realloc - Alter memory space

Definition	#include <stdlib.h> void *realloc(void *p, size_t n); realloc changes the size of the memory area pointed to by p to n bytes. p must have been returned by a previous malloc or calloc call. realloc is part of a C-specific memory management package which internally administers memory areas that are requested and subsequently freed. Attempts are made to satisfy new requests by first using areas that are already being managed and only then by the operating system (cf. garbcoll function).
Return val.	Pointer to the beginning of the modified memory area
		if successful.
	NULL pointer	if realloc was unable to alter the memory space, e.g. because the memory space still available is insufficient or because an error occurred.
Notes	If realloc alters the size of a memory area, it may happen that the allocated block is shifted. In such cases, the contents of the pointer passed as an argument are not identical with the return value. The contents of the block are preserved up to the minimum of the old (when enlarging) and new (when reducing) sizes. If realloc returns the NULL pointer, the block to which p points may have been destroyed! If p is a NULL pointer, realloc functions like a malloc call for the specified size. If n has the value 0, realloc returns an unambiguous address which can also be transferred to free.
Example	The following program fragment first requests memory space for 20 characters and then extends this area to accept 80 additional characters (i.e. to a total of 100 bytes). #include <stdlib.h> char *char_array; char_array = (char *)malloc(20 * sizeof(char)); . . char_array = (char *)realloc(char_array, 100 * sizeof(char));
See also	malloc, calloc, free, garbcoll