[FFmpeg-trac] #9458(ffmpeg:new): ffmpeg's outputs differ a lot when compiled with gcc and clang

[FFmpeg]

#9458: ffmpeg's outputs differ a lot when compiled with gcc and clang
------------------------------------+--------------------------------------
             Reporter:  Shaohua Li  |                     Type:  defect
               Status:  new         |                 Priority:  normal
            Component:  ffmpeg      |                  Version:  git-master
             Keywords:              |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
------------------------------------+--------------------------------------
 Summary of the bug:  For some reasons, I compiled ffmpeg with gcc11 and
 clang13. For some inputs, I found that these two ffmpeg binaries would
 emit outputs that '''differ a lot'''.

 Compile args: ./configure

 Compiler: gcc11 and clang13

 How to reproduce: (run the following command with two ffmpeg compiled with
 different compiler, then compare the size of the outputs. I used `-threads
 1` to avoid possible threading issue.)
 {{{
 % ffmpeg -threads 1 -y -i  input_diff_1  -f mp4 output
 ffmpeg version N-104353-g2c734a8496 Copyright (c) 2000-2021 the FFmpeg
 developers
   built with Ubuntu clang version
 13.0.1-++20211015123032+cf15ccdeb6d5-1~exp1~20211015003613.5
   configuration: --cc=/usr/bin/clang13 --cxx=/usr/bin/clang++-13
 --ld='/usr/bin/clang++-13 -fno-sanitize=vptr -fno-sanitize=vptr -fno-
 sanitize=vptr -std=c++11' --extra-
 cflags=-I/ffmpeg/repo/clang13-O1/ffmpeg_deps/include --extra-
 ldflags=-L/ffmpeg/repo/clang13-O1/ffmpeg_deps/lib
 --prefix=/ffmpeg/repo/clang13-O1/ffmpeg_deps --pkg-config-flags=--static
 --optflags=-O1 --enable-gpl --enable-libass --enable-libfdk-aac --enable-
 libfreetype --enable-libopus --enable-libtheora --enable-libvorbis
 --enable-nonfree --disable-shared
   libavutil      57.  7.100 / 57.  7.100
   libavcodec     59. 12.100 / 59. 12.100
   libavformat    59.  6.100 / 59.  6.100
   libavdevice    59.  0.101 / 59.  0.101
   libavfilter     8. 14.100 /  8. 14.100
   libswscale      6.  1.100 /  6.  1.100
   libswresample   4.  0.100 /  4.  0.100
   libpostproc    56.  0.100 / 56.  0.100
 [avi @ 0x3091f40] Something went wrong during header parsing, tag
 [24][229]q[0] has size 3220715849, I will ignore it and try to continue
 anyway.
 Input #0, avi, from 'bugs/diff_1':
   Duration: 00:00:01.67, start: 0.000000, bitrate: 528 kb/s
   Stream #0:0: Video: rawvideo, pal8, 352x240, 29.97 fps, 29.97 tbr, 29.97
 tbn
 Stream mapping:
   Stream #0:0 -> #0:0 (rawvideo (native) -> mpeg4 (native))
 Press [q] to stop, [?] for help
 [mpeg4 @ 0x30984c0] too many threads/slices (16), reducing to 15
 Output #0, mp4, to '.output':
   Metadata:
     encoder         : Lavf59.6.100
   Stream #0:0: Video: mpeg4 (mp4v / 0x7634706D), yuv420p(tv, progressive),
 352x240, q=2-31, 200 kb/s, 29.97 fps, 11988 tbn
     Metadata:
       encoder         : Lavc59.12.100 mpeg4
     Side data:
       cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
 [rawvideo @ 0x3096ac0] Packet too small (8)ime=00:00:00.00
 bitrate=4241.0kbits/s speed=N/A
 Error while decoding stream #0:0: Invalid data found when processing input
 [rawvideo @ 0x3096ac0] Packet too small (8)
 Error while decoding stream #0:0: Invalid data found when processing input
 frame=   40 fps=0.0 q=31.0 Lsize=     434kB time=00:00:01.30
 bitrate=2732.4kbits/s dup=2 drop=0 speed=2.05x
 video:433kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.237240%
 }}}
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9458>
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