[FFmpeg-devel] Memory leak using bitstream filters with shared libs
Sun Mar 9 01:23:18 CET 2008
On Sun, Mar 09, 2008 at 12:05:33AM +0000, M?ns Rullg?rd wrote:
> Baptiste discovered a rather nasty memory leak when using a bitstream
> filter with shared libraries.
> In ffmpeg.c:write_frame() the output of bitstream filters is stored in
> an AVPacket, and its destruct function is set like this (line 417):
> new_pkt.destruct= av_destruct_packet;
> Later on, in av_interleave_packet_per_dts(), AVPacket.destruct is
> compared against av_destruct_packet, like this (utils.c:2439):
> if(pkt->destruct == av_destruct_packet)
> The trouble here is that with shared libraries, the address of
> av_destruct_packet when used in the main executable or libs other than
> the one defining it resolves to a trampoline that calls the real
> function using a GOT entry. As a result, this comparison is always
> false when the destruct pointer was assigned outside libavformat.
> Does anyone have an idea for fixing this?
It's actually an implementation bug since the C language requires that
the addresses match. I suspect it's binutils doing something stupid
due to -Bsymbolic. Anyway this sort of problem is common enough that
I'd recommend avoiding comparison of function pointers. I'm not
familiar enough with the code to suggest an alternative though.
More information about the ffmpeg-devel