[FFmpeg-trac] #7788(avcodec:new): Custom-compiled FFmpeg 4.1.1 crashes on MacOS when reading files

[FFmpeg]

#7788: Custom-compiled FFmpeg 4.1.1 crashes on MacOS when reading files
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             Reporter:  Jim_ChamSys  |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avcodec
              Version:  4.1          |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by jamrial):

 >I compiled with --enable-debug=gdb and --disable-optimizations (on top of
 the previously used flags), and the crash wouldn't happen

 >rbx = 0x000000010302e8c8
 >->  0x1009dbd72 <+134>: movdqa %xmm0, (%rbx)

 Looks like a compiler bug. The code it generates results in unaligned
 memory access when using movdqa, something that doesn't happen when you
 compile with --disable-optimizations as it removes -O3 and similar
 compiler optimization flags.

 Is this the same compiler you used for ffmpeg 3.4.2, which you say worked?
 It's evidently ignoring the -fno-tree-vectorize flag we use precisely to
 prevent compilers from making mistakes like this.

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Ticket URL: <https://trac.ffmpeg.org/ticket/7788#comment:4>
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