84 lines
2.8 KiB
Groff
84 lines
2.8 KiB
Groff
.\" $NetBSD: __UNCONST.3,v 1.5 2010/12/16 10:40:04 jruoho Exp $
|
|
.\"
|
|
.\" Copyright (c) 2010 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to The NetBSD Foundation
|
|
.\" by Jukka Ruohonen.
|
|
.\"
|
|
.\" 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.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
|
|
.\"
|
|
.Dd December 16, 2010
|
|
.Dt __UNCONST 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm __UNCONST
|
|
.Nd compile time cast-away macro
|
|
.Sh SYNOPSIS
|
|
.In sys/cdefs.h
|
|
.Ft void
|
|
.Fn __UNCONST x
|
|
.Ft void
|
|
.Fn __UNVOLATILE x
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn __UNCONST
|
|
macro can be used to omit warnings produced by certain compilers when
|
|
operating with pointers declared with the
|
|
.Em const
|
|
type qualifier in a context without such qualifier.
|
|
Examples include passing a pointer declared with the
|
|
.Em const
|
|
qualifier to a function without such qualifier,
|
|
and variable assignment from a
|
|
.Em const
|
|
pointer to a non-const pointer.
|
|
In the same vein, the
|
|
.Fn __UNVOLATILE
|
|
macro can be used to exclude warnings related to the
|
|
.Em volatile
|
|
type qualifier.
|
|
.Sh IMPLEMENTATION NOTES
|
|
These macros are implemented by explicitly using
|
|
.Em unsigned long
|
|
instead of
|
|
.Em intptr_t ,
|
|
a signed type guaranteed to hold a pointer.
|
|
.Sh SEE ALSO
|
|
.Xr cc 1 ,
|
|
.Xr cdefs 3
|
|
.Sh CAVEATS
|
|
As both macros may hide valid errors, their usage is not recommended
|
|
unless there is a well-thought reason for a cast.
|
|
A typical use case for
|
|
.Fn __UNCONST
|
|
involve an
|
|
.Tn API
|
|
that does not follow the so-called ``const correctness''
|
|
even if it would be appropriate.
|
|
Valid use cases of
|
|
.Fn __UNVOLATILE
|
|
include passing a
|
|
.Em volatile
|
|
pointer to
|
|
.Xr memset 3 .
|