[FFmpeg-trac] #2526(undetermined:new): ffmpeg on windows crashes when using Avisynth 2.5.8

[FFmpeg]

#2526: ffmpeg on windows crashes when using Avisynth 2.5.8
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             Reporter:  Zarxrax      |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  important    |                Component:
              Version:  unspecified  |  undetermined
             Keywords:  regression   |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
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Comment (by qyot27):

 It does affect 4.7.x as well, as part of that discussion Zarxrax linked to
 originally dealt with builds that were compiled with 4.7.2.  It was
 exactly the same sort of error in DllMain, and only affected AviSynth
 2.5.8.

 For that matter, I can also confirm that MSVC builds exhibit this problem
 with 2.5.8 (while 2.6 works fine) as well.  I'd compiled an MSVC test
 build for that discussion, and can reproduce it with said same build
 (which, granted, is from April 21st, but the gdb output of that MSVC build
 is exactly the same as the backtrace from the current build I posted
 above).

 Unless I'm way off (totally possible here), the crash seems to be
 occurring *within* avisynth.dll, due to how libavformat is trying to load
 it. The DllMain errors would seem to point to this. My best guess is that
 AviSynth 2.6 adds protection meant to avoid this problem, and it doesn't
 show up on Linux/OSX because dlopen doesn't have the same limitations as
 LoadLibrary, or because AvxSynth (which is based on AviSynth 2.5.8)
 backported any necessary changes concerning this issue from 2.6.

 One distinct difference between libavformat/avisynth.c and x264's
 input/avs.c is that in x264's case the struct containing the
 AVSC_DECLARE_FUNC definitions (func) is nested inside the struct for the
 environment (avs_hnd_t), whereas in libavformat, AviSynthLibrary and
 AviSynthContext are separate from each other.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2526#comment:6>
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