Messages in this thread Patch in this message | | | From | Rasmus Villemoes <> | Subject | [PATCH] linux/container_of.h: switch to static_assert | Date | Fri, 15 Oct 2021 11:05:30 +0200 |
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_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().
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> --- akpm: This is obviously on top of Andy's kernel.h splitup series, so should go along with those if acked.
include/linux/container_of.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/include/linux/container_of.h b/include/linux/container_of.h index dd56019838c6..2f4944b791b8 100644 --- a/include/linux/container_of.h +++ b/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))); }) -- 2.31.1
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