freebsd-nq/lib/libc/stdlib/alloca.3

.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
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.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
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.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" SUCH DAMAGE.
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.\"     @(#)alloca.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd September 5, 2006
.Dt ALLOCA 3
.Os
.Sh NAME
.Nm alloca
.Nd memory allocator
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft void *
.Fn alloca "size_t size"
.Sh DESCRIPTION
The
.Fn alloca
function
allocates
.Fa size
bytes of space in the stack frame of the caller.
This temporary space is automatically freed on
return.
.Sh RETURN VALUES
The
.Fn alloca
function returns a pointer to the beginning of the allocated space.
.Sh SEE ALSO
.Xr brk 2 ,
.Xr calloc 3 ,
.Xr getpagesize 3 ,
.Xr malloc 3 ,
.Xr realloc 3
.Sh HISTORY
The
.Fn alloca
function appeared in
.At 32v .
.\" .Bx ?? .
.\" The function appeared in 32v, pwb and pwb.2 and in 3bsd 4bsd
.\" The first man page (or link to a man page that I can find at the
.\" moment is 4.3...
.Sh BUGS
The
.Fn alloca
function
is machine and compiler dependent;
its use is discouraged.
.Pp
The
.Fn alloca
function is slightly unsafe because it cannot ensure that the pointer
returned points to a valid and usable block of memory.
The allocation made may exceed the bounds of the stack, or even go
further into other objects in memory, and
.Fn alloca
cannot determine such an error.
Avoid
.Fn alloca
with large unbounded allocations.
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" Copyright (c) 1980, 1991, 1993`
			`.\" The Regents of the University of California. All rights reserved.`
			`.\"`
			`.\" Redistribution and use in source and binary forms, with or without`
			`.\" modification, are permitted provided that the following conditions`
			`.\" are met:`
			`.\" 1. Redistributions of source code must retain the above copyright`
			`.\" notice, this list of conditions and the following disclaimer.`
			`.\" 2. Redistributions in binary form must reproduce the above copyright`
			`.\" notice, this list of conditions and the following disclaimer in the`
			`.\" documentation and/or other materials provided with the distribution.`
Renumber clauses to reduce diffs to other versions NetBSD, OpenBSD, and Android's Bionic number the clauses 1 through 3, so follow suit to make comparison easier. 2013-05-28 20:57:40 +00:00			`.\" 3. Neither the name of the University nor the names of its contributors`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" may be used to endorse or promote products derived from this software`
			`.\" without specific prior written permission.`
			`.\"`
			.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
			`.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE`
			`.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE`
			`.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE`
			`.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL`
			`.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS`
			`.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)`
			`.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT`
			`.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY`
			`.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF`
			`.\" SUCH DAMAGE.`
			`.\"`
			`.\" @(#)alloca.3 8.1 (Berkeley) 6/4/93`
$Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00			`.\" $FreeBSD$`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\"`
alloca() cannot check if the allocation is valid; mention the consequences. Obtained from: OpenBSD 2006-09-05 16:30:11 +00:00			`.Dd September 5, 2006`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Dt ALLOCA 3`
mdoc(7) police: removed HISTORY info from the .Os call. 2001-07-10 13:41:46 +00:00			`.Os`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh NAME`
			`.Nm alloca`
			`.Nd memory allocator`
Introduce ".Lb" macro to libc manpages. More libraries manpages updates following. 2000-04-21 09:42:15 +00:00			`.Sh LIBRARY`
			`.Lb libc`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh SYNOPSIS`
Move to using .In instead of .Fd #include <> for include mark-up. Inspired by comment from: dd 2001-09-07 14:46:36 +00:00			`.In stdlib.h`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Ft void *`
			`.Fn alloca "size_t size"`
			`.Sh DESCRIPTION`
			`The`
			`.Fn alloca`
			`function`
Remove whitespace at EOL. 2001-07-15 07:53:42 +00:00			`allocates`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Fa size`
			`bytes of space in the stack frame of the caller.`
			`This temporary space is automatically freed on`
			`return.`
			`.Sh RETURN VALUES`
			`The`
			`.Fn alloca`
			`function returns a pointer to the beginning of the allocated space.`
			`.Sh SEE ALSO`
			`.Xr brk 2 ,`
			`.Xr calloc 3 ,`
Correct a bunch of man page cross references and generally try and silence "manck". ncurses, rpc, and some of the gnu stuff are still a big mess, however. 1996-02-11 22:38:05 +00:00			`.Xr getpagesize 3 ,`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Xr malloc 3 ,`
Correct a bunch of man page cross references and generally try and silence "manck". ncurses, rpc, and some of the gnu stuff are still a big mess, however. 1996-02-11 22:38:05 +00:00			`.Xr realloc 3`
Be more specific in BUGS. Submitted by: ru Add history. 2003-06-25 19:18:44 +00:00			`.Sh HISTORY`
			`The`
			`.Fn alloca`
			`function appeared in`
mdoc(7) fix: Use the normal AT&T macro (.At) rather than its internal string in the macro context. 2003-06-28 22:12:30 +00:00			`.At 32v .`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" .Bx ?? .`
Remove whitespace at EOL. 2001-07-15 07:53:42 +00:00			`.\" The function appeared in 32v, pwb and pwb.2 and in 3bsd 4bsd`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" The first man page (or link to a man page that I can find at the`
			`.\" moment is 4.3...`
mdoc police 2003-06-25 21:31:43 +00:00			`.Sh BUGS`
			`The`
			`.Fn alloca`
			`function`
			`is machine and compiler dependent;`
			`its use is discouraged.`
alloca() cannot check if the allocation is valid; mention the consequences. Obtained from: OpenBSD 2006-09-05 16:30:11 +00:00			`.Pp`
			`The`
			`.Fn alloca`
			`function is slightly unsafe because it cannot ensure that the pointer`
			`returned points to a valid and usable block of memory.`
			`The allocation made may exceed the bounds of the stack, or even go`
			`further into other objects in memory, and`
			`.Fn alloca`
			`cannot determine such an error.`
			`Avoid`
			`.Fn alloca`
			`with large unbounded allocations.`