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
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.
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.
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:
The following sections are informative.
There is now no requirement for the implementation to support the inclusion of <malloc.h>.
free(), malloc(), realloc()
The Base Definitions volume of POSIX.1‐2008, <stdlib.h>
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 http://www.unix.org/online.html .
- Insufficient memory is available.
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