On Tue, Oct 13, 2015 at 11:56 AM, Christophe Gisquet <[email protected]> wrote: > Hi > > 2015-10-06 12:41 GMT+02:00 Hendrik Leppkes <[email protected]>: >> +static av_unused int pthread_once(pthread_once_t *once_control, void >> (*init_routine)(void)) > [...] >> + MemoryBarrier(); > > This resolves to _mm_mfence() which results (see configuration below) > in an undefined symbol (paths redacted): > ffmpeg/compat/w32pthreads.h:202: undefined reference to `_mm_mfence' > libavformat/libavformat.a(async.o): In function `w32thread_once_fallback': > ffmpeg/compat/w32pthreads.h:202: undefined reference to `_mm_mfence' > libavcodec/libavcodec.a(pthread_frame.o): In function > `w32thread_once_fallback': > ffmpeg/compat/w32pthreads.h:202: undefined reference to `_mm_mfence' > libavcodec/libavcodec.a(pthread_slice.o): In function > `w32thread_once_fallback': > ffmpeg/compat/w32pthreads.h:202: undefined reference to `_mm_mfence' > ffmpeg/compat/w32pthreads.h:202: undefined reference to `_mm_mfence' > libavcodec/libavcodec.a(vp8.o):ffmpeg/compat/w32pthreads.h:202: more > undefined references to `_mm_mfence' follow > > Configuration: > In a MSYS2 Mingw32 shell > gcc version 5.2.0 (Rev4, Built by MSYS2 project), target: x86_64-w64-mingw32 > Exact configure line: > ../configure --disable-ffplay --disable-ffprobe --disable-ffserver \ > --disable-hwaccels --disable-dxva2 \ > --extra-cflags="-msse4.2" --cc="ccache gcc" > > The above command-line is fine for the equivalent Win64 configuration. > Removing --extra-cflags fixes the issue. Adding -msse2 to it causes > the same compilation error. > > MSVC has platform-specific implementations of MemoryBarrier() which > may resolve to the SSE2 mfence instruction. I'm not sure if > --extra-cflags="-msse4.2" cannot be expected to always work, or if > there's another issue here. >
Why would adding -msse4.2 hide the symbol? Sounds like you should complain to mingw. In the meantime we could add an ugly ifdef for mingw/gcc and use __sync_synchronize there instead (the gcc built-in) - Hendrik _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
