cortex-a72, cortex-a73, cortex-a75, cortex-a76, cortex-a76ae, cortex-a77, cortex-a65, cortex-a65ae, cortex-a34, cortex-a78, cortex-a78ae, cortex-a78c, ares, exynos-m1, emag, falkor, neoverse-512tvb, neoverse-e1, neoverse-n1, neoverse-n2, neoverse-v1, neoverse-v2, qdf24xx, saphira, phecda, xgene1, vulcan, octeontx, octeontx81, octeontx83, octeontx2, octeontx2t98, octeontx2t96 octeontx2t93, octeontx2f95, octeontx2f95n, octeontx2f95mm, a64fx, thunderx, thunderxt88, thunderxt88p1, thunderxt81, tsv110, thunderxt83, thunderx2t99, thunderx3t110, zeus, cortex-a57.cortex-a53, cortex-a72.cortex-a53, cortex-a73.cortex-a35, cortex-a73.cortex-a53, cortex-a75.cortex-a55, cortex-a76.cortex-a55, cortex-r82, cortex-x1, cortex-x1c, cortex-x2, cortex-x3, cortex-a510, cortex-a710, cortex-a715, ampere1, ampere1a, and native. The values cortex-a57.cortex-a53, cortex-a72.cortex-a53, cortex-a73.cortex-a35, cortex-a73.cortex-a53, cortex-a75.cortex-a55, cortex-a76.cortex-a55 specify that GCC should tune for a big.LITTLE system. The value neoverse-512tvb specifies that GCC should tune for Neoverse cores that (a) implement SVE and (b) have a total vector bandwidth of 512 bits per cycle. In other words, the option tells GCC to tune for Neoverse cores that can execute 4 128-bit Advanced SIMD arithmetic instructions a cycle and that can execute an equivalent number of SVE arithmetic instructions per cycle (2 for 256-bit SVE, 4 for 128-bit SVE). This is more general than tuning for a specific core like Neoverse V1 but is more specific than the default tuning described below. Additionally on native AArch64 GNU/Linux systems the value native tunes performance to the host system. This option has no effect if the compiler is unable to recognize the processor of the host system. Where none of -mtune=, -mcpu= or -march= are specified, the code is tuned to perform well across a range of target processors. This option cannot be suffixed by feature modifiers. -mcpu=name Specify the name of the target processor, optionally suffixed by one or more feature modifiers. This option has the form -mcpu=cpu{+[no]feature}*, where the permissible values for cpu are the same as those available for -mtune. The permissible values for feature are documented in the sub-section on aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers. Where conflicting feature modifiers are specified, the right-most feature is used. GCC uses name to determine what kind of instructions it can emit when generating assembly code (as if by -march) and to determine the target processor for which to tune for performance (as if by -mtune). Where this option is used in conjunction with -march or -mtune, those options take precedence over the appropriate part of this option. -mcpu=neoverse-512tvb is special in that it does not refer to a specific core, but instead refers to all Neoverse cores that (a) implement SVE and (b) have a total vector bandwidth of 512 bits a cycle. Unless overridden by -march, -mcpu=neoverse-512tvb generates code that can run on a Neoverse V1 core, since Neoverse V1 is the first Neoverse core with these properties. Unless overridden by -mtune, -mcpu=neoverse-512tvb tunes code in the same way as for -mtune=neoverse-512tvb. -moverride=string Override tuning decisions made by the back-end in response to a -mtune= switch. The syntax, semantics, and accepted values for string in this option are not guaranteed to be consistent across releases. This option is only intended to be useful when developing GCC. -mverbose-cost-dump Enable verbose cost model dumping in the debug dump files. This option is provided for use in debugging the compiler. -mpc-relative-literal-loads -mno-pc-relative-literal-loads Enable or disable PC-relative literal loads. With this option literal pools are accessed using a single instruction and emitted after each function. This limits the maximum size of functions to 1MB. This is enabled by default for -mcmodel=tiny. -msign-return-address=scope Select the function scope on which return address signing will be applied. Permissible values are none, which disables return address signing, non-leaf, which enables pointer signing for functions which are not leaf functions, and all, which enables pointer signing for all functions. The default value is none. This option has been deprecated by -mbranch-protection. -mbranch-protection=none|standard|pac-ret[+leaf+b-key]|bti Select the branch protection features to use. none is the default and turns off all types of branch protection. standard turns on all types of branch protection features. If a feature has additional tuning options, then standard sets it to its standard level. pac-ret[+leaf] turns on return address signing to its standard level: signing functions that save the return address to memory (non-leaf functions will practically always do this) using the a-key. The optional argument leaf can be used to extend the signing to include leaf functions. The optional argument b-key can be used to sign the functions with the B-key instead of the A-key. bti turns on branch target identification mechanism. -mharden-sls=opts Enable compiler hardening against straight line speculation (SLS). opts is a comma-separated list of the following options: retbr blr In addition, -mharden-sls=all enables all SLS hardening while -mharden-sls=none disables all SLS hardening. -msve-vector-bits=bits Specify the number of bits in an SVE vector register. This option only has an effect when SVE is enabled. GCC supports two forms of SVE code generation: "vector-length agnostic" output that works with any size of vector register and "vector-length specific" output that allows GCC to make assumptions about the vector length when it is useful for optimization reasons. The possible values of bits are: scalable, 128, 256, 512, 1024 and 2048. Specifying scalable selects vector-length agnostic output. At present -msve-vector-bits=128 also generates vector-length agnostic output for big-endian targets. All other values generate vector-length specific code. The behavior of these values may change in future releases and no value except scalable should be relied on for producing code that is portable across different hardware SVE vector lengths. The default is -msve-vector-bits=scalable, which produces vector- length agnostic code. -march and -mcpu Feature Modifiers Feature modifiers used with -march and -mcpu can be any of the following and their inverses nofeature: crc Enable CRC extension. This is on by default for -march=armv8.1-a. crypto Enable Crypto extension. This also enables Advanced SIMD and floating-point instructions. fp Enable floating-point instructions. This is on by default for all possible values for options -march and -mcpu. simd Enable Advanced SIMD instructions. This also enables floating- point instructions. This is on by default for all possible values for options -march and -mcpu. sve Enable Scalable Vector Extension instructions. This also enables Advanced SIMD and floating-point instructions. lse Enable Large System Extension instructions. This is on by default for -march=armv8.1-a. rdma Enable Round Double Multiply Accumulate instructions. This is on by default for -march=armv8.1-a. fp16 Enable FP16 extension. This also enables floating-point instructions. fp16fml Enable FP16 fmla extension. This also enables FP16 extensions and floating-point instructions. This option is enabled by default for -march=armv8.4-a. Use of this option with architectures prior to Armv8.2-A is not supported. rcpc Enable the RCpc extension. This enables the use of the LDAPR instructions for load-acquire atomic semantics, and passes it on to the assembler, enabling inline asm statements to use instructions from the RCpc extension. dotprod Enable the Dot Product extension. This also enables Advanced SIMD instructions. aes Enable the Armv8-a aes and pmull crypto extension. This also enables Advanced SIMD instructions. sha2 Enable the Armv8-a sha2 crypto extension. This also enables Advanced SIMD instructions. sha3 Enable the sha512 and sha3 crypto extension. This also enables Advanced SIMD instructions. Use of this option with architectures prior to Armv8.2-A is not supported. sm4 Enable the sm3 and sm4 crypto extension. This also enables Advanced SIMD instructions. Use of this option with architectures prior to Armv8.2-A is not supported. profile Enable the Statistical Profiling extension. This option is only to enable the extension at the assembler level and does not affect code generation. rng Enable the Armv8.5-a Random Number instructions. This option is only to enable the extension at the assembler level and does not affect code generation. memtag Enable the Armv8.5-a Memory Tagging Extensions. Use of this option with architectures prior to Armv8.5-A is not supported. sb Enable the Armv8-a Speculation Barrier instruction. This option is only to enable the extension at the assembler level and does not affect code generation. This option is enabled by default for -march=armv8.5-a. ssbs Enable the Armv8-a Speculative Store Bypass Safe instruction. This option is only to enable the extension at the assembler level and does not affect code generation. This option is enabled by default for -march=armv8.5-a. predres Enable the Armv8-a Execution and Data Prediction Restriction instructions. This option is only to enable the extension at the assembler level and does not affect code generation. This option is enabled by default for -march=armv8.5-a. sve2 Enable the Armv8-a Scalable Vector Extension 2. This also enables SVE instructions. sve2-bitperm Enable SVE2 bitperm instructions. This also enables SVE2 instructions. sve2-sm4 Enable SVE2 sm4 instructions. This also enables SVE2 instructions. sve2-aes Enable SVE2 aes instructions. This also enables SVE2 instructions. sve2-sha3 Enable SVE2 sha3 instructions. This also enables SVE2 instructions. tme Enable the Transactional Memory Extension. i8mm Enable 8-bit Integer Matrix Multiply instructions. This also enables Advanced SIMD and floating-point instructions. This option is enabled by default for -march=armv8.6-a. Use of this option with architectures prior to Armv8.2-A is not supported. f32mm Enable 32-bit Floating point Matrix Multiply instructions. This also enables SVE instructions. Use of this option with architectures prior to Armv8.2-A is not supported. f64mm Enable 64-bit Floating point Matrix Multiply instructions. This also enables SVE instructions. Use of this option with architectures prior to Armv8.2-A is not supported. bf16 Enable brain half-precision floating-point instructions. This also enables Advanced SIMD and floating-point instructions. This option is enabled by default for -march=armv8.6-a. Use of this option with architectures prior to Armv8.2-A is not supported. ls64 Enable the 64-byte atomic load and store instructions for accelerators. This option is enabled by default for -march=armv8.7-a. mops Enable the instructions to accelerate memory operations like "memcpy", "memmove", "memset". This option is enabled by default for -march=armv8.8-a flagm Enable the Flag Manipulation instructions Extension. pauth Enable the Pointer Authentication Extension. cssc Enable the Common Short Sequence Compression instructions. Feature crypto implies aes, sha2, and simd, which implies fp. Conversely, nofp implies nosimd, which implies nocrypto, noaes and nosha2. Adapteva Epiphany Options These -m options are defined for Adapteva Epiphany: -mhalf-reg-file Don't allocate any register in the range "r32"..."r63". That allows code to run on hardware variants that lack these registers. -mprefer-short-insn-regs Preferentially allocate registers that allow short instruction generation. This can result in increased instruction count, so this may either reduce or increase overall code size. -mbranch-cost=num Set the cost of branches to roughly num "simple" instructions. This cost is only a heuristic and is not guaranteed to produce consistent results across releases. -mcmove Enable the generation of conditional moves. -mnops=num Emit num NOPs before every other generated instruction. -mno-soft-cmpsf For single-precision floating-point comparisons, emit an "fsub" instruction and test the flags. This is faster than a software comparison, but can get incorrect results in the presence of NaNs, or when two different small numbers are compared such that their difference is calculated as zero. The default is -msoft-cmpsf, which uses slower, but IEEE-compliant, software comparisons. -mstack-offset=num Set the offset between the top of the stack and the stack pointer. E.g., a value of 8 means that the eight bytes in the range "sp+0...sp+7" can be used by leaf functions without stack allocation. Values other than 8 or 16 are untested and unlikely to work. Note also that this option changes the ABI; compiling a program with a different stack offset than the libraries have been compiled with generally does not work. This option can be useful if you want to evaluate if a different stack offset would give you better code, but to actually use a different stack offset to build working programs, it is recommended to configure the toolchain with the appropriate --with-stack-offset=num option. -mno-round-nearest Make the scheduler assume that the rounding mode has been set to truncating. The default is -mround-nearest. -mlong-calls If not otherwise specified by an attribute, assume all calls might be beyond the offset range of the "b" / "bl" instructions, and therefore load the function address into a register before performing a (otherwise direct) call. This is the default. -mshort-calls If not otherwise specified by an attribute, assume all direct calls are in the range of the "b" / "bl" instructions, so use these instructions for direct calls. The default is -mlong-calls. -msmall16 Assume addresses can be loaded as 16-bit unsigned values. This does not apply to function addresses for which -mlong-calls semantics are in effect. -mfp-mode=mode Set the prevailing mode of the floating-point unit. This determines the floating-point mode that is provided and expected at function call and return time. Making this mode match the mode you predominantly need at function start can make your programs smaller and faster by avoiding unnecessary mode switches. mode can be set to one the following values: caller Any mode at function entry is valid, and retained or restored when the function returns, and when it calls other functions. This mode is useful for compiling libraries or other compilation units you might want to incorporate into different programs with different prevailing FPU modes, and the convenience of being able to use a single object file outweighs the size and speed overhead for any extra mode switching that might be needed, compared with what would be needed with a more specific choice of prevailing FPU mode. truncate This is the mode used for floating-point calculations with truncating (i.e. round towards zero) rounding mode. That includes conversion from floating point to integer. round-nearest This is the mode used for floating-point calculations with round-to-nearest-or-even rounding mode. int This is the mode used to perform integer calculations in the FPU, e.g. integer multiply, or integer multiply-and- accumulate. The default is -mfp-mode=caller -mno-split-lohi -mno-postinc -mno-postmodify Code generation tweaks that disable, respectively, splitting of 32-bit loads, generation of post-increment addresses, and generation of post-modify addresses. The defaults are msplit-lohi, -mpost-inc, and -mpost-modify. -mnovect-double Change the preferred SIMD mode to SImode. The default is -mvect-double, which uses DImode as preferred SIMD mode. -max-vect-align=num The maximum alignment for SIMD vector mode types. num may be 4 or 8. The default is 8. Note that this is an ABI change, even though many library function interfaces are unaffected if they don't use SIMD vector modes in places that affect size and/or alignment of relevant types. -msplit-vecmove-early Split vector moves into single word moves before reload. In theory this can give better register allocation, but so far the reverse seems to be generally the case. -m1reg-reg Specify a register to hold the constant -1, which makes loading small negative constants and certain bitmasks faster. Allowable values for reg are r43 and r63, which specify use of that register as a fixed register, and none, which means that no register is used for this purpose. The default is -m1reg-none. AMD GCN Options These options are defined specifically for the AMD GCN port. -march=gpu -mtune=gpu Set architecture type or tuning for gpu. Supported values for gpu are fiji Compile for GCN3 Fiji devices (gfx803). gfx900 Compile for GCN5 Vega 10 devices (gfx900). gfx906 Compile for GCN5 Vega 20 devices (gfx906). gfx908 Compile for CDNA1 Instinct MI100 series devices (gfx908). gfx90a Compile for CDNA2 Instinct MI200 series devices (gfx90a). -msram-ecc=on -msram-ecc=off -msram-ecc=any Compile binaries suitable for devices with the SRAM-ECC feature enabled, disabled, or either mode. This feature can be enabled per-process on some devices. The compiled code must match the device mode. The default is any, for devices that support it. -mstack-size=bytes Specify how many bytes of stack space will be requested for each GPU thread (wave-front). Beware that there may be many threads and limited memory available. The size of the stack allocation may also have an impact on run-time performance. The default is 32KB when using OpenACC or OpenMP, and 1MB otherwise. -mxnack Compile binaries suitable for devices with the XNACK feature enabled. Some devices always require XNACK and some allow the user to configure XNACK. The compiled code must match the device mode. The default is -mno-xnack. At present this option is a placeholder for support that is not yet implemented. ARC Options The following options control the architecture variant for which code is being compiled: -mbarrel-shifter Generate instructions supported by barrel shifter. This is the default unless -mcpu=ARC601 or -mcpu=ARCEM is in effect. -mjli-always Force to call a function using jli_s instruction. This option is valid only for ARCv2 architecture. -mcpu=cpu Set architecture type, register usage, and instruction scheduling parameters for cpu. There are also shortcut alias options available for backward compatibility and convenience. Supported values for cpu are arc600 Compile for ARC600. Aliases: -mA6, -mARC600. arc601 Compile for ARC601. Alias: -mARC601. arc700 Compile for ARC700. Aliases: -mA7, -mARC700. This is the default when configured with --with-cpu=arc700. arcem Compile for ARC EM. archs Compile for ARC HS. em Compile for ARC EM CPU with no hardware extensions. em4 Compile for ARC EM4 CPU. em4_dmips Compile for ARC EM4 DMIPS CPU. em4_fpus Compile for ARC EM4 DMIPS CPU with the single-precision floating-point extension. em4_fpuda Compile for ARC EM4 DMIPS CPU with single-precision floating- point and double assist instructions. hs Compile for ARC HS CPU with no hardware extensions except the atomic instructions. hs34 Compile for ARC HS34 CPU. hs38 Compile for ARC HS38 CPU. hs38_linux Compile for ARC HS38 CPU with all hardware extensions on. hs4x Compile for ARC HS4x CPU. hs4xd Compile for ARC HS4xD CPU. hs4x_rel31 Compile for ARC HS4x CPU release 3.10a. arc600_norm Compile for ARC 600 CPU with "norm" instructions enabled. arc600_mul32x16 Compile for ARC 600 CPU with "norm" and 32x16-bit multiply instructions enabled. arc600_mul64 Compile for ARC 600 CPU with "norm" and "mul64"-family instructions enabled. arc601_norm Compile for ARC 601 CPU with "norm" instructions enabled. arc601_mul32x16 Compile for ARC 601 CPU with "norm" and 32x16-bit multiply instructions enabled. arc601_mul64 Compile for ARC 601 CPU with "norm" and "mul64"-family instructions enabled. nps400 Compile for ARC 700 on NPS400 chip. em_mini Compile for ARC EM minimalist configuration featuring reduced register set. -mdpfp -mdpfp-compact Generate double-precision FPX instructions, tuned for the compact implementation. -mdpfp-fast Generate double-precision FPX instructions, tuned for the fast implementation. -mno-dpfp-lrsr Disable "lr" and "sr" instructions from using FPX extension aux registers. -mea Generate extended arithmetic instructions. Currently only "divaw", "adds", "subs", and "sat16" are supported. Only valid for -mcpu=ARC700. -mno-mpy Do not generate "mpy"-family instructions for ARC700. This option is deprecated. -mmul32x16 Generate 32x16-bit multiply and multiply-accumulate instructions. -mmul64 Generate "mul64" and "mulu64" instructions. Only valid for -mcpu=ARC600. -mnorm Generate "norm" instructions. This is the default if -mcpu=ARC700 is in effect. -mspfp -mspfp-compact Generate single-precision FPX instructions, tuned for the compact implementation. -mspfp-fast Generate single-precision FPX instructions, tuned for the fast implementation. -msimd Enable generation of ARC SIMD instructions via target-specific builtins. Only valid for -mcpu=ARC700. -msoft-float This option ignored; it is provided for compatibility purposes only. Software floating-point code is emitted by default, and this default can overridden by FPX options; -mspfp, -mspfp-compact, or -mspfp-fast for single precision, and -mdpfp, -mdpfp-compact, or -mdpfp-fast for double precision. -mswap Generate "swap" instructions. -matomic This enables use of the locked load/store conditional extension to implement atomic memory built-in functions. Not available for ARC 6xx or ARC EM cores. -mdiv-rem Enable "div" and "rem" instructions for ARCv2 cores. -mcode-density Enable code density instructions for ARC EM. This option is on by default for ARC HS. -mll64 Enable double load/store operations for ARC HS cores. -mtp-regno=regno Specify thread pointer register number. -mmpy-option=multo Compile ARCv2 code with a multiplier design option. You can specify the option using either a string or numeric value for multo. wlh1 is the default value. The recognized values are: 0 none No multiplier available. 1 w 16x16 multiplier, fully pipelined. The following instructions are enabled: "mpyw" and "mpyuw". 2 wlh1 32x32 multiplier, fully pipelined (1 stage). The following instructions are additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s". 3 wlh2 32x32 multiplier, fully pipelined (2 stages). The following instructions are additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s". 4 wlh3 Two 16x16 multipliers, blocking, sequential. The following instructions are additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s". 5 wlh4 One 16x16 multiplier, blocking, sequential. The following instructions are additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s". 6 wlh5 One 32x4 multiplier, blocking, sequential. The following instructions are additionally enabled: "mpy", "mpyu", "mpym", "mpymu", and "mpy_s". 7 plus_dmpy ARC HS SIMD support. 8 plus_macd ARC HS SIMD support. 9 plus_qmacw ARC HS SIMD support. This option is only available for ARCv2 cores. -mfpu=fpu Enables support for specific floating-point hardware extensions for ARCv2 cores. Supported values for fpu are: fpus Enables support for single-precision floating-point hardware extensions. fpud Enables support for double-precision floating-point hardware extensions. The single-precision floating-point extension is also enabled. Not available for ARC EM. fpuda Enables support for double-precision floating-point hardware extensions using double-precision assist instructions. The single-precision floating-point extension is also enabled. This option is only available for ARC EM. fpuda_div Enables support for double-precision floating-point hardware extensions using double-precision assist instructions. The single-precision floating-point, square-root, and divide extensions are also enabled. This option is only available for ARC EM. fpuda_fma Enables support for double-precision floating-point hardware extensions using double-precision assist instructions. The single-precision floating-point and fused multiply and add hardware extensions are also enabled. This option is only available for ARC EM. fpuda_all Enables support for double-precision floating-point hardware extensions using double-precision assist instructions. All single-precision floating-point hardware extensions are also enabled. This option is only available for ARC EM. fpus_div Enables support for single-precision floating-point, square- root and divide hardware extensions. fpud_div Enables support for double-precision floating-point, square- root and divide hardware extensions. This option includes option fpus_div. Not available for ARC EM. fpus_fma Enables support for single-precision floating-point and fused multiply and add hardware extensions. fpud_fma Enables support for double-precision floating-point and fused multiply and add hardware extensions. This option includes option fpus_fma. Not available for ARC EM. fpus_all Enables support for all single-precision floating-point hardware extensions. fpud_all Enables support for all single- and double-precision floating- point hardware extensions. Not available for ARC EM. -mirq-ctrl-saved=register-range, blink, lp_count Specifies general-purposes registers that the processor automatically saves/restores on interrupt entry and exit. register-range is specified as two registers separated by a dash. The register range always starts with "r0", the upper limit is "fp" register. blink and lp_count are optional. This option is only valid for ARC EM and ARC HS cores. -mrgf-banked-regs=number Specifies the number of registers replicated in second register bank on entry to fast interrupt. Fast interrupts are interrupts with the highest priority level P0. These interrupts save only PC and STATUS32 registers to avoid memory transactions during interrupt entry and exit sequences. Use this option when you are using fast interrupts in an ARC V2 family processor. Permitted values are 4, 8, 16, and 32. -mlpc-width=width Specify the width of the "lp_count" register. Valid values for width are 8, 16, 20, 24, 28 and 32 bits. The default width is fixed to 32 bits. If the width is less than 32, the compiler does not attempt to transform loops in your program to use the zero- delay loop mechanism unless it is known that the "lp_count" register can hold the required loop-counter value. Depending on the width specified, the compiler and run-time library might continue to use the loop mechanism for various needs. This option defines macro "__ARC_LPC_WIDTH__" with the value of width. -mrf16 This option instructs the compiler to generate code for a 16-entry register file. This option defines the "__ARC_RF16__" preprocessor macro. -mbranch-index Enable use of "bi" or "bih" instructions to implement jump tables. The following options are passed through to the assembler, and also define preprocessor macro symbols. -mdsp-packa Passed down to the assembler to enable the DSP Pack A extensions. Also sets the preprocessor symbol "__Xdsp_packa". This option is deprecated. -mdvbf Passed down to the assembler to enable the dual Viterbi butterfly extension. Also sets the preprocessor symbol "__Xdvbf". This option is deprecated. -mlock Passed down to the assembler to enable the locked load/store conditional extension. Also sets the preprocessor symbol "__Xlock". -mmac-d16 Passed down to the assembler. Also sets the preprocessor symbol "__Xxmac_d16". This option is deprecated. -mmac-24 Passed down to the assembler. Also sets the preprocessor symbol "__Xxmac_24". This option is deprecated. -mrtsc Passed down to the assembler to enable the 64-bit time-stamp counter extension instruction. Also sets the preprocessor symbol "__Xrtsc". This option is deprecated. -mswape Passed down to the assembler to enable the swap byte ordering extension instruction. Also sets the preprocessor symbol "__Xswape". -mtelephony Passed down to the assembler to enable dual- and single-operand instructions for telephony. Also sets the preprocessor symbol "__Xtelephony". This option is deprecated. -mxy Passed down to the assembler to enable the XY memory extension. Also sets the preprocessor symbol "__Xxy". The following options control how the assembly code is annotated: -misize Annotate assembler instructions with estimated addresses. -mannotate-align Explain what alignment considerations lead to the decision to make an instruction short or long. The following options are passed through to the linker: -marclinux Passed through to the linker, to specify use of the "arclinux" emulation. This option is enabled by default in tool chains built for "arc-linux-uclibc" and "arceb-linux-uclibc" targets when profiling is not requested. -marclinux_prof Passed through to the linker, to specify use of the "arclinux_prof" emulation. This option is enabled by default in tool chains built for "arc-linux-uclibc" and "arceb-linux-uclibc" targets when profiling is requested. The following options control the semantics of generated code: -mlong-calls Generate calls as register indirect calls, thus providing access to the full 32-bit address range. -mmedium-calls Don't use less than 25-bit addressing range for calls, which is the offset available for an unconditional branch-and-link instruction. Conditional execution of function calls is suppressed, to allow use of the 25-bit range, rather than the 21-bit range with conditional branch-and-link. This is the default for tool chains built for "arc-linux-uclibc" and "arceb-linux-uclibc" targets. -G num Put definitions of externally-visible data in a small data section if that data is no bigger than num bytes. The default value of num is 4 for any ARC configuration, or 8 when we have double load/store operations. -mno-sdata Do not generate sdata references. This is the default for tool chains built for "arc-linux-uclibc" and "arceb-linux-uclibc" targets. -mvolatile-cache Use ordinarily cached memory accesses for volatile references. This is the default. -mno-volatile-cache Enable cache bypass for volatile references. The following options fine tune code generation: -malign-call Does nothing. Preserved for backward compatibility. -mauto-modify-reg Enable the use of pre/post modify with register displacement. -mbbit-peephole Enable bbit peephole2. -mno-brcc This option disables a target-specific pass in arc_reorg to generate compare-and-branch ("brcc") instructions. It has no effect on generation of these instructions driven by the combiner pass. -mcase-vector-pcrel Use PC-relative switch case tables to enable case table shortening. This is the default for -Os. -mcompact-casesi Enable compact "casesi" pattern. This is the default for -Os, and only available for ARCv1 cores. This option is deprecated. -mno-cond-exec Disable the ARCompact-specific pass to generate conditional execution instructions. Due to delay slot scheduling and interactions between operand numbers, literal sizes, instruction lengths, and the support for conditional execution, the target-independent pass to generate conditional execution is often lacking, so the ARC port has kept a special pass around that tries to find more conditional execution generation opportunities after register allocation, branch shortening, and delay slot scheduling have been done. This pass generally, but not always, improves performance and code size, at the cost of extra compilation time, which is why there is an option to switch it off. If you have a problem with call instructions exceeding their allowable offset range because they are conditionalized, you should consider using -mmedium-calls instead. -mearly-cbranchsi Enable pre-reload use of the "cbranchsi" pattern. -mexpand-adddi Expand "adddi3" and "subdi3" at RTL generation time into "add.f", "adc" etc. This option is deprecated. -mindexed-loads Enable the use of indexed loads. This can be problematic because some optimizers then assume that indexed stores exist, which is not the case. -mlra Enable Local Register Allocation. This is still experimental for ARC, so by default the compiler uses standard reload (i.e. -mno-lra). -mlra-priority-none Don't indicate any priority for target registers. -mlra-priority-compact Indicate target register priority for r0..r3 / r12..r15. -mlra-priority-noncompact Reduce target register priority for r0..r3 / r12..r15. -mmillicode When optimizing for size (using -Os), prologues and epilogues that have to save or restore a large number of registers are often shortened by using call to a special function in libgcc; this is referred to as a millicode call. As these calls can pose performance issues, and/or cause linking issues when linking in a nonstandard way, this option is provided to turn on or off millicode call generation. -mcode-density-frame This option enable the compiler to emit "enter" and "leave" instructions. These instructions are only valid for CPUs with code-density feature. -mmixed-code Does nothing. Preserved for backward compatibility. -mq-class Ths option is deprecated. Enable q instruction alternatives. This is the default for -Os. -mRcq Does nothing. Preserved for backward compatibility. -mRcw Does nothing. Preserved for backward compatibility. -msize-level=level Fine-tune size optimization with regards to instruction lengths and alignment. The recognized values for level are: 0 No size optimization. This level is deprecated and treated like 1. 1 Short instructions are used opportunistically. 2 In addition, alignment of loops and of code after barriers are dropped. 3 In addition, optional data alignment is dropped, and the option Os is enabled. This defaults to 3 when -Os is in effect. Otherwise, the behavior when this is not set is equivalent to level 1. -mtune=cpu Set instruction scheduling parameters for cpu, overriding any implied by -mcpu=. Supported values for cpu are ARC600 Tune for ARC600 CPU. ARC601 Tune for ARC601 CPU. ARC700 Tune for ARC700 CPU with standard multiplier block. ARC700-xmac Tune for ARC700 CPU with XMAC block. ARC725D Tune for ARC725D CPU. ARC750D Tune for ARC750D CPU. core3 Tune for ARCv2 core3 type CPU. This option enable usage of "dbnz" instruction. release31a Tune for ARC4x release 3.10a. -mmultcost=num Cost to assume for a multiply instruction, with 4 being equal to a normal instruction. -munalign-prob-threshold=probability Does nothing. Preserved for backward compatibility. The following options are maintained for backward compatibility, but are now deprecated and will be removed in a future release: -margonaut Obsolete FPX. -mbig-endian -EB Compile code for big-endian targets. Use of these options is now deprecated. Big-endian code is supported by configuring GCC to build "arceb-elf32" and "arceb-linux-uclibc" targets, for which big endian is the default. -mlittle-endian -EL Compile code for little-endian targets. Use of these options is now deprecated. Little-endian code is supported by configuring GCC to build "arc-elf32" and "arc-linux-uclibc" targets, for which little endian is the default. -mbarrel_shifter Replaced by -mbarrel-shifter. -mdpfp_compact Replaced by -mdpfp-compact. -mdpfp_fast Replaced by -mdpfp-fast. -mdsp_packa Replaced by -mdsp-packa. -mEA Replaced by -mea. -mmac_24 Replaced by -mmac-24. -mmac_d16 Replaced by -mmac-d16. -mspfp_compact Replaced by -mspfp-compact. -mspfp_fast Replaced by -mspfp-fast. -mtune=cpu Values arc600, arc601, arc700 and arc700-xmac for cpu are replaced by ARC600, ARC601, ARC700 and ARC700-xmac respectively. -multcost=num Replaced by -mmultcost. ARM Options These -m options are defined for the ARM port: -mabi=name Generate code for the specified ABI. Permissible values are: apcs- gnu, atpcs, aapcs, aapcs-linux and iwmmxt. -mapcs-frame Generate a stack frame that is compliant with the ARM Procedure Call Standard for all functions, even if this is not strictly necessary for correct execution of the code. Specifying -fomit-frame-pointer with this option causes the stack frames not to be generated for leaf functions. The default is -mno-apcs-frame. This option is deprecated. -mapcs This is a synonym for -mapcs-frame and is deprecated. -mthumb-interwork Generate code that supports calling between the ARM and Thumb instruction sets. Without this option, on pre-v5 architectures, the two instruction sets cannot be reliably used inside one program. The default is -mno-thumb-interwork, since slightly larger code is generated when -mthumb-interwork is specified. In AAPCS configurations this option is meaningless. -mno-sched-prolog Prevent the reordering of instructions in the function prologue, or the merging of those instruction with the instructions in the function's body. This means that all functions start with a recognizable set of instructions (or in fact one of a choice from a small set of different function prologues), and this information can be used to locate the start of functions inside an executable piece of code. The default is -msched-prolog. -mfloat-abi=name Specifies which floating-point ABI to use. Permissible values are: soft, softfp and hard. Specifying soft causes GCC to generate output containing library calls for floating-point operations. softfp allows the generation of code using hardware floating-point instructions, but still uses the soft-float calling conventions. hard allows generation of floating-point instructions and uses FPU-specific calling conventions. The default depends on the specific target configuration. Note that the hard-float and soft-float ABIs are not link-compatible; you must compile your entire program with the same ABI, and link with a compatible set of libraries. -mgeneral-regs-only Generate code which uses only the general-purpose registers. This will prevent the compiler from using floating-point and Advanced SIMD registers but will not impose any restrictions on the assembler. -mlittle-endian Generate code for a processor running in little-endian mode. This is the default for all standard configurations. -mbig-endian Generate code for a processor running in big-endian mode; the default is to compile code for a little-endian processor. -mbe8 -mbe32 When linking a big-endian image select between BE8 and BE32 formats. The option has no effect for little-endian images and is ignored. The default is dependent on the selected target architecture. For ARMv6 and later architectures the default is BE8, for older architectures the default is BE32. BE32 format has been deprecated by ARM. -march=name[+extension...] This specifies the name of the target ARM architecture. GCC uses this name to determine what kind of instructions it can emit when generating assembly code. This option can be used in conjunction with or instead of the -mcpu= option. Permissible names are: armv4t, armv5t, armv5te, armv6, armv6j, armv6k, armv6kz, armv6t2, armv6z, armv6zk, armv7, armv7-a, armv7ve, armv8-a, armv8.1-a, armv8.2-a, armv8.3-a, armv8.4-a, armv8.5-a, armv8.6-a, armv9-a, armv7-r, armv8-r, armv6-m, armv6s-m, armv7-m, armv7e-m, armv8-m.base, armv8-m.main, armv8.1-m.main, armv9-a, iwmmxt and iwmmxt2. Additionally, the following architectures, which lack support for the Thumb execution state, are recognized but support is deprecated: armv4. Many of the architectures support extensions. These can be added by appending +extension to the architecture name. Extension options are processed in order and capabilities accumulate. An extension will also enable any necessary base extensions upon which it depends. For example, the +crypto extension will always enable the +simd extension. The exception to the additive construction is for extensions that are prefixed with +no...: these extensions disable the specified option and any other extensions that may depend on the presence of that extension. For example, -march=armv7-a+simd+nofp+vfpv4 is equivalent to writing -march=armv7-a+vfpv4 since the +simd option is entirely disabled by the +nofp option that follows it. Most extension names are generically named, but have an effect that is dependent upon the architecture to which it is applied. For example, the +simd option can be applied to both armv7-a and armv8-a architectures, but will enable the original ARMv7-A Advanced SIMD (Neon) extensions for armv7-a and the ARMv8-A variant for armv8-a. The table below lists the supported extensions for each architecture. Architectures not mentioned do not support any extensions. armv5te armv6 armv6j armv6k armv6kz armv6t2 armv6z armv6zk +fp The VFPv2 floating-point instructions. The extension +vfpv2 can be used as an alias for this extension. +nofp Disable the floating-point instructions. armv7 The common subset of the ARMv7-A, ARMv7-R and ARMv7-M architectures. +fp The VFPv3 floating-point instructions, with 16 double- precision registers. The extension +vfpv3-d16 can be used as an alias for this extension. Note that floating-point is not supported by the base ARMv7-M architecture, but is compatible with both the ARMv7-A and ARMv7-R architectures. +nofp Disable the floating-point instructions. armv7-a +mp The multiprocessing extension. +sec The security extension. +fp The VFPv3 floating-point instructions, with 16 double- precision registers. The extension +vfpv3-d16 can be used as an alias for this extension. +simd The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions. The extensions +neon and +neon-vfpv3 can be used as aliases for this extension. +vfpv3 The VFPv3 floating-point instructions, with 32 double- precision registers. +vfpv3-d16-fp16 The VFPv3 floating-point instructions, with 16 double- precision registers and the half-precision floating-point conversion operations. +vfpv3-fp16 The VFPv3 floating-point instructions, with 32 double- precision registers and the half-precision floating-point conversion operations. +vfpv4-d16 The VFPv4 floating-point instructions, with 16 double- precision registers. +vfpv4 The VFPv4 floating-point instructions, with 32 double- precision registers. +neon-fp16 The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions, with the half-precision floating-point conversion operations. +neon-vfpv4 The Advanced SIMD (Neon) v2 and the VFPv4 floating-point instructions. +nosimd Disable the Advanced SIMD instructions (does not disable floating point). +nofp Disable the floating-point and Advanced SIMD instructions. armv7ve The extended version of the ARMv7-A architecture with support for virtualization. +fp The VFPv4 floating-point instructions, with 16 double- precision registers. The extension +vfpv4-d16 can be used as an alias for this extension. +simd The Advanced SIMD (Neon) v2 and the VFPv4 floating-point instructions. The extension +neon-vfpv4 can be used as an alias for this extension. +vfpv3-d16 The VFPv3 floating-point instructions, with 16 double- precision registers. +vfpv3 The VFPv3 floating-point instructions, with 32 double- precision registers. +vfpv3-d16-fp16 The VFPv3 floating-point instructions, with 16 double- precision registers and the half-precision floating-point conversion operations. +vfpv3-fp16 The VFPv3 floating-point instructions, with 32 double- precision registers and the half-precision floating-point conversion operations. +vfpv4-d16 The VFPv4 floating-point instructions, with 16 double- precision registers. +vfpv4 The VFPv4 floating-point instructions, with 32 double- precision registers. +neon The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions. The extension +neon-vfpv3 can be used as an alias for this extension. +neon-fp16 The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions, with the half-precision floating-point conversion operations. +nosimd Disable the Advanced SIMD instructions (does not disable floating point). +nofp Disable the floating-point and Advanced SIMD instructions. armv8-a +crc The Cyclic Redundancy Check (CRC) instructions. +simd The ARMv8-A Advanced SIMD and floating-point instructions. +crypto The cryptographic instructions. +nocrypto Disable the cryptographic instructions. +nofp Disable the floating-point, Advanced SIMD and cryptographic instructions. +sb Speculation Barrier Instruction. +predres Execution and Data Prediction Restriction Instructions. armv8.1-a +simd The ARMv8.1-A Advanced SIMD and floating-point instructions. +crypto The cryptographic instructions. This also enables the Advanced SIMD and floating-point instructions. +nocrypto Disable the cryptographic instructions. +nofp Disable the floating-point, Advanced SIMD and cryptographic instructions. +sb Speculation Barrier Instruction. +predres Execution and Data Prediction Restriction Instructions. armv8.2-a armv8.3-a +fp16 The half-precision floating-point data processing instructions. This also enables the Advanced SIMD and floating-point instructions. +fp16fml The half-precision floating-point fmla extension. This also enables the half-precision floating-point extension and Advanced SIMD and floating-point instructions. +simd The ARMv8.1-A Advanced SIMD and floating-point instructions. +crypto The cryptographic instructions. This also enables the Advanced SIMD and floating-point instructions. +dotprod Enable the Dot Product extension. This also enables Advanced SIMD instructions. +nocrypto Disable the cryptographic extension. +nofp Disable the floating-point, Advanced SIMD and cryptographic instructions. +sb Speculation Barrier Instruction. +predres Execution and Data Prediction Restriction Instructions. +i8mm 8-bit Integer Matrix Multiply instructions. This also enables Advanced SIMD and floating-point instructions. +bf16 Brain half-precision floating-point instructions. This also enables Advanced SIMD and floating-point instructions. armv8.4-a +fp16 The half-precision floating-point data processing instructions. This also enables the Advanced SIMD and floating-point instructions as well as the Dot Product extension and the half-precision floating-point fmla extension. +simd The ARMv8.3-A Advanced SIMD and floating-point instructions as well as the Dot Product extension. +crypto The cryptographic instructions. This also enables the Advanced SIMD and floating-point instructions as well as the Dot Product extension. +nocrypto Disable the cryptographic extension. +nofp Disable the floating-point, Advanced SIMD and cryptographic instructions. +sb Speculation Barrier Instruction. +predres Execution and Data Prediction Restriction Instructions. +i8mm 8-bit Integer Matrix Multiply instructions. This also enables Advanced SIMD and floating-point instructions. +bf16 Brain half-precision floating-point instructions. This also enables Advanced SIMD and floating-point instructions. armv8.5-a +fp16 The half-precision floating-point data processing instructions. This also enables the Advanced SIMD and floating-point instructions as well as the Dot Product extension and the half-precision floating-point fmla extension. +simd The ARMv8.3-A Advanced SIMD and floating-point instructions as well as the Dot Product extension. +crypto The cryptographic instructions. This also enables the Advanced SIMD and floating-point instructions as well as the Dot Product extension. +nocrypto Disable the cryptographic extension. +nofp Disable the floating-point, Advanced SIMD and cryptographic instructions. +i8mm 8-bit Integer Matrix Multiply instructions. This also enables Advanced SIMD and floating-point instructions. +bf16 Brain half-precision floating-point instructions. This also enables Advanced SIMD and floating-point instructions. armv8.6-a +fp16 The half-precision floating-point data processing instructions. This also enables the Advanced SIMD and floating-point instructions as well as the Dot Product extension and the half-precision floating-point fmla extension. +simd The ARMv8.3-A Advanced SIMD and floating-point instructions as well as the Dot Product extension. +crypto The cryptographic instructions. This also enables the Advanced SIMD and floating-point instructions as well as the Dot Product extension. +nocrypto Disable the cryptographic extension. +nofp Disable the floating-point, Advanced SIMD and cryptographic instructions. +i8mm 8-bit Integer Matrix Multiply instructions. This also enables Advanced SIMD and floating-point instructions. +bf16 Brain half-precision floating-point instructions. This also enables Advanced SIMD and floating-point instructions. armv7-r +fp.sp The single-precision VFPv3 floating-point instructions. The extension +vfpv3xd can be used as an alias for this extension. +fp The VFPv3 floating-point instructions with 16 double- precision registers. The extension +vfpv3-d16 can be used as an alias for this extension. +vfpv3xd-d16-fp16 The single-precision VFPv3 floating-point instructions with 16 double-precision registers and the half-precision floating-point conversion operations. +vfpv3-d16-fp16 The VFPv3 floating-point instructions with 16 double- precision registers and the half-precision floating-point conversion operations. +nofp Disable the floating-point extension. +idiv The ARM-state integer division instructions. +noidiv Disable the ARM-state integer division extension. armv7e-m +fp The single-precision VFPv4 floating-point instructions. +fpv5 The single-precision FPv5 floating-point instructions. +fp.dp The single- and double-precision FPv5 floating-point instructions. +nofp Disable the floating-point extensions. armv8.1-m.main +dsp The DSP instructions. +mve The M-Profile Vector Extension (MVE) integer instructions. +mve.fp The M-Profile Vector Extension (MVE) integer and single precision floating-point instructions. +fp The single-precision floating-point instructions. +fp.dp The single- and double-precision floating-point instructions. +nofp Disable the floating-point extension. +cdecp0, +cdecp1, ... , +cdecp7 Enable the Custom Datapath Extension (CDE) on selected coprocessors according to the numbers given in the options in the range 0 to 7. +pacbti Enable the Pointer Authentication and Branch Target Identification Extension. armv8-m.main +dsp The DSP instructions. +nodsp Disable the DSP extension. +fp The single-precision floating-point instructions. +fp.dp The single- and double-precision floating-point instructions. +nofp Disable the floating-point extension. +cdecp0, +cdecp1, ... , +cdecp7 Enable the Custom Datapath Extension (CDE) on selected coprocessors according to the numbers given in the options in the range 0 to 7. armv8-r +crc The Cyclic Redundancy Check (CRC) instructions. +fp.sp The single-precision FPv5 floating-point instructions. +simd The ARMv8-A Advanced SIMD and floating-point instructions. +crypto The cryptographic instructions. +nocrypto Disable the cryptographic instructions. +nofp Disable the floating-point, Advanced SIMD and cryptographic instructions. -march=native causes the compiler to auto-detect the architecture of the build computer. At present, this feature is only supported on GNU/Linux, and not all architectures are recognized. If the auto-detect is unsuccessful the option has no effect. -mtune=name This option specifies the name of the target ARM processor for which GCC should tune the performance of the code. For some ARM implementations better performance can be obtained by using this option. Permissible names are: arm7tdmi, arm7tdmi-s, arm710t, arm720t, arm740t, strongarm, strongarm110, strongarm1100, strongarm1110, arm8, arm810, arm9, arm9e, arm920, arm920t, arm922t, arm946e-s, arm966e-s, arm968e-s, arm926ej-s, arm940t, arm9tdmi, arm10tdmi, arm1020t, arm1026ej-s, arm10e, arm1020e, arm1022e, arm1136j-s, arm1136jf-s, mpcore, mpcorenovfp, arm1156t2-s, arm1156t2f-s, arm1176jz-s, arm1176jzf-s, generic-armv7-a, cortex-a5, cortex-a7, cortex-a8, cortex-a9, cortex-a12, cortex-a15, cortex-a17, cortex-a32, cortex-a35, cortex-a53, cortex-a55, cortex-a57, cortex-a72, cortex-a73, cortex-a75, cortex-a76, cortex-a76ae, cortex-a77, cortex-a78, cortex-a78ae, cortex-a78c, cortex-a710, ares, cortex-r4, cortex-r4f, cortex-r5, cortex-r7, cortex-r8, cortex-r52, cortex-r52plus, cortex-m0, cortex-m0plus, cortex-m1, cortex-m3, cortex-m4, cortex-m7, cortex-m23, cortex-m33, cortex-m35p, cortex-m55, cortex-m85, cortex-x1, cortex-x1c, cortex-m1.small-multiply, cortex-m0.small-multiply, cortex-m0plus.small-multiply, exynos-m1, marvell-pj4, neoverse-n1, neoverse-n2, neoverse-v1, xscale, iwmmxt, iwmmxt2, ep9312, fa526, fa626, fa606te, fa626te, fmp626, fa726te, star-mc1, xgene1. Additionally, this option can specify that GCC should tune the performance of the code for a big.LITTLE system. Permissible names are: cortex-a15.cortex-a7, cortex-a17.cortex-a7, cortex-a57.cortex-a53, cortex-a72.cortex-a53, cortex-a72.cortex-a35, cortex-a73.cortex-a53, cortex-a75.cortex-a55, cortex-a76.cortex-a55. -mtune=generic-arch specifies that GCC should tune the performance for a blend of processors within architecture arch. The aim is to generate code that run well on the current most popular processors, balancing between optimizations that benefit some CPUs in the range, and avoiding performance pitfalls of other CPUs. The effects of this option may change in future GCC versions as CPU models come and go. -mtune permits the same extension options as -mcpu, but the extension options do not affect the tuning of the generated code. -mtune=native causes the compiler to auto-detect the CPU of the build computer. At present, this feature is only supported on GNU/Linux, and not all architectures are recognized. If the auto- detect is unsuccessful the option has no effect. -mcpu=name[+extension...] This specifies the name of the target ARM processor. GCC uses this name to derive the name of the target ARM architecture (as if specified by -march) and the ARM processor type for which to tune for performance (as if specified by -mtune). Where this option is used in conjunction with -march or -mtune, those options take precedence over the appropriate part of this option. Many of the supported CPUs implement optional architectural extensions. Where this is so the architectural extensions are normally enabled by default. If implementations that lack the extension exist, then the extension syntax can be used to disable those extensions that have been omitted. For floating-point and Advanced SIMD (Neon) instructions, the settings of the options -mfloat-abi and -mfpu must also be considered: floating-point and Advanced SIMD instructions will only be used if -mfloat-abi is not set to soft; and any setting of -mfpu other than auto will override the available floating-point and SIMD extension instructions. For example, cortex-a9 can be found in three major configurations: integer only, with just a floating-point unit or with floating- point and Advanced SIMD. The default is to enable all the instructions, but the extensions +nosimd and +nofp can be used to disable just the SIMD or both the SIMD and floating-point instructions respectively. Permissible names for this option are the same as those for -mtune. The following extension options are common to the listed CPUs: +nodsp Disable the DSP instructions on cortex-m33, cortex-m35p, cortex-m55 and cortex-m85. Also disable the M-Profile Vector Extension (MVE) integer and single precision floating-point instructions on cortex-m55 and cortex-m85. +nopacbti Disable the Pointer Authentication and Branch Target Identification Extension on cortex-m85. +nomve Disable the M-Profile Vector Extension (MVE) integer and single precision floating-point instructions on cortex-m55 and cortex-m85. +nomve.fp Disable the M-Profile Vector Extension (MVE) single precision floating-point instructions on cortex-m55 and cortex-m85. +cdecp0, +cdecp1, ... , +cdecp7 Enable the Custom Datapath Extension (CDE) on selected coprocessors according to the numbers given in the options in the range 0 to 7 on cortex-m55. +nofp Disables the floating-point instructions on arm9e, arm946e-s, arm966e-s, arm968e-s, arm10e, arm1020e, arm1022e, arm926ej-s, arm1026ej-s, cortex-r5, cortex-r7, cortex-r8, cortex-m4, cortex-m7, cortex-m33, cortex-m35p cortex-m4, cortex-m7, cortex-m33, cortex-m35p, cortex-m55 and cortex-m85. Disables the floating-point and SIMD instructions on generic-armv7-a, cortex-a5, cortex-a7, cortex-a8, cortex-a9, cortex-a12, cortex-a15, cortex-a17, cortex-a15.cortex-a7, cortex-a17.cortex-a7, cortex-a32, cortex-a35, cortex-a53 and cortex-a55. +nofp.dp Disables the double-precision component of the floating-point instructions on cortex-r5, cortex-r7, cortex-r8, cortex-r52, cortex-r52plus and cortex-m7. +nosimd Disables the SIMD (but not floating-point) instructions on generic-armv7-a, cortex-a5, cortex-a7 and cortex-a9. +crypto Enables the cryptographic instructions on cortex-a32, cortex-a35, cortex-a53, cortex-a55, cortex-a57, cortex-a72, cortex-a73, cortex-a75, exynos-m1, xgene1, cortex-a57.cortex-a53, cortex-a72.cortex-a53, cortex-a73.cortex-a35, cortex-a73.cortex-a53 and cortex-a75.cortex-a55. Additionally the generic-armv7-a pseudo target defaults to VFPv3 with 16 double-precision registers. It supports the following extension options: mp, sec, vfpv3-d16, vfpv3, vfpv3-d16-fp16, vfpv3-fp16, vfpv4-d16, vfpv4, neon, neon-vfpv3, neon-fp16, neon-vfpv4. The meanings are the same as for the extensions to -march=armv7-a. -mcpu=generic-arch is also permissible, and is equivalent to -march=arch -mtune=generic-arch. See -mtune for more information. -mcpu=native causes the compiler to auto-detect the CPU of the build computer. At present, this feature is only supported on GNU/Linux, and not all architectures are recognized. If the auto- detect is unsuccessful the option has no effect. -mfpu=name This specifies what floating-point hardware (or hardware emulation) is available on the target. Permissible names are: auto, vfpv2, vfpv3, vfpv3-fp16, vfpv3-d16, vfpv3-d16-fp16, vfpv3xd, vfpv3xd-fp16, neon-vfpv3, neon-fp16, vfpv4, vfpv4-d16, fpv4-sp-d16, neon-vfpv4, fpv5-d16, fpv5-sp-d16, fp-armv8, neon-fp-armv8 and crypto-neon-fp-armv8. Note that neon is an alias for neon-vfpv3 and vfp is an alias for vfpv2. The setting auto is the default and is special. It causes the compiler to select the floating-point and Advanced SIMD instructions based on the settings of -mcpu and -march. If the selected floating-point hardware includes the NEON extension (e.g. -mfpu=neon), note that floating-point operations are not generated by GCC's auto-vectorization pass unless -funsafe-math-optimizations is also specified. This is because NEON hardware does not fully implement the IEEE 754 standard for floating-point arithmetic (in particular denormal values are treated as zero), so the use of NEON instructions may lead to a loss of precision. You can also set the fpu name at function level by using the "target("fpu=")" function attributes or pragmas. -mfp16-format=name Specify the format of the "__fp16" half-precision floating-point type. Permissible names are none, ieee, and alternative; the default is none, in which case the "__fp16" type is not defined. -mstructure-size-boundary=n The sizes of all structures and unions are rounded up to a multiple of the number of bits set by this option. Permissible values are 8, 32 and 64. The default value varies for different toolchains. For the COFF targeted toolchain the default value is 8. A value of 64 is only allowed if the underlying ABI supports it. Specifying a larger number can produce faster, more efficient code, but can also increase the size of the program. Different values are potentially incompatible. Code compiled with one value cannot necessarily expect to work with code or libraries compiled with another value, if they exchange information using structures or unions. This option is deprecated. -mabort-on-noreturn Generate a call to the function "abort" at the end of a "noreturn" function. It is executed if the function tries to return. -mlong-calls -mno-long-calls Tells the compiler to perform function calls by first loading the address of the function into a register and then performing a subroutine call on this register. This switch is needed if the target function lies outside of the 64-megabyte addressing range of the offset-based version of subroutine call instruction. Even if this switch is enabled, not all function calls are turned into long calls. The heuristic is that static functions, functions that have the "short_call" attribute, functions that are inside the scope of a "#pragma no_long_calls" directive, and functions whose definitions have already been compiled within the current compilation unit are not turned into long calls. The exceptions to this rule are that weak function definitions, functions with the "long_call" attribute or the "section" attribute, and functions that are within the scope of a "#pragma long_calls" directive are always turned into long calls. This feature is not enabled by default. Specifying -mno-long-calls restores the default behavior, as does placing the function calls within the scope of a "#pragma long_calls_off" directive. Note these switches have no effect on how the compiler generates code to handle function calls via function pointers. -msingle-pic-base Treat the register used for PIC addressing as read-only, rather than loading it in the prologue for each function. The runtime system is responsible for initializing this register with an appropriate value before execution begins. -mpic-register=reg Specify the register to be used for PIC addressing. For standard PIC base case, the default is any suitable register determined by compiler. For single PIC base case, the default is R9 if target is EABI based or stack-checking is enabled, otherwise the default is R10. -mpic-data-is-text-relative Assume that the displacement between the text and data segments is fixed at static link time. This permits using PC-relative addressing operations to access data known to be in the data segment. For non-VxWorks RTP targets, this option is enabled by default. When disabled on such targets, it will enable -msingle-pic-base by default. -mpoke-function-name Write the name of each function into the text section, directly preceding the function prologue. The generated code is similar to this: t0 .ascii "arm_poke_function_name", 0 .align t1 .word 0xff000000 + (t1 - t0) arm_poke_function_name mov ip, sp stmfd sp!, {fp, ip, lr, pc} sub fp, ip, #4 When performing a stack backtrace, code can inspect the value of "pc" stored at "fp + 0". If the trace function then looks at location "pc - 12" and the top 8 bits are set, then we know that there is a function name embedded immediately preceding this location and has length "((pc[-3]) & 0xff000000)". -mthumb -marm Select between generating code that executes in ARM and Thumb states. The default for most configurations is to generate code that executes in ARM state, but the default can be changed by configuring GCC with the --with-mode=state configure option. You can also override the ARM and Thumb mode for each function by using the "target("thumb")" and "target("arm")" function attributes or pragmas. -mflip-thumb Switch ARM/Thumb modes on alternating functions. This option is provided for regression testing of mixed Thumb/ARM code generation, and is not intended for ordinary use in compiling code. -mtpcs-frame Generate a stack frame that is compliant with the Thumb Procedure Call Standard for all non-leaf functions. (A leaf function is one that does not call any other functions.) The default is -mno-tpcs-frame. -mtpcs-leaf-frame Generate a stack frame that is compliant with the Thumb Procedure Call Standard for all leaf functions. (A leaf function is one that does not call any other functions.) The default is -mno-apcs-leaf-frame. -mcallee-super-interworking Gives all externally visible functions in the file being compiled an ARM instruction set header which switches to Thumb mode before executing the rest of the function. This allows these functions to be called from non-interworking code. This option is not valid in AAPCS configurations because interworking is enabled by default. -mcaller-super-interworking Allows calls via function pointers (including virtual functions) to execute correctly regardless of whether the target code has been compiled for interworking or not. There is a small overhead in the cost of executing a function pointer if this option is enabled. This option is not valid in AAPCS configurations because interworking is enabled by default. -mtp=name Specify the access model for the thread local storage pointer. The valid models are soft, which generates calls to "__aeabi_read_tp", cp15, which fetches the thread pointer from "cp15" directly (supported in the arm6k architecture), and auto, which uses the best available method for the selected processor. The default setting is auto. -mtls-dialect=dialect Specify the dialect to use for accessing thread local storage. Two dialects are supported---gnu and gnu2. The gnu dialect selects the original GNU scheme for supporting local and global dynamic TLS models. The gnu2 dialect selects the GNU descriptor scheme, which provides better performance for shared libraries. The GNU descriptor scheme is compatible with the original scheme, but does require new assembler, linker and library support. Initial and local exec TLS models are unaffected by this option and always use the original scheme. -mword-relocations Only generate absolute relocations on word-sized values (i.e. R_ARM_ABS32). This is enabled by default on targets (uClinux, SymbianOS) where the runtime loader imposes this restriction, and when -fpic or -fPIC is specified. This option conflicts with -mslow-flash-data. -mfix-cortex-m3-ldrd Some Cortex-M3 cores can cause data corruption when "ldrd" instructions with overlapping destination and base registers are used. This option avoids generating these instructions. This option is enabled by default when -mcpu=cortex-m3 is specified. -mfix-cortex-a57-aes-1742098 -mno-fix-cortex-a57-aes-1742098 -mfix-cortex-a72-aes-1655431 -mno-fix-cortex-a72-aes-1655431 Enable (disable) mitigation for an erratum on Cortex-A57 and Cortex-A72 that affects the AES cryptographic instructions. This option is enabled by default when either -mcpu=cortex-a57 or -mcpu=cortex-a72 is specified. -munaligned-access -mno-unaligned-access Enables (or disables) reading and writing of 16- and 32- bit values from addresses that are not 16- or 32- bit aligned. By default unaligned access is disabled for all pre-ARMv6, all ARMv6-M and for ARMv8-M Baseline architectures, and enabled for all other architectures. If unaligned access is not enabled then words in packed data structures are accessed a byte at a time. The ARM attribute "Tag_CPU_unaligned_access" is set in the generated object file to either true or false, depending upon the setting of this option. If unaligned access is enabled then the preprocessor symbol "__ARM_FEATURE_UNALIGNED" is also defined. -mneon-for-64bits This option is deprecated and has no effect. -mslow-flash-data Assume loading data from flash is slower than fetching instruction. Therefore literal load is minimized for better performance. This option is only supported when compiling for ARMv7 M-profile and off by default. It conflicts with -mword-relocations. -masm-syntax-unified Assume inline assembler is using unified asm syntax. The default is currently off which implies divided syntax. This option has no impact on Thumb2. However, this may change in future releases of GCC. Divided syntax should be considered deprecated. -mrestrict-it Restricts generation of IT blocks to conform to the rules of ARMv8-A. IT blocks can only contain a single 16-bit instruction from a select set of instructions. This option is on by default for ARMv8-A Thumb mode. -mprint-tune-info Print CPU tuning information as comment in assembler file. This is an option used only for regression testing of the compiler and not intended for ordinary use in compiling code. This option is disabled by default. -mverbose-cost-dump Enable verbose cost model dumping in the debug dump files. This option is provided for use in debugging the compiler. -mpure-code Do not allow constant data to be placed in code sections. Additionally, when compiling for ELF object format give all text sections the ELF processor-specific section attribute "SHF_ARM_PURECODE". This option is only available when generating non-pic code for M-profile targets. -mcmse Generate secure code as per the "ARMv8-M Security Extensions: Requirements on Development Tools Engineering Specification", which can be found on <https://developer.arm.com/documentation/ecm0359818/latest/>. -mfix-cmse-cve-2021-35465 Mitigate against a potential security issue with the "VLLDM" instruction in some M-profile devices when using CMSE (CVE-2021-365465). This option is enabled by default when the option -mcpu= is used with "cortex-m33", "cortex-m35p", "cortex-m55", "cortex-m85" or "star-mc1". The option -mno-fix-cmse-cve-2021-35465 can be used to disable the mitigation. -mstack-protector-guard=guard -mstack-protector-guard-offset=offset Generate stack protection code using canary at guard. Supported locations are global for a global canary or tls for a canary accessible via the TLS register. The option -mstack-protector-guard-offset= is for use with -fstack-protector-guard=tls and not for use in user-land code. -mfdpic -mno-fdpic Select the FDPIC ABI, which uses 64-bit function descriptors to represent pointers to functions. When the compiler is configured for "arm-*-uclinuxfdpiceabi" targets, this option is on by default and implies -fPIE if none of the PIC/PIE-related options is provided. On other targets, it only enables the FDPIC-specific code generation features, and the user should explicitly provide the PIC/PIE-related options as needed. Note that static linking is not supported because it would still involve the dynamic linker when the program self-relocates. If such behavior is acceptable, use -static and -Wl,-dynamic-linker options. The opposite -mno-fdpic option is useful (and required) to build the Linux kernel using the same ("arm-*-uclinuxfdpiceabi") toolchain as the one used to build the userland programs. -mbranch-protection=none|standard|pac-ret[+leaf][+bti]|bti[+pac-ret[+leaf]] Enable branch protection features (armv8.1-m.main only). none generate code without branch protection or return address signing. standard[+leaf] generate code with all branch protection features enabled at their standard level. pac-ret[+leaf] generate code with return address signing set to its standard level, which is to sign all functions that save the return address to memory. leaf When return address signing is enabled, also sign leaf functions even if they do not write the return address to memory. +bti Add landing- pad instructions at the permitted targets of indirect branch instructions. If the +pacbti architecture extension is not enabled, then all branch protection and return address signing operations are constrained to use only the instructions defined in the architectural-NOP space. The generated code will remain backwards- compatible with earlier versions of the architecture, but the additional security can be enabled at run time on processors that support the PACBTI extension. Branch target enforcement using BTI can only be enabled at runtime if all code in the application has been compiled with at least -mbranch-protection=bti. Any setting other than none is supported only on armv8-m.main or later. The default is to generate code without branch protection or return address signing. AVR Options These options are defined for AVR implementations: -mmcu=mcu Specify Atmel AVR instruction set architectures (ISA) or MCU type. The default for this option is avr2. GCC supports the following AVR devices and ISAs: "avr2" "Classic" devices with up to 8 KiB of program memory. mcu = "attiny22", "attiny26", "at90s2313", "at90s2323", "at90s2333", "at90s2343", "at90s4414", "at90s4433", "at90s4434", "at90c8534", "at90s8515", "at90s8535". "avr25" "Classic" devices with up to 8 KiB of program memory and with the "MOVW" instruction. mcu = "attiny13", "attiny13a", "attiny24", "attiny24a", "attiny25", "attiny261", "attiny261a", "attiny2313", "attiny2313a", "attiny43u", "attiny44", "attiny44a", "attiny45", "attiny48", "attiny441", "attiny461", "attiny461a", "attiny4313", "attiny84", "attiny84a", "attiny85", "attiny87", "attiny88", "attiny828", "attiny841", "attiny861", "attiny861a", "ata5272", "ata6616c", "at86rf401". "avr3" "Classic" devices with 16 KiB up to 64 KiB of program memory. mcu = "at76c711", "at43usb355". "avr31" "Classic" devices with 128 KiB of program memory. mcu = "atmega103", "at43usb320". "avr35" "Classic" devices with 16 KiB up to 64 KiB of program memory and with the "MOVW" instruction. mcu = "attiny167", "attiny1634", "atmega8u2", "atmega16u2", "atmega32u2", "ata5505", "ata6617c", "ata664251", "at90usb82", "at90usb162". "avr4" "Enhanced" devices with up to 8 KiB of program memory. mcu = "atmega48", "atmega48a", "atmega48p", "atmega48pa", "atmega48pb", "atmega8", "atmega8a", "atmega8hva", "atmega88", "atmega88a", "atmega88p", "atmega88pa", "atmega88pb", "atmega8515", "atmega8535", "ata6285", "ata6286", "ata6289", "ata6612c", "at90pwm1", "at90pwm2", "at90pwm2b", "at90pwm3", "at90pwm3b", "at90pwm81". "avr5" "Enhanced" devices with 16 KiB up to 64 KiB of program memory. mcu = "atmega16", "atmega16a", "atmega16hva", "atmega16hva2", "atmega16hvb", "atmega16hvbrevb", "atmega16m1", "atmega16u4", "atmega161", "atmega162", "atmega163", "atmega164a", "atmega164p", "atmega164pa", "atmega165", "atmega165a", "atmega165p", "atmega165pa", "atmega168", "atmega168a", "atmega168p", "atmega168pa", "atmega168pb", "atmega169", "atmega169a", "atmega169p", "atmega169pa", "atmega32", "atmega32a", "atmega32c1", "atmega32hvb", "atmega32hvbrevb", "atmega32m1", "atmega32u4", "atmega32u6", "atmega323", "atmega324a", "atmega324p", "atmega324pa", "atmega324pb", "atmega325", "atmega325a", "atmega325p", "atmega325pa", "atmega328", "atmega328p", "atmega328pb", "atmega329", "atmega329a", "atmega329p", "atmega329pa", "atmega3250", "atmega3250a", "atmega3250p", "atmega3250pa", "atmega3290", "atmega3290a", "atmega3290p", "atmega3290pa", "atmega406", "atmega64", "atmega64a", "atmega64c1", "atmega64hve", "atmega64hve2", "atmega64m1", "atmega64rfr2", "atmega640", "atmega644", "atmega644a", "atmega644p", "atmega644pa", "atmega644rfr2", "atmega645", "atmega645a", "atmega645p", "atmega649", "atmega649a", "atmega649p", "atmega6450", "atmega6450a", "atmega6450p", "atmega6490", "atmega6490a", "atmega6490p", "ata5795", "ata5790", "ata5790n", "ata5791", "ata6613c", "ata6614q", "ata5782", "ata5831", "ata8210", "ata8510", "ata5702m322", "at90pwm161", "at90pwm216", "at90pwm316", "at90can32", "at90can64", "at90scr100", "at90usb646", "at90usb647", "at94k", "m3000". "avr51" "Enhanced" devices with 128 KiB of program memory. mcu = "atmega128", "atmega128a", "atmega128rfa1", "atmega128rfr2", "atmega1280", "atmega1281", "atmega1284", "atmega1284p", "atmega1284rfr2", "at90can128", "at90usb1286", "at90usb1287". "avr6" "Enhanced" devices with 3-byte PC, i.e. with more than 128 KiB of program memory. mcu = "atmega256rfr2", "atmega2560", "atmega2561", "atmega2564rfr2". "avrxmega2" "XMEGA" devices with more than 8 KiB and up to 64 KiB of program memory. mcu = "atxmega8e5", "atxmega16a4", "atxmega16a4u", "atxmega16c4", "atxmega16d4", "atxmega16e5", "atxmega32a4", "atxmega32a4u", "atxmega32c3", "atxmega32c4", "atxmega32d3", "atxmega32d4", "atxmega32e5", "avr64da28", "avr64da32", "avr64da48", "avr64da64", "avr64db28", "avr64db32", "avr64db48", "avr64db64". "avrxmega3" "XMEGA" devices with up to 64 KiB of combined program memory and RAM, and with program memory visible in the RAM address space. mcu = "attiny202", "attiny204", "attiny212", "attiny214", "attiny402", "attiny404", "attiny406", "attiny412", "attiny414", "attiny416", "attiny417", "attiny804", "attiny806", "attiny807", "attiny814", "attiny816", "attiny817", "attiny1604", "attiny1606", "attiny1607", "attiny1614", "attiny1616", "attiny1617", "attiny3214", "attiny3216", "attiny3217", "atmega808", "atmega809", "atmega1608", "atmega1609", "atmega3208", "atmega3209", "atmega4808", "atmega4809", "avr32da28", "avr32da32", "avr32da48", "avr32db28", "avr32db32", "avr32db48". "avrxmega4" "XMEGA" devices with more than 64 KiB and up to 128 KiB of program memory. mcu = "atxmega64a3", "atxmega64a3u", "atxmega64a4u", "atxmega64b1", "atxmega64b3", "atxmega64c3", "atxmega64d3", "atxmega64d4", "avr128da28", "avr128da32", "avr128da48", "avr128da64", "avr128db28", "avr128db32", "avr128db48", "avr128db64". "avrxmega5" "XMEGA" devices with more than 64 KiB and up to 128 KiB of program memory and more than 64 KiB of RAM. mcu = "atxmega64a1", "atxmega64a1u". "avrxmega6" "XMEGA" devices with more than 128 KiB of program memory. mcu = "atxmega128a3", "atxmega128a3u", "atxmega128b1", "atxmega128b3", "atxmega128c3", "atxmega128d3", "atxmega128d4", "atxmega192a3", "atxmega192a3u", "atxmega192c3", "atxmega192d3", "atxmega256a3", "atxmega256a3b", "atxmega256a3bu", "atxmega256a3u", "atxmega256c3", "atxmega256d3", "atxmega384c3", "atxmega384d3". "avrxmega7" "XMEGA" devices with more than 128 KiB of program memory and more than 64 KiB of RAM. mcu = "atxmega128a1", "atxmega128a1u", "atxmega128a4u". "avrtiny" "TINY" Tiny core devices with 512 B up to 4 KiB of program memory. mcu = "attiny4", "attiny5", "attiny9", "attiny10", "attiny20", "attiny40". "avr1" This ISA is implemented by the minimal AVR core and supported for assembler only. mcu = "attiny11", "attiny12", "attiny15", "attiny28", "at90s1200". -mabsdata Assume that all data in static storage can be accessed by LDS / STS instructions. This option has only an effect on reduced Tiny devices like ATtiny40. See also the "absdata" AVR Variable Attributes,variable attribute. -maccumulate-args Accumulate outgoing function arguments and acquire/release the needed stack space for outgoing function arguments once in function prologue/epilogue. Without this option, outgoing arguments are pushed before calling a function and popped afterwards. Popping the arguments after the function call can be expensive on AVR so that accumulating the stack space might lead to smaller executables because arguments need not be removed from the stack after such a function call. This option can lead to reduced code size for functions that perform several calls to functions that get their arguments on the stack like calls to printf-like functions. -mbranch-cost=cost Set the branch costs for conditional branch instructions to cost. Reasonable values for cost are small, non-negative integers. The default branch cost is 0. -mcall-prologues Functions prologues/epilogues are expanded as calls to appropriate subroutines. Code size is smaller. -mdouble=bits -mlong-double=bits Set the size (in bits) of the "double" or "long double" type, respectively. Possible values for bits are 32 and 64. Whether or not a specific value for bits is allowed depends on the "--with-double=" and "--with-long-double=" configure options ("https://gcc.gnu.org/install/configure.html#avr"), and the same applies for the default values of the options. -mgas-isr-prologues Interrupt service routines (ISRs) may use the "__gcc_isr" pseudo instruction supported by GNU Binutils. If this option is on, the feature can still be disabled for individual ISRs by means of the AVR Function Attributes,,"no_gccisr" function attribute. This feature is activated per default if optimization is on (but not with -Og, @pxref{Optimize Options}), and if GNU Binutils support PR21683 ("https://sourceware.org/PR21683"). -mint8 Assume "int" to be 8-bit integer. This affects the sizes of all types: a "char" is 1 byte, an "int" is 1 byte, a "long" is 2 bytes, and "long long" is 4 bytes. Please note that this option does not conform to the C standards, but it results in smaller code size. -mmain-is-OS_task Do not save registers in "main". The effect is the same like attaching attribute AVR Function Attributes,,"OS_task" to "main". It is activated per default if optimization is on. -mn-flash=num Assume that the flash memory has a size of num times 64 KiB. -mno-interrupts Generated code is not compatible with hardware interrupts. Code size is smaller. -mrelax Try to replace "CALL" resp. "JMP" instruction by the shorter "RCALL" resp. "RJMP" instruction if applicable. Setting -mrelax just adds the --mlink-relax option to the assembler's command line and the --relax option to the linker's command line. Jump relaxing is performed by the linker because jump offsets are not known before code is located. Therefore, the assembler code generated by the compiler is the same, but the instructions in the executable may differ from instructions in the assembler code. Relaxing must be turned on if linker stubs are needed, see the section on "EIND" and linker stubs below. -mrmw Assume that the device supports the Read-Modify-Write instructions "XCH", "LAC", "LAS" and "LAT". -mshort-calls Assume that "RJMP" and "RCALL" can target the whole program memory. This option is used internally for multilib selection. It is not an optimization option, and you don't need to set it by hand. -msp8 Treat the stack pointer register as an 8-bit register, i.e. assume the high byte of the stack pointer is zero. In general, you don't need to set this option by hand. This option is used internally by the compiler to select and build multilibs for architectures "avr2" and "avr25". These architectures mix devices with and without "SPH". For any setting other than -mmcu=avr2 or -mmcu=avr25 the compiler driver adds or removes this option from the compiler proper's command line, because the compiler then knows if the device or architecture has an 8-bit stack pointer and thus no "SPH" register or not. -mstrict-X Use address register "X" in a way proposed by the hardware. This means that "X" is only used in indirect, post-increment or pre- decrement addressing. Without this option, the "X" register may be used in the same way as "Y" or "Z" which then is emulated by additional instructions. For example, loading a value with "X+const" addressing with a small non-negative "const < 64" to a register Rn is performed as adiw r26, const ; X += const ld <Rn>, X ; <Rn> = *X sbiw r26, const ; X -= const -mtiny-stack Only change the lower 8 bits of the stack pointer. -mfract-convert-truncate Allow to use truncation instead of rounding towards zero for fractional fixed-point types. -nodevicelib Don't link against AVR-LibC's device specific library "lib<mcu>.a". -nodevicespecs Don't add -specs=device-specs/specs-mcu to the compiler driver's command line. The user takes responsibility for supplying the sub- processes like compiler proper, assembler and linker with appropriate command line options. This means that the user has to supply her private device specs file by means of -specs=path-to- specs-file. There is no more need for option -mmcu=mcu. This option can also serve as a replacement for the older way of specifying custom device-specs files that needed -B some-path to point to a directory which contains a folder named "device-specs" which contains a specs file named "specs-mcu", where mcu was specified by -mmcu=mcu. -Waddr-space-convert Warn about conversions between address spaces in the case where the resulting address space is not contained in the incoming address space. -Wmisspelled-isr Warn if the ISR is misspelled, i.e. without __vector prefix. Enabled by default. "EIND" and Devices with More Than 128 Ki Bytes of Flash Pointers in the implementation are 16 bits wide. The address of a function or label is represented as word address so that indirect jumps and calls can target any code address in the range of 64 Ki words. In order to facilitate indirect jump on devices with more than 128 Ki bytes of program memory space, there is a special function register called "EIND" that serves as most significant part of the target address when "EICALL" or "EIJMP" instructions are used. Indirect jumps and calls on these devices are handled as follows by the compiler and are subject to some limitations: * The compiler never sets "EIND". * The compiler uses "EIND" implicitly in "EICALL"/"EIJMP" instructions or might read "EIND" directly in order to emulate an indirect call/jump by means of a "RET" instruction. * The compiler assumes that "EIND" never changes during the startup code or during the application. In particular, "EIND" is not saved/restored in function or interrupt service routine prologue/epilogue. * For indirect calls to functions and computed goto, the linker generates stubs. Stubs are jump pads sometimes also called trampolines. Thus, the indirect call/jump jumps to such a stub. The stub contains a direct jump to the desired address. * Linker relaxation must be turned on so that the linker generates the stubs correctly in all situations. See the compiler option -mrelax and the linker option --relax. There are corner cases where the linker is supposed to generate stubs but aborts without relaxation and without a helpful error message. * The default linker script is arranged for code with "EIND = 0". If code is supposed to work for a setup with "EIND != 0", a custom linker script has to be used in order to place the sections whose name start with ".trampolines" into the segment where "EIND" points to. * The startup code from libgcc never sets "EIND". Notice that startup code is a blend of code from libgcc and AVR-LibC. For the impact of AVR-LibC on "EIND", see the AVR-LibC user manual ("https://www.nongnu.org/avr-libc/user-manual/"). * It is legitimate for user-specific startup code to set up "EIND" early, for example by means of initialization code located in section ".init3". Such code runs prior to general startup code that initializes RAM and calls constructors, but after the bit of startup code from AVR-LibC that sets "EIND" to the segment where the vector table is located. #include <avr/io.h> static void __attribute__((section(".init3"),naked,used,no_instrument_function)) init3_set_eind (void) { __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t" "out %i0,r24" :: "n" (&EIND) : "r24","memory"); } The "__trampolines_start" symbol is defined in the linker script. * Stubs are generated automatically by the linker if the following two conditions are met: -<The address of a label is taken by means of the "gs" modifier> (short for generate stubs) like so: LDI r24, lo8(gs(<func>)) LDI r25, hi8(gs(<func>)) -<The final location of that label is in a code segment> outside the segment where the stubs are located. * The compiler emits such "gs" modifiers for code labels in the following situations: -<Taking address of a function or code label.> -<Computed goto.> -<If prologue-save function is used, see -mcall-prologues> command-line option. -<Switch/case dispatch tables. If you do not want such dispatch> tables you can specify the -fno-jump-tables command-line option. -<C and C++ constructors/destructors called during startup/shutdown.> -<If the tools hit a "gs()" modifier explained above.> * Jumping to non-symbolic addresses like so is not supported: int main (void) { /* Call function at word address 0x2 */ return ((int(*)(void)) 0x2)(); } Instead, a stub has to be set up, i.e. the function has to be called through a symbol ("func_4" in the example): int main (void) { extern int func_4 (void); /* Call function at byte address 0x4 */ return func_4(); } and the application be linked with -Wl,--defsym,func_4=0x4. Alternatively, "func_4" can be defined in the linker script. Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special Function Registers Some AVR devices support memories larger than the 64 KiB range that can be accessed with 16-bit pointers. To access memory locations outside this 64 KiB range, the content of a "RAMP" register is used as high part of the address: The "X", "Y", "Z" address register is concatenated with the "RAMPX", "RAMPY", "RAMPZ" special function register, respectively, to get a wide address. Similarly, "RAMPD" is used together with direct addressing. * The startup code initializes the "RAMP" special function registers with zero. * If a AVR Named Address Spaces,named address space other than generic or "__flash" is used, then "RAMPZ" is set as needed before the operation. * If the device supports RAM larger than 64 KiB and the compiler needs to change "RAMPZ" to accomplish an operation, "RAMPZ" is reset to zero after the operation. * If the device comes with a specific "RAMP" register, the ISR prologue/epilogue saves/restores that SFR and initializes it with zero in case the ISR code might (implicitly) use it. * RAM larger than 64 KiB is not supported by GCC for AVR targets. If you use inline assembler to read from locations outside the 16-bit address range and change one of the "RAMP" registers, you must reset it to zero after the access. AVR Built-in Macros GCC defines several built-in macros so that the user code can test for the presence or absence of features. Almost any of the following built-in macros are deduced from device capabilities and thus triggered by the -mmcu= command-line option. For even more AVR-specific built-in macros see AVR Named Address Spaces and AVR Built-in Functions. "__AVR_ARCH__" Build-in macro that resolves to a decimal number that identifies the architecture and depends on the -mmcu=mcu option. Possible values are: 2, 25, 3, 31, 35, 4, 5, 51, 6 for mcu="avr2", "avr25", "avr3", "avr31", "avr35", "avr4", "avr5", "avr51", "avr6", respectively and 100, 102, 103, 104, 105, 106, 107 for mcu="avrtiny", "avrxmega2", "avrxmega3", "avrxmega4", "avrxmega5", "avrxmega6", "avrxmega7", respectively. If mcu specifies a device, this built-in macro is set accordingly. For example, with -mmcu=atmega8 the macro is defined to 4. "__AVR_Device__" Setting -mmcu=device defines this built-in macro which reflects the device's name. For example, -mmcu=atmega8 defines the built-in macro "__AVR_ATmega8__", -mmcu=attiny261a defines "__AVR_ATtiny261A__", etc. The built-in macros' names follow the scheme "__AVR_Device__" where Device is the device name as from the AVR user manual. The difference between Device in the built-in macro and device in -mmcu=device is that the latter is always lowercase. If device is not a device but only a core architecture like avr51, this macro is not defined. "__AVR_DEVICE_NAME__" Setting -mmcu=device defines this built-in macro to the device's name. For example, with -mmcu=atmega8 the macro is defined to "atmega8". If device is not a device but only a core architecture like avr51, this macro is not defined. "__AVR_XMEGA__" The device / architecture belongs to the XMEGA family of devices. "__AVR_HAVE_ELPM__" The device has the "ELPM" instruction. "__AVR_HAVE_ELPMX__" The device has the "ELPM Rn,Z" and "ELPM Rn,Z+" instructions. "__AVR_HAVE_MOVW__" The device has the "MOVW" instruction to perform 16-bit register- register moves. "__AVR_HAVE_LPMX__" The device has the "LPM Rn,Z" and "LPM Rn,Z+" instructions. "__AVR_HAVE_MUL__" The device has a hardware multiplier. "__AVR_HAVE_JMP_CALL__" The device has the "JMP" and "CALL" instructions. This is the case for devices with more than 8 KiB of program memory. "__AVR_HAVE_EIJMP_EICALL__" "__AVR_3_BYTE_PC__" The device has the "EIJMP" and "EICALL" instructions. This is the case for devices with more than 128 KiB of program memory. This also means that the program counter (PC) is 3 bytes wide. "__AVR_2_BYTE_PC__" The program counter (PC) is 2 bytes wide. This is the case for devices with up to 128 KiB of program memory. "__AVR_HAVE_8BIT_SP__" "__AVR_HAVE_16BIT_SP__" The stack pointer (SP) register is treated as 8-bit respectively 16-bit register by the compiler. The definition of these macros is affected by -mtiny-stack. "__AVR_HAVE_SPH__" "__AVR_SP8__" The device has the SPH (high part of stack pointer) special function register or has an 8-bit stack pointer, respectively. The definition of these macros is affected by -mmcu= and in the cases of -mmcu=avr2 and -mmcu=avr25 also by -msp8. "__AVR_HAVE_RAMPD__" "__AVR_HAVE_RAMPX__" "__AVR_HAVE_RAMPY__" "__AVR_HAVE_RAMPZ__" The device has the "RAMPD", "RAMPX", "RAMPY", "RAMPZ" special function register, respectively. "__NO_INTERRUPTS__" This macro reflects the -mno-interrupts command-line option. "__AVR_ERRATA_SKIP__" "__AVR_ERRATA_SKIP_JMP_CALL__" Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit instructions because of a hardware erratum. Skip instructions are "SBRS", "SBRC", "SBIS", "SBIC" and "CPSE". The second macro is only defined if "__AVR_HAVE_JMP_CALL__" is also set. "__AVR_ISA_RMW__" The device has Read-Modify-Write instructions (XCH, LAC, LAS and LAT). "__AVR_SFR_OFFSET__=offset" Instructions that can address I/O special function registers directly like "IN", "OUT", "SBI", etc. may use a different address as if addressed by an instruction to access RAM like "LD" or "STS". This offset depends on the device architecture and has to be subtracted from the RAM address in order to get the respective I/O address. "__AVR_SHORT_CALLS__" The -mshort-calls command line option is set. "__AVR_PM_BASE_ADDRESS__=addr" Some devices support reading from flash memory by means of "LD*" instructions. The flash memory is seen in the data address space at an offset of "__AVR_PM_BASE_ADDRESS__". If this macro is not defined, this feature is not available. If defined, the address space is linear and there is no need to put ".rodata" into RAM. This is handled by the default linker description file, and is currently available for "avrtiny" and "avrxmega3". Even more convenient, there is no need to use address spaces like "__flash" or features like attribute "progmem" and "pgm_read_*". "__WITH_AVRLIBC__" The compiler is configured to be used together with AVR-Libc. See the --with-avrlibc configure option. "__HAVE_DOUBLE_MULTILIB__" Defined if -mdouble= acts as a multilib option. "__HAVE_DOUBLE32__" "__HAVE_DOUBLE64__" Defined if the compiler supports 32-bit double resp. 64-bit double. The actual layout is specified by option -mdouble=. "__DEFAULT_DOUBLE__" The size in bits of "double" if -mdouble= is not set. To test the layout of "double" in a program, use the built-in macro "__SIZEOF_DOUBLE__". "__HAVE_LONG_DOUBLE32__" "__HAVE_LONG_DOUBLE64__" "__HAVE_LONG_DOUBLE_MULTILIB__" "__DEFAULT_LONG_DOUBLE__" Same as above, but for "long double" instead of "double". "__WITH_DOUBLE_COMPARISON__" Reflects the "--with-double-comparison={tristate|bool|libf7}" configure option ("https://gcc.gnu.org/install/configure.html#avr") and is defined to 2 or 3. "__WITH_LIBF7_LIBGCC__" "__WITH_LIBF7_MATH__" "__WITH_LIBF7_MATH_SYMBOLS__" Reflects the "--with-libf7={libgcc|math|math-symbols}" configure option ("https://gcc.gnu.org/install/configure.html#avr"). Blackfin Options -mcpu=cpu[-sirevision] Specifies the name of the target Blackfin processor. Currently, cpu can be one of bf512, bf514, bf516, bf518, bf522, bf523, bf524, bf525, bf526, bf527, bf531, bf532, bf533, bf534, bf536, bf537, bf538, bf539, bf542, bf544, bf547, bf548, bf549, bf542m, bf544m, bf547m, bf548m, bf549m, bf561, bf592. The optional sirevision specifies the silicon revision of the target Blackfin processor. Any workarounds available for the targeted silicon revision are enabled. If sirevision is none, no workarounds are enabled. If sirevision is any, all workarounds for the targeted processor are enabled. The "__SILICON_REVISION__" macro is defined to two hexadecimal digits representing the major and minor numbers in the silicon revision. If sirevision is none, the "__SILICON_REVISION__" is not defined. If sirevision is any, the "__SILICON_REVISION__" is defined to be 0xffff. If this optional sirevision is not used, GCC assumes the latest known silicon revision of the targeted Blackfin processor. GCC defines a preprocessor macro for the specified cpu. For the bfin-elf toolchain, this option causes the hardware BSP provided by libgloss to be linked in if -msim is not given. Without this option, bf532 is used as the processor by default. Note that support for bf561 is incomplete. For bf561, only the preprocessor macro is defined. -msim Specifies that the program will be run on the simulator. This causes the simulator BSP provided by libgloss to be linked in. This option has effect only for bfin-elf toolchain. Certain other options, such as -mid-shared-library and -mfdpic, imply -msim. -momit-leaf-frame-pointer Don't keep the frame pointer in a register for leaf functions. This avoids the instructions to save, set up and restore frame pointers and makes an extra register available in leaf functions. -mspecld-anomaly When enabled, the compiler ensures that the generated code does not contain speculative loads after jump instructions. If this option is used, "__WORKAROUND_SPECULATIVE_LOADS" is defined. -mno-specld-anomaly Don't generate extra code to prevent speculative loads from occurring. -mcsync-anomaly When enabled, the compiler ensures that the generated code does not contain CSYNC or SSYNC instructions too soon after conditional branches. If this option is used, "__WORKAROUND_SPECULATIVE_SYNCS" is defined. -mno-csync-anomaly Don't generate extra code to prevent CSYNC or SSYNC instructions from occurring too soon after a conditional branch. -mlow64k When enabled, the compiler is free to take advantage of the knowledge that the entire program fits into the low 64k of memory. -mno-low64k Assume that the program is arbitrarily large. This is the default. -mstack-check-l1 Do stack checking using information placed into L1 scratchpad memory by the uClinux kernel. -mid-shared-library Generate code that supports shared libraries via the library ID method. This allows for execute in place and shared libraries in an environment without virtual memory management. This option implies -fPIC. With a bfin-elf target, this option implies -msim. -mno-id-shared-library Generate code that doesn't assume ID-based shared libraries are being used. This is the default. -mleaf-id-shared-library Generate code that supports shared libraries via the library ID method, but assumes that this library or executable won't link against any other ID shared libraries. That allows the compiler to use faster code for jumps and calls. -mno-leaf-id-shared-library Do not assume that the code being compiled won't link against any ID shared libraries. Slower code is generated for jump and call insns. -mshared-library-id=n Specifies the identification number of the ID-based shared library being compiled. Specifying a value of 0 generates more compact code; specifying other values forces the allocation of that number to the current library but is no more space- or time-efficient than omitting this option. -msep-data Generate code that allows the data segment to be located in a different area of memory from the text segment. This allows for execute in place in an environment without virtual memory management by eliminating relocations against the text section. -mno-sep-data Generate code that assumes that the data segment follows the text segment. This is the default. -mlong-calls -mno-long-calls Tells the compiler to perform function calls by first loading the address of the function into a register and then performing a subroutine call on this register. This switch is needed if the target function lies outside of the 24-bit addressing range of the offset-based version of subroutine call instruction. This feature is not enabled by default. Specifying -mno-long-calls restores the default behavior. Note these switches have no effect on how the compiler generates code to handle function calls via function pointers. -mfast-fp Link with the fast floating-point library. This library relaxes some of the IEEE floating-point standard's rules for checking inputs against Not-a-Number (NAN), in the interest of performance. -minline-plt Enable inlining of PLT entries in function calls to functions that are not known to bind locally. It has no effect without -mfdpic. -mmulticore Build a standalone application for multicore Blackfin processors. This option causes proper start files and link scripts supporting multicore to be used, and defines the macro "__BFIN_MULTICORE". It can only be used with -mcpu=bf561[-sirevision]. This option can be used with -mcorea or -mcoreb, which selects the one-application-per-core programming model. Without -mcorea or -mcoreb, the single-application/dual-core programming model is used. In this model, the main function of Core B should be named as "coreb_main". If this option is not used, the single-core application programming model is used. -mcorea Build a standalone application for Core A of BF561 when using the one-application-per-core programming model. Proper start files and link scripts are used to support Core A, and the macro "__BFIN_COREA" is defined. This option can only be used in conjunction with -mmulticore. -mcoreb Build a standalone application for Core B of BF561 when using the one-application-per-core programming model. Proper start files and link scripts are used to support Core B, and the macro "__BFIN_COREB" is defined. When this option is used, "coreb_main" should be used instead of "main". This option can only be used in conjunction with -mmulticore. -msdram Build a standalone application for SDRAM. Proper start files and link scripts are used to put the application into SDRAM, and the macro "__BFIN_SDRAM" is defined. The loader should initialize SDRAM before loading the application. -micplb Assume that ICPLBs are enabled at run time. This has an effect on certain anomaly workarounds. For Linux targets, the default is to assume ICPLBs are enabled; for standalone applications the default is off. C6X Options -march=name This specifies the name of the target architecture. GCC uses this name to determine what kind of instructions it can emit when generating assembly code. Permissible names are: c62x, c64x, c64x+, c67x, c67x+, c674x. -mbig-endian Generate code for a big-endian target. -mlittle-endian Generate code for a little-endian target. This is the default. -msim Choose startup files and linker script suitable for the simulator. -msdata=default Put small global and static data in the ".neardata" section, which is pointed to by register "B14". Put small uninitialized global and static data in the ".bss" section, which is adjacent to the ".neardata" section. Put small read-only data into the ".rodata" section. The corresponding sections used for large pieces of data are ".fardata", ".far" and ".const". -msdata=all Put all data, not just small objects, into the sections reserved for small data, and use addressing relative to the "B14" register to access them. -msdata=none Make no use of the sections reserved for small data, and use absolute addresses to access all data. Put all initialized global and static data in the ".fardata" section, and all uninitialized data in the ".far" section. Put all constant data into the ".const" section. CRIS Options These options are defined specifically for the CRIS ports. -march=architecture-type -mcpu=architecture-type Generate code for the specified architecture. The choices for architecture-type are v3, v8 and v10 for respectively ETRAX 4, ETRAX 100, and ETRAX 100 LX. Default is v0. -mtune=architecture-type Tune to architecture-type everything applicable about the generated code, except for the ABI and the set of available instructions. The choices for architecture-type are the same as for -march=architecture-type. -mmax-stack-frame=n Warn when the stack frame of a function exceeds n bytes. -metrax4 -metrax100 The options -metrax4 and -metrax100 are synonyms for -march=v3 and -march=v8 respectively. -mmul-bug-workaround -mno-mul-bug-workaround Work around a bug in the "muls" and "mulu" instructions for CPU models where it applies. This option is disabled by default. -mpdebug Enable CRIS-specific verbose debug-related information in the assembly code. This option also has the effect of turning off the #NO_APP formatted-code indicator to the assembler at the beginning of the assembly file. -mcc-init Do not use condition-code results from previous instruction; always emit compare and test instructions before use of condition codes. -mno-side-effects Do not emit instructions with side effects in addressing modes other than post-increment. -mstack-align -mno-stack-align -mdata-align -mno-data-align -mconst-align -mno-const-align These options (no- options) arrange (eliminate arrangements) for the stack frame, individual data and constants to be aligned for the maximum single data access size for the chosen CPU model. The default is to arrange for 32-bit alignment. ABI details such as structure layout are not affected by these options. -m32-bit -m16-bit -m8-bit Similar to the stack- data- and const-align options above, these options arrange for stack frame, writable data and constants to all be 32-bit, 16-bit or 8-bit aligned. The default is 32-bit alignment. -mno-prologue-epilogue -mprologue-epilogue With -mno-prologue-epilogue, the normal function prologue and epilogue which set up the stack frame are omitted and no return instructions or return sequences are generated in the code. Use this option only together with visual inspection of the compiled code: no warnings or errors are generated when call-saved registers must be saved, or storage for local variables needs to be allocated. -melf Legacy no-op option. -sim This option arranges to link with input-output functions from a simulator library. Code, initialized data and zero-initialized data are allocated consecutively. -sim2 Like -sim, but pass linker options to locate initialized data at 0x40000000 and zero-initialized data at 0x80000000. C-SKY Options GCC supports these options when compiling for C-SKY V2 processors. -march=arch Specify the C-SKY target architecture. Valid values for arch are: ck801, ck802, ck803, ck807, and ck810. The default is ck810. -mcpu=cpu Specify the C-SKY target processor. Valid values for cpu are: ck801, ck801t, ck802, ck802t, ck802j, ck803, ck803h, ck803t, ck803ht, ck803f, ck803fh, ck803e, ck803eh, ck803et, ck803eht, ck803ef, ck803efh, ck803ft, ck803eft, ck803efht, ck803r1, ck803hr1, ck803tr1, ck803htr1, ck803fr1, ck803fhr1, ck803er1, ck803ehr1, ck803etr1, ck803ehtr1, ck803efr1, ck803efhr1, ck803ftr1, ck803eftr1, ck803efhtr1, ck803s, ck803st, ck803se, ck803sf, ck803sef, ck803seft, ck807e, ck807ef, ck807, ck807f, ck810e, ck810et, ck810ef, ck810eft, ck810, ck810v, ck810f, ck810t, ck810fv, ck810tv, ck810ft, and ck810ftv. -mbig-endian -EB -mlittle-endian -EL Select big- or little-endian code. The default is little-endian. -mfloat-abi=name Specifies which floating-point ABI to use. Permissible values are: soft, softfp and hard. Specifying soft causes GCC to generate output containing library calls for floating-point operations. softfp allows the generation of code using hardware floating-point instructions, but still uses the soft-float calling conventions. hard allows generation of floating-point instructions and uses FPU-specific calling conventions. The default depends on the specific target configuration. Note that the hard-float and soft-float ABIs are not link-compatible; you must compile your entire program with the same ABI, and link with a compatible set of libraries. -mhard-float -msoft-float Select hardware or software floating-point implementations. The default is soft float. -mdouble-float -mno-double-float When -mhard-float is in effect, enable generation of double- precision float instructions. This is the default except when compiling for CK803. -mfdivdu -mno-fdivdu When -mhard-float is in effect, enable generation of "frecipd", "fsqrtd", and "fdivd" instructions. This is the default except when compiling for CK803. -mfpu=fpu Select the floating-point processor. This option can only be used with -mhard-float. Values for fpu are fpv2_sf (equivalent to -mno-double-float -mno-fdivdu), fpv2 (-mdouble-float -mno-divdu), and fpv2_divd (-mdouble-float -mdivdu). -melrw -mno-elrw Enable the extended "lrw" instruction. This option defaults to on for CK801 and off otherwise. -mistack -mno-istack Enable interrupt stack instructions; the default is off. The -mistack option is required to handle the "interrupt" and "isr" function attributes. -mmp Enable multiprocessor instructions; the default is off. -mcp Enable coprocessor instructions; the default is off. -mcache Enable coprocessor instructions; the default is off. -msecurity Enable C-SKY security instructions; the default is off. -mtrust Enable C-SKY trust instructions; the default is off. -mdsp -medsp -mvdsp Enable C-SKY DSP, Enhanced DSP, or Vector DSP instructions, respectively. All of these options default to off. -mdiv -mno-div Generate divide instructions. Default is off. -msmart -mno-smart Generate code for Smart Mode, using only registers numbered 0-7 to allow use of 16-bit instructions. This option is ignored for CK801 where this is the required behavior, and it defaults to on for CK802. For other targets, the default is off. -mhigh-registers -mno-high-registers Generate code using the high registers numbered 16-31. This option is not supported on CK801, CK802, or CK803, and is enabled by default for other processors. -manchor -mno-anchor Generate code using global anchor symbol addresses. -mpushpop -mno-pushpop Generate code using "push" and "pop" instructions. This option defaults to on. -mmultiple-stld -mstm -mno-multiple-stld -mno-stm Generate code using "stm" and "ldm" instructions. This option isn't supported on CK801 but is enabled by default on other processors. -mconstpool -mno-constpool Create constant pools in the compiler instead of deferring it to the assembler. This option is the default and required for correct code generation on CK801 and CK802, and is optional on other processors. -mstack-size -mno-stack-size Emit ".stack_size" directives for each function in the assembly output. This option defaults to off. -mccrt -mno-ccrt Generate code for the C-SKY compiler runtime instead of libgcc. This option defaults to off. -mbranch-cost=n Set the branch costs to roughly "n" instructions. The default is 1. -msched-prolog -mno-sched-prolog Permit scheduling of function prologue and epilogue sequences. Using this option can result in code that is not compliant with the C-SKY V2 ABI prologue requirements and that cannot be debugged or backtraced. It is disabled by default. -msim Links the library libsemi.a which is in compatible with simulator. Applicable to ELF compiler only. Darwin Options These options are defined for all architectures running the Darwin operating system. FSF GCC on Darwin does not create "fat" object files; it creates an object file for the single architecture that GCC was built to target. Apple's GCC on Darwin does create "fat" files if multiple -arch options are used; it does so by running the compiler or linker multiple times and joining the results together with lipo. The subtype of the file created (like ppc7400 or ppc970 or i686) is determined by the flags that specify the ISA that GCC is targeting, like -mcpu or -march. The -force_cpusubtype_ALL option can be used to override this. The Darwin tools vary in their behavior when presented with an ISA mismatch. The assembler, as, only permits instructions to be used that are valid for the subtype of the file it is generating, so you cannot put 64-bit instructions in a ppc750 object file. The linker for shared libraries, /usr/bin/libtool, fails and prints an error if asked to create a shared library with a less restrictive subtype than its input files (for instance, trying to put a ppc970 object file in a ppc7400 library). The linker for executables, ld, quietly gives the executable the most restrictive subtype of any of its input files. -Fdir Add the framework directory dir to the head of the list of directories to be searched for header files. These directories are interleaved with those specified by -I options and are scanned in a left-to-right order. A framework directory is a directory with frameworks in it. A framework is a directory with a Headers and/or PrivateHeaders directory contained directly in it that ends in .framework. The name of a framework is the name of this directory excluding the .framework. Headers associated with the framework are found in one of those two directories, with Headers being searched first. A subframework is a framework directory that is in