REALLOC(3P)                                         POSIX Programmer's Manual                                        REALLOC(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   REALLOC(3P)