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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd September 5, 2006 29.Dt ALLOCA 3 30.Os 31.Sh NAME 32.Nm alloca 33.Nd memory allocator 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In stdlib.h 38.Ft void * 39.Fn alloca "size_t size" 40.Sh DESCRIPTION 41The 42.Fn alloca 43function 44allocates 45.Fa size 46bytes of space in the stack frame of the caller. 47This temporary space is automatically freed on 48return. 49.Sh RETURN VALUES 50The 51.Fn alloca 52function returns a pointer to the beginning of the allocated space. 53.Sh SEE ALSO 54.Xr brk 2 , 55.Xr calloc 3 , 56.Xr getpagesize 3 , 57.Xr malloc 3 , 58.Xr realloc 3 59.Sh HISTORY 60The 61.Fn alloca 62function appeared in 63.At 32v . 64.\" .Bx ?? . 65.\" The function appeared in 32v, pwb and pwb.2 and in 3bsd 4bsd 66.\" The first man page (or link to a man page that I can find at the 67.\" moment is 4.3... 68.Sh BUGS 69The 70.Fn alloca 71function 72is machine and compiler dependent; 73its use is discouraged. 74.Pp 75The 76.Fn alloca 77function is slightly unsafe because it cannot ensure that the pointer 78returned points to a valid and usable block of memory. 79The allocation made may exceed the bounds of the stack, or even go 80further into other objects in memory, and 81.Fn alloca 82cannot determine such an error. 83Avoid 84.Fn alloca 85with large unbounded allocations. 86