| This folder contains the musl version of libc at `/musl`. The upstream version |
| can be found at http://www.musl-libc.org/. |
|
|
| Most of the source comes from musl v1.2.5, with some exceptions listed below. |
| We track these changes from upstream in https://github.com/emscripten-core/musl |
| and use a script (`system/lib/update_musl.py`) to pull in updates. |
|
|
| Some changes have been made to the version that was taken from upstream, including: |
|
|
| * Emscripten-specific changes (from before this readme existed). These should be marked with `XXX EMSCRIPTEN` in the source, or ifdefed with `#if __EMSCRIPTEN__`. They are mostly in pthreads code and hopefully temporary. |
| * Backporting an operator-precedence warning fix from 6e76e1540fc58a418494bf5eb832b556f9c5763e in the upstream version. |
| * Switch to using the wasi `fd_write` syscall instead of `writev`. |
| * Simplify stdout stream handling: do not support seeking, terminal handling, etc., as it just increases code size and Emscripten doesn't have those features anyhow. |
| * Setting `_POSIX_REALTIME_SIGNALS` and `_POSIX_SPAWN` macros to -1, to exclude unsupported functions. |
| * Handling trailing % in `strftime` and `wcsftime` format strings. |
|
|
| Copy log.c and log2.c from earlier version of musl which result in smaller |
| binary size since they do not rely on data tables in log_data.c and log2_data.c. |
| See https://github.com/emscripten-core/emscripten/issues/15483. |
|
|
| Verifying upstream musl behaviour |
| ================================= |
|
|
| Occasionally when working on libc/musl it can be useful to verify to behavior |
| of upstream musl. For example, when trying to determine if a certain behavior |
| is a bug in emscripten, or an upstream bug, or just expected musl behavior. |
|
|
| When I need to do this I use the Alpine linux docker image. Alpine linux is a |
| distro where the sysmtem libc is musl so by default any program you build within |
| the contains will be using musl libc. |
|
|
| $ docker run --rm -it -v "$(pwd):/data" alpine /bin/sh |
| |
| Then from inside the new container you can run tests against Alpine's musl libc. |
| For example: |
|
|
| $ apk add build-base |
| $ cd /data |
| $ gcc -pthread test/pthread/test_pthread_cancel_async.c |
| $ ./a.out |
| |
