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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>realloc</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_007_1927"> </a>NAME</h4><blockquote>realloc - memory reallocator</blockquote><h4><a name = "tag_000_007_1928"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="stdlib.h.html">stdlib.h</a>>void *realloc(void *<i>ptr</i>, size_t <i>size</i>);</code></pre></blockquote><h4><a name = "tag_000_007_1929"> </a>DESCRIPTION</h4><blockquote>The<i>realloc()</i>function changes the size of the memory object pointed to by<i>ptr</i>to the size specified by<i>size</i>.The contents of the object will remain unchanged up to the lesser of thenew and old sizes.If the new size of the memory object would requiremovement of the object, the space for the previous instantiation of theobject is freed.If the new size is larger, the contents of the newly allocated portion ofthe object are unspecified. If<i>size</i>is 0 and<i>ptr</i>is not a null pointer,the object pointed to is freed.If the space cannot be allocated, theobject remains unchanged.<p>If<i>ptr</i>is a null pointer,<i>realloc()</i>behaves like<i><a href="malloc.html">malloc()</a></i>for the specified size.<p>If<i>ptr</i>does not match a pointer returned earlier by<i><a href="calloc.html">calloc()</a></i>,<i><a href="malloc.html">malloc()</a></i>or<i>realloc()</i>or if the space has previously been deallocated by a call to<i><a href="free.html">free()</a></i>or<i>realloc()</i>,the behaviour is undefined.<p>The order and contiguity of storage allocated by successive calls to<i>realloc()</i>is unspecified.The pointer returned if the allocation succeeds is suitablyaligned so that it may be assigned to a pointer to any type ofobject and then used to access such an object in the spaceallocated (until the space is explicitly freed or reallocated).Each such allocation will yield a pointer to an object disjointfrom any other object.The pointer returned points to the start (lowest byte address) ofthe allocated space.If the space cannot be allocated, a null pointer is returned.</blockquote><h4><a name = "tag_000_007_1930"> </a>RETURN VALUE</h4><blockquote>Upon successful completion with a size not equal to 0,<i>realloc()</i>returns a pointer to the (possibly moved) allocated space.If<i>size</i>is 0, either a null pointer or a unique pointer thatcan be successfully passed to<i><a href="free.html">free()</a></i>is returned.If there isnot enough available memory,<i>realloc()</i>returnsa null pointer and sets<i>errno</i>to [ENOMEM].</blockquote><h4><a name = "tag_000_007_1931"> </a>ERRORS</h4><blockquote>The<i>realloc()</i>function will fail if:<dl compact><dt>[ENOMEM]<dd>Insufficient memory is available.</dl></blockquote><h4><a name = "tag_000_007_1932"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_1933"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_1934"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_1935"> </a>SEE ALSO</h4><blockquote><i><a href="calloc.html">calloc()</a></i>,<i><a href="free.html">free()</a></i>,<i><a href="malloc.html">malloc()</a></i>,<i><a href="stdlib.h.html"><stdlib.h></a></i>.</blockquote><h4>DERIVATION</h4><blockquote>Derived from Issue 1 of the SVID.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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