[FFmpeg-trac] #11156(avdevice:new): libavdevice fails to compile on Linux (musl libc)

[FFmpeg]

#11156: libavdevice fails to compile on Linux (musl libc)
----------------------------------+--------------------------------------
             Reporter:  2246c68   |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  avdevice  |                  Version:  git-master
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
----------------------------------+--------------------------------------
 Summary of the bug:

 libavdevice fails to build on Linux (musl libc).

 How to reproduce:
 {{{
 % ../configure \
     --cross-prefix="aarch64-unknown-linux-musl-" \
     --target-os="linux" \
     --arch="aarch64" \
     --disable-alsa \
     --disable-appkit \
     --disable-asm \
     --disable-audiotoolbox \
     --disable-avfoundation \
     --disable-bzlib \
     --disable-coreimage \
     --disable-debug \
     --disable-doc \
     --disable-iconv \
     --disable-libxcb \
     --disable-lzma \
     --disable-neon \
     --disable-schannel \
     --disable-sdl2 \
     --disable-securetransport \
     --disable-static \
     --disable-symver \
     --disable-videotoolbox \
     --disable-vulkan \
     --disable-xlib \
     --disable-zlib \
     --disable-manpages \
     --disable-htmlpages \
     --disable-podpages \
     --disable-txtpages \
     --enable-pic \
     --enable-shared \
     --enable-small \
     --enable-version3
 % make
 src/libavdevice/v4l2.c: In function 'device_open':
 src/libavdevice/v4l2.c:137:17: error: assignment to 'int (*)(int,  long
 unsigned int, ...)' from incompatible pointer type 'int (*)(int,  int,
 ...)' [-Wincompatible-pointer-types]
   137 |     s->ioctl_f  = prefix ## ioctl;      \
       |                 ^
 src/libavdevice/v4l2.c:151:9: note: in expansion of macro 'SET_WRAPPERS'
   151 |         SET_WRAPPERS();
       |         ^~~~~~~~~~~~
 }}}

 git bisect points to 9e674b31606c805dd31b4bb754364a72a5877238 as the
 culprit.

 There is one main issue with the changes implemented in that commit,
 specifically the use of the `__musl__` macro to write musl-specific code:

 {{{
 ...
 #if defined(__sun) || defined(__BIONIC__) || defined(__musl__) /* POSIX-
 like */
 ...
 }}}

 It should be noted that musl does not currently provide any way to detect
 itself (see https://wiki.musl-libc.org/faq). That is, neither the
 `__musl__` nor `__MUSL__` macros exists. The `#if defined(__musl__)`
 condition will always evaluate to false, even on musl platforms, leading
 FFmpeg to use the wrong prototype.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11156>
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