[src/riastradh-drm2]: src/sys/external/bsd/drm2/include/linux Make container_...

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

details:   https://anonhg.NetBSD.org/src/rev/2228fc5614b2
branches:  riastradh-drm2
changeset: 788230:2228fc5614b2
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Wed Jul 24 02:49:52 2013 +0000

description:
Make container_of type-safe with the help of a judicious sizeof.

Still avoids multiple evaluation of the pointer operand expression.

diffstat:

 sys/external/bsd/drm2/include/linux/kernel.h |  7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diffs (21 lines):

diff -r 1b7dc7099157 -r 2228fc5614b2 sys/external/bsd/drm2/include/linux/kernel.h
--- a/sys/external/bsd/drm2/include/linux/kernel.h      Wed Jul 24 02:49:35 2013 +0000
+++ b/sys/external/bsd/drm2/include/linux/kernel.h      Wed Jul 24 02:49:52 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kernel.h,v 1.1.2.10 2013/07/24 02:28:07 riastradh Exp $        */
+/*     $NetBSD: kernel.h,v 1.1.2.11 2013/07/24 02:49:52 riastradh Exp $        */
 
 /*-
  * Copyright (c) 2013 The NetBSD Foundation, Inc.
@@ -41,7 +41,10 @@
 #define        unlikely(X)     __predict_false(X)
 
 #define        container_of(PTR, TYPE, FIELD)                                  \
-       ((TYPE *)(((char *)(PTR)) - offsetof(TYPE, FIELD)))
+       ((void)sizeof((PTR) -                                           \
+               &((TYPE *)(((char *)(PTR)) -                            \
+                   offsetof(TYPE, FIELD)))->FIELD),                    \
+           ((TYPE *)(((char *)(PTR)) - offsetof(TYPE, FIELD))))
 
 #define        ARRAY_SIZE(ARRAY)       __arraycount(ARRAY)