a framework's Frameworks directory. Includes of subframework headers can only appear in a header of a framework that contains the subframework, or in a sibling subframework header. Two subframeworks are siblings if they occur in the same framework. A subframework should not have the same name as a framework; a warning is issued if this is violated. Currently a subframework cannot have subframeworks; in the future, the mechanism may be extended to support this. The standard frameworks can be found in /System/Library/Frameworks and /Library/Frameworks. An example include looks like "#include <Framework/header.h>", where Framework denotes the name of the framework and header.h is found in the PrivateHeaders or Headers directory. -iframeworkdir Like -F except the directory is a treated as a system directory. The main difference between this -iframework and -F is that with -iframework the compiler does not warn about constructs contained within header files found via dir. This option is valid only for the C family of languages. -gused Emit debugging information for symbols that are used. For stabs debugging format, this enables -feliminate-unused-debug-symbols. This is by default ON. -gfull Emit debugging information for all symbols and types. -fconstant-cfstrings The -fconstant-cfstrings is an alias for -mconstant-cfstrings. -mconstant-cfstrings When the NeXT runtime is being used (the default on these systems), override any -fconstant-string-class setting and cause "@"..."" literals to be laid out as constant CoreFoundation strings. -mmacosx-version-min=version The earliest version of MacOS X that this executable will run on is version. Typical values supported for version include 12, 10.12, and 10.5.8. If the compiler was built to use the system's headers by default, then the default for this option is the system version on which the compiler is running, otherwise the default is to make choices that are compatible with as many systems and code bases as possible. -mkernel Enable kernel development mode. The -mkernel option sets -static, -fno-common, -fno-use-cxa-atexit, -fno-exceptions, -fno-non-call-exceptions, -fapple-kext, -fno-weak and -fno-rtti where applicable. This mode also sets -mno-altivec, -msoft-float, -fno-builtin and -mlong-branch for PowerPC targets. -mone-byte-bool Override the defaults for "bool" so that "sizeof(bool)==1". By default "sizeof(bool)" is 4 when compiling for Darwin/PowerPC and 1 when compiling for Darwin/x86, so this option has no effect on x86. Warning: The -mone-byte-bool switch causes GCC to generate code that is not binary compatible with code generated without that switch. Using this switch may require recompiling all other modules in a program, including system libraries. Use this switch to conform to a non-default data model. -mfix-and-continue -ffix-and-continue -findirect-data Generate code suitable for fast turnaround development, such as to allow GDB to dynamically load .o files into already-running programs. -findirect-data and -ffix-and-continue are provided for backwards compatibility. -all_load Loads all members of static archive libraries. See man ld(1) for more information. -arch_errors_fatal Cause the errors having to do with files that have the wrong architecture to be fatal. -bind_at_load Causes the output file to be marked such that the dynamic linker will bind all undefined references when the file is loaded or launched. -bundle Produce a Mach-o bundle format file. See man ld(1) for more information. -bundle_loader executable This option specifies the executable that will load the build output file being linked. See man ld(1) for more information. -dynamiclib When passed this option, GCC produces a dynamic library instead of an executable when linking, using the Darwin libtool command. -force_cpusubtype_ALL This causes GCC's output file to have the ALL subtype, instead of one controlled by the -mcpu or -march option. -allowable_client client_name -client_name -compatibility_version -current_version -dead_strip -dependency-file -dylib_file -dylinker_install_name -dynamic -exported_symbols_list -filelist -flat_namespace -force_flat_namespace -headerpad_max_install_names -image_base -init -install_name -keep_private_externs -multi_module -multiply_defined -multiply_defined_unused -noall_load -no_dead_strip_inits_and_terms -nofixprebinding -nomultidefs -noprebind -noseglinkedit -pagezero_size -prebind -prebind_all_twolevel_modules -private_bundle -read_only_relocs -sectalign -sectobjectsymbols -whyload -seg1addr -sectcreate -sectobjectsymbols -sectorder -segaddr -segs_read_only_addr -segs_read_write_addr -seg_addr_table -seg_addr_table_filename -seglinkedit -segprot -segs_read_only_addr -segs_read_write_addr -single_module -static -sub_library -sub_umbrella -twolevel_namespace -umbrella -undefined -unexported_symbols_list -weak_reference_mismatches -whatsloaded These options are passed to the Darwin linker. The Darwin linker man page describes them in detail. DEC Alpha Options These -m options are defined for the DEC Alpha implementations: -mno-soft-float -msoft-float Use (do not use) the hardware floating-point instructions for floating-point operations. When -msoft-float is specified, functions in libgcc.a are used to perform floating-point operations. Unless they are replaced by routines that emulate the floating-point operations, or compiled in such a way as to call such emulations routines, these routines issue floating-point operations. If you are compiling for an Alpha without floating- point operations, you must ensure that the library is built so as not to call them. Note that Alpha implementations without floating-point operations are required to have floating-point registers. -mfp-reg -mno-fp-regs Generate code that uses (does not use) the floating-point register set. -mno-fp-regs implies -msoft-float. If the floating-point register set is not used, floating-point operands are passed in integer registers as if they were integers and floating-point results are passed in $0 instead of $f0. This is a non-standard calling sequence, so any function with a floating-point argument or return value called by code compiled with -mno-fp-regs must also be compiled with that option. A typical use of this option is building a kernel that does not use, and hence need not save and restore, any floating-point registers. -mieee The Alpha architecture implements floating-point hardware optimized for maximum performance. It is mostly compliant with the IEEE floating-point standard. However, for full compliance, software assistance is required. This option generates code fully IEEE- compliant code except that the inexact-flag is not maintained (see below). If this option is turned on, the preprocessor macro "_IEEE_FP" is defined during compilation. The resulting code is less efficient but is able to correctly support denormalized numbers and exceptional IEEE values such as not-a-number and plus/minus infinity. Other Alpha compilers call this option -ieee_with_no_inexact. -mieee-with-inexact This is like -mieee except the generated code also maintains the IEEE inexact-flag. Turning on this option causes the generated code to implement fully-compliant IEEE math. In addition to "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor macro. On some Alpha implementations the resulting code may execute significantly slower than the code generated by default. Since there is very little code that depends on the inexact-flag, you should normally not specify this option. Other Alpha compilers call this option -ieee_with_inexact. -mfp-trap-mode=trap-mode This option controls what floating-point related traps are enabled. Other Alpha compilers call this option -fptm trap-mode. The trap mode can be set to one of four values: n This is the default (normal) setting. The only traps that are enabled are the ones that cannot be disabled in software (e.g., division by zero trap). u In addition to the traps enabled by n, underflow traps are enabled as well. su Like u, but the instructions are marked to be safe for software completion (see Alpha architecture manual for details). sui Like su, but inexact traps are enabled as well. -mfp-rounding-mode=rounding-mode Selects the IEEE rounding mode. Other Alpha compilers call this option -fprm rounding-mode. The rounding-mode can be one of: n Normal IEEE rounding mode. Floating-point numbers are rounded towards the nearest machine number or towards the even machine number in case of a tie. m Round towards minus infinity. c Chopped rounding mode. Floating-point numbers are rounded towards zero. d Dynamic rounding mode. A field in the floating-point control register (fpcr, see Alpha architecture reference manual) controls the rounding mode in effect. The C library initializes this register for rounding towards plus infinity. Thus, unless your program modifies the fpcr, d corresponds to round towards plus infinity. -mtrap-precision=trap-precision In the Alpha architecture, floating-point traps are imprecise. This means without software assistance it is impossible to recover from a floating trap and program execution normally needs to be terminated. GCC can generate code that can assist operating system trap handlers in determining the exact location that caused a floating-point trap. Depending on the requirements of an application, different levels of precisions can be selected: p Program precision. This option is the default and means a trap handler can only identify which program caused a floating-point exception. f Function precision. The trap handler can determine the function that caused a floating-point exception. i Instruction precision. The trap handler can determine the exact instruction that caused a floating-point exception. Other Alpha compilers provide the equivalent options called -scope_safe and -resumption_safe. -mieee-conformant This option marks the generated code as IEEE conformant. You must not use this option unless you also specify -mtrap-precision=i and either -mfp-trap-mode=su or -mfp-trap-mode=sui. Its only effect is to emit the line .eflag 48 in the function prologue of the generated assembly file. -mbuild-constants Normally GCC examines a 32- or 64-bit integer constant to see if it can construct it from smaller constants in two or three instructions. If it cannot, it outputs the constant as a literal and generates code to load it from the data segment at run time. Use this option to require GCC to construct all integer constants using code, even if it takes more instructions (the maximum is six). You typically use this option to build a shared library dynamic loader. Itself a shared library, it must relocate itself in memory before it can find the variables and constants in its own data segment. -mbwx -mno-bwx -mcix -mno-cix -mfix -mno-fix -mmax -mno-max Indicate whether GCC should generate code to use the optional BWX, CIX, FIX and MAX instruction sets. The default is to use the instruction sets supported by the CPU type specified via -mcpu= option or that of the CPU on which GCC was built if none is specified. -mfloat-vax -mfloat-ieee Generate code that uses (does not use) VAX F and G floating-point arithmetic instead of IEEE single and double precision. -mexplicit-relocs -mno-explicit-relocs Older Alpha assemblers provided no way to generate symbol relocations except via assembler macros. Use of these macros does not allow optimal instruction scheduling. GNU binutils as of version 2.12 supports a new syntax that allows the compiler to explicitly mark which relocations should apply to which instructions. This option is mostly useful for debugging, as GCC detects the capabilities of the assembler when it is built and sets the default accordingly. -msmall-data -mlarge-data When -mexplicit-relocs is in effect, static data is accessed via gp-relative relocations. When -msmall-data is used, objects 8 bytes long or smaller are placed in a small data area (the ".sdata" and ".sbss" sections) and are accessed via 16-bit relocations off of the $gp register. This limits the size of the small data area to 64KB, but allows the variables to be directly accessed via a single instruction. The default is -mlarge-data. With this option the data area is limited to just below 2GB. Programs that require more than 2GB of data must use "malloc" or "mmap" to allocate the data in the heap instead of in the program's data segment. When generating code for shared libraries, -fpic implies -msmall-data and -fPIC implies -mlarge-data. -msmall-text -mlarge-text When -msmall-text is used, the compiler assumes that the code of the entire program (or shared library) fits in 4MB, and is thus reachable with a branch instruction. When -msmall-data is used, the compiler can assume that all local symbols share the same $gp value, and thus reduce the number of instructions required for a function call from 4 to 1. The default is -mlarge-text. -mcpu=cpu_type Set the instruction set and instruction scheduling parameters for machine type cpu_type. You can specify either the EV style name or the corresponding chip number. GCC supports scheduling parameters for the EV4, EV5 and EV6 family of processors and chooses the default values for the instruction set from the processor you specify. If you do not specify a processor type, GCC defaults to the processor on which the compiler was built. Supported values for cpu_type are ev4 ev45 21064 Schedules as an EV4 and has no instruction set extensions. ev5 21164 Schedules as an EV5 and has no instruction set extensions. ev56 21164a Schedules as an EV5 and supports the BWX extension. pca56 21164pc 21164PC Schedules as an EV5 and supports the BWX and MAX extensions. ev6 21264 Schedules as an EV6 and supports the BWX, FIX, and MAX extensions. ev67 21264a Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions. Native toolchains also support the value native, which selects the best architecture option for the host processor. -mcpu=native has no effect if GCC does not recognize the processor. -mtune=cpu_type Set only the instruction scheduling parameters for machine type cpu_type. The instruction set is not changed. Native toolchains also support the value native, which selects the best architecture option for the host processor. -mtune=native has no effect if GCC does not recognize the processor. -mmemory-latency=time Sets the latency the scheduler should assume for typical memory references as seen by the application. This number is highly dependent on the memory access patterns used by the application and the size of the external cache on the machine. Valid options for time are number A decimal number representing clock cycles. L1 L2 L3 main The compiler contains estimates of the number of clock cycles for "typical" EV4 & EV5 hardware for the Level 1, 2 & 3 caches (also called Dcache, Scache, and Bcache), as well as to main memory. Note that L3 is only valid for EV5. eBPF Options -mframe-limit=bytes This specifies the hard limit for frame sizes, in bytes. Currently, the value that can be specified should be less than or equal to 32767. Defaults to whatever limit is imposed by the version of the Linux kernel targeted. -mkernel=version This specifies the minimum version of the kernel that will run the compiled program. GCC uses this version to determine which instructions to use, what kernel helpers to allow, etc. Currently, version can be one of 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10, 4.11, 4.12, 4.13, 4.14, 4.15, 4.16, 4.17, 4.18, 4.19, 4.20, 5.0, 5.1, 5.2, latest and native. -mbig-endian Generate code for a big-endian target. -mlittle-endian Generate code for a little-endian target. This is the default. -mjmpext Enable generation of extra conditional-branch instructions. Enabled for CPU v2 and above. -mjmp32 Enable 32-bit jump instructions. Enabled for CPU v3 and above. -malu32 Enable 32-bit ALU instructions. Enabled for CPU v3 and above. -mcpu=version This specifies which version of the eBPF ISA to target. Newer versions may not be supported by all kernels. The default is v3. Supported values for version are: v1 The first stable eBPF ISA with no special features or extensions. v2 Supports the jump extensions, as in -mjmpext. v3 All features of v2, plus: -<32-bit jump operations, as in -mjmp32> -<32-bit ALU operations, as in -malu32> -mco-re Enable BPF Compile Once - Run Everywhere (CO-RE) support. Requires and is implied by -gbtf. -mno-co-re Disable BPF Compile Once - Run Everywhere (CO-RE) support. BPF CO- RE support is enabled by default when generating BTF debug information for the BPF target. -mxbpf Generate code for an expanded version of BPF, which relaxes some of the restrictions imposed by the BPF architecture: -<Save and restore callee-saved registers at function entry and> exit, respectively. FR30 Options These options are defined specifically for the FR30 port. -msmall-model Use the small address space model. This can produce smaller code, but it does assume that all symbolic values and addresses fit into a 20-bit range. -mno-lsim Assume that runtime support has been provided and so there is no need to include the simulator library (libsim.a) on the linker command line. FT32 Options These options are defined specifically for the FT32 port. -msim Specifies that the program will be run on the simulator. This causes an alternate runtime startup and library to be linked. You must not use this option when generating programs that will run on real hardware; you must provide your own runtime library for whatever I/O functions are needed. -mlra Enable Local Register Allocation. This is still experimental for FT32, so by default the compiler uses standard reload. -mnodiv Do not use div and mod instructions. -mft32b Enable use of the extended instructions of the FT32B processor. -mcompress Compress all code using the Ft32B code compression scheme. -mnopm Do not generate code that reads program memory. FRV Options -mgpr-32 Only use the first 32 general-purpose registers. -mgpr-64 Use all 64 general-purpose registers. -mfpr-32 Use only the first 32 floating-point registers. -mfpr-64 Use all 64 floating-point registers. -mhard-float Use hardware instructions for floating-point operations. -msoft-float Use library routines for floating-point operations. -malloc-cc Dynamically allocate condition code registers. -mfixed-cc Do not try to dynamically allocate condition code registers, only use "icc0" and "fcc0". -mdword Change ABI to use double word insns. -mno-dword Do not use double word instructions. -mdouble Use floating-point double instructions. -mno-double Do not use floating-point double instructions. -mmedia Use media instructions. -mno-media Do not use media instructions. -mmuladd Use multiply and add/subtract instructions. -mno-muladd Do not use multiply and add/subtract instructions. -mfdpic Select the FDPIC ABI, which uses function descriptors to represent pointers to functions. Without any PIC/PIE-related options, it implies -fPIE. With -fpic or -fpie, it assumes GOT entries and small data are within a 12-bit range from the GOT base address; with -fPIC or -fPIE, GOT offsets are computed with 32 bits. With a bfin-elf target, this option implies -msim. -minline-plt Enable inlining of PLT entries in function calls to functions that are not known to bind locally. It has no effect without -mfdpic. It's enabled by default if optimizing for speed and compiling for shared libraries (i.e., -fPIC or -fpic), or when an optimization option such as -O3 or above is present in the command line. -mTLS Assume a large TLS segment when generating thread-local code. -mtls Do not assume a large TLS segment when generating thread-local code. -mgprel-ro Enable the use of "GPREL" relocations in the FDPIC ABI for data that is known to be in read-only sections. It's enabled by default, except for -fpic or -fpie: even though it may help make the global offset table smaller, it trades 1 instruction for 4. With -fPIC or -fPIE, it trades 3 instructions for 4, one of which may be shared by multiple symbols, and it avoids the need for a GOT entry for the referenced symbol, so it's more likely to be a win. If it is not, -mno-gprel-ro can be used to disable it. -multilib-library-pic Link with the (library, not FD) pic libraries. It's implied by -mlibrary-pic, as well as by -fPIC and -fpic without -mfdpic. You should never have to use it explicitly. -mlinked-fp Follow the EABI requirement of always creating a frame pointer whenever a stack frame is allocated. This option is enabled by default and can be disabled with -mno-linked-fp. -mlong-calls Use indirect addressing to call functions outside the current compilation unit. This allows the functions to be placed anywhere within the 32-bit address space. -malign-labels Try to align labels to an 8-byte boundary by inserting NOPs into the previous packet. This option only has an effect when VLIW packing is enabled. It doesn't create new packets; it merely adds NOPs to existing ones. -mlibrary-pic Generate position-independent EABI code. -macc-4 Use only the first four media accumulator registers. -macc-8 Use all eight media accumulator registers. -mpack Pack VLIW instructions. -mno-pack Do not pack VLIW instructions. -mno-eflags Do not mark ABI switches in e_flags. -mcond-move Enable the use of conditional-move instructions (default). This switch is mainly for debugging the compiler and will likely be removed in a future version. -mno-cond-move Disable the use of conditional-move instructions. This switch is mainly for debugging the compiler and will likely be removed in a future version. -mscc Enable the use of conditional set instructions (default). This switch is mainly for debugging the compiler and will likely be removed in a future version. -mno-scc Disable the use of conditional set instructions. This switch is mainly for debugging the compiler and will likely be removed in a future version. -mcond-exec Enable the use of conditional execution (default). This switch is mainly for debugging the compiler and will likely be removed in a future version. -mno-cond-exec Disable the use of conditional execution. This switch is mainly for debugging the compiler and will likely be removed in a future version. -mvliw-branch Run a pass to pack branches into VLIW instructions (default). This switch is mainly for debugging the compiler and will likely be removed in a future version. -mno-vliw-branch Do not run a pass to pack branches into VLIW instructions. This switch is mainly for debugging the compiler and will likely be removed in a future version. -mmulti-cond-exec Enable optimization of "&&" and "||" in conditional execution (default). This switch is mainly for debugging the compiler and will likely be removed in a future version. -mno-multi-cond-exec Disable optimization of "&&" and "||" in conditional execution. This switch is mainly for debugging the compiler and will likely be removed in a future version. -mnested-cond-exec Enable nested conditional execution optimizations (default). This switch is mainly for debugging the compiler and will likely be removed in a future version. -mno-nested-cond-exec Disable nested conditional execution optimizations. This switch is mainly for debugging the compiler and will likely be removed in a future version. -moptimize-membar This switch removes redundant "membar" instructions from the compiler-generated code. It is enabled by default. -mno-optimize-membar This switch disables the automatic removal of redundant "membar" instructions from the generated code. -mtomcat-stats Cause gas to print out tomcat statistics. -mcpu=cpu Select the processor type for which to generate code. Possible values are frv, fr550, tomcat, fr500, fr450, fr405, fr400, fr300 and simple. GNU/Linux Options These -m options are defined for GNU/Linux targets: -mglibc Use the GNU C library. This is the default except on *-*-linux-*uclibc*, *-*-linux-*musl* and *-*-linux-*android* targets. -muclibc Use uClibc C library. This is the default on *-*-linux-*uclibc* targets. -mmusl Use the musl C library. This is the default on *-*-linux-*musl* targets. -mbionic Use Bionic C library. This is the default on *-*-linux-*android* targets. -mandroid Compile code compatible with Android platform. This is the default on *-*-linux-*android* targets. When compiling, this option enables -mbionic, -fPIC, -fno-exceptions and -fno-rtti by default. When linking, this option makes the GCC driver pass Android-specific options to the linker. Finally, this option causes the preprocessor macro "__ANDROID__" to be defined. -tno-android-cc Disable compilation effects of -mandroid, i.e., do not enable -mbionic, -fPIC, -fno-exceptions and -fno-rtti by default. -tno-android-ld Disable linking effects of -mandroid, i.e., pass standard Linux linking options to the linker. H8/300 Options These -m options are defined for the H8/300 implementations: -mrelax Shorten some address references at link time, when possible; uses the linker option -relax. -mh Generate code for the H8/300H. -ms Generate code for the H8S. -mn Generate code for the H8S and H8/300H in the normal mode. This switch must be used either with -mh or -ms. -ms2600 Generate code for the H8S/2600. This switch must be used with -ms. -mexr Extended registers are stored on stack before execution of function with monitor attribute. Default option is -mexr. This option is valid only for H8S targets. -mno-exr Extended registers are not stored on stack before execution of function with monitor attribute. Default option is -mno-exr. This option is valid only for H8S targets. -mint32 Make "int" data 32 bits by default. -malign-300 On the H8/300H and H8S, use the same alignment rules as for the H8/300. The default for the H8/300H and H8S is to align longs and floats on 4-byte boundaries. -malign-300 causes them to be aligned on 2-byte boundaries. This option has no effect on the H8/300. HPPA Options These -m options are defined for the HPPA family of computers: -march=architecture-type Generate code for the specified architecture. The choices for architecture-type are 1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for PA 2.0 processors. Refer to /usr/lib/sched.models on an HP-UX system to determine the proper architecture option for your machine. Code compiled for lower numbered architectures runs on higher numbered architectures, but not the other way around. -mpa-risc-1-0 -mpa-risc-1-1 -mpa-risc-2-0 Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively. -matomic-libcalls Generate libcalls for atomic loads and stores when sync libcalls are disabled. This option is enabled by default. It only affects the generation of atomic libcalls by the HPPA backend. Both the sync and libatomic libcall implementations use locking. As a result, processor stores are not atomic with respect to other atomic operations. Processor loads up to DImode are atomic with respect to other atomic operations provided they are implemented as a single access. The PA-RISC architecture does not support any atomic operations in hardware except for the "ldcw" instruction. Thus, all atomic support is implemented using sync and atomic libcalls. Sync libcall support is in libgcc.a. Atomic libcall support is in libatomic. This option generates "__atomic_exchange" calls for atomic stores. It also provides special handling for atomic DImode accesses on 32-bit targets. -mbig-switch Does nothing. Preserved for backward compatibility. -mcaller-copies The caller copies function arguments passed by hidden reference. This option should be used with care as it is not compatible with the default 32-bit runtime. However, only aggregates larger than eight bytes are passed by hidden reference and the option provides better compatibility with OpenMP. -mcoherent-ldcw Use ldcw/ldcd coherent cache-control hint. -mdisable-fpregs Disable floating-point registers. Equivalent to "-msoft-float". -mdisable-indexing Prevent the compiler from using indexing address modes. This avoids some rather obscure problems when compiling MIG generated code under MACH. -mfast-indirect-calls Generate code that assumes calls never cross space boundaries. This allows GCC to emit code that performs faster indirect calls. This option does not work in the presence of shared libraries or nested functions. -mfixed-range=register-range Generate code treating the given register range as fixed registers. A fixed register is one that the register allocator cannot use. This is useful when compiling kernel code. A register range is specified as two registers separated by a dash. Multiple register ranges can be specified separated by a comma. -mgas Enable the use of assembler directives only GAS understands. -mgnu-ld Use options specific to GNU ld. This passes -shared to ld when building a shared library. It is the default when GCC is configured, explicitly or implicitly, with the GNU linker. This option does not affect which ld is called; it only changes what parameters are passed to that ld. The ld that is called is determined by the --with-ld configure option, GCC's program search path, and finally by the user's PATH. The linker used by GCC can be printed using which `gcc -print-prog-name=ld`. This option is only available on the 64-bit HP-UX GCC, i.e. configured with hppa*64*-*-hpux*. -mhp-ld Use options specific to HP ld. This passes -b to ld when building a shared library and passes +Accept TypeMismatch to ld on all links. It is the default when GCC is configured, explicitly or implicitly, with the HP linker. This option does not affect which ld is called; it only changes what parameters are passed to that ld. The ld that is called is determined by the --with-ld configure option, GCC's program search path, and finally by the user's PATH. The linker used by GCC can be printed using which `gcc -print-prog-name=ld`. This option is only available on the 64-bit HP-UX GCC, i.e. configured with hppa*64*-*-hpux*. -mlinker-opt Enable the optimization pass in the HP-UX linker. Note this makes symbolic debugging impossible. It also triggers a bug in the HP-UX 8 and HP-UX 9 linkers in which they give bogus error messages when linking some programs. -mlong-calls Generate code that uses long call sequences. This ensures that a call is always able to reach linker generated stubs. The default is to generate long calls only when the distance from the call site to the beginning of the function or translation unit, as the case may be, exceeds a predefined limit set by the branch type being used. The limits for normal calls are 7,600,000 and 240,000 bytes, respectively for the PA 2.0 and PA 1.X architectures. Sibcalls are always limited at 240,000 bytes. Distances are measured from the beginning of functions when using the -ffunction-sections option, or when using the -mgas and -mno-portable-runtime options together under HP-UX with the SOM linker. It is normally not desirable to use this option as it degrades performance. However, it may be useful in large applications, particularly when partial linking is used to build the application. The types of long calls used depends on the capabilities of the assembler and linker, and the type of code being generated. The impact on systems that support long absolute calls, and long pic symbol-difference or pc-relative calls should be relatively small. However, an indirect call is used on 32-bit ELF systems in pic code and it is quite long. -mlong-load-store Generate 3-instruction load and store sequences as sometimes required by the HP-UX 10 linker. This is equivalent to the +k option to the HP compilers. -mjump-in-delay This option is ignored and provided for compatibility purposes only. -mno-space-regs Generate code that assumes the target has no space registers. This allows GCC to generate faster indirect calls and use unscaled index address modes. Such code is suitable for level 0 PA systems and kernels. -mordered Assume memory references are ordered and barriers are not needed. -mportable-runtime Use the portable calling conventions proposed by HP for ELF systems. -mschedule=cpu-type Schedule code according to the constraints for the machine type cpu-type. The choices for cpu-type are 700 7100, 7100LC, 7200, 7300 and 8000. Refer to /usr/lib/sched.models on an HP-UX system to determine the proper scheduling option for your machine. The default scheduling is 8000. -msio Generate the predefine, "_SIO", for server IO. The default is -mwsio. This generates the predefines, "__hp9000s700", "__hp9000s700__" and "_WSIO", for workstation IO. These options are available under HP-UX and HI-UX. -msoft-float Generate output containing library calls for floating point. Warning: the requisite libraries are not available for all HPPA targets. Normally the facilities of the machine's usual C compiler are used, but this cannot be done directly in cross-compilation. You must make your own arrangements to provide suitable library functions for cross-compilation. -msoft-float changes the calling convention in the output file; therefore, it is only useful if you compile all of a program with this option. In particular, you need to compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this to work. -msoft-mult Use software integer multiplication. This disables the use of the "xmpyu" instruction. -munix=unix-std Generate compiler predefines and select a startfile for the specified UNIX standard. The choices for unix-std are 93, 95 and 98. 93 is supported on all HP-UX versions. 95 is available on HP- UX 10.10 and later. 98 is available on HP-UX 11.11 and later. The default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though to 11.00, and 98 for HP-UX 11.11 and later. -munix=93 provides the same predefines as GCC 3.3 and 3.4. -munix=95 provides additional predefines for "XOPEN_UNIX" and "_XOPEN_SOURCE_EXTENDED", and the startfile unix95.o. -munix=98 provides additional predefines for "_XOPEN_UNIX", "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o. It is important to note that this option changes the interfaces for various library routines. It also affects the operational behavior of the C library. Thus, extreme care is needed in using this option. Library code that is intended to operate with more than one UNIX standard must test, set and restore the variable "__xpg4_extended_mask" as appropriate. Most GNU software doesn't provide this capability. -nolibdld Suppress the generation of link options to search libdld.sl when the -static option is specified on HP-UX 10 and later. -static The HP-UX implementation of setlocale in libc has a dependency on libdld.sl. There isn't an archive version of libdld.sl. Thus, when the -static option is specified, special link options are needed to resolve this dependency. On HP-UX 10 and later, the GCC driver adds the necessary options to link with libdld.sl when the -static option is specified. This causes the resulting binary to be dynamic. On the 64-bit port, the linkers generate dynamic binaries by default in any case. The -nolibdld option can be used to prevent the GCC driver from adding these link options. -threads Add support for multithreading with the dce thread library under HP-UX. This option sets flags for both the preprocessor and linker. IA-64 Options These are the -m options defined for the Intel IA-64 architecture. -mbig-endian Generate code for a big-endian target. This is the default for HP- UX. -mlittle-endian Generate code for a little-endian target. This is the default for AIX5 and GNU/Linux. -mgnu-as -mno-gnu-as Generate (or don't) code for the GNU assembler. This is the default. -mgnu-ld -mno-gnu-ld Generate (or don't) code for the GNU linker. This is the default. -mno-pic Generate code that does not use a global pointer register. The result is not position independent code, and violates the IA-64 ABI. -mvolatile-asm-stop -mno-volatile-asm-stop Generate (or don't) a stop bit immediately before and after volatile asm statements. -mregister-names -mno-register-names Generate (or don't) in, loc, and out register names for the stacked registers. This may make assembler output more readable. -mno-sdata -msdata Disable (or enable) optimizations that use the small data section. This may be useful for working around optimizer bugs. -mconstant-gp Generate code that uses a single constant global pointer value. This is useful when compiling kernel code. -mauto-pic Generate code that is self-relocatable. This implies -mconstant-gp. This is useful when compiling firmware code. -minline-float-divide-min-latency Generate code for inline divides of floating-point values using the minimum latency algorithm. -minline-float-divide-max-throughput Generate code for inline divides of floating-point values using the maximum throughput algorithm. -mno-inline-float-divide Do not generate inline code for divides of floating-point values. -minline-int-divide-min-latency Generate code for inline divides of integer values using the minimum latency algorithm. -minline-int-divide-max-throughput Generate code for inline divides of integer values using the maximum throughput algorithm. -mno-inline-int-divide Do not generate inline code for divides of integer values. -minline-sqrt-min-latency Generate code for inline square roots using the minimum latency algorithm. -minline-sqrt-max-throughput Generate code for inline square roots using the maximum throughput algorithm. -mno-inline-sqrt Do not generate inline code for "sqrt". -mfused-madd -mno-fused-madd Do (don't) generate code that uses the fused multiply/add or multiply/subtract instructions. The default is to use these instructions. -mno-dwarf2-asm -mdwarf2-asm Don't (or do) generate assembler code for the DWARF line number debugging info. This may be useful when not using the GNU assembler. -mearly-stop-bits -mno-early-stop-bits Allow stop bits to be placed earlier than immediately preceding the instruction that triggered the stop bit. This can improve instruction scheduling, but does not always do so. -mfixed-range=register-range Generate code treating the given register range as fixed registers. A fixed register is one that the register allocator cannot use. This is useful when compiling kernel code. A register range is specified as two registers separated by a dash. Multiple register ranges can be specified separated by a comma. -mtls-size=tls-size Specify bit size of immediate TLS offsets. Valid values are 14, 22, and 64. -mtune=cpu-type Tune the instruction scheduling for a particular CPU, Valid values are itanium, itanium1, merced, itanium2, and mckinley. -milp32 -mlp64 Generate code for a 32-bit or 64-bit environment. The 32-bit environment sets int, long and pointer to 32 bits. The 64-bit environment sets int to 32 bits and long and pointer to 64 bits. These are HP-UX specific flags. -mno-sched-br-data-spec -msched-br-data-spec (Dis/En)able data speculative scheduling before reload. This results in generation of "ld.a" instructions and the corresponding check instructions ("ld.c" / "chk.a"). The default setting is disabled. -msched-ar-data-spec -mno-sched-ar-data-spec (En/Dis)able data speculative scheduling after reload. This results in generation of "ld.a" instructions and the corresponding check instructions ("ld.c" / "chk.a"). The default setting is enabled. -mno-sched-control-spec -msched-control-spec (Dis/En)able control speculative scheduling. This feature is available only during region scheduling (i.e. before reload). This results in generation of the "ld.s" instructions and the corresponding check instructions "chk.s". The default setting is disabled. -msched-br-in-data-spec -mno-sched-br-in-data-spec (En/Dis)able speculative scheduling of the instructions that are dependent on the data speculative loads before reload. This is effective only with -msched-br-data-spec enabled. The default setting is enabled. -msched-ar-in-data-spec -mno-sched-ar-in-data-spec (En/Dis)able speculative scheduling of the instructions that are dependent on the data speculative loads after reload. This is effective only with -msched-ar-data-spec enabled. The default setting is enabled. -msched-in-control-spec -mno-sched-in-control-spec (En/Dis)able speculative scheduling of the instructions that are dependent on the control speculative loads. This is effective only with -msched-control-spec enabled. The default setting is enabled. -mno-sched-prefer-non-data-spec-insns -msched-prefer-non-data-spec-insns If enabled, data-speculative instructions are chosen for schedule only if there are no other choices at the moment. This makes the use of the data speculation much more conservative. The default setting is disabled. -mno-sched-prefer-non-control-spec-insns -msched-prefer-non-control-spec-insns If enabled, control-speculative instructions are chosen for schedule only if there are no other choices at the moment. This makes the use of the control speculation much more conservative. The default setting is disabled. -mno-sched-count-spec-in-critical-path -msched-count-spec-in-critical-path If enabled, speculative dependencies are considered during computation of the instructions priorities. This makes the use of the speculation a bit more conservative. The default setting is disabled. -msched-spec-ldc Use a simple data speculation check. This option is on by default. -msched-control-spec-ldc Use a simple check for control speculation. This option is on by default. -msched-stop-bits-after-every-cycle Place a stop bit after every cycle when scheduling. This option is on by default. -msched-fp-mem-deps-zero-cost Assume that floating-point stores and loads are not likely to cause a conflict when placed into the same instruction group. This option is disabled by default. -msel-sched-dont-check-control-spec Generate checks for control speculation in selective scheduling. This flag is disabled by default. -msched-max-memory-insns=max-insns Limit on the number of memory insns per instruction group, giving lower priority to subsequent memory insns attempting to schedule in the same instruction group. Frequently useful to prevent cache bank conflicts. The default value is 1. -msched-max-memory-insns-hard-limit Makes the limit specified by msched-max-memory-insns a hard limit, disallowing more than that number in an instruction group. Otherwise, the limit is "soft", meaning that non-memory operations are preferred when the limit is reached, but memory operations may still be scheduled. LM32 Options These -m options are defined for the LatticeMico32 architecture: -mbarrel-shift-enabled Enable barrel-shift instructions. -mdivide-enabled Enable divide and modulus instructions. -mmultiply-enabled Enable multiply instructions. -msign-extend-enabled Enable sign extend instructions. -muser-enabled Enable user-defined instructions. LoongArch Options These command-line options are defined for LoongArch targets: -march=cpu-type Generate instructions for the machine type cpu-type. In contrast to -mtune=cpu-type, which merely tunes the generated code for the specified cpu-type, -march=cpu-type allows GCC to generate code that may not run at all on processors other than the one indicated. Specifying -march=cpu-type implies -mtune=cpu-type, except where noted otherwise. The choices for cpu-type are: native This selects the CPU to generate code for at compilation time by determining the processor type of the compiling machine. Using -march=native enables all instruction subsets supported by the local machine (hence the result might not run on different machines). Using -mtune=native produces code optimized for the local machine under the constraints of the selected instruction set. loongarch64 A generic CPU with 64-bit extensions. la464 LoongArch LA464 CPU with LBT, LSX, LASX, LVZ. -mtune=cpu-type Optimize the output for the given processor, specified by microarchitecture name. -mabi=base-abi-type Generate code for the specified calling convention. base-abi-type can be one of: lp64d Uses 64-bit general purpose registers and 32/64-bit floating- point registers for parameter passing. Data model is LP64, where int is 32 bits, while long int and pointers are 64 bits. lp64f Uses 64-bit general purpose registers and 32-bit floating-point registers for parameter passing. Data model is LP64, where int is 32 bits, while long int and pointers are 64 bits. lp64s Uses 64-bit general purpose registers and no floating-point registers for parameter passing. Data model is LP64, where int is 32 bits, while long int and pointers are 64 bits. -mfpu=fpu-type Generate code for the specified FPU type, which can be one of: 64 Allow the use of hardware floating-point instructions for 32-bit and 64-bit operations. 32 Allow the use of hardware floating-point instructions for 32-bit operations. none 0 Prevent the use of hardware floating-point instructions. -msoft-float Force -mfpu=none and prevents the use of floating-point registers for parameter passing. This option may change the target ABI. -msingle-float Force -mfpu=32 and allow the use of 32-bit floating-point registers for parameter passing. This option may change the target ABI. -mdouble-float Force -mfpu=64 and allow the use of 32/64-bit floating-point registers for parameter passing. This option may change the target ABI. -mbranch-cost=n Set the cost of branches to roughly n instructions. -mcheck-zero-division -mno-check-zero-divison Trap (do not trap) on integer division by zero. The default is -mcheck-zero-division for -O0 or -Og, and -mno-check-zero-division for other optimization levels. -mcond-move-int -mno-cond-move-int Conditional moves for integral data in general-purpose registers are enabled (disabled). The default is -mcond-move-int. -mcond-move-float -mno-cond-move-float Conditional moves for floating-point registers are enabled (disabled). The default is -mcond-move-float. -mmemcpy -mno-memcpy Force (do not force) the use of "memcpy" for non-trivial block moves. The default is -mno-memcpy, which allows GCC to inline most constant-sized copies. Setting optimization level to -Os also forces the use of "memcpy", but -mno-memcpy may override this behavior if explicitly specified, regardless of the order these options on the command line. -mstrict-align -mno-strict-align Avoid or allow generating memory accesses that may not be aligned on a natural object boundary as described in the architecture specification. The default is -mno-strict-align. -msmall-data-limit=number Put global and static data smaller than number bytes into a special section (on some targets). The default value is 0. -mmax-inline-memcpy-size=n Inline all block moves (such as calls to "memcpy" or structure copies) less than or equal to n bytes. The default value of n is 1024. -mcmodel=code-model Set the code model to one of: tiny-static (Not implemented yet) tiny (Not implemented yet) normal The text segment must be within 128MB addressing space. The data segment must be within 2GB addressing space. medium The text segment and data segment must be within 2GB addressing space. large (Not implemented yet) extreme This mode does not limit the size of the code segment and data segment. The -mcmodel=extreme option is incompatible with -fplt and -mno-explicit-relocs. The default code model is "normal". -mexplicit-relocs -mno-explicit-relocs Use or do not use assembler relocation operators when dealing with symbolic addresses. The alternative is to use assembler macros instead, which may limit optimization. The default value for the option is determined during GCC build-time by detecting corresponding assembler support: "-mexplicit-relocs" if said support is present, "-mno-explicit-relocs" otherwise. This option is mostly useful for debugging, or interoperation with assemblers different from the build-time one. -mdirect-extern-access -mno-direct-extern-access Do not use or use GOT to access external symbols. The default is -mno-direct-extern-access: GOT is used for external symbols with default visibility, but not used for other external symbols. With -mdirect-extern-access, GOT is not used and all external symbols are PC-relatively addressed. It is only suitable for environments where no dynamic link is performed, like firmwares, OS kernels, executables linked with -static or -static-pie. -mdirect-extern-access is not compatible with -fPIC or -fpic. M32C Options -mcpu=name Select the CPU for which code is generated. name may be one of r8c for the R8C/Tiny series, m16c for the M16C (up to /60) series, m32cm for the M16C/80 series, or m32c for the M32C/80 series. -msim Specifies that the program will be run on the simulator. This causes an alternate runtime library to be linked in which supports, for example, file I/O. You must not use this option when generating programs that will run on real hardware; you must provide your own runtime library for whatever I/O functions are needed. -memregs=number Specifies the number of memory-based pseudo-registers GCC uses during code generation. These pseudo-registers are used like real registers, so there is a tradeoff between GCC's ability to fit the code into available registers, and the performance penalty of using memory instead of registers. Note that all modules in a program must be compiled with the same value for this option. Because of that, you must not use this option with GCC's default runtime libraries. M32R/D Options These -m options are defined for Renesas M32R/D architectures: -m32r2 Generate code for the M32R/2. -m32rx Generate code for the M32R/X. -m32r Generate code for the M32R. This is the default. -mmodel=small Assume all objects live in the lower 16MB of memory (so that their addresses can be loaded with the "ld24" instruction), and assume all subroutines are reachable with the "bl" instruction. This is the default. The addressability of a particular object can be set with the "model" attribute. -mmodel=medium Assume objects may be anywhere in the 32-bit address space (the compiler generates "seth/add3" instructions to load their addresses), and assume all subroutines are reachable with the "bl" instruction. -mmodel=large Assume objects may be anywhere in the 32-bit address space (the compiler generates "seth/add3" instructions to load their addresses), and assume subroutines may not be reachable with the "bl" instruction (the compiler generates the much slower "seth/add3/jl" instruction sequence). -msdata=none Disable use of the small data area. Variables are put into one of ".data", ".bss", or ".rodata" (unless the "section" attribute has been specified). This is the default. The small data area consists of sections ".sdata" and ".sbss". Objects may be explicitly put in the small data area with the "section" attribute using one of these sections. -msdata=sdata Put small global and static data in the small data area, but do not generate special code to reference them. -msdata=use Put small global and static data in the small data area, and generate special instructions to reference them. -G num Put global and static objects less than or equal to num bytes into the small data or BSS sections instead of the normal data or BSS sections. The default value of num is 8. The -msdata option must be set to one of sdata or use for this option to have any effect. All modules should be compiled with the same -G num value. Compiling with different values of num may or may not work; if it doesn't the linker gives an error message---incorrect code is not generated. -mdebug Makes the M32R-specific code in the compiler display some statistics that might help in debugging programs. -malign-loops Align all loops to a 32-byte boundary. -mno-align-loops Do not enforce a 32-byte alignment for loops. This is the default. -missue-rate=number Issue number instructions per cycle. number can only be 1 or 2. -mbranch-cost=number number can only be 1 or 2. If it is 1 then branches are preferred over conditional code, if it is 2, then the opposite applies. -mflush-trap=number Specifies the trap number to use to flush the cache. The default is 12. Valid numbers are between 0 and 15 inclusive. -mno-flush-trap Specifies that the cache cannot be flushed by using a trap. -mflush-func=name Specifies the name of the operating system function to call to flush the cache. The default is _flush_cache, but a function call is only used if a trap is not available. -mno-flush-func Indicates that there is no OS function for flushing the cache. M680x0 Options These are the -m options defined for M680x0 and ColdFire processors. The default settings depend on which architecture was selected when the compiler was configured; the defaults for the most common choices are given below. -march=arch Generate code for a specific M680x0 or ColdFire instruction set architecture. Permissible values of arch for M680x0 architectures are: 68000, 68010, 68020, 68030, 68040, 68060 and cpu32. ColdFire architectures are selected according to Freescale's ISA classification and the permissible values are: isaa, isaaplus, isab and isac. GCC defines a macro "__mcfarch__" whenever it is generating code for a ColdFire target. The arch in this macro is one of the -march arguments given above. When used together, -march and -mtune select code that runs on a family of similar processors but that is optimized for a particular microarchitecture. -mcpu=cpu Generate code for a specific M680x0 or ColdFire processor. The M680x0 cpus are: 68000, 68010, 68020, 68030, 68040, 68060, 68302, 68332 and cpu32. The ColdFire cpus are given by the table below, which also classifies the CPUs into families: Family : -mcpu arguments 51 : 51 51ac 51ag 51cn 51em 51je 51jf 51jg 51jm 51mm 51qe 51qm 5206 : 5202 5204 5206 5206e : 5206e 5208 : 5207 5208 5211a : 5210a 5211a 5213 : 5211 5212 5213 5216 : 5214 5216 52235 : 52230 52231 52232 52233 52234 52235 5225 : 5224 5225 52259 : 52252 52254 52255 52256 52258 52259 5235 : 5232 5233 5234 5235 523x 5249 : 5249 5250 : 5250 5271 : 5270 5271 5272 : 5272 5275 : 5274 5275 5282 : 5280 5281 5282 528x 53017 : 53011 53012 53013 53014 53015 53016 53017 5307 : 5307 5329 : 5327 5328 5329 532x 5373 : 5372 5373 537x 5407 : 5407 5475 : 5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483 5484 5485 -mcpu=cpu overrides -march=arch if arch is compatible with cpu. Other combinations of -mcpu and -march are rejected. GCC defines the macro "__mcf_cpu_cpu" when ColdFire target cpu is selected. It also defines "__mcf_family_family", where the value of family is given by the table above. -mtune=tune Tune the code for a particular microarchitecture within the constraints set by -march and -mcpu. The M680x0 microarchitectures are: 68000, 68010, 68020, 68030, 68040, 68060 and cpu32. The ColdFire microarchitectures are: cfv1, cfv2, cfv3, cfv4 and cfv4e. You can also use -mtune=68020-40 for code that needs to run relatively well on 68020, 68030 and 68040 targets. -mtune=68020-60 is similar but includes 68060 targets as well. These two options select the same tuning decisions as -m68020-40 and -m68020-60 respectively. GCC defines the macros "__mcarch" and "__mcarch__" when tuning for 680x0 architecture arch. It also defines "mcarch" unless either -ansi or a non-GNU -std option is used. If GCC is tuning for a range of architectures, as selected by -mtune=68020-40 or -mtune=68020-60, it defines the macros for every architecture in the range. GCC also defines the macro "__muarch__" when tuning for ColdFire microarchitecture uarch, where uarch is one of the arguments given above. -m68000 -mc68000 Generate output for a 68000. This is the default when the compiler is configured for 68000-based systems. It is equivalent to -march=68000. Use this option for microcontrollers with a 68000 or EC000 core, including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. -m68010 Generate output for a 68010. This is the default when the compiler is configured for 68010-based systems. It is equivalent to -march=68010. -m68020 -mc68020 Generate output for a 68020. This is the default when the compiler is configured for 68020-based systems. It is equivalent to -march=68020. -m68030 Generate output for a 68030. This is the default when the compiler is configured for 68030-based systems. It is equivalent to -march=68030. -m68040 Generate output for a 68040. This is the default when the compiler is configured for 68040-based systems. It is equivalent to -march=68040. This option inhibits the use of 68881/68882 instructions that have to be emulated by software on the 68040. Use this option if your 68040 does not have code to emulate those instructions. -m68060 Generate output for a 68060. This is the default when the compiler is configured for 68060-based systems. It is equivalent to -march=68060. This option inhibits the use of 68020 and 68881/68882 instructions that have to be emulated by software on the 68060. Use this option if your 68060 does not have code to emulate those instructions. -mcpu32 Generate output for a CPU32. This is the default when the compiler is configured for CPU32-based systems. It is equivalent to -march=cpu32. Use this option for microcontrollers with a CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334, 68336, 68340, 68341, 68349 and 68360. -m5200 Generate output for a 520X ColdFire CPU. This is the default when the compiler is configured for 520X-based systems. It is equivalent to -mcpu=5206, and is now deprecated in favor of that option. Use this option for microcontroller with a 5200 core, including the MCF5202, MCF5203, MCF5204 and MCF5206. -m5206e Generate output for a 5206e ColdFire CPU. The option is now deprecated in favor of the equivalent -mcpu=5206e. -m528x Generate output for a member of the ColdFire 528X family. The option is now deprecated in favor of the equivalent -mcpu=528x. -m5307 Generate output for a ColdFire 5307 CPU. The option is now deprecated in favor of the equivalent -mcpu=5307. -m5407 Generate output for a ColdFire 5407 CPU. The option is now deprecated in favor of the equivalent -mcpu=5407. -mcfv4e Generate output for a ColdFire V4e family CPU (e.g. 547x/548x). This includes use of hardware floating-point instructions. The option is equivalent to -mcpu=547x, and is now deprecated in favor of that option. -m68020-40 Generate output for a 68040, without using any of the new instructions. This results in code that can run relatively efficiently on either a 68020/68881 or a 68030 or a 68040. The generated code does use the 68881 instructions that are emulated on the 68040. The option is equivalent to -march=68020 -mtune=68020-40. -m68020-60 Generate output for a 68060, without using any of the new instructions. This results in code that can run relatively efficiently on either a 68020/68881 or a 68030 or a 68040. The generated code does use the 68881 instructions that are emulated on the 68060. The option is equivalent to -march=68020 -mtune=68020-60. -mhard-float -m68881 Generate floating-point instructions. This is the default for 68020 and above, and for ColdFire devices that have an FPU. It defines the macro "__HAVE_68881__" on M680x0 targets and "__mcffpu__" on ColdFire targets. -msoft-float Do not generate floating-point instructions; use library calls instead. This is the default for 68000, 68010, and 68832 targets. It is also the default for ColdFire devices that have no FPU. -mdiv -mno-div Generate (do not generate) ColdFire hardware divide and remainder instructions. If -march is used without -mcpu, the default is "on" for ColdFire architectures and "off" for M680x0 architectures. Otherwise, the default is taken from the target CPU (either the default CPU, or the one specified by -mcpu). For example, the default is "off" for -mcpu=5206 and "on" for -mcpu=5206e. GCC defines the macro "__mcfhwdiv__" when this option is enabled. -mshort Consider type "int" to be 16 bits wide, like "short int". Additionally, parameters passed on the stack are also aligned to a 16-bit boundary even on targets whose API mandates promotion to 32-bit. -mno-short Do not consider type "int" to be 16 bits wide. This is the default. -mnobitfield -mno-bitfield Do not use the bit-field instructions. The -m68000, -mcpu32 and -m5200 options imply -mnobitfield. -mbitfield Do use the bit-field instructions. The -m68020 option implies -mbitfield. This is the default if you use a configuration designed for a 68020. -mrtd Use a different function-calling convention, in which functions that take a fixed number of arguments return with the "rtd" instruction, which pops their arguments while returning. This saves one instruction in the caller since there is no need to pop the arguments there. This calling convention is incompatible with the one normally used on Unix, so you cannot use it if you need to call libraries compiled with the Unix compiler. Also, you must provide function prototypes for all functions that take variable numbers of arguments (including "printf"); otherwise incorrect code is generated for calls to those functions. In addition, seriously incorrect code results if you call a function with too many arguments. (Normally, extra arguments are harmlessly ignored.) The "rtd" instruction is supported by the 68010, 68020, 68030, 68040, 68060 and CPU32 processors, but not by the 68000 or 5200. The default is -mno-rtd. -malign-int -mno-align-int Control whether GCC aligns "int", "long", "long long", "float", "double", and "long double" variables on a 32-bit boundary (-malign-int) or a 16-bit boundary (-mno-align-int). Aligning variables on 32-bit boundaries produces code that runs somewhat faster on processors with 32-bit busses at the expense of more memory. Warning: if you use the -malign-int switch, GCC aligns structures containing the above types differently than most published application binary interface specifications for the m68k. Use the pc-relative addressing mode of the 68000 directly, instead of using a global offset table. At present, this option implies -fpic, allowing at most a 16-bit offset for pc-relative addressing. -fPIC is not presently supported with -mpcrel, though this could be supported for 68020 and higher processors. -mno-strict-align -mstrict-align Do not (do) assume that unaligned memory references are handled by the system. -msep-data Generate code that allows the data segment to be located in a different area of memory from the text segment. This allows for execute-in-place in an environment without virtual memory management. This option implies -fPIC. -mno-sep-data Generate code that assumes that the data segment follows the text segment. This is the default. -mid-shared-library Generate code that supports shared libraries via the library ID method. This allows for execute-in-place and shared libraries in an environment without virtual memory management. This option implies -fPIC. -mno-id-shared-library Generate code that doesn't assume ID-based shared libraries are being used. This is the default. -mshared-library-id=n Specifies the identification number of the ID-based shared library being compiled. Specifying a value of 0 generates more compact code; specifying other values forces the allocation of that number to the current library, but is no more space- or time-efficient than omitting this option. -mxgot -mno-xgot When generating position-independent code for ColdFire, generate code that works if the GOT has more than 8192 entries. This code is larger and slower than code generated without this option. On M680x0 processors, this option is not needed; -fPIC suffices. GCC normally uses a single instruction to load values from the GOT. While this is relatively efficient, it only works if the GOT is smaller than about 64k. Anything larger causes the linker to report an error such as: relocation truncated to fit: R_68K_GOT16O foobar If this happens, you should recompile your code with -mxgot. It should then work with very large GOTs. However, code generated with -mxgot is less efficient, since it takes 4 instructions to fetch the value of a global symbol. Note that some linkers, including newer versions of the GNU linker, can create multiple GOTs and sort GOT entries. If you have such a linker, you should only need to use -mxgot when compiling a single object file that accesses more than 8192 GOT entries. Very few do. These options have no effect unless GCC is generating position- independent code. -mlong-jump-table-offsets Use 32-bit offsets in "switch" tables. The default is to use 16-bit offsets. MCore Options These are the -m options defined for the Motorola M*Core processors. -mhardlit -mno-hardlit Inline constants into the code stream if it can be done in two instructions or less. -mdiv -mno-div Use the divide instruction. (Enabled by default). -mrelax-immediate -mno-relax-immediate Allow arbitrary-sized immediates in bit operations. -mwide-bitfields -mno-wide-bitfields Always treat bit-fields as "int"-sized. -m4byte-functions -mno-4byte-functions Force all functions to be aligned to a 4-byte boundary. -mcallgraph-data -mno-callgraph-data Emit callgraph information. -mslow-bytes -mno-slow-bytes Prefer word access when reading byte quantities. -mlittle-endian -mbig-endian Generate code for a little-endian target. -m210 -m340 Generate code for the 210 processor. -mno-lsim Assume that runtime support has been provided and so omit the simulator library (libsim.a) from the linker command line. -mstack-increment=size Set the maximum amount for a single stack increment operation. Large values can increase the speed of programs that contain functions that need a large amount of stack space, but they can also trigger a segmentation fault if the stack is extended too much. The default value is 0x1000. MicroBlaze Options -msoft-float Use software emulation for floating point (default). -mhard-float Use hardware floating-point instructions. -mmemcpy Do not optimize block moves, use "memcpy". -mno-clearbss This option is deprecated. Use -fno-zero-initialized-in-bss instead. -mcpu=cpu-type Use features of, and schedule code for, the given CPU. Supported values are in the format vX.YY.Z, where X is a major version, YY is the minor version, and Z is compatibility code. Example values are v3.00.a, v4.00.b, v5.00.a, v5.00.b, v6.00.a. -mxl-soft-mul Use software multiply emulation (default). -mxl-soft-div Use software emulation for divides (default). -mxl-barrel-shift Use the hardware barrel shifter. -mxl-pattern-compare Use pattern compare instructions. -msmall-divides Use table lookup optimization for small signed integer divisions. -mxl-stack-check This option is deprecated. Use -fstack-check instead. -mxl-gp-opt Use GP-relative ".sdata"/".sbss" sections. -mxl-multiply-high Use multiply high instructions for high part of 32x32 multiply. -mxl-float-convert Use hardware floating-point conversion instructions. -mxl-float-sqrt Use hardware floating-point square root instruction. -mbig-endian Generate code for a big-endian target. -mlittle-endian Generate code for a little-endian target. -mxl-reorder Use reorder instructions (swap and byte reversed load/store). -mxl-mode-app-model Select application model app-model. Valid models are executable normal executable (default), uses startup code crt0.o. xmdstub for use with Xilinx Microprocessor Debugger (XMD) based software intrusive debug agent called xmdstub. This uses startup file crt1.o and sets the start address of the program to 0x800. bootstrap for applications that are loaded using a bootloader. This model uses startup file crt2.o which does not contain a processor reset vector handler. This is suitable for transferring control on a processor reset to the bootloader rather than the application. novectors for applications that do not require any of the MicroBlaze vectors. This option may be useful for applications running within a monitoring application. This model uses crt3.o as a startup file. Option -xl-mode-app-model is a deprecated alias for -mxl-mode-app- model. -mpic-data-is-text-relative Assume that the displacement between the text and data segments is fixed at static link time. This allows data to be referenced by offset from start of text address instead of GOT since PC-relative addressing is not supported. MIPS Options -EB Generate big-endian code. -EL Generate little-endian code. This is the default for mips*el-*-* configurations. -march=arch Generate code that runs on arch, which can be the name of a generic MIPS ISA, or the name of a particular processor. The ISA names are: mips1, mips2, mips3, mips4, mips32, mips32r2, mips32r3, mips32r5, mips32r6, mips64, mips64r2, mips64r3, mips64r5 and mips64r6. The processor names are: 4kc, 4km, 4kp, 4ksc, 4kec, 4kem, 4kep, 4ksd, 5kc, 5kf, 20kc, 24kc, 24kf2_1, 24kf1_1, 24kec, 24kef2_1, 24kef1_1, 34kc, 34kf2_1, 34kf1_1, 34kn, 74kc, 74kf2_1, 74kf1_1, 74kf3_2, 1004kc, 1004kf2_1, 1004kf1_1, i6400, i6500, interaptiv, loongson2e, loongson2f, loongson3a, gs464, gs464e, gs264e, m4k, m14k, m14kc, m14ke, m14kec, m5100, m5101, octeon, octeon+, octeon2, octeon3, orion, p5600, p6600, r2000, r3000, r3900, r4000, r4400, r4600, r4650, r4700, r5900, r6000, r8000, rm7000, rm9000, r10000, r12000, r14000, r16000, sb1, sr71000, vr4100, vr4111, vr4120, vr4130, vr4300, vr5000, vr5400, vr5500, xlr and xlp. The special value from-abi selects the most compatible architecture for the selected ABI (that is, mips1 for 32-bit ABIs and mips3 for 64-bit ABIs). The native Linux/GNU toolchain also supports the value native, which selects the best architecture option for the host processor. -march=native has no effect if GCC does not recognize the processor. In processor names, a final 000 can be abbreviated as k (for example, -march=r2k). Prefixes are optional, and vr may be written r. Names of the form nf2_1 refer to processors with FPUs clocked at half the rate of the core, names of the form nf1_1 refer to processors with FPUs clocked at the same rate as the core, and names of the form nf3_2 refer to processors with FPUs clocked a ratio of 3:2 with respect to the core. For compatibility reasons, nf is accepted as a synonym for nf2_1 while nx and bfx are accepted as synonyms for nf1_1. GCC defines two macros based on the value of this option. The first is "_MIPS_ARCH", which gives the name of target architecture, as a string. The second has the form "_MIPS_ARCH_foo", where foo is the capitalized value of "_MIPS_ARCH". For example, -march=r2000 sets "_MIPS_ARCH" to "r2000" and defines the macro "_MIPS_ARCH_R2000". Note that the "_MIPS_ARCH" macro uses the processor names given above. In other words, it has the full prefix and does not abbreviate 000 as k. In the case of from-abi, the macro names the resolved architecture (either "mips1" or "mips3"). It names the default architecture when no -march option is given. -mtune=arch Optimize for arch. Among other things, this option controls the way instructions are scheduled, and the perceived cost of arithmetic operations. The list of arch values is the same as for -march. When this option is not used, GCC optimizes for the processor specified by -march. By using -march and -mtune together, it is possible to generate code that runs on a family of processors, but optimize the code for one particular member of that family. -mtune defines the macros "_MIPS_TUNE" and "_MIPS_TUNE_foo", which work in the same way as the -march ones described above. -mips1 Equivalent to -march=mips1. -mips2 Equivalent to -march=mips2. -mips3 Equivalent to -march=mips3. -mips4 Equivalent to -march=mips4. -mips32 Equivalent to -march=mips32. -mips32r3 Equivalent to -march=mips32r3. -mips32r5 Equivalent to -march=mips32r5. -mips32r6 Equivalent to -march=mips32r6. -mips64 Equivalent to -march=mips64. -mips64r2 Equivalent to -march=mips64r2. -mips64r3 Equivalent to -march=mips64r3. -mips64r5 Equivalent to -march=mips64r5. -mips64r6 Equivalent to -march=mips64r6. -mips16 -mno-mips16 Generate (do not generate) MIPS16 code. If GCC is targeting a MIPS32 or MIPS64 architecture, it makes use of the MIPS16e ASE. MIPS16 code generation can also be controlled on a per-function basis by means of "mips16" and "nomips16" attributes. -mflip-mips16 Generate MIPS16 code on alternating functions. This option is provided for regression testing of mixed MIPS16/non-MIPS16 code generation, and is not intended for ordinary use in compiling user code. -minterlink-compressed -mno-interlink-compressed Require (do not require) that code using the standard (uncompressed) MIPS ISA be link-compatible with MIPS16 and microMIPS code, and vice versa. For example, code using the standard ISA encoding cannot jump directly to MIPS16 or microMIPS code; it must either use a call or an indirect jump. -minterlink-compressed therefore disables direct jumps unless GCC knows that the target of the jump is not compressed. -minterlink-mips16 -mno-interlink-mips16 Aliases of -minterlink-compressed and -mno-interlink-compressed. These options predate the microMIPS ASE and are retained for backwards compatibility. -mabi=32 -mabi=o64 -mabi=n32 -mabi=64 -mabi=eabi Generate code for the given ABI. Note that the EABI has a 32-bit and a 64-bit variant. GCC normally generates 64-bit code when you select a 64-bit architecture, but you can use -mgp32 to get 32-bit code instead. For information about the O64 ABI, see <https://gcc.gnu.org/projects/mipso64-abi.html>. GCC supports a variant of the o32 ABI in which floating-point registers are 64 rather than 32 bits wide. You can select this combination with -mabi=32 -mfp64. This ABI relies on the "mthc1" and "mfhc1" instructions and is therefore only supported for MIPS32R2, MIPS32R3 and MIPS32R5 processors. The register assignments for arguments and return values remain the same, but each scalar value is passed in a single 64-bit register rather than a pair of 32-bit registers. For example, scalar floating-point values are returned in $f0 only, not a $f0/$f1 pair. The set of call-saved registers also remains the same in that the even-numbered double-precision registers are saved. Two additional variants of the o32 ABI are supported to enable a transition from 32-bit to 64-bit registers. These are FPXX (-mfpxx) and FP64A (-mfp64 -mno-odd-spreg). The FPXX extension mandates that all code must execute correctly when run using 32-bit or 64-bit registers. The code can be interlinked with either FP32 or FP64, but not both. The FP64A extension is similar to the FP64 extension but forbids the use of odd-numbered single-precision registers. This can be used in conjunction with the "FRE" mode of FPUs in MIPS32R5 processors and allows both FP32 and FP64A code to interlink and run in the same process without changing FPU modes. -mabicalls -mno-abicalls Generate (do not generate) code that is suitable for SVR4-style dynamic objects. -mabicalls is the default for SVR4-based systems. -mshared -mno-shared Generate (do not generate) code that is fully position-independent, and that can therefore be linked into shared libraries. This option only affects -mabicalls. All -mabicalls code has traditionally been position-independent, regardless of options like -fPIC and -fpic. However, as an extension, the GNU toolchain allows executables to use absolute accesses for locally-binding symbols. It can also use shorter GP initialization sequences and generate direct calls to locally- defined functions. This mode is selected by -mno-shared. -mno-shared depends on binutils 2.16 or higher and generates objects that can only be linked by the GNU linker. However, the option does not affect the ABI of the final executable; it only affects the ABI of relocatable objects. Using -mno-shared generally makes executables both smaller and quicker. -mshared is the default. -mplt -mno-plt Assume (do not assume) that the static and dynamic linkers support PLTs and copy relocations. This option only affects -mno-shared -mabicalls. For the n64 ABI, this option has no effect without -msym32. You can make -mplt the default by configuring GCC with --with-mips-plt. The default is -mno-plt otherwise. -mxgot -mno-xgot Lift (do not lift) the usual restrictions on the size of the global offset table. GCC normally uses a single instruction to load values from the GOT. While this is relatively efficient, it only works if the GOT is smaller than about 64k. Anything larger causes the linker to report an error such as: relocation truncated to fit: R_MIPS_GOT16 foobar If this happens, you should recompile your code with -mxgot. This works with very large GOTs, although the code is also less efficient, since it takes three instructions to fetch the value of a global symbol. Note that some linkers can create multiple GOTs. If you have such a linker, you should only need to use -mxgot when a single object file accesses more than 64k's worth of GOT entries. Very few do. These options have no effect unless GCC is generating position independent code. -mgp32 Assume that general-purpose registers are 32 bits wide. -mgp64 Assume that general-purpose registers are 64 bits wide. -mfp32 Assume that floating-point registers are 32 bits wide. -mfp64 Assume that floating-point registers are 64 bits wide. -mfpxx Do not assume the width of floating-point registers. -mhard-float Use floating-point coprocessor instructions. -msoft-float Do not use floating-point coprocessor instructions. Implement floating-point calculations using library calls instead. -mno-float Equivalent to -msoft-float, but additionally asserts that the program being compiled does not perform any floating-point operations. This option is presently supported only by some bare- metal MIPS configurations, where it may select a special set of libraries that lack all floating-point support (including, for example, the floating-point "printf" formats). If code compiled with -mno-float accidentally contains floating-point operations, it is likely to suffer a link-time or run-time failure. -msingle-float Assume that the floating-point coprocessor only supports single- precision operations. -mdouble-float Assume that the floating-point coprocessor supports double- precision operations. This is the default. -modd-spreg -mno-odd-spreg Enable the use of odd-numbered single-precision floating-point registers for the o32 ABI. This is the default for processors that are known to support these registers. When using the o32 FPXX ABI, -mno-odd-spreg is set by default. -mabs=2008 -mabs=legacy These options control the treatment of the special not-a-number (NaN) IEEE 754 floating-point data with the "abs.fmt" and "neg.fmt" machine instructions. By default or when -mabs=legacy is used the legacy treatment is selected. In this case these instructions are considered arithmetic and avoided where correct operation is required and the input operand might be a NaN. A longer sequence of instructions that manipulate the sign bit of floating-point datum manually is used instead unless the -ffinite-math-only option has also been specified. The -mabs=2008 option selects the IEEE 754-2008 treatment. In this case these instructions are considered non-arithmetic and therefore operating correctly in all cases, including in particular where the input operand is a NaN. These instructions are therefore always used for the respective operations. -mnan=2008 -mnan=legacy These options control the encoding of the special not-a-number (NaN) IEEE 754 floating-point data. The -mnan=legacy option selects the legacy encoding. In this case quiet NaNs (qNaNs) are denoted by the first bit of their trailing significand field being 0, whereas signaling NaNs (sNaNs) are denoted by the first bit of their trailing significand field being 1. The -mnan=2008 option selects the IEEE 754-2008 encoding. In this case qNaNs are denoted by the first bit of their trailing significand field being 1, whereas sNaNs are denoted by the first bit of their trailing significand field being 0. The default is -mnan=legacy unless GCC has been configured with --with-nan=2008. -mllsc -mno-llsc Use (do not use) ll, sc, and sync instructions to implement atomic memory built-in functions. When neither option is specified, GCC uses the instructions if the target architecture supports them. -mllsc is useful if the runtime environment can emulate the instructions and -mno-llsc can be useful when compiling for nonstandard ISAs. You can make either option the default by configuring GCC with --with-llsc and --without-llsc respectively. --with-llsc is the default for some configurations; see the installation documentation for details. -mdsp -mno-dsp Use (do not use) revision 1 of the MIPS DSP ASE. This option defines the preprocessor macro "__mips_dsp". It also defines "__mips_dsp_rev" to 1. -mdspr2 -mno-dspr2 Use (do not use) revision 2 of the MIPS DSP ASE. This option defines the preprocessor macros "__mips_dsp" and "__mips_dspr2". It also defines "__mips_dsp_rev" to 2. -msmartmips -mno-smartmips Use (do not use) the MIPS SmartMIPS ASE. -mpaired-single -mno-paired-single Use (do not use) paired-single floating-point instructions. This option requires hardware floating-point support to be enabled. -mdmx -mno-mdmx Use (do not use) MIPS Digital Media Extension instructions. This option can only be used when generating 64-bit code and requires hardware floating-point support to be enabled. -mips3d -mno-mips3d Use (do not use) the MIPS-3D ASE. The option -mips3d implies -mpaired-single. -mmicromips -mno-micromips Generate (do not generate) microMIPS code. MicroMIPS code generation can also be controlled on a per-function basis by means of "micromips" and "nomicromips" attributes. -mmt -mno-mt Use (do not use) MT Multithreading instructions. -mmcu -mno-mcu Use (do not use) the MIPS MCU ASE instructions. -meva -mno-eva Use (do not use) the MIPS Enhanced Virtual Addressing instructions. -mvirt -mno-virt Use (do not use) the MIPS Virtualization (VZ) instructions. -mxpa -mno-xpa Use (do not use) the MIPS eXtended Physical Address (XPA) instructions. -mcrc -mno-crc Use (do not use) the MIPS Cyclic Redundancy Check (CRC) instructions. -mginv -mno-ginv Use (do not use) the MIPS Global INValidate (GINV) instructions. -mloongson-mmi -mno-loongson-mmi Use (do not use) the MIPS Loongson MultiMedia extensions Instructions (MMI). -mloongson-ext -mno-loongson-ext Use (do not use) the MIPS Loongson EXTensions (EXT) instructions. -mloongson-ext2 -mno-loongson-ext2 Use (do not use) the MIPS Loongson EXTensions r2 (EXT2) instructions. -mlong64 Force "long" types to be 64 bits wide. See -mlong32 for an explanation of the default and the way that the pointer size is determined. -mlong32 Force "long", "int", and pointer types to be 32 bits wide. The default size of "int"s, "long"s and pointers depends on the ABI. All the supported ABIs use 32-bit "int"s. The n64 ABI uses 64-bit "long"s, as does the 64-bit EABI; the others use 32-bit "long"s. Pointers are the same size as "long"s, or the same size as integer registers, whichever is smaller. -msym32 -mno-sym32 Assume (do not assume) that all symbols have 32-bit values, regardless of the selected ABI. This option is useful in combination with -mabi=64 and -mno-abicalls because it allows GCC to generate shorter and faster references to symbolic addresses. -G num Put definitions of externally-visible data in a small data section if that data is no bigger than num bytes. GCC can then generate more efficient accesses to the data; see -mgpopt for details. The default -G option depends on the configuration. -mlocal-sdata -mno-local-sdata Extend (do not extend) the -G behavior to local data too, such as to static variables in C. -mlocal-sdata is the default for all configurations. If the linker complains that an application is using too much small data, you might want to try rebuilding the less performance- critical parts with -mno-local-sdata. You might also want to build large libraries with -mno-local-sdata, so that the libraries leave more room for the main program. -mextern-sdata -mno-extern-sdata Assume (do not assume) that externally-defined data is in a small data section if the size of that data is within the -G limit. -mextern-sdata is the default for all configurations. If you compile a module Mod with -mextern-sdata -G num -mgpopt, and Mod references a variable Var that is no bigger than num bytes, you must make sure that Var is placed in a small data section. If Var is defined by another module, you must either compile that module with a high-enough -G setting or attach a "section" attribute to Var's definition. If Var is common, you must link the application with a high-enough -G setting. The easiest way of satisfying these restrictions is to compile and link every module with the same -G option. However, you may wish to build a library that supports several different small data limits. You can do this by compiling the library with the highest supported -G setting and additionally using -mno-extern-sdata to stop the library from making assumptions about externally-defined data. -mgpopt -mno-gpopt Use (do not use) GP-relative accesses for symbols that are known to be in a small data section; see -G, -mlocal-sdata and -mextern-sdata. -mgpopt is the default for all configurations. -mno-gpopt is useful for cases where the $gp register might not hold the value of "_gp". For example, if the code is part of a library that might be used in a boot monitor, programs that call boot monitor routines pass an unknown value in $gp. (In such situations, the boot monitor itself is usually compiled with -G0.) -mno-gpopt implies -mno-local-sdata and -mno-extern-sdata. -membedded-data -mno-embedded-data Allocate variables to the read-only data section first if possible, then next in the small data section if possible, otherwise in data. This gives slightly slower code than the default, but reduces the amount of RAM required when executing, and thus may be preferred for some embedded systems. -muninit-const-in-rodata -mno-uninit-const-in-rodata Put uninitialized "const" variables in the read-only data section. This option is only meaningful in conjunction with -membedded-data. -mcode-readable=setting Specify whether GCC may generate code that reads from executable sections. There are three possible settings: -mcode-readable=yes Instructions may freely access executable sections. This is the default setting. -mcode-readable=pcrel MIPS16 PC-relative load instructions can access executable sections, but other instructions must not do so. This option is useful on 4KSc and 4KSd processors when the code TLBs have the Read Inhibit bit set. It is also useful on processors that can be configured to have a dual instruction/data SRAM interface and that, like the M4K, automatically redirect PC- relative loads to the instruction RAM. -mcode-readable=no Instructions must not access executable sections. This option can be useful on targets that are configured to have a dual instruction/data SRAM interface but that (unlike the M4K) do not automatically redirect PC-relative loads to the instruction RAM. -msplit-addresses -mno-split-addresses Enable (disable) use of the "%hi()" and "%lo()" assembler relocation operators. This option has been superseded by -mexplicit-relocs but is retained for backwards compatibility. -mexplicit-relocs -mno-explicit-relocs Use (do not use) assembler relocation operators when dealing with symbolic addresses. The alternative, selected by -mno-explicit-relocs, is to use assembler macros instead. -mexplicit-relocs is the default if GCC was configured to use an assembler that supports relocation operators. -mcheck-zero-division -mno-check-zero-division Trap (do not trap) on integer division by zero. The default is -mcheck-zero-division. -mdivide-traps -mdivide-breaks MIPS systems check for division by zero by generating either a conditional trap or a break instruction. Using traps results in smaller code, but is only supported on MIPS II and later. Also, some versions of the Linux kernel have a bug that prevents trap from generating the proper signal ("SIGFPE"). Use -mdivide-traps to allow conditional traps on architectures that support them and -mdivide-breaks to force the use of breaks. The default is usually -mdivide-traps, but this can be overridden at configure time using --with-divide=breaks. Divide-by-zero checks can be completely disabled using -mno-check-zero-division. -mload-store-pairs -mno-load-store-pairs Enable (disable) an optimization that pairs consecutive load or store instructions to enable load/store bonding. This option is enabled by default but only takes effect when the selected architecture is known to support bonding. -munaligned-access -mno-unaligned-access Enable (disable) direct unaligned access for MIPS Release 6. MIPSr6 requires load/store unaligned-access support, by hardware or trap&emulate. So -mno-unaligned-access may be needed by kernel. -mmemcpy -mno-memcpy Force (do not force) the use of "memcpy" for non-trivial block moves. The default is -mno-memcpy, which allows GCC to inline most constant-sized copies. -mlong-calls -mno-long-calls Disable (do not disable) use of the "jal" instruction. Calling functions using "jal" is more efficient but requires the caller and callee to be in the same 256 megabyte segment. This option has no effect on abicalls code. The default is -mno-long-calls. -mmad -mno-mad Enable (disable) use of the "mad", "madu" and "mul" instructions, as provided by the R4650 ISA. -mimadd -mno-imadd Enable (disable) use of the "madd" and "msub" integer instructions. The default is -mimadd on architectures that support "madd" and "msub" except for the 74k architecture where it was found to generate slower code. -mfused-madd -mno-fused-madd Enable (disable) use of the floating-point multiply-accumulate instructions, when they are available. The default is -mfused-madd. On the R8000 CPU when multiply-accumulate instructions are used, the intermediate product is calculated to infinite precision and is not subject to the FCSR Flush to Zero bit. This may be undesirable in some circumstances. On other processors the result is numerically identical to the equivalent computation using separate multiply, add, subtract and negate instructions. -nocpp Tell the MIPS assembler to not run its preprocessor over user assembler files (with a .s suffix) when assembling them. -mfix-24k -mno-fix-24k Work around the 24K E48 (lost data on stores during refill) errata. The workarounds are implemented by the assembler rather than by GCC. -mfix-r4000 -mno-fix-r4000 Work around certain R4000 CPU errata: - A double-word or a variable shift may give an incorrect result if executed immediately after starting an integer division. - A double-word or a variable shift may give an incorrect result if executed while an integer multiplication is in progress. - An integer division may give an incorrect result if started in a delay slot of a taken branch or a jump. -mfix-r4400 -mno-fix-r4400 Work around certain R4400 CPU errata: - A double-word or a variable shift may give an incorrect result if executed immediately after starting an integer division. -mfix-r10000 -mno-fix-r10000 Work around certain R10000 errata: - "ll"/"sc" sequences may not behave atomically on revisions prior to 3.0. They may deadlock on revisions 2.6 and earlier. This option can only be used if the target architecture supports branch-likely instructions. -mfix-r10000 is the default when -march=r10000 is used; -mno-fix-r10000 is the default otherwise. -mfix-r5900 -mno-fix-r5900 Do not attempt to schedule the preceding instruction into the delay slot of a branch instruction placed at the end of a short loop of six instructions or fewer and always schedule a "nop" instruction there instead. The short loop bug under certain conditions causes loops to execute only once or twice, due to a hardware bug in the R5900 chip. The workaround is implemented by the assembler rather than by GCC. -mfix-rm7000 -mno-fix-rm7000 Work around the RM7000 "dmult"/"dmultu" errata. The workarounds are implemented by the assembler rather than by GCC. -mfix-vr4120 -mno-fix-vr4120 Work around certain VR4120 errata: - "dmultu" does not always produce the correct result. - "div" and "ddiv" do not always produce the correct result if one of the operands is negative. The workarounds for the division errata rely on special functions in libgcc.a. At present, these functions are only provided by the "mips64vr*-elf" configurations. Other VR4120 errata require a NOP to be inserted between certain pairs of instructions. These errata are handled by the assembler, not by GCC itself. -mfix-vr4130 Work around the VR4130 "mflo"/"mfhi" errata. The workarounds are implemented by the assembler rather than by GCC, although GCC avoids using "mflo" and "mfhi" if the VR4130 "macc", "macchi", "dmacc" and "dmacchi" instructions are available instead. -mfix-sb1 -mno-fix-sb1 Work around certain SB-1 CPU core errata. (This flag currently works around the SB-1 revision 2 "F1" and "F2" floating-point errata.) -mr10k-cache-barrier=setting Specify whether GCC should insert cache barriers to avoid the side effects of speculation on R10K processors. In common with many processors, the R10K tries to predict the outcome of a conditional branch and speculatively executes instructions from the "taken" branch. It later aborts these instructions if the predicted outcome is wrong. However, on the R10K, even aborted instructions can have side effects. This problem only affects kernel stores and, depending on the system, kernel loads. As an example, a speculatively-executed store may load the target memory into cache and mark the cache line as dirty, even if the store itself is later aborted. If a DMA operation writes to the same area of memory before the "dirty" line is flushed, the cached data overwrites the DMA-ed data. See the R10K processor manual for a full description, including other potential problems. One workaround is to insert cache barrier instructions before every memory access that might be speculatively executed and that might have side effects even if aborted. -mr10k-cache-barrier=setting controls GCC's implementation of this workaround. It assumes that aborted accesses to any byte in the following regions does not have side effects: 1. the memory occupied by the current function's stack frame; 2. the memory occupied by an incoming stack argument; 3. the memory occupied by an object with a link-time-constant address. It is the kernel's responsibility to ensure that speculative accesses to these regions are indeed safe. If the input program contains a function declaration such as: void foo (void); then the implementation of "foo" must allow "j foo" and "jal foo" to be executed speculatively. GCC honors this restriction for functions it compiles itself. It expects non-GCC functions (such as hand-written assembly code) to do the same. The option has three forms: -mr10k-cache-barrier=load-store Insert a cache barrier before a load or store that might be speculatively executed and that might have side effects even if aborted. -mr10k-cache-barrier=store Insert a cache barrier before a store that might be speculatively executed and that might have side effects even if aborted. -mr10k-cache-barrier=none Disable the insertion of cache barriers. This is the default setting. -mflush-func=func -mno-flush-func Specifies the function to call to flush the I and D caches, or to not call any such function. If called, the function must take the same arguments as the common "_flush_func", that is, the address of the memory range for which the cache is being flushed, the size of the memory range, and the number 3 (to flush both caches). The default depends on the target GCC was configured for, but commonly is either "_flush_func" or "__cpu_flush". mbranch-cost=num Set the cost of branches to roughly num "simple" instructions. This cost is only a heuristic and is not guaranteed to produce consistent results across releases. A zero cost redundantly selects the default, which is based on the -mtune setting. -mbranch-likely -mno-branch-likely Enable or disable use of Branch Likely instructions, regardless of the default for the selected architecture. By default, Branch Likely instructions may be generated if they are supported by the selected architecture. An exception is for the MIPS32 and MIPS64 architectures and processors that implement those architectures; for those, Branch Likely instructions are not be generated by default because the MIPS32 and MIPS64 architectures specifically deprecate their use. -mcompact-branches=never -mcompact-branches=optimal -mcompact-branches=always These options control which form of branches will be generated. The default is -mcompact-branches=optimal. The -mcompact-branches=never option ensures that compact branch instructions will never be generated. The -mcompact-branches=always option ensures that a compact branch instruction will be generated if available for MIPS Release 6 onwards. If a compact branch instruction is not available (or pre-R6), a delay slot form of the branch will be used instead. If it is used for MIPS16/microMIPS targets, it will be just ignored now. The behaviour for MIPS16/microMIPS may change in future, since they do have some compact branch instructions. The -mcompact-branches=optimal option will cause a delay slot branch to be used if one is available in the current ISA and the delay slot is successfully filled. If the delay slot is not filled, a compact branch will be chosen if one is available. -mfp-exceptions -mno-fp-exceptions Specifies whether FP exceptions are enabled. This affects how FP instructions are scheduled for some processors. The default is that FP exceptions are enabled. For instance, on the SB-1, if FP exceptions are disabled, and we are emitting 64-bit code, then we can use both FP pipes. Otherwise, we can only use one FP pipe. -mvr4130-align -mno-vr4130-align The VR4130 pipeline is two-way superscalar, but can only issue two instructions together if the first one is 8-byte aligned. When this option is enabled, GCC aligns pairs of instructions that it thinks should execute in parallel. This option only has an effect when optimizing for the VR4130. It normally makes code faster, but at the expense of making it bigger. It is enabled by default at optimization level -O3. -msynci -mno-synci Enable (disable) generation of "synci" instructions on architectures that support it. The "synci" instructions (if enabled) are generated when "__builtin___clear_cache" is compiled. This option defaults to -mno-synci, but the default can be overridden by configuring GCC with --with-synci. When compiling code for single processor systems, it is generally safe to use "synci". However, on many multi-core (SMP) systems, it does not invalidate the instruction caches on all cores and may lead to undefined behavior. -mrelax-pic-calls -mno-relax-pic-calls Try to turn PIC calls that are normally dispatched via register $25 into direct calls. This is only possible if the linker can resolve the destination at link time and if the destination is within range for a direct call. -mrelax-pic-calls is the default if GCC was configured to use an assembler and a linker that support the ".reloc" assembly directive and -mexplicit-relocs is in effect. With -mno-explicit-relocs, this optimization can be performed by the assembler and the linker alone without help from the compiler. -mmcount-ra-address -mno-mcount-ra-address Emit (do not emit) code that allows "_mcount" to modify the calling function's return address. When enabled, this option extends the usual "_mcount" interface with a new ra-address parameter, which has type "intptr_t *" and is passed in register $12. "_mcount" can then modify the return address by doing both of the following: * Returning the new address in register $31. * Storing the new address in "*ra-address", if ra-address is nonnull. The default is -mno-mcount-ra-address. -mframe-header-opt -mno-frame-header-opt Enable (disable) frame header optimization in the o32 ABI. When using the o32 ABI, calling functions will allocate 16 bytes on the stack for the called function to write out register arguments. When enabled, this optimization will suppress the allocation of the frame header if it can be determined that it is unused. This optimization is off by default at all optimization levels. -mlxc1-sxc1 -mno-lxc1-sxc1 When applicable, enable (disable) the generation of "lwxc1", "swxc1", "ldxc1", "sdxc1" instructions. Enabled by default. -mmadd4 -mno-madd4 When applicable, enable (disable) the generation of 4-operand "madd.s", "madd.d" and related instructions. Enabled by default. MMIX Options These options are defined for the MMIX: -mlibfuncs -mno-libfuncs Specify that intrinsic library functions are being compiled, passing all values in registers, no matter the size. -mepsilon -mno-epsilon Generate floating-point comparison instructions that compare with respect to the "rE" epsilon register. -mabi=mmixware -mabi=gnu Generate code that passes function parameters and return values that (in the called function) are seen as registers $0 and up, as opposed to the GNU ABI which uses global registers $231 and up. -mzero-extend -mno-zero-extend When reading data from memory in sizes shorter than 64 bits, use (do not use) zero-extending load instructions by default, rather than sign-extending ones. -mknuthdiv -mno-knuthdiv Make the result of a division yielding a remainder have the same sign as the divisor. With the default, -mno-knuthdiv, the sign of the remainder follows the sign of the dividend. Both methods are arithmetically valid, the latter being almost exclusively used. -mtoplevel-symbols -mno-toplevel-symbols Prepend (do not prepend) a : to all global symbols, so the assembly code can be used with the "PREFIX" assembly directive. -melf Generate an executable in the ELF format, rather than the default mmo format used by the mmix simulator. -mbranch-predict -mno-branch-predict Use (do not use) the probable-branch instructions, when static branch prediction indicates a probable branch. -mbase-addresses -mno-base-addresses Generate (do not generate) code that uses base addresses. Using a base address automatically generates a request (handled by the assembler and the linker) for a constant to be set up in a global register. The register is used for one or more base address requests within the range 0 to 255 from the value held in the register. The generally leads to short and fast code, but the number of different data items that can be addressed is limited. This means that a program that uses lots of static data may require -mno-base-addresses. -msingle-exit -mno-single-exit Force (do not force) generated code to have a single exit point in each function. MN10300 Options These -m options are defined for Matsushita MN10300 architectures: -mmult-bug Generate code to avoid bugs in the multiply instructions for the MN10300 processors. This is the default. -mno-mult-bug Do not generate code to avoid bugs in the multiply instructions for the MN10300 processors. -mam33 Generate code using features specific to the AM33 processor. -mno-am33 Do not generate code using features specific to the AM33 processor. This is the default. -mam33-2 Generate code using features specific to the AM33/2.0 processor. -mam34 Generate code using features specific to the AM34 processor. -mtune=cpu-type Use the timing characteristics of the indicated CPU type when scheduling instructions. This does not change the targeted processor type. The CPU type must be one of mn10300, am33, am33-2 or am34. -mreturn-pointer-on-d0 When generating a function that returns a pointer, return the pointer in both "a0" and "d0". Otherwise, the pointer is returned only in "a0", and attempts to call such functions without a prototype result in errors. Note that this option is on by default; use -mno-return-pointer-on-d0 to disable it. -mno-crt0 Do not link in the C run-time initialization object file. -mrelax Indicate to the linker that it should perform a relaxation optimization pass to shorten branches, calls and absolute memory addresses. This option only has an effect when used on the command line for the final link step. This option makes symbolic debugging impossible. -mliw Allow the compiler to generate Long Instruction Word instructions if the target is the AM33 or later. This is the default. This option defines the preprocessor macro "__LIW__". -mno-liw Do not allow the compiler to generate Long Instruction Word instructions. This option defines the preprocessor macro "__NO_LIW__". -msetlb Allow the compiler to generate the SETLB and Lcc instructions if the target is the AM33 or later. This is the default. This option defines the preprocessor macro "__SETLB__". -mno-setlb Do not allow the compiler to generate SETLB or Lcc instructions. This option defines the preprocessor macro "__NO_SETLB__". Moxie Options -meb Generate big-endian code. This is the default for moxie-*-* configurations. -mel Generate little-endian code. -mmul.x Generate mul.x and umul.x instructions. This is the default for moxiebox-*-* configurations. -mno-crt0 Do not link in the C run-time initialization object file. MSP430 Options These options are defined for the MSP430: -masm-hex Force assembly output to always use hex constants. Normally such constants are signed decimals, but this option is available for testsuite and/or aesthetic purposes. -mmcu= Select the MCU to target. This is used to create a C preprocessor symbol based upon the MCU name, converted to upper case and pre- and post-fixed with __. This in turn is used by the msp430.h header file to select an MCU-specific supplementary header file. The option also sets the ISA to use. If the MCU name is one that is known to only support the 430 ISA then that is selected, otherwise the 430X ISA is selected. A generic MCU name of msp430 can also be used to select the 430 ISA. Similarly the generic msp430x MCU name selects the 430X ISA. In addition an MCU-specific linker script is added to the linker command line. The script's name is the name of the MCU with .ld appended. Thus specifying -mmcu=xxx on the gcc command line defines the C preprocessor symbol "__XXX__" and cause the linker to search for a script called xxx.ld. The ISA and hardware multiply supported for the different MCUs is hard-coded into GCC. However, an external devices.csv file can be used to extend device support beyond those that have been hard- coded. GCC searches for the devices.csv file using the following methods in the given precedence order, where the first method takes precendence over the second which takes precedence over the third. Include path specified with "-I" and "-L" devices.csv will be searched for in each of the directories specified by include paths and linker library search paths. Path specified by the environment variable MSP430_GCC_INCLUDE_DIR Define the value of the global environment variable MSP430_GCC_INCLUDE_DIR to the full path to the directory containing devices.csv, and GCC will search this directory for devices.csv. If devices.csv is found, this directory will also be registered as an include path, and linker library path. Header files and linker scripts in this directory can therefore be used without manually specifying "-I" and "-L" on the command line. The msp430-elf{,bare}/include/devices directory Finally, GCC will examine msp430-elf{,bare}/include/devices from the toolchain root directory. This directory does not exist in a default installation, but if the user has created it and copied devices.csv there, then the MCU data will be read. As above, this directory will also be registered as an include path, and linker library path. If none of the above search methods find devices.csv, then the hard-coded MCU data is used. -mwarn-mcu -mno-warn-mcu This option enables or disables warnings about conflicts between the MCU name specified by the -mmcu option and the ISA set by the -mcpu option and/or the hardware multiply support set by the -mhwmult option. It also toggles warnings about unrecognized MCU names. This option is on by default. -mcpu= Specifies the ISA to use. Accepted values are msp430, msp430x and msp430xv2. This option is deprecated. The -mmcu= option should be used to select the ISA. -msim Link to the simulator runtime libraries and linker script. Overrides any scripts that would be selected by the -mmcu= option. -mlarge Use large-model addressing (20-bit pointers, 20-bit "size_t"). -msmall Use small-model addressing (16-bit pointers, 16-bit "size_t"). -mrelax This option is passed to the assembler and linker, and allows the linker to perform certain optimizations that cannot be done until the final link. mhwmult= Describes the type of hardware multiply supported by the target. Accepted values are none for no hardware multiply, 16bit for the original 16-bit-only multiply supported by early MCUs. 32bit for the 16/32-bit multiply supported by later MCUs and f5series for the 16/32-bit multiply supported by F5-series MCUs. A value of auto can also be given. This tells GCC to deduce the hardware multiply support based upon the MCU name provided by the -mmcu option. If no -mmcu option is specified or if the MCU name is not recognized then no hardware multiply support is assumed. "auto" is the default setting. Hardware multiplies are normally performed by calling a library routine. This saves space in the generated code. When compiling at -O3 or higher however the hardware multiplier is invoked inline. This makes for bigger, but faster code. The hardware multiply routines disable interrupts whilst running and restore the previous interrupt state when they finish. This makes them safe to use inside interrupt handlers as well as in normal code. -minrt Enable the use of a minimum runtime environment - no static initializers or constructors. This is intended for memory- constrained devices. The compiler includes special symbols in some objects that tell the linker and runtime which code fragments are required. -mtiny-printf Enable reduced code size "printf" and "puts" library functions. The tiny implementations of these functions are not reentrant, so must be used with caution in multi-threaded applications. Support for streams has been removed and the string to be printed will always be sent to stdout via the "write" syscall. The string is not buffered before it is sent to write. This option requires Newlib Nano IO, so GCC must be configured with --enable-newlib-nano-formatted-io. -mmax-inline-shift= This option takes an integer between 0 and 64 inclusive, and sets the maximum number of inline shift instructions which should be emitted to perform a shift operation by a constant amount. When this value needs to be exceeded, an mspabi helper function is used instead. The default value is 4. This only affects cases where a shift by multiple positions cannot be completed with a single instruction (e.g. all shifts >1 on the 430 ISA). Shifts of a 32-bit value are at least twice as costly, so the value passed for this option is divided by 2 and the resulting value used instead. -mcode-region= -mdata-region= These options tell the compiler where to place functions and data that do not have one of the "lower", "upper", "either" or "section" attributes. Possible values are "lower", "upper", "either" or "any". The first three behave like the corresponding attribute. The fourth possible value - "any" - is the default. It leaves placement entirely up to the linker script and how it assigns the standard sections (".text", ".data", etc) to the memory regions. -msilicon-errata= This option passes on a request to assembler to enable the fixes for the named silicon errata. -msilicon-errata-warn= This option passes on a request to the assembler to enable warning messages when a silicon errata might need to be applied. -mwarn-devices-csv -mno-warn-devices-csv Warn if devices.csv is not found or there are problem parsing it (default: on). NDS32 Options These options are defined for NDS32 implementations: -mbig-endian Generate code in big-endian mode. -mlittle-endian Generate code in little-endian mode. -mreduced-regs Use reduced-set registers for register allocation. -mfull-regs Use full-set registers for register allocation. -mcmov Generate conditional move instructions. -mno-cmov Do not generate conditional move instructions. -mext-perf Generate performance extension instructions. -mno-ext-perf Do not generate performance extension instructions. -mext-perf2 Generate performance extension 2 instructions. -mno-ext-perf2 Do not generate performance