REALLOC(P) POSIX Programmer's Manual REALLOC(P)PROLOG
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.
NAMErealloc - memory reallocator
SYNOPSIS
#include <stdlib.h>
void *realloc(void *ptr, size_t size);
DESCRIPTION
The realloc() function shall change the size of the memory object
pointed to by ptr to the size specified by size. The contents of the
object shall remain unchanged up to the lesser of the new and old
sizes. If the new size of the memory object would require movement of
the object, the space for the previous instantiation of the object is
freed. If the new size is larger, the contents of the newly allocated
portion of the object are unspecified. If size is 0 and ptr is not a
null pointer, the object pointed to is freed. If the space cannot be
allocated, the object shall remain unchanged.
If ptr is a null pointer, realloc() shall be equivalent to malloc() for
the specified size.
If ptr does not match a pointer returned earlier by calloc(), malloc(),
or realloc() or if the space has previously been deallocated by a call
to free() or realloc(), the behavior is undefined.
The order and contiguity of storage allocated by successive calls to
realloc() is unspecified. The pointer returned if the allocation suc‐
ceeds 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 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.
RETURN VALUE
Upon successful completion with a size not equal to 0, realloc() shall
return a pointer to the (possibly moved) allocated space. If size is 0,
either a null pointer or a unique pointer that can be successfully
passed to free() shall be returned. If there is not enough available
memory, realloc() shall return a null pointer and set errno to
[ENOMEM].
ERRORS
The realloc() function shall fail if:
ENOMEM Insufficient memory is available.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOcalloc() , free() , malloc() , the Base Definitions volume of
IEEE Std 1003.1-2001, <stdlib.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .
IEEE/The Open Group 2003 REALLOC(P)
