diff mbox series

[26/87] linux/container_of.h: switch to static_assert

Message ID 20211109023246.wjhHbi8dH%akpm@linux-foundation.org (mailing list archive)
State New
Headers show
Series [01/87] vfs: keep inodes with page cache off the inode shrinker LRU | expand

Commit Message

Andrew Morton Nov. 9, 2021, 2:32 a.m. UTC 
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: linux/container_of.h: switch to static_assert

_Static_assert() is evaluated already in the compiler's frontend, and
gives a somehat more to-the-point error, compared to the BUILD_BUG_ON
macro, which only fires after the optimizer has had a chance to eliminate
calls to functions marked with __attribute__((error)).  In theory, this
might make builds a tiny bit faster.

There's also a little less gunk in the error message emitted:

lib/sort.c: In function `foo':
./include/linux/build_bug.h:78:41: error: static assertion failed: "pointer type mismatch in container_of()"
   78 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)

compared to

lib/sort.c: In function `foo':
././include/linux/compiler_types.h:322:38: error: call to `__compiletime_assert_2' declared with attribute error: pointer type mismatch in container_of()
  322 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)

While at it, fix the copy-pasto in container_of_safe().

Link: https://lkml.kernel.org/r/20211015090530.2774079-1-linux@rasmusvillemoes.dk
Link: https://lore.kernel.org/lkml/20211014132331.GA4811@kernel.org/T/
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/container_of.h |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)
diff mbox series

Patch

--- a/include/linux/container_of.h~linux-container_ofh-switch-to-static_assert
+++ a/include/linux/container_of.h
@@ -16,9 +16,9 @@ 
  */
 #define container_of(ptr, type, member) ({				\
 	void *__mptr = (void *)(ptr);					\
-	BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) &&	\
-			 !__same_type(*(ptr), void),			\
-			 "pointer type mismatch in container_of()");	\
+	static_assert(__same_type(*(ptr), ((type *)0)->member) ||	\
+		      __same_type(*(ptr), void),			\
+		      "pointer type mismatch in container_of()");	\
 	((type *)(__mptr - offsetof(type, member))); })
 
 /**
@@ -31,9 +31,9 @@ 
  */
 #define container_of_safe(ptr, type, member) ({				\
 	void *__mptr = (void *)(ptr);					\
-	BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) &&	\
-			 !__same_type(*(ptr), void),			\
-			 "pointer type mismatch in container_of()");	\
+	static_assert(__same_type(*(ptr), ((type *)0)->member) ||	\
+		      __same_type(*(ptr), void),			\
+		      "pointer type mismatch in container_of_safe()");	\
 	IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) :			\
 		((type *)(__mptr - offsetof(type, member))); })