Hi, 2011/11/7 Måns Rullgård <[email protected]>: > Reinhard Tartler <[email protected]> writes: > >> tags 647824 upstream >> stop >> >> On So, Nov 06, 2011 at 17:53:30 (CET), Harald Dunkel wrote: >> >>> Package: libav >>> Version: 4:0.7.2-1 >>> >>> If I build the current xbmc snapshot, then it dies at runtime when >>> creating thumbnails for wmv files. See http://trac.xbmc.org/ticket/11789 >>> for more details >>> >>> http://article.gmane.org/gmane.comp.video.ffmpeg.devel/134444 >>> >>> provides a workaround. Do you think this could be included in the >>> libav and libav-extra packages? >>> >> >> That patch does not apply to Debian's libav package. In fact, it seems >> that this bug is still present in the master branch. >> >> I was able to reproduce the segmentation fault using the following >> command in libav *master* (inspired by >> https://ffmpeg.org/trac/ffmpeg/ticket/397): >> >> ./ffmpeg -v 9 -loglevel 99 -i >> /srv/scratch/fate-suite/amv/MTV_high_res_320x240_sample_Penguin_Joke_MTV_from_WMV.amv >> -sws_flags fast_bilinear -vf "scale=640:480" -vframes 1 -vcodec png >> output.png >> >> Unforutnately, this (adapted) patch does not seem to fix the >> segmentation fault: >> >> diff --git a/libswscale/x86/swscale_template.c >> b/libswscale/x86/swscale_template.c >> index 5e7df5c..51ea303 100644 >> --- a/libswscale/x86/swscale_template.c >> +++ b/libswscale/x86/swscale_template.c >> @@ -1657,6 +1657,11 @@ static void RENAME(hyscale_fast)(SwsContext *c, >> int16_t *dst, >> DECLARE_ALIGNED(8, uint64_t, ebxsave); >> #endif >> >> + // HACK: gcc 4.6 no longer decrements esp, >> + // use this to make it reserve space for the call >> + // return address >> + void *dummy; > > The real problem here comes from hiding a call inside inline asm. On > x86_64 leaf functions have a "red zone" of 128 bytes below the stack > pointer which can be used for whatever the compiler feels like. If the > compiler has made use of this (gcc frequently does) and a call is > injected with inline asm, any values kept in the red zone are destroyed. > > There are 3 solutions to this problem: > > 1. Do the calls in C. > 2. Convert the function to yasm. > 3. Manually protect the red zone in the inline asm. > > Option 3 is difficult to do if any asm parameters might reference the > stack as is the case here. > > Why is this using asm at all? It's only a few function calls.
You should check what it's calling. :-). Ronald _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
