84d9c625bf
- Fix for possible unset uid/gid in toproto
- Fix for default mtree style
- Update libelf
- Importing libexecinfo
- Resynchronize GCC, mpc, gmp, mpfr
- build.sh: Replace params with show-params.
This has been done as the make target has been renamed in the same
way, while a new target named params has been added. This new
target generates a file containing all the parameters, instead of
printing it on the console.
- Update test48 with new etc/services (Fix by Ben Gras <ben@minix3.org)
get getservbyport() out of the inner loop
Change-Id: Ie6ad5226fa2621ff9f0dee8782ea48f9443d2091
121 lines
3.7 KiB
Groff
121 lines
3.7 KiB
Groff
.\" $NetBSD: alloca.3,v 1.16 2012/10/24 22:56:27 wiz Exp $
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.\"
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.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" from: @(#)alloca.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd October 24, 2012
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.Dt ALLOCA 3
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.Os
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.Sh NAME
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.Nm alloca
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.Nd memory allocator
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.Ft void *
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.Fn alloca "size_t size"
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.Sh DESCRIPTION
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The
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.Fn alloca
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function
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allocates
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.Fa size
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bytes of space in the stack frame of the caller.
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This temporary space is automatically freed on
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return.
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.Sh RETURN VALUES
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The
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.Fn alloca
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function returns a pointer to the beginning of the allocated space.
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If the allocation failed, a
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.Dv NULL
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pointer is returned.
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.Sh SEE ALSO
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.Xr cc 1 ,
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.Xr brk 2 ,
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.Xr calloc 3 ,
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.Xr getpagesize 3 ,
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.Xr malloc 3 ,
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.Xr realloc 3 ,
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.Xr security 7
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.Sh CAVEATS
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Few limitations can be mentioned:
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.Bl -bullet
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.It
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The
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.Fn alloca
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function is not part of any C standard and its use is not portable.
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.It
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The
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.Fn alloca
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function should be supplied by the compiler because the compiler is allowed to
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make assumptions about the stack and frame pointers.
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The libc
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.Fn alloca
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implementation cannot account for those assumptions.
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While there is a
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machine dependent implementation of
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.Fn alloca
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in libc, its use is discouraged and in most cases it will not work.
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Using this implementation will produce linker warnings.
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.It
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The
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.Fn alloca
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function is unsafe because it cannot ensure that the pointer
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returned points to a valid and usable block of memory.
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The allocation made may exceed the bounds of the stack, or even go
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further into other objects in memory, and
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.Fn alloca
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cannot determine such an error.
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For that all
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.Fn alloca
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allocations should be bounded and limited to a small size.
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.It
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Since
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.Fn alloca
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modifies the stack at runtime and the stack usage of each function frame
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cannot be predicted, it makes many compiler security features
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(such as
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.Xr cc 1
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.Fl fstack-protector )
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useless for the calling function.
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See
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.Xr security 7
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for a discussion.
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.El
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.\" .Sh HISTORY
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.\" The
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.\" .Fn alloca
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.\" function appeared in
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.\" .Bx ?? .
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.\" The function appeared in 32v, pwb and pwb.2 and in 3bsd 4bsd
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.\" The first man page (or link to a man page that I can find at the
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.\" moment is 4.3...
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