Provided by: manpages-posix-dev_2.16-1_all 
NAME
realloc - 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 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 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 ALSO
calloc() , 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 .