105 lines
3.3 KiB
HTML
105 lines
3.3 KiB
HTML
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Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009, 2013
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The President and Fellows of Harvard College.
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-->
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<html>
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<head>
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<title>free</title>
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<link rel="stylesheet" type="text/css" media="all" href="../man.css">
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</head>
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<body bgcolor=#ffffff>
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<h2 align=center>free</h2>
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<h4 align=center>OS/161 Reference Manual</h4>
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<h3>Name</h3>
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<p>
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free - release/deallocate memory
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</p>
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<h3>Library</h3>
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<p>
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Standard C Library (libc, -lc)
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</p>
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<h3>Synopsis</h3>
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<p>
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<tt>#include <stdlib.h></tt><br>
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<br>
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<tt>void</tt><br>
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<tt>free(void *</tt><em>ptr</em><tt>);</tt>
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</p>
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<h3>Description</h3>
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<p>
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<tt>free</tt> releases a block of memory previously allocated with
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<A HREF=malloc.html>malloc</A>, <A HREF=calloc.html>calloc</A>,
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or <A HREF=realloc.html>realloc</A>.
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</p>
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<p>
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Once free has been called, <em>ptr</em> is no longer valid and
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attempts to dereference it result in undefined behavior.
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(Pedantically, in fact, even using the <i>value</i> of
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<em>ptr</em> may produce undefined behavior.) Passing <em>ptr</em> to
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free a second or subsequent time (unless of course the same pointer
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value is again returned from malloc) is also undefined and
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particularly likely to provoke adverse behavior in most
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implementations.
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</p>
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<p>
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<tt>free(NULL)</tt> has no effect.
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</p>
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<p>
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In practice it is desirable for implementations of <tt>free</tt> to
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detect, to the extent practically possible, pointers that were not
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previously allocated by one of the above functions or that are passed
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to <tt>free</tt> multiple times. However, this can be difficult and
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there is no useful standard mechanism for error reporting.
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</p>
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<p>
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<tt>free</tt> does not necessarily unmap free memory or return it to
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the operating system, but may do so if it chooses.
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</p>
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<h3>Return Values</h3>
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<p>
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<tt>free</tt> returns no value.
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<p>
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<h3>See Also</h3>
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<p>
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<A HREF=calloc.html>calloc</A>,
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<A HREF=malloc.html>malloc</A>,
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<A HREF=realloc.html>realloc</A>
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</p>
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</body>
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</html>
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