.\" 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. .\" 4. 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. .\" .\" 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 .\" $FreeBSD: src/lib/libc/stdlib/alloca.3,v 1.13 2007/01/09 00:28:09 imp Exp $ .\" .Dd September 5, 2006 .Dt ALLOCA 3 .Os .Sh NAME .Nm alloca .Nd memory allocator .Sh SYNOPSIS .In alloca.h or .br .In stdlib.h .Ft void * .Fn alloca "size_t size" .Sh DESCRIPTION The .Fn alloca macro allocates .Fa size bytes of space in the stack frame of the caller. This temporary space is automatically freed on return. .Sh RETURN VALUES .Fn alloca 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 .Fn alloca 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 .Fn alloca is machine and compiler dependent; its use is discouraged. .Pp .Fn alloca 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. .Pp The use of C99 variable-length arrays and .Fn alloca in the same function will cause the lifetime of alloca's storage to be limited to the block containing the .Fn alloca