1.\" $NetBSD: alloca.3,v 1.10 2002/08/10 16:55:18 yamt 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. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" from: @(#)alloca.3 8.1 (Berkeley) 6/4/93 35.\" 36.Dd August 11, 2002 37.Dt ALLOCA 3 38.Os 39.Sh NAME 40.Nm alloca 41.Nd memory allocator 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include \*[Lt]stdlib.h\*[Gt] 46.Ft void * 47.Fn alloca "size_t size" 48.Sh DESCRIPTION 49The 50.Fn alloca 51function 52allocates 53.Fa size 54bytes of space in the stack frame of the caller. 55This temporary space is automatically freed on 56return. 57.Sh RETURN VALUES 58The 59.Fn alloca 60function returns a pointer to the beginning of the allocated space. 61If the allocation failed, a 62.Dv NULL 63pointer is returned. 64.Sh SEE ALSO 65.Xr brk 2 , 66.Xr calloc 3 , 67.Xr getpagesize 3 , 68.Xr malloc 3 , 69.Xr realloc 3 70.Sh BUGS 71The 72.Fn alloca 73function 74is machine dependent; its use is discouraged. 75.Pp 76The 77.Fn alloca 78function is slightly unsafe because it cannot ensure that the pointer 79returned points to a valid and usable block of memory. 80The allocation made may exceed the bounds of the stack, or even go 81further into other objects in memory, and 82.Fn alloca 83cannot determine such an error. 84Avoid 85.Fn alloca 86with large unbounded allocations. 87.\" .Sh HISTORY 88.\" The 89.\" .Fn alloca 90.\" function appeared in 91.\" .Bx ?? . 92.\" The function appeared in 32v, pwb and pwb.2 and in 3bsd 4bsd 93.\" The first man page (or link to a man page that I can find at the 94.\" moment is 4.3... 95