[src/trunk]: src/share/man/man3 Document __UNCONST and __UNVOLATILE.

[jruoho <jruoho%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f7c52dc8cf5c
branches:  trunk
changeset: 752564:f7c52dc8cf5c
user:      jruoho <jruoho%NetBSD.org@localhost>
date:      Mon Mar 01 13:44:09 2010 +0000

description:
Document __UNCONST and __UNVOLATILE.

XXX: If there is anything to add or correct, please do so!

diffstat:

 share/man/man3/Makefile    |   5 +-
 share/man/man3/__UNCONST.3 |  90 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 93 insertions(+), 2 deletions(-)

diffs (114 lines):

diff -r 9489bd87a215 -r f7c52dc8cf5c share/man/man3/Makefile
--- a/share/man/man3/Makefile   Mon Mar 01 13:16:21 2010 +0000
+++ b/share/man/man3/Makefile   Mon Mar 01 13:44:09 2010 +0000
@@ -1,13 +1,14 @@
-#      $NetBSD: Makefile,v 1.36 2010/02/27 22:04:38 wiz Exp $
+#      $NetBSD: Makefile,v 1.37 2010/03/01 13:44:09 jruoho Exp $
 #      @(#)Makefile    8.2 (Berkeley) 12/13/93
 
-MAN=   _DIAGASSERT.3 CMSG_DATA.3 \
+MAN=   _DIAGASSERT.3 __UNCONST.3 CMSG_DATA.3 \
        assert.3 bits.3 bitstring.3 dlfcn.3 end.3 \
        gcq.3 intro.3 offsetof.3 queue.3 stdarg.3 sysexits.3 \
        timeradd.3 tree.3 varargs.3
 
 USETBL=        # used by queue.3
 
+MLINKS+=__UNCONST.3 __UNVOLATILE.3
 MLINKS+=bitstring.3 bit_alloc.3 \
        bitstring.3 bit_clear.3 \
        bitstring.3 bit_decl.3 \
diff -r 9489bd87a215 -r f7c52dc8cf5c share/man/man3/__UNCONST.3
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/share/man/man3/__UNCONST.3        Mon Mar 01 13:44:09 2010 +0000
@@ -0,0 +1,90 @@
+.\"    $NetBSD: __UNCONST.3,v 1.1 2010/03/01 13:44:09 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 February 28, 2010
+.Os
+.Dt __UNCONST 3
+.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
+a pointer declared with the
+.Em const
+type qualifier is being passed to a function without such qualifier.
+In the same vein, the
+.Fn __UNVOLATILE
+macro can be used to omit warnings related to the
+.Em volatile
+type qualifier.
+.Pp
+.Sh IMPLEMENTATION NOTES
+Both macros are implemented by explicitly using
+.Em unsigned long
+instead of
+.Em intptr_t ,
+a signed type guaranteed to hold a pointer.
+.Sh EXAMPLES
+The following example demonstrates a possible usage of
+.Fn __UNCONST :
+.Bd -literal -offset indent
+const char *str = "/dev/null";
+
+api_function(__UNCONST(str));
+
+\&...
+
+static void
+api_function(char *str)
+{
+       \&...
+
+.Ed
+.Sh CAVEATS
+Both macros should be used with care because these can hide valid errors.
+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 volatile pointer to
+.Xr memset 3 .
+.Sh SEE ALSO
+.Xr cc 1