FFmpeg not buildable without pthreads?

[Jozef Chutka]

When configuring ffmpeg (2 days old master version 5661c87) with emscripten with flags --disable-pthreads --disable-w32threads --disable-os2threads:

emconfigure ./configure --target-os=none --arch=x86_32 --enable-cross-compile --enable-version3
  --enable-zlib --enable-libopenh264...
  --disable-x86asm --disable-inline-asm --disable-stripping
  --disable-programs --disable-doc --disable-debug --disable-runtime-cpudetect
  --disable-autodetect
  --extra-cflags="-O3 -msimd128"
  --extra-cxxflags="-O3 -msimd128"
  --extra-ldflags="-O3 -msimd128"
  --pkg-config-flags="--static"
  --nm="llvm-nm" --ar=emar --ranlib=emranlib --cc=emcc --cxx=em++ --objcc=emcc --dep-cc=emcc
  --disable-pthreads --disable-w32threads --disable-os2threads

emmake make -j

emcc -O3 -msimd128 -I. -I./fftools -I$BUILD_DIR/include
  -Llibavcodec -Llibavdevice ... -L$BUILD_DIR/lib
  -Wno-deprecated-declarations -Wno-pointer-sign -Wno-implicit-int-float-conversion -Wno-switch -Wno-parentheses -Qunused-arguments
  -lavdevice -lavfilter -lavformat -lavcodec -lswresample -lswscale -lavutil -lm ...
  fftools/cmdutils.c fftools/ffmpeg.c fftools/ffmpeg_demux.c fftools/ffmpeg_filter.c fftools/ffmpeg_hw.c fftools/ffmpeg_mux.c fftools/ffmpeg_mux_init.c fftools/ffmpeg_opt.c fftools/objpool.c fftools/opt_common.c fftools/sync_queue.c fftools/thread_queue.c
  -lworkerfs.js -s USE_SDL=2 -s INVOKE_RUN=0 -s EXIT_RUNTIME=1 -s MODULARIZE=1
  -s EXPORT_NAME="createFFmpeg" -s EXPORTED_FUNCTIONS="[_main]" -s EXPORTED_RUNTIME_METHODS="[callMain, FS, WORKERFS]" -s INITIAL_MEMORY=128mb -s ENVIRONMENT=worker -o ffmpeg.js

Configure runs ok, however the following command fails with some phtread related errors:

fftools/ffmpeg_demux.c:358:5: error: call to undeclared function 'pthread_join'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    pthread_join(d->thread, NULL);
    ^
fftools/ffmpeg_demux.c:358:5: note: did you mean 'pthread_kill'?
/ffmpeg/modules/emsdk/upstream/emscripten/cache/sysroot/include/signal.h:226:5: note: 'pthread_kill' declared here
int pthread_kill(pthread_t, int);
    ^
fftools/ffmpeg_demux.c:397:16: error: call to undeclared function 'pthread_create'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    if ((ret = pthread_create(&d->thread, NULL, input_thread, d))) {
               ^
2 errors generated.
emcc: error: '/ffmpeg/modules/emsdk/upstream/bin/clang -target wasm32-unknown-emscripten -fignore-exceptions -fvisibility=default -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -DEMSCRIPTEN -Werror=implicit-function-declaration -I/ffmpeg/modules/emsdk/upstream/emscripten/cache/sysroot/include/SDL2 --sysroot=/ffmpeg/modules/emsdk/upstream/emscripten/cache/sysroot -Xclang -iwithsysroot/include/compat -O3 -I/ffmpeg/build/include -msimd128 -I. -I./fftools -I/ffmpeg/build/include -Wno-deprecated-declarations -Wno-pointer-sign -Wno-implicit-int-float-conversion -Wno-switch -Wno-parentheses -Qunused-arguments fftools/ffmpeg_demux.c -c -o /tmp/emscripten_temp_0b3ma1cz/ffmpeg_demux_2.o' failed (returned 1)
root@cs-1036883351707-default:/ffmpeg# 

I can build a version with pthreads by removing --disable-*threads flags from emconfigure and adding -pthread -s PROXY_TO_PTHREAD=1 -s USE_PTHREADS=1 into emcc.

I tried various flags but could not get building single thread version. As I only have setup for emscripten build, I can not confirm if some more standard single thread build works or not. But having references to pthread_create() or pthread_join() in ffmpeg_demux.c seems suspicious.

Can you please verify if single thread ffmpeg version is still buildable, and if so, do you have any idea what I am doing wrong?

[mkver]

Actually, FFmpeg (the cli tool, not the libraries) depends upons threading since commit 760ce4bc0bd11f74f0851c0a662dd5cae888df83. It seems to me you manually tried to compile the fftools after having run configure with --disable-programs. This is not supported and I am therefore closing this as invalid. Reopen if I am wrong about this.

[Jozef Chutka]

My setup is working for cli tool with emscripten inspired by ​https://github.com/ffmpegwasm/ffmpeg.wasm-core/blob/n4.3.1-wasm/wasm/build-scripts/configure-ffmpeg.sh and ​https://github.com/ffmpegwasm/ffmpeg.wasm-core/blob/n4.3.1-wasm/wasm/build-scripts/build-ffmpeg.sh ...

Are there arguments to be changed to follow the supported path?

I understand threading is out of the quesstion now.