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This should guarantee that even if the system provides or will provide native implementations of these functions, we will not have file conflicts.
103 lines
3.2 KiB
Plaintext
103 lines
3.2 KiB
Plaintext
.\"
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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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