161 lines
6.5 KiB
HTML
161 lines
6.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>realloc</title>
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<basefont size="3"> <a name="realloc"></a> <a name="tag_03_598"></a><!-- realloc -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_598_01"></a>NAME</h4>
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<blockquote>realloc - memory reallocator</blockquote>
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<h4><a name="tag_03_598_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/stdlib.h.html">stdlib.h</a>><br>
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<br>
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void *realloc(void *</tt><i>ptr</i><tt>, size_t</tt> <i>size</i><tt>);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_598_03"></a>DESCRIPTION</h4>
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<blockquote>
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<div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"
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border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
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requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to
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the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div>
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<p>The <i>realloc</i>() function shall change the size of the memory object pointed to by <i>ptr</i> to the size specified by
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<i>size</i>. The contents of the object shall remain unchanged up to the lesser of the new and old sizes. If the new size of the
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memory object would require movement of the object, the space for the previous instantiation of the object is freed. If the new
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size is larger, the contents of the newly allocated portion of the object are unspecified. If <i>size</i> is 0 and <i>ptr</i> is
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not a null pointer, the object pointed to is freed. If the space cannot be allocated, the object shall remain unchanged.</p>
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<p>If <i>ptr</i> is a null pointer, <i>realloc</i>() shall be equivalent to <a href="../functions/malloc.html"><i>malloc</i>()</a>
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for the specified size.</p>
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<p>If <i>ptr</i> does not match a pointer returned earlier by <a href="../functions/calloc.html"><i>calloc</i>()</a>, <a href=
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"../functions/malloc.html"><i>malloc</i>()</a>, or <i>realloc</i>() or if the space has previously been deallocated by a call to <a
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href="../functions/free.html"><i>free</i>()</a> or <i>realloc</i>(), the behavior is undefined.</p>
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<p>The order and contiguity of storage allocated by successive calls to <i>realloc</i>() is unspecified. The pointer returned if
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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
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access such an object in the space allocated (until the space is explicitly freed or reallocated). Each such allocation shall yield
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a pointer to an object disjoint from any other object. The pointer returned shall point to the start (lowest byte address) of the
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allocated space. If the space cannot be allocated, a null pointer shall be returned.</p>
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</blockquote>
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<h4><a name="tag_03_598_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion with a size not equal to 0, <i>realloc</i>() shall return a pointer to the (possibly moved) allocated
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space. If <i>size</i> is 0, either a null pointer or a unique pointer that can be successfully passed to <a href=
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"../functions/free.html"><i>free</i>()</a> shall be returned. If there is not enough available memory, <i>realloc</i>() shall
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return a null pointer <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> and set <i>errno</i> to [ENOMEM]. <img src="../images/opt-end.gif" alt="[Option End]" border=
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"0"></p>
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</blockquote>
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<h4><a name="tag_03_598_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>realloc</i>() function shall fail if:</p>
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<dl compact>
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<dt>[ENOMEM]</dt>
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<dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Insufficient memory is available. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_598_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_598_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_598_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_598_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_598_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="calloc.html"><i>calloc</i>()</a> , <a href="free.html"><i>free</i>()</a> , <a href="malloc.html"><i>malloc</i>()</a> ,
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the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/stdlib.h.html"><i><stdlib.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_598_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 1. Derived from Issue 1 of the SVID.</p>
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</blockquote>
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<h4><a name="tag_03_598_12"></a>Issue 6</h4>
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<blockquote>
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<p>Extensions beyond the ISO C standard are marked.</p>
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<p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p>
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<ul>
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<li>
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<p>In the RETURN VALUE section, if there is not enough available memory, the setting of <i>errno</i> to [ENOMEM] is added.</p>
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</li>
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<li>
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<p>The [ENOMEM] error condition is added.</p>
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</li>
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</ul>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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