[FFmpeg-trac] #2755(avcodec:new): avformat_find_stream_info crashes float register

[FFmpeg]

#2755: avformat_find_stream_info crashes float register
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             Reporter:  hxuanyu  |                     Type:  defect
               Status:  new      |                 Priority:  normal
            Component:  avcodec  |                  Version:  unspecified
             Keywords:           |               Blocked By:
             Blocking:           |  Reproduced by developer:  0
Analyzed by developer:  0        |
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 This issue is only reproduce-able on Mac version, it's reproduce-able on
 1.2.x, 1.1.x and 1.0.x branches. it works fine on 0.11.x branches.

 We found this issue in our own app which uses ffmpeg libraries.
 after avformat_find_stream_info is called, long double calculation get
 some wired result.

 We used 'info float' in gdb and found that float register are filled with
 weird value after avformat_find_stream_info is called. I'll attach dbg
 screen shot for you.

 I also wrote a code fragment and put it into main of ffmpeg.c,
 and the executable build on Mac can reproduce the issue.

 testers said it happens every time when input video format is MPEG4

 the configuration used to build on Mac is :  --enable-cross-compile
 --arch=i386 --target-os=darwin --cc=gcc-4.0 --extra-cflags='-arch i386
 -mmacosx-version-min=10.2 -isysroot /Developer/SDKs/MacOSX10.4u.sdk'
 --extra-ldflags='-arch i386 -mmacosx-version-min=10.2 -isysroot
 /Developer/SDKs/MacOSX10.4u.sdk' \ --disable-mmx

 the tested video will be attached, you can test it on 1.1.5 or 1.2.1
 branches

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2755>
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