extension 2 instructions. -mext-string Generate string extension instructions. -mno-ext-string Do not generate string extension instructions. -mv3push Generate v3 push25/pop25 instructions. -mno-v3push Do not generate v3 push25/pop25 instructions. -m16-bit Generate 16-bit instructions. -mno-16-bit Do not generate 16-bit instructions. -misr-vector-size=num Specify the size of each interrupt vector, which must be 4 or 16. -mcache-block-size=num Specify the size of each cache block, which must be a power of 2 between 4 and 512. -march=arch Specify the name of the target architecture. -mcmodel=code-model Set the code model to one of small All the data and read-only data segments must be within 512KB addressing space. The text segment must be within 16MB addressing space. medium The data segment must be within 512KB while the read-only data segment can be within 4GB addressing space. The text segment should be still within 16MB addressing space. large All the text and data segments can be within 4GB addressing space. -mctor-dtor Enable constructor/destructor feature. -mrelax Guide linker to relax instructions. Nios II Options These are the options defined for the Altera Nios II processor. -G num Put global and static objects less than or equal to num bytes into the small data or BSS sections instead of the normal data or BSS sections. The default value of num is 8. -mgpopt=option -mgpopt -mno-gpopt Generate (do not generate) GP-relative accesses. The following option names are recognized: none Do not generate GP-relative accesses. local Generate GP-relative accesses for small data objects that are not external, weak, or uninitialized common symbols. Also use GP-relative addressing for objects that have been explicitly placed in a small data section via a "section" attribute. global As for local, but also generate GP-relative accesses for small data objects that are external, weak, or common. If you use this option, you must ensure that all parts of your program (including libraries) are compiled with the same -G setting. data Generate GP-relative accesses for all data objects in the program. If you use this option, the entire data and BSS segments of your program must fit in 64K of memory and you must use an appropriate linker script to allocate them within the addressable range of the global pointer. all Generate GP-relative addresses for function pointers as well as data pointers. If you use this option, the entire text, data, and BSS segments of your program must fit in 64K of memory and you must use an appropriate linker script to allocate them within the addressable range of the global pointer. -mgpopt is equivalent to -mgpopt=local, and -mno-gpopt is equivalent to -mgpopt=none. The default is -mgpopt except when -fpic or -fPIC is specified to generate position-independent code. Note that the Nios II ABI does not permit GP-relative accesses from shared libraries. You may need to specify -mno-gpopt explicitly when building programs that include large amounts of small data, including large GOT data sections. In this case, the 16-bit offset for GP-relative addressing may not be large enough to allow access to the entire small data section. -mgprel-sec=regexp This option specifies additional section names that can be accessed via GP-relative addressing. It is most useful in conjunction with "section" attributes on variable declarations and a custom linker script. The regexp is a POSIX Extended Regular Expression. This option does not affect the behavior of the -G option, and the specified sections are in addition to the standard ".sdata" and ".sbss" small-data sections that are recognized by -mgpopt. -mr0rel-sec=regexp This option specifies names of sections that can be accessed via a 16-bit offset from "r0"; that is, in the low 32K or high 32K of the 32-bit address space. It is most useful in conjunction with "section" attributes on variable declarations and a custom linker script. The regexp is a POSIX Extended Regular Expression. In contrast to the use of GP-relative addressing for small data, zero-based addressing is never generated by default and there are no conventional section names used in standard linker scripts for sections in the low or high areas of memory. -mel -meb Generate little-endian (default) or big-endian (experimental) code, respectively. -march=arch This specifies the name of the target Nios II architecture. GCC uses this name to determine what kind of instructions it can emit when generating assembly code. Permissible names are: r1, r2. The preprocessor macro "__nios2_arch__" is available to programs, with value 1 or 2, indicating the targeted ISA level. -mbypass-cache -mno-bypass-cache Force all load and store instructions to always bypass cache by using I/O variants of the instructions. The default is not to bypass the cache. -mno-cache-volatile -mcache-volatile Volatile memory access bypass the cache using the I/O variants of the load and store instructions. The default is not to bypass the cache. -mno-fast-sw-div -mfast-sw-div Do not use table-based fast divide for small numbers. The default is to use the fast divide at -O3 and above. -mno-hw-mul -mhw-mul -mno-hw-mulx -mhw-mulx -mno-hw-div -mhw-div Enable or disable emitting "mul", "mulx" and "div" family of instructions by the compiler. The default is to emit "mul" and not emit "div" and "mulx". -mbmx -mno-bmx -mcdx -mno-cdx Enable or disable generation of Nios II R2 BMX (bit manipulation) and CDX (code density) instructions. Enabling these instructions also requires -march=r2. Since these instructions are optional extensions to the R2 architecture, the default is not to emit them. -mcustom-insn=N -mno-custom-insn Each -mcustom-insn=N option enables use of a custom instruction with encoding N when generating code that uses insn. For example, -mcustom-fadds=253 generates custom instruction 253 for single- precision floating-point add operations instead of the default behavior of using a library call. The following values of insn are supported. Except as otherwise noted, floating-point operations are expected to be implemented with normal IEEE 754 semantics and correspond directly to the C operators or the equivalent GCC built-in functions. Single-precision floating point: fadds, fsubs, fdivs, fmuls Binary arithmetic operations. fnegs Unary negation. fabss Unary absolute value. fcmpeqs, fcmpges, fcmpgts, fcmples, fcmplts, fcmpnes Comparison operations. fmins, fmaxs Floating-point minimum and maximum. These instructions are only generated if -ffinite-math-only is specified. fsqrts Unary square root operation. fcoss, fsins, ftans, fatans, fexps, flogs Floating-point trigonometric and exponential functions. These instructions are only generated if -funsafe-math-optimizations is also specified. Double-precision floating point: faddd, fsubd, fdivd, fmuld Binary arithmetic operations. fnegd Unary negation. fabsd Unary absolute value. fcmpeqd, fcmpged, fcmpgtd, fcmpled, fcmpltd, fcmpned Comparison operations. fmind, fmaxd Double-precision minimum and maximum. These instructions are only generated if -ffinite-math-only is specified. fsqrtd Unary square root operation. fcosd, fsind, ftand, fatand, fexpd, flogd Double-precision trigonometric and exponential functions. These instructions are only generated if -funsafe-math-optimizations is also specified. Conversions: fextsd Conversion from single precision to double precision. ftruncds Conversion from double precision to single precision. fixsi, fixsu, fixdi, fixdu Conversion from floating point to signed or unsigned integer types, with truncation towards zero. round Conversion from single-precision floating point to signed integer, rounding to the nearest integer and ties away from zero. This corresponds to the "__builtin_lroundf" function when -fno-math-errno is used. floatis, floatus, floatid, floatud Conversion from signed or unsigned integer types to floating- point types. In addition, all of the following transfer instructions for internal registers X and Y must be provided to use any of the double-precision floating-point instructions. Custom instructions taking two double-precision source operands expect the first operand in the 64-bit register X. The other operand (or only operand of a unary operation) is given to the custom arithmetic instruction with the least significant half in source register src1 and the most significant half in src2. A custom instruction that returns a double-precision result returns the most significant 32 bits in the destination register and the other half in 32-bit register Y. GCC automatically generates the necessary code sequences to write register X and/or read register Y when double- precision floating-point instructions are used. fwrx Write src1 into the least significant half of X and src2 into the most significant half of X. fwry Write src1 into Y. frdxhi, frdxlo Read the most or least (respectively) significant half of X and store it in dest. frdy Read the value of Y and store it into dest. Note that you can gain more local control over generation of Nios II custom instructions by using the "target("custom-insn=N")" and "target("no-custom-insn")" function attributes or pragmas. -mcustom-fpu-cfg=name This option enables a predefined, named set of custom instruction encodings (see -mcustom-insn above). Currently, the following sets are defined: -mcustom-fpu-cfg=60-1 is equivalent to: -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254 -fsingle-precision-constant -mcustom-fpu-cfg=60-2 is equivalent to: -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255 -fsingle-precision-constant -mcustom-fpu-cfg=72-3 is equivalent to: -mcustom-floatus=243 -mcustom-fixsi=244 -mcustom-floatis=245 -mcustom-fcmpgts=246 -mcustom-fcmples=249 -mcustom-fcmpeqs=250 -mcustom-fcmpnes=251 -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255 -fsingle-precision-constant -mcustom-fpu-cfg=fph2 is equivalent to: -mcustom-fabss=224 -mcustom-fnegs=225 -mcustom-fcmpnes=226 -mcustom-fcmpeqs=227 -mcustom-fcmpges=228 -mcustom-fcmpgts=229 -mcustom-fcmples=230 -mcustom-fcmplts=231 -mcustom-fmaxs=232 -mcustom-fmins=233 -mcustom-round=248 -mcustom-fixsi=249 -mcustom-floatis=250 -mcustom-fsqrts=251 -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255 Custom instruction assignments given by individual -mcustom-insn= options override those given by -mcustom-fpu-cfg=, regardless of the order of the options on the command line. Note that you can gain more local control over selection of a FPU configuration by using the "target("custom-fpu-cfg=name")" function attribute or pragma. The name fph2 is an abbreviation for Nios II Floating Point Hardware 2 Component. Please note that the custom instructions enabled by -mcustom-fmins=233 and -mcustom-fmaxs=234 are only generated if -ffinite-math-only is specified. The custom instruction enabled by -mcustom-round=248 is only generated if -fno-math-errno is specified. In contrast to the other configurations, -fsingle-precision-constant is not set. These additional -m options are available for the Altera Nios II ELF (bare-metal) target: -mhal Link with HAL BSP. This suppresses linking with the GCC-provided C runtime startup and termination code, and is typically used in conjunction with -msys-crt0= to specify the location of the alternate startup code provided by the HAL BSP. -msmallc Link with a limited version of the C library, -lsmallc, rather than Newlib. -msys-crt0=startfile startfile is the file name of the startfile (crt0) to use when linking. This option is only useful in conjunction with -mhal. -msys-lib=systemlib systemlib is the library name of the library that provides low- level system calls required by the C library, e.g. "read" and "write". This option is typically used to link with a library provided by a HAL BSP. Nvidia PTX Options These options are defined for Nvidia PTX: -m64 Ignored, but preserved for backward compatibility. Only 64-bit ABI is supported. -march=architecture-string Generate code for the specified PTX ISA target architecture (e.g. sm_35). Valid architecture strings are sm_30, sm_35, sm_53, sm_70, sm_75 and sm_80. The default depends on how the compiler has been configured, see --with-arch. This option sets the value of the preprocessor macro "__PTX_SM__"; for instance, for sm_35, it has the value 350. -misa=architecture-string Alias of -march=. -march-map=architecture-string Select the closest available -march= value that is not more capable. For instance, for -march-map=sm_50 select -march=sm_35, and for -march-map=sm_53 select -march=sm_53. -mptx=version-string Generate code for the specified PTX ISA version (e.g. 7.0). Valid version strings include 3.1, 6.0, 6.3, and 7.0. The default PTX ISA version is 6.0, unless a higher version is required for specified PTX ISA target architecture via option -march=. This option sets the values of the preprocessor macros "__PTX_ISA_VERSION_MAJOR__" and "__PTX_ISA_VERSION_MINOR__"; for instance, for 3.1 the macros have the values 3 and 1, respectively. -mmainkernel Link in code for a __main kernel. This is for stand-alone instead of offloading execution. -moptimize Apply partitioned execution optimizations. This is the default when any level of optimization is selected. -msoft-stack Generate code that does not use ".local" memory directly for stack storage. Instead, a per-warp stack pointer is maintained explicitly. This enables variable-length stack allocation (with variable-length arrays or "alloca"), and when global memory is used for underlying storage, makes it possible to access automatic variables from other threads, or with atomic instructions. This code generation variant is used for OpenMP offloading, but the option is exposed on its own for the purpose of testing the compiler; to generate code suitable for linking into programs using OpenMP offloading, use option -mgomp. -muniform-simt Switch to code generation variant that allows to execute all threads in each warp, while maintaining memory state and side effects as if only one thread in each warp was active outside of OpenMP SIMD regions. All atomic operations and calls to runtime (malloc, free, vprintf) are conditionally executed (iff current lane index equals the master lane index), and the register being assigned is copied via a shuffle instruction from the master lane. Outside of SIMD regions lane 0 is the master; inside, each thread sees itself as the master. Shared memory array "int __nvptx_uni[]" stores all-zeros or all-ones bitmasks for each warp, indicating current mode (0 outside of SIMD regions). Each thread can bitwise- and the bitmask at position "tid.y" with current lane index to compute the master lane index. -mgomp Generate code for use in OpenMP offloading: enables -msoft-stack and -muniform-simt options, and selects corresponding multilib variant. OpenRISC Options These options are defined for OpenRISC: -mboard=name Configure a board specific runtime. This will be passed to the linker for newlib board library linking. The default is "or1ksim". -mnewlib This option is ignored; it is for compatibility purposes only. This used to select linker and preprocessor options for use with newlib. -msoft-div -mhard-div Select software or hardware divide ("l.div", "l.divu") instructions. This default is hardware divide. -msoft-mul -mhard-mul Select software or hardware multiply ("l.mul", "l.muli") instructions. This default is hardware multiply. -msoft-float -mhard-float Select software or hardware for floating point operations. The default is software. -mdouble-float When -mhard-float is selected, enables generation of double- precision floating point instructions. By default functions from libgcc are used to perform double-precision floating point operations. -munordered-float When -mhard-float is selected, enables generation of unordered floating point compare and set flag ("lf.sfun*") instructions. By default functions from libgcc are used to perform unordered floating point compare and set flag operations. -mcmov Enable generation of conditional move ("l.cmov") instructions. By default the equivalent will be generated using set and branch. -mror Enable generation of rotate right ("l.ror") instructions. By default functions from libgcc are used to perform rotate right operations. -mrori Enable generation of rotate right with immediate ("l.rori") instructions. By default functions from libgcc are used to perform rotate right with immediate operations. -msext Enable generation of sign extension ("l.ext*") instructions. By default memory loads are used to perform sign extension. -msfimm Enable generation of compare and set flag with immediate ("l.sf*i") instructions. By default extra instructions will be generated to store the immediate to a register first. -mshftimm Enable generation of shift with immediate ("l.srai", "l.srli", "l.slli") instructions. By default extra instructions will be generated to store the immediate to a register first. -mcmodel=small Generate OpenRISC code for the small model: The GOT is limited to 64k. This is the default model. -mcmodel=large Generate OpenRISC code for the large model: The GOT may grow up to 4G in size. PDP-11 Options These options are defined for the PDP-11: -mfpu Use hardware FPP floating point. This is the default. (FIS floating point on the PDP-11/40 is not supported.) Implies -m45. -msoft-float Do not use hardware floating point. -mac0 Return floating-point results in ac0 (fr0 in Unix assembler syntax). -mno-ac0 Return floating-point results in memory. This is the default. -m40 Generate code for a PDP-11/40. Implies -msoft-float -mno-split. -m45 Generate code for a PDP-11/45. This is the default. -m10 Generate code for a PDP-11/10. Implies -msoft-float -mno-split. -mint16 -mno-int32 Use 16-bit "int". This is the default. -mint32 -mno-int16 Use 32-bit "int". -msplit Target has split instruction and data space. Implies -m45. -munix-asm Use Unix assembler syntax. -mdec-asm Use DEC assembler syntax. -mgnu-asm Use GNU assembler syntax. This is the default. -mlra Use the new LRA register allocator. By default, the old "reload" allocator is used. PowerPC Options These are listed under PRU Options These command-line options are defined for PRU target: -minrt Link with a minimum runtime environment, with no support for static initializers and constructors. Using this option can significantly reduce the size of the final ELF binary. Beware that the compiler could still generate code with static initializers and constructors. It is up to the programmer to ensure that the source program will not use those features. -mmcu=mcu Specify the PRU MCU variant to use. Check Newlib for the exact list of supported MCUs. -mno-relax Make GCC pass the --no-relax command-line option to the linker instead of the --relax option. -mloop Allow (or do not allow) GCC to use the LOOP instruction. -mabi=variant Specify the ABI variant to output code for. -mabi=ti selects the unmodified TI ABI while -mabi=gnu selects a GNU variant that copes more naturally with certain GCC assumptions. These are the differences: Function Pointer Size TI ABI specifies that function (code) pointers are 16-bit, whereas GNU supports only 32-bit data and code pointers. Optional Return Value Pointer Function return values larger than 64 bits are passed by using a hidden pointer as the first argument of the function. TI ABI, though, mandates that the pointer can be NULL in case the caller is not using the returned value. GNU always passes and expects a valid return value pointer. The current -mabi=ti implementation simply raises a compile error when any of the above code constructs is detected. As a consequence the standard C library cannot be built and it is omitted when linking with -mabi=ti. Relaxation is a GNU feature and for safety reasons is disabled when using -mabi=ti. The TI toolchain does not emit relocations for QBBx instructions, so the GNU linker cannot adjust them when shortening adjacent LDI32 pseudo instructions. RISC-V Options These command-line options are defined for RISC-V targets: -mbranch-cost=n Set the cost of branches to roughly n instructions. -mplt -mno-plt When generating PIC code, do or don't allow the use of PLTs. Ignored for non-PIC. The default is -mplt. -mabi=ABI-string Specify integer and floating-point calling convention. ABI-string contains two parts: the size of integer types and the registers used for floating-point types. For example -march=rv64ifd -mabi=lp64d means that long and pointers are 64-bit (implicitly defining int to be 32-bit), and that floating-point values up to 64 bits wide are passed in F registers. Contrast this with -march=rv64ifd -mabi=lp64f, which still allows the compiler to generate code that uses the F and D extensions but only allows floating-point values up to 32 bits long to be passed in registers; or -march=rv64ifd -mabi=lp64, in which no floating-point arguments will be passed in registers. The default for this argument is system dependent, users who want a specific calling convention should specify one explicitly. The valid calling conventions are: ilp32, ilp32f, ilp32d, lp64, lp64f, and lp64d. Some calling conventions are impossible to implement on some ISAs: for example, -march=rv32if -mabi=ilp32d is invalid because the ABI requires 64-bit values be passed in F registers, but F registers are only 32 bits wide. There is also the ilp32e ABI that can only be used with the rv32e architecture. This ABI is not well specified at present, and is subject to change. -mfdiv -mno-fdiv Do or don't use hardware floating-point divide and square root instructions. This requires the F or D extensions for floating- point registers. The default is to use them if the specified architecture has these instructions. -mdiv -mno-div Do or don't use hardware instructions for integer division. This requires the M extension. The default is to use them if the specified architecture has these instructions. -misa-spec=ISA-spec-string Specify the version of the RISC-V Unprivileged (formerly User- Level) ISA specification to produce code conforming to. The possibilities for ISA-spec-string are: 2.2 Produce code conforming to version 2.2. 20190608 Produce code conforming to version 20190608. 20191213 Produce code conforming to version 20191213. The default is -misa-spec=20191213 unless GCC has been configured with --with-isa-spec= specifying a different default version. -march=ISA-string Generate code for given RISC-V ISA (e.g. rv64im). ISA strings must be lower-case. Examples include rv64i, rv32g, rv32e, and rv32imaf. When -march= is not specified, use the setting from -mcpu. If both -march and -mcpu= are not specified, the default for this argument is system dependent, users who want a specific architecture extensions should specify one explicitly. -mcpu=processor-string Use architecture of and optimize the output for the given processor, specified by particular CPU name. Permissible values for this option are: sifive-e20, sifive-e21, sifive-e24, sifive-e31, sifive-e34, sifive-e76, sifive-s21, sifive-s51, sifive-s54, sifive-s76, sifive-u54, and sifive-u74. -mtune=processor-string Optimize the output for the given processor, specified by microarchitecture or particular CPU name. Permissible values for this option are: rocket, sifive-3-series, sifive-5-series, sifive-7-series, thead-c906, size, and all valid options for -mcpu=. When -mtune= is not specified, use the setting from -mcpu, the default is rocket if both are not specified. The size choice is not intended for use by end-users. This is used when -Os is specified. It overrides the instruction cost info provided by -mtune=, but does not override the pipeline info. This helps reduce code size while still giving good performance. -mpreferred-stack-boundary=num Attempt to keep the stack boundary aligned to a 2 raised to num byte boundary. If -mpreferred-stack-boundary is not specified, the default is 4 (16 bytes or 128-bits). Warning: If you use this switch, then you must build all modules with the same value, including any libraries. This includes the system libraries and startup modules. -msmall-data-limit=n Put global and static data smaller than n bytes into a special section (on some targets). -msave-restore -mno-save-restore Do or don't use smaller but slower prologue and epilogue code that uses library function calls. The default is to use fast inline prologues and epilogues. -minline-atomics -mno-inline-atomics Do or don't use smaller but slower subword atomic emulation code that uses libatomic function calls. The default is to use fast inline subword atomics that do not require libatomic. -mshorten-memrefs -mno-shorten-memrefs Do or do not attempt to make more use of compressed load/store instructions by replacing a load/store of 'base register + large offset' with a new load/store of 'new base + small offset'. If the new base gets stored in a compressed register, then the new load/store can be compressed. Currently targets 32-bit integer load/stores only. -mstrict-align -mno-strict-align Do not or do generate unaligned memory accesses. The default is set depending on whether the processor we are optimizing for supports fast unaligned access or not. -mcmodel=medlow Generate code for the medium-low code model. The program and its statically defined symbols must lie within a single 2 GiB address range and must lie between absolute addresses -2 GiB and +2 GiB. Programs can be statically or dynamically linked. This is the default code model. -mcmodel=medany Generate code for the medium-any code model. The program and its statically defined symbols must be within any single 2 GiB address range. Programs can be statically or dynamically linked. The code generated by the medium-any code model is position- independent, but is not guaranteed to function correctly when linked into position-independent executables or libraries. -mexplicit-relocs -mno-exlicit-relocs Use or do not use assembler relocation operators when dealing with symbolic addresses. The alternative is to use assembler macros instead, which may limit optimization. -mrelax -mno-relax Take advantage of linker relaxations to reduce the number of instructions required to materialize symbol addresses. The default is to take advantage of linker relaxations. -mriscv-attribute -mno-riscv-attribute Emit (do not emit) RISC-V attribute to record extra information into ELF objects. This feature requires at least binutils 2.32. -mcsr-check -mno-csr-check Enables or disables the CSR checking. -malign-data=type Control how GCC aligns variables and constants of array, structure, or union types. Supported values for type are xlen which uses x register width as the alignment value, and natural which uses natural alignment. xlen is the default. -mbig-endian Generate big-endian code. This is the default when GCC is configured for a riscv64be-*-* or riscv32be-*-* target. -mlittle-endian Generate little-endian code. This is the default when GCC is configured for a riscv64-*-* or riscv32-*-* but not a riscv64be-*-* or riscv32be-*-* target. -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset Generate stack protection code using canary at guard. Supported locations are global for a global canary or tls for per-thread canary in the TLS block. With the latter choice the options -mstack-protector-guard-reg=reg and -mstack-protector-guard-offset=offset furthermore specify which register to use as base register for reading the canary, and from what offset from that base register. There is no default register or offset as this is entirely for use within the Linux kernel. RL78 Options -msim Links in additional target libraries to support operation within a simulator. -mmul=none -mmul=g10 -mmul=g13 -mmul=g14 -mmul=rl78 Specifies the type of hardware multiplication and division support to be used. The simplest is "none", which uses software for both multiplication and division. This is the default. The "g13" value is for the hardware multiply/divide peripheral found on the RL78/G13 (S2 core) targets. The "g14" value selects the use of the multiplication and division instructions supported by the RL78/G14 (S3 core) parts. The value "rl78" is an alias for "g14" and the value "mg10" is an alias for "none". In addition a C preprocessor macro is defined, based upon the setting of this option. Possible values are: "__RL78_MUL_NONE__", "__RL78_MUL_G13__" or "__RL78_MUL_G14__". -mcpu=g10 -mcpu=g13 -mcpu=g14 -mcpu=rl78 Specifies the RL78 core to target. The default is the G14 core, also known as an S3 core or just RL78. The G13 or S2 core does not have multiply or divide instructions, instead it uses a hardware peripheral for these operations. The G10 or S1 core does not have register banks, so it uses a different calling convention. If this option is set it also selects the type of hardware multiply support to use, unless this is overridden by an explicit -mmul=none option on the command line. Thus specifying -mcpu=g13 enables the use of the G13 hardware multiply peripheral and specifying -mcpu=g10 disables the use of hardware multiplications altogether. Note, although the RL78/G14 core is the default target, specifying -mcpu=g14 or -mcpu=rl78 on the command line does change the behavior of the toolchain since it also enables G14 hardware multiply support. If these options are not specified on the command line then software multiplication routines will be used even though the code targets the RL78 core. This is for backwards compatibility with older toolchains which did not have hardware multiply and divide support. In addition a C preprocessor macro is defined, based upon the setting of this option. Possible values are: "__RL78_G10__", "__RL78_G13__" or "__RL78_G14__". -mg10 -mg13 -mg14 -mrl78 These are aliases for the corresponding -mcpu= option. They are provided for backwards compatibility. -mallregs Allow the compiler to use all of the available registers. By default registers "r24..r31" are reserved for use in interrupt handlers. With this option enabled these registers can be used in ordinary functions as well. -m64bit-doubles -m32bit-doubles Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits (-m32bit-doubles) in size. The default is -m32bit-doubles. -msave-mduc-in-interrupts -mno-save-mduc-in-interrupts Specifies that interrupt handler functions should preserve the MDUC registers. This is only necessary if normal code might use the MDUC registers, for example because it performs multiplication and division operations. The default is to ignore the MDUC registers as this makes the interrupt handlers faster. The target option -mg13 needs to be passed for this to work as this feature is only available on the G13 target (S2 core). The MDUC registers will only be saved if the interrupt handler performs a multiplication or division operation or it calls another function. IBM RS/6000 and PowerPC Options These -m options are defined for the IBM RS/6000 and PowerPC: -mpowerpc-gpopt -mno-powerpc-gpopt -mpowerpc-gfxopt -mno-powerpc-gfxopt -mpowerpc64 -mno-powerpc64 -mmfcrf -mno-mfcrf -mpopcntb -mno-popcntb -mpopcntd -mno-popcntd -mfprnd -mno-fprnd -mcmpb -mno-cmpb -mhard-dfp -mno-hard-dfp You use these options to specify which instructions are available on the processor you are using. The default value of these options is determined when configuring GCC. Specifying the -mcpu=cpu_type overrides the specification of these options. We recommend you use the -mcpu=cpu_type option rather than the options listed above. Specifying -mpowerpc-gpopt allows GCC to use the optional PowerPC architecture instructions in the General Purpose group, including floating-point square root. Specifying -mpowerpc-gfxopt allows GCC to use the optional PowerPC architecture instructions in the Graphics group, including floating-point select. The -mmfcrf option allows GCC to generate the move from condition register field instruction implemented on the POWER4 processor and other processors that support the PowerPC V2.01 architecture. The -mpopcntb option allows GCC to generate the popcount and double- precision FP reciprocal estimate instruction implemented on the POWER5 processor and other processors that support the PowerPC V2.02 architecture. The -mpopcntd option allows GCC to generate the popcount instruction implemented on the POWER7 processor and other processors that support the PowerPC V2.06 architecture. The -mfprnd option allows GCC to generate the FP round to integer instructions implemented on the POWER5+ processor and other processors that support the PowerPC V2.03 architecture. The -mcmpb option allows GCC to generate the compare bytes instruction implemented on the POWER6 processor and other processors that support the PowerPC V2.05 architecture. The -mhard-dfp option allows GCC to generate the decimal floating-point instructions implemented on some POWER processors. The -mpowerpc64 option allows GCC to generate the additional 64-bit instructions that are found in the full PowerPC64 architecture and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to -mno-powerpc64. -mcpu=cpu_type Set architecture type, register usage, and instruction scheduling parameters for machine type cpu_type. Supported values for cpu_type are 401, 403, 405, 405fp, 440, 440fp, 464, 464fp, 476, 476fp, 505, 601, 602, 603, 603e, 604, 604e, 620, 630, 740, 7400, 7450, 750, 801, 821, 823, 860, 970, 8540, a2, e300c2, e300c3, e500mc, e500mc64, e5500, e6500, ec603e, G3, G4, G5, titan, power3, power4, power5, power5+, power6, power6x, power7, power8, power9, power10, powerpc, powerpc64, powerpc64le, rs64, and native. -mcpu=powerpc, -mcpu=powerpc64, and -mcpu=powerpc64le specify pure 32-bit PowerPC (either endian), 64-bit big endian PowerPC and 64-bit little endian PowerPC architecture machine types, with an appropriate, generic processor model assumed for scheduling purposes. Specifying native as cpu type detects and selects the architecture option that corresponds to the host processor of the system performing the compilation. -mcpu=native has no effect if GCC does not recognize the processor. The other options specify a specific processor. Code generated under those options runs best on that processor, and may not run at all on others. The -mcpu options automatically enable or disable the following options: -maltivec -mfprnd -mhard-float -mmfcrf -mmultiple -mpopcntb -mpopcntd -mpowerpc64 -mpowerpc-gpopt -mpowerpc-gfxopt -mmulhw -mdlmzb -mmfpgpr -mvsx -mcrypto -mhtm -mpower8-fusion -mpower8-vector -mquad-memory -mquad-memory-atomic -mfloat128 -mfloat128-hardware -mprefixed -mpcrel -mmma -mrop-protect The particular options set for any particular CPU varies between compiler versions, depending on what setting seems to produce optimal code for that CPU; it doesn't necessarily reflect the actual hardware's capabilities. If you wish to set an individual option to a particular value, you may specify it after the -mcpu option, like -mcpu=970 -mno-altivec. On AIX, the -maltivec and -mpowerpc64 options are not enabled or disabled by the -mcpu option at present because AIX does not have full support for these options. You may still enable or disable them individually if you're sure it'll work in your environment. -mtune=cpu_type Set the instruction scheduling parameters for machine type cpu_type, but do not set the architecture type or register usage, as -mcpu=cpu_type does. The same values for cpu_type are used for -mtune as for -mcpu. If both are specified, the code generated uses the architecture and registers set by -mcpu, but the scheduling parameters set by -mtune. -mcmodel=small Generate PowerPC64 code for the small model: The TOC is limited to 64k. -mcmodel=medium Generate PowerPC64 code for the medium model: The TOC and other static data may be up to a total of 4G in size. This is the default for 64-bit Linux. -mcmodel=large Generate PowerPC64 code for the large model: The TOC may be up to 4G in size. Other data and code is only limited by the 64-bit address space. -maltivec -mno-altivec Generate code that uses (does not use) AltiVec instructions, and also enable the use of built-in functions that allow more direct access to the AltiVec instruction set. You may also need to set -mabi=altivec to adjust the current ABI with AltiVec ABI enhancements. When -maltivec is used, the element order for AltiVec intrinsics such as "vec_splat", "vec_extract", and "vec_insert" match array element order corresponding to the endianness of the target. That is, element zero identifies the leftmost element in a vector register when targeting a big-endian platform, and identifies the rightmost element in a vector register when targeting a little- endian platform. -mvrsave -mno-vrsave Generate VRSAVE instructions when generating AltiVec code. -msecure-plt Generate code that allows ld and ld.so to build executables and shared libraries with non-executable ".plt" and ".got" sections. This is a PowerPC 32-bit SYSV ABI option. -mbss-plt Generate code that uses a BSS ".plt" section that ld.so fills in, and requires ".plt" and ".got" sections that are both writable and executable. This is a PowerPC 32-bit SYSV ABI option. -misel -mno-isel This switch enables or disables the generation of ISEL instructions. -mvsx -mno-vsx Generate code that uses (does not use) vector/scalar (VSX) instructions, and also enable the use of built-in functions that allow more direct access to the VSX instruction set. -mcrypto -mno-crypto Enable the use (disable) of the built-in functions that allow direct access to the cryptographic instructions that were added in version 2.07 of the PowerPC ISA. -mhtm -mno-htm Enable (disable) the use of the built-in functions that allow direct access to the Hardware Transactional Memory (HTM) instructions that were added in version 2.07 of the PowerPC ISA. -mpower8-fusion -mno-power8-fusion Generate code that keeps (does not keeps) some integer operations adjacent so that the instructions can be fused together on power8 and later processors. -mpower8-vector -mno-power8-vector Generate code that uses (does not use) the vector and scalar instructions that were added in version 2.07 of the PowerPC ISA. Also enable the use of built-in functions that allow more direct access to the vector instructions. -mquad-memory -mno-quad-memory Generate code that uses (does not use) the non-atomic quad word memory instructions. The -mquad-memory option requires use of 64-bit mode. -mquad-memory-atomic -mno-quad-memory-atomic Generate code that uses (does not use) the atomic quad word memory instructions. The -mquad-memory-atomic option requires use of 64-bit mode. -mfloat128 -mno-float128 Enable/disable the __float128 keyword for IEEE 128-bit floating point and use either software emulation for IEEE 128-bit floating point or hardware instructions. The VSX instruction set (-mvsx) must be enabled to use the IEEE 128-bit floating point support. The IEEE 128-bit floating point is only supported on Linux. The default for -mfloat128 is enabled on PowerPC Linux systems using the VSX instruction set, and disabled on other systems. If you use the ISA 3.0 instruction set (-mpower9-vector or -mcpu=power9) on a 64-bit system, the IEEE 128-bit floating point support will also enable the generation of ISA 3.0 IEEE 128-bit floating point instructions. Otherwise, if you do not specify to generate ISA 3.0 instructions or you are targeting a 32-bit big endian system, IEEE 128-bit floating point will be done with software emulation. -mfloat128-hardware -mno-float128-hardware Enable/disable using ISA 3.0 hardware instructions to support the __float128 data type. The default for -mfloat128-hardware is enabled on PowerPC Linux systems using the ISA 3.0 instruction set, and disabled on other systems. -m32 -m64 Generate code for 32-bit or 64-bit environments of Darwin and SVR4 targets (including GNU/Linux). The 32-bit environment sets int, long and pointer to 32 bits and generates code that runs on any PowerPC variant. The 64-bit environment sets int to 32 bits and long and pointer to 64 bits, and generates code for PowerPC64, as for -mpowerpc64. -mfull-toc -mno-fp-in-toc -mno-sum-in-toc -mminimal-toc Modify generation of the TOC (Table Of Contents), which is created for every executable file. The -mfull-toc option is selected by default. In that case, GCC allocates at least one TOC entry for each unique non-automatic variable reference in your program. GCC also places floating-point constants in the TOC. However, only 16,384 entries are available in the TOC. If you receive a linker error message that saying you have overflowed the available TOC space, you can reduce the amount of TOC space used with the -mno-fp-in-toc and -mno-sum-in-toc options. -mno-fp-in-toc prevents GCC from putting floating-point constants in the TOC and -mno-sum-in-toc forces GCC to generate code to calculate the sum of an address and a constant at run time instead of putting that sum into the TOC. You may specify one or both of these options. Each causes GCC to produce very slightly slower and larger code at the expense of conserving TOC space. If you still run out of space in the TOC even when you specify both of these options, specify -mminimal-toc instead. This option causes GCC to make only one TOC entry for every file. When you specify this option, GCC produces code that is slower and larger but which uses extremely little TOC space. You may wish to use this option only on files that contain less frequently-executed code. -maix64 -maix32 Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit "long" type, and the infrastructure needed to support them. Specifying -maix64 implies -mpowerpc64, while -maix32 disables the 64-bit ABI and implies -mno-powerpc64. GCC defaults to -maix32. -mxl-compat -mno-xl-compat Produce code that conforms more closely to IBM XL compiler semantics when using AIX-compatible ABI. Pass floating-point arguments to prototyped functions beyond the register save area (RSA) on the stack in addition to argument FPRs. Do not assume that most significant double in 128-bit long double value is properly rounded when comparing values and converting to double. Use XL symbol names for long double support routines. The AIX calling convention was extended but not initially documented to handle an obscure K&R C case of calling a function that takes the address of its arguments with fewer arguments than declared. IBM XL compilers access floating-point arguments that do not fit in the RSA from the stack when a subroutine is compiled without optimization. Because always storing floating-point arguments on the stack is inefficient and rarely needed, this option is not enabled by default and only is necessary when calling subroutines compiled by IBM XL compilers without optimization. -mpe Support IBM RS/6000 SP Parallel Environment (PE). Link an application written to use message passing with special startup code to enable the application to run. The system must have PE installed in the standard location (/usr/lpp/ppe.poe/), or the specs file must be overridden with the -specs= option to specify the appropriate directory location. The Parallel Environment does not support threads, so the -mpe option and the -pthread option are incompatible. -malign-natural -malign-power On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option -malign-natural overrides the ABI-defined alignment of larger types, such as floating-point doubles, on their natural size-based boundary. The option -malign-power instructs GCC to follow the ABI-specified alignment rules. GCC defaults to the standard alignment defined in the ABI. On 64-bit Darwin, natural alignment is the default, and -malign-power is not supported. -msoft-float -mhard-float Generate code that does not use (uses) the floating-point register set. Software floating-point emulation is provided if you use the -msoft-float option, and pass the option to GCC when linking. -mmultiple -mno-multiple Generate code that uses (does not use) the load multiple word instructions and the store multiple word instructions. These instructions are generated by default on POWER systems, and not generated on PowerPC systems. Do not use -mmultiple on little- endian PowerPC systems, since those instructions do not work when the processor is in little-endian mode. The exceptions are PPC740 and PPC750 which permit these instructions in little-endian mode. -mupdate -mno-update Generate code that uses (does not use) the load or store instructions that update the base register to the address of the calculated memory location. These instructions are generated by default. If you use -mno-update, there is a small window between the time that the stack pointer is updated and the address of the previous frame is stored, which means code that walks the stack frame across interrupts or signals may get corrupted data. -mavoid-indexed-addresses -mno-avoid-indexed-addresses Generate code that tries to avoid (not avoid) the use of indexed load or store instructions. These instructions can incur a performance penalty on Power6 processors in certain situations, such as when stepping through large arrays that cross a 16M boundary. This option is enabled by default when targeting Power6 and disabled otherwise. -mfused-madd -mno-fused-madd Generate code that uses (does not use) the floating-point multiply and accumulate instructions. These instructions are generated by default if hardware floating point is used. The machine-dependent -mfused-madd option is now mapped to the machine-independent -ffp-contract=fast option, and -mno-fused-madd is mapped to -ffp-contract=off. -mmulhw -mno-mulhw Generate code that uses (does not use) the half-word multiply and multiply-accumulate instructions on the IBM 405, 440, 464 and 476 processors. These instructions are generated by default when targeting those processors. -mdlmzb -mno-dlmzb Generate code that uses (does not use) the string-search dlmzb instruction on the IBM 405, 440, 464 and 476 processors. This instruction is generated by default when targeting those processors. -mno-bit-align -mbit-align On System V.4 and embedded PowerPC systems do not (do) force structures and unions that contain bit-fields to be aligned to the base type of the bit-field. For example, by default a structure containing nothing but 8 "unsigned" bit-fields of length 1 is aligned to a 4-byte boundary and has a size of 4 bytes. By using -mno-bit-align, the structure is aligned to a 1-byte boundary and is 1 byte in size. -mno-strict-align -mstrict-align On System V.4 and embedded PowerPC systems do not (do) assume that unaligned memory references are handled by the system. -mrelocatable -mno-relocatable Generate code that allows (does not allow) a static executable to be relocated to a different address at run time. A simple embedded PowerPC system loader should relocate the entire contents of ".got2" and 4-byte locations listed in the ".fixup" section, a table of 32-bit addresses generated by this option. For this to work, all objects linked together must be compiled with -mrelocatable or -mrelocatable-lib. -mrelocatable code aligns the stack to an 8-byte boundary. -mrelocatable-lib -mno-relocatable-lib Like -mrelocatable, -mrelocatable-lib generates a ".fixup" section to allow static executables to be relocated at run time, but -mrelocatable-lib does not use the smaller stack alignment of -mrelocatable. Objects compiled with -mrelocatable-lib may be linked with objects compiled with any combination of the -mrelocatable options. -mno-toc -mtoc On System V.4 and embedded PowerPC systems do not (do) assume that register 2 contains a pointer to a global area pointing to the addresses used in the program. -mlittle -mlittle-endian On System V.4 and embedded PowerPC systems compile code for the processor in little-endian mode. The -mlittle-endian option is the same as -mlittle. -mbig -mbig-endian On System V.4 and embedded PowerPC systems compile code for the processor in big-endian mode. The -mbig-endian option is the same as -mbig. -mdynamic-no-pic On Darwin and Mac OS X systems, compile code so that it is not relocatable, but that its external references are relocatable. The resulting code is suitable for applications, but not shared libraries. -msingle-pic-base Treat the register used for PIC addressing as read-only, rather than loading it in the prologue for each function. The runtime system is responsible for initializing this register with an appropriate value before execution begins. -mprioritize-restricted-insns=priority This option controls the priority that is assigned to dispatch-slot restricted instructions during the second scheduling pass. The argument priority takes the value 0, 1, or 2 to assign no, highest, or second-highest (respectively) priority to dispatch-slot restricted instructions. -msched-costly-dep=dependence_type This option controls which dependences are considered costly by the target during instruction scheduling. The argument dependence_type takes one of the following values: no No dependence is costly. all All dependences are costly. true_store_to_load A true dependence from store to load is costly. store_to_load Any dependence from store to load is costly. number Any dependence for which the latency is greater than or equal to number is costly. -minsert-sched-nops=scheme This option controls which NOP insertion scheme is used during the second scheduling pass. The argument scheme takes one of the following values: no Don't insert NOPs. pad Pad with NOPs any dispatch group that has vacant issue slots, according to the scheduler's grouping. regroup_exact Insert NOPs to force costly dependent insns into separate groups. Insert exactly as many NOPs as needed to force an insn to a new group, according to the estimated processor grouping. number Insert NOPs to force costly dependent insns into separate groups. Insert number NOPs to force an insn to a new group. -mcall-sysv On System V.4 and embedded PowerPC systems compile code using calling conventions that adhere to the March 1995 draft of the System V Application Binary Interface, PowerPC processor supplement. This is the default unless you configured GCC using powerpc-*-eabiaix. -mcall-sysv-eabi -mcall-eabi Specify both -mcall-sysv and -meabi options. -mcall-sysv-noeabi Specify both -mcall-sysv and -mno-eabi options. -mcall-aixdesc On System V.4 and embedded PowerPC systems compile code for the AIX operating system. -mcall-linux On System V.4 and embedded PowerPC systems compile code for the Linux-based GNU system. -mcall-freebsd On System V.4 and embedded PowerPC systems compile code for the FreeBSD operating system. -mcall-netbsd On System V.4 and embedded PowerPC systems compile code for the NetBSD operating system. -mcall-openbsd On System V.4 and embedded PowerPC systems compile code for the OpenBSD operating system. -mtraceback=traceback_type Select the type of traceback table. Valid values for traceback_type are full, part, and no. -maix-struct-return Return all structures in memory (as specified by the AIX ABI). -msvr4-struct-return Return structures smaller than 8 bytes in registers (as specified by the SVR4 ABI). -mabi=abi-type Extend the current ABI with a particular extension, or remove such extension. Valid values are: altivec, no-altivec, ibmlongdouble, ieeelongdouble, elfv1, elfv2, and for AIX: vec-extabi, vec-default. -mabi=ibmlongdouble Change the current ABI to use IBM extended-precision long double. This is not likely to work if your system defaults to using IEEE extended-precision long double. If you change the long double type from IEEE extended-precision, the compiler will issue a warning unless you use the -Wno-psabi option. Requires -mlong-double-128 to be enabled. -mabi=ieeelongdouble Change the current ABI to use IEEE extended-precision long double. This is not likely to work if your system defaults to using IBM extended-precision long double. If you change the long double type from IBM extended-precision, the compiler will issue a warning unless you use the -Wno-psabi option. Requires -mlong-double-128 to be enabled. -mabi=elfv1 Change the current ABI to use the ELFv1 ABI. This is the default ABI for big-endian PowerPC 64-bit Linux. Overriding the default ABI requires special system support and is likely to fail in spectacular ways. -mabi=elfv2 Change the current ABI to use the ELFv2 ABI. This is the default ABI for little-endian PowerPC 64-bit Linux. Overriding the default ABI requires special system support and is likely to fail in spectacular ways. -mgnu-attribute -mno-gnu-attribute Emit .gnu_attribute assembly directives to set tag/value pairs in a .gnu.attributes section that specify ABI variations in function parameters or return values. -mprototype -mno-prototype On System V.4 and embedded PowerPC systems assume that all calls to variable argument functions are properly prototyped. Otherwise, the compiler must insert an instruction before every non-prototyped call to set or clear bit 6 of the condition code register ("CR") to indicate whether floating-point values are passed in the floating- point registers in case the function takes variable arguments. With -mprototype, only calls to prototyped variable argument functions set or clear the bit. -msim On embedded PowerPC systems, assume that the startup module is called sim-crt0.o and that the standard C libraries are libsim.a and libc.a. This is the default for powerpc-*-eabisim configurations. -mmvme On embedded PowerPC systems, assume that the startup module is called crt0.o and the standard C libraries are libmvme.a and libc.a. -mads On embedded PowerPC systems, assume that the startup module is called crt0.o and the standard C libraries are libads.a and libc.a. -myellowknife On embedded PowerPC systems, assume that the startup module is called crt0.o and the standard C libraries are libyk.a and libc.a. -mvxworks On System V.4 and embedded PowerPC systems, specify that you are compiling for a VxWorks system. -memb On embedded PowerPC systems, set the "PPC_EMB" bit in the ELF flags header to indicate that eabi extended relocations are used. -meabi -mno-eabi On System V.4 and embedded PowerPC systems do (do not) adhere to the Embedded Applications Binary Interface (EABI), which is a set of modifications to the System V.4 specifications. Selecting -meabi means that the stack is aligned to an 8-byte boundary, a function "__eabi" is called from "main" to set up the EABI environment, and the -msdata option can use both "r2" and "r13" to point to two separate small data areas. Selecting -mno-eabi means that the stack is aligned to a 16-byte boundary, no EABI initialization function is called from "main", and the -msdata option only uses "r13" to point to a single small data area. The -meabi option is on by default if you configured GCC using one of the powerpc*-*-eabi* options. -msdata=eabi On System V.4 and embedded PowerPC systems, put small initialized "const" global and static data in the ".sdata2" section, which is pointed to by register "r2". Put small initialized non-"const" global and static data in the ".sdata" section, which is pointed to by register "r13". Put small uninitialized global and static data in the ".sbss" section, which is adjacent to the ".sdata" section. The -msdata=eabi option is incompatible with the -mrelocatable option. The -msdata=eabi option also sets the -memb option. -msdata=sysv On System V.4 and embedded PowerPC systems, put small global and static data in the ".sdata" section, which is pointed to by register "r13". Put small uninitialized global and static data in the ".sbss" section, which is adjacent to the ".sdata" section. The -msdata=sysv option is incompatible with the -mrelocatable option. -msdata=default -msdata On System V.4 and embedded PowerPC systems, if -meabi is used, compile code the same as -msdata=eabi, otherwise compile code the same as -msdata=sysv. -msdata=data On System V.4 and embedded PowerPC systems, put small global data in the ".sdata" section. Put small uninitialized global data in the ".sbss" section. Do not use register "r13" to address small data however. This is the default behavior unless other -msdata options are used. -msdata=none -mno-sdata On embedded PowerPC systems, put all initialized global and static data in the ".data" section, and all uninitialized data in the ".bss" section. -mreadonly-in-sdata Put read-only objects in the ".sdata" section as well. This is the default. -mblock-move-inline-limit=num Inline all block moves (such as calls to "memcpy" or structure copies) less than or equal to num bytes. The minimum value for num is 32 bytes on 32-bit targets and 64 bytes on 64-bit targets. The default value is target-specific. -mblock-compare-inline-limit=num Generate non-looping inline code for all block compares (such as calls to "memcmp" or structure compares) less than or equal to num bytes. If num is 0, all inline expansion (non-loop and loop) of block compare is disabled. The default value is target-specific. -mblock-compare-inline-loop-limit=num Generate an inline expansion using loop code for all block compares that are less than or equal to num bytes, but greater than the limit for non-loop inline block compare expansion. If the block length is not constant, at most num bytes will be compared before "memcmp" is called to compare the remainder of the block. The default value is target-specific. -mstring-compare-inline-limit=num Compare at most num string bytes with inline code. If the difference or end of string is not found at the end of the inline compare a call to "strcmp" or "strncmp" will take care of the rest of the comparison. The default is 64 bytes. -G num On embedded PowerPC systems, put global and static items less than or equal to num bytes into the small data or BSS sections instead of the normal data or BSS section. By default, num is 8. The -G num switch is also passed to the linker. All modules should be compiled with the same -G num value. -mregnames -mno-regnames On System V.4 and embedded PowerPC systems do (do not) emit register names in the assembly language output using symbolic forms. -mlongcall -mno-longcall By default assume that all calls are far away so that a longer and more expensive calling sequence is required. This is required for calls farther than 32 megabytes (33,554,432 bytes) from the current location. A short call is generated if the compiler knows the call cannot be that far away. This setting can be overridden by the "shortcall" function attribute, or by "#pragma longcall(0)". Some linkers are capable of detecting out-of-range calls and generating glue code on the fly. On these systems, long calls are unnecessary and generate slower code. As of this writing, the AIX linker can do this, as can the GNU linker for PowerPC/64. It is planned to add this feature to the GNU linker for 32-bit PowerPC systems as well. On PowerPC64 ELFv2 and 32-bit PowerPC systems with newer GNU linkers, GCC can generate long calls using an inline PLT call sequence (see -mpltseq). PowerPC with -mbss-plt and PowerPC64 ELFv1 (big-endian) do not support inline PLT calls. On Darwin/PPC systems, "#pragma longcall" generates "jbsr callee, L42", plus a branch island (glue code). The two target addresses represent the callee and the branch island. The Darwin/PPC linker prefers the first address and generates a "bl callee" if the PPC "bl" instruction reaches the callee directly; otherwise, the linker generates "bl L42" to call the branch island. The branch island is appended to the body of the calling function; it computes the full 32-bit address of the callee and jumps to it. On Mach-O (Darwin) systems, this option directs the compiler emit to the glue for every direct call, and the Darwin linker decides whether to use or discard it. In the future, GCC may ignore all longcall specifications when the linker is known to generate glue. -mpltseq -mno-pltseq Implement (do not implement) -fno-plt and long calls using an inline PLT call sequence that supports lazy linking and long calls to functions in dlopen'd shared libraries. Inline PLT calls are only supported on PowerPC64 ELFv2 and 32-bit PowerPC systems with newer GNU linkers, and are enabled by default if the support is detected when configuring GCC, and, in the case of 32-bit PowerPC, if GCC is configured with --enable-secureplt. -mpltseq code and -mbss-plt 32-bit PowerPC relocatable objects may not be linked together. -mtls-markers -mno-tls-markers Mark (do not mark) calls to "__tls_get_addr" with a relocation specifying the function argument. The relocation allows the linker to reliably associate function call with argument setup instructions for TLS optimization, which in turn allows GCC to better schedule the sequence. -mrecip -mno-recip This option enables use of the reciprocal estimate and reciprocal square root estimate instructions with additional Newton-Raphson steps to increase precision instead of doing a divide or square root and divide for floating-point arguments. You should use the -ffast-math option when using -mrecip (or at least -funsafe-math-optimizations, -ffinite-math-only, -freciprocal-math and -fno-trapping-math). Note that while the throughput of the sequence is generally higher than the throughput of the non- reciprocal instruction, the precision of the sequence can be decreased by up to 2 ulp (i.e. the inverse of 1.0 equals 0.99999994) for reciprocal square roots. -mrecip=opt This option controls which reciprocal estimate instructions may be used. opt is a comma-separated list of options, which may be preceded by a "!" to invert the option: all Enable all estimate instructions. default Enable the default instructions, equivalent to -mrecip. none Disable all estimate instructions, equivalent to -mno-recip. div Enable the reciprocal approximation instructions for both single and double precision. divf Enable the single-precision reciprocal approximation instructions. divd Enable the double-precision reciprocal approximation instructions. rsqrt Enable the reciprocal square root approximation instructions for both single and double precision. rsqrtf Enable the single-precision reciprocal square root approximation instructions. rsqrtd Enable the double-precision reciprocal square root approximation instructions. So, for example, -mrecip=all,!rsqrtd enables all of the reciprocal estimate instructions, except for the "FRSQRTE", "XSRSQRTEDP", and "XVRSQRTEDP" instructions which handle the double-precision reciprocal square root calculations. -mrecip-precision -mno-recip-precision Assume (do not assume) that the reciprocal estimate instructions provide higher-precision estimates than is mandated by the PowerPC ABI. Selecting -mcpu=power6, -mcpu=power7 or -mcpu=power8 automatically selects -mrecip-precision. The double-precision square root estimate instructions are not generated by default on low-precision machines, since they do not provide an estimate that converges after three steps. -mveclibabi=type Specifies the ABI type to use for vectorizing intrinsics using an external library. The only type supported at present is mass, which specifies to use IBM's Mathematical Acceleration Subsystem (MASS) libraries for vectorizing intrinsics using external libraries. GCC currently emits calls to "acosd2", "acosf4", "acoshd2", "acoshf4", "asind2", "asinf4", "asinhd2", "asinhf4", "atan2d2", "atan2f4", "atand2", "atanf4", "atanhd2", "atanhf4", "cbrtd2", "cbrtf4", "cosd2", "cosf4", "coshd2", "coshf4", "erfcd2", "erfcf4", "erfd2", "erff4", "exp2d2", "exp2f4", "expd2", "expf4", "expm1d2", "expm1f4", "hypotd2", "hypotf4", "lgammad2", "lgammaf4", "log10d2", "log10f4", "log1pd2", "log1pf4", "log2d2", "log2f4", "logd2", "logf4", "powd2", "powf4", "sind2", "sinf4", "sinhd2", "sinhf4", "sqrtd2", "sqrtf4", "tand2", "tanf4", "tanhd2", and "tanhf4" when generating code for power7. Both -ftree-vectorize and -funsafe-math-optimizations must also be enabled. The MASS libraries must be specified at link time. -mfriz -mno-friz Generate (do not generate) the "friz" instruction when the -funsafe-math-optimizations option is used to optimize rounding of floating-point values to 64-bit integer and back to floating point. The "friz" instruction does not return the same value if the floating-point number is too large to fit in an integer. -mpointers-to-nested-functions -mno-pointers-to-nested-functions Generate (do not generate) code to load up the static chain register ("r11") when calling through a pointer on AIX and 64-bit Linux systems where a function pointer points to a 3-word descriptor giving the function address, TOC value to be loaded in register "r2", and static chain value to be loaded in register "r11". The -mpointers-to-nested-functions is on by default. You cannot call through pointers to nested functions or pointers to functions compiled in other languages that use the static chain if you use -mno-pointers-to-nested-functions. -msave-toc-indirect -mno-save-toc-indirect Generate (do not generate) code to save the TOC value in the reserved stack location in the function prologue if the function calls through a pointer on AIX and 64-bit Linux systems. If the TOC value is not saved in the prologue, it is saved just before the call through the pointer. The -mno-save-toc-indirect option is the default. -mcompat-align-parm -mno-compat-align-parm Generate (do not generate) code to pass structure parameters with a maximum alignment of 64 bits, for compatibility with older versions of GCC. Older versions of GCC (prior to 4.9.0) incorrectly did not align a structure parameter on a 128-bit boundary when that structure contained a member requiring 128-bit alignment. This is corrected in more recent versions of GCC. This option may be used to generate code that is compatible with functions compiled with older versions of GCC. The -mno-compat-align-parm option is the default. -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset -mstack-protector-guard-symbol=symbol Generate stack protection code using canary at guard. Supported locations are global for global canary or tls for per-thread canary in the TLS block (the default with GNU libc version 2.4 or later). With the latter choice the options -mstack-protector-guard-reg=reg and -mstack-protector-guard-offset=offset furthermore specify which register to use as base register for reading the canary, and from what offset from that base register. The default for those is as specified in the relevant ABI. -mstack-protector-guard-symbol=symbol overrides the offset with a symbol reference to a canary in the TLS block. -mpcrel -mno-pcrel Generate (do not generate) pc-relative addressing. The -mpcrel option requires that the medium code model (-mcmodel=medium) and prefixed addressing (-mprefixed) options are enabled. -mprefixed -mno-prefixed Generate (do not generate) addressing modes using prefixed load and store instructions. The -mprefixed option requires that the option -mcpu=power10 (or later) is enabled. -mmma -mno-mma Generate (do not generate) the MMA instructions. The -mma option requires that the option -mcpu=power10 (or later) is enabled. -mrop-protect -mno-rop-protect Generate (do not generate) ROP protection instructions when the target processor supports them. Currently this option disables the shrink-wrap optimization (-fshrink-wrap). -mprivileged -mno-privileged Generate (do not generate) code that will run in privileged state. -mblock-ops-unaligned-vsx -mno-block-ops-unaligned-vsx Generate (do not generate) unaligned vsx loads and stores for inline expansion of "memcpy" and "memmove". --param rs6000-vect-unroll-limit= The vectorizer will check with target information to determine whether it would be beneficial to unroll the main vectorized loop and by how much. This parameter sets the upper bound of how much the vectorizer will unroll the main loop. The default value is four. RX Options These command-line options are defined for RX targets: -m64bit-doubles -m32bit-doubles Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits (-m32bit-doubles) in size. The default is -m32bit-doubles. Note RX floating-point hardware only works on 32-bit values, which is why the default is -m32bit-doubles. -fpu -nofpu Enables (-fpu) or disables (-nofpu) the use of RX floating-point hardware. The default is enabled for the RX600 series and disabled for the RX200 series. Floating-point instructions are only generated for 32-bit floating- point values, however, so the FPU hardware is not used for doubles if the -m64bit-doubles option is used. Note If the -fpu option is enabled then -funsafe-math-optimizations is also enabled automatically. This is because the RX FPU instructions are themselves unsafe. -mcpu=name Selects the type of RX CPU to be targeted. Currently three types are supported, the generic RX600 and RX200 series hardware and the specific RX610 CPU. The default is RX600. The only difference between RX600 and RX610 is that the RX610 does not support the "MVTIPL" instruction. The RX200 series does not have a hardware floating-point unit and so -nofpu is enabled by default when this type is selected. -mbig-endian-data -mlittle-endian-data Store data (but not code) in the big-endian format. The default is -mlittle-endian-data, i.e. to store data in the little-endian format. -msmall-data-limit=N Specifies the maximum size in bytes of global and static variables which can be placed into the small data area. Using the small data area can lead to smaller and faster code, but the size of area is limited and it is up to the programmer to ensure that the area does not overflow. Also when the small data area is used one of the RX's registers (usually "r13") is reserved for use pointing to this area, so it is no longer available for use by the compiler. This could result in slower and/or larger code if variables are pushed onto the stack instead of being held in this register. Note, common variables (variables that have not been initialized) and constants are not placed into the small data area as they are assigned to other sections in the output executable. The default value is zero, which disables this feature. Note, this feature is not enabled by default with higher optimization levels (-O2 etc) because of the potentially detrimental effects of reserving a register. It is up to the programmer to experiment and discover whether this feature is of benefit to their program. See the description of the -mpid option for a description of how the actual register to hold the small data area pointer is chosen. -msim -mno-sim Use the simulator runtime. The default is to use the libgloss board-specific runtime. -mas100-syntax -mno-as100-syntax When generating assembler output use a syntax that is compatible with Renesas's AS100 assembler. This syntax can also be handled by the GAS assembler, but it has some restrictions so it is not generated by default. -mmax-constant-size=N Specifies the maximum size, in bytes, of a constant that can be used as an operand in a RX instruction. Although the RX instruction set does allow constants of up to 4 bytes in length to be used in instructions, a longer value equates to a longer instruction. Thus in some circumstances it can be beneficial to restrict the size of constants that are used in instructions. Constants that are too big are instead placed into a constant pool and referenced via register indirection. The value N can be between 0 and 4. A value of 0 (the default) or 4 means that constants of any size are allowed. -mrelax Enable linker relaxation. Linker relaxation is a process whereby the linker attempts to reduce the size of a program by finding shorter versions of various instructions. Disabled by default. -mint-register=N Specify the number of registers to reserve for fast interrupt handler functions. The value N can be between 0 and 4. A value of 1 means that register "r13" is reserved for the exclusive use of fast interrupt handlers. A value of 2 reserves "r13" and "r12". A value of 3 reserves "r13", "r12" and "r11", and a value of 4 reserves "r13" through "r10". A value of 0, the default, does not reserve any registers. -msave-acc-in-interrupts Specifies that interrupt handler functions should preserve the accumulator register. This is only necessary if normal code might use the accumulator register, for example because it performs 64-bit multiplications. The default is to ignore the accumulator as this makes the interrupt handlers faster. -mpid -mno-pid Enables the generation of position independent data. When enabled any access to constant data is done via an offset from a base address held in a register. This allows the location of constant data to be determined at run time without requiring the executable to be relocated, which is a benefit to embedded applications with tight memory constraints. Data that can be modified is not affected by this option. Note, using this feature reserves a register, usually "r13", for the constant data base address. This can result in slower and/or larger code, especially in complicated functions. The actual register chosen to hold the constant data base address depends upon whether the -msmall-data-limit and/or the -mint-register command-line options are enabled. Starting with register "r13" and proceeding downwards, registers are allocated first to satisfy the requirements of -mint-register, then -mpid and finally -msmall-data-limit. Thus it is possible for the small data area register to be "r8" if both -mint-register=4 and -mpid are specified on the command line. By default this feature is not enabled. The default can be restored via the -mno-pid command-line option. -mno-warn-multiple-fast-interrupts -mwarn-multiple-fast-interrupts Prevents GCC from issuing a warning message if it finds more than one fast interrupt handler when it is compiling a file. The default is to issue a warning for each extra fast interrupt handler found, as the RX only supports one such interrupt. -mallow-string-insns -mno-allow-string-insns Enables or disables the use of the string manipulation instructions "SMOVF", "SCMPU", "SMOVB", "SMOVU", "SUNTIL" "SWHILE" and also the "RMPA" instruction. These instructions may prefetch data, which is not safe to do if accessing an I/O register. (See section 12.2.7 of the RX62N Group User's Manual for more information). The default is to allow these instructions, but it is not possible for GCC to reliably detect all circumstances where a string instruction might be used to access an I/O register, so their use cannot be disabled automatically. Instead it is reliant upon the programmer to use the -mno-allow-string-insns option if their program accesses I/O space. When the instructions are enabled GCC defines the C preprocessor symbol "__RX_ALLOW_STRING_INSNS__", otherwise it defines the symbol "__RX_DISALLOW_STRING_INSNS__". -mjsr -mno-jsr Use only (or not only) "JSR" instructions to access functions. This option can be used when code size exceeds the range of "BSR" instructions. Note that -mno-jsr does not mean to not use "JSR" but instead means that any type of branch may be used. Note: The generic GCC command-line option -ffixed-reg has special significance to the RX port when used with the "interrupt" function attribute. This attribute indicates a function intended to process fast interrupts. GCC ensures that it only uses the registers "r10", "r11", "r12" and/or "r13" and only provided that the normal use of the corresponding registers have been restricted via the -ffixed-reg or -mint-register command-line options. S/390 and zSeries Options These are the -m options defined for the S/390 and zSeries architecture. -mhard-float -msoft-float Use (do not use) the hardware floating-point instructions and registers for floating-point operations. When -msoft-float is specified, functions in libgcc.a are used to perform floating-point operations. When -mhard-float is specified, the compiler generates IEEE floating-point instructions. This is the default. -mhard-dfp -mno-hard-dfp Use (do not use) the hardware decimal-floating-point instructions for decimal-floating-point operations. When -mno-hard-dfp is specified, functions in libgcc.a are used to perform decimal- floating-point operations. When -mhard-dfp is specified, the compiler generates decimal-floating-point hardware instructions. This is the default for -march=z9-ec or higher. -mlong-double-64 -mlong-double-128 These switches control the size of "long double" type. A size of 64 bits makes the "long double" type equivalent to the "double" type. This is the default. -mbackchain -mno-backchain Store (do not store) the address of the caller's frame as backchain pointer into the callee's stack frame. A backchain may be needed to allow debugging using tools that do not understand DWARF call frame information. When -mno-packed-stack is in effect, the backchain pointer is stored at the bottom of the stack frame; when -mpacked-stack is in effect, the backchain is placed into the topmost word of the 96/160 byte register save area. In general, code compiled with -mbackchain is call-compatible with code compiled with -mno-backchain; however, use of the backchain for debugging purposes usually requires that the whole binary is built with -mbackchain. Note that the combination of -mbackchain, -mpacked-stack and -mhard-float is not supported. In order to build a linux kernel use -msoft-float. The default is to not maintain the backchain. -mpacked-stack -mno-packed-stack Use (do not use) the packed stack layout. When -mno-packed-stack is specified, the compiler uses the all fields of the 96/160 byte register save area only for their default purpose; unused fields still take up stack space. When -mpacked-stack is specified, register save slots are densely packed at the top of the register save area; unused space is reused for other purposes, allowing for more efficient use of the available stack space. However, when -mbackchain is also in effect, the topmost word of the save area is always used to store the backchain, and the return address register is always saved two words below the backchain. As long as the stack frame backchain is not used, code generated with -mpacked-stack is call-compatible with code generated with -mno-packed-stack. Note that some non-FSF releases of GCC 2.95 for S/390 or zSeries generated code that uses the stack frame backchain at run time, not just for debugging purposes. Such code is not call-compatible with code compiled with -mpacked-stack. Also, note that the combination of -mbackchain, -mpacked-stack and -mhard-float is not supported. In order to build a linux kernel use -msoft-float. The default is to not use the packed stack layout. -msmall-exec -mno-small-exec Generate (or do not generate) code using the "bras" instruction to do subroutine calls. This only works reliably if the total executable size does not exceed 64k. The default is to use the "basr" instruction instead, which does not have this limitation. -m64 -m31 When -m31 is specified, generate code compliant to the GNU/Linux for S/390 ABI. When -m64 is specified, generate code compliant to the GNU/Linux for zSeries ABI. This allows GCC in particular to generate 64-bit instructions. For the s390 targets, the default is -m31, while the s390x targets default to -m64. -mzarch -mesa When -mzarch is specified, generate code using the instructions available on z/Architecture. When -mesa is specified, generate code using the instructions available on ESA/390. Note that -mesa is not possible with -m64. When generating code compliant to the GNU/Linux for S/390 ABI, the default is -mesa. When generating code compliant to the GNU/Linux for zSeries ABI, the default is -mzarch. -mhtm -mno-htm The -mhtm option enables a set of builtins making use of instructions available with the transactional execution facility introduced with the IBM zEnterprise EC12 machine generation S/390 System z Built-in Functions. -mhtm is enabled by default when using -march=zEC12. -mvx -mno-vx When -mvx is specified, generate code using the instructions available with the vector extension facility introduced with the IBM z13 machine generation. This option changes the ABI for some vector type values with regard to alignment and calling conventions. In case vector type values are being used in an ABI- relevant context a GAS .gnu_attribute command will be added to mark the resulting binary with the ABI used. -mvx is enabled by default when using -march=z13. -mzvector -mno-zvector The -mzvector option enables vector language extensions and builtins using instructions available with the vector extension facility introduced with the IBM z13 machine generation. This option adds support for vector to be used as a keyword to define vector type variables and arguments. vector is only available when GNU extensions are enabled. It will not be expanded when requesting strict standard compliance e.g. with -std=c99. In addition to the GCC low-level builtins -mzvector enables a set of builtins added for compatibility with AltiVec-style implementations like Power and Cell. In order to make use of these builtins the header file vecintrin.h needs to be included. -mzvector is disabled by default. -mmvcle -mno-mvcle Generate (or do not generate) code using the "mvcle" instruction to perform block moves. When -mno-mvcle is specified, use a "mvc" loop instead. This is the default unless optimizing for size. -mdebug -mno-debug Print (or do not print) additional debug information when compiling. The default is to not print debug information. -march=cpu-type Generate code that runs on cpu-type, which is the name of a system representing a certain processor type. Possible values for cpu- type are z900/arch5, z990/arch6, z9-109, z9-ec/arch7, z10/arch8, z196/arch9, zEC12, z13/arch11, z14/arch12, z15/arch13, z16/arch14, and native. The default is -march=z900. Specifying native as cpu type can be used to select the best architecture option for the host processor. -march=native has no effect if GCC does not recognize the processor. -mtune=cpu-type Tune to cpu-type everything applicable about the generated code, except for the ABI and the set of available instructions. The list of cpu-type values is the same as for -march. The default is the value used for -march. -mtpf-trace -mno-tpf-trace Generate code that adds (does not add) in TPF OS specific branches to trace routines in the operating system. This option is off by default, even when compiling for the TPF OS. -mtpf-trace-skip -mno-tpf-trace-skip Generate code that changes (does not change) the default branch targets enabled by -mtpf-trace to point to specialized trace routines providing the ability of selectively skipping function trace entries for the TPF OS. This option is off by default, even when compiling for the TPF OS and specifying -mtpf-trace. -mfused-madd -mno-fused-madd Generate code that uses (does not use) the floating-point multiply and accumulate instructions. These instructions are generated by default if hardware floating point is used. -mwarn-framesize=framesize Emit a warning if the current function exceeds the given frame size. Because this is a compile-time check it doesn't need to be a real problem when the program runs. It is intended to identify functions that most probably cause a stack overflow. It is useful to be used in an environment with limited stack size e.g. the linux kernel. -mwarn-dynamicstack Emit a warning if the function calls "alloca" or uses dynamically- sized arrays. This is generally a bad idea with a limited stack size. -mstack-guard=stack-guard -mstack-size=stack-size If these options are provided the S/390 back end emits additional instructions in the function prologue that trigger a trap if the stack size is stack-guard bytes above the stack-size (remember that the stack on S/390 grows downward). If the stack-guard option is omitted the smallest power of 2 larger than the frame size of the compiled function is chosen. These options are intended to be used to help debugging stack overflow problems. The additionally emitted code causes only little overhead and hence can also be used in production-like systems without greater performance degradation. The given values have to be exact powers of 2 and stack-size has to be greater than stack-guard without exceeding 64k. In order to be efficient the extra code makes the assumption that the stack starts at an address aligned to the value given by stack-size. The stack- guard option can only be used in conjunction with stack-size. -mhotpatch=pre-halfwords,post-halfwords If the hotpatch option is enabled, a "hot-patching" function prologue is generated for all functions in the compilation unit. The funtion label is prepended with the given number of two-byte NOP instructions (pre-halfwords, maximum 1000000). After the label, 2 * post-halfwords bytes are appended, using the largest NOP like instructions the architecture allows (maximum 1000000). If both arguments are zero, hotpatching is disabled. This option can be overridden for individual functions with the "hotpatch" attribute. SH Options These -m options are defined for the SH implementations: -m1 Generate code for the SH1. -m2 Generate code for the SH2. -m2e Generate code for the SH2e. -m2a-nofpu Generate code for the SH2a without FPU, or for a SH2a-FPU in such a way that the floating-point unit is not used. -m2a-single-only Generate code for the SH2a-FPU, in such a way that no double- precision floating-point operations are used. -m2a-single Generate code for the SH2a-FPU assuming the floating-point unit is in single-precision mode by default. -m2a Generate code for the SH2a-FPU assuming the floating-point unit is in double-precision mode by default. -m3 Generate code for the SH3. -m3e Generate code for the SH3e. -m4-nofpu Generate code for the SH4 without a floating-point unit. -m4-single-only Generate code for the SH4 with a floating-point unit that only supports single-precision arithmetic. -m4-single Generate code for the SH4 assuming the floating-point unit is in single-precision mode by default. -m4 Generate code for the SH4. -m4-100 Generate code for SH4-100. -m4-100-nofpu Generate code for SH4-100 in such a way that the floating-point unit is not used. -m4-100-single Generate code for SH4-100 assuming the floating-point unit is in single-precision mode by default. -m4-100-single-only Generate code for SH4-100 in such a way that no double-precision floating-point operations are used. -m4-200 Generate code for SH4-200. -m4-200-nofpu Generate code for SH4-200 without in such a way that the floating- point unit is not used. -m4-200-single Generate code for SH4-200 assuming the floating-point unit is in single-precision mode by default. -m4-200-single-only Generate code for SH4-200 in such a way that no double-precision floating-point operations are used. -m4-300 Generate code for SH4-300. -m4-300-nofpu Generate code for SH4-300 without in such a way that the floating- point unit is not used. -m4-300-single Generate code for SH4-300 in such a way that no double-precision floating-point operations are used. -m4-300-single-only Generate code for SH4-300 in such a way that no double-precision floating-point operations are used. -m4-340 Generate code for SH4-340 (no MMU, no FPU). -m4-500 Generate code for SH4-500 (no FPU). Passes -isa=sh4-nofpu to the assembler. -m4a-nofpu Generate code for the SH4al-dsp, or for a SH4a in such a way that the floating-point unit is not used. -m4a-single-only Generate code for the SH4a, in such a way that no double-precision floating-point operations are used. -m4a-single Generate code for the SH4a assuming the floating-point unit is in single-precision mode by default. -m4a Generate code for the SH4a. -m4al Same as -m4a-nofpu, except that it implicitly passes -dsp to the assembler. GCC doesn't generate any DSP instructions at the moment. -mb Compile code for the processor in big-endian mode. -ml Compile code for the processor in little-endian mode. -mdalign Align doubles at 64-bit boundaries. Note that this changes the calling conventions, and thus some functions from the standard C library do not work unless you recompile it first with -mdalign. -mrelax Shorten some address references at link time, when possible; uses the linker option -relax. -mbigtable Use 32-bit offsets in "switch" tables. The default is to use 16-bit offsets. -mbitops Enable the use of bit manipulation instructions on SH2A. -mfmovd Enable the use of the instruction "fmovd". Check -mdalign for alignment constraints. -mrenesas Comply with the calling conventions defined by Renesas. -mno-renesas Comply with the calling conventions defined for GCC before the Renesas conventions were available. This option is the default for all targets of the SH toolchain. -mnomacsave Mark the "MAC" register as call-clobbered, even if -mrenesas is given. -mieee -mno-ieee Control the IEEE compliance of floating-point comparisons, which affects the handling of cases where the result of a comparison is unordered. By default -mieee is implicitly enabled. If -ffinite-math-only is enabled -mno-ieee is implicitly set, which results in faster floating-point greater-equal and less-equal comparisons. The implicit settings can be overridden by specifying either -mieee or -mno-ieee. -minline-ic_invalidate Inline code to invalidate instruction cache entries after setting up nested function trampolines. This option has no effect if -musermode is in effect and the selected code generation option (e.g. -m4) does not allow the use of the "icbi" instruction. If the selected code generation option does not allow the use of the "icbi" instruction, and -musermode is not in effect, the inlined code manipulates the instruction cache address array directly with an associative write. This not only requires privileged mode at run time, but it also fails if the cache line had been mapped via the TLB and has become unmapped. -misize Dump instruction size and location in the assembly code. -mpadstruct This option is deprecated. It pads structures to multiple of 4 bytes, which is incompatible with the SH ABI. -matomic-model=model Sets the model of atomic operations and additional parameters as a comma separated list. For details on the atomic built-in functions see __atomic Builtins. The following models and parameters are supported: none Disable compiler generated atomic sequences and emit library calls for atomic operations. This is the default if the target is not "sh*-*-linux*". soft-gusa Generate GNU/Linux compatible gUSA software atomic sequences for the atomic built-in functions. The generated atomic sequences require additional support from the interrupt/exception handling code of the system and are only suitable for SH3* and SH4* single-core systems. This option is enabled by default when the target is "sh*-*-linux*" and SH3* or SH4*. When the target is SH4A, this option also partially utilizes the hardware atomic instructions "movli.l" and "movco.l" to create more efficient code, unless strict is specified. soft-tcb Generate software atomic sequences that use a variable in the thread control block. This is a variation of the gUSA sequences which can also be used on SH1* and SH2* targets. The generated atomic sequences require additional support from the interrupt/exception handling code of the system and are only suitable for single-core systems. When using this model, the gbr-offset= parameter has to be specified as well. soft-imask Generate software atomic sequences that temporarily disable interrupts by setting "SR.IMASK = 1111". This model works only when the program runs in privileged mode and is only suitable for single-core systems. Additional support from the interrupt/exception handling code of the system is not required. This model is enabled by default when the target is "sh*-*-linux*" and SH1* or SH2*. hard-llcs Generate hardware atomic sequences using the "movli.l" and "movco.l" instructions only. This is only available on SH4A and is suitable for multi-core systems. Since the hardware instructions support only 32 bit atomic variables access to 8 or 16 bit variables is emulated with 32 bit accesses. Code compiled with this option is also compatible with other software atomic model interrupt/exception handling systems if executed on an SH4A system. Additional support from the interrupt/exception handling code of the system is not required for this model. gbr-offset= This parameter specifies the offset in bytes of the variable in the thread control block structure that should be used by the generated atomic sequences when the soft-tcb model has been selected. For other models this parameter is ignored. The specified value must be an integer multiple of four and in the range 0-1020. strict This parameter prevents mixed usage of multiple atomic models, even if they are compatible, and makes the compiler generate atomic sequences of the specified model only. -mtas Generate the "tas.b" opcode for "__atomic_test_and_set". Notice that depending on the particular hardware and software configuration this can degrade overall performance due to the operand cache line flushes that are implied by the "tas.b" instruction. On multi-core SH4A processors the "tas.b" instruction must be used with caution since it can result in data corruption for certain cache configurations. -mprefergot When generating position-independent code, emit function calls using the Global Offset Table instead of the Procedure Linkage Table. -musermode -mno-usermode Don't allow (allow) the compiler generating privileged mode code. Specifying -musermode also implies -mno-inline-ic_invalidate if the inlined code would not work in user mode. -musermode is the default when the target is "sh*-*-linux*". If the target is SH1* or SH2* -musermode has no effect, since there is no user mode. -multcost=number Set the cost to assume for a multiply insn. -mdiv=strategy Set the division strategy to be used for integer division operations. strategy can be one of: call-div1 Calls a library function that uses the single-step division instruction "div1" to perform the operation. Division by zero calculates an unspecified result and does not trap. This is the default except for SH4, SH2A and SHcompact. call-fp Calls a library function that performs the operation in double precision floating point. Division by zero causes a floating- point exception. This is the default for SHcompact with FPU. Specifying this for targets that do not have a double precision FPU defaults to "call-div1". call-table Calls a library function that uses a lookup table for small divisors and the "div1" instruction with case distinction for larger divisors. Division by zero calculates an unspecified result and does not trap. This is the default for SH4. Specifying this for targets that do not have dynamic shift instructions defaults to "call-div1". When a division strategy has not been specified the default strategy is selected based on the current target. For SH2A the default strategy is to use the "divs" and "divu" instructions instead of library function calls. -maccumulate-outgoing-args Reserve space once for outgoing arguments in the function prologue rather than around each call. Generally beneficial for performance and size. Also needed for unwinding to avoid changing the stack frame around conditional code. -mdivsi3_libfunc=name Set the name of the library function used for 32-bit signed division to name. This only affects the name used in the call division strategies, and the compiler still expects the same sets of input/output/clobbered registers as if this option were not present. -mfixed-range=register-range Generate code treating the given register range as fixed registers. A fixed register is one that the register allocator cannot use. This is useful when compiling kernel code. A register range is specified as two registers separated by a dash. Multiple register ranges can be specified separated by a comma. -mbranch-cost=num Assume num to be the cost for a branch instruction. Higher numbers make the compiler try to generate more branch-free code if possible. If not specified the value is selected depending on the processor type that is being compiled for. -mzdcbranch -mno-zdcbranch Assume (do not assume) that zero displacement conditional branch instructions "bt" and "bf" are fast. If -mzdcbranch is specified, the compiler prefers zero displacement branch code sequences. This is enabled by default when generating code for SH4 and SH4A. It can be explicitly disabled by specifying -mno-zdcbranch. -mcbranch-force-delay-slot Force the usage of delay slots for conditional branches, which stuffs the delay slot with a "nop" if a suitable instruction cannot be found. By default this option is disabled. It can be enabled to work around hardware bugs as found in the original SH7055. -mfused-madd -mno-fused-madd Generate code that uses (does not use) the floating-point multiply and accumulate instructions. These instructions are generated by default if hardware floating point is used. The machine-dependent -mfused-madd option is now mapped to the machine-independent -ffp-contract=fast option, and -mno-fused-madd is mapped to -ffp-contract=off. -mfsca -mno-fsca Allow or disallow the compiler to emit the "fsca" instruction for sine and cosine approximations. The option -mfsca must be used in combination with -funsafe-math-optimizations. It is enabled by default when generating code for SH4A. Using -mno-fsca disables sine and cosine approximations even if -funsafe-math-optimizations is in effect. -mfsrra -mno-fsrra Allow or disallow the compiler to emit the "fsrra" instruction for reciprocal square root approximations. The option -mfsrra must be used in combination with -funsafe-math-optimizations and -ffinite-math-only. It is enabled by default when generating code for SH4A. Using -mno-fsrra disables reciprocal square root approximations even if -funsafe-math-optimizations and -ffinite-math-only are in effect. -mpretend-cmove Prefer zero-displacement conditional branches for conditional move instruction patterns. This can result in faster code on the SH4 processor. -mfdpic Generate code using the FDPIC ABI. Solaris 2 Options These -m options are supported on Solaris 2: -mclear-hwcap -mclear-hwcap tells the compiler to remove the hardware capabilities generated by the Solaris assembler. This is only necessary when object files use ISA extensions not supported by the current machine, but check at runtime whether or not to use them. -mimpure-text -mimpure-text, used in addition to -shared, tells the compiler to not pass -z text to the linker when linking a shared object. Using this option, you can link position-dependent code into a shared object. -mimpure-text suppresses the "relocations remain against allocatable but non-writable sections" linker error message. However, the necessary relocations trigger copy-on-write, and the shared object is not actually shared across processes. Instead of using -mimpure-text, you should compile all source code with -fpic or -fPIC. These switches are supported in addition to the above on Solaris 2: -pthreads This is a synonym for -pthread. SPARC Options These -m options are supported on the SPARC: -mno-app-regs -mapp-regs Specify -mapp-regs to generate output using the global registers 2 through 4, which the SPARC SVR4 ABI reserves for applications. Like the global register 1, each global register 2 through 4 is then treated as an allocable register that is clobbered by function calls. This is the default. To be fully SVR4 ABI-compliant at the cost of some performance loss, specify -mno-app-regs. You should compile libraries and system software with this option. -mflat -mno-flat With -mflat, the compiler does not generate save/restore instructions and uses a "flat" or single register window model. This model is compatible with the regular register window model. The local registers and the input registers (0--5) are still treated as "call-saved" registers and are saved on the stack as needed. With -mno-flat (the default), the compiler generates save/restore instructions (except for leaf functions). This is the normal operating mode. -mfpu -mhard-float Generate output containing floating-point instructions. This is the default. -mno-fpu -msoft-float Generate output containing library calls for floating point. Warning: the requisite libraries are not available for all SPARC targets. Normally the facilities of the machine's usual C compiler are used, but this cannot be done directly in cross-compilation. You must make your own arrangements to provide suitable library functions for cross-compilation. The embedded targets sparc-*-aout and sparclite-*-* do provide software floating-point support. -msoft-float changes the calling convention in the output file; therefore, it is only useful if you compile all of a program with this option. In particular, you need to compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this to work. -mhard-quad-float Generate output containing quad-word (long double) floating-point instructions. -msoft-quad-float Generate output containing library calls for quad-word (long double) floating-point instructions. The functions called are those specified in the SPARC ABI. This is the default. As of this writing, there are no SPARC implementations that have hardware support for the quad-word floating-point instructions. They all invoke a trap handler for one of these instructions, and then the trap handler emulates the effect of the instruction. Because of the trap handler overhead, this is much slower than calling the ABI library routines. Thus the -msoft-quad-float option is the default. -mno-unaligned-doubles -munaligned-doubles Assume that doubles have 8-byte alignment. This is the default. With -munaligned-doubles, GCC assumes that doubles have 8-byte alignment only if they are contained in another type, or if they have an absolute address. Otherwise, it assumes they have 4-byte alignment. Specifying this option avoids some rare compatibility problems with code generated by other compilers. It is not the default because it results in a performance loss, especially for floating-point code. -muser-mode -mno-user-mode Do not generate code that can only run in supervisor mode. This is relevant only for the "casa" instruction emitted for the LEON3 processor. This is the default. -mfaster-structs -mno-faster-structs With -mfaster-structs, the compiler assumes that structures should have 8-byte alignment. This enables the use of pairs of "ldd" and "std" instructions for copies in structure assignment, in place of twice as many "ld" and "st" pairs. However, the use of this changed alignment directly violates the SPARC ABI. Thus, it's intended only for use on targets where the developer acknowledges that their resulting code is not directly in line with the rules of the ABI. -mstd-struct-return -mno-std-struct-return With -mstd-struct-return, the compiler generates checking code in functions returning structures or unions to detect size mismatches between the two sides of function calls, as per the 32-bit ABI. The default is -mno-std-struct-return. This option has no effect in 64-bit mode. -mlra -mno-lra Enable Local Register Allocation. This is the default for SPARC since GCC 7 so -mno-lra needs to be passed to get old Reload. -mcpu=cpu_type Set the instruction set, register set, and instruction scheduling parameters for machine type cpu_type. Supported values for cpu_type are v7, cypress, v8, supersparc, hypersparc, leon, leon3, leon3v7, leon5, sparclite, f930, f934, sparclite86x, sparclet, tsc701, v9, ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4, niagara7 and m8. Native Solaris and GNU/Linux toolchains also support the value native, which selects the best architecture option for the host processor. -mcpu=native has no effect if GCC does not recognize the processor. Default instruction scheduling parameters are used for values that select an architecture and not an implementation. These are v7, v8, sparclite, sparclet, v9. Here is a list of each supported architecture and their supported implementations. v7 cypress, leon3v7 v8 supersparc, hypersparc, leon, leon3, leon5 sparclite f930, f934, sparclite86x sparclet tsc701 v9 ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4, niagara7, m8 By default (unless configured otherwise), GCC generates code for the V7 variant of the SPARC architecture. With -mcpu=cypress, the compiler additionally optimizes it for the Cypress CY7C602 chip, as used in the SPARCStation/SPARCServer 3xx series. This is also appropriate for the older SPARCStation 1, 2, IPX etc. With -mcpu=v8, GCC generates code for the V8 variant of the SPARC architecture. The only difference from V7 code is that the compiler emits the integer multiply and integer divide instructions which exist in SPARC-V8 but not in SPARC-V7. With -mcpu=supersparc, the compiler additionally optimizes it for the SuperSPARC chip, as used in the SPARCStation 10, 1000 and 2000 series. With -mcpu=sparclite, GCC generates code for the SPARClite variant of the SPARC architecture. This adds the integer multiply, integer divide step and scan ("ffs") instructions which exist in SPARClite but not in SPARC-V7. With -mcpu=f930, the compiler additionally optimizes it for the Fujitsu MB86930 chip, which is the original SPARClite, with no FPU. With -mcpu=f934, the compiler additionally optimizes it for the Fujitsu MB86934 chip, which is the more recent SPARClite with FPU. With -mcpu=sparclet, GCC generates code for the SPARClet variant of the SPARC architecture. This adds the integer multiply, multiply/accumulate, integer divide step and scan ("ffs") instructions which exist in SPARClet but not in SPARC-V7. With -mcpu=tsc701, the compiler additionally optimizes it for the TEMIC SPARClet chip. With -mcpu=v9, GCC generates code for the V9 variant of the SPARC architecture. This adds 64-bit integer and floating-point move instructions, 3 additional floating-point condition code registers and conditional move instructions. With -mcpu=ultrasparc, the compiler additionally optimizes it for the Sun UltraSPARC I/II/IIi chips. With -mcpu=ultrasparc3, the compiler additionally optimizes it for the Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+ chips. With -mcpu=niagara, the compiler additionally optimizes it for Sun UltraSPARC T1 chips. With -mcpu=niagara2, the compiler additionally optimizes it for Sun UltraSPARC T2 chips. With -mcpu=niagara3, the compiler additionally optimizes it for Sun UltraSPARC T3 chips. With -mcpu=niagara4, the compiler additionally optimizes it for Sun UltraSPARC T4 chips. With -mcpu=niagara7, the compiler additionally optimizes it for Oracle SPARC M7 chips. With -mcpu=m8, the compiler additionally optimizes it for Oracle M8 chips. -mtune=cpu_type Set the instruction scheduling parameters for machine type cpu_type, but do not set the instruction set or register set that the option -mcpu=cpu_type does. The same values for -mcpu=cpu_type can be used for -mtune=cpu_type, but the only useful values are those that select a particular CPU implementation. Those are cypress, supersparc, hypersparc, leon, leon3, leon3v7, leon5, f930, f934, sparclite86x, tsc701, ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4, niagara7 and m8. With native Solaris and GNU/Linux toolchains, native can also be used. -mv8plus -mno-v8plus With -mv8plus, GCC generates code for the SPARC-V8+ ABI. The difference from the V8 ABI is that the global and out registers are considered 64 bits wide. This is enabled by default on Solaris in 32-bit mode for all SPARC-V9 processors. -mvis -mno-vis With -mvis, GCC generates code that takes advantage of the UltraSPARC Visual Instruction Set extensions. The default is -mno-vis. -mvis2 -mno-vis2 With -mvis2, GCC generates code that takes advantage of version 2.0 of the UltraSPARC Visual Instruction Set extensions. The default is -mvis2 when targeting a cpu that supports such instructions, such as UltraSPARC-III and later. Setting -mvis2 also sets -mvis. -mvis3 -mno-vis3 With -mvis3, GCC generates code that takes advantage of version 3.0 of the UltraSPARC Visual Instruction Set extensions. The default is -mvis3 when targeting a cpu that supports such instructions, such as niagara-3 and later. Setting -mvis3 also sets -mvis2 and -mvis. -mvis4 -mno-vis4 With -mvis4, GCC generates code that takes advantage of version 4.0 of the UltraSPARC Visual Instruction Set extensions. The default is -mvis4 when targeting a cpu that supports such instructions, such as niagara-7 and later. Setting -mvis4 also sets -mvis3, -mvis2 and -mvis. -mvis4b -mno-vis4b With -mvis4b, GCC generates code that takes advantage of version 4.0 of the UltraSPARC Visual Instruction Set extensions, plus the additional VIS instructions introduced in the Oracle SPARC Architecture 2017. The default is -mvis4b when targeting a cpu that supports such instructions, such as m8 and later. Setting -mvis4b also sets -mvis4, -mvis3, -mvis2 and -mvis. -mcbcond -mno-cbcond With -mcbcond, GCC generates code that takes advantage of the UltraSPARC Compare-and-Branch-on-Condition instructions. The default is -mcbcond when targeting a CPU that supports such instructions, such as Niagara-4 and later. -mfmaf -mno-fmaf With -mfmaf, GCC generates code that takes advantage of the UltraSPARC Fused Multiply-Add Floating-point instructions. The default is -mfmaf when targeting a CPU that supports such instructions, such as Niagara-3 and later. -mfsmuld -mno-fsmuld With -mfsmuld, GCC generates code that takes advantage of the Floating-point Multiply Single to Double (FsMULd) instruction. The default is -mfsmuld when targeting a CPU supporting the architecture versions V8 or V9 with FPU except -mcpu=leon. -mpopc -mno-popc With -mpopc, GCC generates code that takes advantage of the UltraSPARC Population Count instruction. The default is -mpopc when targeting a CPU that supports such an instruction, such as Niagara-2 and later. -msubxc -mno-subxc With -msubxc, GCC generates code that takes advantage of the UltraSPARC Subtract-Extended-with-Carry instruction. The default is -msubxc when targeting a CPU that supports such an instruction, such as Niagara-7 and later. -mfix-at697f Enable the documented workaround for the single erratum of the Atmel AT697F processor (which corresponds to erratum #13 of the AT697E processor). -mfix-ut699 Enable the documented workarounds for the floating-point errata and the data cache nullify errata of the UT699 processor. -mfix-ut700 Enable the documented workaround for the back-to-back store errata of the UT699E/UT700 processor. -mfix-gr712rc Enable the documented workaround for the back-to-back store errata of the GR712RC processor. These -m options are supported in addition to the above on SPARC-V9 processors in 64-bit environments: -m32 -m64 Generate code for a 32-bit or 64-bit environment. The 32-bit environment sets int, long and pointer to 32 bits. The 64-bit environment sets int to 32 bits and long and pointer to 64 bits. -mcmodel=which Set the code model to one of medlow The Medium/Low code model: 64-bit addresses, programs must be linked in the low 32 bits of memory. Programs can be statically or dynamically linked. medmid The Medium/Middle code model: 64-bit addresses, programs must be linked in the low 44 bits of memory, the text and data segments must be less than 2GB in size and the data segment must be located within 2GB of the text segment. medany The Medium/Anywhere code model: 64-bit addresses, programs may be linked anywhere in memory, the text and data segments must be less than 2GB in size and the data segment must be located within 2GB of the text segment. embmedany The Medium/Anywhere code model for embedded systems: 64-bit addresses, the text and data segments must be less than 2GB in size, both starting anywhere in memory (determined at link time). The global register %g4 points to the base of the data segment. Programs are statically linked and PIC is not supported. -mmemory-model=mem-model Set the memory model in force on the processor to one of default The default memory model for the processor and operating system. rmo Relaxed Memory Order pso Partial Store Order tso Total Store Order sc Sequential Consistency These memory models are formally defined in Appendix D of the SPARC-V9 architecture