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Yahweasel / libav.js

This is a compilation of the libraries associated with handling audio and video in ffmpeg—libavformat, libavcodec, libavfilter, libavutil, libswresample, and libswscale—for emscripten, and thus the web.
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Error while free'ing a dict #35

Closed reinhrst closed 7 months ago

reinhrst commented 8 months ago

Researching https://github.com/Yahweasel/libav.js/issues/34, I came to a smallest example that produces the error:

<!doctype html>
<html>
  <body>
    <script type="text/javascript">LibAV = {base: "/thirdparty/libav.js-4.5.6.0/dist"};</script>
    <script type="text/javascript" src="/thirdparty/libav.js-4.5.6.0/dist/libav-4.5.6.0-default.dbg.js"></script>
    <script type="text/javascript">(async function() {
      const libav = await LibAV.LibAV({noworker: true});
      const options = libav.av_dict_set_js_sync(0, "max_packet_size", "204800", 0)
      console.log({options})
      libav.av_dict_free_sync(options)
    })();
    </script>
  </body>
</html>

This results in the following error:

{"options": 2850176}
Uncaught (in promise) RuntimeError: memory access out of bounds
    at dlfree (dlmalloc.c:4786:24)
    at av_freep (mem.c:241:5)
    at av_dict_free (dict.c:234:5)
    at ret.<computed> (libav-4.5.6.0-default.dbg.simd.js:5120:35)
    at Module._av_dict_free [as av_dict_free_sync] (libav-4.5.6.0-default.dbg.simd.js:6813:84)
    at (index):10:13

Using the async versions of the av_dict_* functions results in the same errors.

Yahweasel commented 7 months ago

Like av_dict_set, av_dict_free takes a pointer-pointer, and the _js version takes a pointer. If you're using av_dict_set_js, you should be using av_dict_free_js.