The Open Group Base Specifications Issue 7, 2018 edition
IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008)
Copyright © 2001-2018 IEEE and The Open Group

NAME

calloc - a memory allocator

SYNOPSIS

#include <stdlib.h>

void *calloc(size_t
nelem, size_t elsize);

DESCRIPTION

[CX] [Option Start] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO C standard. [Option End]

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: either a null pointer shall be returned, or the behavior shall be as if the size were some non-zero value, except that the behavior is undefined if the returned pointer is used to access an object.

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:

Otherwise, it shall return a null pointer [CX] [Option Start]  and set errno to indicate the error. [Option End]

ERRORS

The calloc() function shall fail if:

[ENOMEM]
[CX] [Option Start] Insufficient memory is available. [Option End]

The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

There is now no requirement for the implementation to support the inclusion of <malloc.h>.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

free, malloc, realloc

XBD <stdlib.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 6

Extensions beyond the ISO C standard are marked.

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

Issue 7

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0053 [526] is applied.

End of informative text.

 

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