manual, as set in the processor's "PSTATE.MM" field. -mstack-bias -mno-stack-bias With -mstack-bias, GCC assumes that the stack pointer, and frame pointer if present, are offset by -2047 which must be added back when making stack frame references. This is the default in 64-bit mode. Otherwise, assume no such offset is present. Options for System V These additional options are available on System V Release 4 for compatibility with other compilers on those systems: -G Create a shared object. It is recommended that -symbolic or -shared be used instead. -Qy Identify the versions of each tool used by the compiler, in a ".ident" assembler directive in the output. -Qn Refrain from adding ".ident" directives to the output file (this is the default). -YP,dirs Search the directories dirs, and no others, for libraries specified with -l. -Ym,dir Look in the directory dir to find the M4 preprocessor. The assembler uses this option. V850 Options These -m options are defined for V850 implementations: -mlong-calls -mno-long-calls Treat all calls as being far away (near). If calls are assumed to be far away, the compiler always loads the function's address into a register, and calls indirect through the pointer. -mno-ep -mep Do not optimize (do optimize) basic blocks that use the same index pointer 4 or more times to copy pointer into the "ep" register, and use the shorter "sld" and "sst" instructions. The -mep option is on by default if you optimize. -mno-prolog-function -mprolog-function Do not use (do use) external functions to save and restore registers at the prologue and epilogue of a function. The external functions are slower, but use less code space if more than one function saves the same number of registers. The -mprolog-function option is on by default if you optimize. -mspace Try to make the code as small as possible. At present, this just turns on the -mep and -mprolog-function options. -mtda=n Put static or global variables whose size is n bytes or less into the tiny data area that register "ep" points to. The tiny data area can hold up to 256 bytes in total (128 bytes for byte references). -msda=n Put static or global variables whose size is n bytes or less into the small data area that register "gp" points to. The small data area can hold up to 64 kilobytes. -mzda=n Put static or global variables whose size is n bytes or less into the first 32 kilobytes of memory. -mv850 Specify that the target processor is the V850. -mv850e3v5 Specify that the target processor is the V850E3V5. The preprocessor constant "__v850e3v5__" is defined if this option is used. -mv850e2v4 Specify that the target processor is the V850E3V5. This is an alias for the -mv850e3v5 option. -mv850e2v3 Specify that the target processor is the V850E2V3. The preprocessor constant "__v850e2v3__" is defined if this option is used. -mv850e2 Specify that the target processor is the V850E2. The preprocessor constant "__v850e2__" is defined if this option is used. -mv850e1 Specify that the target processor is the V850E1. The preprocessor constants "__v850e1__" and "__v850e__" are defined if this option is used. -mv850es Specify that the target processor is the V850ES. This is an alias for the -mv850e1 option. -mv850e Specify that the target processor is the V850E. The preprocessor constant "__v850e__" is defined if this option is used. If neither -mv850 nor -mv850e nor -mv850e1 nor -mv850e2 nor -mv850e2v3 nor -mv850e3v5 are defined then a default target processor is chosen and the relevant __v850*__ preprocessor constant is defined. The preprocessor constants "__v850" and "__v851__" are always defined, regardless of which processor variant is the target. -mdisable-callt -mno-disable-callt This option suppresses generation of the "CALLT" instruction for the v850e, v850e1, v850e2, v850e2v3 and v850e3v5 flavors of the v850 architecture. This option is enabled by default when the RH850 ABI is in use (see -mrh850-abi), and disabled by default when the GCC ABI is in use. If "CALLT" instructions are being generated then the C preprocessor symbol "__V850_CALLT__" is defined. -mrelax -mno-relax Pass on (or do not pass on) the -mrelax command-line option to the assembler. -mlong-jumps -mno-long-jumps Disable (or re-enable) the generation of PC-relative jump instructions. -msoft-float -mhard-float Disable (or re-enable) the generation of hardware floating point instructions. This option is only significant when the target architecture is V850E2V3 or higher. If hardware floating point instructions are being generated then the C preprocessor symbol "__FPU_OK__" is defined, otherwise the symbol "__NO_FPU__" is defined. -mloop Enables the use of the e3v5 LOOP instruction. The use of this instruction is not enabled by default when the e3v5 architecture is selected because its use is still experimental. -mrh850-abi -mghs Enables support for the RH850 version of the V850 ABI. This is the default. With this version of the ABI the following rules apply: * Integer sized structures and unions are returned via a memory pointer rather than a register. * Large structures and unions (more than 8 bytes in size) are passed by value. * Functions are aligned to 16-bit boundaries. * The -m8byte-align command-line option is supported. * The -mdisable-callt command-line option is enabled by default. The -mno-disable-callt command-line option is not supported. When this version of the ABI is enabled the C preprocessor symbol "__V850_RH850_ABI__" is defined. -mgcc-abi Enables support for the old GCC version of the V850 ABI. With this version of the ABI the following rules apply: * Integer sized structures and unions are returned in register "r10". * Large structures and unions (more than 8 bytes in size) are passed by reference. * Functions are aligned to 32-bit boundaries, unless optimizing for size. * The -m8byte-align command-line option is not supported. * The -mdisable-callt command-line option is supported but not enabled by default. When this version of the ABI is enabled the C preprocessor symbol "__V850_GCC_ABI__" is defined. -m8byte-align -mno-8byte-align Enables support for "double" and "long long" types to be aligned on 8-byte boundaries. The default is to restrict the alignment of all objects to at most 4-bytes. When -m8byte-align is in effect the C preprocessor symbol "__V850_8BYTE_ALIGN__" is defined. -mbig-switch Generate code suitable for big switch tables. Use this option only if the assembler/linker complain about out of range branches within a switch table. -mapp-regs This option causes r2 and r5 to be used in the code generated by the compiler. This setting is the default. -mno-app-regs This option causes r2 and r5 to be treated as fixed registers. VAX Options These -m options are defined for the VAX: -munix Do not output certain jump instructions ("aobleq" and so on) that the Unix assembler for the VAX cannot handle across long ranges. -mgnu Do output those jump instructions, on the assumption that the GNU assembler is being used. -mg Output code for G-format floating-point numbers instead of D-format. -mlra -mno-lra Enable Local Register Allocation. This is still experimental for the VAX, so by default the compiler uses standard reload. Visium Options -mdebug A program which performs file I/O and is destined to run on an MCM target should be linked with this option. It causes the libraries libc.a and libdebug.a to be linked. The program should be run on the target under the control of the GDB remote debugging stub. -msim A program which performs file I/O and is destined to run on the simulator should be linked with option. This causes libraries libc.a and libsim.a to be linked. -mfpu -mhard-float Generate code containing floating-point instructions. This is the default. -mno-fpu -msoft-float Generate code containing library calls for floating-point. -msoft-float changes the calling convention in the output file; therefore, it is only useful if you compile all of a program with this option. In particular, you need to compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this to work. -mcpu=cpu_type Set the instruction set, register set, and instruction scheduling parameters for machine type cpu_type. Supported values for cpu_type are mcm, gr5 and gr6. mcm is a synonym of gr5 present for backward compatibility. By default (unless configured otherwise), GCC generates code for the GR5 variant of the Visium architecture. With -mcpu=gr6, GCC generates code for the GR6 variant of the Visium architecture. The only difference from GR5 code is that the compiler will generate block move instructions. -mtune=cpu_type Set the instruction scheduling parameters for machine type cpu_type, but do not set the instruction set or register set that the option -mcpu=cpu_type would. -msv-mode Generate code for the supervisor mode, where there are no restrictions on the access to general registers. This is the default. -muser-mode Generate code for the user mode, where the access to some general registers is forbidden: on the GR5, registers r24 to r31 cannot be accessed in this mode; on the GR6, only registers r29 to r31 are affected. VMS Options These -m options are defined for the VMS implementations: -mvms-return-codes Return VMS condition codes from "main". The default is to return POSIX-style condition (e.g. error) codes. -mdebug-main=prefix Flag the first routine whose name starts with prefix as the main routine for the debugger. -mmalloc64 Default to 64-bit memory allocation routines. -mpointer-size=size Set the default size of pointers. Possible options for size are 32 or short for 32 bit pointers, 64 or long for 64 bit pointers, and no for supporting only 32 bit pointers. The later option disables "pragma pointer_size". VxWorks Options The options in this section are defined for all VxWorks targets. Options specific to the target hardware are listed with the other options for that target. -mrtp GCC can generate code for both VxWorks kernels and real time processes (RTPs). This option switches from the former to the latter. It also defines the preprocessor macro "__RTP__". -non-static Link an RTP executable against shared libraries rather than static libraries. The options -static and -shared can also be used for RTPs; -static is the default. -Bstatic -Bdynamic These options are passed down to the linker. They are defined for compatibility with Diab. -Xbind-lazy Enable lazy binding of function calls. This option is equivalent to -Wl,-z,now and is defined for compatibility with Diab. -Xbind-now Disable lazy binding of function calls. This option is the default and is defined for compatibility with Diab. x86 Options These -m options are defined for the x86 family of computers. -march=cpu-type Generate instructions for the machine type cpu-type. In contrast to -mtune=cpu-type, which merely tunes the generated code for the specified cpu-type, -march=cpu-type allows GCC to generate code that may not run at all on processors other than the one indicated. Specifying -march=cpu-type implies -mtune=cpu-type, except where noted otherwise. The choices for cpu-type are: native This selects the CPU to generate code for at compilation time by determining the processor type of the compiling machine. Using -march=native enables all instruction subsets supported by the local machine (hence the result might not run on different machines). Using -mtune=native produces code optimized for the local machine under the constraints of the selected instruction set. x86-64 A generic CPU with 64-bit extensions. x86-64-v2 x86-64-v3 x86-64-v4 These choices for cpu-type select the corresponding micro- architecture level from the x86-64 psABI. On ABIs other than the x86-64 psABI they select the same CPU features as the x86-64 psABI documents for the particular micro-architecture level. Since these cpu-type values do not have a corresponding -mtune setting, using -march with these values enables generic tuning. Specific tuning can be enabled using the -mtune=other-cpu-type option with an appropriate other-cpu-type value. i386 Original Intel i386 CPU. i486 Intel i486 CPU. (No scheduling is implemented for this chip.) i586 pentium Intel Pentium CPU with no MMX support. lakemont Intel Lakemont MCU, based on Intel Pentium CPU. pentium-mmx Intel Pentium MMX CPU, based on Pentium core with MMX instruction set support. pentiumpro Intel Pentium Pro CPU. i686 When used with -march, the Pentium Pro instruction set is used, so the code runs on all i686 family chips. When used with -mtune, it has the same meaning as generic. pentium2 Intel Pentium II CPU, based on Pentium Pro core with MMX and FXSR instruction set support. pentium3 pentium3m Intel Pentium III CPU, based on Pentium Pro core with MMX, FXSR and SSE instruction set support. pentium-m Intel Pentium M; low-power version of Intel Pentium III CPU with MMX, SSE, SSE2 and FXSR instruction set support. Used by Centrino notebooks. pentium4 pentium4m Intel Pentium 4 CPU with MMX, SSE, SSE2 and FXSR instruction set support. prescott Improved version of Intel Pentium 4 CPU with MMX, SSE, SSE2, SSE3 and FXSR instruction set support. nocona Improved version of Intel Pentium 4 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and FXSR instruction set support. core2 Intel Core 2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, CX16, SAHF and FXSR instruction set support. nehalem Intel Nehalem CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF and FXSR instruction set support. westmere Intel Westmere CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR and PCLMUL instruction set support. sandybridge Intel Sandy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE and PCLMUL instruction set support. ivybridge Intel Ivy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND and F16C instruction set support. haswell Intel Haswell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE and HLE instruction set support. broadwell Intel Broadwell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX and PREFETCHW instruction set support. skylake Intel Skylake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES and SGX instruction set support. bonnell Intel Bonnell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set support. silvermont Intel Silvermont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, PCLMUL, PREFETCHW and RDRND instruction set support. goldmont Intel Goldmont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, PCLMUL, PREFETCHW, RDRND, AES, SHA, RDSEED, XSAVE, XSAVEC, XSAVES, XSAVEOPT, CLFLUSHOPT and FSGSBASE instruction set support. goldmont-plus Intel Goldmont Plus CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, PCLMUL, PREFETCHW, RDRND, AES, SHA, RDSEED, XSAVE, XSAVEC, XSAVES, XSAVEOPT, CLFLUSHOPT, FSGSBASE, PTWRITE, RDPID and SGX instruction set support. tremont Intel Tremont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, PCLMUL, PREFETCHW, RDRND, AES, SHA, RDSEED, XSAVE, XSAVEC, XSAVES, XSAVEOPT, CLFLUSHOPT, FSGSBASE, PTWRITE, RDPID, SGX, CLWB, GFNI-SSE, MOVDIRI, MOVDIR64B, CLDEMOTE and WAITPKG instruction set support. sierraforest Intel Sierra Forest CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES, XSAVEOPT, FSGSBASE, PTWRITE, RDPID, SGX, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B, CLDEMOTE, WAITPKG, ADCX, AVX, AVX2, BMI, BMI2, F16C, FMA, LZCNT, PCONFIG, PKU, VAES, VPCLMULQDQ, SERIALIZE, HRESET, KL, WIDEKL, AVX-VNNI, AVXIFMA, AVXVNNIINT8, AVXNECONVERT, CMPCCXADD, ENQCMD and UINTR instruction set support. grandridge Intel Grand Ridge CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES, XSAVEOPT, FSGSBASE, PTWRITE, RDPID, SGX, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B, CLDEMOTE, WAITPKG, ADCX, AVX, AVX2, BMI, BMI2, F16C, FMA, LZCNT, PCONFIG, PKU, VAES, VPCLMULQDQ, SERIALIZE, HRESET, KL, WIDEKL, AVX-VNNI, AVXIFMA, AVXVNNIINT8, AVXNECONVERT, CMPCCXADD, ENQCMD, UINTR and RAOINT instruction set support. knl Intel Knight's Landing CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AVX512PF, AVX512ER, AVX512F, AVX512CD and PREFETCHWT1 instruction set support. knm Intel Knights Mill CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AVX512PF, AVX512ER, AVX512F, AVX512CD and PREFETCHWT1, AVX5124VNNIW, AVX5124FMAPS and AVX512VPOPCNTDQ instruction set support. skylake-avx512 Intel Skylake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, CLWB, AVX512VL, AVX512BW, AVX512DQ and AVX512CD instruction set support. cannonlake Intel Cannonlake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD, PKU, AVX512VBMI, AVX512IFMA and SHA instruction set support. icelake-client Intel Icelake Client CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD, PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2 , VPCLMULQDQ, AVX512BITALG, RDPID and AVX512VPOPCNTDQ instruction set support. icelake-server Intel Icelake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD, PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2 , VPCLMULQDQ, AVX512BITALG, RDPID, AVX512VPOPCNTDQ, PCONFIG, WBNOINVD and CLWB instruction set support. cascadelake Intel Cascadelake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, CLWB, AVX512VL, AVX512BW, AVX512DQ, AVX512CD and AVX512VNNI instruction set support. cooperlake Intel cooperlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, CLWB, AVX512VL, AVX512BW, AVX512DQ, AVX512CD, AVX512VNNI and AVX512BF16 instruction set support. tigerlake Intel Tigerlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2, VPCLMULQDQ, AVX512BITALG, RDPID, AVX512VPOPCNTDQ, MOVDIRI, MOVDIR64B, CLWB, AVX512VP2INTERSECT and KEYLOCKER instruction set support. sapphirerapids Intel sapphirerapids CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD, PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2, VPCLMULQDQ, AVX512BITALG, RDPID, AVX512VPOPCNTDQ, PCONFIG, WBNOINVD, CLWB, MOVDIRI, MOVDIR64B, ENQCMD, CLDEMOTE, PTWRITE, WAITPKG, SERIALIZE, TSXLDTRK, UINTR, AMX-BF16, AMX-TILE, AMX-INT8, AVX-VNNI, AVX512-FP16 and AVX512BF16 instruction set support. alderlake Intel Alderlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES, XSAVEOPT, FSGSBASE, PTWRITE, RDPID, SGX, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B, CLDEMOTE, WAITPKG, ADCX, AVX, AVX2, BMI, BMI2, F16C, FMA, LZCNT, PCONFIG, PKU, VAES, VPCLMULQDQ, SERIALIZE, HRESET, KL, WIDEKL and AVX-VNNI instruction set support. rocketlake Intel Rocketlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3 , SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2, VPCLMULQDQ, AVX512BITALG, RDPID and AVX512VPOPCNTDQ instruction set support. graniterapids Intel graniterapids CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD, PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2, VPCLMULQDQ, AVX512BITALG, RDPID, AVX512VPOPCNTDQ, PCONFIG, WBNOINVD, CLWB, MOVDIRI, MOVDIR64B, ENQCMD, CLDEMOTE, PTWRITE, WAITPKG, SERIALIZE, TSXLDTRK, UINTR, AMX-BF16, AMX-TILE, AMX-INT8, AVX-VNNI, AVX512-FP16, AVX512BF16, AMX-FP16 and PREFETCHI instruction set support. graniterapids-d Intel graniterapids D CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD, PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2, VPCLMULQDQ, AVX512BITALG, RDPID, AVX512VPOPCNTDQ, PCONFIG, WBNOINVD, CLWB, MOVDIRI, MOVDIR64B, ENQCMD, CLDEMOTE, PTWRITE, WAITPKG, SERIALIZE, TSXLDTRK, UINTR, AMX-BF16, AMX-TILE, AMX-INT8, AVX-VNNI, AVX512FP16, AVX512BF16, AMX-FP16, PREFETCHI and AMX-COMPLEX instruction set support. k6 AMD K6 CPU with MMX instruction set support. k6-2 k6-3 Improved versions of AMD K6 CPU with MMX and 3DNow! instruction set support. athlon athlon-tbird AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow! and SSE prefetch instructions support. athlon-4 athlon-xp athlon-mp Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow! and full SSE instruction set support. k8 opteron athlon64 athlon-fx Processors based on the AMD K8 core with x86-64 instruction set support, including the AMD Opteron, Athlon 64, and Athlon 64 FX processors. (This supersets MMX, SSE, SSE2, 3DNow!, enhanced 3DNow! and 64-bit instruction set extensions.) k8-sse3 opteron-sse3 athlon64-sse3 Improved versions of AMD K8 cores with SSE3 instruction set support. amdfam10 barcelona CPUs based on AMD Family 10h cores with x86-64 instruction set support. (This supersets MMX, SSE, SSE2, SSE3, SSE4A, 3DNow!, enhanced 3DNow!, ABM and 64-bit instruction set extensions.) bdver1 CPUs based on AMD Family 15h cores with x86-64 instruction set support. (This supersets FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.) bdver2 AMD Family 15h core based CPUs with x86-64 instruction set support. (This supersets BMI, TBM, F16C, FMA, FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.) bdver3 AMD Family 15h core based CPUs with x86-64 instruction set support. (This supersets BMI, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.) bdver4 AMD Family 15h core based CPUs with x86-64 instruction set support. (This supersets BMI, BMI2, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, AVX2, XOP, LWP, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.) znver1 AMD Family 17h core based CPUs with x86-64 instruction set support. (This supersets BMI, BMI2, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, and 64-bit instruction set extensions.) znver2 AMD Family 17h core based CPUs with x86-64 instruction set support. (This supersets BMI, BMI2, CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, RDPID, WBNOINVD, and 64-bit instruction set extensions.) znver3 AMD Family 19h core based CPUs with x86-64 instruction set support. (This supersets BMI, BMI2, CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, RDPID, WBNOINVD, PKU, VPCLMULQDQ, VAES, and 64-bit instruction set extensions.) znver4 AMD Family 19h core based CPUs with x86-64 instruction set support. (This supersets BMI, BMI2, CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, RDPID, WBNOINVD, PKU, VPCLMULQDQ, VAES, AVX512F, AVX512DQ, AVX512IFMA, AVX512CD, AVX512BW, AVX512VL, AVX512BF16, AVX512VBMI, AVX512VBMI2, AVX512VNNI, AVX512BITALG, AVX512VPOPCNTDQ, GFNI and 64-bit instruction set extensions.) btver1 CPUs based on AMD Family 14h cores with x86-64 instruction set support. (This supersets MMX, SSE, SSE2, SSE3, SSSE3, SSE4A, CX16, ABM and 64-bit instruction set extensions.) btver2 CPUs based on AMD Family 16h cores with x86-64 instruction set support. This includes MOVBE, F16C, BMI, AVX, PCLMUL, AES, SSE4.2, SSE4.1, CX16, ABM, SSE4A, SSSE3, SSE3, SSE2, SSE, MMX and 64-bit instruction set extensions. winchip-c6 IDT WinChip C6 CPU, dealt in same way as i486 with additional MMX instruction set support. winchip2 IDT WinChip 2 CPU, dealt in same way as i486 with additional MMX and 3DNow! instruction set support. c3 VIA C3 CPU with MMX and 3DNow! instruction set support. (No scheduling is implemented for this chip.) c3-2 VIA C3-2 (Nehemiah/C5XL) CPU with MMX and SSE instruction set support. (No scheduling is implemented for this chip.) c7 VIA C7 (Esther) CPU with MMX, SSE, SSE2 and SSE3 instruction set support. (No scheduling is implemented for this chip.) samuel-2 VIA Eden Samuel 2 CPU with MMX and 3DNow! instruction set support. (No scheduling is implemented for this chip.) nehemiah VIA Eden Nehemiah CPU with MMX and SSE instruction set support. (No scheduling is implemented for this chip.) esther VIA Eden Esther CPU with MMX, SSE, SSE2 and SSE3 instruction set support. (No scheduling is implemented for this chip.) eden-x2 VIA Eden X2 CPU with x86-64, MMX, SSE, SSE2 and SSE3 instruction set support. (No scheduling is implemented for this chip.) eden-x4 VIA Eden X4 CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, AVX and AVX2 instruction set support. (No scheduling is implemented for this chip.) nano Generic VIA Nano CPU with x86-64, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set support. (No scheduling is implemented for this chip.) nano-1000 VIA Nano 1xxx CPU with x86-64, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set support. (No scheduling is implemented for this chip.) nano-2000 VIA Nano 2xxx CPU with x86-64, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set support. (No scheduling is implemented for this chip.) nano-3000 VIA Nano 3xxx CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1 instruction set support. (No scheduling is implemented for this chip.) nano-x2 VIA Nano Dual Core CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1 instruction set support. (No scheduling is implemented for this chip.) nano-x4 VIA Nano Quad Core CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1 instruction set support. (No scheduling is implemented for this chip.) lujiazui ZHAOXIN lujiazui CPU with x86-64, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, AVX, POPCNT, AES, PCLMUL, RDRND, XSAVE, XSAVEOPT, FSGSBASE, CX16, ABM, BMI, BMI2, F16C, FXSR, RDSEED instruction set support. geode AMD Geode embedded processor with MMX and 3DNow! instruction set support. -mtune=cpu-type Tune to cpu-type everything applicable about the generated code, except for the ABI and the set of available instructions. While picking a specific cpu-type schedules things appropriately for that particular chip, the compiler does not generate any code that cannot run on the default machine type unless you use a -march=cpu- type option. For example, if GCC is configured for i686-pc-linux-gnu then -mtune=pentium4 generates code that is tuned for Pentium 4 but still runs on i686 machines. The choices for cpu-type are the same as for -march. In addition, -mtune supports 2 extra choices for cpu-type: generic Produce code optimized for the most common IA32/AMD64/EM64T processors. If you know the CPU on which your code will run, then you should use the corresponding -mtune or -march option instead of -mtune=generic. But, if you do not know exactly what CPU users of your application will have, then you should use this option. As new processors are deployed in the marketplace, the behavior of this option will change. Therefore, if you upgrade to a newer version of GCC, code generation controlled by this option will change to reflect the processors that are most common at the time that version of GCC is released. There is no -march=generic option because -march indicates the instruction set the compiler can use, and there is no generic instruction set applicable to all processors. In contrast, -mtune indicates the processor (or, in this case, collection of processors) for which the code is optimized. intel Produce code optimized for the most current Intel processors, which are Haswell and Silvermont for this version of GCC. If you know the CPU on which your code will run, then you should use the corresponding -mtune or -march option instead of -mtune=intel. But, if you want your application performs better on both Haswell and Silvermont, then you should use this option. As new Intel processors are deployed in the marketplace, the behavior of this option will change. Therefore, if you upgrade to a newer version of GCC, code generation controlled by this option will change to reflect the most current Intel processors at the time that version of GCC is released. There is no -march=intel option because -march indicates the instruction set the compiler can use, and there is no common instruction set applicable to all processors. In contrast, -mtune indicates the processor (or, in this case, collection of processors) for which the code is optimized. -mcpu=cpu-type A deprecated synonym for -mtune. -mfpmath=unit Generate floating-point arithmetic for selected unit unit. The choices for unit are: 387 Use the standard 387 floating-point coprocessor present on the majority of chips and emulated otherwise. Code compiled with this option runs almost everywhere. The temporary results are computed in 80-bit precision instead of the precision specified by the type, resulting in slightly different results compared to most of other chips. See -ffloat-store for more detailed description. This is the default choice for non-Darwin x86-32 targets. sse Use scalar floating-point instructions present in the SSE instruction set. This instruction set is supported by Pentium III and newer chips, and in the AMD line by Athlon-4, Athlon XP and Athlon MP chips. The earlier version of the SSE instruction set supports only single-precision arithmetic, thus the double and extended-precision arithmetic are still done using 387. A later version, present only in Pentium 4 and AMD x86-64 chips, supports double-precision arithmetic too. For the x86-32 compiler, you must use -march=cpu-type, -msse or -msse2 switches to enable SSE extensions and make this option effective. For the x86-64 compiler, these extensions are enabled by default. The resulting code should be considerably faster in the majority of cases and avoid the numerical instability problems of 387 code, but may break some existing code that expects temporaries to be 80 bits. This is the default choice for the x86-64 compiler, Darwin x86-32 targets, and the default choice for x86-32 targets with the SSE2 instruction set when -ffast-math is enabled. sse,387 sse+387 both Attempt to utilize both instruction sets at once. This effectively doubles the amount of available registers, and on chips with separate execution units for 387 and SSE the execution resources too. Use this option with care, as it is still experimental, because the GCC register allocator does not model separate functional units well, resulting in unstable performance. -masm=dialect Output assembly instructions using selected dialect. Also affects which dialect is used for basic "asm" and extended "asm". Supported choices (in dialect order) are att or intel. The default is att. Darwin does not support intel. -mieee-fp -mno-ieee-fp Control whether or not the compiler uses IEEE floating-point comparisons. These correctly handle the case where the result of a comparison is unordered. -m80387 -mhard-float Generate output containing 80387 instructions for floating point. -mno-80387 -msoft-float Generate output containing library calls for floating point. Warning: the requisite libraries are not part of GCC. Normally the facilities of the machine's usual C compiler are used, but this cannot be done directly in cross-compilation. You must make your own arrangements to provide suitable library functions for cross- compilation. On machines where a function returns floating-point results in the 80387 register stack, some floating-point opcodes may be emitted even if -msoft-float is used. -mno-fp-ret-in-387 Do not use the FPU registers for return values of functions. The usual calling convention has functions return values of types "float" and "double" in an FPU register, even if there is no FPU. The idea is that the operating system should emulate an FPU. The option -mno-fp-ret-in-387 causes such values to be returned in ordinary CPU registers instead. -mno-fancy-math-387 Some 387 emulators do not support the "sin", "cos" and "sqrt" instructions for the 387. Specify this option to avoid generating those instructions. This option is overridden when -march indicates that the target CPU always has an FPU and so the instruction does not need emulation. These instructions are not generated unless you also use the -funsafe-math-optimizations switch. -malign-double -mno-align-double Control whether GCC aligns "double", "long double", and "long long" variables on a two-word boundary or a one-word boundary. Aligning "double" variables on a two-word boundary produces code that runs somewhat faster on a Pentium at the expense of more memory. On x86-64, -malign-double is enabled by default. Warning: if you use the -malign-double switch, structures containing the above types are aligned differently than the published application binary interface specifications for the x86-32 and are not binary compatible with structures in code compiled without that switch. -m96bit-long-double -m128bit-long-double These switches control the size of "long double" type. The x86-32 application binary interface specifies the size to be 96 bits, so -m96bit-long-double is the default in 32-bit mode. Modern architectures (Pentium and newer) prefer "long double" to be aligned to an 8- or 16-byte boundary. In arrays or structures conforming to the ABI, this is not possible. So specifying -m128bit-long-double aligns "long double" to a 16-byte boundary by padding the "long double" with an additional 32-bit zero. In the x86-64 compiler, -m128bit-long-double is the default choice as its ABI specifies that "long double" is aligned on 16-byte boundary. Notice that neither of these options enable any extra precision over the x87 standard of 80 bits for a "long double". Warning: if you override the default value for your target ABI, this changes the size of structures and arrays containing "long double" variables, as well as modifying the function calling convention for functions taking "long double". Hence they are not binary-compatible with code compiled without that switch. -mlong-double-64 -mlong-double-80 -mlong-double-128 These switches control the size of "long double" type. A size of 64 bits makes the "long double" type equivalent to the "double" type. This is the default for 32-bit Bionic C library. A size of 128 bits makes the "long double" type equivalent to the "__float128" type. This is the default for 64-bit Bionic C library. Warning: if you override the default value for your target ABI, this changes the size of structures and arrays containing "long double" variables, as well as modifying the function calling convention for functions taking "long double". Hence they are not binary-compatible with code compiled without that switch. -malign-data=type Control how GCC aligns variables. Supported values for type are compat uses increased alignment value compatible uses GCC 4.8 and earlier, abi uses alignment value as specified by the psABI, and cacheline uses increased alignment value to match the cache line size. compat is the default. -mlarge-data-threshold=threshold When -mcmodel=medium is specified, data objects larger than threshold are placed in the large data section. This value must be the same across all objects linked into the binary, and defaults to 65535. -mrtd Use a different function-calling convention, in which functions that take a fixed number of arguments return with the "ret num" instruction, which pops their arguments while returning. This saves one instruction in the caller since there is no need to pop the arguments there. You can specify that an individual function is called with this calling sequence with the function attribute "stdcall". You can also override the -mrtd option by using the function attribute "cdecl". Warning: this calling convention is incompatible with the one normally used on Unix, so you cannot use it if you need to call libraries compiled with the Unix compiler. Also, you must provide function prototypes for all functions that take variable numbers of arguments (including "printf"); otherwise incorrect code is generated for calls to those functions. In addition, seriously incorrect code results if you call a function with too many arguments. (Normally, extra arguments are harmlessly ignored.) -mregparm=num Control how many registers are used to pass integer arguments. By default, no registers are used to pass arguments, and at most 3 registers can be used. You can control this behavior for a specific function by using the function attribute "regparm". Warning: if you use this switch, and num is nonzero, then you must build all modules with the same value, including any libraries. This includes the system libraries and startup modules. -msseregparm Use SSE register passing conventions for float and double arguments and return values. You can control this behavior for a specific function by using the function attribute "sseregparm". Warning: if you use this switch then you must build all modules with the same value, including any libraries. This includes the system libraries and startup modules. -mvect8-ret-in-mem Return 8-byte vectors in memory instead of MMX registers. This is the default on VxWorks to match the ABI of the Sun Studio compilers until version 12. Only use this option if you need to remain compatible with existing code produced by those previous compiler versions or older versions of GCC. -mpc32 -mpc64 -mpc80 Set 80387 floating-point precision to 32, 64 or 80 bits. When -mpc32 is specified, the significands of results of floating-point operations are rounded to 24 bits (single precision); -mpc64 rounds the significands of results of floating-point operations to 53 bits (double precision) and -mpc80 rounds the significands of results of floating-point operations to 64 bits (extended double precision), which is the default. When this option is used, floating-point operations in higher precisions are not available to the programmer without setting the FPU control word explicitly. Setting the rounding of floating-point operations to less than the default 80 bits can speed some programs by 2% or more. Note that some mathematical libraries assume that extended-precision (80-bit) floating-point operations are enabled by default; routines in such libraries could suffer significant loss of accuracy, typically through so-called "catastrophic cancellation", when this option is used to set the precision to less than extended precision. -mdaz-ftz The flush-to-zero (FTZ) and denormals-are-zero (DAZ) flags in the MXCSR register are used to control floating-point calculations.SSE and AVX instructions including scalar and vector instructions could benefit from enabling the FTZ and DAZ flags when -mdaz-ftz is specified. Don't set FTZ/DAZ flags when -mno-daz-ftz or -shared is specified, -mdaz-ftz will set FTZ/DAZ flags even with -shared. -mstackrealign Realign the stack at entry. On the x86, the -mstackrealign option generates an alternate prologue and epilogue that realigns the run- time stack if necessary. This supports mixing legacy codes that keep 4-byte stack alignment with modern codes that keep 16-byte stack alignment for SSE compatibility. See also the attribute "force_align_arg_pointer", applicable to individual functions. -mpreferred-stack-boundary=num Attempt to keep the stack boundary aligned to a 2 raised to num byte boundary. If -mpreferred-stack-boundary is not specified, the default is 4 (16 bytes or 128 bits). Warning: When generating code for the x86-64 architecture with SSE extensions disabled, -mpreferred-stack-boundary=3 can be used to keep the stack boundary aligned to 8 byte boundary. Since x86-64 ABI require 16 byte stack alignment, this is ABI incompatible and intended to be used in controlled environment where stack space is important limitation. This option leads to wrong code when functions compiled with 16 byte stack alignment (such as functions from a standard library) are called with misaligned stack. In this case, SSE instructions may lead to misaligned memory access traps. In addition, variable arguments are handled incorrectly for 16 byte aligned objects (including x87 long double and __int128), leading to wrong results. You must build all modules with -mpreferred-stack-boundary=3, including any libraries. This includes the system libraries and startup modules. -mincoming-stack-boundary=num Assume the incoming stack is aligned to a 2 raised to num byte boundary. If -mincoming-stack-boundary is not specified, the one specified by -mpreferred-stack-boundary is used. On Pentium and Pentium Pro, "double" and "long double" values should be aligned to an 8-byte boundary (see -malign-double) or suffer significant run time performance penalties. On Pentium III, the Streaming SIMD Extension (SSE) data type "__m128" may not work properly if it is not 16-byte aligned. To ensure proper alignment of this values on the stack, the stack boundary must be as aligned as that required by any value stored on the stack. Further, every function must be generated such that it keeps the stack aligned. Thus calling a function compiled with a higher preferred stack boundary from a function compiled with a lower preferred stack boundary most likely misaligns the stack. It is recommended that libraries that use callbacks always use the default setting. This extra alignment does consume extra stack space, and generally increases code size. Code that is sensitive to stack space usage, such as embedded systems and operating system kernels, may want to reduce the preferred alignment to -mpreferred-stack-boundary=2. -mmmx -msse -msse2 -msse3 -mssse3 -msse4 -msse4a -msse4.1 -msse4.2 -mavx -mavx2 -mavx512f -mavx512pf -mavx512er -mavx512cd -mavx512vl -mavx512bw -mavx512dq -mavx512ifma -mavx512vbmi -msha -maes -mpclmul -mclflushopt -mclwb -mfsgsbase -mptwrite -mrdrnd -mf16c -mfma -mpconfig -mwbnoinvd -mfma4 -mprfchw -mrdpid -mprefetchwt1 -mrdseed -msgx -mxop -mlwp -m3dnow -m3dnowa -mpopcnt -mabm -madx -mbmi -mbmi2 -mlzcnt -mfxsr -mxsave -mxsaveopt -mxsavec -mxsaves -mrtm -mhle -mtbm -mmwaitx -mclzero -mpku -mavx512vbmi2 -mavx512bf16 -mavx512fp16 -mgfni -mvaes -mwaitpkg -mvpclmulqdq -mavx512bitalg -mmovdiri -mmovdir64b -menqcmd -muintr -mtsxldtrk -mavx512vpopcntdq -mavx512vp2intersect -mavx5124fmaps -mavx512vnni -mavxvnni -mavx5124vnniw -mcldemote -mserialize -mamx-tile -mamx-int8 -mamx-bf16 -mhreset -mkl -mwidekl -mavxifma -mavxvnniint8 -mavxneconvert -mcmpccxadd -mamx-fp16 -mprefetchi -mraoint -mamx-complex These switches enable the use of instructions in the MMX, SSE, SSE2, SSE3, SSSE3, SSE4, SSE4A, SSE4.1, SSE4.2, AVX, AVX2, AVX512F, AVX512PF, AVX512ER, AVX512CD, AVX512VL, AVX512BW, AVX512DQ, AVX512IFMA, AVX512VBMI, SHA, AES, PCLMUL, CLFLUSHOPT, CLWB, FSGSBASE, PTWRITE, RDRND, F16C, FMA, PCONFIG, WBNOINVD, FMA4, PREFETCHW, RDPID, PREFETCHWT1, RDSEED, SGX, XOP, LWP, 3DNow!, enhanced 3DNow!, POPCNT, ABM, ADX, BMI, BMI2, LZCNT, FXSR, XSAVE, XSAVEOPT, XSAVEC, XSAVES, RTM, HLE, TBM, MWAITX, CLZERO, PKU, AVX512VBMI2, GFNI, VAES, WAITPKG, VPCLMULQDQ, AVX512BITALG, MOVDIRI, MOVDIR64B, AVX512BF16, ENQCMD, AVX512VPOPCNTDQ, AVX5124FMAPS, AVX512VNNI, AVX5124VNNIW, SERIALIZE, UINTR, HRESET, AMXTILE, AMXINT8, AMXBF16, KL, WIDEKL, AVXVNNI, AVX512-FP16, AVXIFMA, AVXVNNIINT8, AVXNECONVERT, CMPCCXADD, AMX-FP16, PREFETCHI, RAOINT, AMX-COMPLEX or CLDEMOTE extended instruction sets. Each has a corresponding -mno- option to disable use of these instructions. These extensions are also available as built-in functions: see x86 Built-in Functions, for details of the functions enabled and disabled by these switches. To generate SSE/SSE2 instructions automatically from floating-point code (as opposed to 387 instructions), see -mfpmath=sse. GCC depresses SSEx instructions when -mavx is used. Instead, it generates new AVX instructions or AVX equivalence for all SSEx instructions when needed. These options enable GCC to use these extended instructions in generated code, even without -mfpmath=sse. Applications that perform run-time CPU detection must compile separate files for each supported architecture, using the appropriate flags. In particular, the file containing the CPU detection code should be compiled without these options. -mdump-tune-features This option instructs GCC to dump the names of the x86 performance tuning features and default settings. The names can be used in -mtune-ctrl=feature-list. -mtune-ctrl=feature-list This option is used to do fine grain control of x86 code generation features. feature-list is a comma separated list of feature names. See also -mdump-tune-features. When specified, the feature is turned on if it is not preceded with ^, otherwise, it is turned off. -mtune-ctrl=feature-list is intended to be used by GCC developers. Using it may lead to code paths not covered by testing and can potentially result in compiler ICEs or runtime errors. -mno-default This option instructs GCC to turn off all tunable features. See also -mtune-ctrl=feature-list and -mdump-tune-features. -mcld This option instructs GCC to emit a "cld" instruction in the prologue of functions that use string instructions. String instructions depend on the DF flag to select between autoincrement or autodecrement mode. While the ABI specifies the DF flag to be cleared on function entry, some operating systems violate this specification by not clearing the DF flag in their exception dispatchers. The exception handler can be invoked with the DF flag set, which leads to wrong direction mode when string instructions are used. This option can be enabled by default on 32-bit x86 targets by configuring GCC with the --enable-cld configure option. Generation of "cld" instructions can be suppressed with the -mno-cld compiler option in this case. -mvzeroupper This option instructs GCC to emit a "vzeroupper" instruction before a transfer of control flow out of the function to minimize the AVX to SSE transition penalty as well as remove unnecessary "zeroupper" intrinsics. -mprefer-avx128 This option instructs GCC to use 128-bit AVX instructions instead of 256-bit AVX instructions in the auto-vectorizer. -mprefer-vector-width=opt This option instructs GCC to use opt-bit vector width in instructions instead of default on the selected platform. -mmove-max=bits This option instructs GCC to set the maximum number of bits can be moved from memory to memory efficiently to bits. The valid bits are 128, 256 and 512. -mstore-max=bits This option instructs GCC to set the maximum number of bits can be stored to memory efficiently to bits. The valid bits are 128, 256 and 512. none No extra limitations applied to GCC other than defined by the selected platform. 128 Prefer 128-bit vector width for instructions. 256 Prefer 256-bit vector width for instructions. 512 Prefer 512-bit vector width for instructions. -mcx16 This option enables GCC to generate "CMPXCHG16B" instructions in 64-bit code to implement compare-and-exchange operations on 16-byte aligned 128-bit objects. This is useful for atomic updates of data structures exceeding one machine word in size. The compiler uses this instruction to implement __sync Builtins. However, for __atomic Builtins operating on 128-bit integers, a library call is always used. -msahf This option enables generation of "SAHF" instructions in 64-bit code. Early Intel Pentium 4 CPUs with Intel 64 support, prior to the introduction of Pentium 4 G1 step in December 2005, lacked the "LAHF" and "SAHF" instructions which are supported by AMD64. These are load and store instructions, respectively, for certain status flags. In 64-bit mode, the "SAHF" instruction is used to optimize "fmod", "drem", and "remainder" built-in functions; see Other Builtins for details. -mmovbe This option enables use of the "movbe" instruction to implement "__builtin_bswap32" and "__builtin_bswap64". -mshstk The -mshstk option enables shadow stack built-in functions from x86 Control-flow Enforcement Technology (CET). -mcrc32 This option enables built-in functions "__builtin_ia32_crc32qi", "__builtin_ia32_crc32hi", "__builtin_ia32_crc32si" and "__builtin_ia32_crc32di" to generate the "crc32" machine instruction. -mmwait This option enables built-in functions "__builtin_ia32_monitor", and "__builtin_ia32_mwait" to generate the "monitor" and "mwait" machine instructions. -mrecip This option enables use of "RCPSS" and "RSQRTSS" instructions (and their vectorized variants "RCPPS" and "RSQRTPS") with an additional Newton-Raphson step to increase precision instead of "DIVSS" and "SQRTSS" (and their vectorized variants) for single-precision floating-point arguments. These instructions are generated only when -funsafe-math-optimizations is enabled together with -ffinite-math-only and -fno-trapping-math. Note that while the throughput of the sequence is higher than the throughput of the non-reciprocal instruction, the precision of the sequence can be decreased by up to 2 ulp (i.e. the inverse of 1.0 equals 0.99999994). Note that GCC implements "1.0f/sqrtf(x)" in terms of "RSQRTSS" (or "RSQRTPS") already with -ffast-math (or the above option combination), and doesn't need -mrecip. Also note that GCC emits the above sequence with additional Newton- Raphson step for vectorized single-float division and vectorized "sqrtf(x)" already with -ffast-math (or the above option combination), and doesn't need -mrecip. -mrecip=opt This option controls which reciprocal estimate instructions may be used. opt is a comma-separated list of options, which may be preceded by a ! to invert the option: all Enable all estimate instructions. default Enable the default instructions, equivalent to -mrecip. none Disable all estimate instructions, equivalent to -mno-recip. div Enable the approximation for scalar division. vec-div Enable the approximation for vectorized division. sqrt Enable the approximation for scalar square root. vec-sqrt Enable the approximation for vectorized square root. So, for example, -mrecip=all,!sqrt enables all of the reciprocal approximations, except for square root. -mveclibabi=type Specifies the ABI type to use for vectorizing intrinsics using an external library. Supported values for type are svml for the Intel short vector math library and acml for the AMD math core library. To use this option, both -ftree-vectorize and -funsafe-math-optimizations have to be enabled, and an SVML or ACML ABI-compatible library must be specified at link time. GCC currently emits calls to "vmldExp2", "vmldLn2", "vmldLog102", "vmldPow2", "vmldTanh2", "vmldTan2", "vmldAtan2", "vmldAtanh2", "vmldCbrt2", "vmldSinh2", "vmldSin2", "vmldAsinh2", "vmldAsin2", "vmldCosh2", "vmldCos2", "vmldAcosh2", "vmldAcos2", "vmlsExp4", "vmlsLn4", "vmlsLog104", "vmlsPow4", "vmlsTanh4", "vmlsTan4", "vmlsAtan4", "vmlsAtanh4", "vmlsCbrt4", "vmlsSinh4", "vmlsSin4", "vmlsAsinh4", "vmlsAsin4", "vmlsCosh4", "vmlsCos4", "vmlsAcosh4" and "vmlsAcos4" for corresponding function type when -mveclibabi=svml is used, and "__vrd2_sin", "__vrd2_cos", "__vrd2_exp", "__vrd2_log", "__vrd2_log2", "__vrd2_log10", "__vrs4_sinf", "__vrs4_cosf", "__vrs4_expf", "__vrs4_logf", "__vrs4_log2f", "__vrs4_log10f" and "__vrs4_powf" for the corresponding function type when -mveclibabi=acml is used. -mabi=name Generate code for the specified calling convention. Permissible values are sysv for the ABI used on GNU/Linux and other systems, and ms for the Microsoft ABI. The default is to use the Microsoft ABI when targeting Microsoft Windows and the SysV ABI on all other systems. You can control this behavior for specific functions by using the function attributes "ms_abi" and "sysv_abi". -mforce-indirect-call Force all calls to functions to be indirect. This is useful when using Intel Processor Trace where it generates more precise timing information for function calls. -mmanual-endbr Insert ENDBR instruction at function entry only via the "cf_check" function attribute. This is useful when used with the option -fcf-protection=branch to control ENDBR insertion at the function entry. -mcet-switch By default, CET instrumentation is turned off on switch statements that use a jump table and indirect branch track is disabled. Since jump tables are stored in read-only memory, this does not result in a direct loss of hardening. But if the jump table index is attacker-controlled, the indirect jump may not be constrained by CET. This option turns on CET instrumentation to enable indirect branch track for switch statements with jump tables which leads to the jump targets reachable via any indirect jumps. -mcall-ms2sysv-xlogues Due to differences in 64-bit ABIs, any Microsoft ABI function that calls a System V ABI function must consider RSI, RDI and XMM6-15 as clobbered. By default, the code for saving and restoring these registers is emitted inline, resulting in fairly lengthy prologues and epilogues. Using -mcall-ms2sysv-xlogues emits prologues and epilogues that use stubs in the static portion of libgcc to perform these saves and restores, thus reducing function size at the cost of a few extra instructions. -mtls-dialect=type Generate code to access thread-local storage using the gnu or gnu2 conventions. gnu is the conservative default; gnu2 is more efficient, but it may add compile- and run-time requirements that cannot be satisfied on all systems. -mpush-args -mno-push-args Use PUSH operations to store outgoing parameters. This method is shorter and usually equally fast as method using SUB/MOV operations and is enabled by default. In some cases disabling it may improve performance because of improved scheduling and reduced dependencies. -maccumulate-outgoing-args If enabled, the maximum amount of space required for outgoing arguments is computed in the function prologue. This is faster on most modern CPUs because of reduced dependencies, improved scheduling and reduced stack usage when the preferred stack boundary is not equal to 2. The drawback is a notable increase in code size. This switch implies -mno-push-args. -mthreads Support thread-safe exception handling on MinGW. Programs that rely on thread-safe exception handling must compile and link all code with the -mthreads option. When compiling, -mthreads defines -D_MT; when linking, it links in a special thread helper library -lmingwthrd which cleans up per-thread exception-handling data. -mms-bitfields -mno-ms-bitfields Enable/disable bit-field layout compatible with the native Microsoft Windows compiler. If "packed" is used on a structure, or if bit-fields are used, it may be that the Microsoft ABI lays out the structure differently than the way GCC normally does. Particularly when moving packed data between functions compiled with GCC and the native Microsoft compiler (either via function call or as data in a file), it may be necessary to access either format. This option is enabled by default for Microsoft Windows targets. This behavior can also be controlled locally by use of variable or type attributes. For more information, see x86 Variable Attributes and x86 Type Attributes. The Microsoft structure layout algorithm is fairly simple with the exception of the bit-field packing. The padding and alignment of members of structures and whether a bit-field can straddle a storage-unit boundary are determine by these rules: 1. Structure members are stored sequentially in the order in which they are declared: the first member has the lowest memory address and the last member the highest. 2. Every data object has an alignment requirement. The alignment requirement for all data except structures, unions, and arrays is either the size of the object or the current packing size (specified with either the "aligned" attribute or the "pack" pragma), whichever is less. For structures, unions, and arrays, the alignment requirement is the largest alignment requirement of its members. Every object is allocated an offset so that: offset % alignment_requirement == 0 3. Adjacent bit-fields are packed into the same 1-, 2-, or 4-byte allocation unit if the integral types are the same size and if the next bit-field fits into the current allocation unit without crossing the boundary imposed by the common alignment requirements of the bit-fields. MSVC interprets zero-length bit-fields in the following ways: 1. If a zero-length bit-field is inserted between two bit-fields that are normally coalesced, the bit-fields are not coalesced. For example: struct { unsigned long bf_1 : 12; unsigned long : 0; unsigned long bf_2 : 12; } t1; The size of "t1" is 8 bytes with the zero-length bit-field. If the zero-length bit-field were removed, "t1"'s size would be 4 bytes. 2. If a zero-length bit-field is inserted after a bit-field, "foo", and the alignment of the zero-length bit-field is greater than the member that follows it, "bar", "bar" is aligned as the type of the zero-length bit-field. For example: struct { char foo : 4; short : 0; char bar; } t2; struct { char foo : 4; short : 0; double bar; } t3; For "t2", "bar" is placed at offset 2, rather than offset 1. Accordingly, the size of "t2" is 4. For "t3", the zero-length bit-field does not affect the alignment of "bar" or, as a result, the size of the structure. Taking this into account, it is important to note the following: 1. If a zero-length bit-field follows a normal bit-field, the type of the zero-length bit-field may affect the alignment of the structure as whole. For example, "t2" has a size of 4 bytes, since the zero-length bit-field follows a normal bit-field, and is of type short. 2. Even if a zero-length bit-field is not followed by a normal bit-field, it may still affect the alignment of the structure: struct { char foo : 6; long : 0; } t4; Here, "t4" takes up 4 bytes. 3. Zero-length bit-fields following non-bit-field members are ignored: struct { char foo; long : 0; char bar; } t5; Here, "t5" takes up 2 bytes. -mno-align-stringops Do not align the destination of inlined string operations. This switch reduces code size and improves performance in case the destination is already aligned, but GCC doesn't know about it. -minline-all-stringops By default GCC inlines string operations only when the destination is known to be aligned to least a 4-byte boundary. This enables more inlining and increases code size, but may improve performance of code that depends on fast "memcpy" and "memset" for short lengths. The option enables inline expansion of "strlen" for all pointer alignments. -minline-stringops-dynamically For string operations of unknown size, use run-time checks with inline code for small blocks and a library call for large blocks. -mstringop-strategy=alg Override the internal decision heuristic for the particular algorithm to use for inlining string operations. The allowed values for alg are: rep_byte rep_4byte rep_8byte Expand using i386 "rep" prefix of the specified size. byte_loop loop unrolled_loop Expand into an inline loop. libcall Always use a library call. -mmemcpy-strategy=strategy Override the internal decision heuristic to decide if "__builtin_memcpy" should be inlined and what inline algorithm to use when the expected size of the copy operation is known. strategy is a comma-separated list of alg:max_size:dest_align triplets. alg is specified in -mstringop-strategy, max_size specifies the max byte size with which inline algorithm alg is allowed. For the last triplet, the max_size must be "-1". The max_size of the triplets in the list must be specified in increasing order. The minimal byte size for alg is 0 for the first triplet and "max_size + 1" of the preceding range. -mmemset-strategy=strategy The option is similar to -mmemcpy-strategy= except that it is to control "__builtin_memset" expansion. -momit-leaf-frame-pointer Don't keep the frame pointer in a register for leaf functions. This avoids the instructions to save, set up, and restore frame pointers and makes an extra register available in leaf functions. The option -fomit-leaf-frame-pointer removes the frame pointer for leaf functions, which might make debugging harder. -mtls-direct-seg-refs -mno-tls-direct-seg-refs Controls whether TLS variables may be accessed with offsets from the TLS segment register (%gs for 32-bit, %fs for 64-bit), or whether the thread base pointer must be added. Whether or not this is valid depends on the operating system, and whether it maps the segment to cover the entire TLS area. For systems that use the GNU C Library, the default is on. -msse2avx -mno-sse2avx Specify that the assembler should encode SSE instructions with VEX prefix. The option -mavx turns this on by default. -mfentry -mno-fentry If profiling is active (-pg), put the profiling counter call before the prologue. Note: On x86 architectures the attribute "ms_hook_prologue" isn't possible at the moment for -mfentry and -pg. -mrecord-mcount -mno-record-mcount If profiling is active (-pg), generate a __mcount_loc section that contains pointers to each profiling call. This is useful for automatically patching and out calls. -mnop-mcount -mno-nop-mcount If profiling is active (-pg), generate the calls to the profiling functions as NOPs. This is useful when they should be patched in later dynamically. This is likely only useful together with -mrecord-mcount. -minstrument-return=type Instrument function exit in -pg -mfentry instrumented functions with call to specified function. This only instruments true returns ending with ret, but not sibling calls ending with jump. Valid types are none to not instrument, call to generate a call to __return__, or nop5 to generate a 5 byte nop. -mrecord-return -mno-record-return Generate a __return_loc section pointing to all return instrumentation code. -mfentry-name=name Set name of __fentry__ symbol called at function entry for -pg -mfentry functions. -mfentry-section=name Set name of section to record -mrecord-mcount calls (default __mcount_loc). -mskip-rax-setup -mno-skip-rax-setup When generating code for the x86-64 architecture with SSE extensions disabled, -mskip-rax-setup can be used to skip setting up RAX register when there are no variable arguments passed in vector registers. Warning: Since RAX register is used to avoid unnecessarily saving vector registers on stack when passing variable arguments, the impacts of this option are callees may waste some stack space, misbehave or jump to a random location. GCC 4.4 or newer don't have those issues, regardless the RAX register value. -m8bit-idiv -mno-8bit-idiv On some processors, like Intel Atom, 8-bit unsigned integer divide is much faster than 32-bit/64-bit integer divide. This option generates a run-time check. If both dividend and divisor are within range of 0 to 255, 8-bit unsigned integer divide is used instead of 32-bit/64-bit integer divide. -mavx256-split-unaligned-load -mavx256-split-unaligned-store Split 32-byte AVX unaligned load and store. -mstack-protector-guard=guard -mstack-protector-guard-reg=reg -mstack-protector-guard-offset=offset Generate stack protection code using canary at guard. Supported locations are global for global canary or tls for per-thread canary in the TLS block (the default). This option has effect only when -fstack-protector or -fstack-protector-all is specified. With the latter choice the options -mstack-protector-guard-reg=reg and -mstack-protector-guard-offset=offset furthermore specify which segment register (%fs or %gs) to use as base register for reading the canary, and from what offset from that base register. The default for those is as specified in the relevant ABI. -mgeneral-regs-only Generate code that uses only the general-purpose registers. This prevents the compiler from using floating-point, vector, mask and bound registers. -mrelax-cmpxchg-loop When emitting a compare-and-swap loop for __sync Builtins and __atomic Builtins lacking a native instruction, optimize for the highly contended case by issuing an atomic load before the "CMPXCHG" instruction, and using the "PAUSE" instruction to save CPU power when restarting the loop. -mindirect-branch=choice Convert indirect call and jump with choice. The default is keep, which keeps indirect call and jump unmodified. thunk converts indirect call and jump to call and return thunk. thunk-inline converts indirect call and jump to inlined call and return thunk. thunk-extern converts indirect call and jump to external call and return thunk provided in a separate object file. You can control this behavior for a specific function by using the function attribute "indirect_branch". Note that -mcmodel=large is incompatible with -mindirect-branch=thunk and -mindirect-branch=thunk-extern since the thunk function may not be reachable in the large code model. Note that -mindirect-branch=thunk-extern is compatible with -fcf-protection=branch since the external thunk can be made to enable control-flow check. -mfunction-return=choice Convert function return with choice. The default is keep, which keeps function return unmodified. thunk converts function return to call and return thunk. thunk-inline converts function return to inlined call and return thunk. thunk-extern converts function return to external call and return thunk provided in a separate object file. You can control this behavior for a specific function by using the function attribute "function_return". Note that -mindirect-return=thunk-extern is compatible with -fcf-protection=branch since the external thunk can be made to enable control-flow check. Note that -mcmodel=large is incompatible with -mfunction-return=thunk and -mfunction-return=thunk-extern since the thunk function may not be reachable in the large code model. -mindirect-branch-register Force indirect call and jump via register. -mharden-sls=choice Generate code to mitigate against straight line speculation (SLS) with choice. The default is none which disables all SLS hardening. return enables SLS hardening for function returns. indirect-jmp enables SLS hardening for indirect jumps. all enables all SLS hardening. -mindirect-branch-cs-prefix Add CS prefix to call and jmp to indirect thunk with branch target in r8-r15 registers so that the call and jmp instruction length is 6 bytes to allow them to be replaced with lfence; call *%r8-r15 or lfence; jmp *%r8-r15 at run-time. These -m switches are supported in addition to the above on x86-64 processors in 64-bit environments. -m32 -m64 -mx32 -m16 -miamcu Generate code for a 16-bit, 32-bit or 64-bit environment. The -m32 option sets "int", "long", and pointer types to 32 bits, and generates code that runs in 32-bit mode. The -m64 option sets "int" to 32 bits and "long" and pointer types to 64 bits, and generates code for the x86-64 architecture. For Darwin only the -m64 option also turns off the -fno-pic and -mdynamic-no-pic options. The -mx32 option sets "int", "long", and pointer types to 32 bits, and generates code for the x86-64 architecture. The -m16 option is the same as -m32, except for that it outputs the ".code16gcc" assembly directive at the beginning of the assembly output so that the binary can run in 16-bit mode. The -miamcu option generates code which conforms to Intel MCU psABI. It requires the -m32 option to be turned on. -mno-red-zone Do not use a so-called "red zone" for x86-64 code. The red zone is mandated by the x86-64 ABI; it is a 128-byte area beyond the location of the stack pointer that is not modified by signal or interrupt handlers and therefore can be used for temporary data without adjusting the stack pointer. The flag -mno-red-zone disables this red zone. -mcmodel=small Generate code for the small code model: the program and its symbols must be linked in the lower 2 GB of the address space. Pointers are 64 bits. Programs can be statically or dynamically linked. This is the default code model. -mcmodel=kernel Generate code for the kernel code model. The kernel runs in the negative 2 GB of the address space. This model has to be used for Linux kernel code. -mcmodel=medium Generate code for the medium model: the program is linked in the lower 2 GB of the address space. Small symbols are also placed there. Symbols with sizes larger than -mlarge-data-threshold are put into large data or BSS sections and can be located above 2GB. Programs can be statically or dynamically linked. -mcmodel=large Generate code for the large model. This model makes no assumptions about addresses and sizes of sections. -maddress-mode=long Generate code for long address mode. This is only supported for 64-bit and x32 environments. It is the default address mode for 64-bit environments. -maddress-mode=short Generate code for short address mode. This is only supported for 32-bit and x32 environments. It is the default address mode for 32-bit and x32 environments. -mneeded -mno-needed Emit GNU_PROPERTY_X86_ISA_1_NEEDED GNU property for Linux target to indicate the micro-architecture ISA level required to execute the binary. -mno-direct-extern-access Without -fpic nor -fPIC, always use the GOT pointer to access external symbols. With -fpic or -fPIC, treat access to protected symbols as local symbols. The default is -mdirect-extern-access. Warning: shared libraries compiled with -mno-direct-extern-access and executable compiled with -mdirect-extern-access may not be binary compatible if protected symbols are used in shared libraries and executable. -munroll-only-small-loops Controls conservative small loop unrolling. It is default enabled by O2, and unrolls loop with less than 4 insns by 1 time. Explicit -f[no-]unroll-[all-]loops would disable this flag to avoid any unintended unrolling behavior that user does not want. -mlam=choice LAM(linear-address masking) allows special bits in the pointer to be used for metadata. The default is none. With u48, pointer bits in positions 62:48 can be used for metadata; With u57, pointer bits in positions 62:57 can be used for metadata. x86 Windows Options These additional options are available for Microsoft Windows targets: -mconsole This option specifies that a console application is to be generated, by instructing the linker to set the PE header subsystem type required for console applications. This option is available for Cygwin and MinGW targets and is enabled by default on those targets. -mdll This option is available for Cygwin and MinGW targets. It specifies that a DLL---a dynamic link library---is to be generated, enabling the selection of the required runtime startup object and entry point. -mnop-fun-dllimport This option is available for Cygwin and MinGW targets. It specifies that the "dllimport" attribute should be ignored. -mthreads This option is available for MinGW targets. It specifies that MinGW-specific thread support is to be used. -municode This option is available for MinGW-w64 targets. It causes the "UNICODE" preprocessor macro to be predefined, and chooses Unicode- capable runtime startup code. -mwin32 This option is available for Cygwin and MinGW targets. It specifies that the typical Microsoft Windows predefined macros are to be set in the pre-processor, but does not influence the choice of runtime library/startup code. -mwindows This option is available for Cygwin and MinGW targets. It specifies that a GUI application is to be generated by instructing the linker to set the PE header subsystem type appropriately. -fno-set-stack-executable This option is available for MinGW targets. It specifies that the executable flag for the stack used by nested functions isn't set. This is necessary for binaries running in kernel mode of Microsoft Windows, as there the User32 API, which is used to set executable privileges, isn't available. -fwritable-relocated-rdata This option is available for MinGW and Cygwin targets. It specifies that relocated-data in read-only section is put into the ".data" section. This is a necessary for older runtimes not supporting modification of ".rdata" sections for pseudo-relocation. -mpe-aligned-commons This option is available for Cygwin and MinGW targets. It specifies that the GNU extension to the PE file format that permits the correct alignment of COMMON variables should be used when generating code. It is enabled by default if GCC detects that the target assembler found during configuration supports the feature. See also under x86 Options for standard options. Xstormy16 Options These options are defined for Xstormy16: -msim Choose startup files and linker script suitable for the simulator. Xtensa Options These options are supported for Xtensa targets: -mconst16 -mno-const16 Enable or disable use of "CONST16" instructions for loading constant values. The "CONST16" instruction is currently not a standard option from Tensilica. When enabled, "CONST16" instructions are always used in place of the standard "L32R" instructions. The use of "CONST16" is enabled by default only if the "L32R" instruction is not available. -mfused-madd -mno-fused-madd Enable or disable use of fused multiply/add and multiply/subtract instructions in the floating-point option. This has no effect if the floating-point option is not also enabled. Disabling fused multiply/add and multiply/subtract instructions forces the compiler to use separate instructions for the multiply and add/subtract operations. This may be desirable in some cases where strict IEEE 754-compliant results are required: the fused multiply add/subtract instructions do not round the intermediate result, thereby producing results with more bits of precision than specified by the IEEE standard. Disabling fused multiply add/subtract instructions also ensures that the program output is not sensitive to the compiler's ability to combine multiply and add/subtract operations. -mserialize-volatile -mno-serialize-volatile When this option is enabled, GCC inserts "MEMW" instructions before "volatile" memory references to guarantee sequential consistency. The default is -mserialize-volatile. Use -mno-serialize-volatile to omit the "MEMW" instructions. -mforce-no-pic For targets, like GNU/Linux, where all user-mode Xtensa code must be position-independent code (PIC), this option disables PIC for compiling kernel code. -mtext-section-literals -mno-text-section-literals These options control the treatment of literal pools. The default is -mno-text-section-literals, which places literals in a separate section in the output file. This allows the literal pool to be placed in a data RAM/ROM, and it also allows the linker to combine literal pools from separate object files to remove redundant literals and improve code size. With -mtext-section-literals, the literals are interspersed in the text section in order to keep them as close as possible to their references. This may be necessary for large assembly files. Literals for each function are placed right before that function. -mauto-litpools -mno-auto-litpools These options control the treatment of literal pools. The default is -mno-auto-litpools, which places literals in a separate section in the output file unless -mtext-section-literals is used. With -mauto-litpools the literals are interspersed in the text section by the assembler. Compiler does not produce explicit ".literal" directives and loads literals into registers with "MOVI" instructions instead of "L32R" to let the assembler do relaxation and place literals as necessary. This option allows assembler to create several literal pools per function and assemble very big functions, which may not be possible with -mtext-section-literals. -mtarget-align -mno-target-align When this option is enabled, GCC instructs the assembler to automatically align instructions to reduce branch penalties at the expense of some code density. The assembler attempts to widen density instructions to align branch targets and the instructions following call instructions. If there are not enough preceding safe density instructions to align a target, no widening is performed. The default is -mtarget-align. These options do not affect the treatment of auto-aligned instructions like "LOOP", which the assembler always aligns, either by widening density instructions or by inserting NOP instructions. -mlongcalls -mno-longcalls When this option is enabled, GCC instructs the assembler to translate direct calls to indirect calls unless it can determine that the target of a direct call is in the range allowed by the call instruction. This translation typically occurs for calls to functions in other source files. Specifically, the assembler translates a direct "CALL" instruction into an "L32R" followed by a "CALLX" instruction. The default is -mno-longcalls. This option should be used in programs where the call target can potentially be out of range. This option is implemented in the assembler, not the compiler, so the assembly code generated by GCC still shows direct call instructions---look at the disassembled object code to see the actual instructions. Note that the assembler uses an indirect call for every cross-file call, not just those that really are out of range. -mabi=name Generate code for the specified ABI. Permissible values are: call0, windowed. Default ABI is chosen by the Xtensa core configuration. -mabi=call0 When this option is enabled function parameters are passed in registers "a2" through "a7", registers "a12" through "a15" are caller-saved, and register "a15" may be used as a frame pointer. When this version of the ABI is enabled the C preprocessor symbol "__XTENSA_CALL0_ABI__" is defined. -mabi=windowed When this option is enabled function parameters are passed in registers "a10" through "a15", and called function rotates register window by 8 registers on entry so that its arguments are found in registers "a2" through "a7". Register "a7" may be used as a frame pointer. Register window is rotated 8 registers back upon return. When this version of the ABI is enabled the C preprocessor symbol "__XTENSA_WINDOWED_ABI__" is defined. -mextra-l32r-costs=n Specify an extra cost of instruction RAM/ROM access for "L32R" instructions, in clock cycles. This affects, when optimizing for speed, whether loading a constant from literal pool using "L32R" or synthesizing the constant from a small one with a couple of arithmetic instructions. The default value is 0. zSeries Options These are listed under ENVIRONMENT This section describes several environment variables that affect how GCC operates. Some of them work by specifying directories or prefixes to use when searching for various kinds of files. Some are used to specify other aspects of the compilation environment. Note that you can also specify places to search using options such as -B, -I and -L. These take precedence over places specified using environment variables, which in turn take precedence over those specified by the configuration of GCC. LANG LC_CTYPE LC_MESSAGES LC_ALL These environment variables control the way that GCC uses localization information which allows GCC to work with different national conventions. GCC inspects the locale categories LC_CTYPE and LC_MESSAGES if it has been configured to do so. These locale categories can be set to any value supported by your installation. A typical value is en_GB.UTF-8 for English in the United Kingdom encoded in UTF-8. The LC_CTYPE environment variable specifies character classification. GCC uses it to determine the character boundaries in a string; this is needed for some multibyte encodings that contain quote and escape characters that are otherwise interpreted as a string end or escape. The LC_MESSAGES environment variable specifies the language to use in diagnostic messages. If the LC_ALL environment variable is set, it overrides the value of LC_CTYPE and LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES default to the value of the LANG environment variable. If none of these variables are set, GCC defaults to traditional C English behavior. TMPDIR If TMPDIR is set, it specifies the directory to use for temporary files. GCC uses temporary files to hold the output of one stage of compilation which is to be used as input to the next stage: for example, the output of the preprocessor, which is the input to the compiler proper. GCC_COMPARE_DEBUG Setting GCC_COMPARE_DEBUG is nearly equivalent to passing -fcompare-debug to the compiler driver. See the documentation of this option for more details. GCC_EXEC_PREFIX If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the names of the subprograms executed by the compiler. No slash is added when this prefix is combined with the name of a subprogram, but you can specify a prefix that ends with a slash if you wish. If GCC_EXEC_PREFIX is not set, GCC attempts to figure out an appropriate prefix to use based on the pathname it is invoked with. If GCC cannot find the subprogram using the specified prefix, it tries looking in the usual places for the subprogram. The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/ where prefix is the prefix to the installed compiler. In many cases prefix is the value of "prefix" when you ran the configure script. Other prefixes specified with -B take precedence over this prefix. This prefix is also used for finding files such as crt0.o that are used for linking. In addition, the prefix is used in an unusual way in finding the directories to search for header files. For each of the standard directories whose name normally begins with /usr/local/lib/gcc (more precisely, with the value of GCC_INCLUDE_DIR), GCC tries replacing that beginning with the specified prefix to produce an alternate directory name. Thus, with -Bfoo/, GCC searches foo/bar just before it searches the standard directory /usr/local/lib/bar. If a standard directory begins with the configured prefix then the value of prefix is replaced by GCC_EXEC_PREFIX when looking for header files. COMPILER_PATH The value of COMPILER_PATH is a colon-separated list of directories, much like PATH. GCC tries the directories thus specified when searching for subprograms, if it cannot find the subprograms using GCC_EXEC_PREFIX. LIBRARY_PATH The value of LIBRARY_PATH is a colon-separated list of directories, much like PATH. When configured as a native compiler, GCC tries the directories thus specified when searching for special linker files, if it cannot find them using GCC_EXEC_PREFIX. Linking using GCC also uses these directories when searching for ordinary libraries for the -l option (but directories specified with -L come first). LANG This variable is used to pass locale information to the compiler. One way in which this information is used is to determine the character set to be used when character literals, string literals and comments are parsed in C and C++. When the compiler is configured to allow multibyte characters, the following values for LANG are recognized: C-JIS Recognize JIS characters. C-SJIS Recognize SJIS characters. C-EUCJP Recognize EUCJP characters. If LANG is not defined, or if it has some other value, then the compiler uses "mblen" and "mbtowc" as defined by the default locale to recognize and translate multibyte characters. GCC_EXTRA_DIAGNOSTIC_OUTPUT If GCC_EXTRA_DIAGNOSTIC_OUTPUT is set to one of the following values, then additional text will be emitted to stderr when fix-it hints are emitted. -fdiagnostics-parseable-fixits and -fno-diagnostics-parseable-fixits take precedence over this environment variable. fixits-v1 Emit parseable fix-it hints, equivalent to -fdiagnostics-parseable-fixits. In particular, columns are expressed as a count of bytes, starting at byte 1 for the initial column. fixits-v2 As "fixits-v1", but columns are expressed as display columns, as per -fdiagnostics-column-unit=display. Some additional environment variables affect the behavior of the preprocessor. CPATH C_INCLUDE_PATH CPLUS_INCLUDE_PATH OBJC_INCLUDE_PATH Each variable's value is a list of directories separated by a special character, much like PATH, in which to look for header files. The special character, "PATH_SEPARATOR", is target- dependent and determined at GCC build time. For Microsoft Windows- based targets it is a semicolon, and for almost all other targets it is a colon. CPATH specifies a list of directories to be searched as if specified with -I, but after any paths given with -I options on the command line. This environment variable is used regardless of which language is being preprocessed. The remaining environment variables apply only when preprocessing the particular language indicated. Each specifies a list of directories to be searched as if specified with -isystem, but after any paths given with -isystem options on the command line. In all these variables, an empty element instructs the compiler to search its current working directory. Empty elements can appear at the beginning or end of a path. For instance, if the value of CPATH is ":/special/include", that has the same effect as -I. -I/special/include. DEPENDENCIES_OUTPUT If this variable is set, its value specifies how to output dependencies for Make based on the non-system header files processed by the compiler. System header files are ignored in the dependency output. The value of DEPENDENCIES_OUTPUT can be just a file name, in which case the Make rules are written to that file, guessing the target name from the source file name. Or the value can have the form file target, in which case the rules are written to file file using target as the target name. In other words, this environment variable is equivalent to combining the options -MM and -MF, with an optional -MT switch too. SUNPRO_DEPENDENCIES This variable is the same as DEPENDENCIES_OUTPUT (see above), except that system header files are not ignored, so it implies -M rather than -MM. However, the dependence on the main input file is omitted. SOURCE_DATE_EPOCH If this variable is set, its value specifies a UNIX timestamp to be used in replacement of the current date and time in the "__DATE__" and "__TIME__" macros, so that the embedded timestamps become reproducible. The value of SOURCE_DATE_EPOCH must be a UNIX timestamp, defined as the number of seconds (excluding leap seconds) since 01 Jan 1970 00:00:00 represented in ASCII; identical to the output of "date +%s" on GNU/Linux and other systems that support the %s extension in the "date" command. The value should be a known timestamp such as the last modification time of the source or package and it should be set by the build process. BUGS For instructions on reporting bugs, see <https://github.com/Homebrew/homebrew-core/issues>. FOOTNOTES 1. On some systems, gcc -shared needs to build supplementary stub code for constructors to work. On multi-libbed systems, gcc -shared must select the correct support libraries to link against. Failing to supply the correct flags may lead to subtle defects. Supplying them in cases where they are not necessary is innocuous. -shared suppresses the addition of startup code to alter the floating-point environment as done with -ffast-math, -Ofast or -funsafe-math-optimizations on some targets. SEE ALSO gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1), gdb(1) and the Info entries for gcc, cpp, as, ld, binutils and gdb. AUTHOR See the Info entry for gcc, or <https://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for contributors to GCC. COPYRIGHT Copyright (c) 1988-2023 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being "GNU General Public License" and "Funding Free Software", the Front-Cover texts being (a) (see below), and with the Back-Cover Texts being (b) (see below). A copy of the license is included in the gfdl(7) man page. (a) The FSF's Front-Cover Text is: A GNU Manual (b) The FSF's Back-Cover Text is: You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development. gcc-13 2023-07-27 GCC(1)
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pk11importtest
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gpg-card
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The gpg-card is used to administrate smart cards and USB tokens. It provides a superset of features from gpg --card-edit an can be considered a frontend to scdaemon which is a daemon started by gpg-agent to handle smart cards. If gpg-card is invoked without commands an interactive mode is used. If gpg-card is invoked with one or more commands the same commands as available in the interactive mode are run from the command line. These commands need to be delimited with a double-dash. If a double-dash or a shell specific character is required as part of a command the entire command needs to be put in quotes. If one of those commands returns an error the remaining commands are not anymore run unless the command was prefixed with a single dash. A list of commands is available by using the command help and a brief description of each command is printed by using help CMD. See the section COMMANDS for a full description. See the NOTES sections for instructions pertaining to specific cards or card applications. COMMANDS gpg-card understands the following commands, which have options of their own. The pseudo-option ‘--’ can be used to separate command options from arguments; if this pseudo option is used on the command line the entire command with options and arguments must be quoted, so that it is not mixed up with the ‘--’ as used on the command line to separate commands. Note that a short online help is available for all commands by prefixing them with ``help''. Command completion in the interactive mode is also supported. AUTHENTICATE [--setkey] [--raw] [< file]|key] AUTH Authenticate to the card. Perform a mutual authentication either by reading the key from file or by taking it from the command line as key. Without the option --raw the key is expected to be hex encoded. To install a new administration key --setkey is used; this requires a prior authentication with the old key. This is used with PIV cards. CAFPR [--clear] N Change the CA fingerprint number N of an OpenPGP card. N must be in the range 1 to 3. The option --clear clears the specified CA fingerprint N or all of them if N is 0 or not given. FACTORY-RESET Do a complete reset of some OpenPGP and PIV cards. This command deletes all data and keys and resets the PINs to their default. Don't worry, you need to confirm before the command proceeds. FETCH Retrieve a key using the URL data object of an OpenPGP card or if that is missing using the stored fingerprint. FORCESIG Toggle the forcesig flag of an OpenPGP card. GENERATE [--force] [--algo=algo{+algo2}] keyref Create a new key on a card. Use --force to overwrite an existing key. Use "help" for algo to get a list of known algorithms. For OpenPGP cards several algos may be given. Note that the OpenPGP key generation is done interactively unless --algo or keyref are given. KDF-SETUP Prepare the OpenPGP card KDF feature for this card. LANG [--clear] Change the language info for the card. This info can be used by applications for a personalized greeting. Up to 4 two-digit language identifiers can be entered as a preference. The option --clear removes all identifiers. GnuPG does not use this info. LIST [--cards] [--apps] [--info] [--no-key-lookup] [n] [app] L This command reads all information from the current card and display them in a human readable format. The first section shows generic information vaialable for all cards. The next section shows information pertaining to keys which depend on the actual card and application. With n given select and list the n-th card; with app also given select that application. To select an app on the current card use "-" for n. The serial number of the card may be used instead of n. The option --cards lists the serial numbers of available cards. The option --apps lists all card applications. The option --info selects a card and prints its serial number. The option --no-key-lookup suppresses the listing of matching OpenPGP or X.509 keys. LOGIN [--clear] [< file] Set the login data object of OpenPGP cards. If file is given the data is is read from that file. This allows one to store binary data in the login field. The option --clear deletes the login data object. NAME [--clear] Set the name field of an OpenPGP card. With option --clear the stored name is cleared off the card. PASSWD [--reset|--nullpin] [pinref] Change or unblock the PINs. Note that in interactive mode and without a pinref a menu is presented for certain cards." In non-interactive mode and without a pinref a default value i used for these cards. The option --reset is used with TCOS cards to reset the PIN using the PUK or vice versa; the option --nullpin is used for these cards to set the initial PIN. PRIVATEDO [--clear] n [< file] Change the private data object n of an OpenPGP card. n must be in the range 1 to 4. If file is given the data is is read from that file. The option --clear clears the data. QUIT Q Stop processing and terminate gpg-card. READCERT [--openpgp] certref > file Read the certificate for key certref and store it in file. With option --openpgp an OpenPGP keyblock wrapped in a dedicated CMS content type (OID=1.3.6.1.4.1.11591.2.3.1) is expected and extracted to file. Note that for current OpenPGP cards a certificate may only be available at the certref "OPENPGP.3". RESET Send a reset to the card daemon. SALUTATION [--clear] SALUT Change the salutation info for the card. This info can be used by applications for a personalized greeting. The option --clear removes this data object. GnuPG does not use this info. UIF N [on|off|permanent] Change the User Interaction Flag. That flags tells whether the confirmation button of a token shall be used. n must in the range 1 to 3. "permanent" is the same as "on" but the flag can't be changed anmore. UNBLOCK Unblock a PIN using a PUK or Reset Code. Note that OpenPGP cards prior to version 2 can't use this; instead the PASSWD can be used to set a new PIN. URL [--clear] Set the URL data object of an OpenPGP card. That data object can be used by by gpg's --fetch command to retrieve the full public key. The option --clear deletes the content of that data object. VERIFY [chvid] Verify the PIN identified by chvid or the default PIN. WRITECERT certref < file WRITECERT --openpgp certref [< file|fpr] WRITECERT --clear certref Write a certificate to the card under the id certref. The option --clear removes the certificate from the card. The option --openpgp expects an OpenPGP keyblock and stores it encapsulated in a CMS container; the keyblock is taken from file or directly from the OpenPGP key identified by fingerprint fpr. WRITEKEY [--force] keyref keygrip Write a private key object identified by keygrip to the card under the id keyref. Option --force allows overwriting an existing key. CHECKKEYS [--ondisk] [--delete-clear-copy] [--delete-protected-copy] Print a list of keys noticed on all inserted cards. With --ondisk only smartcard keys with a copy on disk are listed. With --delete-clear-copy copies of smartcard keys stored on disk without any protection will be deleted. With --delete-protected-copy password protected copies of smartcard keys stored on disk will be deleted. This command creates missing shadow keys. The delete options print the status of the keys before they are deleted. The format of the output is: Serial number A hex-string with the serial number of the card. Type This gives the type of the card's application. For example "OpenPGP" or "PIV". Keygrip A hex-string identifying a key. Keyref The application slot where the key is stored on the card. For example "OpenPGP.1" Status The status of the key. The most common value is "shadowed" for a key where only the public key along with the card's serial number is stored on the disk. The value "clear" indicates that a copy of the card's key is stored unprotected on disk. The value "protected" indicated that a copy of the car's key is stored on disk but is protected by a password. The value "error" may also be shown if there was a problem reading information from the card. YUBIKEY cmd args Various commands pertaining to Yubikey tokens with cmd being: LIST List supported and enabled Yubikey applications. ENABLE usb|nfc|all [otp|u2f|opgp|piv|oath|fido2|all] DISABLE Enable or disable the specified or all applications on the given interface. NOTES (OPENPGP) The support for OpenPGP cards in gpg-card is not yet complete. For missing features, please continue to use gpg --card-edit. NOTES (PIV) GnuPG has support for PIV cards (``Personal Identity Verification'' as specified by NIST Special Publication 800-73-4). This section describes how to initialize (personalize) a fresh Yubikey token featuring the PIV application (requires Yubikey-5). We assume that the credentials have not yet been changed and thus are: Authentication key This is a 24 byte key described by the hex string 010203040506070801020304050607080102030405060708. PIV Application PIN This is the string 123456. PIN Unblocking Key This is the string 12345678. See the example section on how to change these defaults. For production use it is important to use secure values for them. Note that the Authentication Key is not queried via the usual Pinentry dialog but needs to be entered manually or read from a file. The use of a dedicated machine to personalize tokens is strongly suggested. To see what is on the card, the command list can be given. We will use the interactive mode in the following (the string gpg/card> is the prompt). An example output for a fresh card is: gpg/card> list Reader ...........: 1050:0407:X:0 Card type ........: yubikey Card firmware ....: 5.1.2 Serial number ....: D2760001240102010006090746250000 Application type .: OpenPGP Version ..........: 2.1 [...] It can be seen by the ``Application type'' line that GnuPG selected the OpenPGP application of the Yubikey. This is because GnuPG assigns the highest priority to the OpenPGP application. To use the PIV application of the Yubikey several methods can be used: With a Yubikey 5 or later the OpenPGP application on the Yubikey can be disabled: gpg/card> yubikey disable all opgp gpg/card> yubikey list Application USB NFC ----------------------- OTP yes yes U2F yes yes OPGP no no PIV yes no OATH yes yes FIDO2 yes yes gpg/card> reset The reset is required so that the GnuPG system rereads the card. Note that disabled applications keep all their data and can at any time be re-enabled (use ‘help yubikey’). Another option, which works for all Yubikey versions, is to disable the support for OpenPGP cards in scdaemon. This is done by adding the line disable-application openpgp to ‘~/.gnupg/scdaemon.conf’ and by restarting scdaemon, either by killing the process or by using ‘gpgconf --kill scdaemon’. Finally the default order in which card applications are tried by scdaemon can be changed. For example to prefer PIV over OpenPGP it is sufficient to add application-priority piv to ‘~/.gnupg/scdaemon.conf’ and to restart scdaemon. This has an effect only on tokens which support both, PIV and OpenPGP, but does not hamper the use of OpenPGP only tokens. With one of these methods employed the list command of gpg-card shows this: gpg/card> list Reader ...........: 1050:0407:X:0 Card type ........: yubikey Card firmware ....: 5.1.2 Serial number ....: FF020001008A77C1 Application type .: PIV Version ..........: 1.0 Displayed s/n ....: yk-9074625 PIN usage policy .: app-pin PIN retry counter : - 3 - PIV authentication: [none] keyref .....: PIV.9A Card authenticat. : [none] keyref .....: PIV.9E Digital signature : [none] keyref .....: PIV.9C Key management ...: [none] keyref .....: PIV.9D In case several tokens are plugged into the computer, gpg-card will show only one. To show another token the number of the token (0, 1, 2, ...) can be given as an argument to the list command. The command ‘list --cards’ prints a list of all inserted tokens. Note that the ``Displayed s/n'' is printed on the token and also shown in Pinentry prompts asking for the PIN. The four standard key slots are always shown, if other key slots are initialized they are shown as well. The PIV authentication key (internal reference PIV.9A) is used to authenticate the card and the card holder. The use of the associated private key is protected by the Application PIN which needs to be provided once and the key can the be used until the card is reset or removed from the reader or USB port. GnuPG uses this key with its Secure Shell support. The Card authentication key (PIV.9E) is also known as the CAK and used to support physical access applications. The private key is not protected by a PIN and can thus immediately be used. The Digital signature key (PIV.9C) is used to digitally sign documents. The use of the associated private key is protected by the Application PIN which needs to be provided for each signing operation. The Key management key (PIV.9D) is used for encryption. The use of the associated private key is protected by the Application PIN which needs to be provided only once so that decryption operations can then be done until the card is reset or removed from the reader or USB port. We now generate three of the four keys. Note that GnuPG does currently not use the the Card authentication key; however, that key is mandatory by the PIV standard and thus we create it too. Key generation requires that we authenticate to the card. This can be done either on the command line (which would reveal the key): gpg/card> auth 010203040506070801020304050607080102030405060708 or by reading the key from a file. That file needs to consist of one LF terminated line with the hex encoded key (as above): gpg/card> auth < myauth.key As usual ‘help auth’ gives help for this command. An error message is printed if a non-matching key is used. The authentication is valid until a reset of the card or until the card is removed from the reader or the USB port. Note that that in non-interactive mode the ‘<’ needs to be quoted so that the shell does not interpret it as a its own redirection symbol. Here are the actual commands to generate the keys: gpg/card> generate --algo=nistp384 PIV.9A PIV card no. yk-9074625 detected gpg/card> generate --algo=nistp256 PIV.9E PIV card no. yk-9074625 detected gpg/card> generate --algo=rsa2048 PIV.9C PIV card no. yk-9074625 detected If a key has already been created for one of the slots an error will be printed; to create a new key anyway the option ‘--force’ can be used. Note that only the private and public keys have been created but no certificates are stored in the key slots. In fact, GnuPG uses its own non-standard method to store just the public key in place of the the certificate. Other application will not be able to make use these keys until gpgsm or another tool has been used to create and store the respective certificates. Let us see what the list command now shows: gpg/card> list Reader ...........: 1050:0407:X:0 Card type ........: yubikey Card firmware ....: 5.1.2 Serial number ....: FF020001008A77C1 Application type .: PIV Version ..........: 1.0 Displayed s/n ....: yk-9074625 PIN usage policy .: app-pin PIN retry counter : - 3 - PIV authentication: 213D1825FDE0F8240CB4E4229F01AF90AC658C2E keyref .....: PIV.9A (auth) algorithm ..: nistp384 Card authenticat. : 7A53E6CFFE7220A0E646B4632EE29E5A7104499C keyref .....: PIV.9E (auth) algorithm ..: nistp256 Digital signature : 32A6C6FAFCB8421878608AAB452D5470DD3223ED keyref .....: PIV.9C (sign,cert) algorithm ..: rsa2048 Key management ...: [none] keyref .....: PIV.9D The primary information for each key is the keygrip, a 40 byte hex- string identifying the key. This keygrip is a unique identifier for the specific parameters of a key. It is used by gpg-agent and other parts of GnuPG to associate a private key to its protocol specific certificate format (X.509, OpenPGP, or SecureShell). Below the keygrip the key reference along with the key usage capabilities are show. Finally the algorithm is printed in the format used by {gpg}. At that point no other information is shown because for these new keys gpg won't be able to find matching certificates. Although we could have created the Key management key also with the generate command, we will create that key off-card so that a backup exists. To accomplish this a key needs to be created with either gpg or gpgsm or imported in one of these tools. In our example we create a self-signed X.509 certificate (exit the gpg-card tool, first): $ gpgsm --gen-key -o encr.crt (1) RSA (2) Existing key (3) Existing key from card Your selection? 1 What keysize do you want? (3072) 2048 Requested keysize is 2048 bits Possible actions for a RSA key: (1) sign, encrypt (2) sign (3) encrypt Your selection? 3 Enter the X.509 subject name: CN=Encryption key for yk-9074625,O=example,C=DE Enter email addresses (end with an empty line): > otto@example.net > Enter DNS names (optional; end with an empty line): > Enter URIs (optional; end with an empty line): > Create self-signed certificate? (y/N) y These parameters are used: Key-Type: RSA Key-Length: 2048 Key-Usage: encrypt Serial: random Name-DN: CN=Encryption key for yk-9074625,O=example,C=DE Name-Email: otto@example.net Proceed with creation? (y/N) Now creating self-signed certificate. This may take a while ... gpgsm: about to sign the certificate for key: &34798AAFE0A7565088101CC4AE31C5C8C74461CB gpgsm: certificate created Ready. $ gpgsm --import encr.crt gpgsm: certificate imported gpgsm: total number processed: 1 gpgsm: imported: 1 Note the last step which imported the created certificate. If you you instead created a certificate signing request (CSR) instead of a self- signed certificate and sent this off to a CA you would do the same import step with the certificate received from the CA. Take note of the keygrip (prefixed with an ampersand) as shown during the certificate creation or listed it again using ‘gpgsm --with-keygrip -k otto@example.net’. Now to move the key and certificate to the card start gpg-card again and enter: gpg/card> writekey PIV.9D 34798AAFE0A7565088101CC4AE31C5C8C74461CB gpg/card> writecert PIV.9D < encr.crt If you entered a passphrase to protect the private key, you will be asked for it via the Pinentry prompt. On success the key and the certificate has been written to the card and a list command shows: [...] Key management ...: 34798AAFE0A7565088101CC4AE31C5C8C74461CB keyref .....: PIV.9D (encr) algorithm ..: rsa2048 used for ...: X.509 user id ..: CN=Encryption key for yk-9074625,O=example,C=DE user id ..: <otto@example.net> In case the same key (identified by the keygrip) has been used for several certificates you will see several ``used for'' parts. With this the encryption key is now fully functional and can be used to decrypt messages encrypted to this certificate. Take care: the original key is still stored on-disk and should be moved to a backup medium. This can simply be done by copying the file ‘34798AAFE0A7565088101CC4AE31C5C8C74461CB.key’ from the directory ‘~/.gnupg/private-keys-v1.d/’ to the backup medium and deleting the file at its original place. The final example is to create a self-signed certificate for digital signatures. Leave gpg-card using quit or by pressing Control-D and use gpgsm: $ gpgsm --learn $ gpgsm --gen-key -o sign.crt Please select what kind of key you want: (1) RSA (2) Existing key (3) Existing key from card Your selection? 3 Serial number of the card: FF020001008A77C1 Available keys: (1) 213D1825FDE0F8240CB4E4229F01AF90AC658C2E PIV.9A nistp384 (2) 7A53E6CFFE7220A0E646B4632EE29E5A7104499C PIV.9E nistp256 (3) 32A6C6FAFCB8421878608AAB452D5470DD3223ED PIV.9C rsa2048 (4) 34798AAFE0A7565088101CC4AE31C5C8C74461CB PIV.9D rsa2048 Your selection? 3 Possible actions for a RSA key: (1) sign, encrypt (2) sign (3) encrypt Your selection? 2 Enter the X.509 subject name: CN=Signing key for yk-9074625,O=example,C=DE Enter email addresses (end with an empty line): > otto@example.net > Enter DNS names (optional; end with an empty line): > Enter URIs (optional; end with an empty line): > Create self-signed certificate? (y/N) These parameters are used: Key-Type: card:PIV.9C Key-Length: 1024 Key-Usage: sign Serial: random Name-DN: CN=Signing key for yk-9074625,O=example,C=DE Name-Email: otto@example.net Proceed with creation? (y/N) y Now creating self-signed certificate. This may take a while ... gpgsm: about to sign the certificate for key: &32A6C6FAFCB8421878608AAB452D5470DD3223ED gpgsm: certificate created Ready. $ gpgsm --import sign.crt gpgsm: certificate imported gpgsm: total number processed: 1 gpgsm: imported: 1 The use of ‘gpgsm --learn’ is currently necessary so that gpg-agent knows what keys are available on the card. The need for this command will eventually be removed. The remaining commands are similar to the creation of an on-disk key. However, here we select the ‘Digital signature’ key. During the creation process you will be asked for the Application PIN of the card. The final step is to write the certificate to the card using gpg-card: gpg/card> writecert PIV.9C < sign.crt By running list again we will see the fully initialized card: Reader ...........: 1050:0407:X:0 Card type ........: yubikey Card firmware ....: 5.1.2 Serial number ....: FF020001008A77C1 Application type .: PIV Version ..........: 1.0 Displayed s/n ....: yk-9074625 PIN usage policy .: app-pin PIN retry counter : - [verified] - PIV authentication: 213D1825FDE0F8240CB4E4229F01AF90AC658C2E keyref .....: PIV.9A (auth) algorithm ..: nistp384 Card authenticat. : 7A53E6CFFE7220A0E646B4632EE29E5A7104499C keyref .....: PIV.9E (auth) algorithm ..: nistp256 Digital signature : 32A6C6FAFCB8421878608AAB452D5470DD3223ED keyref .....: PIV.9C (sign,cert) algorithm ..: rsa2048 used for ...: X.509 user id ..: CN=Signing key for yk-9074625,O=example,C=DE user id ..: <otto@example.net> Key management ...: 34798AAFE0A7565088101CC4AE31C5C8C74461CB keyref .....: PIV.9D (encr) algorithm ..: rsa2048 used for ...: X.509 user id ..: CN=Encryption key for yk-9074625,O=example,C=DE user id ..: <otto@example.net> It is now possible to sign and to encrypt with this card using gpgsm and to use the ‘PIV authentication’ key with ssh: $ ssh-add -l 384 SHA256:0qnJ0Y0ehWxKcx2frLfEljf6GCdlO55OZed5HqGHsaU cardno:yk-9074625 (ECDSA) As usual use ssh-add with the uppercase ‘-L’ to list the public ssh key. To use the certificates with Thunderbird or Mozilla, please consult the Scute manual for details. If you want to use the same PIV keys also for OpenPGP (for example on a Yubikey to avoid switching between OpenPGP and PIV), this is also possible: $ gpgsm --learn $ gpg --full-gen-key Please select what kind of key you want: (1) RSA and RSA (default) (2) DSA and Elgamal (3) DSA (sign only) (4) RSA (sign only) (14) Existing key from card Your selection? 14 Serial number of the card: FF020001008A77C1 Available keys: (1) 213D1825FDE0F8240CB4E4229F01AF90AC658C2E PIV.9A nistp384 (auth) (2) 7A53E6CFFE7220A0E646B4632EE29E5A7104499C PIV.9E nistp256 (auth) (3) 32A6C6FAFCB8421878608AAB452D5470DD3223ED PIV.9C rsa2048 (cert,sign) (4) 34798AAFE0A7565088101CC4AE31C5C8C74461CB PIV.9D rsa2048 (encr) Your selection? 3 Please specify how long the key should be valid. 0 = key does not expire <n> = key expires in n days <n>w = key expires in n weeks <n>m = key expires in n months <n>y = key expires in n years Key is valid for? (0) Key does not expire at all Is this correct? (y/N) y GnuPG needs to construct a user ID to identify your key. Real name: Email address: otto@example.net Comment: You selected this USER-ID: "otto@example.net" Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? o gpg: key C3AFA9ED971BB365 marked as ultimately trusted gpg: revocation certificate stored as '[...]D971BB365.rev' public and secret key created and signed. Note that this key cannot be used for encryption. You may want to use the command "--edit-key" to generate a subkey for this purpose. pub rsa2048 2019-04-04 [SC] 7F899AE2FB73159DD68A1B20C3AFA9ED971BB365 uid otto@example.net Note that you will be asked two times to enter the PIN of your PIV card. If you run gpg in --expert mode you will also ge given the option to change the usage flags of the key. The next typescript shows how to add the encryption subkey: $ gpg --edit-key 7F899AE2FB73159DD68A1B20C3AFA9ED971BB365 Secret key is available. sec rsa2048/C3AFA9ED971BB365 created: 2019-04-04 expires: never usage: SC card-no: FF020001008A77C1 trust: ultimate validity: ultimate [ultimate] (1). otto@example.net gpg> addkey Secret parts of primary key are stored on-card. Please select what kind of key you want: (3) DSA (sign only) (4) RSA (sign only) (5) Elgamal (encrypt only) (6) RSA (encrypt only) (14) Existing key from card Your selection? 14 Serial number of the card: FF020001008A77C1 Available keys: (1) 213D1825FDE0F8240CB4E4229F01AF90AC658C2E PIV.9A nistp384 (auth) (2) 7A53E6CFFE7220A0E646B4632EE29E5A7104499C PIV.9E nistp256 (auth) (3) 32A6C6FAFCB8421878608AAB452D5470DD3223ED PIV.9C rsa2048 (cert,sign) (4) 34798AAFE0A7565088101CC4AE31C5C8C74461CB PIV.9D rsa2048 (encr) Your selection? 4 Please specify how long the key should be valid. 0 = key does not expire <n> = key expires in n days <n>w = key expires in n weeks <n>m = key expires in n months <n>y = key expires in n years Key is valid for? (0) Key does not expire at all Is this correct? (y/N) y Really create? (y/N) y sec rsa2048/C3AFA9ED971BB365 created: 2019-04-04 expires: never usage: SC card-no: FF020001008A77C1 trust: ultimate validity: ultimate ssb rsa2048/7067860A98FCE6E1 created: 2019-04-04 expires: never usage: E card-no: FF020001008A77C1 [ultimate] (1). otto@example.net gpg> save Now you can use your PIV card also with gpg.
