#define _BSD_SOURCE
#include <errno.h>
#include <stdlib.h>
#include <string.h>

void *recallocarray(void *ptr, size_t om, size_t m, size_t n)
{
	void *newptr;
	size_t old_size = om * n, new_size;

	if (n && m > -1 / n) {
		errno = ENOMEM;
		return 0;
	}
	new_size = m * n;

	if (new_size <= old_size) {
		memset((char *) ptr + new_size, 0, old_size - new_size);
	}

	newptr = realloc(ptr, m * n);
	if (new_size > old_size) {
		memset((char *) ptr + old_size, 0, new_size - old_size);
	}

	return newptr;
}