函数 av_mallocz 

pub unsafe extern "C" fn av_mallocz(size: usize) -> *mut c_void

Allocate a memory block with alignment suitable for all memory accesses (including vectors if available on the CPU) and zero all the bytes of the block.

@param size Size in bytes for the memory block to be allocated @return Pointer to the allocated block, or NULL if it cannot be allocated @see av_malloc()