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gpg-card - Administrate Smart Cards
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gpg-card [options] gpg-card [options] command { -- command }
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gpg-card understands these options: --with-colons This option has currently no effect. --status-fd n Write special status strings to the file descriptor n. This program returns only the status messages SUCCESS or FAILURE which are helpful when the caller uses a double fork approach and can't easily get the return code of the process. --verbose Enable extra informational output. --quiet Disable almost all informational output. --version Print version of the program and exit. --help Display a brief help page and exit. --no-autostart Do not start the gpg-agent if it has not yet been started and its service is required. This option is mostly useful on machines where the connection to gpg-agent has been redirected to another machines. --no-history In interactive mode the command line history is usually saved and restored to and from a file below the GnuPG home directory. This option inhibits the use of that file. --agent-program file Specify the agent program to be started if none is running. The default value is determined by running gpgconf with the option --list-dirs. --gpg-program file Specify a non-default gpg binary to be used by certain commands. --gpgsm-program file Specify a non-default gpgsm binary to be used by certain commands. --chuid uid Change the current user to uid which may either be a number or a name. This can be used from the root account to run gpg-card for another user. If uid is not the current UID a standard PATH is set and the envvar GNUPGHOME is unset. To override the latter the option --homedir can be used. This option has only an effect when used on the command line. This option has currently no effect at all on Windows. SEE ALSO scdaemon(1) GnuPG 2.4.5 2024-03-04 GPG-CARD(1)
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gtsort
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Write totally ordered list consistent with the partial ordering in FILE. With no FILE, or when FILE is -, read standard input. --help display this help and exit --version output version information and exit AUTHOR Written by Mark Kettenis. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO Full documentation <https://www.gnu.org/software/coreutils/tsort> or available locally via: info '(coreutils) tsort invocation' GNU coreutils 9.3 April 2023 TSORT(1)
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tsort - perform topological sort
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tsort [OPTION] [FILE]
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ffhash
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pcre2grep
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pcre2grep searches files for character patterns, in the same way as other grep commands do, but it uses the PCRE2 regular expression library to support patterns that are compatible with the regular expressions of Perl 5. See pcre2syntax(3) for a quick-reference summary of pattern syntax, or pcre2pattern(3) for a full description of the syntax and semantics of the regular expressions that PCRE2 supports. Patterns, whether supplied on the command line or in a separate file, are given without delimiters. For example: pcre2grep Thursday /etc/motd If you attempt to use delimiters (for example, by surrounding a pattern with slashes, as is common in Perl scripts), they are interpreted as part of the pattern. Quotes can of course be used to delimit patterns on the command line because they are interpreted by the shell, and indeed quotes are required if a pattern contains white space or shell metacharacters. The first argument that follows any option settings is treated as the single pattern to be matched when neither -e nor -f is present. Conversely, when one or both of these options are used to specify patterns, all arguments are treated as path names. At least one of -e, -f, or an argument pattern must be provided. If no files are specified, pcre2grep reads the standard input. The standard input can also be referenced by a name consisting of a single hyphen. For example: pcre2grep some-pattern file1 - file3 By default, input files are searched line by line, so pattern assertions about the beginning and end of a subject string (^, $, \A, \Z, and \z) match at the beginning and end of each line. When a line matches a pattern, it is copied to the standard output, and if there is more than one file, the file name is output at the start of each line, followed by a colon. However, there are options that can change how pcre2grep behaves. For example, the -M option makes it possible to search for strings that span line boundaries. What defines a line boundary is controlled by the -N (--newline) option. The -h and -H options control whether or not file names are shown, and the -Z option changes the file name terminator to a zero byte. The amount of memory used for buffering files that are being scanned is controlled by parameters that can be set by the --buffer-size and --max-buffer-size options. The first of these sets the size of buffer that is obtained at the start of processing. If an input file contains very long lines, a larger buffer may be needed; this is handled by automatically extending the buffer, up to the limit specified by --max- buffer-size. The default values for these parameters can be set when pcre2grep is built; if nothing is specified, the defaults are set to 20KiB and 1MiB respectively. An error occurs if a line is too long and the buffer can no longer be expanded. The block of memory that is actually used is three times the "buffer size", to allow for buffering "before" and "after" lines. If the buffer size is too small, fewer than requested "before" and "after" lines may be output. When matching with a multiline pattern, the size of the buffer must be at least half of the maximum match expected or the pattern might fail to match. Patterns can be no longer than 8KiB or BUFSIZ bytes, whichever is the greater. BUFSIZ is defined in <stdio.h>. When there is more than one pattern (specified by the use of -e and/or -f), each pattern is applied to each line in the order in which they are defined, except that all the -e patterns are tried before the -f patterns. By default, as soon as one pattern matches a line, no further patterns are considered. However, if --colour (or --color) is used to colour the matching substrings, or if --only-matching, --file-offsets, --line- offsets, or --output is used to output only the part of the line that matched (either shown literally, or as an offset), the behaviour is different. In this situation, all the patterns are applied to the line. If there is more than one match, the one that begins nearest to the start of the subject is processed; if there is more than one match at that position, the one with the longest matching substring is processed; if the matching substrings are equal, the first match found is processed. Scanning with all the patterns resumes immediately following the match, so that later matches on the same line can be found. Note, however, that an overlapping match that starts in the middle of another match will not be processed. The above behaviour was changed at release 10.41 to be more compatible with GNU grep. In earlier releases, pcre2grep did not recognize matches from later patterns that were earlier in the subject. Patterns that can match an empty string are accepted, but empty string matches are never recognized. An example is the pattern "(super)?(man)?", in which all components are optional. This pattern finds all occurrences of both "super" and "man"; the output differs from matching with "super|man" when only the matching substrings are being shown. If the LC_ALL or LC_CTYPE environment variable is set, pcre2grep uses the value to set a locale when calling the PCRE2 library. The --locale option can be used to override this. SUPPORT FOR COMPRESSED FILES Compile-time options for pcre2grep can set it up to use libz or libbz2 for reading compressed files whose names end in .gz or .bz2, respectively. You can find out whether your pcre2grep binary has support for one or both of these file types by running it with the --help option. If the appropriate support is not present, all files are treated as plain text. The standard input is always so treated. If a file with a .gz or .bz2 extension is not in fact compressed, it is read as a plain text file. When input is from a compressed .gz or .bz2 file, the --line-buffered option is ignored. BINARY FILES By default, a file that contains a binary zero byte within the first 1024 bytes is identified as a binary file, and is processed specially. However, if the newline type is specified as NUL, that is, the line terminator is a binary zero, the test for a binary file is not applied. See the --binary-files option for a means of changing the way binary files are handled. BINARY ZEROS IN PATTERNS Patterns passed from the command line are strings that are terminated by a binary zero, so cannot contain internal zeros. However, patterns that are read from a file via the -f option may contain binary zeros.
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pcre2grep - a grep with Perl-compatible regular expressions.
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pcre2grep [options] [long options] [pattern] [path1 path2 ...]
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The order in which some of the options appear can affect the output. For example, both the -H and -l options affect the printing of file names. Whichever comes later in the command line will be the one that takes effect. Similarly, except where noted below, if an option is given twice, the later setting is used. Numerical values for options may be followed by K or M, to signify multiplication by 1024 or 1024*1024 respectively. -- This terminates the list of options. It is useful if the next item on the command line starts with a hyphen but is not an option. This allows for the processing of patterns and file names that start with hyphens. -A number, --after-context=number Output up to number lines of context after each matching line. Fewer lines are output if the next match or the end of the file is reached, or if the processing buffer size has been set too small. If file names and/or line numbers are being output, a hyphen separator is used instead of a colon for the context lines (the -Z option can be used to change the file name terminator to a zero byte). A line containing "--" is output between each group of lines, unless they are in fact contiguous in the input file. The value of number is expected to be relatively small. When -c is used, -A is ignored. -a, --text Treat binary files as text. This is equivalent to --binary- files=text. --allow-lookaround-bsk PCRE2 now forbids the use of \K in lookarounds by default, in line with Perl. This option causes pcre2grep to set the PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK option, which enables this somewhat dangerous usage. -B number, --before-context=number Output up to number lines of context before each matching line. Fewer lines are output if the previous match or the start of the file is within number lines, or if the processing buffer size has been set too small. If file names and/or line numbers are being output, a hyphen separator is used instead of a colon for the context lines (the -Z option can be used to change the file name terminator to a zero byte). A line containing "--" is output between each group of lines, unless they are in fact contiguous in the input file. The value of number is expected to be relatively small. When -c is used, -B is ignored. --binary-files=word Specify how binary files are to be processed. If the word is "binary" (the default), pattern matching is performed on binary files, but the only output is "Binary file <name> matches" when a match succeeds. If the word is "text", which is equivalent to the -a or --text option, binary files are processed in the same way as any other file. In this case, when a match succeeds, the output may be binary garbage, which can have nasty effects if sent to a terminal. If the word is "without-match", which is equivalent to the -I option, binary files are not processed at all; they are assumed not to be of interest and are skipped without causing any output or affecting the return code. --buffer-size=number Set the parameter that controls how much memory is obtained at the start of processing for buffering files that are being scanned. See also --max-buffer-size below. -C number, --context=number Output number lines of context both before and after each matching line. This is equivalent to setting both -A and -B to the same value. -c, --count Do not output lines from the files that are being scanned; instead output the number of lines that would have been shown, either because they matched, or, if -v is set, because they failed to match. By default, this count is exactly the same as the number of lines that would have been output, but if the -M (multiline) option is used (without -v), there may be more suppressed lines than the count (that is, the number of matches). If no lines are selected, the number zero is output. If several files are being scanned, a count is output for each of them and the -t option can be used to cause a total to be output at the end. However, if the --files-with-matches option is also used, only those files whose counts are greater than zero are listed. When -c is used, the -A, -B, and -C options are ignored. --colour, --color If this option is given without any data, it is equivalent to "--colour=auto". If data is required, it must be given in the same shell item, separated by an equals sign. --colour=value, --color=value This option specifies under what circumstances the parts of a line that matched a pattern should be coloured in the output. It is ignored if --file-offsets, --line-offsets, or --output is set. By default, output is not coloured. The value for the --colour option (which is optional, see above) may be "never", "always", or "auto". In the latter case, colouring happens only if the standard output is connected to a terminal. More resources are used when colouring is enabled, because pcre2grep has to search for all possible matches in a line, not just one, in order to colour them all. The colour that is used can be specified by setting one of the environment variables PCRE2GREP_COLOUR, PCRE2GREP_COLOR, PCREGREP_COLOUR, or PCREGREP_COLOR, which are checked in that order. If none of these are set, pcre2grep looks for GREP_COLORS or GREP_COLOR (in that order). The value of the variable should be a string of two numbers, separated by a semicolon, except in the case of GREP_COLORS, which must start with "ms=" or "mt=" followed by two semicolon-separated colours, terminated by the end of the string or by a colon. If GREP_COLORS does not start with "ms=" or "mt=" it is ignored, and GREP_COLOR is checked. If the string obtained from one of the above variables contains any characters other than semicolon or digits, the setting is ignored and the default colour is used. The string is copied directly into the control string for setting colour on a terminal, so it is your responsibility to ensure that the values make sense. If no relevant environment variable is set, the default is "1;31", which gives red. -D action, --devices=action If an input path is not a regular file or a directory, "action" specifies how it is to be processed. Valid values are "read" (the default) or "skip" (silently skip the path). -d action, --directories=action If an input path is a directory, "action" specifies how it is to be processed. Valid values are "read" (the default in non-Windows environments, for compatibility with GNU grep), "recurse" (equivalent to the -r option), or "skip" (silently skip the path, the default in Windows environments). In the "read" case, directories are read as if they were ordinary files. In some operating systems the effect of reading a directory like this is an immediate end-of-file; in others it may provoke an error. --depth-limit=number See --match-limit below. -E, --case-restrict When case distinctions are being ignored in Unicode mode, two ASCII letters (K and S) will by default match Unicode characters U+212A (Kelvin sign) and U+017F (long S) respectively, as well as their lower case ASCII counterparts. When this option is set, case equivalences are restricted such that no ASCII character matches a non-ASCII character, and vice versa. -e pattern, --regex=pattern, --regexp=pattern Specify a pattern to be matched. This option can be used multiple times in order to specify several patterns. It can also be used as a way of specifying a single pattern that starts with a hyphen. When -e is used, no argument pattern is taken from the command line; all arguments are treated as file names. There is no limit to the number of patterns. They are applied to each line in the order in which they are defined. If -f is used with -e, the command line patterns are matched first, followed by the patterns from the file(s), independent of the order in which these options are specified. --exclude=pattern Files (but not directories) whose names match the pattern are skipped without being processed. This applies to all files, whether listed on the command line, obtained from --file- list, or by scanning a directory. The pattern is a PCRE2 regular expression, and is matched against the final component of the file name, not the entire path. The -F, -w, and -x options do not apply to this pattern. The option may be given any number of times in order to specify multiple patterns. If a file name matches both an --include and an --exclude pattern, it is excluded. There is no short form for this option. --exclude-from=filename Treat each non-empty line of the file as the data for an --exclude option. What constitutes a newline when reading the file is the operating system's default. The --newline option has no effect on this option. This option may be given more than once in order to specify a number of files to read. --exclude-dir=pattern Directories whose names match the pattern are skipped without being processed, whatever the setting of the --recursive option. This applies to all directories, whether listed on the command line, obtained from --file-list, or by scanning a parent directory. The pattern is a PCRE2 regular expression, and is matched against the final component of the directory name, not the entire path. The -F, -w, and -x options do not apply to this pattern. The option may be given any number of times in order to specify more than one pattern. If a directory matches both --include-dir and --exclude-dir, it is excluded. There is no short form for this option. -F, --fixed-strings Interpret each data-matching pattern as a list of fixed strings, separated by newlines, instead of as a regular expression. What constitutes a newline for this purpose is controlled by the --newline option. The -w (match as a word) and -x (match whole line) options can be used with -F. They apply to each of the fixed strings. A line is selected if any of the fixed strings are found in it (subject to -w or -x, if present). This option applies only to the patterns that are matched against the contents of files; it does not apply to patterns specified by any of the --include or --exclude options. -f filename, --file=filename Read patterns from the file, one per line. As is the case with patterns on the command line, no delimiters should be used. What constitutes a newline when reading the file is the operating system's default interpretation of \n. The --newline option has no effect on this option. Trailing white space is removed from each line, and blank lines are ignored. An empty file contains no patterns and therefore matches nothing. Patterns read from a file in this way may contain binary zeros, which are treated as ordinary data characters. If this option is given more than once, all the specified files are read. A data line is output if any of the patterns match it. A file name can be given as "-" to refer to the standard input. When -f is used, patterns specified on the command line using -e may also be present; they are matched before the file's patterns. However, no pattern is taken from the command line; all arguments are treated as the names of paths to be searched. --file-list=filename Read a list of files and/or directories that are to be scanned from the given file, one per line. What constitutes a newline when reading the file is the operating system's default. Trailing white space is removed from each line, and blank lines are ignored. These paths are processed before any that are listed on the command line. The file name can be given as "-" to refer to the standard input. If --file and --file-list are both specified as "-", patterns are read first. This is useful only when the standard input is a terminal, from which further lines (the list of files) can be read after an end-of-file indication. If this option is given more than once, all the specified files are read. --file-offsets Instead of showing lines or parts of lines that match, show each match as an offset from the start of the file and a length, separated by a comma. In this mode, --colour has no effect, and no context is shown. That is, the -A, -B, and -C options are ignored. If there is more than one match in a line, each of them is shown separately. This option is mutually exclusive with --output, --line-offsets, and --only- matching. --group-separator=text Output this text string instead of two hyphens between groups of lines when -A, -B, or -C is in use. See also --no-group- separator. -H, --with-filename Force the inclusion of the file name at the start of output lines when searching a single file. The file name is not normally shown in this case. By default, for matching lines, the file name is followed by a colon; for context lines, a hyphen separator is used. The -Z option can be used to change the terminator to a zero byte. If a line number is also being output, it follows the file name. When the -M option causes a pattern to match more than one line, only the first is preceded by the file name. This option overrides any previous -h, -l, or -L options. -h, --no-filename Suppress the output file names when searching multiple files. File names are normally shown when multiple files are searched. By default, for matching lines, the file name is followed by a colon; for context lines, a hyphen separator is used. The -Z option can be used to change the terminator to a zero byte. If a line number is also being output, it follows the file name. This option overrides any previous -H, -L, or -l options. --heap-limit=number See --match-limit below. --help Output a help message, giving brief details of the command options and file type support, and then exit. Anything else on the command line is ignored. -I Ignore binary files. This is equivalent to --binary- files=without-match. -i, --ignore-case Ignore upper/lower case distinctions when pattern matching. This applies when matching path names for inclusion or exclusion as well as when matching lines in files. --include=pattern If any --include patterns are specified, the only files that are processed are those whose names match one of the patterns and do not match an --exclude pattern. This option does not affect directories, but it applies to all files, whether listed on the command line, obtained from --file-list, or by scanning a directory. The pattern is a PCRE2 regular expression, and is matched against the final component of the file name, not the entire path. The -F, -w, and -x options do not apply to this pattern. The option may be given any number of times. If a file name matches both an --include and an --exclude pattern, it is excluded. There is no short form for this option. --include-from=filename Treat each non-empty line of the file as the data for an --include option. What constitutes a newline for this purpose is the operating system's default. The --newline option has no effect on this option. This option may be given any number of times; all the files are read. --include-dir=pattern If any --include-dir patterns are specified, the only directories that are processed are those whose names match one of the patterns and do not match an --exclude-dir pattern. This applies to all directories, whether listed on the command line, obtained from --file-list, or by scanning a parent directory. The pattern is a PCRE2 regular expression, and is matched against the final component of the directory name, not the entire path. The -F, -w, and -x options do not apply to this pattern. The option may be given any number of times. If a directory matches both --include-dir and --exclude-dir, it is excluded. There is no short form for this option. -L, --files-without-match Instead of outputting lines from the files, just output the names of the files that do not contain any lines that would have been output. Each file name is output once, on a separate line by default, but if the -Z option is set, they are separated by zero bytes instead of newlines. This option overrides any previous -H, -h, or -l options. -l, --files-with-matches Instead of outputting lines from the files, just output the names of the files containing lines that would have been output. Each file name is output once, on a separate line, but if the -Z option is set, they are separated by zero bytes instead of newlines. Searching normally stops as soon as a matching line is found in a file. However, if the -c (count) option is also used, matching continues in order to obtain the correct count, and those files that have at least one match are listed along with their counts. Using this option with -c is a way of suppressing the listing of files with no matches that occurs with -c on its own. This option overrides any previous -H, -h, or -L options. --label=name This option supplies a name to be used for the standard input when file names are being output. If not supplied, "(standard input)" is used. There is no short form for this option. --line-buffered When this option is given, non-compressed input is read and processed line by line, and the output is flushed after each write. By default, input is read in large chunks, unless pcre2grep can determine that it is reading from a terminal, which is currently possible only in Unix-like environments or Windows. Output to terminal is normally automatically flushed by the operating system. This option can be useful when the input or output is attached to a pipe and you do not want pcre2grep to buffer up large amounts of data. However, its use will affect performance, and the -M (multiline) option ceases to work. When input is from a compressed .gz or .bz2 file, --line-buffered is ignored. --line-offsets Instead of showing lines or parts of lines that match, show each match as a line number, the offset from the start of the line, and a length. The line number is terminated by a colon (as usual; see the -n option), and the offset and length are separated by a comma. In this mode, --colour has no effect, and no context is shown. That is, the -A, -B, and -C options are ignored. If there is more than one match in a line, each of them is shown separately. This option is mutually exclusive with --output, --file-offsets, and --only-matching. --locale=locale-name This option specifies a locale to be used for pattern matching. It overrides the value in the LC_ALL or LC_CTYPE environment variables. If no locale is specified, the PCRE2 library's default (usually the "C" locale) is used. There is no short form for this option. -M, --multiline Allow patterns to match more than one line. When this option is set, the PCRE2 library is called in "multiline" mode, and a match is allowed to continue past the end of the initial line and onto one or more subsequent lines. Patterns used with -M may usefully contain literal newline characters and internal occurrences of ^ and $ characters, because in multiline mode these can match at internal newlines. Because pcre2grep is scanning multiple lines, the \Z and \z assertions match only at the end of the last line in the file. The \A assertion matches at the start of the first line of a match. This can be any line in the file; it is not anchored to the first line. The output for a successful match may consist of more than one line. The first line is the line in which the match started, and the last line is the line in which the match ended. If the matched string ends with a newline sequence, the output ends at the end of that line. If -v is set, none of the lines in a multi-line match are output. Once a match has been handled, scanning restarts at the beginning of the line after the one in which the match ended. The newline sequence that separates multiple lines must be matched as part of the pattern. For example, to find the phrase "regular expression" in a file where "regular" might be at the end of a line and "expression" at the start of the next line, you could use this command: pcre2grep -M 'regular\s+expression' <file> The \s escape sequence matches any white space character, including newlines, and is followed by + so as to match trailing white space on the first line as well as possibly handling a two-character newline sequence. There is a limit to the number of lines that can be matched, imposed by the way that pcre2grep buffers the input file as it scans it. With a sufficiently large processing buffer, this should not be a problem. The -M option does not work when input is read line by line (see --line-buffered.) -m number, --max-count=number Stop processing after finding number matching lines, or non- matching lines if -v is also set. Any trailing context lines are output after the final match. In multiline mode, each multiline match counts as just one line for this purpose. If this limit is reached when reading the standard input from a regular file, the file is left positioned just after the last matching line. If -c is also set, the count that is output is never greater than number. This option has no effect if used with -L, -l, or -q, or when just checking for a match in a binary file. --match-limit=number Processing some regular expression patterns may take a very long time to search for all possible matching strings. Others may require a very large amount of memory. There are three options that set resource limits for matching. The --match-limit option provides a means of limiting computing resource usage when processing patterns that are not going to match, but which have a very large number of possibilities in their search trees. The classic example is a pattern that uses nested unlimited repeats. Internally, PCRE2 has a counter that is incremented each time around its main processing loop. If the value set by --match-limit is reached, an error occurs. The --heap-limit option specifies, as a number of kibibytes (units of 1024 bytes), the maximum amount of heap memory that may be used for matching. The --depth-limit option limits the depth of nested backtracking points, which indirectly limits the amount of memory that is used. The amount of memory needed for each backtracking point depends on the number of capturing parentheses in the pattern, so the amount of memory that is used before this limit acts varies from pattern to pattern. This limit is of use only if it is set smaller than --match- limit. There are no short forms for these options. The default limits can be set when the PCRE2 library is compiled; if they are not specified, the defaults are very large and so effectively unlimited. --max-buffer-size=number This limits the expansion of the processing buffer, whose initial size can be set by --buffer-size. The maximum buffer size is silently forced to be no smaller than the starting buffer size. -N newline-type, --newline=newline-type Six different conventions for indicating the ends of lines in scanned files are supported. For example: pcre2grep -N CRLF 'some pattern' <file> The newline type may be specified in upper, lower, or mixed case. If the newline type is NUL, lines are separated by binary zero characters. The other types are the single- character sequences CR (carriage return) and LF (linefeed), the two-character sequence CRLF, an "anycrlf" type, which recognizes any of the preceding three types, and an "any" type, for which any Unicode line ending sequence is assumed to end a line. The Unicode sequences are the three just mentioned, plus VT (vertical tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029). When the PCRE2 library is built, a default line-ending sequence is specified. This is normally the standard sequence for the operating system. Unless otherwise specified by this option, pcre2grep uses the library's default. This option makes it possible to use pcre2grep to scan files that have come from other environments without having to modify their line endings. If the data that is being scanned does not agree with the convention set by this option, pcre2grep may behave in strange ways. Note that this option does not apply to files specified by the -f, --exclude-from, or --include-from options, which are expected to use the operating system's standard newline sequence. -n, --line-number Precede each output line by its line number in the file, followed by a colon for matching lines or a hyphen for context lines. If the file name is also being output, it precedes the line number. When the -M option causes a pattern to match more than one line, only the first is preceded by its line number. This option is forced if --line-offsets is used. --no-group-separator Do not output a separator between groups of lines when -A, -B, or -C is in use. The default is to output a line containing two hyphens. See also --group-separator. --no-jit If the PCRE2 library is built with support for just-in-time compiling (which speeds up matching), pcre2grep automatically makes use of this, unless it was explicitly disabled at build time. This option can be used to disable the use of JIT at run time. It is provided for testing and working around problems. It should never be needed in normal use. -O text, --output=text When there is a match, instead of outputting the line that matched, output just the text specified in this option, followed by an operating-system standard newline. In this mode, --colour has no effect, and no context is shown. That is, the -A, -B, and -C options are ignored. The --newline option has no effect on this option, which is mutually exclusive with --only-matching, --file-offsets, and --line- offsets. However, like --only-matching, if there is more than one match in a line, each of them causes a line of output. Escape sequences starting with a dollar character may be used to insert the contents of the matched part of the line and/or captured substrings into the text. $<digits> or ${<digits>} is replaced by the captured substring of the given decimal number; zero substitutes the whole match. If the number is greater than the number of capturing substrings, or if the capture is unset, the replacement is empty. $a is replaced by bell; $b by backspace; $e by escape; $f by form feed; $n by newline; $r by carriage return; $t by tab; $v by vertical tab. $o<digits> or $o{<digits>} is replaced by the character whose code point is the given octal number. In the first form, up to three octal digits are processed. When more digits are needed in Unicode mode to specify a wide character, the second form must be used. $x<digits> or $x{<digits>} is replaced by the character represented by the given hexadecimal number. In the first form, up to two hexadecimal digits are processed. When more digits are needed in Unicode mode to specify a wide character, the second form must be used. Any other character is substituted by itself. In particular, $$ is replaced by a single dollar. -o, --only-matching Show only the part of the line that matched a pattern instead of the whole line. In this mode, no context is shown. That is, the -A, -B, and -C options are ignored. If there is more than one match in a line, each of them is shown separately, on a separate line of output. If -o is combined with -v (invert the sense of the match to find non-matching lines), no output is generated, but the return code is set appropriately. If the matched portion of the line is empty, nothing is output unless the file name or line number are being printed, in which case they are shown on an otherwise empty line. This option is mutually exclusive with --output, --file-offsets and --line-offsets. -onumber, --only-matching=number Show only the part of the line that matched the capturing parentheses of the given number. Up to 50 capturing parentheses are supported by default. This limit can be changed via the --om-capture option. A pattern may contain any number of capturing parentheses, but only those whose number is within the limit can be accessed by -o. An error occurs if the number specified by -o is greater than the limit. -o0 is the same as -o without a number. Because these options can be given without an argument (see above), if an argument is present, it must be given in the same shell item, for example, -o3 or --only-matching=2. The comments given for the non-argument case above also apply to this option. If the specified capturing parentheses do not exist in the pattern, or were not set in the match, nothing is output unless the file name or line number are being output. If this option is given multiple times, multiple substrings are output for each match, in the order the options are given, and all on one line. For example, -o3 -o1 -o3 causes the substrings matched by capturing parentheses 3 and 1 and then 3 again to be output. By default, there is no separator (but see the next but one option). --om-capture=number Set the number of capturing parentheses that can be accessed by -o. The default is 50. --om-separator=text Specify a separating string for multiple occurrences of -o. The default is an empty string. Separating strings are never coloured. -P, --no-ucp Starting from release 10.43, when UTF/Unicode mode is specified with -u or -U, the PCRE2_UCP option is used by default. This means that the POSIX classes in patterns match more than just ASCII characters. For example, [:digit:] matches any Unicode decimal digit. The --no-ucp option suppresses PCRE2_UCP, thus restricting the POSIX classes to ASCII characters, as was the case in earlier releases. Note that there are now more fine-grained option settings within patterns that affect individual classes. For example, when in UCP mode, the sequence (?aP) restricts [:word:] to ASCII letters, while allowing \w to match Unicode letters and digits. -q, --quiet Work quietly, that is, display nothing except error messages. The exit status indicates whether or not any matches were found. -r, --recursive If any given path is a directory, recursively scan the files it contains, taking note of any --include and --exclude settings. By default, a directory is read as a normal file; in some operating systems this gives an immediate end-of- file. This option is a shorthand for setting the -d option to "recurse". --recursion-limit=number This is an obsolete synonym for --depth-limit. See --match- limit above for details. -s, --no-messages Suppress error messages about non-existent or unreadable files. Such files are quietly skipped. However, the return code is still 2, even if matches were found in other files. -t, --total-count This option is useful when scanning more than one file. If used on its own, -t suppresses all output except for a grand total number of matching lines (or non-matching lines if -v is used) in all the files. If -t is used with -c, a grand total is output except when the previous output is just one line. In other words, it is not output when just one file's count is listed. If file names are being output, the grand total is preceded by "TOTAL:". Otherwise, it appears as just another number. The -t option is ignored when used with -L (list files without matches), because the grand total would always be zero. -u, --utf Operate in UTF/Unicode mode. This option is available only if PCRE2 has been compiled with UTF-8 support. All patterns (including those for any --exclude and --include options) and all lines that are scanned must be valid strings of UTF-8 characters. If an invalid UTF-8 string is encountered, an error occurs. -U, --utf-allow-invalid As --utf, but in addition subject lines may contain invalid UTF-8 code unit sequences. These can never form part of any pattern match. Patterns themselves, however, must still be valid UTF-8 strings. This facility allows valid UTF-8 strings to be sought within arbitrary byte sequences in executable or other binary files. For more details about matching in non- valid UTF-8 strings, see the pcre2unicode(3) documentation. -V, --version Write the version numbers of pcre2grep and the PCRE2 library to the standard output and then exit. Anything else on the command line is ignored. -v, --invert-match Invert the sense of the match, so that lines which do not match any of the patterns are the ones that are found. When this option is set, options such as --only-matching and --output, which specify parts of a match that are to be output, are ignored. -w, --word-regex, --word-regexp Force the patterns only to match "words". That is, there must be a word boundary at the start and end of each matched string. This is equivalent to having "\b(?:" at the start of each pattern, and ")\b" at the end. This option applies only to the patterns that are matched against the contents of files; it does not apply to patterns specified by any of the --include or --exclude options. -x, --line-regex, --line-regexp Force the patterns to start matching only at the beginnings of lines, and in addition, require them to match entire lines. In multiline mode the match may be more than one line. This is equivalent to having "^(?:" at the start of each pattern and ")$" at the end. This option applies only to the patterns that are matched against the contents of files; it does not apply to patterns specified by any of the --include or --exclude options. -Z, --null Terminate files names in the regular output with a zero byte (the NUL character) instead of what would normally appear. This is useful when file names contain unusual characters such as colons, hyphens, or even newlines. The option does not apply to file names in error messages. ENVIRONMENT VARIABLES The environment variables LC_ALL and LC_CTYPE are examined, in that order, for a locale. The first one that is set is used. This can be overridden by the --locale option. If no locale is set, the PCRE2 library's default (usually the "C" locale) is used. NEWLINES The -N (--newline) option allows pcre2grep to scan files with newline conventions that differ from the default. This option affects only the way scanned files are processed. It does not affect the interpretation of files specified by the -f, --file-list, --exclude-from, or --include-from options. Any parts of the scanned input files that are written to the standard output are copied with whatever newline sequences they have in the input. However, if the final line of a file is output, and it does not end with a newline sequence, a newline sequence is added. If the newline setting is CR, LF, CRLF or NUL, that line ending is output; for the other settings (ANYCRLF or ANY) a single NL is used. The newline setting does not affect the way in which pcre2grep writes newlines in informational messages to the standard output and error streams. Under Windows, the standard output is set to be binary, so that "\r\n" at the ends of output lines that are copied from the input is not converted to "\r\r\n" by the C I/O library. This means that any messages written to the standard output must end with "\r\n". For all other operating systems, and for all messages to the standard error stream, "\n" is used. OPTIONS COMPATIBILITY WITH GNU GREP Many of the short and long forms of pcre2grep's options are the same as in the GNU grep program. Any long option of the form --xxx-regexp (GNU terminology) is also available as --xxx-regex (PCRE2 terminology). However, the --case-restrict, --depth-limit, -E, --file-list, --file- offsets, --heap-limit, --include-dir, --line-offsets, --locale, --match-limit, -M, --multiline, -N, --newline, --no-ucp, --om- separator, --output, -P, -u, --utf, -U, and --utf-allow-invalid options are specific to pcre2grep, as is the use of the --only-matching option with a capturing parentheses number. Although most of the common options work the same way, a few are different in pcre2grep. For example, the --include option's argument is a glob for GNU grep, but in pcre2grep it is a regular expression to which the -i option applies. If both the -c and -l options are given, GNU grep lists only file names, without counts, but pcre2grep gives the counts as well. OPTIONS WITH DATA There are four different ways in which an option with data can be specified. If a short form option is used, the data may follow immediately, or (with one exception) in the next command line item. For example: -f/some/file -f /some/file The exception is the -o option, which may appear with or without data. Because of this, if data is present, it must follow immediately in the same item, for example -o3. If a long form option is used, the data may appear in the same command line item, separated by an equals character, or (with two exceptions) it may appear in the next command line item. For example: --file=/some/file --file /some/file Note, however, that if you want to supply a file name beginning with ~ as data in a shell command, and have the shell expand ~ to a home directory, you must separate the file name from the option, because the shell does not treat ~ specially unless it is at the start of an item. The exceptions to the above are the --colour (or --color) and --only- matching options, for which the data is optional. If one of these options does have data, it must be given in the first form, using an equals character. Otherwise pcre2grep will assume that it has no data. USING PCRE2'S CALLOUT FACILITY pcre2grep has, by default, support for calling external programs or scripts or echoing specific strings during matching by making use of PCRE2's callout facility. However, this support can be completely or partially disabled when pcre2grep is built. You can find out whether your binary has support for callouts by running it with the --help option. If callout support is completely disabled, all callouts in patterns are ignored by pcre2grep. If the facility is partially disabled, calling external programs is not supported, and callouts that request it are ignored. A callout in a PCRE2 pattern is of the form (?C<arg>) where the argument is either a number or a quoted string (see the pcre2callout documentation for details). Numbered callouts are ignored by pcre2grep; only callouts with string arguments are useful. Echoing a specific string Starting the callout string with a pipe character invokes an echoing facility that avoids calling an external program or script. This facility is always available, provided that callouts were not completely disabled when pcre2grep was built. The rest of the callout string is processed as a zero-terminated string, which means it should not contain any internal binary zeros. It is written to the output, having first been passed through the same escape processing as text from the --output (-O) option (see above). However, $0 cannot be used to insert a matched substring because the match is still in progress. Instead, the single character '0' is inserted. Any syntax errors in the string (for example, a dollar not followed by another character) causes the callout to be ignored. No terminator is added to the output string, so if you want a newline, you must include it explicitly using the escape $n. For example: pcre2grep '(.)(..(.))(?C"|[$1] [$2] [$3]$n")' <some file> Matching continues normally after the string is output. If you want to see only the callout output but not any output from an actual match, you should end the pattern with (*FAIL). Calling external programs or scripts This facility can be independently disabled when pcre2grep is built. It is supported for Windows, where a call to _spawnvp() is used, for VMS, where lib$spawn() is used, and for any Unix-like environment where fork() and execv() are available. If the callout string does not start with a pipe (vertical bar) character, it is parsed into a list of substrings separated by pipe characters. The first substring must be an executable name, with the following substrings specifying arguments: executable_name|arg1|arg2|... Any substring (including the executable name) may contain escape sequences started by a dollar character. These are the same as for the --output (-O) option documented above, except that $0 cannot insert the matched string because the match is still in progress. Instead, the character '0' is inserted. If you need a literal dollar or pipe character in any substring, use $$ or $| respectively. Here is an example: echo -e "abcde\n12345" | pcre2grep \ '(?x)(.)(..(.)) (?C"/bin/echo|Arg1: [$1] [$2] [$3]|Arg2: $|${1}$| ($4)")()' - Output: Arg1: [a] [bcd] [d] Arg2: |a| () abcde Arg1: [1] [234] [4] Arg2: |1| () 12345 The parameters for the system call that is used to run the program or script are zero-terminated strings. This means that binary zero characters in the callout argument will cause premature termination of their substrings, and therefore should not be present. Any syntax errors in the string (for example, a dollar not followed by another character) causes the callout to be ignored. If running the program fails for any reason (including the non-existence of the executable), a local matching failure occurs and the matcher backtracks in the normal way. MATCHING ERRORS It is possible to supply a regular expression that takes a very long time to fail to match certain lines. Such patterns normally involve nested indefinite repeats, for example: (a+)*\d when matched against a line of a's with no final digit. The PCRE2 matching function has a resource limit that causes it to abort in these circumstances. If this happens, pcre2grep outputs an error message and the line that caused the problem to the standard error stream. If there are more than 20 such errors, pcre2grep gives up. The --match-limit option of pcre2grep can be used to set the overall resource limit. There are also other limits that affect the amount of memory used during matching; see the discussion of --heap-limit and --depth-limit above. DIAGNOSTICS Exit status is 0 if any matches were found, 1 if no matches were found, and 2 for syntax errors, overlong lines, non-existent or inaccessible files (even if matches were found in other files) or too many matching errors. Using the -s option to suppress error messages about inaccessible files does not affect the return code. When run under VMS, the return code is placed in the symbol PCRE2GREP_RC because VMS does not distinguish between exit(0) and exit(1). SEE ALSO pcre2pattern(3), pcre2syntax(3), pcre2callout(3), pcre2unicode(3). AUTHOR Philip Hazel Retired from University Computing Service Cambridge, England. REVISION Last updated: 22 December 2023 Copyright (c) 1997-2023 University of Cambridge. PCRE2 10.43 22 December 2023 PCRE2GREP(1)
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autopoint
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Copies standard gettext infrastructure files into a source package.
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autopoint - copies standard gettext infrastructure
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autopoint [OPTION]...
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--help print this help and exit --version print version information and exit -f, --force force overwriting of files that already exist -n, --dry-run print modifications but don't perform them AUTHOR Written by Bruno Haible REPORTING BUGS Report bugs in the bug tracker at <https://savannah.gnu.org/projects/gettext> or by email to <bug-gettext@gnu.org>. COPYRIGHT Copyright © 2002-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO The full documentation for autopoint is maintained as a Texinfo manual. If the info and autopoint programs are properly installed at your site, the command info autopoint should give you access to the complete manual. GNU gettext-tools 0.22.5 February 2024 AUTOPOINT(1)
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convertsegfilestops
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prezip-bin
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prezip-bin compresses/decompresses sorted word lists from standard input to standard output. Prezip-bin is similar to word-list-compress(1) but it allows a larger character set of {0x00...0x09, 0x0B, 0x0C, 0x0E...0xFF} and multi-words larger than 255 characters in length. It can also decompress word-list-compress(1) compatible files. COMMANDS Prezip-bin accepts only one of these commands. -V Display prezip-bin version number to standard output. -d Read a compressed word list from standard input and decompress it to standard output. This can be a word-list-compress(1) or a prezip-bin compressed file. -z Read a binary word list from standard input and compress it to standard output.
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prezip-bin - prefix zip delta word list compressor/decompressor
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prezip-bin [ -V | -d | -z ]
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prezip-bin -d <wordlist.cwl >wordlist.txt Decompress file wordlist.cwl to text file wordlist.txt prezip-bin -z <wordlist.txt >wordlist.pz 2>errors.txt Compress wordlist.txt to binary file wordlist.pz and send any error messages to a text file named errors.txt LC_COLLATE=C sort -u <wordlist.txt | prezip-bin -z >wordlist.pz Sort a word list, then pipe it to prezip-bin to create a compressed binary wordlist.pz file. prezip-bin -d <words.pz | aspell create master ./words.rws Decompress a wordlist, then pipe it to aspell(1) to create a spelling list. Please check the aspell(1) info manual for proper usage and options. TIPS Prezip-bin is best used with sorted word list type files. It is not a general purpose compression program since resulting files may actually increase in size. Unlike word-list-compress(1) if your word list has leading or trailing blank spaces for formatting purposes, you should remove them first before you compress your list using prezip-bin -z , otherwise those spaces will be included in the compressed binary output. DIAGNOSTICS Prezip-bin normally exits with a return code of 0. If it encounters an error, a message is sent to standard error output (stderr), and prezip-bin exits with a non-zero return value. Error messages are listed below: (display help/usage message) Unknown command given on the command line so prezip-bin displays a usage message to standard error output. unknown format The input file appears not to be an expected format, or may possibly be a more advanced format. The output file will be empty. corrupt input This is only for the decompression command -d. The input file appeared to be of a correct format, but something appears wrong now. There may be some valid data in output, but due to input corruption, the rest of the file can not be completed. unexpected EOF The input file appeared okay but ended sooner than expected, therefore the output file is not complete. SEE ALSO aspell(1), aspell-import(1), run-with-aspell(1), word-list-compress(1) Aspell is fully documented in its Texinfo manual. See the `aspell' entry in info for more complete documentation. REPORTING BUGS For help, see the Aspell homepage at <http://aspell.net>. Send bug reports/comments to the Aspell user list at the above address. AUTHOR This info page was written by Jose Da Silva <digital@joescat.com>. prezip-bin-0.1.2 2005-09-30 PREZIP-BIN(1)
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gifclrmp
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A program to modify GIF image colormaps. Any local colormap in a GIF file can be modified at a time, or the global screen one.
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gifclrmp - extract colormaps from GIF images
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gifclrmp [-v] [-s] [-l mapfile] [-t trans] [-g gamma] [-i image] [-h] [gif-file]
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-v Verbose mode (show progress). Enables printout of running scan lines. -s Select the global screen color map. -l mapfile Load color map from this file instead of selected color map. -t trans Change color index values. The change is made to both the selected color table and the raster bits of the selected image. A translation file is a list of pairs of `before' and `after' index values. At present, the `before' index values must be in ascending order starting from 0. -g gamma Apply gamma correction to selected color map. -i image Select the color map of the numbered image. -h Print one command line help, similar to Usage above. If no GIF file is given, gifclip will try to read a GIF file from stdin. NOTES • The default operation is to dump out the selected color map in text format. • The file to load/dump is simply one color map entry per line. Each such entry line has four integers: "ColorIndex Red Green Blue", where color index is in ascending order starting from 1. AUTHOR Gershon Elber. GIFLIB 2 May 2012 GIFCLRMP(1)
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pyftsubset
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hwloc-bind
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hwloc-bind execs an executable (with optional command line arguments) that is bound to the specified location (or list of locations). Location specification is described in hwloc(7). Upon successful execution, hwloc-bind simply sets bindings and then execs the executable over itself. If a bitmask location is given with prefix nodeset=, then it is considered a nodeset instead of a CPU set. See also --nodeset. If multiple locations are given, they are combined in the sense that the binding will be wider. The process will be allowed to run on every location inside the combination. The list of input locations may be explicitly ended with "--". If binding fails, or if the binding set is empty, and --force was not given, hwloc-bind returns with an error instead of launching the executable. NOTE: It is highly recommended that you read the hwloc(7) overview page before reading this man page. Most of the concepts described in hwloc(7) directly apply to the hwloc-bind utility.
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hwloc-bind - Launch a command that is bound to specific processors and/or memory, or consult the binding of an existing program
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hwloc-bind [topology options] [options] <location1> [<location2> [...] ] [--] <command> ... Note that hwloc(7) provides a detailed explanation of the hwloc system and of valid <location> formats; it should be read before reading this man page. TOPOLOGY OPTIONS All topology options must be given before all other options. --no-smt, --no-smt=<N> Only keep the first PU per core before binding. If <N> is specified, keep the <N>-th instead, if any. PUs are ordered by physical index during this filtering. Note that this option is applied after searching locations. Hence --no-smt pu:2-5 will first select the PUs #2 to #5 in the machine before binding on one of them per core. To rather bind on PUs #2 to #5 after filtering one per core, you should combine with hwloc-calc: hwloc-bind $(hwloc-calc --restrict $(hwloc-calc --no-smt all) pu:2-5) -- echo hello --restrict <cpuset> Restrict the topology to the given cpuset. This removes some PUs and their now-child-less parents. Beware that restricting the PUs in a topology may change the logical indexes of many objects, including NUMA nodes. --restrict nodeset=<nodeset> Restrict the topology to the given nodeset (unless --restrict-flags specifies something different). This removes some NUMA nodes and their now-child-less parents. Beware that restricting the NUMA nodes in a topology may change the logical indexes of many objects, including PUs. --restrict-flags <flags> Enforce flags when restricting the topology. Flags may be given as numeric values or as a comma-separated list of flag names that are passed to hwloc_topology_restrict(). Those names may be substrings of actual flag names as long as a single one matches, for instance bynodeset,memless. The default is 0 (or none). --disallowed Include objects disallowed by administrative limitations. --best-memattr <name> Select the best NUMA node among the given memory binding set by looking at the memory attribute given by <name> (or as an index). If the memory attribute values depend on the initiator, the CPU binding set is used as the initiator. Standard attribute names are Capacity, Locality, Bandwidth, and Latency. All existing attributes in the current topology may be listed with $ lstopo --memattrs --hbm Only take high bandwidth memory nodes (marked with "HBM" subtype, or "MCDRAM" on Intel Xeon Phi) in account when looking for NUMA nodes in the input locations. This option must be combined with NUMA node locations, such as --hbm numa:1 for binding on the second HBM node. It may also be written as numa[hbm]:1 or numa[mcdram]:1. --no-hbm Ignore high bandwidth memory nodes (marked with "HBM" subtype, or "MCDRAM" on Intel Xeon Phi MCDRAM) when looking for NUMA nodes in the input locations.
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All these options must be given after all topology options above. --cpubind Use following arguments for CPU binding (default). --membind Use following arguments for memory binding. If --mempolicy is not also given, the default policy is bind. --mempolicy <policy> Change the memory binding policy. This option is only meaningful when an actual binding is also given with --membind. If --membind is given without --mempolicy, the default policy is bind. The available policies are default, firsttouch, bind, interleave and nexttouch. See hwloc.h for details about these policies. Note that hwloc's memory binding policies may be slightly different from operating system policies. For instance, the hwloc bind policy uses Linux MPOL_PREFERRED_MANY (or MPOL_PREFERRED) by default, but it switches to Linux MPOL_BIND if the hwloc strict option or flag is also given. --get Report the current bindings. The output is an opaque bitmask that may be translated into objects with hwloc-calc (see EXAMPLES below). When a command is given, the binding is displayed before executing the command. When no command is given, the program exits after displaying the current binding. When combined with --membind, report the memory binding instead of CPU binding. No location may be given since no binding is performed. --nodeset Report binding as a NUMA memory node set instead of a CPU set if --get was given. This is useful for manipulating CPU-less NUMA nodes since their cpuset is empty while their nodeset is correct. Also parse input bitmasks as nodesets instead of cpusets. When this option is not passed, individual input bitmasks may still be parsed as nodesets if they are prefixed with nodeset=. -e --get-last-cpu-location Report the last processors where the process ran. The output is an opaque bitmask that may be translated into objects with hwloc-calc (see EXAMPLES below). Note that the result may already be outdated when reported since the operating system may move the process to other processors at any time according to the binding. When a command is given, the last processors is displayed before executing the command. When no command is given, the program exits after displaying the last processors. This option cannot be combined with --membind. No location may be given since no binding is performed. --single Bind on a single CPU to prevent migration. --strict Require strict binding. --pid <pid> Operate on pid <pid> --tid <tid> Operate on thread <tid> instead of on an entire process. The feature is only supported on Linux for thread CPU binding, or for reporting the last processor where the thread ran if -e was also passed. -p --physical Interpret input locations with OS/physical indexes instead of logical indexes. This option does not apply to the output, see --get above. -l --logical Interpret input locations with logical indexes instead of physical/OS indexes (default). This option does not apply to the output, see --get above. --taskset Display CPU set strings in the format recognized by the taskset command-line program instead of hwloc-specific CPU set string format. This option has no impact on the format of input CPU set strings, both formats are always accepted. -f --force Launch the executable even if binding failed. -q --quiet Hide non-fatal error messages. It includes locations pointing to non-existing objects, as well as failure to bind. This is usually useful in addition to --force. -v --verbose Verbose output. --version Report version and exit. -h --help Display help message and exit.
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hwloc-bind's operation is best described through several examples. More details about how locations are specified on the hwloc-bind command line are described in hwloc(7). To run the echo command on the first logical processor of the second package: $ hwloc-bind package:1.pu:0 -- echo hello which is exactly equivalent to the following line as long as there is no ambiguity between hwloc-bind option names and the executed command name: $ hwloc-bind package:1.pu:0 echo hello To bind the "echo" command to the first core of the second package and the second core of the first package: $ hwloc-bind package:1.core:0 package:0.core:1 -- echo hello To bind on the first PU of all cores of the first package: $ hwloc-bind package:0.core:all.pu:0 -- echo hello $ hwloc-bind --no-smt package:0 -- echo hello To bind on the memory node local to a PU with largest capacity: $ hwloc-bind --best-memattr capacity --cpubind pu:23 --membind pu:23 -- echo hello To bind memory on the first NUMA node marked with "HBM" subtype: $ hwloc-bind --membind numa[hbm]:0 -- echo hello $ hwloc-bind --hbm --membind numa:0 -- echo hello To bind memory on the first high-bandwidth memory node (MCDRAM) on Intel Xeon Phi: $ hwloc-bind --membind numa[mcdram]:0 -- echo hello $ hwloc-bind --hbm --membind numa:0 -- echo hello Note that binding the "echo" command to multiple processors is probably meaningless (because "echo" is likely implemented as a single-threaded application); these examples just serve to show what hwloc-bind can do. To run on the first three packages on the second and third nodes: $ hwloc-bind node:1-2.package:0:3 -- echo hello which is also equivalent to: $ hwloc-bind node:1-2.package:0-2 -- echo hello Note that if you attempt to bind to objects that do not exist, hwloc- bind will not warn unless -v was specified. To run on processor with physical index 2 in package with physical index 1: $ hwloc-bind --physical package:1.core:2 -- echo hello To run on odd cores within even packages: $ hwloc-bind package:even.core:odd -- echo hello To run on the first package, except on its second and fifth cores: $ hwloc-bind package:0 ~package:0.core:1 ~package:0.core:4 -- echo hello To run anywhere except on the first package: $ hwloc-bind all ~package:0 -- echo hello To run on a core near the network interface named eth0: $ hwloc-bind os=eth0 -- echo hello To run on a core near the PCI device whose bus ID is 0000:01:02.0: $ hwloc-bind pci=0000:01:02.0 -- echo hello To bind memory on second memory node and run on first node (when supported by the OS): $ hwloc-bind --cpubind node:1 --membind node:0 -- echo hello hwloc-bind does not have an option to select a kind of CPU core but it may be combined with hwloc-calc to do so. For instance, to bind on the first two cores whose kind matches CoreType=IntelAtom: $ hwloc-bind $(hwloc-calc --restrict $(hwloc-calc --cpukind CoreType=IntelAtom all) core:0-1) -- echo hello The --get option can report current bindings. This example shows nesting hwloc-bind invocations to set a binding and then report it: $ hwloc-bind node:1.package:2 -- hwloc-bind --get 0x00004444,0x44000000 hwloc-calc can also be used to convert cpu mask strings to human- readable package/core/PU strings; see the description of -H in hwloc- calc(1) for more details. The following example binds to all the PUs in a specific core, uses the --get option to retrieve where the process was actually bound, and then uses hwloc-calc to display the resulting cpu mask in space-delimited list of human-readable locations: $ hwloc-bind package:1.core:2 -- hwloc-bind --get | hwloc-calc -H package.core.pu Package:1.Core:2.PU:0 Package:1.Core:2.PU:1 hwloc-calc may convert this output into actual objects, either with logical or physical indexes: $ hwloc-calc --physical -I pu `hwloc-bind --get` 26,30,34,38,42,46 $ hwloc-calc --logical -I pu `hwloc-bind --get` --sep " " 24 25 26 27 28 29 Locations may also be specified as a hex bit mask (typically generated by hwloc-calc). For example: $ hwloc-bind 0x00004444,0x44000000 -- echo hello $ hwloc-bind `hwloc-calc node:1.package:2` -- echo hello The current memory binding may also be reported: $ hwloc-bind --membind node:1 --mempolicy interleave -- hwloc-bind --get --membind 0x000000f0 (interleave) HINT If the graphics-enabled lstopo is available, use for instance $ hwloc-bind core:2 -- lstopo --pid 0 to check what the result of your binding command actually is. lstopo will graphically show where it is bound to by hwloc-bind. RETURN VALUE Upon successful execution, hwloc-bind execs the command over itself. The return value is therefore whatever the return value of the command is. hwloc-bind will return nonzero if any kind of error occurs, such as (but not limited to): failure to parse the command line, failure to retrieve process bindings, or lack of a command to execute. SEE ALSO hwloc(7), lstopo(1), hwloc-calc(1), hwloc-distrib(1) 2.10.0 December 4, 2023 HWLOC-BIND(1)
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mysqlbinlog
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The server's binary log consists of files containing “events” that describe modifications to database contents. The server writes these files in binary format. To display their contents in text format, use the mysqlbinlog utility. You can also use mysqlbinlog to display the contents of relay log files written by a replica server in a replication setup because relay logs have the same format as binary logs. The binary log and relay log are discussed further in Section 5.4.4, “The Binary Log”, and Section 17.2.4, “Relay Log and Replication Metadata Repositories”. Invoke mysqlbinlog like this: mysqlbinlog [options] log_file ... For example, to display the contents of the binary log file named binlog.000003, use this command: mysqlbinlog binlog.000003 The output includes events contained in binlog.000003. For statement-based logging, event information includes the SQL statement, the ID of the server on which it was executed, the timestamp when the statement was executed, how much time it took, and so forth. For row-based logging, the event indicates a row change rather than an SQL statement. See Section 17.2.1, “Replication Formats”, for information about logging modes. Events are preceded by header comments that provide additional information. For example: # at 141 #100309 9:28:36 server id 123 end_log_pos 245 Query thread_id=3350 exec_time=11 error_code=0 In the first line, the number following at indicates the file offset, or starting position, of the event in the binary log file. The second line starts with a date and time indicating when the statement started on the server where the event originated. For replication, this timestamp is propagated to replica servers. server id is the server_id value of the server where the event originated. end_log_pos indicates where the next event starts (that is, it is the end position of the current event + 1). thread_id indicates which thread executed the event. exec_time is the time spent executing the event, on a replication source server. On a replica, it is the difference of the end execution time on the replica minus the beginning execution time on the source. The difference serves as an indicator of how much replication lags behind the source. error_code indicates the result from executing the event. Zero means that no error occurred. Note When using event groups, the file offsets of events may be grouped together and the comments of events may be grouped together. Do not mistake these grouped events for blank file offsets. The output from mysqlbinlog can be re-executed (for example, by using it as input to mysql) to redo the statements in the log. This is useful for recovery operations after an unexpected server exit. For other usage examples, see the discussion later in this section and in Section 7.5, “Point-in-Time (Incremental) Recovery”. To execute the internal-use BINLOG statements used by mysqlbinlog, the user requires the BINLOG_ADMIN privilege (or the deprecated SUPER privilege), or the REPLICATION_APPLIER privilege plus the appropriate privileges to execute each log event. You can use mysqlbinlog to read binary log files directly and apply them to the local MySQL server. You can also read binary logs from a remote server by using the --read-from-remote-server option. To read remote binary logs, the connection parameter options can be given to indicate how to connect to the server. These options are --host, --password, --port, --protocol, --socket, and --user. When binary log files have been encrypted, which can be done from MySQL 8.0.14 onwards, mysqlbinlog cannot read them directly, but can read them from the server using the --read-from-remote-server option. Binary log files are encrypted when the server's binlog_encryption system variable is set to ON. The SHOW BINARY LOGS statement shows whether a particular binary log file is encrypted or unencrypted. Encrypted and unencrypted binary log files can also be distinguished using the magic number at the start of the file header for encrypted log files (0xFD62696E), which differs from that used for unencrypted log files (0xFE62696E). Note that from MySQL 8.0.14, mysqlbinlog returns a suitable error if you attempt to read an encrypted binary log file directly, but older versions of mysqlbinlog do not recognise the file as a binary log file at all. For more information on binary log encryption, see Section 17.3.2, “Encrypting Binary Log Files and Relay Log Files”. When binary log transaction payloads have been compressed, which can be done from MySQL 8.0.20 onwards, mysqlbinlog versions from that release on automatically decompress and decode the transaction payloads, and print them as they would uncompressed events. Older versions of mysqlbinlog cannot read compressed transaction payloads. When the server's binlog_transaction_compression system variable is set to ON, transaction payloads are compressed and then written to the server's binary log file as a single event (a Transaction_payload_event). With the --verbose option, mysqlbinlog adds comments stating the compression algorithm used, the compressed payload size that was originally received, and the resulting payload size after decompression. Note The end position (end_log_pos) that mysqlbinlog states for an individual event that was part of a compressed transaction payload is the same as the end position of the original compressed payload. Multiple decompressed events can therefore have the same end position. mysqlbinlog's own connection compression does less if transaction payloads are already compressed, but still operates on uncompressed transactions and headers. For more information on binary log transaction compression, see Section 5.4.4.5, “Binary Log Transaction Compression”. When running mysqlbinlog against a large binary log, be careful that the filesystem has enough space for the resulting files. To configure the directory that mysqlbinlog uses for temporary files, use the TMPDIR environment variable. mysqlbinlog sets the value of pseudo_replica_mode to true before executing any SQL statements. This system variable affects the handling of XA transactions, the original_commit_timestamp replication delay timestamp and the original_server_version system variable, and unsupported SQL modes. mysqlbinlog supports the following options, which can be specified on the command line or in the [mysqlbinlog] and [client] groups of an option file. For information about option files used by MySQL programs, see Section 4.2.2.2, “Using Option Files”. • --help, -? ┌────────────────────┬────────┐ │Command-Line Format │ --help │ └────────────────────┴────────┘ Display a help message and exit. • --base64-output=value ┌────────────────────┬────────────────────────┐ │Command-Line Format │ --base64-output=value │ ├────────────────────┼────────────────────────┤ │Type │ String │ ├────────────────────┼────────────────────────┤ │Default Value │ AUTO │ ├────────────────────┼────────────────────────┤ │Valid Values │ AUTO NEVER │ │ │ DECODE-ROWS │ └────────────────────┴────────────────────────┘ This option determines when events should be displayed encoded as base-64 strings using BINLOG statements. The option has these permissible values (not case-sensitive): • AUTO ("automatic") or UNSPEC ("unspecified") displays BINLOG statements automatically when necessary (that is, for format description events and row events). If no --base64-output option is given, the effect is the same as --base64-output=AUTO. Note Automatic BINLOG display is the only safe behavior if you intend to use the output of mysqlbinlog to re-execute binary log file contents. The other option values are intended only for debugging or testing purposes because they may produce output that does not include all events in executable form. • NEVER causes BINLOG statements not to be displayed. mysqlbinlog exits with an error if a row event is found that must be displayed using BINLOG. • DECODE-ROWS specifies to mysqlbinlog that you intend for row events to be decoded and displayed as commented SQL statements by also specifying the --verbose option. Like NEVER, DECODE-ROWS suppresses display of BINLOG statements, but unlike NEVER, it does not exit with an error if a row event is found. For examples that show the effect of --base64-output and --verbose on row event output, see the section called “MYSQLBINLOG ROW EVENT DISPLAY”. • --bind-address=ip_address ┌────────────────────┬───────────────────────────┐ │Command-Line Format │ --bind-address=ip_address │ └────────────────────┴───────────────────────────┘ On a computer having multiple network interfaces, use this option to select which interface to use for connecting to the MySQL server. • --binlog-row-event-max-size=N ┌────────────────────┬───────────────────────────────┐ │Command-Line Format │ --binlog-row-event-max-size=# │ ├────────────────────┼───────────────────────────────┤ │Type │ Numeric │ ├────────────────────┼───────────────────────────────┤ │Default Value │ 4294967040 │ ├────────────────────┼───────────────────────────────┤ │Minimum Value │ 256 │ ├────────────────────┼───────────────────────────────┤ │Maximum Value │ 18446744073709547520 │ └────────────────────┴───────────────────────────────┘ Specify the maximum size of a row-based binary log event, in bytes. Rows are grouped into events smaller than this size if possible. The value should be a multiple of 256. The default is 4GB. • --character-sets-dir=dir_name ┌────────────────────┬───────────────────────────────┐ │Command-Line Format │ --character-sets-dir=dir_name │ ├────────────────────┼───────────────────────────────┤ │Type │ Directory name │ └────────────────────┴───────────────────────────────┘ The directory where character sets are installed. See Section 10.15, “Character Set Configuration”. • --compress ┌────────────────────┬───────────────────────┐ │Command-Line Format │ --compress[={OFF|ON}] │ ├────────────────────┼───────────────────────┤ │Deprecated │ Yes │ ├────────────────────┼───────────────────────┤ │Type │ Boolean │ ├────────────────────┼───────────────────────┤ │Default Value │ OFF │ └────────────────────┴───────────────────────┘ Compress all information sent between the client and the server if possible. See Section 4.2.8, “Connection Compression Control”. This option was added in MySQL 8.0.17. As of MySQL 8.0.18 it is deprecated. Expect it to be removed in a future version of MySQL. See the section called “Configuring Legacy Connection Compression”. • --compression-algorithms=value ┌────────────────────┬────────────────────────────────┐ │Command-Line Format │ --compression-algorithms=value │ ├────────────────────┼────────────────────────────────┤ │Type │ Set │ ├────────────────────┼────────────────────────────────┤ │Default Value │ uncompressed │ ├────────────────────┼────────────────────────────────┤ │Valid Values │ zlib zstd uncompressed │ └────────────────────┴────────────────────────────────┘ The permitted compression algorithms for connections to the server. The available algorithms are the same as for the protocol_compression_algorithms system variable. The default value is uncompressed. For more information, see Section 4.2.8, “Connection Compression Control”. • --connection-server-id=server_id ┌────────────────────┬───────────────────────────┐ │Command-Line Format │ --connection-server-id=#] │ ├────────────────────┼───────────────────────────┤ │Type │ Integer │ ├────────────────────┼───────────────────────────┤ │Default Value │ 0 (1) │ ├────────────────────┼───────────────────────────┤ │Minimum Value │ 0 (1) │ ├────────────────────┼───────────────────────────┤ │Maximum Value │ 4294967295 │ └────────────────────┴───────────────────────────┘ --connection-server-id specifies the server ID that mysqlbinlog reports when it connects to the server. It can be used to avoid a conflict with the ID of a replica server or another mysqlbinlog process. If the --read-from-remote-server option is specified, mysqlbinlog reports a server ID of 0, which tells the server to disconnect after sending the last log file (nonblocking behavior). If the --stop-never option is also specified to maintain the connection to the server, mysqlbinlog reports a server ID of 1 by default instead of 0, and --connection-server-id can be used to replace that server ID if required. See the section called “SPECIFYING THE MYSQLBINLOG SERVER ID”. • --database=db_name, -d db_name ┌────────────────────┬────────────────────┐ │Command-Line Format │ --database=db_name │ ├────────────────────┼────────────────────┤ │Type │ String │ └────────────────────┴────────────────────┘ This option causes mysqlbinlog to output entries from the binary log (local log only) that occur while db_name is been selected as the default database by USE. The --database option for mysqlbinlog is similar to the --binlog-do-db option for mysqld, but can be used to specify only one database. If --database is given multiple times, only the last instance is used. The effects of this option depend on whether the statement-based or row-based logging format is in use, in the same way that the effects of --binlog-do-db depend on whether statement-based or row-based logging is in use. Statement-based logging. The --database option works as follows: • While db_name is the default database, statements are output whether they modify tables in db_name or a different database. • Unless db_name is selected as the default database, statements are not output, even if they modify tables in db_name. • There is an exception for CREATE DATABASE, ALTER DATABASE, and DROP DATABASE. The database being created, altered, or dropped is considered to be the default database when determining whether to output the statement. Suppose that the binary log was created by executing these statements using statement-based-logging: INSERT INTO test.t1 (i) VALUES(100); INSERT INTO db2.t2 (j) VALUES(200); USE test; INSERT INTO test.t1 (i) VALUES(101); INSERT INTO t1 (i) VALUES(102); INSERT INTO db2.t2 (j) VALUES(201); USE db2; INSERT INTO test.t1 (i) VALUES(103); INSERT INTO db2.t2 (j) VALUES(202); INSERT INTO t2 (j) VALUES(203); mysqlbinlog --database=test does not output the first two INSERT statements because there is no default database. It outputs the three INSERT statements following USE test, but not the three INSERT statements following USE db2. mysqlbinlog --database=db2 does not output the first two INSERT statements because there is no default database. It does not output the three INSERT statements following USE test, but does output the three INSERT statements following USE db2. Row-based logging. mysqlbinlog outputs only entries that change tables belonging to db_name. The default database has no effect on this. Suppose that the binary log just described was created using row-based logging rather than statement-based logging. mysqlbinlog --database=test outputs only those entries that modify t1 in the test database, regardless of whether USE was issued or what the default database is. If a server is running with binlog_format set to MIXED and you want it to be possible to use mysqlbinlog with the --database option, you must ensure that tables that are modified are in the database selected by USE. (In particular, no cross-database updates should be used.) When used together with the --rewrite-db option, the --rewrite-db option is applied first; then the --database option is applied, using the rewritten database name. The order in which the options are provided makes no difference in this regard. • --debug[=debug_options], -# [debug_options] ┌────────────────────┬──────────────────────────────┐ │Command-Line Format │ --debug[=debug_options] │ ├────────────────────┼──────────────────────────────┤ │Type │ String │ ├────────────────────┼──────────────────────────────┤ │Default Value │ d:t:o,/tmp/mysqlbinlog.trace │ └────────────────────┴──────────────────────────────┘ Write a debugging log. A typical debug_options string is d:t:o,file_name. The default is d:t:o,/tmp/mysqlbinlog.trace. This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option. • --debug-check ┌────────────────────┬───────────────┐ │Command-Line Format │ --debug-check │ ├────────────────────┼───────────────┤ │Type │ Boolean │ ├────────────────────┼───────────────┤ │Default Value │ FALSE │ └────────────────────┴───────────────┘ Print some debugging information when the program exits. This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option. • --debug-info ┌────────────────────┬──────────────┐ │Command-Line Format │ --debug-info │ ├────────────────────┼──────────────┤ │Type │ Boolean │ ├────────────────────┼──────────────┤ │Default Value │ FALSE │ └────────────────────┴──────────────┘ Print debugging information and memory and CPU usage statistics when the program exits. This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option. • --default-auth=plugin ┌────────────────────┬───────────────────────┐ │Command-Line Format │ --default-auth=plugin │ ├────────────────────┼───────────────────────┤ │Type │ String │ └────────────────────┴───────────────────────┘ A hint about which client-side authentication plugin to use. See Section 6.2.17, “Pluggable Authentication”. • --defaults-extra-file=file_name ┌────────────────────┬─────────────────────────────────┐ │Command-Line Format │ --defaults-extra-file=file_name │ ├────────────────────┼─────────────────────────────────┤ │Type │ File name │ └────────────────────┴─────────────────────────────────┘ Read this option file after the global option file but (on Unix) before the user option file. If the file does not exist or is otherwise inaccessible, an error occurs. If file_name is not an absolute path name, it is interpreted relative to the current directory. For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”. • --defaults-file=file_name ┌────────────────────┬───────────────────────────┐ │Command-Line Format │ --defaults-file=file_name │ ├────────────────────┼───────────────────────────┤ │Type │ File name │ └────────────────────┴───────────────────────────┘ Use only the given option file. If the file does not exist or is otherwise inaccessible, an error occurs. If file_name is not an absolute path name, it is interpreted relative to the current directory. Exception: Even with --defaults-file, client programs read .mylogin.cnf. For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”. • --defaults-group-suffix=str ┌────────────────────┬─────────────────────────────┐ │Command-Line Format │ --defaults-group-suffix=str │ ├────────────────────┼─────────────────────────────┤ │Type │ String │ └────────────────────┴─────────────────────────────┘ Read not only the usual option groups, but also groups with the usual names and a suffix of str. For example, mysqlbinlog normally reads the [client] and [mysqlbinlog] groups. If this option is given as --defaults-group-suffix=_other, mysqlbinlog also reads the [client_other] and [mysqlbinlog_other] groups. For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”. • --disable-log-bin, -D ┌────────────────────┬───────────────────┐ │Command-Line Format │ --disable-log-bin │ └────────────────────┴───────────────────┘ Disable binary logging. This is useful for avoiding an endless loop if you use the --to-last-log option and are sending the output to the same MySQL server. This option also is useful when restoring after an unexpected exit to avoid duplication of the statements you have logged. This option causes mysqlbinlog to include a SET sql_log_bin = 0 statement in its output to disable binary logging of the remaining output. Manipulating the session value of the sql_log_bin system variable is a restricted operation, so this option requires that you have privileges sufficient to set restricted session variables. See Section 5.1.9.1, “System Variable Privileges”. • --exclude-gtids=gtid_set ┌────────────────────┬──────────────────────────┐ │Command-Line Format │ --exclude-gtids=gtid_set │ ├────────────────────┼──────────────────────────┤ │Type │ String │ ├────────────────────┼──────────────────────────┤ │Default Value │ │ └────────────────────┴──────────────────────────┘ Do not display any of the groups listed in the gtid_set. • --force-if-open, -F ┌────────────────────┬─────────────────┐ │Command-Line Format │ --force-if-open │ └────────────────────┴─────────────────┘ Read binary log files even if they are open or were not closed properly (IN_USE flag is set); do not fail if the file ends with a truncated event. The IN_USE flag is set only for the binary log that is currently written by the server; if the server has crashed, the flag remains set until the server is started up again and recovers the binary log. Without this option, mysqlbinlog refuses to process a file with this flag set. Since the server may be in the process of writing the file, truncation of the last event is considered normal. • --force-read, -f ┌────────────────────┬──────────────┐ │Command-Line Format │ --force-read │ └────────────────────┴──────────────┘ With this option, if mysqlbinlog reads a binary log event that it does not recognize, it prints a warning, ignores the event, and continues. Without this option, mysqlbinlog stops if it reads such an event. • --get-server-public-key ┌────────────────────┬─────────────────────────┐ │Command-Line Format │ --get-server-public-key │ ├────────────────────┼─────────────────────────┤ │Type │ Boolean │ └────────────────────┴─────────────────────────┘ Request from the server the public key required for RSA key pair-based password exchange. This option applies to clients that authenticate with the caching_sha2_password authentication plugin. For that plugin, the server does not send the public key unless requested. This option is ignored for accounts that do not authenticate with that plugin. It is also ignored if RSA-based password exchange is not used, as is the case when the client connects to the server using a secure connection. If --server-public-key-path=file_name is given and specifies a valid public key file, it takes precedence over --get-server-public-key. For information about the caching_sha2_password plugin, see Section 6.4.1.2, “Caching SHA-2 Pluggable Authentication”. • --hexdump, -H ┌────────────────────┬───────────┐ │Command-Line Format │ --hexdump │ └────────────────────┴───────────┘ Display a hex dump of the log in comments, as described in the section called “MYSQLBINLOG HEX DUMP FORMAT”. The hex output can be helpful for replication debugging. • --host=host_name, -h host_name ┌────────────────────┬──────────────────┐ │Command-Line Format │ --host=host_name │ ├────────────────────┼──────────────────┤ │Type │ String │ ├────────────────────┼──────────────────┤ │Default Value │ localhost │ └────────────────────┴──────────────────┘ Get the binary log from the MySQL server on the given host. • --idempotent ┌────────────────────┬──────────────┐ │Command-Line Format │ --idempotent │ ├────────────────────┼──────────────┤ │Type │ Boolean │ ├────────────────────┼──────────────┤ │Default Value │ true │ └────────────────────┴──────────────┘ Tell the MySQL Server to use idempotent mode while processing updates; this causes suppression of any duplicate-key or key-not-found errors that the server encounters in the current session while processing updates. This option may prove useful whenever it is desirable or necessary to replay one or more binary logs to a MySQL Server which may not contain all of the data to which the logs refer. The scope of effect for this option includes the current mysqlbinlog client and session only. • --include-gtids=gtid_set ┌────────────────────┬──────────────────────────┐ │Command-Line Format │ --include-gtids=gtid_set │ ├────────────────────┼──────────────────────────┤ │Type │ String │ ├────────────────────┼──────────────────────────┤ │Default Value │ │ └────────────────────┴──────────────────────────┘ Display only the groups listed in the gtid_set. • --local-load=dir_name, -l dir_name ┌────────────────────┬───────────────────────┐ │Command-Line Format │ --local-load=dir_name │ ├────────────────────┼───────────────────────┤ │Type │ Directory name │ └────────────────────┴───────────────────────┘ For data loading operations corresponding to LOAD DATA statements, mysqlbinlog extracts the files from the binary log events, writes them as temporary files to the local file system, and writes LOAD DATA LOCAL statements to cause the files to be loaded. By default, mysqlbinlog writes these temporary files to an operating system-specific directory. The --local-load option can be used to explicitly specify the directory where mysqlbinlog should prepare local temporary files. Because other processes can write files to the default system-specific directory, it is advisable to specify the --local-load option to mysqlbinlog to designate a different directory for data files, and then designate that same directory by specifying the --load-data-local-dir option to mysql when processing the output from mysqlbinlog. For example: mysqlbinlog --local-load=/my/local/data ... | mysql --load-data-local-dir=/my/local/data ... Important These temporary files are not automatically removed by mysqlbinlog or any other MySQL program. • --login-path=name ┌────────────────────┬───────────────────┐ │Command-Line Format │ --login-path=name │ ├────────────────────┼───────────────────┤ │Type │ String │ └────────────────────┴───────────────────┘ Read options from the named login path in the .mylogin.cnf login path file. A “login path” is an option group containing options that specify which MySQL server to connect to and which account to authenticate as. To create or modify a login path file, use the mysql_config_editor utility. See mysql_config_editor(1). For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”. • --no-login-paths ┌────────────────────┬──────────────────┐ │Command-Line Format │ --no-login-paths │ └────────────────────┴──────────────────┘ Skips reading options from the login path file. See --login-path for related information. For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”. • --no-defaults ┌────────────────────┬───────────────┐ │Command-Line Format │ --no-defaults │ └────────────────────┴───────────────┘ Do not read any option files. If program startup fails due to reading unknown options from an option file, --no-defaults can be used to prevent them from being read. The exception is that the .mylogin.cnf file is read in all cases, if it exists. This permits passwords to be specified in a safer way than on the command line even when --no-defaults is used. To create .mylogin.cnf, use the mysql_config_editor utility. See mysql_config_editor(1). For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”. • --offset=N, -o N ┌────────────────────┬────────────┐ │Command-Line Format │ --offset=# │ ├────────────────────┼────────────┤ │Type │ Numeric │ └────────────────────┴────────────┘ Skip the first N entries in the log. • --open-files-limit=N ┌────────────────────┬──────────────────────┐ │Command-Line Format │ --open-files-limit=# │ ├────────────────────┼──────────────────────┤ │Type │ Numeric │ ├────────────────────┼──────────────────────┤ │Default Value │ 8 │ ├────────────────────┼──────────────────────┤ │Minimum Value │ 1 │ ├────────────────────┼──────────────────────┤ │Maximum Value │ [platform dependent] │ └────────────────────┴──────────────────────┘ Specify the number of open file descriptors to reserve. • --password[=password], -p[password] ┌────────────────────┬───────────────────────┐ │Command-Line Format │ --password[=password] │ ├────────────────────┼───────────────────────┤ │Type │ String │ └────────────────────┴───────────────────────┘ The password of the MySQL account used for connecting to the server. The password value is optional. If not given, mysqlbinlog prompts for one. If given, there must be no space between --password= or -p and the password following it. If no password option is specified, the default is to send no password. Specifying a password on the command line should be considered insecure. To avoid giving the password on the command line, use an option file. See Section 6.1.2.1, “End-User Guidelines for Password Security”. To explicitly specify that there is no password and that mysqlbinlog should not prompt for one, use the --skip-password option. • --plugin-dir=dir_name ┌────────────────────┬───────────────────────┐ │Command-Line Format │ --plugin-dir=dir_name │ ├────────────────────┼───────────────────────┤ │Type │ Directory name │ └────────────────────┴───────────────────────┘ The directory in which to look for plugins. Specify this option if the --default-auth option is used to specify an authentication plugin but mysqlbinlog does not find it. See Section 6.2.17, “Pluggable Authentication”. • --port=port_num, -P port_num ┌────────────────────┬─────────────────┐ │Command-Line Format │ --port=port_num │ ├────────────────────┼─────────────────┤ │Type │ Numeric │ ├────────────────────┼─────────────────┤ │Default Value │ 3306 │ └────────────────────┴─────────────────┘ The TCP/IP port number to use for connecting to a remote server. • --print-defaults ┌────────────────────┬──────────────────┐ │Command-Line Format │ --print-defaults │ └────────────────────┴──────────────────┘ Print the program name and all options that it gets from option files. For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”. • --print-table-metadata ┌────────────────────┬────────────────────────┐ │Command-Line Format │ --print-table-metadata │ └────────────────────┴────────────────────────┘ Print table related metadata from the binary log. Configure the amount of table related metadata binary logged using binlog-row-metadata. • --protocol={TCP|SOCKET|PIPE|MEMORY} ┌────────────────────┬────────────────────────┐ │Command-Line Format │ --protocol=type │ ├────────────────────┼────────────────────────┤ │Type │ String │ ├────────────────────┼────────────────────────┤ │Default Value │ [see text] │ ├────────────────────┼────────────────────────┤ │Valid Values │ TCP SOCKET PIPE │ │ │ MEMORY │ └────────────────────┴────────────────────────┘ The transport protocol to use for connecting to the server. It is useful when the other connection parameters normally result in use of a protocol other than the one you want. For details on the permissible values, see Section 4.2.7, “Connection Transport Protocols”. • --raw ┌────────────────────┬─────────┐ │Command-Line Format │ --raw │ ├────────────────────┼─────────┤ │Type │ Boolean │ ├────────────────────┼─────────┤ │Default Value │ FALSE │ └────────────────────┴─────────┘ By default, mysqlbinlog reads binary log files and writes events in text format. The --raw option tells mysqlbinlog to write them in their original binary format. Its use requires that --read-from-remote-server also be used because the files are requested from a server. mysqlbinlog writes one output file for each file read from the server. The --raw option can be used to make a backup of a server's binary log. With the --stop-never option, the backup is “live” because mysqlbinlog stays connected to the server. By default, output files are written in the current directory with the same names as the original log files. Output file names can be modified using the --result-file option. For more information, see the section called “USING MYSQLBINLOG TO BACK UP BINARY LOG FILES”. • --read-from-remote-source=type ┌────────────────────┬────────────────────────────────┐ │Command-Line Format │ --read-from-remote-source=type │ └────────────────────┴────────────────────────────────┘ This option reads binary logs from a MySQL server with the COM_BINLOG_DUMP or COM_BINLOG_DUMP_GTID commands by setting the option value to either BINLOG-DUMP-NON-GTIDS or BINLOG-DUMP-GTIDS, respectively. If --read-from-remote-source=BINLOG-DUMP-GTIDS is combined with --exclude-gtids, transactions can be filtered out on the source, avoiding unnecessary network traffic. The connection parameter options are used with these options or the --read-from-remote-server option. These options are --host, --password, --port, --protocol, --socket, and --user. If none of the remote options is specified, the connection parameter options are ignored. The REPLICATION SLAVE privilege is required to use these options. • --read-from-remote-master=type ┌────────────────────┬────────────────────────────────┐ │Command-Line Format │ --read-from-remote-master=type │ ├────────────────────┼────────────────────────────────┤ │Deprecated │ Yes │ └────────────────────┴────────────────────────────────┘ Deprecated synonym for --read-from-remote-source. • --read-from-remote-server=file_name, -R ┌────────────────────┬─────────────────────────────────────┐ │Command-Line Format │ --read-from-remote-server=file_name │ └────────────────────┴─────────────────────────────────────┘ Read the binary log from a MySQL server rather than reading a local log file. This option requires that the remote server be running. It works only for binary log files on the remote server, not relay log files, and takes only the binary log file name (including the numeric suffix) as its argument, while ignoring any path. The connection parameter options are used with this option or the --read-from-remote-source option. These options are --host, --password, --port, --protocol, --socket, and --user. If neither of the remote options is specified, the connection parameter options are ignored. The REPLICATION SLAVE privilege is required to use this option. This option is like --read-from-remote-source=BINLOG-DUMP-NON-GTIDS. • --result-file=name, -r name ┌────────────────────┬────────────────────┐ │Command-Line Format │ --result-file=name │ └────────────────────┴────────────────────┘ Without the --raw option, this option indicates the file to which mysqlbinlog writes text output. With --raw, mysqlbinlog writes one binary output file for each log file transferred from the server, writing them by default in the current directory using the same names as the original log file. In this case, the --result-file option value is treated as a prefix that modifies output file names. • --require-row-format ┌────────────────────┬──────────────────────┐ │Command-Line Format │ --require-row-format │ ├────────────────────┼──────────────────────┤ │Type │ Boolean │ ├────────────────────┼──────────────────────┤ │Default Value │ false │ └────────────────────┴──────────────────────┘ Require row-based binary logging format for events. This option enforces row-based replication events for mysqlbinlog output. The stream of events produced with this option would be accepted by a replication channel that is secured using the REQUIRE_ROW_FORMAT option of the CHANGE REPLICATION SOURCE TO statement. binlog_format=ROW must be set on the server where the binary log was written. When you specify this option, mysqlbinlog stops with an error message if it encounters any events that are disallowed under the REQUIRE_ROW_FORMAT restrictions, including LOAD DATA INFILE instructions, creating or dropping temporary tables, INTVAR, RAND, or USER_VAR events, and non-row-based events within a DML transaction. mysqlbinlog also prints a SET @@session.require_row_format statement at the start of its output to apply the restrictions when the output is executed, and does not print the SET @@session.pseudo_thread_id statement. • --rewrite-db='from_name->to_name' ┌────────────────────┬─────────────────────────────────┐ │Command-Line Format │ --rewrite-db='oldname->newname' │ ├────────────────────┼─────────────────────────────────┤ │Type │ String │ ├────────────────────┼─────────────────────────────────┤ │Default Value │ [none] │ └────────────────────┴─────────────────────────────────┘ When reading from a row-based or statement-based log, rewrite all occurrences of from_name to to_name. Rewriting is done on the rows, for row-based logs, as well as on the USE clauses, for statement-based logs. Warning Statements in which table names are qualified with database names are not rewritten to use the new name when using this option. The rewrite rule employed as a value for this option is a string having the form 'from_name->to_name', as shown previously, and for this reason must be enclosed by quotation marks. To employ multiple rewrite rules, specify the option multiple times, as shown here: mysqlbinlog --rewrite-db='dbcurrent->dbold' --rewrite-db='dbtest->dbcurrent' \ binlog.00001 > /tmp/statements.sql When used together with the --database option, the --rewrite-db option is applied first; then --database option is applied, using the rewritten database name. The order in which the options are provided makes no difference in this regard. This means that, for example, if mysqlbinlog is started with --rewrite-db='mydb->yourdb' --database=yourdb, then all updates to any tables in databases mydb and yourdb are included in the output. On the other hand, if it is started with --rewrite-db='mydb->yourdb' --database=mydb, then mysqlbinlog outputs no statements at all: since all updates to mydb are first rewritten as updates to yourdb before applying the --database option, there remain no updates that match --database=mydb. • --server-id=id ┌────────────────────┬────────────────┐ │Command-Line Format │ --server-id=id │ ├────────────────────┼────────────────┤ │Type │ Numeric │ └────────────────────┴────────────────┘ Display only those events created by the server having the given server ID. • --server-id-bits=N ┌────────────────────┬────────────────────┐ │Command-Line Format │ --server-id-bits=# │ ├────────────────────┼────────────────────┤ │Type │ Numeric │ ├────────────────────┼────────────────────┤ │Default Value │ 32 │ ├────────────────────┼────────────────────┤ │Minimum Value │ 7 │ ├────────────────────┼────────────────────┤ │Maximum Value │ 32 │ └────────────────────┴────────────────────┘ Use only the first N bits of the server_id to identify the server. If the binary log was written by a mysqld with server-id-bits set to less than 32 and user data stored in the most significant bit, running mysqlbinlog with --server-id-bits set to 32 enables this data to be seen. This option is supported only by the version of mysqlbinlog supplied with the NDB Cluster distribution, or built with NDB Cluster support. • --server-public-key-path=file_name ┌────────────────────┬────────────────────────────────────┐ │Command-Line Format │ --server-public-key-path=file_name │ ├────────────────────┼────────────────────────────────────┤ │Type │ File name │ └────────────────────┴────────────────────────────────────┘ The path name to a file in PEM format containing a client-side copy of the public key required by the server for RSA key pair-based password exchange. This option applies to clients that authenticate with the sha256_password or caching_sha2_password authentication plugin. This option is ignored for accounts that do not authenticate with one of those plugins. It is also ignored if RSA-based password exchange is not used, as is the case when the client connects to the server using a secure connection. If --server-public-key-path=file_name is given and specifies a valid public key file, it takes precedence over --get-server-public-key. For sha256_password, this option applies only if MySQL was built using OpenSSL. For information about the sha256_password and caching_sha2_password plugins, see Section 6.4.1.3, “SHA-256 Pluggable Authentication”, and Section 6.4.1.2, “Caching SHA-2 Pluggable Authentication”. • --set-charset=charset_name ┌────────────────────┬────────────────────────────┐ │Command-Line Format │ --set-charset=charset_name │ ├────────────────────┼────────────────────────────┤ │Type │ String │ └────────────────────┴────────────────────────────┘ Add a SET NAMES charset_name statement to the output to specify the character set to be used for processing log files. • --shared-memory-base-name=name ┌────────────────────┬────────────────────────────────┐ │Command-Line Format │ --shared-memory-base-name=name │ ├────────────────────┼────────────────────────────────┤ │Platform Specific │ Windows │ └────────────────────┴────────────────────────────────┘ On Windows, the shared-memory name to use for connections made using shared memory to a local server. The default value is MYSQL. The shared-memory name is case-sensitive. This option applies only if the server was started with the shared_memory system variable enabled to support shared-memory connections. • --short-form, -s ┌────────────────────┬──────────────┐ │Command-Line Format │ --short-form │ └────────────────────┴──────────────┘ Display only the statements contained in the log, without any extra information or row-based events. This is for testing only, and should not be used in production systems. It is deprecated, and you should expect it to be removed in a future release. • --skip-gtids[=(true|false)] ┌────────────────────┬───────────────────────────┐ │Command-Line Format │ --skip-gtids[=true|false] │ ├────────────────────┼───────────────────────────┤ │Type │ Boolean │ ├────────────────────┼───────────────────────────┤ │Default Value │ false │ └────────────────────┴───────────────────────────┘ Do not include the GTIDs from the binary log files in the output dump file. For example: mysqlbinlog --skip-gtids binlog.000001 > /tmp/dump.sql mysql -u root -p -e "source /tmp/dump.sql" You should not normally use this option in production or in recovery, except in the specific, and rare, scenarios where the GTIDs are actively unwanted. For example, an administrator might want to duplicate selected transactions (such as table definitions) from a deployment to another, unrelated, deployment that will not replicate to or from the original. In that scenario, --skip-gtids can be used to enable the administrator to apply the transactions as if they were new, and ensure that the deployments remain unrelated. However, you should only use this option if the inclusion of the GTIDs causes a known issue for your use case. • --socket=path, -S path ┌────────────────────┬────────────────────────────────┐ │Command-Line Format │ --socket={file_name|pipe_name} │ ├────────────────────┼────────────────────────────────┤ │Type │ String │ └────────────────────┴────────────────────────────────┘ For connections to localhost, the Unix socket file to use, or, on Windows, the name of the named pipe to use. On Windows, this option applies only if the server was started with the named_pipe system variable enabled to support named-pipe connections. In addition, the user making the connection must be a member of the Windows group specified by the named_pipe_full_access_group system variable. • --ssl* Options that begin with --ssl specify whether to connect to the server using encryption and indicate where to find SSL keys and certificates. See the section called “Command Options for Encrypted Connections”. • --ssl-fips-mode={OFF|ON|STRICT} ┌────────────────────┬─────────────────────────────────┐ │Command-Line Format │ --ssl-fips-mode={OFF|ON|STRICT} │ ├────────────────────┼─────────────────────────────────┤ │Deprecated │ Yes │ ├────────────────────┼─────────────────────────────────┤ │Type │ Enumeration │ ├────────────────────┼─────────────────────────────────┤ │Default Value │ OFF │ ├────────────────────┼─────────────────────────────────┤ │Valid Values │ OFF ON STRICT │ └────────────────────┴─────────────────────────────────┘ Controls whether to enable FIPS mode on the client side. The --ssl-fips-mode option differs from other --ssl-xxx options in that it is not used to establish encrypted connections, but rather to affect which cryptographic operations to permit. See Section 6.8, “FIPS Support”. These --ssl-fips-mode values are permitted: • OFF: Disable FIPS mode. • ON: Enable FIPS mode. • STRICT: Enable “strict” FIPS mode. Note If the OpenSSL FIPS Object Module is not available, the only permitted value for --ssl-fips-mode is OFF. In this case, setting --ssl-fips-mode to ON or STRICT causes the client to produce a warning at startup and to operate in non-FIPS mode. This option is deprecated. Expect it to be removed in a future version of MySQL. • --start-datetime=datetime ┌────────────────────┬───────────────────────────┐ │Command-Line Format │ --start-datetime=datetime │ ├────────────────────┼───────────────────────────┤ │Type │ Datetime │ └────────────────────┴───────────────────────────┘ Start reading the binary log at the first event having a timestamp equal to or later than the datetime argument. The datetime value is relative to the local time zone on the machine where you run mysqlbinlog. The value should be in a format accepted for the DATETIME or TIMESTAMP data types. For example: mysqlbinlog --start-datetime="2005-12-25 11:25:56" binlog.000003 This option is useful for point-in-time recovery. See Section 7.5, “Point-in-Time (Incremental) Recovery”. • --start-position=N, -j N ┌────────────────────┬────────────────────┐ │Command-Line Format │ --start-position=# │ ├────────────────────┼────────────────────┤ │Type │ Numeric │ └────────────────────┴────────────────────┘ Start decoding the binary log at the log position N, including in the output any events that begin at position N or after. The position is a byte point in the log file, not an event counter; it needs to point to the starting position of an event to generate useful output. This option applies to the first log file named on the command line. Prior to MySQL 8.0.33, the maximum value supported for this option was 4294967295 (232-1). In MySQL 8.0.33 and later, it is 18446744073709551616 (264-1), unless --read-from-remote-server or --read-from-remote-source is also used, in which case the maximum is 4294967295. This option is useful for point-in-time recovery. See Section 7.5, “Point-in-Time (Incremental) Recovery”. • --stop-datetime=datetime ┌────────────────────┬──────────────────────────┐ │Command-Line Format │ --stop-datetime=datetime │ └────────────────────┴──────────────────────────┘ Stop reading the binary log at the first event having a timestamp equal to or later than the datetime argument. See the description of the --start-datetime option for information about the datetime value. This option is useful for point-in-time recovery. See Section 7.5, “Point-in-Time (Incremental) Recovery”. • --stop-never ┌────────────────────┬──────────────┐ │Command-Line Format │ --stop-never │ ├────────────────────┼──────────────┤ │Type │ Boolean │ ├────────────────────┼──────────────┤ │Default Value │ FALSE │ └────────────────────┴──────────────┘ This option is used with --read-from-remote-server. It tells mysqlbinlog to remain connected to the server. Otherwise mysqlbinlog exits when the last log file has been transferred from the server. --stop-never implies --to-last-log, so only the first log file to transfer need be named on the command line. --stop-never is commonly used with --raw to make a live binary log backup, but also can be used without --raw to maintain a continuous text display of log events as the server generates them. With --stop-never, by default, mysqlbinlog reports a server ID of 1 when it connects to the server. Use --connection-server-id to explicitly specify an alternative ID to report. It can be used to avoid a conflict with the ID of a replica server or another mysqlbinlog process. See the section called “SPECIFYING THE MYSQLBINLOG SERVER ID”. • --stop-never-slave-server-id=id ┌────────────────────┬────────────────────────────────┐ │Command-Line Format │ --stop-never-slave-server-id=# │ ├────────────────────┼────────────────────────────────┤ │Type │ Numeric │ ├────────────────────┼────────────────────────────────┤ │Default Value │ 65535 │ ├────────────────────┼────────────────────────────────┤ │Minimum Value │ 1 │ └────────────────────┴────────────────────────────────┘ This option is deprecated; expect it to be removed in a future release. Use the --connection-server-id option instead to specify a server ID for mysqlbinlog to report. • --stop-position=N ┌────────────────────┬───────────────────┐ │Command-Line Format │ --stop-position=# │ ├────────────────────┼───────────────────┤ │Type │ Numeric │ └────────────────────┴───────────────────┘ Stop decoding the binary log at the log position N, excluding from the output any events that begin at position N or after. The position is a byte point in the log file, not an event counter; it needs to point to a spot after the starting position of the last event you want to include in the output. The event starting before position N and finishing at or after the position is the last event to be processed. This option applies to the last log file named on the command line. This option is useful for point-in-time recovery. See Section 7.5, “Point-in-Time (Incremental) Recovery”. • --tls-ciphersuites=ciphersuite_list ┌────────────────────┬─────────────────────────────────────┐ │Command-Line Format │ --tls-ciphersuites=ciphersuite_list │ ├────────────────────┼─────────────────────────────────────┤ │Type │ String │ └────────────────────┴─────────────────────────────────────┘ The permissible ciphersuites for encrypted connections that use TLSv1.3. The value is a list of one or more colon-separated ciphersuite names. The ciphersuites that can be named for this option depend on the SSL library used to compile MySQL. For details, see Section 6.3.2, “Encrypted Connection TLS Protocols and Ciphers”. • --tls-sni-servername=server_name ┌────────────────────┬──────────────────────────────────┐ │Command-Line Format │ --tls-sni-servername=server_name │ ├────────────────────┼──────────────────────────────────┤ │Type │ String │ └────────────────────┴──────────────────────────────────┘ When specified, the name is passed to the libmysqlclient C API library using the MYSQL_OPT_TLS_SNI_SERVERNAME option of mysql_options(). The server name is not case-sensitive. To show which server name the client specified for the current session, if any, check the Tls_sni_server_name status variable. Server Name Indication (SNI) is an extension to the TLS protocol (OpenSSL must be compiled using TLS extensions for this option to function). The MySQL implementation of SNI represents the client-side only. • --tls-version=protocol_list ┌────────────────────┬───────────────────────────────┐ │Command-Line Format │ --tls-version=protocol_list │ ├────────────────────┼───────────────────────────────┤ │Type │ String │ ├────────────────────┼───────────────────────────────┤ │Default Value │ TLSv1,TLSv1.1,TLSv1.2,TLSv1.3 │ │ │ (OpenSSL 1.1.1 or higher) │ │ │ TLSv1,TLSv1.1,TLSv1.2 │ │ │ (otherwise) │ └────────────────────┴───────────────────────────────┘ The permissible TLS protocols for encrypted connections. The value is a list of one or more comma-separated protocol names. The protocols that can be named for this option depend on the SSL library used to compile MySQL. For details, see Section 6.3.2, “Encrypted Connection TLS Protocols and Ciphers”. • --to-last-log, -t ┌────────────────────┬───────────────┐ │Command-Line Format │ --to-last-log │ └────────────────────┴───────────────┘ Do not stop at the end of the requested binary log from a MySQL server, but rather continue printing until the end of the last binary log. If you send the output to the same MySQL server, this may lead to an endless loop. This option requires --read-from-remote-server. • --user=user_name, -u user_name ┌────────────────────┬───────────────────┐ │Command-Line Format │ --user=user_name, │ ├────────────────────┼───────────────────┤ │Type │ String │ └────────────────────┴───────────────────┘ The user name of the MySQL account to use when connecting to a remote server. If you are using the Rewriter plugin with MySQL 8.0.31 or later, you should grant this user the SKIP_QUERY_REWRITE privilege. • --verbose, -v ┌────────────────────┬───────────┐ │Command-Line Format │ --verbose │ └────────────────────┴───────────┘ Reconstruct row events and display them as commented SQL statements, with table partition information where applicable. If this option is given twice (by passing in either "-vv" or "--verbose --verbose"), the output includes comments to indicate column data types and some metadata, and informational log events such as row query log events if the binlog_rows_query_log_events system variable is set to TRUE. For examples that show the effect of --base64-output and --verbose on row event output, see the section called “MYSQLBINLOG ROW EVENT DISPLAY”. • --verify-binlog-checksum, -c ┌────────────────────┬──────────────────────────┐ │Command-Line Format │ --verify-binlog-checksum │ └────────────────────┴──────────────────────────┘ Verify checksums in binary log files. • --version, -V ┌────────────────────┬───────────┐ │Command-Line Format │ --version │ └────────────────────┴───────────┘ Display version information and exit. • --zstd-compression-level=level ┌────────────────────┬────────────────────────────┐ │Command-Line Format │ --zstd-compression-level=# │ ├────────────────────┼────────────────────────────┤ │Type │ Integer │ └────────────────────┴────────────────────────────┘ The compression level to use for connections to the server that use the zstd compression algorithm. The permitted levels are from 1 to 22, with larger values indicating increasing levels of compression. The default zstd compression level is 3. The compression level setting has no effect on connections that do not use zstd compression. For more information, see Section 4.2.8, “Connection Compression Control”. You can pipe the output of mysqlbinlog into the mysql client to execute the events contained in the binary log. This technique is used to recover from an unexpected exit when you have an old backup (see Section 7.5, “Point-in-Time (Incremental) Recovery”). For example: mysqlbinlog binlog.000001 | mysql -u root -p Or: mysqlbinlog binlog.[0-9]* | mysql -u root -p If the statements produced by mysqlbinlog may contain BLOB values, these may cause problems when mysql processes them. In this case, invoke mysql with the --binary-mode option. You can also redirect the output of mysqlbinlog to a text file instead, if you need to modify the statement log first (for example, to remove statements that you do not want to execute for some reason). After editing the file, execute the statements that it contains by using it as input to the mysql program: mysqlbinlog binlog.000001 > tmpfile ... edit tmpfile ... mysql -u root -p < tmpfile When mysqlbinlog is invoked with the --start-position option, it displays only those events with an offset in the binary log greater than or equal to a given position (the given position must match the start of one event). It also has options to stop and start when it sees an event with a given date and time. This enables you to perform point-in-time recovery using the --stop-datetime option (to be able to say, for example, “roll forward my databases to how they were today at 10:30 a.m.”). Processing multiple files. If you have more than one binary log to execute on the MySQL server, the safe method is to process them all using a single connection to the server. Here is an example that demonstrates what may be unsafe: mysqlbinlog binlog.000001 | mysql -u root -p # DANGER!! mysqlbinlog binlog.000002 | mysql -u root -p # DANGER!! Processing binary logs this way using multiple connections to the server causes problems if the first log file contains a CREATE TEMPORARY TABLE statement and the second log contains a statement that uses the temporary table. When the first mysql process terminates, the server drops the temporary table. When the second mysql process attempts to use the table, the server reports “unknown table.” To avoid problems like this, use a single mysql process to execute the contents of all binary logs that you want to process. Here is one way to do so: mysqlbinlog binlog.000001 binlog.000002 | mysql -u root -p Another approach is to write all the logs to a single file and then process the file: mysqlbinlog binlog.000001 > /tmp/statements.sql mysqlbinlog binlog.000002 >> /tmp/statements.sql mysql -u root -p -e "source /tmp/statements.sql" From MySQL 8.0.12, you can also supply multiple binary log files to mysqlbinlog as streamed input using a shell pipe. An archive of compressed binary log files can be decompressed and provided directly to mysqlbinlog. In this example, binlog-files_1.gz contains multiple binary log files for processing. The pipeline extracts the contents of binlog-files_1.gz, pipes the binary log files to mysqlbinlog as standard input, and pipes the output of mysqlbinlog into the mysql client for execution: gzip -cd binlog-files_1.gz | ./mysqlbinlog - | ./mysql -uroot -p You can specify more than one archive file, for example: gzip -cd binlog-files_1.gz binlog-files_2.gz | ./mysqlbinlog - | ./mysql -uroot -p For streamed input, do not use --stop-position, because mysqlbinlog cannot identify the last log file to apply this option. LOAD DATA operations. mysqlbinlog can produce output that reproduces a LOAD DATA operation without the original data file. mysqlbinlog copies the data to a temporary file and writes a LOAD DATA LOCAL statement that refers to the file. The default location of the directory where these files are written is system-specific. To specify a directory explicitly, use the --local-load option. Because mysqlbinlog converts LOAD DATA statements to LOAD DATA LOCAL statements (that is, it adds LOCAL), both the client and the server that you use to process the statements must be configured with the LOCAL capability enabled. See Section 6.1.6, “Security Considerations for LOAD DATA LOCAL”. Warning The temporary files created for LOAD DATA LOCAL statements are not automatically deleted because they are needed until you actually execute those statements. You should delete the temporary files yourself after you no longer need the statement log. The files can be found in the temporary file directory and have names like original_file_name-#-#. MYSQLBINLOG HEX DUMP FORMAT The --hexdump option causes mysqlbinlog to produce a hex dump of the binary log contents: mysqlbinlog --hexdump source-bin.000001 The hex output consists of comment lines beginning with #, so the output might look like this for the preceding command: /*!40019 SET @@SESSION.max_insert_delayed_threads=0*/; /*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/; # at 4 #051024 17:24:13 server id 1 end_log_pos 98 # Position Timestamp Type Master ID Size Master Pos Flags # 00000004 9d fc 5c 43 0f 01 00 00 00 5e 00 00 00 62 00 00 00 00 00 # 00000017 04 00 35 2e 30 2e 31 35 2d 64 65 62 75 67 2d 6c |..5.0.15.debug.l| # 00000027 6f 67 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |og..............| # 00000037 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| # 00000047 00 00 00 00 9d fc 5c 43 13 38 0d 00 08 00 12 00 |.......C.8......| # 00000057 04 04 04 04 12 00 00 4b 00 04 1a |.......K...| # Start: binlog v 4, server v 5.0.15-debug-log created 051024 17:24:13 # at startup ROLLBACK; Hex dump output currently contains the elements in the following list. This format is subject to change. For more information about binary log format, see MySQL Internals: The Binary Log[1]. • Position: The byte position within the log file. • Timestamp: The event timestamp. In the example shown, '9d fc 5c 43' is the representation of '051024 17:24:13' in hexadecimal. • Type: The event type code. • Master ID: The server ID of the replication source server that created the event. • Size: The size in bytes of the event. • Master Pos: The position of the next event in the original source's binary log file. • Flags: Event flag values. MYSQLBINLOG ROW EVENT DISPLAY The following examples illustrate how mysqlbinlog displays row events that specify data modifications. These correspond to events with the WRITE_ROWS_EVENT, UPDATE_ROWS_EVENT, and DELETE_ROWS_EVENT type codes. The --base64-output=DECODE-ROWS and --verbose options may be used to affect row event output. Suppose that the server is using row-based binary logging and that you execute the following sequence of statements: CREATE TABLE t ( id INT NOT NULL, name VARCHAR(20) NOT NULL, date DATE NULL ) ENGINE = InnoDB; START TRANSACTION; INSERT INTO t VALUES(1, 'apple', NULL); UPDATE t SET name = 'pear', date = '2009-01-01' WHERE id = 1; DELETE FROM t WHERE id = 1; COMMIT; By default, mysqlbinlog displays row events encoded as base-64 strings using BINLOG statements. Omitting extraneous lines, the output for the row events produced by the preceding statement sequence looks like this: $> mysqlbinlog log_file ... # at 218 #080828 15:03:08 server id 1 end_log_pos 258 Write_rows: table id 17 flags: STMT_END_F BINLOG ' fAS3SBMBAAAALAAAANoAAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ= fAS3SBcBAAAAKAAAAAIBAAAQABEAAAAAAAEAA//8AQAAAAVhcHBsZQ== '/*!*/; ... # at 302 #080828 15:03:08 server id 1 end_log_pos 356 Update_rows: table id 17 flags: STMT_END_F BINLOG ' fAS3SBMBAAAALAAAAC4BAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ= fAS3SBgBAAAANgAAAGQBAAAQABEAAAAAAAEAA////AEAAAAFYXBwbGX4AQAAAARwZWFyIbIP '/*!*/; ... # at 400 #080828 15:03:08 server id 1 end_log_pos 442 Delete_rows: table id 17 flags: STMT_END_F BINLOG ' fAS3SBMBAAAALAAAAJABAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ= fAS3SBkBAAAAKgAAALoBAAAQABEAAAAAAAEAA//4AQAAAARwZWFyIbIP '/*!*/; To see the row events as comments in the form of “pseudo-SQL” statements, run mysqlbinlog with the --verbose or -v option. This output level also shows table partition information where applicable. The output contains lines beginning with ###: $> mysqlbinlog -v log_file ... # at 218 #080828 15:03:08 server id 1 end_log_pos 258 Write_rows: table id 17 flags: STMT_END_F BINLOG ' fAS3SBMBAAAALAAAANoAAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ= fAS3SBcBAAAAKAAAAAIBAAAQABEAAAAAAAEAA//8AQAAAAVhcHBsZQ== '/*!*/; ### INSERT INTO test.t ### SET ### @1=1 ### @2='apple' ### @3=NULL ... # at 302 #080828 15:03:08 server id 1 end_log_pos 356 Update_rows: table id 17 flags: STMT_END_F BINLOG ' fAS3SBMBAAAALAAAAC4BAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ= fAS3SBgBAAAANgAAAGQBAAAQABEAAAAAAAEAA////AEAAAAFYXBwbGX4AQAAAARwZWFyIbIP '/*!*/; ### UPDATE test.t ### WHERE ### @1=1 ### @2='apple' ### @3=NULL ### SET ### @1=1 ### @2='pear' ### @3='2009:01:01' ... # at 400 #080828 15:03:08 server id 1 end_log_pos 442 Delete_rows: table id 17 flags: STMT_END_F BINLOG ' fAS3SBMBAAAALAAAAJABAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ= fAS3SBkBAAAAKgAAALoBAAAQABEAAAAAAAEAA//4AQAAAARwZWFyIbIP '/*!*/; ### DELETE FROM test.t ### WHERE ### @1=1 ### @2='pear' ### @3='2009:01:01' Specify --verbose or -v twice to also display data types and some metadata for each column, and informational log events such as row query log events if the binlog_rows_query_log_events system variable is set to TRUE. The output contains an additional comment following each column change: $> mysqlbinlog -vv log_file ... # at 218 #080828 15:03:08 server id 1 end_log_pos 258 Write_rows: table id 17 flags: STMT_END_F BINLOG ' fAS3SBMBAAAALAAAANoAAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ= fAS3SBcBAAAAKAAAAAIBAAAQABEAAAAAAAEAA//8AQAAAAVhcHBsZQ== '/*!*/; ### INSERT INTO test.t ### SET ### @1=1 /* INT meta=0 nullable=0 is_null=0 */ ### @2='apple' /* VARSTRING(20) meta=20 nullable=0 is_null=0 */ ### @3=NULL /* VARSTRING(20) meta=0 nullable=1 is_null=1 */ ... # at 302 #080828 15:03:08 server id 1 end_log_pos 356 Update_rows: table id 17 flags: STMT_END_F BINLOG ' fAS3SBMBAAAALAAAAC4BAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ= fAS3SBgBAAAANgAAAGQBAAAQABEAAAAAAAEAA////AEAAAAFYXBwbGX4AQAAAARwZWFyIbIP '/*!*/; ### UPDATE test.t ### WHERE ### @1=1 /* INT meta=0 nullable=0 is_null=0 */ ### @2='apple' /* VARSTRING(20) meta=20 nullable=0 is_null=0 */ ### @3=NULL /* VARSTRING(20) meta=0 nullable=1 is_null=1 */ ### SET ### @1=1 /* INT meta=0 nullable=0 is_null=0 */ ### @2='pear' /* VARSTRING(20) meta=20 nullable=0 is_null=0 */ ### @3='2009:01:01' /* DATE meta=0 nullable=1 is_null=0 */ ... # at 400 #080828 15:03:08 server id 1 end_log_pos 442 Delete_rows: table id 17 flags: STMT_END_F BINLOG ' fAS3SBMBAAAALAAAAJABAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ= fAS3SBkBAAAAKgAAALoBAAAQABEAAAAAAAEAA//4AQAAAARwZWFyIbIP '/*!*/; ### DELETE FROM test.t ### WHERE ### @1=1 /* INT meta=0 nullable=0 is_null=0 */ ### @2='pear' /* VARSTRING(20) meta=20 nullable=0 is_null=0 */ ### @3='2009:01:01' /* DATE meta=0 nullable=1 is_null=0 */ You can tell mysqlbinlog to suppress the BINLOG statements for row events by using the --base64-output=DECODE-ROWS option. This is similar to --base64-output=NEVER but does not exit with an error if a row event is found. The combination of --base64-output=DECODE-ROWS and --verbose provides a convenient way to see row events only as SQL statements: $> mysqlbinlog -v --base64-output=DECODE-ROWS log_file ... # at 218 #080828 15:03:08 server id 1 end_log_pos 258 Write_rows: table id 17 flags: STMT_END_F ### INSERT INTO test.t ### SET ### @1=1 ### @2='apple' ### @3=NULL ... # at 302 #080828 15:03:08 server id 1 end_log_pos 356 Update_rows: table id 17 flags: STMT_END_F ### UPDATE test.t ### WHERE ### @1=1 ### @2='apple' ### @3=NULL ### SET ### @1=1 ### @2='pear' ### @3='2009:01:01' ... # at 400 #080828 15:03:08 server id 1 end_log_pos 442 Delete_rows: table id 17 flags: STMT_END_F ### DELETE FROM test.t ### WHERE ### @1=1 ### @2='pear' ### @3='2009:01:01' Note You should not suppress BINLOG statements if you intend to re-execute mysqlbinlog output. The SQL statements produced by --verbose for row events are much more readable than the corresponding BINLOG statements. However, they do not correspond exactly to the original SQL statements that generated the events. The following limitations apply: • The original column names are lost and replaced by @N, where N is a column number. • Character set information is not available in the binary log, which affects string column display: • There is no distinction made between corresponding binary and nonbinary string types (BINARY and CHAR, VARBINARY and VARCHAR, BLOB and TEXT). The output uses a data type of STRING for fixed-length strings and VARSTRING for variable-length strings. • For multibyte character sets, the maximum number of bytes per character is not present in the binary log, so the length for string types is displayed in bytes rather than in characters. For example, STRING(4) is used as the data type for values from either of these column types: CHAR(4) CHARACTER SET latin1 CHAR(2) CHARACTER SET ucs2 • Due to the storage format for events of type UPDATE_ROWS_EVENT, UPDATE statements are displayed with the WHERE clause preceding the SET clause. Proper interpretation of row events requires the information from the format description event at the beginning of the binary log. Because mysqlbinlog does not know in advance whether the rest of the log contains row events, by default it displays the format description event using a BINLOG statement in the initial part of the output. If the binary log is known not to contain any events requiring a BINLOG statement (that is, no row events), the --base64-output=NEVER option can be used to prevent this header from being written. USING MYSQLBINLOG TO BACK UP BINARY LOG FILES By default, mysqlbinlog reads binary log files and displays their contents in text format. This enables you to examine events within the files more easily and to re-execute them (for example, by using the output as input to mysql). mysqlbinlog can read log files directly from the local file system, or, with the --read-from-remote-server option, it can connect to a server and request binary log contents from that server. mysqlbinlog writes text output to its standard output, or to the file named as the value of the --result-file=file_name option if that option is given. • mysqlbinlog Backup Capabilities • mysqlbinlog Backup Options • Static and Live Backups • Output File Naming • Example: mysqldump + mysqlbinlog for Backup and Restore • mysqlbinlog Backup Restrictions mysqlbinlog Backup Capabilities mysqlbinlog can read binary log files and write new files containing the same content—that is, in binary format rather than text format. This capability enables you to easily back up a binary log in its original format. mysqlbinlog can make a static backup, backing up a set of log files and stopping when the end of the last file is reached. It can also make a continuous (“live”) backup, staying connected to the server when it reaches the end of the last log file and continuing to copy new events as they are generated. In continuous-backup operation, mysqlbinlog runs until the connection ends (for example, when the server exits) or mysqlbinlog is forcibly terminated. When the connection ends, mysqlbinlog does not wait and retry the connection, unlike a replica server. To continue a live backup after the server has been restarted, you must also restart mysqlbinlog. Important mysqlbinlog can back up both encrypted and unencrypted binary log files . However, copies of encrypted binary log files that are generated using mysqlbinlog are stored in an unencrypted format. mysqlbinlog Backup Options Binary log backup requires that you invoke mysqlbinlog with two options at minimum: • The --read-from-remote-server (or -R) option tells mysqlbinlog to connect to a server and request its binary log. (This is similar to a replica server connecting to its replication source server.) • The --raw option tells mysqlbinlog to write raw (binary) output, not text output. Along with --read-from-remote-server, it is common to specify other options: --host indicates where the server is running, and you may also need to specify connection options such as --user and --password. Several other options are useful in conjunction with --raw: • --stop-never: Stay connected to the server after reaching the end of the last log file and continue to read new events. • --connection-server-id=id: The server ID that mysqlbinlog reports when it connects to a server. When --stop-never is used, the default reported server ID is 1. If this causes a conflict with the ID of a replica server or another mysqlbinlog process, use --connection-server-id to specify an alternative server ID. See the section called “SPECIFYING THE MYSQLBINLOG SERVER ID”. • --result-file: A prefix for output file names, as described later. Static and Live Backups To back up a server's binary log files with mysqlbinlog, you must specify file names that actually exist on the server. If you do not know the names, connect to the server and use the SHOW BINARY LOGS statement to see the current names. Suppose that the statement produces this output: mysql> SHOW BINARY LOGS; +---------------+-----------+-----------+ | Log_name | File_size | Encrypted | +---------------+-----------+-----------+ | binlog.000130 | 27459 | No | | binlog.000131 | 13719 | No | | binlog.000132 | 43268 | No | +---------------+-----------+-----------+ With that information, you can use mysqlbinlog to back up the binary log to the current directory as follows (enter each command on a single line): • To make a static backup of binlog.000130 through binlog.000132, use either of these commands: mysqlbinlog --read-from-remote-server --host=host_name --raw binlog.000130 binlog.000131 binlog.000132 mysqlbinlog --read-from-remote-server --host=host_name --raw --to-last-log binlog.000130 The first command specifies every file name explicitly. The second names only the first file and uses --to-last-log to read through the last. A difference between these commands is that if the server happens to open binlog.000133 before mysqlbinlog reaches the end of binlog.000132, the first command does not read it, but the second command does. • To make a live backup in which mysqlbinlog starts with binlog.000130 to copy existing log files, then stays connected to copy new events as the server generates them: mysqlbinlog --read-from-remote-server --host=host_name --raw --stop-never binlog.000130 With --stop-never, it is not necessary to specify --to-last-log to read to the last log file because that option is implied. Output File Naming Without --raw, mysqlbinlog produces text output and the --result-file option, if given, specifies the name of the single file to which all output is written. With --raw, mysqlbinlog writes one binary output file for each log file transferred from the server. By default, mysqlbinlog writes the files in the current directory with the same names as the original log files. To modify the output file names, use the --result-file option. In conjunction with --raw, the --result-file option value is treated as a prefix that modifies the output file names. Suppose that a server currently has binary log files named binlog.000999 and up. If you use mysqlbinlog --raw to back up the files, the --result-file option produces output file names as shown in the following table. You can write the files to a specific directory by beginning the --result-file value with the directory path. If the --result-file value consists only of a directory name, the value must end with the pathname separator character. Output files are overwritten if they exist. ┌─────────────────────┬────────────────────────────┐ │--result-file Option │ Output File Names │ ├─────────────────────┼────────────────────────────┤ │--result-file=x │ xbinlog.000999 and up │ ├─────────────────────┼────────────────────────────┤ │--result-file=/tmp/ │ /tmp/binlog.000999 and up │ ├─────────────────────┼────────────────────────────┤ │--result-file=/tmp/x │ /tmp/xbinlog.000999 and up │ └─────────────────────┴────────────────────────────┘ Example: mysqldump + mysqlbinlog for Backup and Restore The following example describes a simple scenario that shows how to use mysqldump and mysqlbinlog together to back up a server's data and binary log, and how to use the backup to restore the server if data loss occurs. The example assumes that the server is running on host host_name and its first binary log file is named binlog.000999. Enter each command on a single line. Use mysqlbinlog to make a continuous backup of the binary log: mysqlbinlog --read-from-remote-server --host=host_name --raw --stop-never binlog.000999 Use mysqldump to create a dump file as a snapshot of the server's data. Use --all-databases, --events, and --routines to back up all data, and --source-data=2 to include the current binary log coordinates in the dump file. mysqldump --host=host_name --all-databases --events --routines --source-data=2> dump_file Execute the mysqldump command periodically to create newer snapshots as desired. If data loss occurs (for example, if the server unexpectedly exits), use the most recent dump file to restore the data: mysql --host=host_name -u root -p < dump_file Then use the binary log backup to re-execute events that were written after the coordinates listed in the dump file. Suppose that the coordinates in the file look like this: -- CHANGE REPLICATION SOURCE TO SOURCE_LOG_FILE='binlog.001002', SOURCE_LOG_POS=27284; If the most recent backed-up log file is named binlog.001004, re-execute the log events like this: mysqlbinlog --start-position=27284 binlog.001002 binlog.001003 binlog.001004 | mysql --host=host_name -u root -p You might find it easier to copy the backup files (dump file and binary log files) to the server host to make it easier to perform the restore operation, or if MySQL does not allow remote root access. mysqlbinlog Backup Restrictions Binary log backups with mysqlbinlog are subject to these restrictions: • mysqlbinlog does not automatically reconnect to the MySQL server if the connection is lost (for example, if a server restart occurs or there is a network outage). • The delay for a backup is similar to the delay for a replica server. SPECIFYING THE MYSQLBINLOG SERVER ID When invoked with the --read-from-remote-server option, mysqlbinlog connects to a MySQL server, specifies a server ID to identify itself, and requests binary log files from the server. You can use mysqlbinlog to request log files from a server in several ways: • Specify an explicitly named set of files: For each file, mysqlbinlog connects and issues a Binlog dump command. The server sends the file and disconnects. There is one connection per file. • Specify the beginning file and --to-last-log: mysqlbinlog connects and issues a Binlog dump command for all files. The server sends all files and disconnects. • Specify the beginning file and --stop-never (which implies --to-last-log): mysqlbinlog connects and issues a Binlog dump command for all files. The server sends all files, but does not disconnect after sending the last one. With --read-from-remote-server only, mysqlbinlog connects using a server ID of 0, which tells the server to disconnect after sending the last requested log file. With --read-from-remote-server and --stop-never, mysqlbinlog connects using a nonzero server ID, so the server does not disconnect after sending the last log file. The server ID is 1 by default, but this can be changed with --connection-server-id. Thus, for the first two ways of requesting files, the server disconnects because mysqlbinlog specifies a server ID of 0. It does not disconnect if --stop-never is given because mysqlbinlog specifies a nonzero server ID. COPYRIGHT Copyright © 1997, 2023, Oracle and/or its affiliates. This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with the program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/. NOTES 1. MySQL Internals: The Binary Log https://dev.mysql.com/doc/internals/en/binary-log.html SEE ALSO For more information, please refer to the MySQL Reference Manual, which may already be installed locally and which is also available online at http://dev.mysql.com/doc/. AUTHOR Oracle Corporation (http://dev.mysql.com/). MySQL 8.3 11/23/2023 MYSQLBINLOG(1)
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mysqlbinlog - utility for processing binary log files
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mysqlbinlog [options] log_file ...
