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103 lines
3.2 KiB
Plaintext
103 lines
3.2 KiB
Plaintext
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.\"
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.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the American National Standards Committee X3, on Information
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.\" Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $OpenBSD: malloc.3,v 1.78 2014/05/01 18:41:59 jmc Exp $
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.\"
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.Dd $Mdocdate: May 1 2014 $
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.Dt MALLOC 3
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.Os
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.Sh NAME
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.Nm reallocarray
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.Nd memory allocation and deallocation
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.Sh LIBRARY
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.ds str-Lb-libbsd Utility functions from BSD systems (libbsd, \-lbsd)
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.Lb libbsd
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.Sh SYNOPSIS
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.In bsd/stdlib.h
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.Ft void *
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.Fn reallocarray "void *ptr" "size_t nmemb" "size_t size"
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.Sh DESCRIPTION
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.Pp
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When using
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.Fn malloc
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be careful to avoid the following idiom:
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.Bd -literal -offset indent
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if ((p = malloc(num * size)) == NULL)
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err(1, "malloc");
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.Ed
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.Pp
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The multiplication may lead to an integer overflow, which can
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be avoided using the extension
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.Fn reallocarray ,
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as follows:
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.Bd -literal -offset indent
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if ((p = reallocarray(NULL, num, size)) == NULL)
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err(1, "malloc");
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.Ed
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.Pp
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Alternatively
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.Fn calloc
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is a more portable solution which comes with the cost of clearing memory.
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.Pp
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If
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.Fn malloc
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must be used, be sure to test for overflow:
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.Bd -literal -offset indent
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if (size && num > SIZE_MAX / size) {
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errno = ENOMEM;
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err(1, "overflow");
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}
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.Ed
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.Pp
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The use of
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.Fn reallocarray
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or
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.Fn calloc
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is strongly encouraged when allocating multiple sized objects
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in order to avoid possible integer overflows.
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.Sh RETURN VALUES
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The
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.Fn reallocarray
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function returns a pointer to the allocated space if successful; otherwise,
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a null pointer is returned and
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.Va errno
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is set to
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.Er ENOMEM .
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.Sh SEE ALSO
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.Xr malloc 3 ,
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.Xr calloc 3 ,
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.Xr alloca 3
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.Sh HISTORY
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.Fn reallocarray
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appeared in
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.Ox 5.6 .
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