minix/lib/libc/stdlib/alloca.3
Ben Gras 2fe8fb192f Full switch to clang/ELF. Drop ack. Simplify.
There is important information about booting non-ack images in
docs/UPDATING. ack/aout-format images can't be built any more, and
booting clang/ELF-format ones is a little different. Updating to the
new boot monitor is recommended.

Changes in this commit:

	. drop boot monitor -> allowing dropping ack support
	. facility to copy ELF boot files to /boot so that old boot monitor
	  can still boot fairly easily, see UPDATING
	. no more ack-format libraries -> single-case libraries
	. some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases
	. drop several ack toolchain commands, but not all support
	  commands (e.g. aal is gone but acksize is not yet).
	. a few libc files moved to netbsd libc dir
	. new /bin/date as minix date used code in libc/
	. test compile fix
	. harmonize includes
	. /usr/lib is no longer special: without ack, /usr/lib plays no
	  kind of special bootstrapping role any more and bootstrapping
	  is done exclusively through packages, so releases depend even
	  less on the state of the machine making them now.
	. rename nbsd_lib* to lib*
	. reduce mtree
2012-02-14 14:52:02 +01:00

102 lines
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Groff

.\" $NetBSD: alloca.3,v 1.13 2010/05/03 06:11:38 jruoho Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" 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.
.\" 3. 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.
.\"
.\" from: @(#)alloca.3 8.1 (Berkeley) 6/4/93
.\"
.Dd May 3, 2010
.Dt ALLOCA 3
.Os
.Sh NAME
.Nm alloca
.Nd memory allocator
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft void *
.Fn alloca "size_t size"
.Sh DESCRIPTION
The
.Fn alloca
function
allocates
.Fa size
bytes of space in the stack frame of the caller.
This temporary space is automatically freed on
return.
.Sh RETURN VALUES
The
.Fn alloca
function returns a pointer to the beginning of the allocated space.
If the allocation failed, a
.Dv NULL
pointer is returned.
.Sh SEE ALSO
.Xr brk 2 ,
.Xr calloc 3 ,
.Xr getpagesize 3 ,
.Xr malloc 3 ,
.Xr realloc 3
.Sh CAVEATS
Few limitations can be mentioned:
.Bl -bullet
.It
The
.Fn alloca
function
is machine dependent; its use is discouraged.
.It
The
.Fn alloca
function 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.
.It
Since
.Fn alloca
modifies the stack at runtime,
it causes problems to certain security features.
See
.Xr security 8
for a discussion.
.El
.\" .Sh HISTORY
.\" The
.\" .Fn alloca
.\" function appeared in
.\" .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...