1.\" Copyright (c) 1980, 1991 Regents of the University of California. 2.\" 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.\" $OpenBSD: alloca.3,v 1.9 2001/12/06 04:21:27 deraadt Exp $ 33.\" 34.Dd May 2, 1991 35.Dt ALLOCA 3 36.Os 37.Sh NAME 38.Nm alloca 39.Nd memory allocator 40.Sh SYNOPSIS 41.Fd #include <stdlib.h> 42.Ft void * 43.Fn alloca "size_t size" 44.Sh DESCRIPTION 45The 46.Fn alloca 47function allocates 48.Fa size 49bytes of space in the stack frame of the caller. 50This temporary space is automatically freed on return. 51.Sh RETURN VALUES 52The 53.Fn alloca 54function returns a pointer to the beginning of the allocated space. 55.Sh SEE ALSO 56.Xr pagesize 1 , 57.Xr brk 2 , 58.Xr calloc 3 , 59.Xr malloc 3 , 60.Xr realloc 3 61.Sh BUGS 62The 63.Fn alloca 64function is machine dependent; its use is discouraged. 65.\" .Sh HISTORY 66.\" The 67.\" .Fn alloca 68.\" function appeared in 69.\" .Bx ?? . 70.\" The function appeared in 32v, pwb and pwb.2 and in 3bsd 4bsd 71.\" The first man page (or link to a man page that I can find at the 72.\" moment is 4.3... 73.Pp 74The 75.Fn alloca 76function is slightly unsafe because it cannot ensure that the pointer 77returned points to a valid and usable block of memory. 78The allocation made may exceed the bounds of the stack, or even go 79further into other objects in memory, and 80.Fn alloca 81cannot determine such an error. 82Avoid 83.Fn alloca 84with large unbounded allocations. 85