1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)alloca.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd September 5, 2006 36.Dt ALLOCA 3 37.Os 38.Sh NAME 39.Nm alloca 40.Nd memory allocator 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In stdlib.h 45.Ft void * 46.Fn alloca "size_t size" 47.Sh DESCRIPTION 48The 49.Fn alloca 50function 51allocates 52.Fa size 53bytes of space in the stack frame of the caller. 54This temporary space is automatically freed on 55return. 56.Sh RETURN VALUES 57The 58.Fn alloca 59function returns a pointer to the beginning of the allocated space. 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 HISTORY 67The 68.Fn alloca 69function appeared in 70.At 32v . 71.\" .Bx ?? . 72.\" The function appeared in 32v, pwb and pwb.2 and in 3bsd 4bsd 73.\" The first man page (or link to a man page that I can find at the 74.\" moment is 4.3... 75.Sh BUGS 76The 77.Fn alloca 78function 79is machine and compiler dependent; 80its use is discouraged. 81.Pp 82The 83.Fn alloca 84function is slightly unsafe because it cannot ensure that the pointer 85returned points to a valid and usable block of memory. 86The allocation made may exceed the bounds of the stack, or even go 87further into other objects in memory, and 88.Fn alloca 89cannot determine such an error. 90Avoid 91.Fn alloca 92with large unbounded allocations. 93