1.\" $NetBSD: alloca.3,v 1.12 2003/08/07 16:43:37 agc Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" from: @(#)alloca.3 8.1 (Berkeley) 6/4/93 31.\" 32.Dd August 11, 2002 33.Dt ALLOCA 3 34.Os 35.Sh NAME 36.Nm alloca 37.Nd memory allocator 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In stdlib.h 42.Ft void * 43.Fn alloca "size_t size" 44.Sh DESCRIPTION 45The 46.Fn alloca 47function 48allocates 49.Fa size 50bytes of space in the stack frame of the caller. 51This temporary space is automatically freed on 52return. 53.Sh RETURN VALUES 54The 55.Fn alloca 56function returns a pointer to the beginning of the allocated space. 57If the allocation failed, a 58.Dv NULL 59pointer is returned. 60.Sh SEE ALSO 61.Xr brk 2 , 62.Xr calloc 3 , 63.Xr getpagesize 3 , 64.Xr malloc 3 , 65.Xr realloc 3 66.Sh BUGS 67The 68.Fn alloca 69function 70is machine dependent; its use is discouraged. 71.Pp 72The 73.Fn alloca 74function is slightly unsafe because it cannot ensure that the pointer 75returned points to a valid and usable block of memory. 76The allocation made may exceed the bounds of the stack, or even go 77further into other objects in memory, and 78.Fn alloca 79cannot determine such an error. 80Avoid 81.Fn alloca 82with large unbounded allocations. 83.\" .Sh HISTORY 84.\" The 85.\" .Fn alloca 86.\" function appeared in 87.\" .Bx ?? . 88.\" The function appeared in 32v, pwb and pwb.2 and in 3bsd 4bsd 89.\" The first man page (or link to a man page that I can find at the 90.\" moment is 4.3... 91