Hi, 2011/11/7 Måns Rullgård <[email protected]>: > "Ronald S. Bultje" <[email protected]> writes: > >> 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. :-). > > It's calling some generated code. So what? Use a function pointer.
Ugliest version of emulating pmaddubsw ever? That's essentially what it is... But fine, calling in C should work. Ronald _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
