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| <html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>Chapter 4. Programming with Cygwin</title><link rel="stylesheet" type="text/css" href="docbook.css"><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot"><link rel="home" href="cygwin-ug-net.html" title="Cygwin User's Guide"><link rel="up" href="cygwin-ug-net.html" title="Cygwin User's Guide"><link rel="prev" href="using-effectively.html" title="Using Cygwin effectively with Windows"><link rel="next" href="gdb.html" title="Debugging Cygwin Programs"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 4. Programming with Cygwin</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="using-effectively.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="gdb.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="programming"></a>Chapter 4. Programming with Cygwin</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="sect1"><a href="programming.html#gcc">Using GCC with Cygwin</a></span></dt><dd><dl><dt><span class="sect2"><a href="programming.html#gcc-default">Standard Usage</a></span></dt><dt><span class="sect2"><a href="programming.html#gcc-64">Building applications for 64 bit Cygwin</a></span></dt><dt><span class="sect2"><a href="programming.html#gcc-gui">GUI Mode Applications</a></span></dt></dl></dd><dt><span class="sect1"><a href="gdb.html">Debugging Cygwin Programs</a></span></dt><dt><span class="sect1"><a href="dll.html">Building and Using DLLs</a></span></dt><dd><dl><dt><span class="sect2"><a href="dll.html#dll-build">Building DLLs</a></span></dt><dt><span class="sect2"><a href="dll.html#dll-link">Linking Against DLLs</a></span></dt></dl></dd><dt><span class="sect1"><a href="windres.html">Defining Windows Resources</a></span></dt><dt><span class="sect1"><a href="gprof.html">Profiling Cygwin Programs</a></span></dt><dd><dl><dt><span class="sect2"><a href="gprof.html#gprof-intro">Introduction</a></span></dt><dt><span class="sect2"><a href="gprof.html#gprof-ex">Examples</a></span></dt><dt><span class="sect2"><a href="gprof.html#gprof-ss">Special situations</a></span></dt><dd><dl><dt><span class="sect3"><a href="gprof.html#gprof-mt">Profiling multi-threaded programs</a></span></dt><dt><span class="sect3"><a href="gprof.html#gprof-fork">Profiling programs that fork</a></span></dt><dt><span class="sect3"><a href="gprof.html#gprof-res">Getting better profiling resolution</a></span></dt><dt><span class="sect3"><a href="gprof.html#gprof-lib">Profiling programs with their libraries</a></span></dt><dt><span class="sect3"><a href="gprof.html#gprof-cyg">Profiling Cygwin itself</a></span></dt></dl></dd></dl></dd></dl></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="gcc"></a>Using GCC with Cygwin</h2></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="gcc-default"></a>Standard Usage</h3></div></div></div><p>Use gcc to compile, just like under UNIX. Refer to the GCC User's Guide |
| for information on standard usage and options. Here's a simple example:</p><div class="example"><a name="gcc-hello-world"></a><p class="title"><b>Example 4.1. Building Hello World with GCC</b></p><div class="example-contents"><pre class="screen"> |
| <code class="prompt">bash$</code> <strong class="userinput"><code>gcc hello.c -o hello.exe</code></strong> |
| <code class="prompt">bash$</code> <strong class="userinput"><code>hello.exe</code></strong> |
| Hello, World |
|
|
| <code class="prompt">bash$</code> |
| </pre></div></div><br class="example-break"></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="gcc-64"></a>Building applications for 64 bit Cygwin</h3></div></div></div><p>The 64 bit Cygwin toolchain uses the |
| <a class="ulink" href="http://en.wikipedia.org/wiki/X86_calling_convention#Microsoft_x64_calling_convention" target="_top">Microsoft x64 calling convention</a> |
| by default, so you can create applications using the Win32 API just as with |
| the 32 bit Cygwin toolchain.</p><p>There's just one important difference. The 64 bit Cygwin compilers use |
| a different data model than the Mingw and Microsoft compilers. For reference, |
| see the Wikipedia entry on |
| <a class="ulink" href="http://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models" target="_top">64-bit computing</a>.</p><p>While the Mingw and Microsoft compilers use the <code class="literal">LLP64</code> |
| data model, Cygwin compilers use the <code class="literal">LP64</code> data model, just |
| like Linux. This affects the size of the type <code class="literal">long</code>. In the |
| <code class="literal">LLP64</code> model preferred by Microsoft, |
