[src/trunk]: src/sys/sys Add an __UNVOLATILE() macro. It should be used with...

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

details:   https://anonhg.NetBSD.org/src/rev/f3eae6475b54
branches:  trunk
changeset: 581548:f3eae6475b54
user:      he <he%NetBSD.org@localhost>
date:      Thu Jun 02 14:31:38 2005 +0000

description:
Add an __UNVOLATILE() macro.  It should be used with caution, but
it is required to use this whenever you want to pass a pointer to
volatile data e.g. to memset().  This allows us to still compile
files doing such things with -Wcast-qual and get the rest of the
code checked under that option.

Based on suggestions from tron and christos.

diffstat:

 sys/sys/cdefs.h |  11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diffs (25 lines):

diff -r 3f49afdb6038 -r f3eae6475b54 sys/sys/cdefs.h
--- a/sys/sys/cdefs.h   Thu Jun 02 14:29:02 2005 +0000
+++ b/sys/sys/cdefs.h   Thu Jun 02 14:31:38 2005 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: cdefs.h,v 1.58 2004/12/11 05:59:00 christos Exp $      */
+/*     $NetBSD: cdefs.h,v 1.59 2005/06/02 14:31:38 he Exp $    */
 
 /*
  * Copyright (c) 1991, 1993
@@ -147,6 +147,15 @@
 #define __UNCONST(a)   ((void *)(unsigned long)(const void *)(a))
 
 /*
+ * The following macro is used to remove the volatile cast-away warnings
+ * from gcc -Wcast-qual; as above it should be used with caution
+ * because it can hide valid errors or warnings.  Valid uses include
+ * making it possible to pass a volatile pointer to memset().
+ * For the same reasons as above, we use unsigned long and not intptr_t.
+ */
+#define __UNVOLATILE(a)        ((void *)(unsigned long)(volatile void *)(a))
+
+/*
  * GCC2 provides __extension__ to suppress warnings for various GNU C
  * language extensions under "-ansi -pedantic".
  */