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.
calloc — a memory allocator
#include <stdlib.h>
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.1‐2017 defers to the ISO C standard.
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.
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 shall be returned and errno may be
set to an implementation-defined value, or
- *
- A pointer to the allocated space shall be returned. The
application shall ensure that the pointer is not used to access an
object.
Otherwise, it shall return a null pointer and set
errno to indicate the
error.
The
calloc() function shall fail if:
- ENOMEM
- Insufficient memory is available.
The following sections are informative.
None.
There is now no requirement for the implementation to support the inclusion of
<malloc.h>.
None.
None.
free(),
malloc(),
realloc()
The Base Definitions volume of POSIX.1‐2017,
<stdlib.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1-2017, Standard for Information Technology -- Portable Operating
System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018
Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. 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
http://www.opengroup.org/unix/online.html .
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
https://www.kernel.org/doc/man-pages/reporting_bugs.html .