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.