void av_freep(void *ptr);
Pointer to the pointer to the memory block which should be freed.
NOTE: ptr should be declared as a void**, eg. it should be used as in the following example:
void *p = av_malloc(42); av_freep(&p); // Now the memory is freed, and p has the value NULL.
Using av_freep is equivalent to using av_free and manually setting the pointer to NULL afterwards.