Section: POSIX Programmer's Manual (3P)
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
--- a memory allocator
void *calloc(size_t nelem, size_t elsize);
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.1-2008 defers to the ISO C standard.
function shall allocate unused space for an array of
elements each of whose size in bytes is
The space shall be initialized to all bits 0.
The order and contiguity of storage allocated by successive calls to
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.
Upon successful completion with both
shall return a pointer to the allocated space. If either
is 0, then either a null pointer or a unique pointer value that can be
successfully passed to
shall be returned. Otherwise, it shall return a null pointer
to indicate the error.
function shall fail if:
Insufficient memory is available.
The following sections are informative.
There is now no requirement for the implementation to support the
The Base Definitions volume of POSIX.1-2008,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see