[FFmpeg-trac] #3194(avcodec:open): valgrind leak on example package (leaking global lock manager mutex at exit)

[FFmpeg]

#3194: valgrind  leak on example package (leaking global lock manager mutex at
exit)
-------------------------------------+-------------------------------------
             Reporter:  andreyv      |                    Owner:
                 Type:  defect       |  er.anshul.maheshwari@…
             Priority:  minor        |                   Status:  open
              Version:  git-master   |                Component:  avcodec
             Keywords:  leak         |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  1            |  Reproduced by developer:  1
-------------------------------------+-------------------------------------

Comment (by jyavenard):

 Why wasn't the codec_mutex not allocated on the stack instead ?

 The test that the codec_mutex has been allocated isn't thread-safe itself.
 (testing that a pointer isn't null isn't an atomic operation, and the
 behaviour is undefined in C or C++)

 https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/utils.c#L76
 {{{
         if (!*mutex) {
             pthread_mutex_t *tmp = av_malloc(sizeof(pthread_mutex_t));
             if (!tmp)
                 return AVERROR(ENOMEM);
 }}}

 so I don't see much the advantage in allocating codec_mutex on the stack ;
 and would get around valgrind reporting this has a leak.

 (I'm facing the same problem on our mozilla's ASAN build which has
 suddenly started to report failures to this 40 bytes (size of
 pthread_mutex_t on Linux 64 bits) object leaking)

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Ticket URL: <https://trac.ffmpeg.org/ticket/3194#comment:16>
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