* [PATCH] linux/container_of.h: switch to static_assert
@ 2021-10-15 9:05 Rasmus Villemoes
2021-10-15 13:08 ` Miguel Ojeda
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Rasmus Villemoes @ 2021-10-15 9:05 UTC (permalink / raw)
To: akpm
Cc: Miguel Ojeda, Andy Shevchenko, Nick Desaulniers,
Rasmus Villemoes, linux-kernel
_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
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] linux/container_of.h: switch to static_assert
2021-10-15 9:05 [PATCH] linux/container_of.h: switch to static_assert Rasmus Villemoes
@ 2021-10-15 13:08 ` Miguel Ojeda
2021-10-15 13:11 ` Andy Shevchenko
2021-10-15 17:33 ` Nick Desaulniers
2 siblings, 0 replies; 6+ messages in thread
From: Miguel Ojeda @ 2021-10-15 13:08 UTC (permalink / raw)
To: Rasmus Villemoes
Cc: Andrew Morton, Andy Shevchenko, Nick Desaulniers, linux-kernel
On Fri, Oct 15, 2021 at 11:05 AM Rasmus Villemoes
<linux@rasmusvillemoes.dk> wrote:
>
> _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.
Thanks for this! Very much in favor!
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Perhaps Andrew may want to add a link to the related discussion
thread: https://lore.kernel.org/lkml/20211014132331.GA4811@kernel.org/T/
Cheers,
Miguel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux/container_of.h: switch to static_assert
2021-10-15 9:05 [PATCH] linux/container_of.h: switch to static_assert Rasmus Villemoes
2021-10-15 13:08 ` Miguel Ojeda
@ 2021-10-15 13:11 ` Andy Shevchenko
2021-10-15 13:13 ` Andy Shevchenko
2021-10-15 17:33 ` Nick Desaulniers
2 siblings, 1 reply; 6+ messages in thread
From: Andy Shevchenko @ 2021-10-15 13:11 UTC (permalink / raw)
To: Rasmus Villemoes; +Cc: akpm, Miguel Ojeda, Nick Desaulniers, linux-kernel
On Fri, Oct 15, 2021 at 11:05:30AM +0200, Rasmus Villemoes wrote:
> _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().
Thanks, Rasmus!
Make sense to me.
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> 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.
Nevertheless, kbuild bot is not happy about bottom_half.h (_RET_IP_, _THIS_IP_
definitions). Do you have any idea what to do the best? (I think those macros
deserve a separate header as well).
--
With Best Regards,
Andy Shevchenko
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux/container_of.h: switch to static_assert
2021-10-15 13:11 ` Andy Shevchenko
@ 2021-10-15 13:13 ` Andy Shevchenko
2021-10-15 11:46 ` Rasmus Villemoes
0 siblings, 1 reply; 6+ messages in thread
From: Andy Shevchenko @ 2021-10-15 13:13 UTC (permalink / raw)
To: Rasmus Villemoes; +Cc: akpm, Miguel Ojeda, Nick Desaulniers, linux-kernel
On Fri, Oct 15, 2021 at 04:11:01PM +0300, Andy Shevchenko wrote:
> On Fri, Oct 15, 2021 at 11:05:30AM +0200, Rasmus Villemoes wrote:
> > _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().
>
> Thanks, Rasmus!
> Make sense to me.
Btw, shouldn't we also remove build_bug.h in the container_of.h with this?
(Or if this goes first, do we still need bug.h?)
--
With Best Regards,
Andy Shevchenko
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux/container_of.h: switch to static_assert
2021-10-15 13:13 ` Andy Shevchenko
@ 2021-10-15 11:46 ` Rasmus Villemoes
0 siblings, 0 replies; 6+ messages in thread
From: Rasmus Villemoes @ 2021-10-15 11:46 UTC (permalink / raw)
To: Andy Shevchenko; +Cc: akpm, Miguel Ojeda, Nick Desaulniers, linux-kernel
On 15/10/2021 15.13, Andy Shevchenko wrote:
> Btw, shouldn't we also remove build_bug.h in the container_of.h with this?
> (Or if this goes first, do we still need bug.h?)
>
We absolutely need build_bug.h, as that is where static_assert is defined.
container_of.h doesn't include bug.h AFAICT, nor should it need to.
(We should still find a quiet place for __same_type and have
container_of include that header, but that's unrelated to this patch.)
Rasmus
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux/container_of.h: switch to static_assert
2021-10-15 9:05 [PATCH] linux/container_of.h: switch to static_assert Rasmus Villemoes
2021-10-15 13:08 ` Miguel Ojeda
2021-10-15 13:11 ` Andy Shevchenko
@ 2021-10-15 17:33 ` Nick Desaulniers
2 siblings, 0 replies; 6+ messages in thread
From: Nick Desaulniers @ 2021-10-15 17:33 UTC (permalink / raw)
To: Rasmus Villemoes; +Cc: akpm, Miguel Ojeda, Andy Shevchenko, linux-kernel
On Fri, Oct 15, 2021 at 2:05 AM Rasmus Villemoes
<linux@rasmusvillemoes.dk> wrote:
>
> _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>
Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> 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
>
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 6+ messages in thread
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2021-10-15 9:05 [PATCH] linux/container_of.h: switch to static_assert Rasmus Villemoes
2021-10-15 13:08 ` Miguel Ojeda
2021-10-15 13:11 ` Andy Shevchenko
2021-10-15 13:13 ` Andy Shevchenko
2021-10-15 11:46 ` Rasmus Villemoes
2021-10-15 17:33 ` Nick Desaulniers
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