103 lines
3.1 KiB
Groff
103 lines
3.1 KiB
Groff
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.\" $NetBSD: alloca.3,v 1.13 2010/05/03 06:11:38 jruoho Exp $
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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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.\" 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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.\" from: @(#)alloca.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd May 3, 2010
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.Dt ALLOCA 3
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.Os
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.Sh NAME
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.Nm alloca
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.Nd memory allocator
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.Ft void *
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.Fn alloca "size_t size"
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.Sh DESCRIPTION
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The
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.Fn alloca
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function
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allocates
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.Fa size
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bytes of space in the stack frame of the caller.
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This temporary space is automatically freed on
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return.
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.Sh RETURN VALUES
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The
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.Fn alloca
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function returns a pointer to the beginning of the allocated space.
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If the allocation failed, a
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.Dv NULL
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pointer is returned.
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.Sh SEE ALSO
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.Xr brk 2 ,
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.Xr calloc 3 ,
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.Xr getpagesize 3 ,
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.Xr malloc 3 ,
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.Xr realloc 3
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.Sh CAVEATS
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Few limitations can be mentioned:
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.Bl -bullet
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.It
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The
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.Fn alloca
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function
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is machine dependent; its use is discouraged.
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.It
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The
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.Fn alloca
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function is slightly unsafe because it cannot ensure that the pointer
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returned points to a valid and usable block of memory.
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The allocation made may exceed the bounds of the stack, or even go
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further into other objects in memory, and
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.Fn alloca
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cannot determine such an error.
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Avoid
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.Fn alloca
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with large unbounded allocations.
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.It
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Since
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.Fn alloca
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modifies the stack at runtime,
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it causes problems to certain security features.
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See
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.Xr security 8
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for a discussion.
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.El
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.\" .Sh HISTORY
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.\" The
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.\" .Fn alloca
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.\" function appeared in
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.\" .Bx ?? .
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.\" The function appeared in 32v, pwb and pwb.2 and in 3bsd 4bsd
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.\" The first man page (or link to a man page that I can find at the
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.\" moment is 4.3...
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