98 lines
3.0 KiB
Groff
98 lines
3.0 KiB
Groff
.\" $NetBSD: STACK.9,v 1.2 2011/04/08 07:55:04 jruoho Exp $
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.\"
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.\" Copyright (c) 2010 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Jukka Ruohonen.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd April 8, 2011
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.Dt STACK 9
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.Os
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.Sh NAME
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.Nm STACK
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.Nd stack macros
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.Sh SYNOPSIS
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.In sys/param.h
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.Ft type
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.Fn STACK_ALLOC "sp" "size"
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.Ft type
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.Fn STACK_MAX "sp" "size"
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.Ft type
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.Fn STACK_ALIGN "sp" "bytes"
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.Ft type
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.Fn STACK_GROW "sp" "size"
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.Ft type
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.Fn STACK_SHRINK "sp" "size"
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.Sh DESCRIPTION
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A stack is an area of memory with a fixed origin but with a variable size.
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A stack pointer points to the most recently referenced location on the stack.
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Initially, when the stack has a size of zero,
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the stack pointer points to the origin of the stack.
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When data items are added to the stack,
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the stack pointer moves away from the origin.
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.Pp
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The
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.Fn STACK_ALLOC
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macro returns a pointer to allocated stack space of some
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.Fa size .
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Given the returned pointer
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.Fa sp
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and
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.Fa size ,
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.Fn STACK_MAX
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returns the maximum stack address of the allocated stack space.
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The
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.Fn STACK_ALIGN
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macro can be used to align the stack pointer
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.Fa sp
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by the specified amount of
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.Fa bytes .
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.Pp
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Two basic operations are common to all stacks:
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a data item is added
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.Pq Dq push
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to the location pointed by
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.Fa sp
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or a data item is removed
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.Pq Dq pop
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from the stack.
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The stack pointer must be subsequently adjusted by the size of the data item.
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The
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.Fn STACK_GROW
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and
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.Fn STACK_SHRINK
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macros adjust the stack pointer
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.Fa sp
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by given
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.Fa size .
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.Pp
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A stack may grow either up or down.
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The described macros take this into account by using the
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.Dv __MACHINE_STACK_GROWS_UP
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preprocessor define.
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.Sh SEE ALSO
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.Xr param 3 ,
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.Xr queue 3
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