calloc()

Allocate space for an array

Synopsis:

#include <stdlib.h>

void* calloc ( size_t n, 
               size_t size );

Arguments:

n

The number of array elements to allocate.

size

The size, in bytes, of one array element.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The calloc() function allocates space from the heap for an array of n objects, each of size bytes, and initializes them to 0. Use free() or realloc() to free the block of memory.

If n or size is zero, the default behavior is to return a non-NULL pointer that's valid only to a corresponding call to free() or realloc(). Don't assume that this pointer points to any valid memory. You can control this behavior via the MALLOC_OPTIONS environmental variable; if the value of MALLOC_OPTIONS contains a V, calloc() returns a NULL pointer. This environment variable also affects malloc() and realloc(). This is known as the “System V” behavior.

Returns:

A pointer to the start of the allocated memory, or NULL if an error occurred (errno is set).

Errors:

ENOMEM

Not enough memory.

EOK

No error.

Examples:

#include <stdlib.h>
#include <stdio.h>

int main( void )
{
    char* buffer;

    buffer = (char* )calloc( 80, sizeof(char) );
    if( buffer == NULL ) {
        printf( "Can't allocate memory for buffer!\n" );
        return EXIT_FAILURE;
    }

    free( buffer );

    return EXIT_SUCCESS;
}

Environment variables:

MALLOC_OPTIONS

Control the way calloc(), malloc(), and realloc() behave if you specify a size of 0 (or a value of 0 for the n argument to calloc()). The V (“System V”) and R (“use the realloc() behavior of QNX Neutrino 6.4.0 and earlier”) columns below indicate how the functions behave if the value of MALLOC_OPTIONS includes that letter:

Function	Default	V	R
calloc(n, 0)	Non-NULL	NULL	No effect
malloc(0)	Non-NULL	NULL	No effect
realloc(NULL, 0)	Non-NULL	NULL	No effect
realloc(non-NULL, 0)	Non-NULL	NULL	NULL

In all the above cases, if the function returns a non-NULL pointer, it's valid only for a corresponding call to free() or realloc().

Classification:

ANSI, POSIX 1003.1

See also:

free(), malloc(), realloc(), sbrk()