realloc

type *currptr = realloc(oldptr, num_bytes)

• Resizes a previous allocation, recalling malloc for your new specified size
• Find space for new allocation
• Copy original data into new space
  • Truncating if allocating less than original
• Free old malloc space
• If successful
  • Return pointer to new space
  • oldptr has been freed by realloc and should never be used again
• If fails
  • Return null
  • oldptr has not been freed and still maintains its reference to the original malloc block

Tip

malloc(n) = realloc(NULL, n)

Template

type *cp = malloc(...);
{
	void *tmp;
	if ((tmp = realloc(cp, ...)) == NULL) {
		/* realloc error */
		free(cp);
		// probably crash program here
	} else {
		cp = tmp;
	}
}

See also

Heap Allocation