Function realloc 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn realloc(
    ptr: *mut c_void,
    size: usize,
) -> *mut c_void

Changes the size of the memory block pointed to by ptr to size bytes. If the returned ptr is non-null, any usage of the old memory block is immediately undefined behavior.

Safety

ptr must be a pointer to a memory block previously allocated by memory::malloc, memory::calloc, or memory::realloc.