Function dlmemalign 

pub unsafe extern "C" fn dlmemalign(
    alignment: usize,
    n: usize,
) -> *mut c_void

memalign(size_t alignment, size_t n);

Returns a pointer to a newly allocated chunk of n bytes, aligned in accord with the alignment argument.

The alignment argument should be a power of two. If the argument is not a power of two, the nearest greater power is used. 8-byte alignment is guaranteed by normal malloc calls, so don’t bother calling memalign with an argument of 8 or less.

Overreliance on memalign is a sure way to fragment space.