| <code class="function">sizeof(long)</code> is 4. This applies for the related Win32 |
| types like <code class="literal">LONG</code>, <code class="literal">ULONG</code>, |
| <code class="literal">DWORD</code>, etc., too.</p><p>In the <code class="literal">LP64</code> model used by Cygwin, <code class="function">sizeof(long)</code> is 8, |
| just like the size of pointers or the types <code class="literal">size_t/ssize_t</code>. |
| This simplifies porting Linux applications to 64 bit Cygwin, but it requires |
| due diligence when calling Windows functions taking LONG, ULONG, DWORD, or any |
| other equivalent type. This is especially important in conjunction with |
| pointers.</p><p>Here's an example. The Win32 function <code class="function">ReadFile</code> |
| returns the number of read bytes via a pointer to a DWORD variable:</p><pre class="screen"> |
| BOOL WINAPI ReadFile (HANDLE, PVOID, DWORD, PDWORD, LPOVERLAPPED); |
| </pre><p>Note that the forth parameter is a pointer to a DWORD, thus it's a |
| pointer to a 4 byte type, on 32 as well as on 64 bit Windows. Now we write |
| our own <code class="function">my_read</code> function using ReadFile:</p><div class="example"><a name="gcc-64-ex1"></a><p class="title"><b>Example 4.2. 64bit-programming, Using ReadFile, 1st try</b></p><div class="example-contents"><pre class="screen"> |
| ssize_t |
| my_read (int fd, void *buffer, size_t bytes_to_read) |
| { |
| HANDLE fh = _get_osfhandle (fd); |
| ssize_t bytes_read; |
|
|
| if (ReadFile (fh, buffer, bytes_to_read, (PDWORD) &bytes_read, NULL)) |
| return bytes_read; |
| set_errno_from_get_last_error (); |
| return -1; |
| } |
| </pre></div></div><br class="example-break"><p>While this example code works fine on 32 bit Windows, it has in fact |
| a bad bug. The assumption that the size of ssize_t is the same as the size |
| of DWORD is wrong for 64 bit. In fact, since |
| <code class="function">sizeof(ssize_t)</code> is 8, <code class="function">ReadFile</code> |
| will write the number of read bytes into the lower 4 bytes of the variable |
| <code class="literal">bytes_read</code>, while the upper 4 bytes will contain an |
| undefined value. <code class="function">my_read</code> will very likely return the |
| wrong number of read bytes to the caller.</p><p>Here's the fixed version of <code class="function">my_read</code>:</p><div class="example"><a name="gcc-64-ex2"></a><p class="title"><b>Example 4.3. 64bit-programming, Using ReadFile, 2nd try</b></p><div class="example-contents"><pre class="screen"> |
| ssize_t |
| my_read (int fd, void *buffer, size_t bytes_to_read) |
| { |
| HANDLE fh = _get_osfhandle (fd); |
| DWORD bytes_read; |
|
|
| if (ReadFile (fh, buffer, bytes_to_read, &bytes_read, NULL)) |
| return (ssize_t) bytes_read; |
| set_errno_from_get_last_error (); |
| return -1; |
| } |
| </pre></div></div><br class="example-break"></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="gcc-gui"></a>GUI Mode Applications</h3></div></div></div><p>Cygwin comes with an X server, so usually you should compile your |
| GUI applications as X applications to allow better interoperability with |
| other Cygwin GUI applications.</p><p>Other than that, Cygwin allows you to build programs with full access |
| to the standard Windows API, including the GUI functions as defined in |
| any Microsoft or off-the-shelf publication.</p><p>The build process is similar to any other build process. The only |
| difference is that you use <span class="command"><strong>gcc -mwindows</strong></span> to link your |
| program into a GUI application instead of a command-line application. |
| Here's an example Makefile:</p><pre class="screen"> |
|
|
| myapp.exe : myapp.o myapp.res |
| gcc -mwindows myapp.o myapp.res -o $@ |
|
|
| myapp.res : myapp.rc resource.h |
| windres $< -O coff -o $@ |
|
|
| </pre><p>Note the use of <code class="filename">windres</code> to compile the |
| Windows resources into a COFF-format <code class="filename">.res</code> file. |
| That will include all the bitmaps, icons, and other resources you |
| need, into one handy object file. For more information on |
| <code class="filename">windres</code>, consult the Binutils manual. </p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="using-effectively.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="gdb.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Using Cygwin effectively with Windows </td><td width="20%" align="center"><a accesskey="h" href="cygwin-ug-net.html">Home</a></td><td width="40%" align="right" valign="top"> Debugging Cygwin Programs</td></tr></table></div></body></html> |
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