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pzstd
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pear
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pyrsa-sign
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protoc-gen-upb_minitable-27.1.0
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onnxruntime_test
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grealpath
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Print the resolved absolute file name; all but the last component must exist -e, --canonicalize-existing all components of the path must exist -m, --canonicalize-missing no path components need exist or be a directory -L, --logical resolve '..' components before symlinks -P, --physical resolve symlinks as encountered (default) -q, --quiet suppress most error messages --relative-to=DIR print the resolved path relative to DIR --relative-base=DIR print absolute paths unless paths below DIR -s, --strip, --no-symlinks don't expand symlinks -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit AUTHOR Written by Padraig Brady. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO readlink(1), readlink(2), realpath(3) Full documentation <https://www.gnu.org/software/coreutils/realpath> or available locally via: info '(coreutils) realpath invocation' GNU coreutils 9.3 April 2023 REALPATH(1)
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realpath - print the resolved path
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realpath [OPTION]... FILE...
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ocspresp
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ffmpeg
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ffmpeg is a universal media converter. It can read a wide variety of inputs - including live grabbing/recording devices - filter, and transcode them into a plethora of output formats. ffmpeg reads from an arbitrary number of input "files" (which can be regular files, pipes, network streams, grabbing devices, etc.), specified by the "-i" option, and writes to an arbitrary number of output "files", which are specified by a plain output url. Anything found on the command line which cannot be interpreted as an option is considered to be an output url. Each input or output url can, in principle, contain any number of streams of different types (video/audio/subtitle/attachment/data). The allowed number and/or types of streams may be limited by the container format. Selecting which streams from which inputs will go into which output is either done automatically or with the "-map" option (see the Stream selection chapter). To refer to input files in options, you must use their indices (0-based). E.g. the first input file is 0, the second is 1, etc. Similarly, streams within a file are referred to by their indices. E.g. "2:3" refers to the fourth stream in the third input file. Also see the Stream specifiers chapter. As a general rule, options are applied to the next specified file. Therefore, order is important, and you can have the same option on the command line multiple times. Each occurrence is then applied to the next input or output file. Exceptions from this rule are the global options (e.g. verbosity level), which should be specified first. Do not mix input and output files -- first specify all input files, then all output files. Also do not mix options which belong to different files. All options apply ONLY to the next input or output file and are reset between files. Some simple examples follow. • Convert an input media file to a different format, by re-encoding media streams: ffmpeg -i input.avi output.mp4 • Set the video bitrate of the output file to 64 kbit/s: ffmpeg -i input.avi -b:v 64k -bufsize 64k output.mp4 • Force the frame rate of the output file to 24 fps: ffmpeg -i input.avi -r 24 output.mp4 • Force the frame rate of the input file (valid for raw formats only) to 1 fps and the frame rate of the output file to 24 fps: ffmpeg -r 1 -i input.m2v -r 24 output.mp4 The format option may be needed for raw input files. DETAILED DESCRIPTION The transcoding process in ffmpeg for each output can be described by the following diagram: _______ ______________ | | | | | input | demuxer | encoded data | decoder | file | ---------> | packets | -----+ |_______| |______________| | v _________ | | | decoded | | frames | |_________| ________ ______________ | | | | | | | output | <-------- | encoded data | <----+ | file | muxer | packets | encoder |________| |______________| ffmpeg calls the libavformat library (containing demuxers) to read input files and get packets containing encoded data from them. When there are multiple input files, ffmpeg tries to keep them synchronized by tracking lowest timestamp on any active input stream. Encoded packets are then passed to the decoder (unless streamcopy is selected for the stream, see further for a description). The decoder produces uncompressed frames (raw video/PCM audio/...) which can be processed further by filtering (see next section). After filtering, the frames are passed to the encoder, which encodes them and outputs encoded packets. Finally, those are passed to the muxer, which writes the encoded packets to the output file. Filtering Before encoding, ffmpeg can process raw audio and video frames using filters from the libavfilter library. Several chained filters form a filter graph. ffmpeg distinguishes between two types of filtergraphs: simple and complex. Simple filtergraphs Simple filtergraphs are those that have exactly one input and output, both of the same type. In the above diagram they can be represented by simply inserting an additional step between decoding and encoding: _________ ______________ | | | | | decoded | | encoded data | | frames |\ _ | packets | |_________| \ /||______________| \ __________ / simple _\|| | / encoder filtergraph | filtered |/ | frames | |__________| Simple filtergraphs are configured with the per-stream -filter option (with -vf and -af aliases for video and audio respectively). A simple filtergraph for video can look for example like this: _______ _____________ _______ ________ | | | | | | | | | input | ---> | deinterlace | ---> | scale | ---> | output | |_______| |_____________| |_______| |________| Note that some filters change frame properties but not frame contents. E.g. the "fps" filter in the example above changes number of frames, but does not touch the frame contents. Another example is the "setpts" filter, which only sets timestamps and otherwise passes the frames unchanged. Complex filtergraphs Complex filtergraphs are those which cannot be described as simply a linear processing chain applied to one stream. This is the case, for example, when the graph has more than one input and/or output, or when output stream type is different from input. They can be represented with the following diagram: _________ | | | input 0 |\ __________ |_________| \ | | \ _________ /| output 0 | \ | | / |__________| _________ \| complex | / | | | |/ | input 1 |---->| filter |\ |_________| | | \ __________ /| graph | \ | | / | | \| output 1 | _________ / |_________| |__________| | | / | input 2 |/ |_________| Complex filtergraphs are configured with the -filter_complex option. Note that this option is global, since a complex filtergraph, by its nature, cannot be unambiguously associated with a single stream or file. The -lavfi option is equivalent to -filter_complex. A trivial example of a complex filtergraph is the "overlay" filter, which has two video inputs and one video output, containing one video overlaid on top of the other. Its audio counterpart is the "amix" filter. Stream copy Stream copy is a mode selected by supplying the "copy" parameter to the -codec option. It makes ffmpeg omit the decoding and encoding step for the specified stream, so it does only demuxing and muxing. It is useful for changing the container format or modifying container-level metadata. The diagram above will, in this case, simplify to this: _______ ______________ ________ | | | | | | | input | demuxer | encoded data | muxer | output | | file | ---------> | packets | -------> | file | |_______| |______________| |________| Since there is no decoding or encoding, it is very fast and there is no quality loss. However, it might not work in some cases because of many factors. Applying filters is obviously also impossible, since filters work on uncompressed data. Loopback decoders While decoders are normally associated with demuxer streams, it is also possible to create "loopback" decoders that decode the output from some encoder and allow it to be fed back to complex filtergraphs. This is done with the "-dec" directive, which takes as a parameter the index of the output stream that should be decoded. Every such directive creates a new loopback decoder, indexed with successive integers starting at zero. These indices should then be used to refer to loopback decoders in complex filtergraph link labels, as described in the documentation for -filter_complex. E.g. the following example: ffmpeg -i INPUT \ -map 0:v:0 -c:v libx264 -crf 45 -f null - \ -dec 0:0 -filter_complex '[0:v][dec:0]hstack[stack]' \ -map '[stack]' -c:v ffv1 OUTPUT reads an input video and • (line 2) encodes it with "libx264" at low quality; • (line 3) decodes this encoded stream and places it side by side with the original input video; • (line 4) combined video is then losslessly encoded and written into OUTPUT. STREAM SELECTION ffmpeg provides the "-map" option for manual control of stream selection in each output file. Users can skip "-map" and let ffmpeg perform automatic stream selection as described below. The "-vn / -an / -sn / -dn" options can be used to skip inclusion of video, audio, subtitle and data streams respectively, whether manually mapped or automatically selected, except for those streams which are outputs of complex filtergraphs. The sub-sections that follow describe the various rules that are involved in stream selection. The examples that follow next show how these rules are applied in practice. While every effort is made to accurately reflect the behavior of the program, FFmpeg is under continuous development and the code may have changed since the time of this writing. Automatic stream selection In the absence of any map options for a particular output file, ffmpeg inspects the output format to check which type of streams can be included in it, viz. video, audio and/or subtitles. For each acceptable stream type, ffmpeg will pick one stream, when available, from among all the inputs. It will select that stream based upon the following criteria: • for video, it is the stream with the highest resolution, • for audio, it is the stream with the most channels, • for subtitles, it is the first subtitle stream found but there's a caveat. The output format's default subtitle encoder can be either text-based or image-based, and only a subtitle stream of the same type will be chosen. In the case where several streams of the same type rate equally, the stream with the lowest index is chosen. Data or attachment streams are not automatically selected and can only be included using "-map". Manual stream selection When "-map" is used, only user-mapped streams are included in that output file, with one possible exception for filtergraph outputs described below. Complex filtergraphs If there are any complex filtergraph output streams with unlabeled pads, they will be added to the first output file. This will lead to a fatal error if the stream type is not supported by the output format. In the absence of the map option, the inclusion of these streams leads to the automatic stream selection of their types being skipped. If map options are present, these filtergraph streams are included in addition to the mapped streams. Complex filtergraph output streams with labeled pads must be mapped once and exactly once. Stream handling Stream handling is independent of stream selection, with an exception for subtitles described below. Stream handling is set via the "-codec" option addressed to streams within a specific output file. In particular, codec options are applied by ffmpeg after the stream selection process and thus do not influence the latter. If no "-codec" option is specified for a stream type, ffmpeg will select the default encoder registered by the output file muxer. An exception exists for subtitles. If a subtitle encoder is specified for an output file, the first subtitle stream found of any type, text or image, will be included. ffmpeg does not validate if the specified encoder can convert the selected stream or if the converted stream is acceptable within the output format. This applies generally as well: when the user sets an encoder manually, the stream selection process cannot check if the encoded stream can be muxed into the output file. If it cannot, ffmpeg will abort and all output files will fail to be processed.
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ffmpeg - ffmpeg media converter
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ffmpeg [global_options] {[input_file_options] -i input_url} ... {[output_file_options] output_url} ...
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All the numerical options, if not specified otherwise, accept a string representing a number as input, which may be followed by one of the SI unit prefixes, for example: 'K', 'M', or 'G'. If 'i' is appended to the SI unit prefix, the complete prefix will be interpreted as a unit prefix for binary multiples, which are based on powers of 1024 instead of powers of 1000. Appending 'B' to the SI unit prefix multiplies the value by 8. This allows using, for example: 'KB', 'MiB', 'G' and 'B' as number suffixes. Options which do not take arguments are boolean options, and set the corresponding value to true. They can be set to false by prefixing the option name with "no". For example using "-nofoo" will set the boolean option with name "foo" to false. Options that take arguments support a special syntax where the argument given on the command line is interpreted as a path to the file from which the actual argument value is loaded. To use this feature, add a forward slash '/' immediately before the option name (after the leading dash). E.g. ffmpeg -i INPUT -/filter:v filter.script OUTPUT will load a filtergraph description from the file named filter.script. Stream specifiers Some options are applied per-stream, e.g. bitrate or codec. Stream specifiers are used to precisely specify which stream(s) a given option belongs to. A stream specifier is a string generally appended to the option name and separated from it by a colon. E.g. "-codec:a:1 ac3" contains the "a:1" stream specifier, which matches the second audio stream. Therefore, it would select the ac3 codec for the second audio stream. A stream specifier can match several streams, so that the option is applied to all of them. E.g. the stream specifier in "-b:a 128k" matches all audio streams. An empty stream specifier matches all streams. For example, "-codec copy" or "-codec: copy" would copy all the streams without reencoding. Possible forms of stream specifiers are: stream_index Matches the stream with this index. E.g. "-threads:1 4" would set the thread count for the second stream to 4. If stream_index is used as an additional stream specifier (see below), then it selects stream number stream_index from the matching streams. Stream numbering is based on the order of the streams as detected by libavformat except when a stream group specifier or program ID is also specified. In this case it is based on the ordering of the streams in the group or program. stream_type[:additional_stream_specifier] stream_type is one of following: 'v' or 'V' for video, 'a' for audio, 's' for subtitle, 'd' for data, and 't' for attachments. 'v' matches all video streams, 'V' only matches video streams which are not attached pictures, video thumbnails or cover arts. If additional_stream_specifier is used, then it matches streams which both have this type and match the additional_stream_specifier. Otherwise, it matches all streams of the specified type. g:group_specifier[:additional_stream_specifier] Matches streams which are in the group with the specifier group_specifier. if additional_stream_specifier is used, then it matches streams which both are part of the group and match the additional_stream_specifier. group_specifier may be one of the following: group_index Match the stream with this group index. #group_id or i:group_id Match the stream with this group id. p:program_id[:additional_stream_specifier] Matches streams which are in the program with the id program_id. If additional_stream_specifier is used, then it matches streams which both are part of the program and match the additional_stream_specifier. #stream_id or i:stream_id Match the stream by stream id (e.g. PID in MPEG-TS container). m:key[:value] Matches streams with the metadata tag key having the specified value. If value is not given, matches streams that contain the given tag with any value. u Matches streams with usable configuration, the codec must be defined and the essential information such as video dimension or audio sample rate must be present. Note that in ffmpeg, matching by metadata will only work properly for input files. Generic options These options are shared amongst the ff* tools. -L Show license. -h, -?, -help, --help [arg] Show help. An optional parameter may be specified to print help about a specific item. If no argument is specified, only basic (non advanced) tool options are shown. Possible values of arg are: long Print advanced tool options in addition to the basic tool options. full Print complete list of options, including shared and private options for encoders, decoders, demuxers, muxers, filters, etc. decoder=decoder_name Print detailed information about the decoder named decoder_name. Use the -decoders option to get a list of all decoders. encoder=encoder_name Print detailed information about the encoder named encoder_name. Use the -encoders option to get a list of all encoders. demuxer=demuxer_name Print detailed information about the demuxer named demuxer_name. Use the -formats option to get a list of all demuxers and muxers. muxer=muxer_name Print detailed information about the muxer named muxer_name. Use the -formats option to get a list of all muxers and demuxers. filter=filter_name Print detailed information about the filter named filter_name. Use the -filters option to get a list of all filters. bsf=bitstream_filter_name Print detailed information about the bitstream filter named bitstream_filter_name. Use the -bsfs option to get a list of all bitstream filters. protocol=protocol_name Print detailed information about the protocol named protocol_name. Use the -protocols option to get a list of all protocols. -version Show version. -buildconf Show the build configuration, one option per line. -formats Show available formats (including devices). -demuxers Show available demuxers. -muxers Show available muxers. -devices Show available devices. -codecs Show all codecs known to libavcodec. Note that the term 'codec' is used throughout this documentation as a shortcut for what is more correctly called a media bitstream format. -decoders Show available decoders. -encoders Show all available encoders. -bsfs Show available bitstream filters. -protocols Show available protocols. -filters Show available libavfilter filters. -pix_fmts Show available pixel formats. -sample_fmts Show available sample formats. -layouts Show channel names and standard channel layouts. -dispositions Show stream dispositions. -colors Show recognized color names. -sources device[,opt1=val1[,opt2=val2]...] Show autodetected sources of the input device. Some devices may provide system-dependent source names that cannot be autodetected. The returned list cannot be assumed to be always complete. ffmpeg -sources pulse,server=192.168.0.4 -sinks device[,opt1=val1[,opt2=val2]...] Show autodetected sinks of the output device. Some devices may provide system-dependent sink names that cannot be autodetected. The returned list cannot be assumed to be always complete. ffmpeg -sinks pulse,server=192.168.0.4 -loglevel [flags+]loglevel | -v [flags+]loglevel Set logging level and flags used by the library. The optional flags prefix can consist of the following values: repeat Indicates that repeated log output should not be compressed to the first line and the "Last message repeated n times" line will be omitted. level Indicates that log output should add a "[level]" prefix to each message line. This can be used as an alternative to log coloring, e.g. when dumping the log to file. Flags can also be used alone by adding a '+'/'-' prefix to set/reset a single flag without affecting other flags or changing loglevel. When setting both flags and loglevel, a '+' separator is expected between the last flags value and before loglevel. loglevel is a string or a number containing one of the following values: quiet, -8 Show nothing at all; be silent. panic, 0 Only show fatal errors which could lead the process to crash, such as an assertion failure. This is not currently used for anything. fatal, 8 Only show fatal errors. These are errors after which the process absolutely cannot continue. error, 16 Show all errors, including ones which can be recovered from. warning, 24 Show all warnings and errors. Any message related to possibly incorrect or unexpected events will be shown. info, 32 Show informative messages during processing. This is in addition to warnings and errors. This is the default value. verbose, 40 Same as "info", except more verbose. debug, 48 Show everything, including debugging information. trace, 56 For example to enable repeated log output, add the "level" prefix, and set loglevel to "verbose": ffmpeg -loglevel repeat+level+verbose -i input output Another example that enables repeated log output without affecting current state of "level" prefix flag or loglevel: ffmpeg [...] -loglevel +repeat By default the program logs to stderr. If coloring is supported by the terminal, colors are used to mark errors and warnings. Log coloring can be disabled setting the environment variable AV_LOG_FORCE_NOCOLOR, or can be forced setting the environment variable AV_LOG_FORCE_COLOR. -report Dump full command line and log output to a file named "program-YYYYMMDD-HHMMSS.log" in the current directory. This file can be useful for bug reports. It also implies "-loglevel debug". Setting the environment variable FFREPORT to any value has the same effect. If the value is a ':'-separated key=value sequence, these options will affect the report; option values must be escaped if they contain special characters or the options delimiter ':' (see the ``Quoting and escaping'' section in the ffmpeg-utils manual). The following options are recognized: file set the file name to use for the report; %p is expanded to the name of the program, %t is expanded to a timestamp, "%%" is expanded to a plain "%" level set the log verbosity level using a numerical value (see "-loglevel"). For example, to output a report to a file named ffreport.log using a log level of 32 (alias for log level "info"): FFREPORT=file=ffreport.log:level=32 ffmpeg -i input output Errors in parsing the environment variable are not fatal, and will not appear in the report. -hide_banner Suppress printing banner. All FFmpeg tools will normally show a copyright notice, build options and library versions. This option can be used to suppress printing this information. -cpuflags flags (global) Allows setting and clearing cpu flags. This option is intended for testing. Do not use it unless you know what you're doing. ffmpeg -cpuflags -sse+mmx ... ffmpeg -cpuflags mmx ... ffmpeg -cpuflags 0 ... Possible flags for this option are: x86 mmx mmxext sse sse2 sse2slow sse3 sse3slow ssse3 atom sse4.1 sse4.2 avx avx2 xop fma3 fma4 3dnow 3dnowext bmi1 bmi2 cmov ARM armv5te armv6 armv6t2 vfp vfpv3 neon setend AArch64 armv8 vfp neon PowerPC altivec Specific Processors pentium2 pentium3 pentium4 k6 k62 athlon athlonxp k8 -cpucount count (global) Override detection of CPU count. This option is intended for testing. Do not use it unless you know what you're doing. ffmpeg -cpucount 2 -max_alloc bytes Set the maximum size limit for allocating a block on the heap by ffmpeg's family of malloc functions. Exercise extreme caution when using this option. Don't use if you do not understand the full consequence of doing so. Default is INT_MAX. AVOptions These options are provided directly by the libavformat, libavdevice and libavcodec libraries. To see the list of available AVOptions, use the -help option. They are separated into two categories: generic These options can be set for any container, codec or device. Generic options are listed under AVFormatContext options for containers/devices and under AVCodecContext options for codecs. private These options are specific to the given container, device or codec. Private options are listed under their corresponding containers/devices/codecs. For example to write an ID3v2.3 header instead of a default ID3v2.4 to an MP3 file, use the id3v2_version private option of the MP3 muxer: ffmpeg -i input.flac -id3v2_version 3 out.mp3 All codec AVOptions are per-stream, and thus a stream specifier should be attached to them: ffmpeg -i multichannel.mxf -map 0:v:0 -map 0:a:0 -map 0:a:0 -c:a:0 ac3 -b:a:0 640k -ac:a:1 2 -c:a:1 aac -b:2 128k out.mp4 In the above example, a multichannel audio stream is mapped twice for output. The first instance is encoded with codec ac3 and bitrate 640k. The second instance is downmixed to 2 channels and encoded with codec aac. A bitrate of 128k is specified for it using absolute index of the output stream. Note: the -nooption syntax cannot be used for boolean AVOptions, use -option 0/-option 1. Note: the old undocumented way of specifying per-stream AVOptions by prepending v/a/s to the options name is now obsolete and will be removed soon. Main options -f fmt (input/output) Force input or output file format. The format is normally auto detected for input files and guessed from the file extension for output files, so this option is not needed in most cases. -i url (input) input file url -y (global) Overwrite output files without asking. -n (global) Do not overwrite output files, and exit immediately if a specified output file already exists. -stream_loop number (input) Set number of times input stream shall be looped. Loop 0 means no loop, loop -1 means infinite loop. -recast_media (global) Allow forcing a decoder of a different media type than the one detected or designated by the demuxer. Useful for decoding media data muxed as data streams. -c[:stream_specifier] codec (input/output,per-stream) -codec[:stream_specifier] codec (input/output,per-stream) Select an encoder (when used before an output file) or a decoder (when used before an input file) for one or more streams. codec is the name of a decoder/encoder or a special value "copy" (output only) to indicate that the stream is not to be re-encoded. For example ffmpeg -i INPUT -map 0 -c:v libx264 -c:a copy OUTPUT encodes all video streams with libx264 and copies all audio streams. For each stream, the last matching "c" option is applied, so ffmpeg -i INPUT -map 0 -c copy -c:v:1 libx264 -c:a:137 libvorbis OUTPUT will copy all the streams except the second video, which will be encoded with libx264, and the 138th audio, which will be encoded with libvorbis. -t duration (input/output) When used as an input option (before "-i"), limit the duration of data read from the input file. When used as an output option (before an output url), stop writing the output after its duration reaches duration. duration must be a time duration specification, see the Time duration section in the ffmpeg-utils(1) manual. -to and -t are mutually exclusive and -t has priority. -to position (input/output) Stop writing the output or reading the input at position. position must be a time duration specification, see the Time duration section in the ffmpeg-utils(1) manual. -to and -t are mutually exclusive and -t has priority. -fs limit_size (output) Set the file size limit, expressed in bytes. No further chunk of bytes is written after the limit is exceeded. The size of the output file is slightly more than the requested file size. -ss position (input/output) When used as an input option (before "-i"), seeks in this input file to position. Note that in most formats it is not possible to seek exactly, so ffmpeg will seek to the closest seek point before position. When transcoding and -accurate_seek is enabled (the default), this extra segment between the seek point and position will be decoded and discarded. When doing stream copy or when -noaccurate_seek is used, it will be preserved. When used as an output option (before an output url), decodes but discards input until the timestamps reach position. position must be a time duration specification, see the Time duration section in the ffmpeg-utils(1) manual. -sseof position (input) Like the "-ss" option but relative to the "end of file". That is negative values are earlier in the file, 0 is at EOF. -isync input_index (input) Assign an input as a sync source. This will take the difference between the start times of the target and reference inputs and offset the timestamps of the target file by that difference. The source timestamps of the two inputs should derive from the same clock source for expected results. If "copyts" is set then "start_at_zero" must also be set. If either of the inputs has no starting timestamp then no sync adjustment is made. Acceptable values are those that refer to a valid ffmpeg input index. If the sync reference is the target index itself or -1, then no adjustment is made to target timestamps. A sync reference may not itself be synced to any other input. Default value is -1. -itsoffset offset (input) Set the input time offset. offset must be a time duration specification, see the Time duration section in the ffmpeg-utils(1) manual. The offset is added to the timestamps of the input files. Specifying a positive offset means that the corresponding streams are delayed by the time duration specified in offset. -itsscale scale (input,per-stream) Rescale input timestamps. scale should be a floating point number. -timestamp date (output) Set the recording timestamp in the container. date must be a date specification, see the Date section in the ffmpeg-utils(1) manual. -metadata[:metadata_specifier] key=value (output,per-metadata) Set a metadata key/value pair. An optional metadata_specifier may be given to set metadata on streams, chapters or programs. See "-map_metadata" documentation for details. This option overrides metadata set with "-map_metadata". It is also possible to delete metadata by using an empty value. For example, for setting the title in the output file: ffmpeg -i in.avi -metadata title="my title" out.flv To set the language of the first audio stream: ffmpeg -i INPUT -metadata:s:a:0 language=eng OUTPUT -disposition[:stream_specifier] value (output,per-stream) Sets the disposition for a stream. By default, the disposition is copied from the input stream, unless the output stream this option applies to is fed by a complex filtergraph - in that case the disposition is unset by default. value is a sequence of items separated by '+' or '-'. The first item may also be prefixed with '+' or '-', in which case this option modifies the default value. Otherwise (the first item is not prefixed) this options overrides the default value. A '+' prefix adds the given disposition, '-' removes it. It is also possible to clear the disposition by setting it to 0. If no "-disposition" options were specified for an output file, ffmpeg will automatically set the 'default' disposition on the first stream of each type, when there are multiple streams of this type in the output file and no stream of that type is already marked as default. The "-dispositions" option lists the known dispositions. For example, to make the second audio stream the default stream: ffmpeg -i in.mkv -c copy -disposition:a:1 default out.mkv To make the second subtitle stream the default stream and remove the default disposition from the first subtitle stream: ffmpeg -i in.mkv -c copy -disposition:s:0 0 -disposition:s:1 default out.mkv To add an embedded cover/thumbnail: ffmpeg -i in.mp4 -i IMAGE -map 0 -map 1 -c copy -c:v:1 png -disposition:v:1 attached_pic out.mp4 Not all muxers support embedded thumbnails, and those who do, only support a few formats, like JPEG or PNG. -program [title=title:][program_num=program_num:]st=stream[:st=stream...] (output) Creates a program with the specified title, program_num and adds the specified stream(s) to it. -stream_group type=type:st=stream[:st=stream][:stg=stream_group][:id=stream_group_id...] (output) Creates a stream group of the specified type, stream_group_id and adds the specified stream(s) and/or previously defined stream_group(s) to it. type can be one of the following: iamf_audio_element Groups streams that belong to the same IAMF Audio Element For this group type, the following options are available audio_element_type The Audio Element type. The following values are supported: channel Scalable channel audio representation scene Ambisonics representation demixing Demixing information used to reconstruct a scalable channel audio representation. This option must be separated from the rest with a ',', and takes the following key=value parameter_id An identifier parameters blocks in frames may refer to dmixp_mode A pre-defined combination of demixing parameters recon_gain Recon gain information used to reconstruct a scalable channel audio representation. This option must be separated from the rest with a ',', and takes the following key=value options parameter_id An identifier parameters blocks in frames may refer to layer A layer defining a Channel Layout in the Audio Element. This option must be separated from the rest with a ','. Several ',' separated entries can be defined, and at least one must be set. It takes the following ":"-separated key=value options ch_layout The layer's channel layout flags The following flags are available: recon_gain Wether to signal if recon_gain is present as metadata in parameter blocks within frames output_gain output_gain_flags Which channels output_gain applies to. The following flags are available: FL FR BL BR TFL TFR ambisonics_mode The ambisonics mode. This has no effect if audio_element_type is set to channel. The following values are supported: mono Each ambisonics channel is coded as an individual mono stream in the group default_w Default weight value iamf_mix_presentation Groups streams that belong to all IAMF Audio Element the same IAMF Mix Presentation references For this group type, the following options are available submix A sub-mix within the Mix Presentation. This option must be separated from the rest with a ','. Several ',' separated entries can be defined, and at least one must be set. It takes the following ":"-separated key=value options parameter_id An identifier parameters blocks in frames may refer to, for post-processing the mixed audio signal to generate the audio signal for playback parameter_rate The sample rate duration fields in parameters blocks in frames that refer to this parameter_id are expressed as default_mix_gain Default mix gain value to apply when there are no parameter blocks sharing the same parameter_id for a given frame element References an Audio Element used in this Mix Presentation to generate the final output audio signal for playback. This option must be separated from the rest with a '|'. Several '|' separated entries can be defined, and at least one must be set. It takes the following ":"-separated key=value options: stg The stream_group_id for an Audio Element which this sub-mix refers to parameter_id An identifier parameters blocks in frames may refer to, for applying any processing to the referenced and rendered Audio Element before being summed with other processed Audio Elements parameter_rate The sample rate duration fields in parameters blocks in frames that refer to this parameter_id are expressed as default_mix_gain Default mix gain value to apply when there are no parameter blocks sharing the same parameter_id for a given frame annotations A key=value string describing the sub-mix element where "key" is a string conforming to BCP-47 that specifies the language for the "value" string. "key" must be the same as the one in the mix's annotations headphones_rendering_mode Indicates whether the input channel-based Audio Element is rendered to stereo loudspeakers or spatialized with a binaural renderer when played back on headphones. This has no effect if the referenced Audio Element's audio_element_type is set to channel. The following values are supported: stereo binaural layout Specifies the layouts for this sub-mix on which the loudness information was measured. This option must be separated from the rest with a '|'. Several '|' separated entries can be defined, and at least one must be set. It takes the following ":"-separated key=value options: layout_type loudspeakers The layout follows the loudspeaker sound system convention of ITU-2051-3. binaural The layout is binaural. sound_system Channel layout matching one of Sound Systems A to J of ITU-2051-3, plus 7.1.2 and 3.1.2 This has no effect if layout_type is set to binaural. integrated_loudness The program integrated loudness information, as defined in ITU-1770-4. digital_peak The digital (sampled) peak value of the audio signal, as defined in ITU-1770-4. true_peak The true peak of the audio signal, as defined in ITU-1770-4. dialog_anchored_loudness The Dialogue loudness information, as defined in ITU-1770-4. album_anchored_loudness The Album loudness information, as defined in ITU-1770-4. annotations A key=value string string describing the mix where "key" is a string conforming to BCP-47 that specifies the language for the "value" string. "key" must be the same as the ones in all sub-mix element's annotationss -target type (output) Specify target file type ("vcd", "svcd", "dvd", "dv", "dv50"). type may be prefixed with "pal-", "ntsc-" or "film-" to use the corresponding standard. All the format options (bitrate, codecs, buffer sizes) are then set automatically. You can just type: ffmpeg -i myfile.avi -target vcd /tmp/vcd.mpg Nevertheless you can specify additional options as long as you know they do not conflict with the standard, as in: ffmpeg -i myfile.avi -target vcd -bf 2 /tmp/vcd.mpg The parameters set for each target are as follows. VCD <pal>: -f vcd -muxrate 1411200 -muxpreload 0.44 -packetsize 2324 -s 352x288 -r 25 -codec:v mpeg1video -g 15 -b:v 1150k -maxrate:v 1150k -minrate:v 1150k -bufsize:v 327680 -ar 44100 -ac 2 -codec:a mp2 -b:a 224k <ntsc>: -f vcd -muxrate 1411200 -muxpreload 0.44 -packetsize 2324 -s 352x240 -r 30000/1001 -codec:v mpeg1video -g 18 -b:v 1150k -maxrate:v 1150k -minrate:v 1150k -bufsize:v 327680 -ar 44100 -ac 2 -codec:a mp2 -b:a 224k <film>: -f vcd -muxrate 1411200 -muxpreload 0.44 -packetsize 2324 -s 352x240 -r 24000/1001 -codec:v mpeg1video -g 18 -b:v 1150k -maxrate:v 1150k -minrate:v 1150k -bufsize:v 327680 -ar 44100 -ac 2 -codec:a mp2 -b:a 224k SVCD <pal>: -f svcd -packetsize 2324 -s 480x576 -pix_fmt yuv420p -r 25 -codec:v mpeg2video -g 15 -b:v 2040k -maxrate:v 2516k -minrate:v 0 -bufsize:v 1835008 -scan_offset 1 -ar 44100 -codec:a mp2 -b:a 224k <ntsc>: -f svcd -packetsize 2324 -s 480x480 -pix_fmt yuv420p -r 30000/1001 -codec:v mpeg2video -g 18 -b:v 2040k -maxrate:v 2516k -minrate:v 0 -bufsize:v 1835008 -scan_offset 1 -ar 44100 -codec:a mp2 -b:a 224k <film>: -f svcd -packetsize 2324 -s 480x480 -pix_fmt yuv420p -r 24000/1001 -codec:v mpeg2video -g 18 -b:v 2040k -maxrate:v 2516k -minrate:v 0 -bufsize:v 1835008 -scan_offset 1 -ar 44100 -codec:a mp2 -b:a 224k DVD <pal>: -f dvd -muxrate 10080k -packetsize 2048 -s 720x576 -pix_fmt yuv420p -r 25 -codec:v mpeg2video -g 15 -b:v 6000k -maxrate:v 9000k -minrate:v 0 -bufsize:v 1835008 -ar 48000 -codec:a ac3 -b:a 448k <ntsc>: -f dvd -muxrate 10080k -packetsize 2048 -s 720x480 -pix_fmt yuv420p -r 30000/1001 -codec:v mpeg2video -g 18 -b:v 6000k -maxrate:v 9000k -minrate:v 0 -bufsize:v 1835008 -ar 48000 -codec:a ac3 -b:a 448k <film>: -f dvd -muxrate 10080k -packetsize 2048 -s 720x480 -pix_fmt yuv420p -r 24000/1001 -codec:v mpeg2video -g 18 -b:v 6000k -maxrate:v 9000k -minrate:v 0 -bufsize:v 1835008 -ar 48000 -codec:a ac3 -b:a 448k DV <pal>: -f dv -s 720x576 -pix_fmt yuv420p -r 25 -ar 48000 -ac 2 <ntsc>: -f dv -s 720x480 -pix_fmt yuv411p -r 30000/1001 -ar 48000 -ac 2 <film>: -f dv -s 720x480 -pix_fmt yuv411p -r 24000/1001 -ar 48000 -ac 2 The "dv50" target is identical to the "dv" target except that the pixel format set is "yuv422p" for all three standards. Any user-set value for a parameter above will override the target preset value. In that case, the output may not comply with the target standard. -dn (input/output) As an input option, blocks all data streams of a file from being filtered or being automatically selected or mapped for any output. See "-discard" option to disable streams individually. As an output option, disables data recording i.e. automatic selection or mapping of any data stream. For full manual control see the "-map" option. -dframes number (output) Set the number of data frames to output. This is an obsolete alias for "-frames:d", which you should use instead. -frames[:stream_specifier] framecount (output,per-stream) Stop writing to the stream after framecount frames. -q[:stream_specifier] q (output,per-stream) -qscale[:stream_specifier] q (output,per-stream) Use fixed quality scale (VBR). The meaning of q/qscale is codec- dependent. If qscale is used without a stream_specifier then it applies only to the video stream, this is to maintain compatibility with previous behavior and as specifying the same codec specific value to 2 different codecs that is audio and video generally is not what is intended when no stream_specifier is used. -filter[:stream_specifier] filtergraph (output,per-stream) Create the filtergraph specified by filtergraph and use it to filter the stream. filtergraph is a description of the filtergraph to apply to the stream, and must have a single input and a single output of the same type of the stream. In the filtergraph, the input is associated to the label "in", and the output to the label "out". See the ffmpeg-filters manual for more information about the filtergraph syntax. See the -filter_complex option if you want to create filtergraphs with multiple inputs and/or outputs. -reinit_filter[:stream_specifier] integer (input,per-stream) This boolean option determines if the filtergraph(s) to which this stream is fed gets reinitialized when input frame parameters change mid-stream. This option is enabled by default as most video and all audio filters cannot handle deviation in input frame properties. Upon reinitialization, existing filter state is lost, like e.g. the frame count "n" reference available in some filters. Any frames buffered at time of reinitialization are lost. The properties where a change triggers reinitialization are, for video, frame resolution or pixel format; for audio, sample format, sample rate, channel count or channel layout. -filter_threads nb_threads (global) Defines how many threads are used to process a filter pipeline. Each pipeline will produce a thread pool with this many threads available for parallel processing. The default is the number of available CPUs. -pre[:stream_specifier] preset_name (output,per-stream) Specify the preset for matching stream(s). -stats (global) Print encoding progress/statistics. It is on by default, to explicitly disable it you need to specify "-nostats". -stats_period time (global) Set period at which encoding progress/statistics are updated. Default is 0.5 seconds. -progress url (global) Send program-friendly progress information to url. Progress information is written periodically and at the end of the encoding process. It is made of "key=value" lines. key consists of only alphanumeric characters. The last key of a sequence of progress information is always "progress". The update period is set using "-stats_period". -stdin Enable interaction on standard input. On by default unless standard input is used as an input. To explicitly disable interaction you need to specify "-nostdin". Disabling interaction on standard input is useful, for example, if ffmpeg is in the background process group. Roughly the same result can be achieved with "ffmpeg ... < /dev/null" but it requires a shell. -debug_ts (global) Print timestamp/latency information. It is off by default. This option is mostly useful for testing and debugging purposes, and the output format may change from one version to another, so it should not be employed by portable scripts. See also the option "-fdebug ts". -attach filename (output) Add an attachment to the output file. This is supported by a few formats like Matroska for e.g. fonts used in rendering subtitles. Attachments are implemented as a specific type of stream, so this option will add a new stream to the file. It is then possible to use per-stream options on this stream in the usual way. Attachment streams created with this option will be created after all the other streams (i.e. those created with "-map" or automatic mappings). Note that for Matroska you also have to set the mimetype metadata tag: ffmpeg -i INPUT -attach DejaVuSans.ttf -metadata:s:2 mimetype=application/x-truetype-font out.mkv (assuming that the attachment stream will be third in the output file). -dump_attachment[:stream_specifier] filename (input,per-stream) Extract the matching attachment stream into a file named filename. If filename is empty, then the value of the "filename" metadata tag will be used. E.g. to extract the first attachment to a file named 'out.ttf': ffmpeg -dump_attachment:t:0 out.ttf -i INPUT To extract all attachments to files determined by the "filename" tag: ffmpeg -dump_attachment:t "" -i INPUT Technical note -- attachments are implemented as codec extradata, so this option can actually be used to extract extradata from any stream, not just attachments. Video Options -vframes number (output) Set the number of video frames to output. This is an obsolete alias for "-frames:v", which you should use instead. -r[:stream_specifier] fps (input/output,per-stream) Set frame rate (Hz value, fraction or abbreviation). As an input option, ignore any timestamps stored in the file and instead generate timestamps assuming constant frame rate fps. This is not the same as the -framerate option used for some input formats like image2 or v4l2 (it used to be the same in older versions of FFmpeg). If in doubt use -framerate instead of the input option -r. As an output option: video encoding Duplicate or drop frames right before encoding them to achieve constant output frame rate fps. video streamcopy Indicate to the muxer that fps is the stream frame rate. No data is dropped or duplicated in this case. This may produce invalid files if fps does not match the actual stream frame rate as determined by packet timestamps. See also the "setts" bitstream filter. -fpsmax[:stream_specifier] fps (output,per-stream) Set maximum frame rate (Hz value, fraction or abbreviation). Clamps output frame rate when output framerate is auto-set and is higher than this value. Useful in batch processing or when input framerate is wrongly detected as very high. It cannot be set together with "-r". It is ignored during streamcopy. -s[:stream_specifier] size (input/output,per-stream) Set frame size. As an input option, this is a shortcut for the video_size private option, recognized by some demuxers for which the frame size is either not stored in the file or is configurable -- e.g. raw video or video grabbers. As an output option, this inserts the "scale" video filter to the end of the corresponding filtergraph. Please use the "scale" filter directly to insert it at the beginning or some other place. The format is wxh (default - same as source). -aspect[:stream_specifier] aspect (output,per-stream) Set the video display aspect ratio specified by aspect. aspect can be a floating point number string, or a string of the form num:den, where num and den are the numerator and denominator of the aspect ratio. For example "4:3", "16:9", "1.3333", and "1.7777" are valid argument values. If used together with -vcodec copy, it will affect the aspect ratio stored at container level, but not the aspect ratio stored in encoded frames, if it exists. -display_rotation[:stream_specifier] rotation (input,per-stream) Set video rotation metadata. rotation is a decimal number specifying the amount in degree by which the video should be rotated counter-clockwise before being displayed. This option overrides the rotation/display transform metadata stored in the file, if any. When the video is being transcoded (rather than copied) and "-autorotate" is enabled, the video will be rotated at the filtering stage. Otherwise, the metadata will be written into the output file if the muxer supports it. If the "-display_hflip" and/or "-display_vflip" options are given, they are applied after the rotation specified by this option. -display_hflip[:stream_specifier] (input,per-stream) Set whether on display the image should be horizontally flipped. See the "-display_rotation" option for more details. -display_vflip[:stream_specifier] (input,per-stream) Set whether on display the image should be vertically flipped. See the "-display_rotation" option for more details. -vn (input/output) As an input option, blocks all video streams of a file from being filtered or being automatically selected or mapped for any output. See "-discard" option to disable streams individually. As an output option, disables video recording i.e. automatic selection or mapping of any video stream. For full manual control see the "-map" option. -vcodec codec (output) Set the video codec. This is an alias for "-codec:v". -pass[:stream_specifier] n (output,per-stream) Select the pass number (1 or 2). It is used to do two-pass video encoding. The statistics of the video are recorded in the first pass into a log file (see also the option -passlogfile), and in the second pass that log file is used to generate the video at the exact requested bitrate. On pass 1, you may just deactivate audio and set output to null, examples for Windows and Unix: ffmpeg -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y NUL ffmpeg -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y /dev/null -passlogfile[:stream_specifier] prefix (output,per-stream) Set two-pass log file name prefix to prefix, the default file name prefix is ``ffmpeg2pass''. The complete file name will be PREFIX-N.log, where N is a number specific to the output stream -vf filtergraph (output) Create the filtergraph specified by filtergraph and use it to filter the stream. This is an alias for "-filter:v", see the -filter option. -autorotate Automatically rotate the video according to file metadata. Enabled by default, use -noautorotate to disable it. -autoscale Automatically scale the video according to the resolution of first frame. Enabled by default, use -noautoscale to disable it. When autoscale is disabled, all output frames of filter graph might not be in the same resolution and may be inadequate for some encoder/muxer. Therefore, it is not recommended to disable it unless you really know what you are doing. Disable autoscale at your own risk. Advanced Video options -pix_fmt[:stream_specifier] format (input/output,per-stream) Set pixel format. Use "-pix_fmts" to show all the supported pixel formats. If the selected pixel format can not be selected, ffmpeg will print a warning and select the best pixel format supported by the encoder. If pix_fmt is prefixed by a "+", ffmpeg will exit with an error if the requested pixel format can not be selected, and automatic conversions inside filtergraphs are disabled. If pix_fmt is a single "+", ffmpeg selects the same pixel format as the input (or graph output) and automatic conversions are disabled. -sws_flags flags (input/output) Set default flags for the libswscale library. These flags are used by automatically inserted "scale" filters and those within simple filtergraphs, if not overridden within the filtergraph definition. See the ffmpeg-scaler manual for a list of scaler options. -rc_override[:stream_specifier] override (output,per-stream) Rate control override for specific intervals, formatted as "int,int,int" list separated with slashes. Two first values are the beginning and end frame numbers, last one is quantizer to use if positive, or quality factor if negative. -vstats Dump video coding statistics to vstats_HHMMSS.log. See the vstats file format section for the format description. -vstats_file file Dump video coding statistics to file. See the vstats file format section for the format description. -vstats_version file Specify which version of the vstats format to use. Default is 2. See the vstats file format section for the format description. -vtag fourcc/tag (output) Force video tag/fourcc. This is an alias for "-tag:v". -force_key_frames[:stream_specifier] time[,time...] (output,per-stream) -force_key_frames[:stream_specifier] expr:expr (output,per-stream) -force_key_frames[:stream_specifier] source (output,per-stream) force_key_frames can take arguments of the following form: time[,time...] If the argument consists of timestamps, ffmpeg will round the specified times to the nearest output timestamp as per the encoder time base and force a keyframe at the first frame having timestamp equal or greater than the computed timestamp. Note that if the encoder time base is too coarse, then the keyframes may be forced on frames with timestamps lower than the specified time. The default encoder time base is the inverse of the output framerate but may be set otherwise via "-enc_time_base". If one of the times is ""chapters"[delta]", it is expanded into the time of the beginning of all chapters in the file, shifted by delta, expressed as a time in seconds. This option can be useful to ensure that a seek point is present at a chapter mark or any other designated place in the output file. For example, to insert a key frame at 5 minutes, plus key frames 0.1 second before the beginning of every chapter: -force_key_frames 0:05:00,chapters-0.1 expr:expr If the argument is prefixed with "expr:", the string expr is interpreted like an expression and is evaluated for each frame. A key frame is forced in case the evaluation is non-zero. The expression in expr can contain the following constants: n the number of current processed frame, starting from 0 n_forced the number of forced frames prev_forced_n the number of the previous forced frame, it is "NAN" when no keyframe was forced yet prev_forced_t the time of the previous forced frame, it is "NAN" when no keyframe was forced yet t the time of the current processed frame For example to force a key frame every 5 seconds, you can specify: -force_key_frames expr:gte(t,n_forced*5) To force a key frame 5 seconds after the time of the last forced one, starting from second 13: -force_key_frames expr:if(isnan(prev_forced_t),gte(t,13),gte(t,prev_forced_t+5)) source If the argument is "source", ffmpeg will force a key frame if the current frame being encoded is marked as a key frame in its source. In cases where this particular source frame has to be dropped, enforce the next available frame to become a key frame instead. Note that forcing too many keyframes is very harmful for the lookahead algorithms of certain encoders: using fixed-GOP options or similar would be more efficient. -copyinkf[:stream_specifier] (output,per-stream) When doing stream copy, copy also non-key frames found at the beginning. -init_hw_device type[=name][:device[,key=value...]] Initialise a new hardware device of type type called name, using the given device parameters. If no name is specified it will receive a default name of the form "type%d". The meaning of device and the following arguments depends on the device type: cuda device is the number of the CUDA device. The following options are recognized: primary_ctx If set to 1, uses the primary device context instead of creating a new one. Examples: -init_hw_device cuda:1 Choose the second device on the system. -init_hw_device cuda:0,primary_ctx=1 Choose the first device and use the primary device context. dxva2 device is the number of the Direct3D 9 display adapter. d3d11va device is the number of the Direct3D 11 display adapter. If not specified, it will attempt to use the default Direct3D 11 display adapter or the first Direct3D 11 display adapter whose hardware VendorId is specified by vendor_id. Examples: -init_hw_device d3d11va Create a d3d11va device on the default Direct3D 11 display adapter. -init_hw_device d3d11va:1 Create a d3d11va device on the Direct3D 11 display adapter specified by index 1. -init_hw_device d3d11va:,vendor_id=0x8086 Create a d3d11va device on the first Direct3D 11 display adapter whose hardware VendorId is 0x8086. vaapi device is either an X11 display name, a DRM render node or a DirectX adapter index. If not specified, it will attempt to open the default X11 display ($DISPLAY) and then the first DRM render node (/dev/dri/renderD128), or the default DirectX adapter on Windows. The following options are recognized: kernel_driver When device is not specified, use this option to specify the name of the kernel driver associated with the desired device. This option is available only when the hardware acceleration method drm and vaapi are enabled. Examples: -init_hw_device vaapi Create a vaapi device on the default device. -init_hw_device vaapi:/dev/dri/renderD129 Create a vaapi device on DRM render node /dev/dri/renderD129. -init_hw_device vaapi:1 Create a vaapi device on DirectX adapter 1. -init_hw_device vaapi:,kernel_driver=i915 Create a vaapi device on a device associated with kernel driver i915. vdpau device is an X11 display name. If not specified, it will attempt to open the default X11 display ($DISPLAY). qsv device selects a value in MFX_IMPL_*. Allowed values are: auto sw hw auto_any hw_any hw2 hw3 hw4 If not specified, auto_any is used. (Note that it may be easier to achieve the desired result for QSV by creating the platform-appropriate subdevice (dxva2 or d3d11va or vaapi) and then deriving a QSV device from that.) The following options are recognized: child_device Specify a DRM render node on Linux or DirectX adapter on Windows. child_device_type Choose platform-appropriate subdevice type. On Windows d3d11va is used as default subdevice type when "--enable-libvpl" is specified at configuration time, dxva2 is used as default subdevice type when "--enable-libmfx" is specified at configuration time. On Linux user can use vaapi only as subdevice type. Examples: -init_hw_device qsv:hw,child_device=/dev/dri/renderD129 Create a QSV device with MFX_IMPL_HARDWARE on DRM render node /dev/dri/renderD129. -init_hw_device qsv:hw,child_device=1 Create a QSV device with MFX_IMPL_HARDWARE on DirectX adapter 1. -init_hw_device qsv:hw,child_device_type=d3d11va Choose the GPU subdevice with type d3d11va and create QSV device with MFX_IMPL_HARDWARE. -init_hw_device qsv:hw,child_device_type=dxva2 Choose the GPU subdevice with type dxva2 and create QSV device with MFX_IMPL_HARDWARE. -init_hw_device qsv:hw,child_device=1,child_device_type=d3d11va Create a QSV device with MFX_IMPL_HARDWARE on DirectX adapter 1 with subdevice type d3d11va. -init_hw_device vaapi=va:/dev/dri/renderD129 -init_hw_device qsv=hw1@va Create a VAAPI device called va on /dev/dri/renderD129, then derive a QSV device called hw1 from device va. opencl device selects the platform and device as platform_index.device_index. The set of devices can also be filtered using the key-value pairs to find only devices matching particular platform or device strings. The strings usable as filters are: platform_profile platform_version platform_name platform_vendor platform_extensions device_name device_vendor driver_version device_version device_profile device_extensions device_type The indices and filters must together uniquely select a device. Examples: -init_hw_device opencl:0.1 Choose the second device on the first platform. -init_hw_device opencl:,device_name=Foo9000 Choose the device with a name containing the string Foo9000. -init_hw_device opencl:1,device_type=gpu,device_extensions=cl_khr_fp16 Choose the GPU device on the second platform supporting the cl_khr_fp16 extension. vulkan If device is an integer, it selects the device by its index in a system-dependent list of devices. If device is any other string, it selects the first device with a name containing that string as a substring. The following options are recognized: debug If set to 1, enables the validation layer, if installed. linear_images If set to 1, images allocated by the hwcontext will be linear and locally mappable. instance_extensions A plus separated list of additional instance extensions to enable. device_extensions A plus separated list of additional device extensions to enable. Examples: -init_hw_device vulkan:1 Choose the second device on the system. -init_hw_device vulkan:RADV Choose the first device with a name containing the string RADV. -init_hw_device vulkan:0,instance_extensions=VK_KHR_wayland_surface+VK_KHR_xcb_surface Choose the first device and enable the Wayland and XCB instance extensions. -init_hw_device type[=name]@source Initialise a new hardware device of type type called name, deriving it from the existing device with the name source. -init_hw_device list List all hardware device types supported in this build of ffmpeg. -filter_hw_device name Pass the hardware device called name to all filters in any filter graph. This can be used to set the device to upload to with the "hwupload" filter, or the device to map to with the "hwmap" filter. Other filters may also make use of this parameter when they require a hardware device. Note that this is typically only required when the input is not already in hardware frames - when it is, filters will derive the device they require from the context of the frames they receive as input. This is a global setting, so all filters will receive the same device. -hwaccel[:stream_specifier] hwaccel (input,per-stream) Use hardware acceleration to decode the matching stream(s). The allowed values of hwaccel are: none Do not use any hardware acceleration (the default). auto Automatically select the hardware acceleration method. vdpau Use VDPAU (Video Decode and Presentation API for Unix) hardware acceleration. dxva2 Use DXVA2 (DirectX Video Acceleration) hardware acceleration. d3d11va Use D3D11VA (DirectX Video Acceleration) hardware acceleration. vaapi Use VAAPI (Video Acceleration API) hardware acceleration. qsv Use the Intel QuickSync Video acceleration for video transcoding. Unlike most other values, this option does not enable accelerated decoding (that is used automatically whenever a qsv decoder is selected), but accelerated transcoding, without copying the frames into the system memory. For it to work, both the decoder and the encoder must support QSV acceleration and no filters must be used. This option has no effect if the selected hwaccel is not available or not supported by the chosen decoder. Note that most acceleration methods are intended for playback and will not be faster than software decoding on modern CPUs. Additionally, ffmpeg will usually need to copy the decoded frames from the GPU memory into the system memory, resulting in further performance loss. This option is thus mainly useful for testing. -hwaccel_device[:stream_specifier] hwaccel_device (input,per-stream) Select a device to use for hardware acceleration. This option only makes sense when the -hwaccel option is also specified. It can either refer to an existing device created with -init_hw_device by name, or it can create a new device as if -init_hw_device type:hwaccel_device were called immediately before. -hwaccels List all hardware acceleration components enabled in this build of ffmpeg. Actual runtime availability depends on the hardware and its suitable driver being installed. -fix_sub_duration_heartbeat[:stream_specifier] Set a specific output video stream as the heartbeat stream according to which to split and push through currently in-progress subtitle upon receipt of a random access packet. This lowers the latency of subtitles for which the end packet or the following subtitle has not yet been received. As a drawback, this will most likely lead to duplication of subtitle events in order to cover the full duration, so when dealing with use cases where latency of when the subtitle event is passed on to output is not relevant this option should not be utilized. Requires -fix_sub_duration to be set for the relevant input subtitle stream for this to have any effect, as well as for the input subtitle stream having to be directly mapped to the same output in which the heartbeat stream resides. Audio Options -aframes number (output) Set the number of audio frames to output. This is an obsolete alias for "-frames:a", which you should use instead. -ar[:stream_specifier] freq (input/output,per-stream) Set the audio sampling frequency. For output streams it is set by default to the frequency of the corresponding input stream. For input streams this option only makes sense for audio grabbing devices and raw demuxers and is mapped to the corresponding demuxer options. -aq q (output) Set the audio quality (codec-specific, VBR). This is an alias for -q:a. -ac[:stream_specifier] channels (input/output,per-stream) Set the number of audio channels. For output streams it is set by default to the number of input audio channels. For input streams this option only makes sense for audio grabbing devices and raw demuxers and is mapped to the corresponding demuxer options. -an (input/output) As an input option, blocks all audio streams of a file from being filtered or being automatically selected or mapped for any output. See "-discard" option to disable streams individually. As an output option, disables audio recording i.e. automatic selection or mapping of any audio stream. For full manual control see the "-map" option. -acodec codec (input/output) Set the audio codec. This is an alias for "-codec:a". -sample_fmt[:stream_specifier] sample_fmt (output,per-stream) Set the audio sample format. Use "-sample_fmts" to get a list of supported sample formats. -af filtergraph (output) Create the filtergraph specified by filtergraph and use it to filter the stream. This is an alias for "-filter:a", see the -filter option. Advanced Audio options -atag fourcc/tag (output) Force audio tag/fourcc. This is an alias for "-tag:a". -guess_layout_max channels (input,per-stream) If some input channel layout is not known, try to guess only if it corresponds to at most the specified number of channels. For example, 2 tells to ffmpeg to recognize 1 channel as mono and 2 channels as stereo but not 6 channels as 5.1. The default is to always try to guess. Use 0 to disable all guessing. Subtitle options -scodec codec (input/output) Set the subtitle codec. This is an alias for "-codec:s". -sn (input/output) As an input option, blocks all subtitle streams of a file from being filtered or being automatically selected or mapped for any output. See "-discard" option to disable streams individually. As an output option, disables subtitle recording i.e. automatic selection or mapping of any subtitle stream. For full manual control see the "-map" option. Advanced Subtitle options -fix_sub_duration Fix subtitles durations. For each subtitle, wait for the next packet in the same stream and adjust the duration of the first to avoid overlap. This is necessary with some subtitles codecs, especially DVB subtitles, because the duration in the original packet is only a rough estimate and the end is actually marked by an empty subtitle frame. Failing to use this option when necessary can result in exaggerated durations or muxing failures due to non- monotonic timestamps. Note that this option will delay the output of all data until the next subtitle packet is decoded: it may increase memory consumption and latency a lot. -canvas_size size Set the size of the canvas used to render subtitles. Advanced options -map [-]input_file_id[:stream_specifier][?] | [linklabel] (output) Create one or more streams in the output file. This option has two forms for specifying the data source(s): the first selects one or more streams from some input file (specified with "-i"), the second takes an output from some complex filtergraph (specified with "-filter_complex"). In the first form, an output stream is created for every stream from the input file with the index input_file_id. If stream_specifier is given, only those streams that match the specifier are used (see the Stream specifiers section for the stream_specifier syntax). A "-" character before the stream identifier creates a "negative" mapping. It disables matching streams from already created mappings. A trailing "?" after the stream index will allow the map to be optional: if the map matches no streams the map will be ignored instead of failing. Note the map will still fail if an invalid input file index is used; such as if the map refers to a non- existent input. An alternative [linklabel] form will map outputs from complex filter graphs (see the -filter_complex option) to the output file. linklabel must correspond to a defined output link label in the graph. This option may be specified multiple times, each adding more streams to the output file. Any given input stream may also be mapped any number of times as a source for different output streams, e.g. in order to use different encoding options and/or filters. The streams are created in the output in the same order in which the "-map" options are given on the commandline. Using this option disables the default mappings for this output file. Examples: map everything To map ALL streams from the first input file to output ffmpeg -i INPUT -map 0 output select specific stream If you have two audio streams in the first input file, these streams are identified by 0:0 and 0:1. You can use "-map" to select which streams to place in an output file. For example: ffmpeg -i INPUT -map 0:1 out.wav will map the second input stream in INPUT to the (single) output stream in out.wav. create multiple streams To select the stream with index 2 from input file a.mov (specified by the identifier 0:2), and stream with index 6 from input b.mov (specified by the identifier 1:6), and copy them to the output file out.mov: ffmpeg -i a.mov -i b.mov -c copy -map 0:2 -map 1:6 out.mov create multiple streams 2 To select all video and the third audio stream from an input file: ffmpeg -i INPUT -map 0:v -map 0:a:2 OUTPUT negative map To map all the streams except the second audio, use negative mappings ffmpeg -i INPUT -map 0 -map -0:a:1 OUTPUT optional map To map the video and audio streams from the first input, and using the trailing "?", ignore the audio mapping if no audio streams exist in the first input: ffmpeg -i INPUT -map 0:v -map 0:a? OUTPUT map by language To pick the English audio stream: ffmpeg -i INPUT -map 0:m:language:eng OUTPUT -ignore_unknown Ignore input streams with unknown type instead of failing if copying such streams is attempted. -copy_unknown Allow input streams with unknown type to be copied instead of failing if copying such streams is attempted. -map_metadata[:metadata_spec_out] infile[:metadata_spec_in] (output,per-metadata) Set metadata information of the next output file from infile. Note that those are file indices (zero-based), not filenames. Optional metadata_spec_in/out parameters specify, which metadata to copy. A metadata specifier can have the following forms: g global metadata, i.e. metadata that applies to the whole file s[:stream_spec] per-stream metadata. stream_spec is a stream specifier as described in the Stream specifiers chapter. In an input metadata specifier, the first matching stream is copied from. In an output metadata specifier, all matching streams are copied to. c:chapter_index per-chapter metadata. chapter_index is the zero-based chapter index. p:program_index per-program metadata. program_index is the zero-based program index. If metadata specifier is omitted, it defaults to global. By default, global metadata is copied from the first input file, per-stream and per-chapter metadata is copied along with streams/chapters. These default mappings are disabled by creating any mapping of the relevant type. A negative file index can be used to create a dummy mapping that just disables automatic copying. For example to copy metadata from the first stream of the input file to global metadata of the output file: ffmpeg -i in.ogg -map_metadata 0:s:0 out.mp3 To do the reverse, i.e. copy global metadata to all audio streams: ffmpeg -i in.mkv -map_metadata:s:a 0:g out.mkv Note that simple 0 would work as well in this example, since global metadata is assumed by default. -map_chapters input_file_index (output) Copy chapters from input file with index input_file_index to the next output file. If no chapter mapping is specified, then chapters are copied from the first input file with at least one chapter. Use a negative file index to disable any chapter copying. -benchmark (global) Show benchmarking information at the end of an encode. Shows real, system and user time used and maximum memory consumption. Maximum memory consumption is not supported on all systems, it will usually display as 0 if not supported. -benchmark_all (global) Show benchmarking information during the encode. Shows real, system and user time used in various steps (audio/video encode/decode). -timelimit duration (global) Exit after ffmpeg has been running for duration seconds in CPU user time. -dump (global) Dump each input packet to stderr. -hex (global) When dumping packets, also dump the payload. -readrate speed (input) Limit input read speed. Its value is a floating-point positive number which represents the maximum duration of media, in seconds, that should be ingested in one second of wallclock time. Default value is zero and represents no imposed limitation on speed of ingestion. Value 1 represents real-time speed and is equivalent to "-re". Mainly used to simulate a capture device or live input stream (e.g. when reading from a file). Should not be used with a low value when input is an actual capture device or live stream as it may cause packet loss. It is useful for when flow speed of output packets is important, such as live streaming. -re (input) Read input at native frame rate. This is equivalent to setting "-readrate 1". -readrate_initial_burst seconds Set an initial read burst time, in seconds, after which -re/-readrate will be enforced. -vsync parameter (global) -fps_mode[:stream_specifier] parameter (output,per-stream) Set video sync method / framerate mode. vsync is applied to all output video streams but can be overridden for a stream by setting fps_mode. vsync is deprecated and will be removed in the future. For compatibility reasons some of the values for vsync can be specified as numbers (shown in parentheses in the following table). passthrough (0) Each frame is passed with its timestamp from the demuxer to the muxer. cfr (1) Frames will be duplicated and dropped to achieve exactly the requested constant frame rate. vfr (2) Frames are passed through with their timestamp or dropped so as to prevent 2 frames from having the same timestamp. auto (-1) Chooses between cfr and vfr depending on muxer capabilities. This is the default method. Note that the timestamps may be further modified by the muxer, after this. For example, in the case that the format option avoid_negative_ts is enabled. With -map you can select from which stream the timestamps should be taken. You can leave either video or audio unchanged and sync the remaining stream(s) to the unchanged one. -frame_drop_threshold parameter Frame drop threshold, which specifies how much behind video frames can be before they are dropped. In frame rate units, so 1.0 is one frame. The default is -1.1. One possible usecase is to avoid framedrops in case of noisy timestamps or to increase frame drop precision in case of exact timestamps. -apad parameters (output,per-stream) Pad the output audio stream(s). This is the same as applying "-af apad". Argument is a string of filter parameters composed the same as with the "apad" filter. "-shortest" must be set for this output for the option to take effect. -copyts Do not process input timestamps, but keep their values without trying to sanitize them. In particular, do not remove the initial start time offset value. Note that, depending on the vsync option or on specific muxer processing (e.g. in case the format option avoid_negative_ts is enabled) the output timestamps may mismatch with the input timestamps even when this option is selected. -start_at_zero When used with copyts, shift input timestamps so they start at zero. This means that using e.g. "-ss 50" will make output timestamps start at 50 seconds, regardless of what timestamp the input file started at. -copytb mode Specify how to set the encoder timebase when stream copying. mode is an integer numeric value, and can assume one of the following values: 1 Use the demuxer timebase. The time base is copied to the output encoder from the corresponding input demuxer. This is sometimes required to avoid non monotonically increasing timestamps when copying video streams with variable frame rate. 0 Use the decoder timebase. The time base is copied to the output encoder from the corresponding input decoder. -1 Try to make the choice automatically, in order to generate a sane output. Default value is -1. -enc_time_base[:stream_specifier] timebase (output,per-stream) Set the encoder timebase. timebase can assume one of the following values: 0 Assign a default value according to the media type. For video - use 1/framerate, for audio - use 1/samplerate. demux Use the timebase from the demuxer. filter Use the timebase from the filtergraph. a positive number Use the provided number as the timebase. This field can be provided as a ratio of two integers (e.g. 1:24, 1:48000) or as a decimal number (e.g. 0.04166, 2.0833e-5) Default value is 0. -bitexact (input/output) Enable bitexact mode for (de)muxer and (de/en)coder -shortest (output) Finish encoding when the shortest output stream ends. Note that this option may require buffering frames, which introduces extra latency. The maximum amount of this latency may be controlled with the "-shortest_buf_duration" option. -shortest_buf_duration duration (output) The "-shortest" option may require buffering potentially large amounts of data when at least one of the streams is "sparse" (i.e. has large gaps between frames X this is typically the case for subtitles). This option controls the maximum duration of buffered frames in seconds. Larger values may allow the "-shortest" option to produce more accurate results, but increase memory use and latency. The default value is 10 seconds. -dts_delta_threshold threshold Timestamp discontinuity delta threshold, expressed as a decimal number of seconds. The timestamp discontinuity correction enabled by this option is only applied to input formats accepting timestamp discontinuity (for which the "AVFMT_TS_DISCONT" flag is enabled), e.g. MPEG-TS and HLS, and is automatically disabled when employing the "-copyts" option (unless wrapping is detected). If a timestamp discontinuity is detected whose absolute value is greater than threshold, ffmpeg will remove the discontinuity by decreasing/increasing the current DTS and PTS by the corresponding delta value. The default value is 10. -dts_error_threshold threshold Timestamp error delta threshold, expressed as a decimal number of seconds. The timestamp correction enabled by this option is only applied to input formats not accepting timestamp discontinuity (for which the "AVFMT_TS_DISCONT" flag is not enabled). If a timestamp discontinuity is detected whose absolute value is greater than threshold, ffmpeg will drop the PTS/DTS timestamp value. The default value is "3600*30" (30 hours), which is arbitrarily picked and quite conservative. -muxdelay seconds (output) Set the maximum demux-decode delay. -muxpreload seconds (output) Set the initial demux-decode delay. -streamid output-stream-index:new-value (output) Assign a new stream-id value to an output stream. This option should be specified prior to the output filename to which it applies. For the situation where multiple output files exist, a streamid may be reassigned to a different value. For example, to set the stream 0 PID to 33 and the stream 1 PID to 36 for an output mpegts file: ffmpeg -i inurl -streamid 0:33 -streamid 1:36 out.ts -bsf[:stream_specifier] bitstream_filters (input/output,per-stream) Apply bitstream filters to matching streams. The filters are applied to each packet as it is received from the demuxer (when used as an input option) or before it is sent to the muxer (when used as an output option). bitstream_filters is a comma-separated list of bitstream filter specifications, each of the form <filter>[=<optname0>=<optval0>:<optname1>=<optval1>:...] Any of the ',=:' characters that are to be a part of an option value need to be escaped with a backslash. Use the "-bsfs" option to get the list of bitstream filters. E.g. ffmpeg -bsf:v h264_mp4toannexb -i h264.mp4 -c:v copy -an out.h264 applies the "h264_mp4toannexb" bitstream filter (which converts MP4-encapsulated H.264 stream to Annex B) to the input video stream. On the other hand, ffmpeg -i file.mov -an -vn -bsf:s mov2textsub -c:s copy -f rawvideo sub.txt applies the "mov2textsub" bitstream filter (which extracts text from MOV subtitles) to the output subtitle stream. Note, however, that since both examples use "-c copy", it matters little whether the filters are applied on input or output - that would change if transcoding was happening. -tag[:stream_specifier] codec_tag (input/output,per-stream) Force a tag/fourcc for matching streams. -timecode hh:mm:ssSEPff Specify Timecode for writing. SEP is ':' for non drop timecode and ';' (or '.') for drop. ffmpeg -i input.mpg -timecode 01:02:03.04 -r 30000/1001 -s ntsc output.mpg -filter_complex filtergraph (global) Define a complex filtergraph, i.e. one with arbitrary number of inputs and/or outputs. For simple graphs -- those with one input and one output of the same type -- see the -filter options. filtergraph is a description of the filtergraph, as described in the ``Filtergraph syntax'' section of the ffmpeg-filters manual. Input link labels must refer to either input streams or loopback decoders. For input streams, use the "[file_index:stream_specifier]" syntax (i.e. the same as -map uses). If stream_specifier matches multiple streams, the first one will be used. For decoders, the link label must be [dec:dec_idx], where dec_idx is the index of the loopback decoder to be connected to given input. An unlabeled input will be connected to the first unused input stream of the matching type. Output link labels are referred to with -map. Unlabeled outputs are added to the first output file. Note that with this option it is possible to use only lavfi sources without normal input files. For example, to overlay an image over video ffmpeg -i video.mkv -i image.png -filter_complex '[0:v][1:v]overlay[out]' -map '[out]' out.mkv Here "[0:v]" refers to the first video stream in the first input file, which is linked to the first (main) input of the overlay filter. Similarly the first video stream in the second input is linked to the second (overlay) input of overlay. Assuming there is only one video stream in each input file, we can omit input labels, so the above is equivalent to ffmpeg -i video.mkv -i image.png -filter_complex 'overlay[out]' -map '[out]' out.mkv Furthermore we can omit the output label and the single output from the filter graph will be added to the output file automatically, so we can simply write ffmpeg -i video.mkv -i image.png -filter_complex 'overlay' out.mkv As a special exception, you can use a bitmap subtitle stream as input: it will be converted into a video with the same size as the largest video in the file, or 720x576 if no video is present. Note that this is an experimental and temporary solution. It will be removed once libavfilter has proper support for subtitles. For example, to hardcode subtitles on top of a DVB-T recording stored in MPEG-TS format, delaying the subtitles by 1 second: ffmpeg -i input.ts -filter_complex \ '[#0x2ef] setpts=PTS+1/TB [sub] ; [#0x2d0] [sub] overlay' \ -sn -map '#0x2dc' output.mkv (0x2d0, 0x2dc and 0x2ef are the MPEG-TS PIDs of respectively the video, audio and subtitles streams; 0:0, 0:3 and 0:7 would have worked too) To generate 5 seconds of pure red video using lavfi "color" source: ffmpeg -filter_complex 'color=c=red' -t 5 out.mkv -filter_complex_threads nb_threads (global) Defines how many threads are used to process a filter_complex graph. Similar to filter_threads but used for "-filter_complex" graphs only. The default is the number of available CPUs. -lavfi filtergraph (global) Define a complex filtergraph, i.e. one with arbitrary number of inputs and/or outputs. Equivalent to -filter_complex. -accurate_seek (input) This option enables or disables accurate seeking in input files with the -ss option. It is enabled by default, so seeking is accurate when transcoding. Use -noaccurate_seek to disable it, which may be useful e.g. when copying some streams and transcoding the others. -seek_timestamp (input) This option enables or disables seeking by timestamp in input files with the -ss option. It is disabled by default. If enabled, the argument to the -ss option is considered an actual timestamp, and is not offset by the start time of the file. This matters only for files which do not start from timestamp 0, such as transport streams. -thread_queue_size size (input/output) For input, this option sets the maximum number of queued packets when reading from the file or device. With low latency / high rate live streams, packets may be discarded if they are not read in a timely manner; setting this value can force ffmpeg to use a separate input thread and read packets as soon as they arrive. By default ffmpeg only does this if multiple inputs are specified. For output, this option specified the maximum number of packets that may be queued to each muxing thread. -sdp_file file (global) Print sdp information for an output stream to file. This allows dumping sdp information when at least one output isn't an rtp stream. (Requires at least one of the output formats to be rtp). -discard (input) Allows discarding specific streams or frames from streams. Any input stream can be fully discarded, using value "all" whereas selective discarding of frames from a stream occurs at the demuxer and is not supported by all demuxers. none Discard no frame. default Default, which discards no frames. noref Discard all non-reference frames. bidir Discard all bidirectional frames. nokey Discard all frames excepts keyframes. all Discard all frames. -abort_on flags (global) Stop and abort on various conditions. The following flags are available: empty_output No packets were passed to the muxer, the output is empty. empty_output_stream No packets were passed to the muxer in some of the output streams. -max_error_rate (global) Set fraction of decoding frame failures across all inputs which when crossed ffmpeg will return exit code 69. Crossing this threshold does not terminate processing. Range is a floating-point number between 0 to 1. Default is 2/3. -xerror (global) Stop and exit on error -max_muxing_queue_size packets (output,per-stream) When transcoding audio and/or video streams, ffmpeg will not begin writing into the output until it has one packet for each such stream. While waiting for that to happen, packets for other streams are buffered. This option sets the size of this buffer, in packets, for the matching output stream. The default value of this option should be high enough for most uses, so only touch this option if you are sure that you need it. -muxing_queue_data_threshold bytes (output,per-stream) This is a minimum threshold until which the muxing queue size is not taken into account. Defaults to 50 megabytes per stream, and is based on the overall size of packets passed to the muxer. -auto_conversion_filters (global) Enable automatically inserting format conversion filters in all filter graphs, including those defined by -vf, -af, -filter_complex and -lavfi. If filter format negotiation requires a conversion, the initialization of the filters will fail. Conversions can still be performed by inserting the relevant conversion filter (scale, aresample) in the graph. On by default, to explicitly disable it you need to specify "-noauto_conversion_filters". -bits_per_raw_sample[:stream_specifier] value (output,per-stream) Declare the number of bits per raw sample in the given output stream to be value. Note that this option sets the information provided to the encoder/muxer, it does not change the stream to conform to this value. Setting values that do not match the stream properties may result in encoding failures or invalid output files. -stats_enc_pre[:stream_specifier] path (output,per-stream) -stats_enc_post[:stream_specifier] path (output,per-stream) -stats_mux_pre[:stream_specifier] path (output,per-stream) Write per-frame encoding information about the matching streams into the file given by path. -stats_enc_pre writes information about raw video or audio frames right before they are sent for encoding, while -stats_enc_post writes information about encoded packets as they are received from the encoder. -stats_mux_pre writes information about packets just as they are about to be sent to the muxer. Every frame or packet produces one line in the specified file. The format of this line is controlled by -stats_enc_pre_fmt / -stats_enc_post_fmt / -stats_mux_pre_fmt. When stats for multiple streams are written into a single file, the lines corresponding to different streams will be interleaved. The precise order of this interleaving is not specified and not guaranteed to remain stable between different invocations of the program, even with the same options. -stats_enc_pre_fmt[:stream_specifier] format_spec (output,per-stream) -stats_enc_post_fmt[:stream_specifier] format_spec (output,per-stream) -stats_mux_pre_fmt[:stream_specifier] format_spec (output,per-stream) Specify the format for the lines written with -stats_enc_pre / -stats_enc_post / -stats_mux_pre. format_spec is a string that may contain directives of the form {fmt}. format_spec is backslash-escaped --- use \{, \}, and \\ to write a literal {, }, or \, respectively, into the output. The directives given with fmt may be one of the following: fidx Index of the output file. sidx Index of the output stream in the file. n Frame number. Pre-encoding: number of frames sent to the encoder so far. Post-encoding: number of packets received from the encoder so far. Muxing: number of packets submitted to the muxer for this stream so far. ni Input frame number. Index of the input frame (i.e. output by a decoder) that corresponds to this output frame or packet. -1 if unavailable. tb Timebase in which this frame/packet's timestamps are expressed, as a rational number num/den. Note that encoder and muxer may use different timebases. tbi Timebase for ptsi, as a rational number num/den. Available when ptsi is available, 0/1 otherwise. pts Presentation timestamp of the frame or packet, as an integer. Should be multiplied by the timebase to compute presentation time. ptsi Presentation timestamp of the input frame (see ni), as an integer. Should be multiplied by tbi to compute presentation time. Printed as (2^63 - 1 = 9223372036854775807) when not available. t Presentation time of the frame or packet, as a decimal number. Equal to pts multiplied by tb. ti Presentation time of the input frame (see ni), as a decimal number. Equal to ptsi multiplied by tbi. Printed as inf when not available. dts (packet) Decoding timestamp of the packet, as an integer. Should be multiplied by the timebase to compute presentation time. dt (packet) Decoding time of the frame or packet, as a decimal number. Equal to dts multiplied by tb. sn (frame,audio) Number of audio samples sent to the encoder so far. samp (frame,audio) Number of audio samples in the frame. size (packet) Size of the encoded packet in bytes. br (packet) Current bitrate in bits per second. abr (packet) Average bitrate for the whole stream so far, in bits per second, -1 if it cannot be determined at this point. key (packet) Character 'K' if the packet contains a keyframe, character 'N' otherwise. Directives tagged with packet may only be used with -stats_enc_post_fmt and -stats_mux_pre_fmt. Directives tagged with frame may only be used with -stats_enc_pre_fmt. Directives tagged with audio may only be used with audio streams. The default format strings are: pre-encoding {fidx} {sidx} {n} {t} post-encoding {fidx} {sidx} {n} {t} In the future, new items may be added to the end of the default formatting strings. Users who depend on the format staying exactly the same, should prescribe it manually. Note that stats for different streams written into the same file may have different formats. Preset files A preset file contains a sequence of option=value pairs, one for each line, specifying a sequence of options which would be awkward to specify on the command line. Lines starting with the hash ('#') character are ignored and are used to provide comments. Check the presets directory in the FFmpeg source tree for examples. There are two types of preset files: ffpreset and avpreset files. ffpreset files ffpreset files are specified with the "vpre", "apre", "spre", and "fpre" options. The "fpre" option takes the filename of the preset instead of a preset name as input and can be used for any kind of codec. For the "vpre", "apre", and "spre" options, the options specified in a preset file are applied to the currently selected codec of the same type as the preset option. The argument passed to the "vpre", "apre", and "spre" preset options identifies the preset file to use according to the following rules: First ffmpeg searches for a file named arg.ffpreset in the directories $FFMPEG_DATADIR (if set), and $HOME/.ffmpeg, and in the datadir defined at configuration time (usually PREFIX/share/ffmpeg) or in a ffpresets folder along the executable on win32, in that order. For example, if the argument is "libvpx-1080p", it will search for the file libvpx-1080p.ffpreset. If no such file is found, then ffmpeg will search for a file named codec_name-arg.ffpreset in the above-mentioned directories, where codec_name is the name of the codec to which the preset file options will be applied. For example, if you select the video codec with "-vcodec libvpx" and use "-vpre 1080p", then it will search for the file libvpx-1080p.ffpreset. avpreset files avpreset files are specified with the "pre" option. They work similar to ffpreset files, but they only allow encoder- specific options. Therefore, an option=value pair specifying an encoder cannot be used. When the "pre" option is specified, ffmpeg will look for files with the suffix .avpreset in the directories $AVCONV_DATADIR (if set), and $HOME/.avconv, and in the datadir defined at configuration time (usually PREFIX/share/ffmpeg), in that order. First ffmpeg searches for a file named codec_name-arg.avpreset in the above-mentioned directories, where codec_name is the name of the codec to which the preset file options will be applied. For example, if you select the video codec with "-vcodec libvpx" and use "-pre 1080p", then it will search for the file libvpx-1080p.avpreset. If no such file is found, then ffmpeg will search for a file named arg.avpreset in the same directories. vstats file format The "-vstats" and "-vstats_file" options enable generation of a file containing statistics about the generated video outputs. The "-vstats_version" option controls the format version of the generated file. With version 1 the format is: frame= <FRAME> q= <FRAME_QUALITY> PSNR= <PSNR> f_size= <FRAME_SIZE> s_size= <STREAM_SIZE>kB time= <TIMESTAMP> br= <BITRATE>kbits/s avg_br= <AVERAGE_BITRATE>kbits/s With version 2 the format is: out= <OUT_FILE_INDEX> st= <OUT_FILE_STREAM_INDEX> frame= <FRAME_NUMBER> q= <FRAME_QUALITY>f PSNR= <PSNR> f_size= <FRAME_SIZE> s_size= <STREAM_SIZE>kB time= <TIMESTAMP> br= <BITRATE>kbits/s avg_br= <AVERAGE_BITRATE>kbits/s The value corresponding to each key is described below: avg_br average bitrate expressed in Kbits/s br bitrate expressed in Kbits/s frame number of encoded frame out out file index PSNR Peak Signal to Noise Ratio q quality of the frame f_size encoded packet size expressed as number of bytes s_size stream size expressed in KiB st out file stream index time time of the packet type picture type See also the -stats_enc options for an alternative way to show encoding statistics.
