Wednesday, November 2, 2011

calloc c

Allocating Memory with calloc

calloc is declared as follows,

#include <stdlib.h>
void *calloc(size_t nelem, size_t elsize);

The calloc() function shall allocate unused space for an array of nelem elements each of whose size in bytes is elsize. The space shall be initialized to all bits 0.
The order and contiguity of storage allocated by successive calls to calloc() is unspecified. The pointer returned if the allocation succeeds shall be suitably aligned so that it may be assigned to a pointer to any type of object and then used to access such an object or an array of such objects in the space allocated (until the space is explicitly freed or reallocated). Each such allocation shall yield a pointer to an object disjoint from any other object. The pointer returned shall point to the start (lowest byte address) of the allocated space. If the space cannot be allocated, a null pointer shall be returned. If the size of the space requested is 0, the behavior is implementation-defined: the value returned shall be either a null pointer or a unique pointer.

Return Value: 

Upon successful completion with both nelem and elsize non-zero, calloc() shall return a pointer to the allocated space. If either nelem or elsize is 0, then either a null pointer or a unique pointer value that can be successfully passed to free() shall be returned. Otherwise, it shall return a null pointer  and set errno to indicate the error

The calloc() function shall fail if: Insufficient memory is available.


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