1REALLOC(3P) POSIX Programmer's Manual REALLOC(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 realloc - memory reallocator
13
15 #include <stdlib.h>
16 void *realloc(void *ptr, size_t size);
18
21 The realloc() function shall change the size of the memory object
22 pointed to by ptr to the size specified by size. The contents of the
23 object shall remain unchanged up to the lesser of the new and old
24 sizes. If the new size of the memory object would require movement of
25 the object, the space for the previous instantiation of the object is
26 freed. If the new size is larger, the contents of the newly allocated
27 portion of the object are unspecified. If size is 0 and ptr is not a
28 null pointer, the object pointed to is freed. If the space cannot be
29 allocated, the object shall remain unchanged.
30 If ptr is a null pointer, realloc() shall be equivalent to malloc() for
32 the specified size.
33 If ptr does not match a pointer returned earlier by calloc(), malloc(),
35 or realloc() or if the space has previously been deallocated by a call
36 to free() or realloc(), the behavior is undefined.
37 The order and contiguity of storage allocated by successive calls to
39 realloc() is unspecified. The pointer returned if the allocation suc‐
40 ceeds shall be suitably aligned so that it may be assigned to a pointer
41 to any type of object and then used to access such an object in the
42 space allocated (until the space is explicitly freed or reallocated).
43 Each such allocation shall yield a pointer to an object disjoint from
44 any other object. The pointer returned shall point to the start (lowest
45 byte address) of the allocated space. If the space cannot be allocated,
46 a null pointer shall be returned.
47
49 Upon successful completion with a size not equal to 0, realloc() shall
50 return a pointer to the (possibly moved) allocated space. If size is 0,
51 either a null pointer or a unique pointer that can be successfully
52 passed to free() shall be returned. If there is not enough available
53 memory, realloc() shall return a null pointer and set errno to
54 [ENOMEM].
55
57 The realloc() function shall fail if:
58 ENOMEM Insufficient memory is available.
60 The following sections are informative.
63
65 None.
66
68 None.
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71 None.
72
74 None.
75
77 calloc(), free(), malloc(), the Base Definitions volume of
78 IEEE Std 1003.1-2001, <stdlib.h>
79
81 Portions of this text are reprinted and reproduced in electronic form
82 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
83 -- Portable Operating System Interface (POSIX), The Open Group Base
84 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
85 Electrical and Electronics Engineers, Inc and The Open Group. In the
86 event of any discrepancy between this version and the original IEEE and
87 The Open Group Standard, the original IEEE and The Open Group Standard
88 is the referee document. The original Standard can be obtained online
89 at http://www.opengroup.org/unix/online.html .
90IEEE/The Open Group 2003 REALLOC(3P)