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The following examples illustrate the behavior, quirks and limitations of ffmpeg's stream selection methods. They assume the following three input files. input file 'A.avi' stream 0: video 640x360 stream 1: audio 2 channels input file 'B.mp4' stream 0: video 1920x1080 stream 1: audio 2 channels stream 2: subtitles (text) stream 3: audio 5.1 channels stream 4: subtitles (text) input file 'C.mkv' stream 0: video 1280x720 stream 1: audio 2 channels stream 2: subtitles (image) Example: automatic stream selection ffmpeg -i A.avi -i B.mp4 out1.mkv out2.wav -map 1:a -c:a copy out3.mov There are three output files specified, and for the first two, no "-map" options are set, so ffmpeg will select streams for these two files automatically. out1.mkv is a Matroska container file and accepts video, audio and subtitle streams, so ffmpeg will try to select one of each type.For video, it will select "stream 0" from B.mp4, which has the highest resolution among all the input video streams.For audio, it will select "stream 3" from B.mp4, since it has the greatest number of channels.For subtitles, it will select "stream 2" from B.mp4, which is the first subtitle stream from among A.avi and B.mp4. out2.wav accepts only audio streams, so only "stream 3" from B.mp4 is selected. For out3.mov, since a "-map" option is set, no automatic stream selection will occur. The "-map 1:a" option will select all audio streams from the second input B.mp4. No other streams will be included in this output file. For the first two outputs, all included streams will be transcoded. The encoders chosen will be the default ones registered by each output format, which may not match the codec of the selected input streams. For the third output, codec option for audio streams has been set to "copy", so no decoding-filtering-encoding operations will occur, or can occur. Packets of selected streams shall be conveyed from the input file and muxed within the output file. Example: automatic subtitles selection ffmpeg -i C.mkv out1.mkv -c:s dvdsub -an out2.mkv Although out1.mkv is a Matroska container file which accepts subtitle streams, only a video and audio stream shall be selected. The subtitle stream of C.mkv is image-based and the default subtitle encoder of the Matroska muxer is text-based, so a transcode operation for the subtitles is expected to fail and hence the stream isn't selected. However, in out2.mkv, a subtitle encoder is specified in the command and so, the subtitle stream is selected, in addition to the video stream. The presence of "-an" disables audio stream selection for out2.mkv. Example: unlabeled filtergraph outputs ffmpeg -i A.avi -i C.mkv -i B.mp4 -filter_complex "overlay" out1.mp4 out2.srt A filtergraph is setup here using the "-filter_complex" option and consists of a single video filter. The "overlay" filter requires exactly two video inputs, but none are specified, so the first two available video streams are used, those of A.avi and C.mkv. The output pad of the filter has no label and so is sent to the first output file out1.mp4. Due to this, automatic selection of the video stream is skipped, which would have selected the stream in B.mp4. The audio stream with most channels viz. "stream 3" in B.mp4, is chosen automatically. No subtitle stream is chosen however, since the MP4 format has no default subtitle encoder registered, and the user hasn't specified a subtitle encoder. The 2nd output file, out2.srt, only accepts text-based subtitle streams. So, even though the first subtitle stream available belongs to C.mkv, it is image-based and hence skipped. The selected stream, "stream 2" in B.mp4, is the first text-based subtitle stream. Example: labeled filtergraph outputs ffmpeg -i A.avi -i B.mp4 -i C.mkv -filter_complex "[1:v]hue=s=0[outv];overlay;aresample" \ -map '[outv]' -an out1.mp4 \ out2.mkv \ -map '[outv]' -map 1:a:0 out3.mkv The above command will fail, as the output pad labelled "[outv]" has been mapped twice. None of the output files shall be processed. ffmpeg -i A.avi -i B.mp4 -i C.mkv -filter_complex "[1:v]hue=s=0[outv];overlay;aresample" \ -an out1.mp4 \ out2.mkv \ -map 1:a:0 out3.mkv This command above will also fail as the hue filter output has a label, "[outv]", and hasn't been mapped anywhere. The command should be modified as follows, ffmpeg -i A.avi -i B.mp4 -i C.mkv -filter_complex "[1:v]hue=s=0,split=2[outv1][outv2];overlay;aresample" \ -map '[outv1]' -an out1.mp4 \ out2.mkv \ -map '[outv2]' -map 1:a:0 out3.mkv The video stream from B.mp4 is sent to the hue filter, whose output is cloned once using the split filter, and both outputs labelled. Then a copy each is mapped to the first and third output files. The overlay filter, requiring two video inputs, uses the first two unused video streams. Those are the streams from A.avi and C.mkv. The overlay output isn't labelled, so it is sent to the first output file out1.mp4, regardless of the presence of the "-map" option. The aresample filter is sent the first unused audio stream, that of A.avi. Since this filter output is also unlabelled, it too is mapped to the first output file. The presence of "-an" only suppresses automatic or manual stream selection of audio streams, not outputs sent from filtergraphs. Both these mapped streams shall be ordered before the mapped stream in out1.mp4. The video, audio and subtitle streams mapped to "out2.mkv" are entirely determined by automatic stream selection. out3.mkv consists of the cloned video output from the hue filter and the first audio stream from B.mp4. Video and Audio grabbing If you specify the input format and device then ffmpeg can grab video and audio directly. ffmpeg -f oss -i /dev/dsp -f video4linux2 -i /dev/video0 /tmp/out.mpg Or with an ALSA audio source (mono input, card id 1) instead of OSS: ffmpeg -f alsa -ac 1 -i hw:1 -f video4linux2 -i /dev/video0 /tmp/out.mpg Note that you must activate the right video source and channel before launching ffmpeg with any TV viewer such as <http://linux.bytesex.org/xawtv/> by Gerd Knorr. You also have to set the audio recording levels correctly with a standard mixer. X11 grabbing Grab the X11 display with ffmpeg via ffmpeg -f x11grab -video_size cif -framerate 25 -i :0.0 /tmp/out.mpg 0.0 is display.screen number of your X11 server, same as the DISPLAY environment variable. ffmpeg -f x11grab -video_size cif -framerate 25 -i :0.0+10,20 /tmp/out.mpg 0.0 is display.screen number of your X11 server, same as the DISPLAY environment variable. 10 is the x-offset and 20 the y-offset for the grabbing. Video and Audio file format conversion Any supported file format and protocol can serve as input to ffmpeg: Examples: • You can use YUV files as input: ffmpeg -i /tmp/test%d.Y /tmp/out.mpg It will use the files: /tmp/test0.Y, /tmp/test0.U, /tmp/test0.V, /tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc... The Y files use twice the resolution of the U and V files. They are raw files, without header. They can be generated by all decent video decoders. You must specify the size of the image with the -s option if ffmpeg cannot guess it. • You can input from a raw YUV420P file: ffmpeg -i /tmp/test.yuv /tmp/out.avi test.yuv is a file containing raw YUV planar data. Each frame is composed of the Y plane followed by the U and V planes at half vertical and horizontal resolution. • You can output to a raw YUV420P file: ffmpeg -i mydivx.avi hugefile.yuv • You can set several input files and output files: ffmpeg -i /tmp/a.wav -s 640x480 -i /tmp/a.yuv /tmp/a.mpg Converts the audio file a.wav and the raw YUV video file a.yuv to MPEG file a.mpg. • You can also do audio and video conversions at the same time: ffmpeg -i /tmp/a.wav -ar 22050 /tmp/a.mp2 Converts a.wav to MPEG audio at 22050 Hz sample rate. • You can encode to several formats at the same time and define a mapping from input stream to output streams: ffmpeg -i /tmp/a.wav -map 0:a -b:a 64k /tmp/a.mp2 -map 0:a -b:a 128k /tmp/b.mp2 Converts a.wav to a.mp2 at 64 kbits and to b.mp2 at 128 kbits. '-map file:index' specifies which input stream is used for each output stream, in the order of the definition of output streams. • You can transcode decrypted VOBs: ffmpeg -i snatch_1.vob -f avi -c:v mpeg4 -b:v 800k -g 300 -bf 2 -c:a libmp3lame -b:a 128k snatch.avi This is a typical DVD ripping example; the input is a VOB file, the output an AVI file with MPEG-4 video and MP3 audio. Note that in this command we use B-frames so the MPEG-4 stream is DivX5 compatible, and GOP size is 300 which means one intra frame every 10 seconds for 29.97fps input video. Furthermore, the audio stream is MP3-encoded so you need to enable LAME support by passing "--enable-libmp3lame" to configure. The mapping is particularly useful for DVD transcoding to get the desired audio language. NOTE: To see the supported input formats, use "ffmpeg -demuxers". • You can extract images from a video, or create a video from many images: For extracting images from a video: ffmpeg -i foo.avi -r 1 -s WxH -f image2 foo-%03d.jpeg This will extract one video frame per second from the video and will output them in files named foo-001.jpeg, foo-002.jpeg, etc. Images will be rescaled to fit the new WxH values. If you want to extract just a limited number of frames, you can use the above command in combination with the "-frames:v" or "-t" option, or in combination with -ss to start extracting from a certain point in time. For creating a video from many images: ffmpeg -f image2 -framerate 12 -i foo-%03d.jpeg -s WxH foo.avi The syntax "foo-%03d.jpeg" specifies to use a decimal number composed of three digits padded with zeroes to express the sequence number. It is the same syntax supported by the C printf function, but only formats accepting a normal integer are suitable. When importing an image sequence, -i also supports expanding shell- like wildcard patterns (globbing) internally, by selecting the image2-specific "-pattern_type glob" option. For example, for creating a video from filenames matching the glob pattern "foo-*.jpeg": ffmpeg -f image2 -pattern_type glob -framerate 12 -i 'foo-*.jpeg' -s WxH foo.avi • You can put many streams of the same type in the output: ffmpeg -i test1.avi -i test2.avi -map 1:1 -map 1:0 -map 0:1 -map 0:0 -c copy -y test12.nut The resulting output file test12.nut will contain the first four streams from the input files in reverse order. • To force CBR video output: ffmpeg -i myfile.avi -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k out.m2v • The four options lmin, lmax, mblmin and mblmax use 'lambda' units, but you may use the QP2LAMBDA constant to easily convert from 'q' units: ffmpeg -i src.ext -lmax 21*QP2LAMBDA dst.ext SEE ALSO ffmpeg-all(1), ffplay(1), ffprobe(1), ffmpeg-utils(1), ffmpeg-scaler(1), ffmpeg-resampler(1), ffmpeg-codecs(1), ffmpeg-bitstream-filters(1), ffmpeg-formats(1), ffmpeg-devices(1), ffmpeg-protocols(1), ffmpeg-filters(1) AUTHORS The FFmpeg developers. For details about the authorship, see the Git history of the project (https://git.ffmpeg.org/ffmpeg), e.g. by typing the command git log in the FFmpeg source directory, or browsing the online repository at <https://git.ffmpeg.org/ffmpeg>. Maintainers for the specific components are listed in the file MAINTAINERS in the source code tree. FFMPEG(1)
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redis-check-rdb
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iusql
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isql and iusql are command-line tools allowing users to execute SQL interactively or in batches. The tools provide several useful features, including an option to generate output wrapped in an HTML table. iusql is the same as isql but includes built-in Unicode support. Some data sources only work with iusql. An important difference between the two tools is that isql connects using SQLConnect and iusql connects using SQLDriverConnect. ARGUMENTS DSN The Data Source Name (DSN) used to connect to the SQL database. unixODBC looks for the specified DSN in /etc/odbc.ini and $HOME/.odbc.ini, with the latter taking precedence. When searching the configuration files, unixODBC looks for a bare name. If the DSN begins with a semicolon, it is treated as a connection string. The connection string can contain a DSN and/or other semicolon-separated parameters. USER Specifies the database user or role under which the connection should be made. This parameter overrides any UID specified in the data source configuration files. PASSWORD Password required to access the database for the specified USER. This parameter overrides any PASSWORD specified in the data source configuration files. When using iusql, passwords containing semicolons should be escaped with braces (curly brackets) and terminated with a semicolon. Refer to the Examples section below for syntax. "ConnectionString" A connection string starting with DSN=, DRIVER= or FILEDSN= will be passed unchanged to SQLDriverConnect. This option allows for the use of more complex syntax in a connection string than would otherwise be possible by just using DSN, UID and PWD. It also (and this was the main reason for its inclusion) allows passwords to contain semicolons without having to add complex escape syntax to the existing code.
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isql, iusql - unixODBC interactive SQL command-line tools
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isql DSN [USER [PASSWORD]] [options] iusql DSN [USER [PASSWORD]] [options] iusql "ConnectionString" [options]
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-b Run 'isql' in non-interactive batch mode. In this mode, 'isql' processes from standard input, expecting one SQL command per line. -dDELIMITER Delimit columns with the specified delimiter. -xHEX Delimit columns with the character represented in hexadecimal by HEX. The hexadecimal code must be in the format 0xNN (e.g. 0x09 for the TAB character). -w Format the result as an HTML table. -c Output the names of the columns on the first row. This option can only be used with the -d or -x options. -mNUM Limit the column display width to NUM characters. -lLOCALE Set the character locale to LOCALE. -q Wrap the character fields in double quotes. -3 Use calls from ODBC version 3. -n Process multiple lines of SQL, terminated with the GO command. -e Use SQLExecDirect instead of Prepare. -k Use SQLDriverConnect. -v Enable verbose mode, fully describing all errors. This option is useful for debugging. --version Display the program version. -LNUM Set the maximum number of characters displayed from a character field to NUM. The default value is 300 characters. COMMANDS This section briefly describes some isql and iusql run-time commands. help List all tables in the database. help table List all columns in the table. help help List all help options.
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A bare DSN: $ iusql WebDB MyID MyPWD -w -b < My.sql Connects to the WebDB DSN as user MyID with password MyPWD, then executes the commands in the My.sql file and returns the results wrapped in an HTML table. Each line in My.sql must only contain one SQL command, except for the last line, which must be blank (unless the -n option is specified). A DSN in a connection string: Note the leading semicolon on the connection string. $ iusql ";DSN=WebDB" MyID MyPWD -w -b < My.sql Options in the DSN may be overridden in the connection string: $ iusql ";DSN=WebDB;Driver=PostgreSQL ODBC;UID=MyID;PASSWORD=secret;Debug=1;CommLog=1" -v A string DSN: A string DSN may be provided in its entirety, with no file DSN reference at all: $ iusql ";Driver=PostgreSQL Unicode;UID=MyID;PASSWORD=secret" -v A password containing a semicolon (iusql): $ iusql WebDB MyID '{My;PWD};' $ iusql 'DSN=WebDB;UID=MyID;PWD={My;PWD};' TROUBLESHOOTING Cryptic error messages Re-run isql or iusql with the -v flag to get more information from errors, and/or enable Trace mode in odbcinst.ini. Missing driver definition Check that the driver name specified by the Driver entry in the odbc.ini data-source definition is present in odbcinst.ini and exactly matches the odbcinst.ini [section name]. Unloadable or incompatible driver If the ODBC driver is properly specified for the data source, it is possible that the driver is not loadable. Check for mix-ups between Unicode and ANSI drivers, and verify the driver paths in the odbcinst.ini [section name]. Unicode data sources with ANSI clients Some data sources are Unicode-only and require the use of iusql. If isql reports [IM002][unixODBC][Driver Manager]Data source name not found and no default driver specified [ISQL]ERROR: Could not SQLConnect but the data source and driver required are listed by odbcinst -q -d and odbcinst -q -s then try iusql. FILES /etc/odbc.ini Configuration file containing system-wide Data Source Name (DSN) definitions. See odbc.ini(5) for more information. $HOME/.odbc.ini Configuration file containing user-specific Data Source Name (DSN) definitions. See odbc.ini(5) for more information. SEE ALSO unixODBC(7), odbcinst(1), odbc.ini(5) "The unixODBC Administrator Manual (HTML)" AUTHORS The authors of unixODBC are Peter Harvey <pharvey@codebydesign.com> and Nick Gorham <nick@lurcher.org>. For a full list of contributors, refer to the AUTHORS file. COPYRIGHT unixODBC is licensed under the GNU Lesser General Public License. For details about the license, see the COPYING file. version 2.3.12 Thu 14 Jan 2021 isql(1)
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tificc
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lcms is a standalone CMM engine, which deals with the color management. It implements a fast transformation between ICC profiles. tificc is a little cms ICC profile applier for TIFF.
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tificc - little cms ICC profile applier for TIFF.
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tificc [options] input.tif output.tif
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-a Handle channels > 4 as alpha. -b Black point compensation. -c NUM Precalculates transform (0=Off, 1=Normal, 2=Hi-res, 3=LoRes) [defaults to 1]. -d NUM Observer adaptation state (abs.col. only), (0..1.0, float value) [defaults to 0.0]. -e Embed destination profile. -g Marks out-of-gamut colors on softproof. -h NUM Show summary of options and examples (0=help, 1=Examples, 2=Built-in profiles, 3=Contact information) -i profile Input profile (defaults to sRGB). -k inklimit Ink-limiting in % (CMYK only), (0..400.0, float value) [default 400.0]. -l profile Transform by device-link profile. -m TODO: check if values outside 0..3 are possible SoftProof intent [defaults to 0]. -n Ignore embedded profile on input. -o profile Output profile (defaults to sRGB). -p profile Soft proof profile. -s newprofile Save embedded profile as newprofile. -t NUM Rendering intent 0=Perceptual [default] 1=Relative colorimetric 2=Saturation 3=Absolute colorimetric 10=Perceptual preserving black ink 11=Relative colorimetric preserving black ink 12=Saturation preserving black ink 13=Perceptual preserving black plane 14=Relative colorimetric preserving black plane 15=Saturation preserving black plane -v Verbose. -w NUM Output depth (8, 16 or 32). Use 32 for floating-point. BUILT-IN PROFILES *Lab2 -- D50-based v2 CIEL*a*b *Lab4 -- D50-based v4 CIEL*a*b *Lab -- D50-based v4 CIEL*a*b *XYZ -- CIE XYZ (PCS) *sRGB -- sRGB color space *Gray22 - Monochrome of Gamma 2.2 *Gray30 - Monochrome of Gamma 3.0 *null - Monochrome black for all input *Lin2222- CMYK linearization of gamma 2.2 on each channel
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To color correct from scanner to sRGB: tificc -iscanner.icm in.tif out.tif To convert from monitor1 to monitor2: tificc -imon1.icm -omon2.icm in.tif out.tif To make a CMYK separation: tificc -oprinter.icm inrgb.tif outcmyk.tif To recover sRGB from a CMYK separation: tificc -iprinter.icm incmyk.tif outrgb.tif To convert from CIELab TIFF to sRGB tificc -i*Lab in.tif out.tif NOTES For suggestions, comments, bug reports etc. send mail to info@littlecms.com. SEE ALSO jpgicc(1), linkicc(1), psicc(1), transicc(1) AUTHOR This manual page was originally written by Shiju p. Nair <shiju.p@gmail.com>, for the Debian project. Modified by Marti Maria to reflect further changes. October 23, 2004 TIFICC(1)
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grmdir
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Remove the DIRECTORY(ies), if they are empty. --ignore-fail-on-non-empty ignore each failure to remove a non-empty directory -p, --parents remove DIRECTORY and its ancestors; e.g., 'rmdir -p a/b' is similar to 'rmdir a/b a' -v, --verbose output a diagnostic for every directory processed --help display this help and exit --version output version information and exit AUTHOR Written by David MacKenzie. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO rmdir(2) Full documentation <https://www.gnu.org/software/coreutils/rmdir> or available locally via: info '(coreutils) rmdir invocation' GNU coreutils 9.3 April 2023 RMDIR(1)
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rmdir - remove empty directories
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rmdir [OPTION]... DIRECTORY...
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markdown_py
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pinentry
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instmodsh
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A little interface to ExtUtils::Installed to examine installed modules, validate your packlists and even create a tarball from an installed module. SEE ALSO ExtUtils::Installed perl v5.38.2 2023-11-28 INSTMODSH(1)
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instmodsh - A shell to examine installed modules
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instmodsh
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ngrok
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oidcalc
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gfold
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Wrap input lines in each FILE, writing to standard output. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. -b, --bytes count bytes rather than columns -s, --spaces break at spaces -w, --width=WIDTH use WIDTH columns instead of 80 --help display this help and exit --version output version information and exit AUTHOR Written by David MacKenzie. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO fmt(1) Full documentation <https://www.gnu.org/software/coreutils/fold> or available locally via: info '(coreutils) fold invocation' GNU coreutils 9.3 April 2023 FOLD(1)
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fold - wrap each input line to fit in specified width
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fold [OPTION]... [FILE]...
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vfychain
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supervisord
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vfyserv
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zmqsend
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2to3-3.12
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benchmark_app
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gnl
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Write each FILE to standard output, with line numbers added. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. -b, --body-numbering=STYLE use STYLE for numbering body lines -d, --section-delimiter=CC use CC for logical page delimiters -f, --footer-numbering=STYLE use STYLE for numbering footer lines -h, --header-numbering=STYLE use STYLE for numbering header lines -i, --line-increment=NUMBER line number increment at each line -l, --join-blank-lines=NUMBER group of NUMBER empty lines counted as one -n, --number-format=FORMAT insert line numbers according to FORMAT -p, --no-renumber do not reset line numbers for each section -s, --number-separator=STRING add STRING after (possible) line number -v, --starting-line-number=NUMBER first line number for each section -w, --number-width=NUMBER use NUMBER columns for line numbers --help display this help and exit --version output version information and exit Default options are: -bt -d'\:' -fn -hn -i1 -l1 -n'rn' -s<TAB> -v1 -w6 CC are two delimiter characters used to construct logical page delimiters; a missing second character implies ':'. As a GNU extension one can specify more than two characters, and also specifying the empty string (-d '') disables section matching. STYLE is one of: a number all lines t number only nonempty lines n number no lines pBRE number only lines that contain a match for the basic regular expression, BRE FORMAT is one of: ln left justified, no leading zeros rn right justified, no leading zeros rz right justified, leading zeros AUTHOR Written by Scott Bartram and David MacKenzie. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO Full documentation <https://www.gnu.org/software/coreutils/nl> or available locally via: info '(coreutils) nl invocation' GNU coreutils 9.3 April 2023 NL(1)
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nl - number lines of files
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nl [OPTION]... [FILE]...
| null | null |
pdfinfo
|
Pdfinfo prints the contents of the ´Info' dictionary (plus some other useful information) from a Portable Document Format (PDF) file. If PDF-file is ´-', it reads the PDF file from stdin. The ´Info' dictionary contains the following values: title subject keywords author creator producer creation date modification date In addition, the following information is printed: custom metadata (yes/no) metadata stream (yes/no) tagged (yes/no) userproperties (yes/no) suspects (yes/no) form (AcroForm / XFA / none) javascript (yes/no) page count encrypted flag (yes/no) print and copy permissions (if encrypted) page size file size linearized (yes/no) PDF version metadata (only if requested) The options -listenc, -meta, -js, -struct, and -struct-text only print the requested information. The 'Info' dictionary and related data listed above is not printed. At most one of these five options may be used.
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pdfinfo - Portable Document Format (PDF) document information extractor (version 3.03)
|
pdfinfo [options] [PDF-file]
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-f number Specifies the first page to examine. If multiple pages are requested using the "-f" and "-l" options, the size of each requested page (and, optionally, the bounding boxes for each requested page) are printed. Otherwise, only page one is examined. -l number Specifies the last page to examine. -box Prints the page box bounding boxes: MediaBox, CropBox, BleedBox, TrimBox, and ArtBox. -meta Prints document-level metadata. (This is the "Metadata" stream from the PDF file's Catalog object.) -custom Prints custom and standard metadata. -js Prints all JavaScript in the PDF. -struct Prints the logical document structure of a Tagged-PDF file. -struct-text Print the textual content along with the document structure of a Tagged-PDF file. Note that extracting text this way might be slow for big PDF files. (Implies -struct.) -url Print all URLs in the PDF. Only the URL types supported by Poppler are listed. Currently, this is limited to Annotations. Note: only URLs referenced by the PDF objects such as Link Annotations are listed. pdfinfo does not attempt to extract strings matching http://... from the text content. -isodates Prints dates in ISO-8601 format (including the time zone). -rawdates Prints the raw (undecoded) date strings, directly from the PDF file. -dests Print a list of all named destinations. If a page range is specified using "-f" and "-l", only destinations in the page range are listed. -enc encoding-name Sets the encoding to use for text output. This defaults to "UTF-8". -listenc Lits the available encodings -opw password Specify the owner password for the PDF file. Providing this will bypass all security restrictions. -upw password Specify the user password for the PDF file. -v Print copyright and version information. -h Print usage information. (-help and --help are equivalent.) EXIT CODES The Xpdf tools use the following exit codes: 0 No error. 1 Error opening a PDF file. 2 Error opening an output file. 3 Error related to PDF permissions. 99 Other error. AUTHOR The pdfinfo software and documentation are copyright 1996-2011 Glyph & Cog, LLC. SEE ALSO pdfdetach(1), pdffonts(1), pdfimages(1), pdftocairo(1), pdftohtml(1), pdftoppm(1), pdftops(1), pdftotext(1) pdfseparate(1), pdfsig(1), pdfunite(1) 15 August 2011 pdfinfo(1)
| null |
sexp-conv
| null | null | null | null | null |
perlivp
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The perlivp program is set up at Perl source code build time to test the Perl version it was built under. It can be used after running: make install (or your platform's equivalent procedure) to verify that perl and its libraries have been installed correctly. A correct installation is verified by output that looks like: ok 1 ok 2 etc.
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perlivp - Perl Installation Verification Procedure
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perlivp [-p] [-v] [-h]
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-h help Prints out a brief help message. -p print preface Gives a description of each test prior to performing it. -v verbose Gives more detailed information about each test, after it has been performed. Note that any failed tests ought to print out some extra information whether or not -v is thrown. DIAGNOSTICS • print "# Perl binary '$perlpath' does not appear executable.\n"; Likely to occur for a perl binary that was not properly installed. Correct by conducting a proper installation. • print "# Perl version '$]' installed, expected $ivp_VERSION.\n"; Likely to occur for a perl that was not properly installed. Correct by conducting a proper installation. • print "# Perl \@INC directory '$_' does not appear to exist.\n"; Likely to occur for a perl library tree that was not properly installed. Correct by conducting a proper installation. • print "# Needed module '$_' does not appear to be properly installed.\n"; One of the two modules that is used by perlivp was not present in the installation. This is a serious error since it adversely affects perlivp's ability to function. You may be able to correct this by performing a proper perl installation. • print "# Required module '$_' does not appear to be properly installed.\n"; An attempt to "eval "require $module"" failed, even though the list of extensions indicated that it should succeed. Correct by conducting a proper installation. • print "# Unnecessary module 'bLuRfle' appears to be installed.\n"; This test not coming out ok could indicate that you have in fact installed a bLuRfle.pm module or that the "eval " require \"$module_name.pm\"; "" test may give misleading results with your installation of perl. If yours is the latter case then please let the author know. • print "# file",+($#missing == 0) ? '' : 's'," missing from installation:\n"; One or more files turned up missing according to a run of "ExtUtils::Installed -> validate()" over your installation. Correct by conducting a proper installation. For further information on how to conduct a proper installation consult the INSTALL file that comes with the perl source and the README file for your platform. AUTHOR Peter Prymmer perl v5.38.2 2023-11-28 PERLIVP(1)
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tree-sitter
| null | null | null | null | null |
greadlink
|
Note realpath(1) is the preferred command to use for canonicalization functionality. Print value of a symbolic link or canonical file name -f, --canonicalize canonicalize by following every symlink in every component of the given name recursively; all but the last component must exist -e, --canonicalize-existing canonicalize by following every symlink in every component of the given name recursively, all components must exist -m, --canonicalize-missing canonicalize by following every symlink in every component of the given name recursively, without requirements on components existence -n, --no-newline do not output the trailing delimiter -q, --quiet -s, --silent suppress most error messages (on by default) -v, --verbose report error messages -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit AUTHOR Written by Dmitry V. Levin. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO readlink(2), realpath(1), realpath(3) Full documentation <https://www.gnu.org/software/coreutils/readlink> or available locally via: info '(coreutils) readlink invocation' GNU coreutils 9.3 April 2023 READLINK(1)
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readlink - print resolved symbolic links or canonical file names
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readlink [OPTION]... FILE...
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gshred
|
Overwrite the specified FILE(s) repeatedly, in order to make it harder for even very expensive hardware probing to recover the data. If FILE is -, shred standard output. Mandatory arguments to long options are mandatory for short options too. -f, --force change permissions to allow writing if necessary -n, --iterations=N overwrite N times instead of the default (3) --random-source=FILE get random bytes from FILE -s, --size=N shred this many bytes (suffixes like K, M, G accepted) -u deallocate and remove file after overwriting --remove[=HOW] like -u but give control on HOW to delete; See below -v, --verbose show progress -x, --exact do not round file sizes up to the next full block; this is the default for non-regular files -z, --zero add a final overwrite with zeros to hide shredding --help display this help and exit --version output version information and exit Delete FILE(s) if --remove (-u) is specified. The default is not to remove the files because it is common to operate on device files like /dev/hda, and those files usually should not be removed. The optional HOW parameter indicates how to remove a directory entry: 'unlink' => use a standard unlink call. 'wipe' => also first obfuscate bytes in the name. 'wipesync' => also sync each obfuscated byte to the device. The default mode is 'wipesync', but note it can be expensive. CAUTION: shred assumes the file system and hardware overwrite data in place. Although this is common, many platforms operate otherwise. Also, backups and mirrors may contain unremovable copies that will let a shredded file be recovered later. See the GNU coreutils manual for details. AUTHOR Written by Colin Plumb. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO Full documentation <https://www.gnu.org/software/coreutils/shred> or available locally via: info '(coreutils) shred invocation' GNU coreutils 9.3 April 2023 SHRED(1)
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shred - overwrite a file to hide its contents, and optionally delete it
|
shred [OPTION]... FILE...
| null | null |
wheel3.10
| null | null | null | null | null |
gmv
|
Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY. Mandatory arguments to long options are mandatory for short options too. --backup[=CONTROL] make a backup of each existing destination file -b like --backup but does not accept an argument --debug explain how a file is copied. Implies -v -f, --force do not prompt before overwriting -i, --interactive prompt before overwrite -n, --no-clobber do not overwrite an existing file If you specify more than one of -i, -f, -n, only the final one takes effect. --no-copy do not copy if renaming fails --strip-trailing-slashes remove any trailing slashes from each SOURCE argument -S, --suffix=SUFFIX override the usual backup suffix -t, --target-directory=DIRECTORY move all SOURCE arguments into DIRECTORY -T, --no-target-directory treat DEST as a normal file --update[=UPDATE] control which existing files are updated; UPDATE={all,none,older(default)}. See below -u equivalent to --update[=older] -v, --verbose explain what is being done -Z, --context set SELinux security context of destination file to default type --help display this help and exit --version output version information and exit UPDATE controls which existing files in the destination are replaced. 'all' is the default operation when an --update option is not specified, and results in all existing files in the destination being replaced. 'none' is similar to the --no-clobber option, in that no files in the destination are replaced, but also skipped files do not induce a failure. 'older' is the default operation when --update is specified, and results in files being replaced if they're older than the corresponding source file. The backup suffix is '~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX. The version control method may be selected via the --backup option or through the VERSION_CONTROL environment variable. Here are the values: none, off never make backups (even if --backup is given) numbered, t make numbered backups existing, nil numbered if numbered backups exist, simple otherwise simple, never always make simple backups AUTHOR Written by Mike Parker, David MacKenzie, and Jim Meyering. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO rename(2) Full documentation <https://www.gnu.org/software/coreutils/mv> or available locally via: info '(coreutils) mv invocation' GNU coreutils 9.3 April 2023 MV(1)
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mv - move (rename) files
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mv [OPTION]... [-T] SOURCE DEST mv [OPTION]... SOURCE... DIRECTORY mv [OPTION]... -t DIRECTORY SOURCE...
| null | null |
c_rehash
|
This command is generally equivalent to the external script c_rehash, except for minor differences noted below. openssl rehash scans directories and calculates a hash value of each .pem, .crt, .cer, or .crl file in the specified directory list and creates symbolic links for each file, where the name of the link is the hash value. (If the platform does not support symbolic links, a copy is made.) This command is useful as many programs that use OpenSSL require directories to be set up like this in order to find certificates. If any directories are named on the command line, then those are processed in turn. If not, then the SSL_CERT_DIR environment variable is consulted; this should be a colon-separated list of directories, like the Unix PATH variable. If that is not set then the default directory (installation-specific but often /usr/local/ssl/certs) is processed. In order for a directory to be processed, the user must have write permissions on that directory, otherwise an error will be generated. The links created are of the form HHHHHHHH.D, where each H is a hexadecimal character and D is a single decimal digit. When a directory is processed, all links in it that have a name in that syntax are first removed, even if they are being used for some other purpose. To skip the removal step, use the -n flag. Hashes for CRL's look similar except the letter r appears after the period, like this: HHHHHHHH.rD. Multiple objects may have the same hash; they will be indicated by incrementing the D value. Duplicates are found by comparing the full SHA-1 fingerprint. A warning will be displayed if a duplicate is found. A warning will also be displayed if there are files that cannot be parsed as either a certificate or a CRL or if more than one such object appears in the file. Script Configuration The c_rehash script uses the openssl program to compute the hashes and fingerprints. If not found in the user's PATH, then set the OPENSSL environment variable to the full pathname. Any program can be used, it will be invoked as follows for either a certificate or CRL: $OPENSSL x509 -hash -fingerprint -noout -in FILENAME $OPENSSL crl -hash -fingerprint -noout -in FILENAME where FILENAME is the filename. It must output the hash of the file on the first line, and the fingerprint on the second, optionally prefixed with some text and an equals sign.
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openssl-rehash, c_rehash - Create symbolic links to files named by the hash values
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openssl rehash [-h] [-help] [-old] [-compat] [-n] [-v] [-provider name] [-provider-path path] [-propquery propq] [directory] ... c_rehash [-h] [-help] [-old] [-n] [-v] [-provider name] [-provider-path path] [-propquery propq] [directory] ...
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-help -h Display a brief usage message. -old Use old-style hashing (MD5, as opposed to SHA-1) for generating links to be used for releases before 1.0.0. Note that current versions will not use the old style. -n Do not remove existing links. This is needed when keeping new and old-style links in the same directory. -compat Generate links for both old-style (MD5) and new-style (SHA1) hashing. This allows releases before 1.0.0 to use these links along-side newer releases. -v Print messages about old links removed and new links created. By default, this command only lists each directory as it is processed. -provider name -provider-path path -propquery propq See "Provider Options" in openssl(1), provider(7), and property(7). ENVIRONMENT OPENSSL The path to an executable to use to generate hashes and fingerprints (see above). SSL_CERT_DIR Colon separated list of directories to operate on. Ignored if directories are listed on the command line. SEE ALSO openssl(1), openssl-crl(1), openssl-x509(1) COPYRIGHT Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved. Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>. 3.3.1 2024-06-04 OPENSSL-REHASH(1ssl)
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pp
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pp creates standalone executables from Perl programs, using the compressed packager provided by PAR, and dependency detection heuristics offered by Module::ScanDeps. Source files are compressed verbatim without compilation. You may think of pp as "perlcc that works without hassle". :-) A GUI interface is also available as the tkpp command. It does not provide the compilation-step acceleration provided by perlcc (however, see -f below for byte-compiled, source-hiding techniques), but makes up for it with better reliability, smaller executable size, and full retrieval of original source code. When a single input program is specified, the resulting executable will behave identically as that program. However, when multiple programs are packaged, the produced executable will run the one that has the same basename as $0 (i.e. the filename used to invoke it). If nothing matches, it dies with the error "Can't open perl script "$0"".
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pp - PAR Packager
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pp [ -ABCEFILMPTSVXacdefghilmnoprsuvxz ] [ parfile | scriptfile ]...
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Options are available in a short form and a long form. For example, the three lines below are all equivalent: % pp -o output.exe input.pl % pp --output output.exe input.pl % pp --output=output.exe input.pl Since the command lines can become sufficiently long to reach the limits imposed by some shells, it is possible to have pp read some of its options from one or more text files. The basic usage is to just include an argument starting with an 'at' (@) sigil. This argument will be interpreted as a file to read options from. Mixing ordinary options and @file options is possible. This is implemented using the Getopt::ArgvFile module, so read its documentation for advanced usage. -a, --addfile=FILE|DIR Add an extra file into the package. If the file is a directory, recursively add all files inside that directory, with links turned into actual files. By default, files are placed under "/" inside the package with their original names. You may override this by appending the target filename after a ";", like this: % pp -a "old_filename.txt;new_filename.txt" % pp -a "old_dirname;new_dirname" You may specify "-a" multiple times. -A, --addlist=FILE Read a list of file/directory names from FILE, adding them into the package. Each line in FILE is taken as an argument to -a above. You may specify "-A" multiple times. -B, --bundle Bundle core modules in the resulting package. This option is enabled by default, except when "-p" or "-P" is specified. Since PAR version 0.953, this also strips any local paths from the list of module search paths @INC before running the contained script. -C, --clean Clean up temporary files extracted from the application at runtime. By default, these files are cached in the temporary directory; this allows the program to start up faster next time. -c, --compile Run "perl -c inputfile" to determine additional run-time dependencies. -cd, --cachedeps=FILE Use FILE to cache detected dependencies. Creates FILE unless present. This will speed up the scanning process on subsequent runs. -d, --dependent Reduce the executable size by not including a copy of perl interpreter. Executables built this way will need a separate perl5x.dll or libperl.so to function correctly. This option is only available if perl is built as a shared library. -e, --eval=STRING Package a one-liner, much the same as "perl -e '...'" -E, --evalfeature=STRING Behaves just like "-e", except that it implicitly enables all optional features (in the main compilation unit) with Perl 5.10 and later. See feature. -x, --execute Run "perl inputfile" to determine additional run-time dependencies. Using this option, pp may be able to detect the use of modules that can't be determined by static analysis of "inputfile". Examples are stuff loaded by run-time loaders like Module::Runtime or "plugin" loaders like Module::Loader. Note that which modules are detected depends on which parts of your program are exercised when running "inputfile". E.g. if your program immediately terminates when run as "perl inputfile" because it lacks mandatory arguments, then this option will probably have no effect. You may use --xargs to supply arguments in this case. --xargs=STRING If -x is given, splits the "STRING" using the function "shellwords" from Text::ParseWords and passes the result as @ARGV when running "perl inputfile". -X, --exclude=MODULE Exclude the given module from the dependency search path and from the package. If the given file is a zip or par or par executable, all the files in the given file (except MANIFEST, META.yml and script/*) will be excluded and the output file will "use" the given file at runtime. -f, --filter=FILTER Filter source script(s) with a PAR::Filter subclass. You may specify multiple such filters. If you wish to hide the source code from casual prying, this will do: % pp -f Bleach source.pl If you are more serious about hiding your source code, you should have a look at Steve Hay's PAR::Filter::Crypto module. Make sure you understand the Filter::Crypto caveats! -g, --gui Build an executable that does not have a console window. This option is ignored on non-MSWin32 platforms or when "-p" is specified. -h, --help Show basic usage information. -I, --lib=DIR Add the given directory to the perl module search path. May be specified multiple times. -l, --link=FILE|LIBRARY Add the given shared library (a.k.a. shared object or DLL) into the packed file. Also accepts names under library paths; i.e. "-l ncurses" means the same thing as "-l libncurses.so" or "-l /usr/local/lib/libncurses.so" in most Unixes. May be specified multiple times. -L, --log=FILE Log the output of packaging to a file rather than to stdout. -F, --modfilter=FILTER[=REGEX], Filter included perl module(s) with a PAR::Filter subclass. You may specify multiple such filters. By default, the PodStrip filter is applied. In case that causes trouble, you can turn this off by setting the environment variable "PAR_VERBATIM" to 1. Since PAR 0.958, you can use an optional regular expression (REGEX above) to select the files in the archive which should be filtered. Example: pp -o foo.exe -F Bleach=warnings\.pm$ foo.pl This creates a binary executable foo.exe from foo.pl packaging all files as usual except for files ending in "warnings.pm" which are filtered with PAR::Filter::Bleach. -M, --module=MODULE Add the specified module into the package, along with its dependencies. The following variants may be used to add whole module namespaces: -M Foo::** Add every module in the "Foo" namespace except "Foo" itself, i.e. add "Foo::Bar", "Foo::Bar::Quux" etc up to any depth. -M Foo::* Add every module at level 1 in the "Foo" namespace, i.e. add "Foo::Bar", but neither "Foo::Bar::Quux" nor "Foo". -M Foo:: Shorthand for "-M Foo -M Foo:**": every module in the "Foo" namespace including "Foo" itself. Instead of a module name, MODULE may also be specified as a filename relative to the @INC path, i.e. "-M Module/ScanDeps.pm" means the same thing as "-M Module::ScanDeps". If MODULE has an extension that is not ".pm"/".ix"/".al", it will not be scanned for dependencies, and will be placed under "/" instead of "/lib/" inside the PAR file. This use is deprecated -- consider using the -a option instead. You may specify "-M" multiple times. -m, --multiarch Build a multi-architecture PAR file. Implies -p. -n, --noscan Skip the default static scanning altogether, using run-time dependencies from -c or -x exclusively. -N, --namespace=NAMESPACE Add all modules in the namespace into the package, along with their dependencies. If "NAMESPACE" is something like "Foo::Bar" then this will add all modules "Foo/Bar/Quux.pm", "Foo/Bar/Fred/Barnie.pm" etc that can be located in your module search path. It mimics the behaviour of "plugin" loaders like Module::Loader. This is different from using "-M Foo::Bar::", as the latter insists on adding "Foo/Bar.pm" which might not exist in the above "plugin" scenario. You may specify "-N" multiple times. -o, --output=FILE File name for the final packaged executable. -p, --par Create PAR archives only; do not package to a standalone binary. -P, --perlscript Create stand-alone perl script; do not package to a standalone binary. -r, --run Run the resulting packaged script after packaging it. --reusable EXPERIMENTAL Make the packaged executable reusable for running arbitrary, external Perl scripts as if they were part of the package: pp -o myapp --reusable someapp.pl ./myapp --par-options --reuse otherapp.pl The second line will run otherapp.pl instead of someapp.pl. -S, --save Do not delete generated PAR file after packaging. -s, --sign Cryptographically sign the generated PAR or binary file using Module::Signature. -T, --tempcache Set the program unique part of the cache directory name that is used if the program is run without -C. If not set, a hash of the executable is used. When the program is run, its contents are extracted to a temporary directory. On Unix systems, this is commonly /tmp/par-USER/cache-XXXXXXX. USER is replaced by the name of the user running the program, but "spelled" in hex. XXXXXXX is either a hash of the executable or the value passed to the "-T" or "--tempcache" switch. -u, --unicode Package Unicode support (essentially utf8_heavy.pl and everything below the directory unicore in your perl library). This option exists because it is impossible to detect using static analysis if your program needs Unicode support at runtime. (Note: If your program contains "use utf8" this does not imply it needs Unicode support. It merely says that your program is written in UTF-8.) If your packed program exits with an error message like Can't locate utf8_heavy.pl in @INC (@INC contains: ...) try to pack it with "-u" (or use "-x"). -v, --verbose[=NUMBER] Increase verbosity of output; NUMBER is an integer from 1 to 3, 3 being the most verbose. Defaults to 1 if specified without an argument. Alternatively, -vv sets verbose level to 2, and -vvv sets it to 3. -V, --version Display the version number and copyrights of this program. -z, --compress=NUMBER Set zip compression level; NUMBER is an integer from 0 to 9, 0 = no compression, 9 = max compression. Defaults to 6 if -z is not used. ENVIRONMENT PP_OPTS Command-line options (switches). Switches in this variable are taken as if they were on every pp command line. NOTES Here are some recipes showing how to utilize pp to bundle source.pl with all its dependencies, on target machines with different expected settings: Stone-alone setup: To make a stand-alone executable, suitable for running on a machine that doesn't have perl installed: % pp -o packed.exe source.pl # makes packed.exe # Now, deploy 'packed.exe' to target machine... $ packed.exe # run it Perl interpreter only, without core modules: To make a packed .pl file including core modules, suitable for running on a machine that has a perl interpreter, but where you want to be sure of the versions of the core modules that your program uses: % pp -B -P -o packed.pl source.pl # makes packed.pl # Now, deploy 'packed.pl' to target machine... $ perl packed.pl # run it Perl with core modules installed: To make a packed .pl file without core modules, relying on the target machine's perl interpreter and its core libraries. This produces a significantly smaller file than the previous version: % pp -P -o packed.pl source.pl # makes packed.pl # Now, deploy 'packed.pl' to target machine... $ perl packed.pl # run it Perl with PAR.pm and its dependencies installed: Make a separate archive and executable that uses the archive. This relies upon the perl interpreter and libraries on the target machine. % pp -p source.pl # makes source.par % echo "use PAR 'source.par';" > packed.pl; % cat source.pl >> packed.pl; # makes packed.pl # Now, deploy 'source.par' and 'packed.pl' to target machine... $ perl packed.pl # run it, perl + core modules required Note that even if your perl was built with a shared library, the 'Stand-alone executable' above will not need a separate perl5x.dll or libperl.so to function correctly. But even in this case, the underlying system libraries such as libc must be compatible between the host and target machines. Use "--dependent" if you are willing to ship the shared library with the application, which can significantly reduce the executable size. SEE ALSO tkpp, par.pl, parl, perlcc PAR, PAR::Packer, Module::ScanDeps Getopt::Long, Getopt::ArgvFile ACKNOWLEDGMENTS Simon Cozens, Tom Christiansen and Edward Peschko for writing perlcc; this program try to mimic its interface as close as possible, and copied liberally from their code. Jan Dubois for writing the exetype.pl utility, which has been partially adapted into the "-g" flag. Mattia Barbon for providing the "myldr" binary loader code. Jeff Goff for suggesting the name pp. AUTHORS Audrey Tang <cpan@audreyt.org>, Steffen Mueller <smueller@cpan.org> Roderich Schupp <rschupp@cpan.org> You can write to the mailing list at <par@perl.org>, or send an empty mail to <par-subscribe@perl.org> to participate in the discussion. Please submit bug reports to <bug-par-packer@rt.cpan.org>. COPYRIGHT Copyright 2002-2009 by Audrey Tang <cpan@audreyt.org>. Neither this program nor the associated parl program impose any licensing restrictions on files generated by their execution, in accordance with the 8th article of the Artistic License: "Aggregation of this Package with a commercial distribution is always permitted provided that the use of this Package is embedded; that is, when no overt attempt is made to make this Package's interfaces visible to the end user of the commercial distribution. Such use shall not be construed as a distribution of this Package." Therefore, you are absolutely free to place any license on the resulting executable, as long as the packed 3rd-party libraries are also available under the Artistic License. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See LICENSE. perl v5.34.0 2020-03-08 PP(1)
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Note: When running on Microsoft Windows, the a.out below will be replaced by a.exe instead. % pp hello.pl # Pack 'hello.pl' into executable 'a.out' % pp -o hello hello.pl # Pack 'hello.pl' into executable 'hello' # (or 'hello.exe' on Win32) % pp -o foo foo.pl bar.pl # Pack 'foo.pl' and 'bar.pl' into 'foo' % ./foo # Run 'foo.pl' inside 'foo' % mv foo bar; ./bar # Run 'bar.pl' inside 'foo' % mv bar baz; ./baz # Error: Can't open perl script "baz" % pp -p file # Creates a PAR file, 'a.par' % pp -o hello a.par # Pack 'a.par' to executable 'hello' % pp -S -o hello file # Combine the two steps above % pp -p -o out.par file # Creates 'out.par' from 'file' % pp -B -p -o out.par file # same as above, but bundles core modules # and removes any local paths from @INC % pp -P -o out.pl file # Creates 'out.pl' from 'file' % pp -B -p -o out.pl file # same as above, but bundles core modules # and removes any local paths from @INC # (-B is assumed when making executables) % pp -e "print 123" # Pack a one-liner into 'a.out' % pp -p -e "print 123" # Creates a PAR file 'a.par' % pp -P -e "print 123" # Creates a perl script 'a.pl' % pp -c hello # Check dependencies from "perl -c hello" % pp -x hello # Check dependencies from "perl hello" % pp -n -x hello # same as above, but skips static scanning % pp -I /foo hello # Extra include paths % pp -M Foo::Bar hello # Extra modules in the include path % pp -M abbrev.pl hello # Extra libraries in the include path % pp -X Foo::Bar hello # Exclude modules % pp -a data.txt hello # Additional data files % pp -r hello # Pack 'hello' into 'a.out', runs 'a.out' % pp -r hello a b c # Pack 'hello' into 'a.out', runs 'a.out' # with arguments 'a b c' % pp hello --log=c # Pack 'hello' into 'a.out', logs # messages into 'c' # Pack 'hello' into a console-less 'out.exe' (Win32 only) % pp --gui -o out.exe hello % pp @file hello.pl # Pack 'hello.pl' but read _additional_ # options from file 'file'
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vi
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Vim is a text editor that is upwards compatible to Vi. It can be used to edit all kinds of plain text. It is especially useful for editing programs. There are a lot of enhancements above Vi: multi level undo, multi windows and buffers, syntax highlighting, command line editing, filename completion, on-line help, visual selection, etc.. See ":help vi_diff.txt" for a summary of the differences between Vim and Vi. While running Vim a lot of help can be obtained from the on-line help system, with the ":help" command. See the ON-LINE HELP section below. Most often Vim is started to edit a single file with the command vim file More generally Vim is started with: vim [options] [filelist] If the filelist is missing, the editor will start with an empty buffer. Otherwise exactly one out of the following four may be used to choose one or more files to be edited. file .. A list of filenames. The first one will be the current file and read into the buffer. The cursor will be positioned on the first line of the buffer. You can get to the other files with the ":next" command. To edit a file that starts with a dash, precede the filelist with "--". - The file to edit is read from stdin. Commands are read from stderr, which should be a tty. -t {tag} The file to edit and the initial cursor position depends on a "tag", a sort of goto label. {tag} is looked up in the tags file, the associated file becomes the current file and the associated command is executed. Mostly this is used for C programs, in which case {tag} could be a function name. The effect is that the file containing that function becomes the current file and the cursor is positioned on the start of the function. See ":help tag-commands". -q [errorfile] Start in quickFix mode. The file [errorfile] is read and the first error is displayed. If [errorfile] is omitted, the filename is obtained from the 'errorfile' option (defaults to "AztecC.Err" for the Amiga, "errors.err" on other systems). Further errors can be jumped to with the ":cn" command. See ":help quickfix". Vim behaves differently, depending on the name of the command (the executable may still be the same file). vim The "normal" way, everything is default. ex Start in Ex mode. Go to Normal mode with the ":vi" command. Can also be done with the "-e" argument. view Start in read-only mode. You will be protected from writing the files. Can also be done with the "-R" argument. gvim gview The GUI version. Starts a new window. Can also be done with the "-g" argument. evim eview The GUI version in easy mode. Starts a new window. Can also be done with the "-y" argument. rvim rview rgvim rgview Like the above, but with restrictions. It will not be possible to start shell commands, or suspend Vim. Can also be done with the "-Z" argument.
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vim - Vi IMproved, a programmer's text editor
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vim [options] [file ..] vim [options] - vim [options] -t tag vim [options] -q [errorfile] ex view gvim gview evim eview rvim rview rgvim rgview
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The options may be given in any order, before or after filenames. Options without an argument can be combined after a single dash. +[num] For the first file the cursor will be positioned on line "num". If "num" is missing, the cursor will be positioned on the last line. +/{pat} For the first file the cursor will be positioned in the line with the first occurrence of {pat}. See ":help search-pattern" for the available search patterns. +{command} -c {command} {command} will be executed after the first file has been read. {command} is interpreted as an Ex command. If the {command} contains spaces it must be enclosed in double quotes (this depends on the shell that is used). Example: vim "+set si" main.c Note: You can use up to 10 "+" or "-c" commands. -S {file} {file} will be sourced after the first file has been read. This is equivalent to -c "source {file}". {file} cannot start with '-'. If {file} is omitted "Session.vim" is used (only works when -S is the last argument). --cmd {command} Like using "-c", but the command is executed just before processing any vimrc file. You can use up to 10 of these commands, independently from "-c" commands. -A If Vim has been compiled with ARABIC support for editing right-to-left oriented files and Arabic keyboard mapping, this option starts Vim in Arabic mode, i.e. 'arabic' is set. Otherwise an error message is given and Vim aborts. -b Binary mode. A few options will be set that makes it possible to edit a binary or executable file. -C Compatible. Set the 'compatible' option. This will make Vim behave mostly like Vi, even though a .vimrc file exists. -d Start in diff mode. There should between two to eight file name arguments. Vim will open all the files and show differences between them. Works like vimdiff(1). -d {device} Open {device} for use as a terminal. Only on the Amiga. Example: "-d con:20/30/600/150". -D Debugging. Go to debugging mode when executing the first command from a script. -e Start Vim in Ex mode, just like the executable was called "ex". -E Start Vim in improved Ex mode, just like the executable was called "exim". -f Foreground. For the GUI version, Vim will not fork and detach from the shell it was started in. On the Amiga, Vim is not restarted to open a new window. This option should be used when Vim is executed by a program that will wait for the edit session to finish (e.g. mail). On the Amiga the ":sh" and ":!" commands will not work. --nofork Foreground. For the GUI version, Vim will not fork and detach from the shell it was started in. -F If Vim has been compiled with FKMAP support for editing right-to-left oriented files and Farsi keyboard mapping, this option starts Vim in Farsi mode, i.e. 'fkmap' and 'rightleft' are set. Otherwise an error message is given and Vim aborts. -g If Vim has been compiled with GUI support, this option enables the GUI. If no GUI support was compiled in, an error message is given and Vim aborts. -h Give a bit of help about the command line arguments and options. After this Vim exits. -H If Vim has been compiled with RIGHTLEFT support for editing right-to-left oriented files and Hebrew keyboard mapping, this option starts Vim in Hebrew mode, i.e. 'hkmap' and 'rightleft' are set. Otherwise an error message is given and Vim aborts. -i {viminfo} Specifies the filename to use when reading or writing the viminfo file, instead of the default "~/.viminfo". This can also be used to skip the use of the .viminfo file, by giving the name "NONE". -L Same as -r. -l Lisp mode. Sets the 'lisp' and 'showmatch' options on. -m Modifying files is disabled. Resets the 'write' option. You can still modify the buffer, but writing a file is not possible. -M Modifications not allowed. The 'modifiable' and 'write' options will be unset, so that changes are not allowed and files can not be written. Note that these options can be set to enable making modifications. -N No-compatible mode. Resets the 'compatible' option. This will make Vim behave a bit better, but less Vi compatible, even though a .vimrc file does not exist. -n No swap file will be used. Recovery after a crash will be impossible. Handy if you want to edit a file on a very slow medium (e.g. floppy). Can also be done with ":set uc=0". Can be undone with ":set uc=200". -nb Become an editor server for NetBeans. See the docs for details. -o[N] Open N windows stacked. When N is omitted, open one window for each file. -O[N] Open N windows side by side. When N is omitted, open one window for each file. -p[N] Open N tab pages. When N is omitted, open one tab page for each file. -R Read-only mode. The 'readonly' option will be set. You can still edit the buffer, but will be prevented from accidentally overwriting a file. If you do want to overwrite a file, add an exclamation mark to the Ex command, as in ":w!". The -R option also implies the -n option (see above). The 'readonly' option can be reset with ":set noro". See ":help 'readonly'". -r List swap files, with information about using them for recovery. -r {file} Recovery mode. The swap file is used to recover a crashed editing session. The swap file is a file with the same filename as the text file with ".swp" appended. See ":help recovery". -s Silent mode. Only when started as "Ex" or when the "-e" option was given before the "-s" option. -s {scriptin} The script file {scriptin} is read. The characters in the file are interpreted as if you had typed them. The same can be done with the command ":source! {scriptin}". If the end of the file is reached before the editor exits, further characters are read from the keyboard. -T {terminal} Tells Vim the name of the terminal you are using. Only required when the automatic way doesn't work. Should be a terminal known to Vim (builtin) or defined in the termcap or terminfo file. -u {vimrc} Use the commands in the file {vimrc} for initializations. All the other initializations are skipped. Use this to edit a special kind of files. It can also be used to skip all initializations by giving the name "NONE". See ":help initialization" within vim for more details. -U {gvimrc} Use the commands in the file {gvimrc} for GUI initializations. All the other GUI initializations are skipped. It can also be used to skip all GUI initializations by giving the name "NONE". See ":help gui-init" within vim for more details. -V[N] Verbose. Give messages about which files are sourced and for reading and writing a viminfo file. The optional number N is the value for 'verbose'. Default is 10. -v Start Vim in Vi mode, just like the executable was called "vi". This only has effect when the executable is called "ex". -w {scriptout} All the characters that you type are recorded in the file {scriptout}, until you exit Vim. This is useful if you want to create a script file to be used with "vim -s" or ":source!". If the {scriptout} file exists, characters are appended. -W {scriptout} Like -w, but an existing file is overwritten. -x Use encryption when writing files. Will prompt for a crypt key. -X Don't connect to the X server. Shortens startup time in a terminal, but the window title and clipboard will not be used. -y Start Vim in easy mode, just like the executable was called "evim" or "eview". Makes Vim behave like a click-and-type editor. -Z Restricted mode. Works like the executable starts with "r". -- Denotes the end of the options. Arguments after this will be handled as a file name. This can be used to edit a filename that starts with a '-'. --clean Do not use any personal configuration (vimrc, plugins, etc.). Useful to see if a problem reproduces with a clean Vim setup. --echo-wid GTK GUI only: Echo the Window ID on stdout. --help Give a help message and exit, just like "-h". --literal Take file name arguments literally, do not expand wildcards. This has no effect on Unix where the shell expands wildcards. --noplugin Skip loading plugins. Implied by -u NONE. --remote Connect to a Vim server and make it edit the files given in the rest of the arguments. If no server is found a warning is given and the files are edited in the current Vim. --remote-expr {expr} Connect to a Vim server, evaluate {expr} in it and print the result on stdout. --remote-send {keys} Connect to a Vim server and send {keys} to it. --remote-silent As --remote, but without the warning when no server is found. --remote-wait As --remote, but Vim does not exit until the files have been edited. --remote-wait-silent As --remote-wait, but without the warning when no server is found. --serverlist List the names of all Vim servers that can be found. --servername {name} Use {name} as the server name. Used for the current Vim, unless used with a --remote argument, then it's the name of the server to connect to. --socketid {id} GTK GUI only: Use the GtkPlug mechanism to run gvim in another window. --startuptime {file} During startup write timing messages to the file {fname}. --version Print version information and exit. ON-LINE HELP Type ":help" in Vim to get started. Type ":help subject" to get help on a specific subject. For example: ":help ZZ" to get help for the "ZZ" command. Use <Tab> and CTRL-D to complete subjects (":help cmdline-completion"). Tags are present to jump from one place to another (sort of hypertext links, see ":help"). All documentation files can be viewed in this way, for example ":help syntax.txt". FILES /usr/local/lib/vim/doc/*.txt The Vim documentation files. Use ":help doc-file-list" to get the complete list. /usr/local/lib/vim/doc/tags The tags file used for finding information in the documentation files. /usr/local/lib/vim/syntax/syntax.vim System wide syntax initializations. /usr/local/lib/vim/syntax/*.vim Syntax files for various languages. /usr/local/lib/vim/vimrc System wide Vim initializations. ~/.vimrc Your personal Vim initializations. /usr/local/lib/vim/gvimrc System wide gvim initializations. ~/.gvimrc Your personal gvim initializations. /usr/local/lib/vim/optwin.vim Script used for the ":options" command, a nice way to view and set options. /usr/local/lib/vim/menu.vim System wide menu initializations for gvim. /usr/local/lib/vim/bugreport.vim Script to generate a bug report. See ":help bugs". /usr/local/lib/vim/filetype.vim Script to detect the type of a file by its name. See ":help 'filetype'". /usr/local/lib/vim/scripts.vim Script to detect the type of a file by its contents. See ":help 'filetype'". /usr/local/lib/vim/print/*.ps Files used for PostScript printing. For recent info read the VIM home page: <URL:http://www.vim.org/> SEE ALSO vimtutor(1) AUTHOR Most of Vim was made by Bram Moolenaar, with a lot of help from others. See ":help credits" in Vim. Vim is based on Stevie, worked on by: Tim Thompson, Tony Andrews and G.R. (Fred) Walter. Although hardly any of the original code remains. BUGS Probably. See ":help todo" for a list of known problems. Note that a number of things that may be regarded as bugs by some, are in fact caused by a too-faithful reproduction of Vi's behaviour. And if you think other things are bugs "because Vi does it differently", you should take a closer look at the vi_diff.txt file (or type :help vi_diff.txt when in Vim). Also have a look at the 'compatible' and 'cpoptions' options. 2021 Jun 13 VIM(1)
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clean-diff
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xzdec
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xzdec is a liblzma-based decompression-only tool for .xz (and only .xz) files. xzdec is intended to work as a drop-in replacement for xz(1) in the most common situations where a script has been written to use xz --decompress --stdout (and possibly a few other commonly used options) to decompress .xz files. lzmadec is identical to xzdec except that lzmadec supports .lzma files instead of .xz files. To reduce the size of the executable, xzdec doesn't support multithreading or localization, and doesn't read options from XZ_DEFAULTS and XZ_OPT environment variables. xzdec doesn't support displaying intermediate progress information: sending SIGINFO to xzdec does nothing, but sending SIGUSR1 terminates the process instead of displaying progress information.
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xzdec, lzmadec - Small .xz and .lzma decompressors
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xzdec [option...] [file...] lzmadec [option...] [file...]
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-d, --decompress, --uncompress Ignored for xz(1) compatibility. xzdec supports only decompression. -k, --keep Ignored for xz(1) compatibility. xzdec never creates or removes any files. -c, --stdout, --to-stdout Ignored for xz(1) compatibility. xzdec always writes the decompressed data to standard output. -q, --quiet Specifying this once does nothing since xzdec never displays any warnings or notices. Specify this twice to suppress errors. -Q, --no-warn Ignored for xz(1) compatibility. xzdec never uses the exit status 2. -h, --help Display a help message and exit successfully. -V, --version Display the version number of xzdec and liblzma. EXIT STATUS 0 All was good. 1 An error occurred. xzdec doesn't have any warning messages like xz(1) has, thus the exit status 2 is not used by xzdec. NOTES Use xz(1) instead of xzdec or lzmadec for normal everyday use. xzdec or lzmadec are meant only for situations where it is important to have a smaller decompressor than the full-featured xz(1). xzdec and lzmadec are not really that small. The size can be reduced further by dropping features from liblzma at compile time, but that shouldn't usually be done for executables distributed in typical non- embedded operating system distributions. If you need a truly small .xz decompressor, consider using XZ Embedded. SEE ALSO xz(1) XZ Embedded: <https://tukaani.org/xz/embedded.html> Tukaani 2024-04-08 XZDEC(1)
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luajit-2.1.0-beta3
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pod2usage
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pod2usage will read the given input file looking for pod documentation and will print the corresponding usage message. If no input file is specified then standard input is read. pod2usage invokes the pod2usage() function in the Pod::Usage module. Please see "pod2usage()" in Pod::Usage. SEE ALSO Pod::Usage, pod2text, Pod::Text, Pod::Text::Termcap, perldoc AUTHOR Please report bugs using <http://rt.cpan.org>. Brad Appleton <bradapp@enteract.com> Based on code for pod2text(1) written by Tom Christiansen <tchrist@mox.perl.com> perl v5.38.2 2023-11-28 POD2USAGE(1)
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pod2usage - print usage messages from embedded pod docs in files
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pod2usage [-help] [-man] [-exit exitval] [-output outfile] [-verbose level] [-pathlist dirlist] [-formatter module] [-utf8] file OPTIONS AND ARGUMENTS -help Print a brief help message and exit. -man Print this command's manual page and exit. -exit exitval The exit status value to return. -output outfile The output file to print to. If the special names "-" or ">&1" or ">&STDOUT" are used then standard output is used. If ">&2" or ">&STDERR" is used then standard error is used. -verbose level The desired level of verbosity to use: 1 : print SYNOPSIS only 2 : print SYNOPSIS sections and any OPTIONS/ARGUMENTS sections 3 : print the entire manpage (similar to running pod2text) -pathlist dirlist Specifies one or more directories to search for the input file if it was not supplied with an absolute path. Each directory path in the given list should be separated by a ':' on Unix (';' on MSWin32 and DOS). -formatter module Which text formatter to use. Default is Pod::Text, or for very old Perl versions Pod::PlainText. An alternative would be e.g. Pod::Text::Termcap. -utf8 This option assumes that the formatter (see above) understands the option "utf8". It turns on generation of utf8 output. file The pathname of a file containing pod documentation to be output in usage message format. If omitted, standard input is read - but the output is then formatted with Pod::Text only - unless a specific formatter has been specified with -formatter.
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tiffsplit
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tiffsplit takes a multi-directory (page) TIFF file and creates one or more single-directory (page) TIFF files from it. The output files are given names created by concatenating a prefix, a lexically ordered suffix in the range [aaa--zzz], the suffix .tif (e.g. xaaa.tif, xaab.tif, …, xzzz.tif). If a prefix is not specified on the command line, the default prefix of x is used.
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tiffsplit - split a multi-image TIFF into single-image TIFF files
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tiffsplit src.tif [ prefix ]
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None. EXIT STATUS tiffsplit exits with one of the following values: 0: Success 1: An error occurred either reading the input or writing results. BUGS Only a select set of "known tags" are copied when splitting. SEE ALSO tiffcp (1), tiffinfo (1), libtiff (3tiff), AUTHOR LibTIFF contributors COPYRIGHT 1988-2022, LibTIFF contributors 4.6 September 8, 2023 TIFFSPLIT(1)
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dltest
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dltest is a simple program that determines whether a symbol appears in a (shared object) library. The name of the library must be prefixed by a full system path. If no parameters are provided, dltest prints a short help message.
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dltest - A simple library symbol test program
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dltest [ library symbol ]
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To determine if the symbol printf is found in libc-2.18.so, run: $ dltest /usr/lib/libc-2.18.so printf AUTHORS The authors of unixODBC are Peter Harvey <pharvey@codebydesign.com> and Nick Gorham <nick@lurcher.org>. For a full list of contributors, refer to the AUTHORS file. COPYRIGHT unixODBC is licensed under the GNU Lesser General Public License. For details about the license, see the COPYING file. version 2.3.12 Thu 07 Jan 2021 dltest(1)
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corelist
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See Module::CoreList for one.
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corelist - a commandline frontend to Module::CoreList
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corelist -v corelist [-a|-d] <ModuleName> | /<ModuleRegex>/ [<ModuleVersion>] ... corelist [-v <PerlVersion>] [ <ModuleName> | /<ModuleRegex>/ ] ... corelist [-r <PerlVersion>] ... corelist --utils [-d] <UtilityName> [<UtilityName>] ... corelist --utils -v <PerlVersion> corelist --feature <FeatureName> [<FeatureName>] ... corelist --diff PerlVersion PerlVersion corelist --upstream <ModuleName>
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-a lists all versions of the given module (or the matching modules, in case you used a module regexp) in the perls Module::CoreList knows about. corelist -a Unicode Unicode was first released with perl v5.6.2 v5.6.2 3.0.1 v5.8.0 3.2.0 v5.8.1 4.0.0 v5.8.2 4.0.0 v5.8.3 4.0.0 v5.8.4 4.0.1 v5.8.5 4.0.1 v5.8.6 4.0.1 v5.8.7 4.1.0 v5.8.8 4.1.0 v5.8.9 5.1.0 v5.9.0 4.0.0 v5.9.1 4.0.0 v5.9.2 4.0.1 v5.9.3 4.1.0 v5.9.4 4.1.0 v5.9.5 5.0.0 v5.10.0 5.0.0 v5.10.1 5.1.0 v5.11.0 5.1.0 v5.11.1 5.1.0 v5.11.2 5.1.0 v5.11.3 5.2.0 v5.11.4 5.2.0 v5.11.5 5.2.0 v5.12.0 5.2.0 v5.12.1 5.2.0 v5.12.2 5.2.0 v5.12.3 5.2.0 v5.12.4 5.2.0 v5.13.0 5.2.0 v5.13.1 5.2.0 v5.13.2 5.2.0 v5.13.3 5.2.0 v5.13.4 5.2.0 v5.13.5 5.2.0 v5.13.6 5.2.0 v5.13.7 6.0.0 v5.13.8 6.0.0 v5.13.9 6.0.0 v5.13.10 6.0.0 v5.13.11 6.0.0 v5.14.0 6.0.0 v5.14.1 6.0.0 v5.15.0 6.0.0 -d finds the first perl version where a module has been released by date, and not by version number (as is the default). --diff Given two versions of perl, this prints a human-readable table of all module changes between the two. The output format may change in the future, and is meant for humans, not programs. For programs, use the Module::CoreList API. -? or -help help! help! help! to see more help, try --man. -man all of the help -v lists all of the perl release versions we got the CoreList for. If you pass a version argument (value of $], like 5.00503 or 5.008008), you get a list of all the modules and their respective versions. (If you have the "version" module, you can also use new- style version numbers, like 5.8.8.) In module filtering context, it can be used as Perl version filter. -r lists all of the perl releases and when they were released If you pass a perl version you get the release date for that version only. --utils lists the first version of perl each named utility program was released with May be used with -d to modify the first release criteria. If used with -v <version> then all utilities released with that version of perl are listed, and any utility programs named on the command line are ignored. --feature, -f lists the first version bundle of each named feature given --upstream, -u Shows if the given module is primarily maintained in perl core or on CPAN and bug tracker URL. As a special case, if you specify the module name "Unicode", you'll get the version number of the Unicode Character Database bundled with the requested perl versions.
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$ corelist File::Spec File::Spec was first released with perl 5.005 $ corelist File::Spec 0.83 File::Spec 0.83 was released with perl 5.007003 $ corelist File::Spec 0.89 File::Spec 0.89 was not in CORE (or so I think) $ corelist File::Spec::Aliens File::Spec::Aliens was not in CORE (or so I think) $ corelist /IPC::Open/ IPC::Open2 was first released with perl 5 IPC::Open3 was first released with perl 5 $ corelist /MANIFEST/i ExtUtils::Manifest was first released with perl 5.001 $ corelist /Template/ /Template/ has no match in CORE (or so I think) $ corelist -v 5.8.8 B B 1.09_01 $ corelist -v 5.8.8 /^B::/ B::Asmdata 1.01 B::Assembler 0.07 B::Bblock 1.02_01 B::Bytecode 1.01_01 B::C 1.04_01 B::CC 1.00_01 B::Concise 0.66 B::Debug 1.02_01 B::Deparse 0.71 B::Disassembler 1.05 B::Lint 1.03 B::O 1.00 B::Showlex 1.02 B::Stackobj 1.00 B::Stash 1.00 B::Terse 1.03_01 B::Xref 1.01 COPYRIGHT Copyright (c) 2002-2007 by D.H. aka PodMaster Currently maintained by the perl 5 porters <perl5-porters@perl.org>. This program is distributed under the same terms as perl itself. See http://perl.org/ or http://cpan.org/ for more info on that. perl v5.38.2 2023-11-28 CORELIST(1)
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wheel3
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runcon
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Run COMMAND with completely-specified CONTEXT, or with current or transitioned security context modified by one or more of LEVEL, ROLE, TYPE, and USER. If none of -c, -t, -u, -r, or -l, is specified, the first argument is used as the complete context. Any additional arguments after COMMAND are interpreted as arguments to the command. Note that only carefully-chosen contexts are likely to successfully run. Run a program in a different SELinux security context. With neither CONTEXT nor COMMAND, print the current security context. Mandatory arguments to long options are mandatory for short options too. CONTEXT Complete security context -c, --compute compute process transition context before modifying -t, --type=TYPE type (for same role as parent) -u, --user=USER user identity -r, --role=ROLE role -l, --range=RANGE levelrange --help display this help and exit --version output version information and exit Exit status: 125 if the runcon command itself fails 126 if COMMAND is found but cannot be invoked 127 if COMMAND cannot be found - the exit status of COMMAND otherwise AUTHOR Written by Russell Coker. REPORTING BUGS GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO Full documentation <https://www.gnu.org/software/coreutils/runcon> or available locally via: info '(coreutils) runcon invocation' GNU coreutils 9.3 April 2023 RUNCON(1)
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runcon - run command with specified security context
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runcon CONTEXT COMMAND [args] runcon [ -c ] [-u USER] [-r ROLE] [-t TYPE] [-l RANGE] COMMAND [args]
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mysql_config_editor
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The mysql_config_editor utility enables you to store authentication credentials in an obfuscated login path file named .mylogin.cnf. The file location is the %APPDATA%\MySQL directory on Windows and the current user's home directory on non-Windows systems. The file can be read later by MySQL client programs to obtain authentication credentials for connecting to MySQL Server. The unobfuscated format of the .mylogin.cnf login path file consists of option groups, similar to other option files. Each option group in .mylogin.cnf is called a “login path,” which is a group that permits only certain options: host, user, password, port and socket. Think of a login path option group as a set of options that specify which MySQL server to connect to and which account to authenticate as. Here is an unobfuscated example: [client] user = mydefaultname password = mydefaultpass host = 127.0.0.1 [mypath] user = myothername password = myotherpass host = localhost When you invoke a client program to connect to the server, the client uses .mylogin.cnf in conjunction with other option files. Its precedence is higher than other option files, but less than options specified explicitly on the client command line. For information about the order in which option files are used, see Section 4.2.2.2, “Using Option Files”. To specify an alternate login path file name, set the MYSQL_TEST_LOGIN_FILE environment variable. This variable is recognized by mysql_config_editor, by standard MySQL clients (mysql, mysqladmin, and so forth), and by the mysql-test-run.pl testing utility. Programs use groups in the login path file as follows: • mysql_config_editor operates on the client login path by default if you specify no --login-path=name option to indicate explicitly which login path to use. • Without a --login-path option, client programs read the same option groups from the login path file that they read from other option files. Consider this command: mysql By default, the mysql client reads the [client] and [mysql] groups from other option files, so it reads them from the login path file as well. • With a --login-path option, client programs additionally read the named login path from the login path file. The option groups read from other option files remain the same. Consider this command: mysql --login-path=mypath The mysql client reads [client] and [mysql] from other option files, and [client], [mysql], and [mypath] from the login path file. • Client programs read the login path file even when the --no-defaults option is used, unless --no-login-paths is set. This permits passwords to be specified in a safer way than on the command line even if --no-defaults is present. mysql_config_editor obfuscates the .mylogin.cnf file so it cannot be read as cleartext, and its contents when unobfuscated by client programs are used only in memory. In this way, passwords can be stored in a file in non-cleartext format and used later without ever needing to be exposed on the command line or in an environment variable. mysql_config_editor provides a print command for displaying the login path file contents, but even in this case, password values are masked so as never to appear in a way that other users can see them. The obfuscation used by mysql_config_editor prevents passwords from appearing in .mylogin.cnf as cleartext and provides a measure of security by preventing inadvertent password exposure. For example, if you display a regular unobfuscated my.cnf option file on the screen, any passwords it contains are visible for anyone to see. With .mylogin.cnf, that is not true, but the obfuscation used is not likely to deter a determined attacker and you should not consider it unbreakable. A user who can gain system administration privileges on your machine to access your files could unobfuscate the .mylogin.cnf file with some effort. The login path file must be readable and writable to the current user, and inaccessible to other users. Otherwise, mysql_config_editor ignores it, and client programs do not use it, either. Invoke mysql_config_editor like this: mysql_config_editor [program_options] command [command_options] If the login path file does not exist, mysql_config_editor creates it. Command arguments are given as follows: • program_options consists of general mysql_config_editor options. • command indicates what action to perform on the .mylogin.cnf login path file. For example, set writes a login path to the file, remove removes a login path, and print displays login path contents. • command_options indicates any additional options specific to the command, such as the login path name and the values to use in the login path. The position of the command name within the set of program arguments is significant. For example, these command lines have the same arguments, but produce different results: mysql_config_editor --help set mysql_config_editor set --help The first command line displays a general mysql_config_editor help message, and ignores the set command. The second command line displays a help message specific to the set command. Suppose that you want to establish a client login path that defines your default connection parameters, and an additional login path named remote for connecting to the MySQL server the host remote.example.com. You want to log in as follows: • By default, to the local server with a user name and password of localuser and localpass • To the remote server with a user name and password of remoteuser and remotepass To set up the login paths in the .mylogin.cnf file, use the following set commands. Enter each command on a single line, and enter the appropriate passwords when prompted: $> mysql_config_editor set --login-path=client --host=localhost --user=localuser --password Enter password: enter password "localpass" here $> mysql_config_editor set --login-path=remote --host=remote.example.com --user=remoteuser --password Enter password: enter password "remotepass" here mysql_config_editor uses the client login path by default, so the --login-path=client option can be omitted from the first command without changing its effect. To see what mysql_config_editor writes to the .mylogin.cnf file, use the print command: $> mysql_config_editor print --all [client] user = localuser password = ***** host = localhost [remote] user = remoteuser password = ***** host = remote.example.com The print command displays each login path as a set of lines beginning with a group header indicating the login path name in square brackets, followed by the option values for the login path. Password values are masked and do not appear as cleartext. If you do not specify --all to display all login paths or --login-path=name to display a named login path, the print command displays the client login path by default, if there is one. As shown by the preceding example, the login path file can contain multiple login paths. In this way, mysql_config_editor makes it easy to set up multiple “personalities” for connecting to different MySQL servers, or for connecting to a given server using different accounts. Any of these can be selected by name later using the --login-path option when you invoke a client program. For example, to connect to the remote server, use this command: mysql --login-path=remote Here, mysql reads the [client] and [mysql] option groups from other option files, and the [client], [mysql], and [remote] groups from the login path file. To connect to the local server, use this command: mysql --login-path=client Because mysql reads the client and mysql login paths by default, the --login-path option does not add anything in this case. That command is equivalent to this one: mysql Options read from the login path file take precedence over options read from other option files. Options read from login path groups appearing later in the login path file take precedence over options read from groups appearing earlier in the file. mysql_config_editor adds login paths to the login path file in the order you create them, so you should create more general login paths first and more specific paths later. If you need to move a login path within the file, you can remove it, then recreate it to add it to the end. For example, a client login path is more general because it is read by all client programs, whereas a mysqldump login path is read only by mysqldump. Options specified later override options specified earlier, so putting the login paths in the order client, mysqldump enables mysqldump-specific options to override client options. When you use the set command with mysql_config_editor to create a login path, you need not specify all possible option values (host name, user name, password, port, socket). Only those values given are written to the path. Any missing values required later can be specified when you invoke a client path to connect to the MySQL server, either in other option files or on the command line. Any options specified on the command line override those specified in the login path file or other option files. For example, if the credentials in the remote login path also apply for the host remote2.example.com, connect to the server on that host like this: mysql --login-path=remote --host=remote2.example.com mysql_config_editor General Options mysql_config_editor supports the following general options, which may be used preceding any command named on the command line. For descriptions of command-specific options, see mysql_config_editor Commands and Command-Specific Options. • --help, -? ┌────────────────────┬────────┐ │Command-Line Format │ --help │ └────────────────────┴────────┘ Display a general help message and exit. To see a command-specific help message, invoke mysql_config_editor as follows, where command is a command other than help: mysql_config_editor command --help • --debug[=debug_options], -# debug_options ┌────────────────────┬─────────────────────────┐ │Command-Line Format │ --debug[=debug_options] │ ├────────────────────┼─────────────────────────┤ │Type │ String │ ├────────────────────┼─────────────────────────┤ │Default Value │ d:t:o │ └────────────────────┴─────────────────────────┘ Write a debugging log. A typical debug_options string is d:t:o,file_name. The default is d:t:o,/tmp/mysql_config_editor.trace. This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option. • --verbose, -v ┌────────────────────┬───────────┐ │Command-Line Format │ --verbose │ └────────────────────┴───────────┘ Verbose mode. Print more information about what the program does. This option may be helpful in diagnosing problems if an operation does not have the effect you expect. • --version, -V ┌────────────────────┬───────────┐ │Command-Line Format │ --version │ └────────────────────┴───────────┘ Display version information and exit. mysql_config_editor Commands and Command-Specific Options This section describes the permitted mysql_config_editor commands, and, for each one, the command-specific options permitted following the command name on the command line. In addition, mysql_config_editor supports general options that can be used preceding any command. For descriptions of these options, see mysql_config_editor General Options. mysql_config_editor supports these commands: • help Display a general help message and exit. This command takes no following options. To see a command-specific help message, invoke mysql_config_editor as follows, where command is a command other than help: mysql_config_editor command --help • print [options] Print the contents of the login path file in unobfuscated form, with the exception that passwords are displayed as *****. The default login path name is client if no login path is named. If both --all and --login-path are given, --all takes precedence. The print command permits these options following the command name: • --help, -? Display a help message for the print command and exit. To see a general help message, use mysql_config_editor --help. • --all Print the contents of all login paths in the login path file. • --login-path=name, -G name Print the contents of the named login path. • remove [options] Remove a login path from the login path file, or modify a login path by removing options from it. This command removes from the login path only such options as are specified with the --host, --password, --port, --socket, and --user options. If none of those options are given, remove removes the entire login path. For example, this command removes only the user option from the mypath login path rather than the entire mypath login path: mysql_config_editor remove --login-path=mypath --user This command removes the entire mypath login path: mysql_config_editor remove --login-path=mypath The remove command permits these options following the command name: • --help, -? Display a help message for the remove command and exit. To see a general help message, use mysql_config_editor --help. • --host, -h Remove the host name from the login path. • --login-path=name, -G name The login path to remove or modify. The default login path name is client if this option is not given. • --password, -p Remove the password from the login path. • --port, -P Remove the TCP/IP port number from the login path. • --socket, -S Remove the Unix socket file name from the login path. • --user, -u Remove the user name from the login path. • --warn, -w Warn and prompt the user for confirmation if the command attempts to remove the default login path (client) and --login-path=client was not specified. This option is enabled by default; use --skip-warn to disable it. • reset [options] Empty the contents of the login path file. The reset command permits these options following the command name: • --help, -? Display a help message for the reset command and exit. To see a general help message, use mysql_config_editor --help. • set [options] Write a login path to the login path file. This command writes to the login path only such options as are specified with the --host, --password, --port, --socket, and --user options. If none of those options are given, mysql_config_editor writes the login path as an empty group. The set command permits these options following the command name: • --help, -? Display a help message for the set command and exit. To see a general help message, use mysql_config_editor --help. • --host=host_name, -h host_name The host name to write to the login path. • --login-path=name, -G name The login path to create. The default login path name is client if this option is not given. • --password, -p Prompt for a password to write to the login path. After mysql_config_editor displays the prompt, type the password and press Enter. To prevent other users from seeing the password, mysql_config_editor does not echo it. To specify an empty password, press Enter at the password prompt. The resulting login path written to the login path file includes a line like this: password = • --port=port_num, -P port_num The TCP/IP port number to write to the login path. • --socket=file_name, -S file_name The Unix socket file name to write to the login path. • --user=user_name, -u user_name The user name to write to the login path. • --warn, -w Warn and prompt the user for confirmation if the command attempts to overwrite an existing login path. This option is enabled by default; use --skip-warn to disable it. COPYRIGHT Copyright © 1997, 2023, Oracle and/or its affiliates. This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with the program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/. SEE ALSO For more information, please refer to the MySQL Reference Manual, which may already be installed locally and which is also available online at http://dev.mysql.com/doc/. AUTHOR Oracle Corporation (http://dev.mysql.com/). MySQL 8.3 11/23/2023 MYSQL_CONFIG_EDITOR(1)
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mysql_config_editor - configure authentication information for connecting to MySQL server
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mysql_config_editor options command
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parsort
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parsort uses GNU sort to sort in parallel. It works just like sort but faster on inputs with more than 1 M lines, if you have a multicore machine. Hopefully these ideas will make it into GNU sort in the future.
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parsort - Sort (big files) in parallel
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parsort options for sort
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Same as sort. Except: --parallel=N Change the number of sorts run concurrently to N. N will be increased to number of files if parsort is given more than N files. EXAMPLE Sort files: parsort *.txt > sorted.txt Sort stdin (standard input) numerically: cat numbers | parsort -n > sorted.txt PERFORMANCE parsort is faster on files than on stdin (standard input), because different parts of a file can be read in parallel. On a 48 core machine you should see a speedup of 3x over sort. AUTHOR Copyright (C) 2020-2024 Ole Tange, http://ole.tange.dk and Free Software Foundation, Inc. LICENSE Copyright (C) 2012 Free Software Foundation, Inc. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or at your option any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. DEPENDENCIES parsort uses sort, bash, and parallel. SEE ALSO sort 20240722 2024-07-21 PARSORT(1)
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parallel
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STOP! Read the Reader's guide below if you are new to GNU parallel. GNU parallel is a shell tool for executing jobs in parallel using one or more computers. A job can be a single command or a small script that has to be run for each of the lines in the input. The typical input is a list of files, a list of hosts, a list of users, a list of URLs, or a list of tables. A job can also be a command that reads from a pipe. GNU parallel can then split the input into blocks and pipe a block into each command in parallel. If you use xargs and tee today you will find GNU parallel very easy to use as GNU parallel is written to have the same options as xargs. If you write loops in shell, you will find GNU parallel may be able to replace most of the loops and make them run faster by running several jobs in parallel. GNU parallel makes sure output from the commands is the same output as you would get had you run the commands sequentially. This makes it possible to use output from GNU parallel as input for other programs. For each line of input GNU parallel will execute command with the line as arguments. If no command is given, the line of input is executed. Several lines will be run in parallel. GNU parallel can often be used as a substitute for xargs or cat | bash. Reader's guide GNU parallel includes the 4 types of documentation: Tutorial, how-to, reference and explanation/design. Tutorial If you prefer reading a book buy GNU Parallel 2018 at https://www.lulu.com/shop/ole-tange/gnu-parallel-2018/paperback/product-23558902.html or download it at: https://doi.org/10.5281/zenodo.1146014 Read at least chapter 1+2. It should take you less than 20 minutes. Otherwise start by watching the intro videos for a quick introduction: https://youtube.com/playlist?list=PL284C9FF2488BC6D1 If you want to dive deeper: spend a couple of hours walking through the tutorial (man parallel_tutorial). Your command line will love you for it. How-to You can find a lot of examples of use in man parallel_examples. They will give you an idea of what GNU parallel is capable of, and you may find a solution you can simply adapt to your situation. If the example do not cover your exact needs, the options map (https://www.gnu.org/software/parallel/parallel_options_map.pdf) can help you identify options that are related, so you can look these up in the man page. Reference If you need a one page printable cheat sheet you can find it on: https://www.gnu.org/software/parallel/parallel_cheat.pdf The man page is the reference for all options, and reading the man page from cover to cover is probably not what you need. Design discussion If you want to know the design decisions behind GNU parallel, try: man parallel_design. This is also a good intro if you intend to change GNU parallel.
