memory leak in fftools/ffmpeg_opt.c file's opt_map_channel function

[Hripsime]

The opt_map_channel function in the fftools/ffmpeg_opt.c source file appears to contain a memory leak. Specifically, memory is allocated using av_strdup() in line 472:

mapchan = av_strdup(arg);

However, the function contains multiple exit_program() calls that terminate the program without freeing the allocated memory in lines 507, 513, 519, and 533.

[Cigaes]

Exiting without freeing all memory is not a leak. All the memory is freed by the operating system.

[Balling]

All the memory is freed by the operating system.

*modern operating system. And anyway, GPU memory will not be, handles will not be closed, even files opened will not be closed. And of course it makes closing slower, since OS will still check the state before closing the threads.

[quinkblack]

It's important to cleanup resources manually so we can detect if there is any memleak in our libs.

Should be fixed by ​http://ffmpeg.org/pipermail/ffmpeg-devel/2023-May/309209.html