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parallel - build and execute shell command lines from standard input in parallel
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parallel [options] [command [arguments]] < list_of_arguments parallel [options] [command [arguments]] ( ::: arguments | :::+ arguments | :::: argfile(s) | ::::+ argfile(s) ) ... parallel --semaphore [options] command #!/usr/bin/parallel --shebang [options] [command [arguments]] #!/usr/bin/parallel --shebang-wrap [options] [command [arguments]]
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command Command to execute. If command or the following arguments contain replacement strings (such as {}) every instance will be substituted with the input. If command is given, GNU parallel solve the same tasks as xargs. If command is not given GNU parallel will behave similar to cat | sh. The command must be an executable, a script, a composed command, an alias, or a function. Bash functions: export -f the function first or use env_parallel. Bash, Csh, or Tcsh aliases: Use env_parallel. Zsh, Fish, Ksh, and Pdksh functions and aliases: Use env_parallel. {} Input line. This replacement string will be replaced by a full line read from the input source. The input source is normally stdin (standard input), but can also be given with --arg-file, :::, or ::::. The replacement string {} can be changed with -I. If the command line contains no replacement strings then {} will be appended to the command line. Replacement strings are normally quoted, so special characters are not parsed by the shell. The exception is if the command starts with a replacement string; then the string is not quoted. See also: --plus {.} {/} {//} {/.} {#} {%} {n} {=perl expression=} {.} Input line without extension. This replacement string will be replaced by the input with the extension removed. If the input line contains . after the last /, the last . until the end of the string will be removed and {.} will be replaced with the remaining. E.g. foo.jpg becomes foo, subdir/foo.jpg becomes subdir/foo, sub.dir/foo.jpg becomes sub.dir/foo, sub.dir/bar remains sub.dir/bar. If the input line does not contain . it will remain unchanged. The replacement string {.} can be changed with --extensionreplace See also: {} --extensionreplace {/} Basename of input line. This replacement string will be replaced by the input with the directory part removed. See also: {} --basenamereplace {//} Dirname of input line. This replacement string will be replaced by the dir of the input line. See dirname(1). See also: {} --dirnamereplace {/.} Basename of input line without extension. This replacement string will be replaced by the input with the directory and extension part removed. {/.} is a combination of {/} and {.}. See also: {} --basenameextensionreplace {#} Sequence number of the job to run. This replacement string will be replaced by the sequence number of the job being run. It contains the same number as $PARALLEL_SEQ. See also: {} --seqreplace {%} Job slot number. This replacement string will be replaced by the job's slot number between 1 and number of jobs to run in parallel. There will never be 2 jobs running at the same time with the same job slot number. If the job needs to be retried (e.g using --retries or --retry-failed) the job slot is not automatically updated. You should then instead use $PARALLEL_JOBSLOT: $ do_test() { id="$3 {%}=$1 PARALLEL_JOBSLOT=$2" echo run "$id"; sleep 1 # fail if {%} is odd return `echo $1%2 | bc` } $ export -f do_test $ parallel -j3 --jl mylog do_test {%} \$PARALLEL_JOBSLOT {} ::: A B C D run A {%}=1 PARALLEL_JOBSLOT=1 run B {%}=2 PARALLEL_JOBSLOT=2 run C {%}=3 PARALLEL_JOBSLOT=3 run D {%}=1 PARALLEL_JOBSLOT=1 $ parallel --retry-failed -j3 --jl mylog do_test {%} \$PARALLEL_JOBSLOT {} ::: A B C D run A {%}=1 PARALLEL_JOBSLOT=1 run C {%}=3 PARALLEL_JOBSLOT=2 run D {%}=1 PARALLEL_JOBSLOT=3 Notice how {%} and $PARALLEL_JOBSLOT differ in the retry run of C and D. See also: {} --jobs --slotreplace {n} Argument from input source n or the n'th argument. This positional replacement string will be replaced by the input from input source n (when used with --arg-file or ::::) or with the n'th argument (when used with -N or --colsep). If n is negative it refers to the n'th last argument. See also: {} {n.} {n/} {n//} {n/.} --colsep {n.} Argument from input source n or the n'th argument without extension. {n.} is a combination of {n} and {.}. This positional replacement string will be replaced by the input from input source n (when used with --arg-file or ::::) or with the n'th argument (when used with -N). The input will have the extension removed. See also: {n} {.} {n/} Basename of argument from input source n or the n'th argument. {n/} is a combination of {n} and {/}. This positional replacement string will be replaced by the input from input source n (when used with --arg-file or ::::) or with the n'th argument (when used with -N). The input will have the directory (if any) removed. See also: {n} {/} {n//} Dirname of argument from input source n or the n'th argument. {n//} is a combination of {n} and {//}. This positional replacement string will be replaced by the dir of the input from input source n (when used with --arg-file or ::::) or with the n'th argument (when used with -N). See dirname(1). See also: {n} {//} {n/.} Basename of argument from input source n or the n'th argument without extension. {n/.} is a combination of {n}, {/}, and {.}. This positional replacement string will be replaced by the input from input source n (when used with --arg-file or ::::) or with the n'th argument (when used with -N). The input will have the directory (if any) and extension removed. See also: {n} {/.} {=perl expression=} Replace with calculated perl expression. $_ will contain the same as {}. After evaluating perl expression $_ will be used as the value. It is recommended to only change $_ but you have full access to all of GNU parallel's internal functions and data structures. The expression must give the same result if evaluated twice - otherwise the behaviour is undefined. E.g. in some versions of GNU parallel this will not work as expected: parallel echo '{= $_= ++$wrong_counter =}' ::: a b c A few convenience functions and data structures have been made: Q(string) Shell quote a string. Example: parallel echo {} is quoted as '{= $_=Q($_) =}' ::: \$PWD pQ(string) Perl quote a string. Example: parallel echo {} is quoted as '{= $_=pQ($_) =}' ::: \$PWD uq() (or uq) Do not quote current replacement string. Example: parallel echo {} has the value '{= uq =}' ::: \$PWD hash(val) Compute B::hash(val). Example: parallel echo Hash of {} is '{= $_=hash($_) =}' ::: a b c total_jobs() Number of jobs in total. Example: parallel echo Number of jobs: '{= $_=total_jobs() =}' ::: a b c slot() Slot number of job. Example: parallel echo Job slot of {} is '{= $_=slot() =}' ::: a b c seq() Sequence number of job. Example: parallel echo Seq number of {} is '{= $_=seq() =}' ::: a b c @arg The arguments counting from 1 ($arg[1] = {1} = first argument). Example: parallel echo {1}+{2}='{=1 $_=$arg[1]+$arg[2] =}' \ ::: 1 2 3 ::: 2 3 4 ('{=1' forces this to be a positional replacement string, and therefore will not repeat the value for each arg.) skip() Skip this job (see also --filter). Example: parallel echo '{= $arg[1] >= $arg[2] and skip =}' \ ::: 1 2 3 ::: 2 3 4 yyyy_mm_dd_hh_mm_ss(sec) yyyy_mm_dd_hh_mm(sec) yyyy_mm_dd(sec) hh_mm_ss(sec) hh_mm(sec) yyyymmddhhmmss(sec) yyyymmddhhmm(sec) yyyymmdd(sec) hhmmss(sec) hhmm(sec) Time functions. sec is number of seconds since epoch. If left out it will use current local time. Example: parallel echo 'Now: {= $_=yyyy_mm_dd_hh_mm_ss() =}' ::: Dummy parallel echo 'The end: {= $_=yyyy_mm_dd_hh_mm_ss($_) =}' \ ::: 2147483648 Example: seq 10 | parallel echo {} + 1 is {= '$_++' =} parallel csh -c {= '$_="mkdir ".Q($_)' =} ::: '12" dir' seq 50 | parallel echo job {#} of {= '$_=total_jobs()' =} See also: --rpl --parens {} {=n perl expression=} --filter {=n perl expression=} Positional equivalent to {=perl expression=}. To understand positional replacement strings see {n}. See also: {=perl expression=} {n} ::: arguments Use arguments on the command line as input source. Unlike other options for GNU parallel ::: is placed after the command and before the arguments. The following are equivalent: (echo file1; echo file2) | parallel gzip parallel gzip ::: file1 file2 parallel gzip {} ::: file1 file2 parallel --arg-sep ,, gzip {} ,, file1 file2 parallel --arg-sep ,, gzip ,, file1 file2 parallel ::: "gzip file1" "gzip file2" To avoid treating ::: as special use --arg-sep to set the argument separator to something else. If multiple ::: are given, each group will be treated as an input source, and all combinations of input sources will be generated. E.g. ::: 1 2 ::: a b c will result in the combinations (1,a) (1,b) (1,c) (2,a) (2,b) (2,c). This is useful for replacing nested for- loops. :::, ::::, and --arg-file can be mixed. So these are equivalent: parallel echo {1} {2} {3} ::: 6 7 ::: 4 5 ::: 1 2 3 parallel echo {1} {2} {3} :::: <(seq 6 7) <(seq 4 5) \ :::: <(seq 1 3) parallel -a <(seq 6 7) echo {1} {2} {3} :::: <(seq 4 5) \ :::: <(seq 1 3) parallel -a <(seq 6 7) -a <(seq 4 5) echo {1} {2} {3} \ ::: 1 2 3 seq 6 7 | parallel -a - -a <(seq 4 5) echo {1} {2} {3} \ ::: 1 2 3 seq 4 5 | parallel echo {1} {2} {3} :::: <(seq 6 7) - \ ::: 1 2 3 See also: --arg-sep --arg-file :::: :::+ ::::+ --link :::+ arguments Like ::: but linked like --link to the previous input source. Contrary to --link, values do not wrap: The shortest input source determines the length. Example: parallel echo ::: a b c :::+ 1 2 3 ::: X Y :::+ 11 22 See also: ::::+ --link :::: argfiles Another way to write --arg-file argfile1 --arg-file argfile2 ... ::: and :::: can be mixed. See also: --arg-file ::: ::::+ --link ::::+ argfiles Like :::: but linked like --link to the previous input source. Contrary to --link, values do not wrap: The shortest input source determines the length. See also: --arg-file :::+ --link --null -0 Use NUL as delimiter. Normally input lines will end in \n (newline). If they end in \0 (NUL), then use this option. It is useful for processing arguments that may contain \n (newline). Shorthand for --delimiter '\0'. See also: --delimiter --arg-file input-file -a input-file Use input-file as input source. If multiple --arg-file are given, each input-file will be treated as an input source, and all combinations of input sources will be generated. E.g. The file foo contains 1 2, the file bar contains a b c. -a foo -a bar will result in the combinations (1,a) (1,b) (1,c) (2,a) (2,b) (2,c). This is useful for replacing nested for- loops. If input-file starts with + the file will be linked to the previous --arg-file E.g. The file foo contains 1 2, the file bar contains a b. -a foo -a +bar will result in the combinations (1,a) (2,b) like --link instead of generating all combinations. See also: --link {n} :::: ::::+ ::: --arg-file-sep sep-str Use sep-str instead of :::: as separator string between command and argument files. Useful if :::: is used for something else by the command. See also: :::: --arg-sep sep-str Use sep-str instead of ::: as separator string. Useful if ::: is used for something else by the command. Also useful if you command uses ::: but you still want to read arguments from stdin (standard input): Simply change --arg-sep to a string that is not in the command line. See also: ::: --bar Show progress as a progress bar. In the bar is shown: % of jobs completed, estimated seconds left, and number of jobs started. It is compatible with zenity: seq 1000 | parallel -j30 --bar '(echo {};sleep 0.1)' \ 2> >(perl -pe 'BEGIN{$/="\r";$|=1};s/\r/\n/g' | zenity --progress --auto-kill) | wc See also: --eta --progress --total-jobs --basefile file --bf file file will be transferred to each sshlogin before first job is started. It will be removed if --cleanup is active. The file may be a script to run or some common base data needed for the job. Multiple --bf can be specified to transfer more basefiles. The file will be transferred the same way as --transferfile. See also: --sshlogin --transfer --return --cleanup --workdir --basenamereplace replace-str --bnr replace-str Use the replacement string replace-str instead of {/} for basename of input line. See also: {/} --basenameextensionreplace replace-str --bner replace-str Use the replacement string replace-str instead of {/.} for basename of input line without extension. See also: {/.} --bin binexpr Use binexpr as binning key and bin input to the jobs. binexpr is [column number|column name] [perlexpression] e.g.: 3 Address 3 $_%=100 Address s/\D//g Each input line is split using --colsep. The value of the column is put into $_, the perl expression is executed, the resulting value is is the job slot that will be given the line. If the value is bigger than the number of jobslots the value will be modulo number of jobslots. This is similar to --shard but the hashing algorithm is a simple modulo, which makes it predictible which jobslot will receive which value. The performance is in the order of 100K rows per second. Faster if the bincol is small (<10), slower if it is big (>100). --bin requires --pipe and a fixed numeric value for --jobs. See also: SPREADING BLOCKS OF DATA --group-by --round-robin --shard --bg Run command in background. GNU parallel will normally wait for the completion of a job. With --bg GNU parallel will not wait for completion of the command before exiting. This is the default if --semaphore is set. Implies --semaphore. See also: --fg man sem --bibtex --citation Print the citation notice and BibTeX entry for GNU parallel, silence citation notice for all future runs, and exit. It will not run any commands. If it is impossible for you to run --citation you can instead use --will-cite, which will run commands, but which will only silence the citation notice for this single run. If you use --will-cite in scripts to be run by others you are making it harder for others to see the citation notice. The development of GNU parallel is indirectly financed through citations, so if your users do not know they should cite then you are making it harder to finance development. However, if you pay 10000 EUR, you have done your part to finance future development and should feel free to use --will-cite in scripts. If you do not want to help financing future development by letting other users see the citation notice or by paying, then please consider using another tool instead of GNU parallel. You can find some of the alternatives in man parallel_alternatives. --block size --block-size size Size of block in bytes to read at a time. The size can be postfixed with K, M, G, T, P, k, m, g, t, or p. GNU parallel tries to meet the block size but can be off by the length of one record. For performance reasons size should be bigger than a two records. GNU parallel will warn you and automatically increase the size if you choose a size that is too small. If you use -N, --block should be bigger than N+1 records. size defaults to 1M. When using --pipe-part a negative block size is not interpreted as a blocksize but as the number of blocks each jobslot should have. So this will run 10*5 = 50 jobs in total: parallel --pipe-part -a myfile --block -10 -j5 wc This is an efficient alternative to --round-robin because data is never read by GNU parallel, but you can still have very few jobslots process large amounts of data. See also: UNIT PREFIX -N --pipe --pipe-part --round-robin --block-timeout --block-timeout duration --bt duration Timeout for reading block when using --pipe. If it takes longer than duration to read a full block, use the partial block read so far. duration is in seconds, but can be postfixed with s, m, h, or d. See also: TIME POSTFIXES --pipe --block --cat Create a temporary file with content. Normally --pipe/--pipe-part will give data to the program on stdin (standard input). With --cat GNU parallel will create a temporary file with the name in {}, so you can do: parallel --pipe --cat wc {}. Implies --pipe unless --pipe-part is used. See also: --pipe --pipe-part --fifo --cleanup Remove transferred files. --cleanup will remove the transferred files on the remote computer after processing is done. find log -name '*gz' | parallel \ --sshlogin server.example.com --transferfile {} \ --return {.}.bz2 --cleanup "zcat {} | bzip -9 >{.}.bz2" With --transferfile {} the file transferred to the remote computer will be removed on the remote computer. Directories on the remote computer containing the file will be removed if they are empty. With --return the file transferred from the remote computer will be removed on the remote computer. Directories on the remote computer containing the file will be removed if they are empty. --cleanup is ignored when not used with --basefile, --transfer, --transferfile or --return. See also: --basefile --transfer --transferfile --sshlogin --return --color Colour output. Colour the output. Each job gets its own colour combination (background+foreground). --color is ignored when using -u. See also: --color-failed --color-failed --cf Colour the output from failing jobs white on red. Useful if you have a lot of jobs and want to focus on the failing jobs. --color-failed is ignored when using -u, --line-buffer and unreliable when using --latest-line. See also: --color --colsep regexp -C regexp Column separator. The input will be treated as a table with regexp separating the columns. The n'th column can be accessed using {n} or {n.}. E.g. {3} is the 3rd column. If there are more input sources, each input source will be separated, but the columns from each input source will be linked. Here {4} refers to column 2 in input source 2: parallel --colsep '-' echo {4} {3} {2} {1} \ ::: A-B C-D ::: e-f g-h --colsep implies --trim rl, which can be overridden with --trim n. regexp is a Perl Regular Expression: https://perldoc.perl.org/perlre.html See also: --csv {n} --trim --link --combineexec name --combine-executable name Combine GNU parallel with another program into a single executable. Let us say you have developed myprg which takes a single argument. You do not want to parallelize it yourself. You could write a wrapper that uses GNU parallel called myparprg: #!/bin/sh parallel myprg ::: "$@" But for others to use this, they need to install: GNU parallel, myprg, and myparprg. It would be easier to install if all could be packed into a single executable. If myprg is written in shell, you can use --embed. If myprg is a binary you can use --combineexec. Here we use gzip as example: parallel --combineexec pargzip gzip -9 ::: You can now do: ./pargzip foo bar baz If you want to pass options to gzip you can do: parallel --combineexec pargzip gzip Followed by: ./pargzip -1 ::: foo bar baz See also: --embed --shebang --shebang-wrap --compress Compress temporary files. If the output is big and very compressible this will take up less disk space in $TMPDIR and possibly be faster due to less disk I/O. GNU parallel will try pzstd, lbzip2, pbzip2, zstd, pigz, lz4, lzop, plzip, lzip, lrz, gzip, pxz, lzma, bzip2, xz, clzip, in that order, and use the first available. GNU parallel will use up to 8 processes per job waiting to be printed. See man parallel_design for details. See also: --compress-program --compress-program prg --decompress-program prg Use prg for (de)compressing temporary files. It is assumed that prg -dc will decompress stdin (standard input) to stdout (standard output) unless --decompress-program is given. See also: --compress --csv Treat input as CSV-format. --colsep sets the field delimiter. It works very much like --colsep except it deals correctly with quoting. Compare: echo '"1 big, 2 small","2""x4"" plank",12.34' | parallel --csv echo {1} of {2} at {3} echo '"1 big, 2 small","2""x4"" plank",12.34' | parallel --colsep ',' echo {1} of {2} at {3} Even quoted newlines are parsed correctly: (echo '"Start of field 1 with newline' echo 'Line 2 in field 1";value 2') | parallel --csv --colsep ';' echo Field 1: {1} Field 2: {2} When used with --pipe only pass full CSV-records. See also: --pipe --link {n} --colsep --header --ctag (obsolete: use --color --tag) Color tag. If the values look very similar looking at the output it can be hard to tell when a new value is used. --ctag gives each value a random color. See also: --color --tag --ctagstring str (obsolete: use --color --tagstring) Color tagstring. See also: --color --ctag --tagstring --delay duration Delay starting next job by duration. GNU parallel will not start another job for the next duration. duration is in seconds, but can be postfixed with s, m, h, or d. If you append 'auto' to duration (e.g. 13m3sauto) GNU parallel will automatically try to find the optimal value: If a job fails, duration is increased by 30%. If a job succeeds, duration is decreased by 10%. See also: TIME POSTFIXES --retries --ssh-delay --delimiter delim -d delim Input items are terminated by delim. The specified delimiter may be characters, C-style character escapes such as \n, or octal or hexadecimal escape codes. Octal and hexadecimal escape codes are understood as for the printf command. See also: --colsep --dirnamereplace replace-str --dnr replace-str Use the replacement string replace-str instead of {//} for dirname of input line. See also: {//} --dry-run Print the job to run on stdout (standard output), but do not run the job. Use -v -v to include the wrapping that GNU parallel generates (for remote jobs, --tmux, --nice, --pipe, --pipe-part, --fifo and --cat). Do not count on this literally, though, as the job may be scheduled on another computer or the local computer if : is in the list. See also: -v -E eof-str Set the end of file string to eof-str. If the end of file string occurs as a line of input, the rest of the input is not read. If neither -E nor -e is used, no end of file string is used. --eof[=eof-str] -e[eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant for xargs while this option is not. If eof-str is omitted, there is no end of file string. If neither -E nor -e is used, no end of file string is used. --embed Embed GNU parallel in a shell script. If you need to distribute your script to someone who does not want to install GNU parallel you can embed GNU parallel in your own shell script: parallel --embed > new_script After which you add your code at the end of new_script. This is tested on ash, bash, dash, ksh, sh, and zsh. --env var Copy exported environment variable var. This will copy var to the environment that the command is run in. This is especially useful for remote execution. In Bash var can also be a Bash function - just remember to export -f the function. The variable '_' is special. It will copy all exported environment variables except for the ones mentioned in ~/.parallel/ignored_vars. To copy the full environment (both exported and not exported variables, arrays, and functions) use env_parallel. See also: --record-env --session --sshlogin command env_parallel --eta Show the estimated number of seconds before finishing. This forces GNU parallel to read all jobs before starting to find the number of jobs (unless you use --total-jobs). GNU parallel normally only reads the next job to run. The estimate is based on the runtime of finished jobs, so the first estimate will only be shown when the first job has finished. Implies --progress. See also: --bar --progress --total-jobs --fg Run command in foreground. With --tmux and --tmuxpane GNU parallel will start tmux in the foreground. With --semaphore GNU parallel will run the command in the foreground (opposite --bg), and wait for completion of the command before exiting. Exit code will be that of the command. See also: --bg man sem --fifo Create a temporary fifo with content. Normally --pipe and --pipe-part will give data to the program on stdin (standard input). With --fifo GNU parallel will create a temporary fifo with the name in {}, so you can do: parallel --pipe --fifo wc {} Beware: If the fifo is never opened for reading, the job will block forever: seq 1000000 | parallel --fifo echo This will block forever seq 1000000 | parallel --fifo 'echo This will not block < {}' By using --fifo instead of --cat you may save I/O as --cat will write to a temporary file, whereas --fifo will not. Implies --pipe unless --pipe-part is used. See also: --cat --pipe --pipe-part --filter filter Only run jobs where filter is true. filter can contain replacement strings and Perl code. Example: parallel --filter '{1}+{2}+{3} < 10' echo {1},{2},{3} \ ::: {1..10} ::: {3..8} ::: {3..10} Outputs: 1,3,3 1,3,4 1,3,5 1,4,3 1,4,4 1,5,3 2,3,3 2,3,4 2,4,3 3,3,3 parallel --filter '{1} < {2}*{2}' echo {1},{2} \ ::: {1..10} ::: {1..3} Outputs: 1,2 1,3 2,2 2,3 3,2 3,3 4,3 5,3 6,3 7,3 8,3 parallel --filter '{choose_k}' --plus echo {1},{2},{3} \ ::: {1..5} ::: {1..5} ::: {1..5} Outputs: 1,2,3 1,2,4 1,2,5 1,3,4 1,3,5 1,4,5 2,3,4 2,3,5 2,4,5 3,4,5 See also: skip() --no-run-if-empty {choose_k} --filter-hosts Remove down hosts. For each remote host: check that login through ssh works. If not: do not use this host. For performance reasons, this check is performed only at the start and every time --sshloginfile is changed. If an host goes down after the first check, it will go undetected until --sshloginfile is changed; --retries can be used to mitigate this. Currently you can not put --filter-hosts in a profile, $PARALLEL, /etc/parallel/config or similar. This is because GNU parallel uses GNU parallel to compute this, so you will get an infinite loop. This will likely be fixed in a later release. See also: --sshloginfile --sshlogin --retries --gnu Behave like GNU parallel. This option historically took precedence over --tollef. The --tollef option is now retired, and therefore may not be used. --gnu is kept for compatibility, but does nothing. --group Group output. Output from each job is grouped together and is only printed when the command is finished. Stdout (standard output) first followed by stderr (standard error). This takes in the order of 0.5ms CPU time per job and depends on the speed of your disk for larger output. --group is the default. See also: --line-buffer --ungroup --tag --group-by val Group input by value. Combined with --pipe/--pipe-part --group-by groups lines with the same value into a record. The value can be computed from the full line or from a single column. val can be: column number Use the value in the column numbered. column name Treat the first line as a header and use the value in the column named. (Not supported with --pipe-part). perl expression Run the perl expression and use $_ as the value. column number perl expression Put the value of the column put in $_, run the perl expression, and use $_ as the value. column name perl expression Put the value of the column put in $_, run the perl expression, and use $_ as the value. (Not supported with --pipe-part). Example: UserID, Consumption 123, 1 123, 2 12-3, 1 221, 3 221, 1 2/21, 5 If you want to group 123, 12-3, 221, and 2/21 into 4 records and pass one record at a time to wc: tail -n +2 table.csv | \ parallel --pipe --colsep , --group-by 1 -kN1 wc Make GNU parallel treat the first line as a header: cat table.csv | \ parallel --pipe --colsep , --header : --group-by 1 -kN1 wc Address column by column name: cat table.csv | \ parallel --pipe --colsep , --header : --group-by UserID -kN1 wc If 12-3 and 123 are really the same UserID, remove non-digits in UserID when grouping: cat table.csv | parallel --pipe --colsep , --header : \ --group-by 'UserID s/\D//g' -kN1 wc See also: SPREADING BLOCKS OF DATA --pipe --pipe-part --bin --shard --round-robin --help -h Print a summary of the options to GNU parallel and exit. --halt-on-error val --halt val When should GNU parallel terminate? In some situations it makes no sense to run all jobs. GNU parallel should simply stop as soon as a condition is met. val defaults to never, which runs all jobs no matter what. val can also take on the form of when,why. when can be 'now' which means kill all running jobs and halt immediately, or it can be 'soon' which means wait for all running jobs to complete, but start no new jobs. why can be 'fail=X', 'fail=Y%', 'success=X', 'success=Y%', 'done=X', or 'done=Y%' where X is the number of jobs that has to fail, succeed, or be done before halting, and Y is the percentage of jobs that has to fail, succeed, or be done before halting. Example: --halt now,fail=1 exit when a job has failed. Kill running jobs. --halt soon,fail=3 exit when 3 jobs have failed, but wait for running jobs to complete. --halt soon,fail=3% exit when 3% of the jobs have failed, but wait for running jobs to complete. --halt now,success=1 exit when a job has succeeded. Kill running jobs. --halt soon,success=3 exit when 3 jobs have succeeded, but wait for running jobs to complete. --halt now,success=3% exit when 3% of the jobs have succeeded. Kill running jobs. --halt now,done=1 exit when a job has finished. Kill running jobs. --halt soon,done=3 exit when 3 jobs have finished, but wait for running jobs to complete. --halt now,done=3% exit when 3% of the jobs have finished. Kill running jobs. For backwards compatibility these also work: 0 never 1 soon,fail=1 2 now,fail=1 -1 soon,success=1 -2 now,success=1 1-99% soon,fail=1-99% --header regexp Use regexp as header. For normal usage the matched header (typically the first line: --header '.*\n') will be split using --colsep (which will default to '\t') and column names can be used as replacement variables: {column name}, {column name/}, {column name//}, {column name/.}, {column name.}, {=column name perl expression =}, .. For --pipe the matched header will be prepended to each output. --header : is an alias for --header '.*\n'. If regexp is a number, it is a fixed number of lines. --header 0 is special: It will make replacement strings for files given with --arg-file or ::::. It will make {foo/bar} for the file foo/bar. See also: --colsep --pipe --pipe-part --arg-file --hostgroups --hgrp Enable hostgroups on arguments. If an argument contains '@' the string after '@' will be removed and treated as a list of hostgroups on which this job is allowed to run. If there is no --sshlogin with a corresponding group, the job will run on any hostgroup. Example: parallel --hostgroups \ --sshlogin @grp1/myserver1 -S @grp1+grp2/myserver2 \ --sshlogin @grp3/myserver3 \ echo ::: my_grp1_arg@grp1 arg_for_grp2@grp2 third@grp1+grp3 my_grp1_arg may be run on either myserver1 or myserver2, third may be run on either myserver1 or myserver3, but arg_for_grp2 will only be run on myserver2. See also: --sshlogin $PARALLEL_HOSTGROUPS $PARALLEL_ARGHOSTGROUPS -I replace-str Use the replacement string replace-str instead of {}. See also: {} --replace [replace-str] -i [replace-str] This option is deprecated; use -I instead. This option is a synonym for -Ireplace-str if replace-str is specified, and for -I {} otherwise. See also: {} --joblog logfile --jl logfile Logfile for executed jobs. Save a list of the executed jobs to logfile in the following TAB separated format: sequence number, sshlogin, start time as seconds since epoch, run time in seconds, bytes in files transferred, bytes in files returned, exit status, signal, and command run. For --pipe bytes transferred and bytes returned are number of input and output of bytes. If logfile is prepended with '+' log lines will be appended to the logfile. To convert the times into ISO-8601 strict do: cat logfile | perl -a -F"\t" -ne \ 'chomp($F[2]=`date -d \@$F[2] +%FT%T`); print join("\t",@F)' If the host is long, you can use column -t to pretty print it: cat joblog | column -t See also: --resume --resume-failed --jobs num -j num --max-procs num -P num Number of jobslots on each machine. Run up to num jobs in parallel. Default is 100%. num Run up to num jobs in parallel. 0 Run as many as possible (this can take a while to determine). Due to a bug -j 0 will also evaluate replacement strings twice up to the number of joblots: # This will not count from 1 but from number-of-jobslots seq 10000 | parallel -j0 echo '{= $_ = $foo++; =}' | head # This will count from 1 seq 10000 | parallel -j100 echo '{= $_ = $foo++; =}' | head num% Multiply the number of CPU threads by num percent. E.g. 100% means one job per CPU thread on each machine. +num Add num to the number of CPU threads. -num Subtract num from the number of CPU threads. expr Evaluate expr. E.g. '12/2' to get 6, '+25%' gives the same as '125%', or complex expressions like '+3*log(55)%' which means: multiply 3 by log(55), multiply that by the number of CPU threads and divide by 100, add this to the number of CPU threads. An expression that evalutates to less that 1 is replaced with 1. procfile Read parameter from file. Use the content of procfile as parameter for -j. E.g. procfile could contain the string 100% or +2 or 10. If procfile is changed when a job completes, procfile is read again and the new number of jobs is computed. If the number is lower than before, running jobs will be allowed to finish but new jobs will not be started until the wanted number of jobs has been reached. This makes it possible to change the number of simultaneous running jobs while GNU parallel is running. If the evaluated number is less than 1 then 1 will be used. If --semaphore is set, the default is 1 thus making a mutex. See also: --use-cores-instead-of-threads --use-sockets-instead-of-threads --keep-order -k Keep sequence of output same as the order of input. Normally the output of a job will be printed as soon as the job completes. Try this to see the difference: parallel -j4 sleep {}\; echo {} ::: 2 1 4 3 parallel -j4 -k sleep {}\; echo {} ::: 2 1 4 3 If used with --onall or --nonall the output will grouped by sshlogin in sorted order. --keep-order cannot keep the output order when used with --pipe --round-robin. Here it instead means, that the jobslots will get the same blocks as input in the same order in every run if the input is kept the same. Run each of these twice and compare: seq 10000000 | parallel --pipe --round-robin 'sleep 0.$RANDOM; wc' seq 10000000 | parallel --pipe -k --round-robin 'sleep 0.$RANDOM; wc' -k only affects the order in which the output is printed - not the order in which jobs are run. See also: --group --line-buffer -L recsize When used with --pipe: Read records of recsize. When used otherwise: Use at most recsize nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. -L 0 means read one line, but insert 0 arguments on the command line. recsize can be postfixed with K, M, G, T, P, k, m, g, t, or p. Implies -X unless -m, --xargs, or --pipe is set. See also: UNIT PREFIX -N --max-lines --block -X -m --xargs --pipe --max-lines [recsize] -l[recsize] When used with --pipe: Read records of recsize lines. When used otherwise: Synonym for the -L option. Unlike -L, the recsize argument is optional. If recsize is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -l 0 is an alias for -l 1. Implies -X unless -m, --xargs, or --pipe is set. See also: UNIT PREFIX -N --block -X -m --xargs --pipe --limit "command args" Dynamic job limit. Before starting a new job run command with args. The exit value of command determines what GNU parallel will do: 0 Below limit. Start another job. 1 Over limit. Start no jobs. 2 Way over limit. Kill the youngest job. You can use any shell command. There are 3 predefined commands: "io n" Limit for I/O. The amount of disk I/O will be computed as a value 0-100, where 0 is no I/O and 100 is at least one disk is 100% saturated. "load n" Similar to --load. "mem n" Similar to --memfree. See also: --memfree --load --latest-line --ll Print the lastest line. Each job gets a single line that is updated with the lastest output from the job. Example: slow_seq() { seq "$@" | perl -ne '$|=1; for(split//){ print; select($a,$a,$a,0.03);}' } export -f slow_seq parallel --shuf -j99 --ll --tag --bar --color slow_seq {} ::: {1..300} See also: --line-buffer --line-buffer --lb Buffer output on line basis. --group will keep the output together for a whole job. --ungroup allows output to mixup with half a line coming from one job and half a line coming from another job. --line-buffer fits between these two: GNU parallel will print a full line, but will allow for mixing lines of different jobs. --line-buffer takes more CPU power than both --group and --ungroup, but can be much faster than --group if the CPU is not the limiting factor. Normally --line-buffer does not buffer on disk, and can thus process an infinite amount of data, but it will buffer on disk when combined with: --keep-order, --results, --compress, and --files. This will make it as slow as --group and will limit output to the available disk space. With --keep-order --line-buffer will output lines from the first job continuously while it is running, then lines from the second job while that is running. It will buffer full lines, but jobs will not mix. Compare: parallel -j0 'echo [{};sleep {};echo {}]' ::: 1 3 2 4 parallel -j0 --lb 'echo [{};sleep {};echo {}]' ::: 1 3 2 4 parallel -j0 -k --lb 'echo [{};sleep {};echo {}]' ::: 1 3 2 4 See also: --group --ungroup --keep-order --tag --link --xapply Link input sources. Read multiple input sources like the command xapply. If multiple input sources are given, one argument will be read from each of the input sources. The arguments can be accessed in the command as {1} .. {n}, so {1} will be a line from the first input source, and {6} will refer to the line with the same line number from the 6th input source. Compare these two: parallel echo {1} {2} ::: 1 2 3 ::: a b c parallel --link echo {1} {2} ::: 1 2 3 ::: a b c Arguments will be recycled if one input source has more arguments than the others: parallel --link echo {1} {2} {3} \ ::: 1 2 ::: I II III ::: a b c d e f g See also: --header :::+ ::::+ --load max-load Only start jobs if load is less than max-load. Do not start new jobs on a given computer unless the number of running processes on the computer is less than max-load. max-load uses the same syntax as --jobs, so 100% for one per CPU is a valid setting. Only difference is 0 which is interpreted as 0.01. See also: --limit --jobs --controlmaster -M Use ssh's ControlMaster to make ssh connections faster. Useful if jobs run remote and are very fast to run. This is disabled for sshlogins that specify their own ssh command. See also: --ssh --sshlogin -m Multiple arguments. Insert as many arguments as the command line length permits. If multiple jobs are being run in parallel: distribute the arguments evenly among the jobs. Use -j1 or --xargs to avoid this. If {} is not used the arguments will be appended to the line. If {} is used multiple times each {} will be replaced with all the arguments. Support for -m with --sshlogin is limited and may fail. If in doubt use -X as that will most likely do what is needed. See also: -X --xargs --memfree size Minimum memory free when starting another job. The size can be postfixed with K, M, G, T, P, k, m, g, t, or p. If the jobs take up very different amount of RAM, GNU parallel will only start as many as there is memory for. If less than size bytes are free, no more jobs will be started. If less than 50% size bytes are free, the youngest job will be killed (as per --term-seq), and put back on the queue to be run later. See also: UNIT PREFIX --term-seq --memsuspend --memsuspend size Suspend jobs when there is less memory available. If the available memory falls below 2 * size, GNU parallel will suspend some of the running jobs. If the available memory falls below size, only one job will be running. If a single job fits in the given size, all jobs will complete without running out of memory. If you have swap available, you can usually lower size to around half the size of a single job - with the slight risk of swapping a little. Jobs will be resumed when more RAM is available - typically when the oldest job completes. --memsuspend only works on local jobs because there is no obvious way to suspend remote jobs. size can be postfixed with K, M, G, T, P, k, m, g, t, or p. See also: UNIT PREFIX --memfree --minversion version Print the version GNU parallel and exit. If the current version of GNU parallel is less than version the exit code is 255. Otherwise it is 0. This is useful for scripts that depend on features only available from a certain version of GNU parallel: parallel --minversion 20170422 && echo halt done=50% supported from version 20170422 && parallel --halt now,done=50% echo ::: {1..100} See also: --version --max-args max-args -n max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case GNU parallel will exit. -n 0 means read one argument, but insert 0 arguments on the command line. max-args can be postfixed with K, M, G, T, P, k, m, g, t, or p (see UNIT PREFIX). Implies -X unless -m is set. See also: -X -m --xargs --max-replace-args --max-replace-args max-args -N max-args Use at most max-args arguments per command line. Like -n but also makes replacement strings {1} .. {max-args} that represents argument 1 .. max-args. If too few args the {n} will be empty. -N 0 means read one argument, but insert 0 arguments on the command line. This will set the owner of the homedir to the user: tr ':' '\n' < /etc/passwd | parallel -N7 chown {1} {6} Implies -X unless -m or --pipe is set. max-args can be postfixed with K, M, G, T, P, k, m, g, t, or p. When used with --pipe -N is the number of records to read. This is somewhat slower than --block. See also: UNIT PREFIX --pipe --block -m -X --max-args --nonall --onall with no arguments. Run the command on all computers given with --sshlogin but take no arguments. GNU parallel will log into --jobs number of computers in parallel and run the job on the computer. -j adjusts how many computers to log into in parallel. This is useful for running the same command (e.g. uptime) on a list of servers. See also: --onall --sshlogin --onall Run all the jobs on all computers given with --sshlogin. GNU parallel will log into --jobs number of computers in parallel and run one job at a time on the computer. The order of the jobs will not be changed, but some computers may finish before others. When using --group the output will be grouped by each server, so all the output from one server will be grouped together. --joblog will contain an entry for each job on each server, so there will be several job sequence 1. See also: --nonall --sshlogin --open-tty -o Open terminal tty. Similar to --tty but does not set --jobs or --ungroup. See also: --tty --output-as-files --outputasfiles --files --files0 Save output to files. Instead of printing the output to stdout (standard output) the output of each job is saved in a file and the filename is then printed. --files0 uses NUL (\0) instead of newline (\n) as separator. See also: --results --pipe --spreadstdin Spread input to jobs on stdin (standard input). Read a block of data from stdin (standard input) and give one block of data as input to one job. The block size is determined by --block (default: 1M). Except for the first and last record GNU parallel only passes full records to the job. The strings --recstart and --recend determine where a record starts and ends: The border between two records is defined as --recend immediately followed by --recstart. GNU parallel splits exactly after --recend and before --recstart. The block will have the last partial record removed before the block is passed on to the job. The partial record will be prepended to next block. You can limit the number of records to be passed with -N, and set the record size with -L. --pipe maxes out at around 1 GB/s input, and 100 MB/s output. If performance is important use --pipe-part. --fifo and --cat will give stdin (standard input) on a fifo or a temporary file. If data is arriving slowly, you can use --block-timeout to finish reading a block early. The data can be spread between the jobs in specific ways using --round-robin, --bin, --shard, --group-by. See the section: SPREADING BLOCKS OF DATA See also: --block --block-timeout --recstart --recend --fifo --cat --pipe-part -N -L --round-robin --pipe-part Pipe parts of a physical file. --pipe-part works similar to --pipe, but is much faster. 5 GB/s can easily be delivered. --pipe-part has a few limitations: • The file must be a normal file or a block device (technically it must be seekable) and must be given using --arg-file or ::::. The file cannot be a pipe, a fifo, or a stream as they are not seekable. If using a block device with lot of NUL bytes, remember to set --recend ''. • Record counting (-N) and line counting (-L/-l) do not work. Instead use --recstart and --recend to determine where records end. See also: --pipe --recstart --recend --arg-file :::: --plain Ignore --profile, $PARALLEL, and ~/.parallel/config. Ignore any --profile, $PARALLEL, and ~/.parallel/config to get full control on the command line (used by GNU parallel internally when called with --sshlogin). See also: --profile --plus Add more replacement strings. Activate additional replacement strings: {+/} {+.} {+..} {+...} {..} {...} {/..} {/...} {##}. The idea being that '{+foo}' matches the opposite of '{foo}' so that: {} = {+/}/{/} = {.}.{+.} = {+/}/{/.}.{+.} = {..}.{+..} = {+/}/{/..}.{+..} = {...}.{+...} = {+/}/{/...}.{+...} {##} is the total number of jobs to be run. It is incompatible with -X/-m/--xargs. {0%} zero-padded jobslot. {0#} zero-padded sequence number. {slot-1} jobslot - 1 (i.e. counting from 0). {seq-1} sequence number - 1 (i.e. counting from 0). {choose_k} is inspired by n choose k: Given a list of n elements, choose k. k is the number of input sources and n is the number of arguments in an input source. The content of the input sources must be the same and the arguments must be unique. {uniq} skips jobs where values from two input sources are the same. Shorthands for variables: {slot} $PARALLEL_JOBSLOT (see {%}) {sshlogin} $PARALLEL_SSHLOGIN {host} $PARALLEL_SSHHOST {agrp} $PARALLEL_ARGHOSTGROUPS {hgrp} $PARALLEL_HOSTGROUPS The following dynamic replacement strings are also activated. They are inspired by bash's parameter expansion: {:-str} str if the value is empty {:num} remove the first num characters {:pos:len} substring from position pos length len {#regexp} remove prefix regexp (non-greedy) {##regexp} remove prefix regexp (greedy) {%regexp} remove postfix regexp (non-greedy) {%%regexp} remove postfix regexp (greedy) {/regexp/str} replace one regexp with str {//regexp/str} replace every regexp with str {^str} uppercase str if found at the start {^^str} uppercase str {,str} lowercase str if found at the start {,,str} lowercase str See also: --rpl {} --process-slot-var varname Set the environment variable varname to the jobslot number-1. seq 10 | parallel --process-slot-var=name echo '$name' {} --progress Show progress of computations. List the computers involved in the task with number of CPUs detected and the max number of jobs to run. After that show progress for each computer: number of running jobs, number of completed jobs, and percentage of all jobs done by this computer. The percentage will only be available after all jobs have been scheduled as GNU parallel only read the next job when ready to schedule it - this is to avoid wasting time and memory by reading everything at startup. By sending GNU parallel SIGUSR2 you can toggle turning on/off --progress on a running GNU parallel process. See also: --eta --bar --max-line-length-allowed Print maximal command line length. Print the maximal number of characters allowed on the command line and exit (used by GNU parallel itself to determine the line length on remote computers). See also: --show-limits --number-of-cpus (obsolete) Print the number of physical CPU cores and exit. --number-of-cores Print the number of physical CPU cores and exit (used by GNU parallel itself to determine the number of physical CPU cores on remote computers). See also: --number-of-sockets --number-of-threads --use-cores-instead-of-threads --jobs --number-of-sockets Print the number of filled CPU sockets and exit (used by GNU parallel itself to determine the number of filled CPU sockets on remote computers). See also: --number-of-cores --number-of-threads --use-sockets-instead-of-threads --jobs --number-of-threads Print the number of hyperthreaded CPU cores and exit (used by GNU parallel itself to determine the number of hyperthreaded CPU cores on remote computers). See also: --number-of-cores --number-of-sockets --jobs --no-keep-order Overrides an earlier --keep-order (e.g. if set in ~/.parallel/config). --nice niceness Run the command at this niceness. By default GNU parallel will run jobs at the same nice level as GNU parallel is started - both on the local machine and remote servers, so you are unlikely to ever use this option. Setting --nice will override this nice level. If the nice level is smaller than the current nice level, it will only affect remote jobs (e.g. if current level is 10 then --nice 5 will cause local jobs to be run at level 10, but remote jobs run at nice level 5). --interactive -p Ask user before running a job. Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with 'y' or 'Y'. Implies -t. --_parset type,varname Used internally by parset. Generate shell code to be eval'ed which will set the variable(s) varname. type can be 'assoc' for associative array or 'var' for normal variables. The only supported use is as part of parset. --parens parensstring Use parensstring instead of {==}. Define start and end parenthesis for {=perl expression=}. The left and the right parenthesis can be multiple characters and are assumed to be the same length. The default is {==} giving {= as the start parenthesis and =} as the end parenthesis. Another useful setting is ,,,, which would make both parenthesis ,,: parallel --parens ,,,, echo foo is ,,s/I/O/g,, ::: FII See also: --rpl {=perl expression=} --profile profilename -J profilename Use profile profilename for options. This is useful if you want to have multiple profiles. You could have one profile for running jobs in parallel on the local computer and a different profile for running jobs on remote computers. profilename corresponds to the file ~/.parallel/profilename. You can give multiple profiles by repeating --profile. If parts of the profiles conflict, the later ones will be used. Default: ~/.parallel/config See also: PROFILE FILES --quote -q Quote command. If your command contains special characters that should not be interpreted by the shell (e.g. ; \ | *), use --quote to escape these. The command must be a simple command (see man bash) without redirections and without variable assignments. Most people will not need this. Quoting is disabled by default. See also: QUOTING command --shell-quote uq() Q() --no-run-if-empty -r Do not run empty input. If the stdin (standard input) only contains whitespace, do not run the command. If used with --pipe this is slow. See also: command --pipe --interactive --noswap Do not start job is computer is swapping. Do not start new jobs on a given computer if there is both swap-in and swap-out activity. The swap activity is only sampled every 10 seconds as the sampling takes 1 second to do. Swap activity is computed as (swap-in)*(swap-out) which in practice is a good value: swapping out is not a problem, swapping in is not a problem, but both swapping in and out usually indicates a problem. --memfree and --memsuspend may give better results, so try using those first. See also: --memfree --memsuspend --record-env Record exported environment. Record current exported environment variables in ~/.parallel/ignored_vars. This will ignore variables currently set when using --env _. So you should set the variables/fuctions, you want to use after running --record-env. See also: --env --session env_parallel --recstart startstring --recend endstring Split record between endstring and startstring. If --recstart is given startstring will be used to split at record start. If --recend is given endstring will be used to split at record end. If both --recstart and --recend are given the combined string endstringstartstring will have to match to find a split position. This is useful if either startstring or endstring match in the middle of a record. If neither --recstart nor --recend are given, then --recend defaults to '\n'. To have no record separator (e.g. for binary files) use --recend "". --recstart and --recend are used with --pipe. Use --regexp to interpret --recstart and --recend as regular expressions. This is slow, however. Use --remove-rec-sep to remove --recstart and --recend before passing the block to the job. See also: --pipe --regexp --remove-rec-sep --regexp Use --regexp to interpret --recstart and --recend as regular expressions. This is slow, however. See also: --pipe --regexp --remove-rec-sep --recstart --recend --remove-rec-sep --removerecsep --rrs Remove record separator. Remove the text matched by --recstart and --recend before piping it to the command. Only used with --pipe/--pipe-part. See also: --pipe --regexp --pipe-part --recstart --recend --results name --res name Save the output into files. Simple string output dir If name does not contain replacement strings and does not end in .csv/.tsv, the output will be stored in a directory tree rooted at name. Within this directory tree, each command will result in three files: name/<ARGS>/stdout and name/<ARGS>/stderr, name/<ARGS>/seq, where <ARGS> is a sequence of directories representing the header of the input source (if using --header :) or the number of the input source and corresponding values. E.g: parallel --header : --results foo echo {a} {b} \ ::: a I II ::: b III IIII will generate the files: foo/a/II/b/III/seq foo/a/II/b/III/stderr foo/a/II/b/III/stdout foo/a/II/b/IIII/seq foo/a/II/b/IIII/stderr foo/a/II/b/IIII/stdout foo/a/I/b/III/seq foo/a/I/b/III/stderr foo/a/I/b/III/stdout foo/a/I/b/IIII/seq foo/a/I/b/IIII/stderr foo/a/I/b/IIII/stdout and parallel --results foo echo {1} {2} ::: I II ::: III IIII will generate the files: foo/1/II/2/III/seq foo/1/II/2/III/stderr foo/1/II/2/III/stdout foo/1/II/2/IIII/seq foo/1/II/2/IIII/stderr foo/1/II/2/IIII/stdout foo/1/I/2/III/seq foo/1/I/2/III/stderr foo/1/I/2/III/stdout foo/1/I/2/IIII/seq foo/1/I/2/IIII/stderr foo/1/I/2/IIII/stdout CSV file output If name ends in .csv/.tsv the output will be a CSV-file named name. .csv gives a comma separated value file. .tsv gives a TAB separated value file. -.csv/-.tsv are special: It will give the file on stdout (standard output). JSON file output If name ends in .json the output will be a JSON-file named name. -.json is special: It will give the file on stdout (standard output). Replacement string output file If name contains a replacement string and the replaced result does not end in /, then the standard output will be stored in a file named by this result. Standard error will be stored in the same file name with '.err' added, and the sequence number will be stored in the same file name with '.seq' added. E.g. parallel --results my_{} echo ::: foo bar baz will generate the files: my_bar my_bar.err my_bar.seq my_baz my_baz.err my_baz.seq my_foo my_foo.err my_foo.seq Replacement string output dir If name contains a replacement string and the replaced result ends in /, then output files will be stored in the resulting dir. E.g. parallel --results my_{}/ echo ::: foo bar baz will generate the files: my_bar/seq my_bar/stderr my_bar/stdout my_baz/seq my_baz/stderr my_baz/stdout my_foo/seq my_foo/stderr my_foo/stdout See also: --output-as-files --tag --header --joblog --resume Resumes from the last unfinished job. By reading --joblog or the --results dir GNU parallel will figure out the last unfinished job and continue from there. As GNU parallel only looks at the sequence numbers in --joblog then the input, the command, and --joblog all have to remain unchanged; otherwise GNU parallel may run wrong commands. See also: --joblog --results --resume-failed --retries --resume-failed Retry all failed and resume from the last unfinished job. By reading --joblog GNU parallel will figure out the failed jobs and run those again. After that it will resume last unfinished job and continue from there. As GNU parallel only looks at the sequence numbers in --joblog then the input, the command, and --joblog all have to remain unchanged; otherwise GNU parallel may run wrong commands. See also: --joblog --resume --retry-failed --retries --retry-failed Retry all failed jobs in joblog. By reading --joblog GNU parallel will figure out the failed jobs and run those again. --retry-failed ignores the command and arguments on the command line: It only looks at the joblog. Differences between --resume, --resume-failed, --retry-failed In this example exit {= $_%=2 =} will cause every other job to fail. timeout -k 1 4 parallel --joblog log -j10 \ 'sleep {}; exit {= $_%=2 =}' ::: {10..1} 4 jobs completed. 2 failed: Seq [...] Exitval Signal Command 10 [...] 1 0 sleep 1; exit 1 9 [...] 0 0 sleep 2; exit 0 8 [...] 1 0 sleep 3; exit 1 7 [...] 0 0 sleep 4; exit 0 --resume does not care about the Exitval, but only looks at Seq. If the Seq is run, it will not be run again. So if needed, you can change the command for the seqs not run yet: parallel --resume --joblog log -j10 \ 'sleep .{}; exit {= $_%=2 =}' ::: {10..1} Seq [...] Exitval Signal Command [... as above ...] 1 [...] 0 0 sleep .10; exit 0 6 [...] 1 0 sleep .5; exit 1 5 [...] 0 0 sleep .6; exit 0 4 [...] 1 0 sleep .7; exit 1 3 [...] 0 0 sleep .8; exit 0 2 [...] 1 0 sleep .9; exit 1 --resume-failed cares about the Exitval, but also only looks at Seq to figure out which commands to run. Again this means you can change the command, but not the arguments. It will run the failed seqs and the seqs not yet run: parallel --resume-failed --joblog log -j10 \ 'echo {};sleep .{}; exit {= $_%=3 =}' ::: {10..1} Seq [...] Exitval Signal Command [... as above ...] 10 [...] 1 0 echo 1;sleep .1; exit 1 8 [...] 0 0 echo 3;sleep .3; exit 0 6 [...] 2 0 echo 5;sleep .5; exit 2 4 [...] 1 0 echo 7;sleep .7; exit 1 2 [...] 0 0 echo 9;sleep .9; exit 0 --retry-failed cares about the Exitval, but takes the command from the joblog. It ignores any arguments or commands given on the command line: parallel --retry-failed --joblog log -j10 this part is ignored Seq [...] Exitval Signal Command [... as above ...] 10 [...] 1 0 echo 1;sleep .1; exit 1 6 [...] 2 0 echo 5;sleep .5; exit 2 4 [...] 1 0 echo 7;sleep .7; exit 1 See also: --joblog --resume --resume-failed --retries --retries n Try failing jobs n times. If a job fails, retry it on another computer on which it has not failed. Do this n times. If there are fewer than n computers in --sshlogin GNU parallel will re-use all the computers. This is useful if some jobs fail for no apparent reason (such as network failure). n=0 means infinite. See also: --term-seq --sshlogin --return filename Transfer files from remote computers. --return is used with --sshlogin when the arguments are files on the remote computers. When processing is done the file filename will be transferred from the remote computer using rsync and will be put relative to the default login dir. E.g. echo foo/bar.txt | parallel --return {.}.out \ --sshlogin server.example.com touch {.}.out This will transfer the file $HOME/foo/bar.out from the computer server.example.com to the file foo/bar.out after running touch foo/bar.out on server.example.com. parallel -S server --trc out/./{}.out touch {}.out ::: in/file This will transfer the file in/file.out from the computer server.example.com to the files out/in/file.out after running touch in/file.out on server. echo /tmp/foo/bar.txt | parallel --return {.}.out \ --sshlogin server.example.com touch {.}.out This will transfer the file /tmp/foo/bar.out from the computer server.example.com to the file /tmp/foo/bar.out after running touch /tmp/foo/bar.out on server.example.com. Multiple files can be transferred by repeating the option multiple times: echo /tmp/foo/bar.txt | parallel \ --sshlogin server.example.com \ --return {.}.out --return {.}.out2 touch {.}.out {.}.out2 --return is ignored when used with --sshlogin : or when not used with --sshlogin. For details on transferring see --transferfile. See also: --transfer --transferfile --sshlogin --cleanup --workdir --round-robin --round Distribute chunks of standard input in a round robin fashion. Normally --pipe will give a single block to each instance of the command. With --round-robin all blocks will at random be written to commands already running. This is useful if the command takes a long time to initialize. With --keep-order and --round-robin the jobslots will get the same blocks as input in the same order in every run if the input is kept the same. See details under --keep-order. --round-robin implies --pipe, except if --pipe-part is given. See the section: SPREADING BLOCKS OF DATA. See also: --bin --group-by --shard --rpl 'tag perl expression' Define replacement string. Use tag as a replacement string for perl expression. This makes it possible to define your own replacement strings. GNU parallel's 7 replacement strings are implemented as: --rpl '{} ' --rpl '{#} 1 $_=$job->seq()' --rpl '{%} 1 $_=$job->slot()' --rpl '{/} s:.*/::' --rpl '{//} $Global::use{"File::Basename"} ||= eval "use File::Basename; 1;"; $_ = dirname($_);' --rpl '{/.} s:.*/::; s:\.[^/.]+$::;' --rpl '{.} s:\.[^/.]+$::' The --plus replacement strings are implemented as: --rpl '{+/} s:/[^/]*$:: || s:.*$::' --rpl '{+.} s:.*\.:: || s:.*$::' --rpl '{+..} s:.*\.([^/.]+\.[^/.]+)$:$1: || s:.*$::' --rpl '{+...} s:.*\.([^/.]+\.[^/.]+\.[^/.]+)$:$1: || s:.*$::' --rpl '{..} s:\.[^/.]+\.[^/.]+$::' --rpl '{...} s:\.[^/.]+\.[^/.]+\.[^/.]+$::' --rpl '{/..} s:.*/::; s:\.[^/.]+\.[^/.]+$::' --rpl '{/...} s:.*/::; s:\.[^/.]+\.[^/.]+\.[^/.]+$::' --rpl '{choose_k} for $t (2..$#arg){ if($arg[$t-1] ge $arg[$t]) { skip() } }' --rpl '{##} 1 $_=total_jobs()' --rpl '{0%} 1 $f=1+int((log($Global::max_jobs_running||1)/ log(10))); $_=sprintf("%0${f}d",slot())' --rpl '{0#} 1 $f=1+int((log(total_jobs())/log(10))); $_=sprintf("%0${f}d",seq())' --rpl '{seq(.*?)} $_=eval q{$job->seq()}.qq{$$1}' --rpl '{slot(.*?)} $_=eval q{$job->slot()}.qq{$$1}' --rpl '{:-([^}]+?)} $_ ||= $$1' --rpl '{:(\d+?)} substr($_,0,$$1) = ""' --rpl '{:(\d+?):(\d+?)} $_ = substr($_,$$1,$$2);' --rpl '{#([^#}][^}]*?)} $nongreedy=::make_regexp_ungreedy($$1); s/^$nongreedy(.*)/$1/;' --rpl '{##([^#}][^}]*?)} s/^$$1//;' --rpl '{%([^}]+?)} $nongreedy=::make_regexp_ungreedy($$1); s/(.*)$nongreedy$/$1/;' --rpl '{%%([^}]+?)} s/$$1$//;' --rpl '{/([^}]+?)/([^}]*?)} s/$$1/$$2/;' --rpl '{^([^}]+?)} s/^($$1)/uc($1)/e;' --rpl '{^^([^}]+?)} s/($$1)/uc($1)/eg;' --rpl '{,([^}]+?)} s/^($$1)/lc($1)/e;' --rpl '{,,([^}]+?)} s/($$1)/lc($1)/eg;' --rpl '{slot} 1 $_="\${PARALLEL_JOBSLOT}";uq()' --rpl '{host} 1 $_="\${PARALLEL_SSHHOST}";uq()' --rpl '{sshlogin} 1 $_="\${PARALLEL_SSHLOGIN}";uq()' --rpl '{hgrp} 1 $_="\${PARALLEL_HOSTGROUPS}";uq()' --rpl '{agrp} 1 $_="\${PARALLEL_ARGHOSTGROUPS}";uq()' If the user defined replacement string starts with '{' it can also be used as a positional replacement string (like {2.}). It is recommended to only change $_ but you have full access to all of GNU parallel's internal functions and data structures. Here are a few examples: Is the job sequence even or odd? --rpl '{odd} $_ = seq() % 2 ? "odd" : "even"' Pad job sequence with leading zeros to get equal width --rpl '{0#} $f=1+int("".(log(total_jobs())/log(10))); $_=sprintf("%0${f}d",seq())' Job sequence counting from 0 --rpl '{#0} $_ = seq() - 1' Job slot counting from 2 --rpl '{%1} $_ = slot() + 1' Remove all extensions --rpl '{:} s:(\.[^/]+)*$::' You can have dynamic replacement strings by including parenthesis in the replacement string and adding a regular expression between the parenthesis. The matching string will be inserted as $$1: parallel --rpl '{%(.*?)} s/$$1//' echo {%.tar.gz} ::: my.tar.gz parallel --rpl '{:%(.+?)} s:$$1(\.[^/]+)*$::' \ echo {:%_file} ::: my_file.tar.gz parallel -n3 --rpl '{/:%(.*?)} s:.*/(.*)$$1(\.[^/]+)*$:$1:' \ echo job {#}: {2} {2.} {3/:%_1} ::: a/b.c c/d.e f/g_1.h.i You can even use multiple matches: parallel --rpl '{/(.+?)/(.*?)} s/$$1/$$2/;' echo {/replacethis/withthis} {/b/C} ::: a_replacethis_b parallel --rpl '{(.*?)/(.*?)} $_="$$2$_$$1"' \ echo {swap/these} ::: -middle- See also: {=perl expression=} --parens --rsync-opts options Options to pass on to rsync. Setting --rsync-opts takes precedence over setting the environment variable $PARALLEL_RSYNC_OPTS. --max-chars max-chars -s max-chars Limit length of command. Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system- dependent, and is calculated as the argument length limit for exec, less the size of your environment. The default value is the maximum. max-chars can be postfixed with K, M, G, T, P, k, m, g, t, or p (see UNIT PREFIX). Implies -X unless -m or --xargs is set. See also: -X -m --xargs --max-line-length-allowed --show-limits --show-limits Display limits given by the operating system. Display the limits on the command-line length which are imposed by the operating system and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want GNU parallel to do anything. See also: --max-chars --max-line-length-allowed --version --semaphore Work as a counting semaphore. --semaphore will cause GNU parallel to start command in the background. When the number of jobs given by --jobs is reached, GNU parallel will wait for one of these to complete before starting another command. --semaphore implies --bg unless --fg is specified. The command sem is an alias for parallel --semaphore. See also: man sem --bg --fg --semaphore-name --semaphore-timeout --wait --semaphore-name name --id name Use name as the name of the semaphore. The default is the name of the controlling tty (output from tty). The default normally works as expected when used interactively, but when used in a script name should be set. $$ or my_task_name are often a good value. The semaphore is stored in ~/.parallel/semaphores/ Implies --semaphore. See also: man sem --semaphore --semaphore-timeout secs --st secs If secs > 0: If the semaphore is not released within secs seconds, take it anyway. If secs < 0: If the semaphore is not released within secs seconds, exit. secs is in seconds, but can be postfixed with s, m, h, or d (see the section TIME POSTFIXES). Implies --semaphore. See also: man sem --seqreplace replace-str Use the replacement string replace-str instead of {#} for job sequence number. See also: {#} --session Record names in current environment in $PARALLEL_IGNORED_NAMES and exit. Only used with env_parallel. Aliases, functions, and variables with names in $PARALLEL_IGNORED_NAMES will not be copied. So you should set variables/function you want copied after running --session. It is similar to --record-env, but only for this session. Only supported in Ash, Bash, Dash, Ksh, Sh, and Zsh. See also: --env --record-env env_parallel --shard shardexpr Use shardexpr as shard key and shard input to the jobs. shardexpr is [column number|column name] [perlexpression] e.g.: 3 Address 3 $_%=100 Address s/\d//g Each input line is split using --colsep. The string of the column is put into $_, the perl expression is executed, the resulting string is hashed so that all lines of a given value is given to the same job slot. This is similar to sharding in databases. The performance is in the order of 100K rows per second. Faster if the shardcol is small (<10), slower if it is big (>100). --shard requires --pipe and a fixed numeric value for --jobs. See the section: SPREADING BLOCKS OF DATA. See also: --bin --group-by --round-robin --shebang --hashbang GNU parallel can be called as a shebang (#!) command as the first line of a script. The content of the file will be treated as inputsource. Like this: #!/usr/bin/parallel --shebang -r wget https://ftpmirror.gnu.org/parallel/parallel-20120822.tar.bz2 https://ftpmirror.gnu.org/parallel/parallel-20130822.tar.bz2 https://ftpmirror.gnu.org/parallel/parallel-20140822.tar.bz2 --shebang must be set as the first option. On FreeBSD env is needed: #!/usr/bin/env -S parallel --shebang -r wget https://ftpmirror.gnu.org/parallel/parallel-20120822.tar.bz2 https://ftpmirror.gnu.org/parallel/parallel-20130822.tar.bz2 https://ftpmirror.gnu.org/parallel/parallel-20140822.tar.bz2 There are many limitations of shebang (#!) depending on your operating system. See details on https://www.in-ulm.de/~mascheck/various/shebang/ See also: --shebang-wrap --shebang-wrap GNU parallel can parallelize scripts by wrapping the shebang line. If the program can be run like this: cat arguments | parallel the_program then the script can be changed to: #!/usr/bin/parallel --shebang-wrap /original/parser --options E.g. #!/usr/bin/parallel --shebang-wrap /usr/bin/python If the program can be run like this: cat data | parallel --pipe the_program then the script can be changed to: #!/usr/bin/parallel --shebang-wrap --pipe /orig/parser --opts E.g. #!/usr/bin/parallel --shebang-wrap --pipe /usr/bin/perl -w --shebang-wrap must be set as the first option. See also: --shebang --shell-completion shell Generate shell completion code for interactive shells. Supported shells: bash zsh. Use auto as shell to automatically detect running shell. Activate the completion code with: zsh% eval "$(parallel --shell-completion auto)" bash$ eval "$(parallel --shell-completion auto)" Or put this `/usr/share/zsh/site-functions/_parallel`, then `compinit` to generate `~/.zcompdump`: #compdef parallel (( $+functions[_comp_parallel] )) || eval "$(parallel --shell-completion auto)" && _comp_parallel --shell-quote Does not run the command but quotes it. Useful for making quoted composed commands for GNU parallel. Multiple --shell-quote with quote the string multiple times, so parallel --shell-quote | parallel --shell-quote can be written as parallel --shell-quote --shell-quote. See also: --quote --shuf Shuffle jobs. When having multiple input sources it is hard to randomize jobs. --shuf will generate all jobs, and shuffle them before running them. This is useful to get a quick preview of the results before running the full batch. Combined with --halt soon,done=1% you can run a random 1% sample of all jobs: parallel --shuf --halt soon,done=1% echo ::: {1..100} ::: {1..100} See also: --halt --skip-first-line Do not use the first line of input (used by GNU parallel itself when called with --shebang). --sql DBURL (obsolete) Use --sql-master instead. --sql-master DBURL Submit jobs via SQL server. DBURL must point to a table, which will contain the same information as --joblog, the values from the input sources (stored in columns V1 .. Vn), and the output (stored in columns Stdout and Stderr). If DBURL is prepended with '+' GNU parallel assumes the table is already made with the correct columns and appends the jobs to it. If DBURL is not prepended with '+' the table will be dropped and created with the correct amount of V-columns unless --sqlmaster does not run any jobs, but it creates the values for the jobs to be run. One or more --sqlworker must be run to actually execute the jobs. If --wait is set, GNU parallel will wait for the jobs to complete. The format of a DBURL is: [sql:]vendor://[[user][:pwd]@][host][:port]/[db]/table E.g. sql:mysql://hr:hr@localhost:3306/hrdb/jobs mysql://scott:tiger@my.example.com/pardb/paralleljobs sql:oracle://scott:tiger@ora.example.com/xe/parjob postgresql://scott:tiger@pg.example.com/pgdb/parjob pg:///parjob sqlite3:///%2Ftmp%2Fpardb.sqlite/parjob csv:///%2Ftmp%2Fpardb/parjob Notice how / in the path of sqlite and CVS must be encoded as %2F. Except the last / in CSV which must be a /. It can also be an alias from ~/.sql/aliases: :myalias mysql:///mydb/paralleljobs See also: --sql-and-worker --sql-worker --joblog --sql-and-worker DBURL Shorthand for: --sql-master DBURL --sql-worker DBURL. See also: --sql-master --sql-worker --sql-worker DBURL Execute jobs via SQL server. Read the input sources variables from the table pointed to by DBURL. The command on the command line should be the same as given by --sqlmaster. If you have more than one --sqlworker jobs may be run more than once. If --sqlworker runs on the local machine, the hostname in the SQL table will not be ':' but instead the hostname of the machine. See also: --sql-master --sql-and-worker --ssh sshcommand GNU parallel defaults to using ssh for remote access. This can be overridden with --ssh. It can also be set on a per server basis with --sshlogin. See also: --sshlogin --ssh-delay duration Delay starting next ssh by duration. GNU parallel will not start another ssh for the next duration. duration is in seconds, but can be postfixed with s, m, h, or d. See also: TIME POSTFIXES --sshlogin --delay --sshlogin [@hostgroups/][ncpus/][[user][:[password]]@]host[:port][,...] --sshlogin @hostgroup -S [@hostgroups/][ncpus/][ssh command][[user][:[password]]@]host[:port][,...] -S @hostgroup Distribute jobs to remote computers. The jobs will be run on a list of remote computers. @hostgroups/ One or more groups this sshlogin belongs to. Multiple groups are separated by '+'. The sshlogin will always be added to a hostgroup named the same as sshlogin. If only the @hostgroup is given, only the sshlogins in that hostgroup will be used. Multiple @hostgroup can be given. See --hostgroup. Examples: @prod/, @dev+remote/ ncpus/ Force number of CPU threads. GNU parallel will determine the number of CPUs on the remote computers and run the number of jobs as specified by -j. If the number ncpus is given GNU parallel will use this number for number of CPU threads on the host. Normally ncpus will not be needed. Examples: 4/, 12/ ssh command The ssh command to use. The ssh command must be followed by a space. Example: /usr/bin/lsh -z , autossh -C user User name to log in as. Defaults to the current user name. Examples: alice, bob :password Use password for authentication (using sshpass). password cannot contain space. If password is omitted, GNU parallel will use $SSHPASS. If : is omitted use ssh's default authentication. In this case login must not require a password (ssh-agent and ssh-copy-id may help with that). Examples: :mypassword, : host Hostname or IP address of server. (This is what you will use the most). Examples: server01, 10.1.2.3, [2001:470:142:4::a], 2001:470:142:5::116. Ranges of hostnames can be given in [] like this: server[1,3,8-10] (for server1, server3, server8, server9, server10) or server[001,003,008-010] (for server001, server003, server008, server009, server010). With Bash's brace expansion you can do: -S{dev,prod}[001-100] to get -Sdev[001-100] -Sprod[001-100] More []'s are allowed: server[01-10].cluster[1-5].example.net :port Port number to connect to. Examples: :22, :2222. For IPv6 you can use p or # instead of :. Examples: [2001:470:142:4::a]:2222, 2001:470:142:5::116p2222, 2001:470:142:5::116#22222 There are 3 names with special meaning: : Means 'no ssh' and will therefore run on the local computer. .. Read sshlogins from ~/.parallel/sshloginfile or $XDG_CONFIG_HOME/parallel/sshloginfile - Read sshlogins from stdin (standard input). To specify more sshlogins separate the sshlogins by comma, newline (in the same string), or repeat the options multiple times. GNU parallel splits on , (comma) so if your sshlogin contains , (comma) you need to replace it with \, or ,, See --sshloginfile for complete examples. The remote host must have GNU parallel installed. --sshlogin is known to cause problems with -m and -X. See also: --basefile --transferfile --return --cleanup --trc --sshloginfile --workdir --filter-hosts --ssh --sshloginfile filename --slf filename File with sshlogins. The file consists of sshlogins on separate lines. Empty lines and lines starting with '#' are ignored. Example: server.example.com username@server2.example.com 8/my-8-cpu-server.example.com 2/my_other_username@my-dualcore.example.net # These servers have SSH running on port 2222 ssh -p 2222 server.example.net server01.example.net:2222 4/ssh -p 2222 quadserver.example.net # Use a different ssh program myssh -p 2222 -l myusername hexacpu.example.net # Use a different ssh program with default number of CPUs //opt/homebrew/bin/myssh -p 2222 -l myusername hexacpu # Use a different ssh program with 6 CPUs 6//opt/homebrew/bin/myssh -p 2222 -l myusername hexacpu # Assume 16 CPUs on the local computer 16/: # Use password for authentication user:password@host # Use $SSHPASS for authentication user:@host # Use $SSHPASS for authentication and current username :@host # Use password for authentication and current username :password@host # Login in as bob with :p@ss:w0rd@ as password bob::p@ss:w0rd@@host # Put server1 in hostgroup1 @hostgroup1/server1 # Put myusername@server2 in hostgroup1+hostgroup2 @hostgroup1+hostgroup2/myusername@server2 # Force 4 CPUs and put 'ssh -p 2222 server3' in hostgroup1 @hostgroup1/4/ssh -p 2222 server3 # TODO example with ,, When using a different ssh program the last argument must be the hostname. Multiple --sshloginfile are allowed. GNU parallel will first look for the file in current dir; if that fails it look for the file in ~/.parallel. There are 3 names with special meaning: .. Read sshlogins from ~/.parallel/sshloginfile . Read sshlogins from /etc/parallel/sshloginfile - Read sshlogins from stdin (standard input). If the sshloginfile is changed it will be re-read when a job finishes though at most once per second. This makes it possible to add and remove hosts while running. This can be used to have a daemon that updates the sshloginfile to only contain servers that are up: cp original.slf tmp2.slf while [ 1 ] ; do nice parallel --nonall -j0 -k --slf original.slf \ --tag echo | perl 's/\t$//' > tmp.slf if diff tmp.slf tmp2.slf; then mv tmp.slf tmp2.slf fi sleep 10 done & parallel --slf tmp2.slf ... See also: --filter-hosts --slotreplace replace-str Use the replacement string replace-str instead of {%} for job slot number. See also: {%} --silent Silent. The job to be run will not be printed. This is the default. Can be reversed with -v. See also: -v --template file=repl --tmpl file=repl Replace replacement strings in file and save it in repl. All replacement strings in the contents of file will be replaced. All replacement strings in the name repl will be replaced. With --cleanup the new file will be removed when the job is done. If my.tmpl contains this: Xval: {x} Yval: {y} FixedValue: 9 # x with 2 decimals DecimalX: {=x $_=sprintf("%.2f",$_) =} TenX: {=x $_=$_*10 =} RandomVal: {=1 $_=rand() =} it can be used like this: myprog() { echo Using "$@"; cat "$@"; } export -f myprog parallel --cleanup --header : --tmpl my.tmpl={#}.t myprog {#}.t \ ::: x 1.234 2.345 3.45678 ::: y 1 2 3 See also: {} --cleanup --tty Open terminal tty. If GNU parallel is used for starting a program that accesses the tty (such as an interactive program) then this option may be needed. It will default to starting only one job at a time (i.e. -j1), not buffer the output (i.e. -u), and it will open a tty for the job. You can of course override -j1 and -u. Using --tty unfortunately means that GNU parallel cannot kill the jobs (with --timeout, --memfree, or --halt). This is due to GNU parallel giving each child its own process group, which is then killed. Process groups are dependant on the tty. See also: --ungroup --open-tty --tag Tag lines with arguments. Each output line will be prepended with the arguments and TAB (\t). When combined with --onall or --nonall the lines will be prepended with the sshlogin instead. --tag is ignored when using -u. See also: --tagstring --ctag --tagstring str Tag lines with a string. Each output line will be prepended with str and TAB (\t). str can contain replacement strings such as {}. --tagstring is ignored when using -u, --onall, and --nonall. See also: --tag --ctagstring --tee Pipe all data to all jobs. Used with --pipe/--pipe-part and :::. seq 1000 | parallel --pipe --tee -v wc {} ::: -w -l -c How many numbers in 1..1000 contain 0..9, and how many bytes do they fill: seq 1000 | parallel --pipe --tee --tag \ 'grep {1} | wc {2}' ::: {0..9} ::: -l -c How many words contain a..z and how many bytes do they fill? parallel -a /usr/share/dict/words --pipe-part --tee --tag \ 'grep {1} | wc {2}' ::: {a..z} ::: -l -c See also: ::: --pipe --pipe-part --term-seq sequence Termination sequence. When a job is killed due to --timeout, --memfree, --halt, or abnormal termination of GNU parallel, sequence determines how the job is killed. The default is: TERM,200,TERM,100,TERM,50,KILL,25 which sends a TERM signal, waits 200 ms, sends another TERM signal, waits 100 ms, sends another TERM signal, waits 50 ms, sends a KILL signal, waits 25 ms, and exits. GNU parallel detects if a process dies before the waiting time is up. See also: --halt --timeout --memfree --total-jobs jobs --total jobs Provide the total number of jobs for computing ETA which is also used for --bar. Without --total-jobs GNU Parallel will read all jobs before starting a job. --total-jobs is useful if the input is generated slowly. See also: --bar --eta --tmpdir dirname Directory for temporary files. GNU parallel normally buffers output into temporary files in /tmp. By setting --tmpdir you can use a different dir for the files. Setting --tmpdir is equivalent to setting $TMPDIR. See also: --compress $TMPDIR $PARALLEL_REMOTE_TMPDIR --tmux (Long beta testing) Use tmux for output. Start a tmux session and run each job in a window in that session. No other output will be produced. See also: --tmuxpane --tmuxpane (Long beta testing) Use tmux for output but put output into panes in the first window. Useful if you want to monitor the progress of less than 100 concurrent jobs. See also: --tmux --timeout duration Time out for command. If the command runs for longer than duration seconds it will get killed as per --term-seq. If duration is followed by a % then the timeout will dynamically be computed as a percentage of the median average runtime of successful jobs. Only values > 100% will make sense. duration is in seconds, but can be postfixed with s, m, h, or d. See also: TIME POSTFIXES --term-seq --retries --verbose -t Print the job to be run on stderr (standard error). See also: -v --interactive --transfer Transfer files to remote computers. Shorthand for: --transferfile {}. See also: --transferfile. --transferfile filename --tf filename Transfer filename to remote computers. --transferfile is used with --sshlogin to transfer files to the remote computers. The files will be transferred using rsync and will be put relative to the work dir. The filename will normally contain a replacement string. If the path contains /./ the remaining path will be relative to the work dir (for details: see rsync). If the work dir is /home/user, the transferring will be as follows: /tmp/foo/bar => /tmp/foo/bar tmp/foo/bar => /home/user/tmp/foo/bar /tmp/./foo/bar => /home/user/foo/bar tmp/./foo/bar => /home/user/foo/bar
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This will transfer the file foo/bar.txt to the computer server.example.com to the file $HOME/foo/bar.txt before running wc foo/bar.txt on server.example.com: echo foo/bar.txt | parallel --transferfile {} \ --sshlogin server.example.com wc This will transfer the file /tmp/foo/bar.txt to the computer server.example.com to the file /tmp/foo/bar.txt before running wc /tmp/foo/bar.txt on server.example.com: echo /tmp/foo/bar.txt | parallel --transferfile {} \ --sshlogin server.example.com wc This will transfer the file /tmp/foo/bar.txt to the computer server.example.com to the file foo/bar.txt before running wc ./foo/bar.txt on server.example.com: echo /tmp/./foo/bar.txt | parallel --transferfile {} \ --sshlogin server.example.com wc {= s:.*/\./:./: =} --transferfile is often used with --return and --cleanup. A shorthand for --transferfile {} is --transfer. --transferfile is ignored when used with --sshlogin : or when not used with --sshlogin. See also: --workdir --sshlogin --basefile --return --cleanup --trc filename Transfer, Return, Cleanup. Shorthand for: --transfer --return filename --cleanup See also: --transfer --return --cleanup --trim <n|l|r|lr|rl> Trim white space in input. n No trim. Input is not modified. This is the default. l Left trim. Remove white space from start of input. E.g. " a bc " -> "a bc ". r Right trim. Remove white space from end of input. E.g. " a bc " -> " a bc". lr rl Both trim. Remove white space from both start and end of input. E.g. " a bc " -> "a bc". This is the default if --colsep is used. See also: --no-run-if-empty {} --colsep --ungroup -u Ungroup output. Output is printed as soon as possible and bypasses GNU parallel internal processing. This may cause output from different commands to be mixed thus should only be used if you do not care about the output. Compare these: seq 4 | parallel -j0 \ 'sleep {};echo -n start{};sleep {};echo {}end' seq 4 | parallel -u -j0 \ 'sleep {};echo -n start{};sleep {};echo {}end' It also disables --tag. GNU parallel outputs faster with -u. Compare the speeds of these: parallel seq ::: 300000000 >/dev/null parallel -u seq ::: 300000000 >/dev/null parallel --line-buffer seq ::: 300000000 >/dev/null Can be reversed with --group. See also: --line-buffer --group --extensionreplace replace-str --er replace-str Use the replacement string replace-str instead of {.} for input line without extension. See also: {.} --use-sockets-instead-of-threads See also: --use-cores-instead-of-threads --use-cores-instead-of-threads --use-cpus-instead-of-cores (obsolete) Determine how GNU parallel counts the number of CPUs. GNU parallel uses this number when the number of jobslots (--jobs) is computed relative to the number of CPUs (e.g. 100% or +1). CPUs can be counted in three different ways: sockets The number of filled CPU sockets (i.e. the number of physical chips). cores The number of physical cores (i.e. the number of physical compute cores). threads The number of hyperthreaded cores (i.e. the number of virtual cores - with some of them possibly being hyperthreaded) Normally the number of CPUs is computed as the number of CPU threads. With --use-sockets-instead-of-threads or --use-cores-instead-of-threads you can force it to be computed as the number of filled sockets or number of cores instead. Most users will not need these options. --use-cpus-instead-of-cores is a (misleading) alias for --use-sockets-instead-of-threads and is kept for backwards compatibility. See also: --number-of-threads --number-of-cores --number-of-sockets -v Verbose. Print the job to be run on stdout (standard output). Can be reversed with --silent. Use -v -v to print the wrapping ssh command when running remotely. See also: -t --version -V Print the version GNU parallel and exit. --workdir mydir --wd mydir Jobs will be run in the dir mydir. The default is the current dir for the local machine, and the login dir for remote computers. Files transferred using --transferfile and --return will be relative to mydir on remote computers. The special mydir value ... will create working dirs under ~/.parallel/tmp/. If --cleanup is given these dirs will be removed. The special mydir value . uses the current working dir. If the current working dir is beneath your home dir, the value . is treated as the relative path to your home dir. This means that if your home dir is different on remote computers (e.g. if your login is different) the relative path will still be relative to your home dir. To see the difference try: parallel -S server pwd ::: "" parallel --wd . -S server pwd ::: "" parallel --wd ... -S server pwd ::: "" mydir can contain GNU parallel's replacement strings. --wait Wait for all commands to complete. Used with --semaphore or --sqlmaster. See also: man sem -X Multiple arguments with context replace. Insert as many arguments as the command line length permits. If multiple jobs are being run in parallel: distribute the arguments evenly among the jobs. Use -j1 to avoid this. If {} is not used the arguments will be appended to the line. If {} is used as part of a word (like pic{}.jpg) then the whole word will be repeated. If {} is used multiple times each {} will be replaced with the arguments. Normally -X will do the right thing, whereas -m can give unexpected results if {} is used as part of a word. Support for -X with --sshlogin is limited and may fail. See also: -m --exit -x Exit if the size (see the -s option) is exceeded. --xargs Multiple arguments. Insert as many arguments as the command line length permits. If {} is not used the arguments will be appended to the line. If {} is used multiple times each {} will be replaced with all the arguments. Support for --xargs with --sshlogin is limited and may fail. See also: -X See: man parallel_examples SPREADING BLOCKS OF DATA --round-robin, --pipe-part, --shard, --bin and --group-by are all specialized versions of --pipe. In the following n is the number of jobslots given by --jobs. A record starts with --recstart and ends with --recend. It is typically a full line. A chunk is a number of full records that is approximately the size of a block. A block can contain half records, a chunk cannot. --pipe starts one job per chunk. It reads blocks from stdin (standard input). It finds a record end near a block border and passes a chunk to the program. --pipe-part starts one job per chunk - just like normal --pipe. It first finds record endings near all block borders in the file and then starts the jobs. By using --block -1 it will set the block size to size-of-file/n. Used this way it will start n jobs in total. --round-robin starts n jobs in total. It reads a block and passes a chunk to whichever job is ready to read. It does not parse the content except for identifying where a record ends to make sure it only passes full records. --shard starts n jobs in total. It parses each line to read the string in the given column. Based on this string the line is passed to one of the n jobs. All lines having this string will be given to the same jobslot. --bin works like --shard but the value of the column must be numeric and is the jobslot number it will be passed to. If the value is bigger than n, then n will be subtracted from the value until the value is smaller than or equal to n. --group-by starts one job per chunk. Record borders are not given by --recend/--recstart. Instead a record is defined by a group of lines having the same string in a given column. So the string of a given column changes at a chunk border. With --pipe every line is parsed, with --pipe-part only a few lines are parsed to find the chunk border. --group-by can be combined with --round-robin or --pipe-part. TIME POSTFIXES Arguments that give a duration are given in seconds, but can be expressed as floats postfixed with s, m, h, or d which would multiply the float by 1, 60, 60*60, or 60*60*24. Thus these are equivalent: 100000 and 1d3.5h16.6m4s. UNIT PREFIX Many numerical arguments in GNU parallel can be postfixed with K, M, G, T, P, k, m, g, t, or p which would multiply the number with 1024, 1048576, 1073741824, 1099511627776, 1125899906842624, 1000, 1000000, 1000000000, 1000000000000, or 1000000000000000, respectively. You can even give it as a math expression. E.g. 1000000 can be written as 1M-12*2.024*2k. QUOTING GNU parallel is very liberal in quoting. You only need to quote characters that have special meaning in shell: ( ) $ ` ' " < > ; | \ and depending on context these needs to be quoted, too: ~ & ! ? space * { # Therefore most people will never need more quoting than putting '\' in front of the special characters. Often you can simply put \' around every ': perl -ne '/^\S+\s+\S+$/ and print $ARGV,"\n"' file can be quoted: parallel perl -ne \''/^\S+\s+\S+$/ and print $ARGV,"\n"'\' ::: file However, when you want to use a shell variable you need to quote the $-sign. Here is an example using $PARALLEL_SEQ. This variable is set by GNU parallel itself, so the evaluation of the $ must be done by the sub shell started by GNU parallel: seq 10 | parallel -N2 echo seq:\$PARALLEL_SEQ arg1:{1} arg2:{2} If the variable is set before GNU parallel starts you can do this: VAR=this_is_set_before_starting echo test | parallel echo {} $VAR Prints: test this_is_set_before_starting It is a little more tricky if the variable contains more than one space in a row: VAR="two spaces between each word" echo test | parallel echo {} \'"$VAR"\' Prints: test two spaces between each word If the variable should not be evaluated by the shell starting GNU parallel but be evaluated by the sub shell started by GNU parallel, then you need to quote it: echo test | parallel VAR=this_is_set_after_starting \; echo {} \$VAR Prints: test this_is_set_after_starting It is a little more tricky if the variable contains space: echo test |\ parallel VAR='"two spaces between each word"' echo {} \'"$VAR"\' Prints: test two spaces between each word $$ is the shell variable containing the process id of the shell. This will print the process id of the shell running GNU parallel: seq 10 | parallel echo $$ And this will print the process ids of the sub shells started by GNU parallel. seq 10 | parallel echo \$\$ If the special characters should not be evaluated by the sub shell then you need to protect it against evaluation from both the shell starting GNU parallel and the sub shell: echo test | parallel echo {} \\\$VAR Prints: test $VAR GNU parallel can protect against evaluation by the sub shell by using -q: echo test | parallel -q echo {} \$VAR Prints: test $VAR This is particularly useful if you have lots of quoting. If you want to run a perl script like this: perl -ne '/^\S+\s+\S+$/ and print $ARGV,"\n"' file It needs to be quoted like one of these: ls | parallel perl -ne '/^\\S+\\s+\\S+\$/\ and\ print\ \$ARGV,\"\\n\"' ls | parallel perl -ne \''/^\S+\s+\S+$/ and print $ARGV,"\n"'\' Notice how spaces, \'s, "'s, and $'s need to be quoted. GNU parallel can do the quoting by using option -q: ls | parallel -q perl -ne '/^\S+\s+\S+$/ and print $ARGV,"\n"' However, this means you cannot make the sub shell interpret special characters. For example because of -q this WILL NOT WORK: ls *.gz | parallel -q "zcat {} >{.}" ls *.gz | parallel -q "zcat {} | bzip2 >{.}.bz2" because > and | need to be interpreted by the sub shell. If you get errors like: sh: -c: line 0: syntax error near unexpected token sh: Syntax error: Unterminated quoted string sh: -c: line 0: unexpected EOF while looking for matching `'' sh: -c: line 1: syntax error: unexpected end of file zsh:1: no matches found: then you might try using -q. If you are using bash process substitution like <(cat foo) then you may try -q and prepending command with bash -c: ls | parallel -q bash -c 'wc -c <(echo {})' Or for substituting output: ls | parallel -q bash -c \ 'tar c {} | tee >(gzip >{}.tar.gz) | bzip2 >{}.tar.bz2' Conclusion: If this is confusing consider avoiding having to deal with quoting by writing a small script or a function (remember to export -f the function) and have GNU parallel call that. LIST RUNNING JOBS If you want a list of the jobs currently running you can run: killall -USR1 parallel GNU parallel will then print the currently running jobs on stderr (standard error). COMPLETE RUNNING JOBS BUT DO NOT START NEW JOBS If you regret starting a lot of jobs you can simply break GNU parallel, but if you want to make sure you do not have half-completed jobs you should send the signal SIGHUP to GNU parallel: killall -HUP parallel This will tell GNU parallel to not start any new jobs, but wait until the currently running jobs are finished before exiting. ENVIRONMENT VARIABLES $PARALLEL_HOME Dir where GNU parallel stores config files, semaphores, and caches information between invocations. If set to a non- existent dir, the dir will be created. Default: $HOME/.parallel. $PARALLEL_ARGHOSTGROUPS When using --hostgroups GNU parallel sets this to the hostgroups of the job. Remember to quote the $, so it gets evaluated by the correct shell. Or use --plus and {agrp}. $PARALLEL_HOSTGROUPS When using --hostgroups GNU parallel sets this to the hostgroups of the sshlogin that the job is run on. Remember to quote the $, so it gets evaluated by the correct shell. Or use --plus and {hgrp}. $PARALLEL_JOBSLOT Set by GNU parallel and can be used in jobs run by GNU parallel. Remember to quote the $, so it gets evaluated by the correct shell. Or use --plus and {slot}. $PARALLEL_JOBSLOT is the jobslot of the job. It is equal to {%} unless the job is being retried. See {%} for details. $PARALLEL_PID Set by GNU parallel and can be used in jobs run by GNU parallel. Remember to quote the $, so it gets evaluated by the correct shell. This makes it possible for the jobs to communicate directly to GNU parallel. Example: If each of the jobs tests a solution and one of jobs finds the solution the job can tell GNU parallel not to start more jobs by: kill -HUP $PARALLEL_PID. This only works on the local computer. $PARALLEL_RSYNC_OPTS Options to pass on to rsync. Defaults to: -rlDzR. $PARALLEL_SHELL Use this shell for the commands run by GNU parallel: • $PARALLEL_SHELL. If undefined use: • The shell that started GNU parallel. If that cannot be determined: • $SHELL. If undefined use: • /bin/sh $PARALLEL_SSH GNU parallel defaults to using the ssh command for remote access. This can be overridden with $PARALLEL_SSH, which again can be overridden with --ssh. It can also be set on a per server basis (see --sshlogin). $PARALLEL_SSHHOST Set by GNU parallel and can be used in jobs run by GNU parallel. Remember to quote the $, so it gets evaluated by the correct shell. Or use --plus and {host}. $PARALLEL_SSHHOST is the host part of an sshlogin line. E.g. 4//usr/bin/specialssh user@host becomes: host $PARALLEL_SSHLOGIN Set by GNU parallel and can be used in jobs run by GNU parallel. Remember to quote the $, so it gets evaluated by the correct shell. Or use --plus and {sshlogin}. The value is the sshlogin line with number of threads removed. E.g. 4//usr/bin/specialssh user@host becomes: /usr/bin/specialssh user@host $PARALLEL_SEQ Set by GNU parallel and can be used in jobs run by GNU parallel. Remember to quote the $, so it gets evaluated by the correct shell. $PARALLEL_SEQ is the sequence number of the job running. Example: seq 10 | parallel -N2 \ echo seq:'$'PARALLEL_SEQ arg1:{1} arg2:{2} {#} is a shorthand for $PARALLEL_SEQ. $PARALLEL_TMUX Path to tmux. If unset the tmux in $PATH is used. $TMPDIR Directory for temporary files. See also: --tmpdir $PARALLEL_REMOTE_TMPDIR Directory for temporary files on remote servers. See also: --tmpdir $PARALLEL The environment variable $PARALLEL will be used as default options for GNU parallel. If the variable contains special shell characters (e.g. $, *, or space) then these need to be to be escaped with \. Example: cat list | parallel -j1 -k -v ls cat list | parallel -j1 -k -v -S"myssh user@server" ls can be written as: cat list | PARALLEL="-kvj1" parallel ls cat list | PARALLEL='-kvj1 -S myssh\ user@server' \ parallel echo Notice the \ after 'myssh' is needed because 'myssh' and 'user@server' must be one argument. See also: --profile DEFAULT PROFILE (CONFIG FILE) The global configuration file /etc/parallel/config, followed by user configuration file ~/.parallel/config (formerly known as .parallelrc) will be read in turn if they exist. Lines starting with '#' will be ignored. The format can follow that of the environment variable $PARALLEL, but it is often easier to simply put each option on its own line. Options on the command line take precedence, followed by the environment variable $PARALLEL, user configuration file ~/.parallel/config, and finally the global configuration file /etc/parallel/config. Note that no file that is read for options, nor the environment variable $PARALLEL, may contain retired options such as --tollef. PROFILE FILES If --profile set, GNU parallel will read the profile from that file rather than the global or user configuration files. You can have multiple --profiles. Profiles are searched for in ~/.parallel. If the name starts with / it is seen as an absolute path. If the name starts with ./ it is seen as a relative path from current dir. Example: Profile for running a command on every sshlogin in ~/.ssh/sshlogins and prepend the output with the sshlogin: echo --tag -S .. --nonall > ~/.parallel/nonall_profile parallel -J nonall_profile uptime Example: Profile for running every command with -j-1 and nice echo -j-1 nice > ~/.parallel/nice_profile parallel -J nice_profile bzip2 -9 ::: * Example: Profile for running a perl script before every command: echo "perl -e '\$a=\$\$; print \$a,\" \",'\$PARALLEL_SEQ',\" \";';" \ > ~/.parallel/pre_perl parallel -J pre_perl echo ::: * Note how the $ and " need to be quoted using \. Example: Profile for running distributed jobs with nice on the remote computers: echo -S .. nice > ~/.parallel/dist parallel -J dist --trc {.}.bz2 bzip2 -9 ::: * EXIT STATUS Exit status depends on --halt-on-error if one of these is used: success=X, success=Y%, fail=Y%. 0 All jobs ran without error. If success=X is used: X jobs ran without error. If success=Y% is used: Y% of the jobs ran without error. 1-100 Some of the jobs failed. The exit status gives the number of failed jobs. If Y% is used the exit status is the percentage of jobs that failed. 101 More than 100 jobs failed. 255 Other error. -1 (In joblog and SQL table) Killed by Ctrl-C, timeout, not enough memory or similar. -2 (In joblog and SQL table) skip() was called in {= =}. -1000 (In SQL table) Job is ready to run (set by --sqlmaster). -1220 (In SQL table) Job is taken by worker (set by --sqlworker). If fail=1 is used, the exit status will be the exit status of the failing job. DIFFERENCES BETWEEN GNU Parallel AND ALTERNATIVES See: man parallel_alternatives BUGS Quoting of newline Because of the way newline is quoted this will not work: echo 1,2,3 | parallel -vkd, "echo 'a{}b'" However, these will all work: echo 1,2,3 | parallel -vkd, echo a{}b echo 1,2,3 | parallel -vkd, "echo 'a'{}'b'" echo 1,2,3 | parallel -vkd, "echo 'a'"{}"'b'" Speed Startup GNU parallel is slow at starting up - around 250 ms the first time and 150 ms after that. Job startup Starting a job on the local machine takes around 3-10 ms. This can be a big overhead if the job takes very few ms to run. Often you can group small jobs together using -X which will make the overhead less significant. Or you can run multiple GNU parallels as described in EXAMPLE: Speeding up fast jobs. SSH When using multiple computers GNU parallel opens ssh connections to them to figure out how many connections can be used reliably simultaneously (Namely SSHD's MaxStartups). This test is done for each host in serial, so if your --sshloginfile contains many hosts it may be slow. If your jobs are short you may see that there are fewer jobs running on the remote systems than expected. This is due to time spent logging in and out. -M may help here. Disk access A single disk can normally read data faster if it reads one file at a time instead of reading a lot of files in parallel, as this will avoid disk seeks. However, newer disk systems with multiple drives can read faster if reading from multiple files in parallel. If the jobs are of the form read-all-compute-all-write-all, so everything is read before anything is written, it may be faster to force only one disk access at the time: sem --id diskio cat file | compute | sem --id diskio cat > file If the jobs are of the form read-compute-write, so writing starts before all reading is done, it may be faster to force only one reader and writer at the time: sem --id read cat file | compute | sem --id write cat > file If the jobs are of the form read-compute-read-compute, it may be faster to run more jobs in parallel than the system has CPUs, as some of the jobs will be stuck waiting for disk access. --nice limits command length The current implementation of --nice is too pessimistic in the max allowed command length. It only uses a little more than half of what it could. This affects -X and -m. If this becomes a real problem for you, file a bug-report. Aliases and functions do not work If you get: Can't exec "command": No such file or directory or: open3: exec of by command failed or: /bin/bash: command: command not found it may be because command is not known, but it could also be because command is an alias or a function. If it is a function you need to export -f the function first or use env_parallel. An alias will only work if you use env_parallel. Database with MySQL fails randomly The --sql* options may fail randomly with MySQL. This problem does not exist with PostgreSQL. REPORTING BUGS Report bugs to <parallel@gnu.org> or https://savannah.gnu.org/bugs/?func=additem&group=parallel When you write your report, please keep in mind, that you must give the reader enough information to be able to run exactly what you run. So you need to include all data and programs that you use to show the problem. See a perfect bug report on https://lists.gnu.org/archive/html/bug-parallel/2015-01/msg00000.html Your bug report should always include: • The error message you get (if any). If the error message is not from GNU parallel you need to show why you think GNU parallel caused this. • The complete output of parallel --version. If you are not running the latest released version (see https://ftp.gnu.org/gnu/parallel/) you should specify why you believe the problem is not fixed in that version. • A minimal, complete, and verifiable example (See description on https://stackoverflow.com/help/mcve). It should be a complete example that others can run which shows the problem including all files needed to run the example. This should preferably be small and simple, so try to remove as many options as possible. A combination of yes, seq, cat, echo, wc, and sleep can reproduce most errors. If your example requires large files, see if you can make them with something like seq 100000000 > bigfile or yes | head -n 1000000000 > file. If you need multiple columns: paste <(seq 1000) <(seq 1000 1999) If your example requires remote execution, see if you can use localhost - maybe using another login. If you have access to a different system (maybe a VirtualBox on your own machine), test if your MCVE shows the problem on that system. If it does not, read below. • The output of your example. If your problem is not easily reproduced by others, the output might help them figure out the problem. • Whether you have watched the intro videos (https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1), walked through the tutorial (man parallel_tutorial), and read the examples (man parallel_examples). Bug dependent on environment If you suspect the error is dependent on your environment or distribution, please see if you can reproduce the error on one of these VirtualBox images: https://sourceforge.net/projects/virtualboximage/files/ https://www.osboxes.org/virtualbox-images/ Specifying the name of your distribution is not enough as you may have installed software that is not in the VirtualBox images. If you cannot reproduce the error on any of the VirtualBox images above, see if you can build a VirtualBox image on which you can reproduce the error. If not you should assume the debugging will be done through you. That will put a lot more burden on you and it is extra important you give any information that help. In general the problem will be fixed faster and with much less work for you if you can reproduce the error on a VirtualBox - even if you have to build a VirtualBox image. In summary Your report must include: • parallel --version • output + error message • full example including all files • VirtualBox image, if you cannot reproduce it on other systems AUTHOR When using GNU parallel for a publication please cite: O. Tange (2011): GNU Parallel - The Command-Line Power Tool, ;login: The USENIX Magazine, February 2011:42-47. This helps funding further development; and it won't cost you a cent. If you pay 10000 EUR you should feel free to use GNU Parallel without citing. Copyright (C) 2007-10-18 Ole Tange, http://ole.tange.dk Copyright (C) 2008-2010 Ole Tange, http://ole.tange.dk Copyright (C) 2010-2024 Ole Tange, http://ole.tange.dk and Free Software Foundation, Inc. Parts of the manual concerning xargs compatibility is inspired by the manual of xargs from GNU findutils 4.4.2. LICENSE This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or at your option any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <https://www.gnu.org/licenses/>. Documentation license I Permission is granted to copy, distribute and/or modify this documentation under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the file LICENSES/GFDL-1.3-or-later.txt. Documentation license II You are free: to Share to copy, distribute and transmit the work to Remix to adapt the work Under the following conditions: Attribution You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work). Share Alike If you alter, transform, or build upon this work, you may distribute the resulting work only under the same, similar or a compatible license. With the understanding that: Waiver Any of the above conditions can be waived if you get permission from the copyright holder. Public Domain Where the work or any of its elements is in the public domain under applicable law, that status is in no way affected by the license. Other Rights In no way are any of the following rights affected by the license: • Your fair dealing or fair use rights, or other applicable copyright exceptions and limitations; • The author's moral rights; • Rights other persons may have either in the work itself or in how the work is used, such as publicity or privacy rights. Notice For any reuse or distribution, you must make clear to others the license terms of this work. A copy of the full license is included in the file as LICENCES/CC-BY-SA-4.0.txt DEPENDENCIES GNU parallel uses Perl, and the Perl modules Getopt::Long, IPC::Open3, Symbol, IO::File, POSIX, and File::Temp. For --csv it uses the Perl module Text::CSV. For remote usage it uses rsync with ssh. SEE ALSO parallel_tutorial(1), env_parallel(1), parset(1), parsort(1), parallel_alternatives(1), parallel_design(7), niceload(1), sql(1), ssh(1), ssh-agent(1), sshpass(1), ssh-copy-id(1), rsync(1) 20240622 2024-07-21 PARALLEL(1)
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luac5.4
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idle3.10
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