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| author |   Vincent Mailhol <mailhol.vincent@wanadoo.fr> | 2025-03-29 01:48:50 +0900 |
|---|---|---|
| committer |   Yury Norov <yury.norov@gmail.com> | 2025-04-29 15:58:38 -0400 |
| commit | 243c90e917f5cfc99821e5104d1c8a81c11cda4c (patch) | |
| tree | 2abb577edd3b6cd38d429432e646a9bd303f56ab /include/linux/compiler.h | |
| parent | test_bits: add tests for BIT_U*() (diff) | |
| download | linux-rng-243c90e917f5cfc99821e5104d1c8a81c11cda4c.tar.xz linux-rng-243c90e917f5cfc99821e5104d1c8a81c11cda4c.zip | |
build_bug.h: more user friendly error messages in BUILD_BUG_ON_ZERO()
__BUILD_BUG_ON_ZERO_MSG(), as introduced in [1], makes it possible to
do a static assertions in expressions. The direct benefit is to
provide a meaningful error message instead of the cryptic negative
bitfield size error message currently returned by BUILD_BUG_ON_ZERO():
./include/linux/build_bug.h:16:51: error: negative width in bit-field '<anonymous>'
16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
| ^
Get rid of BUILD_BUG_ON_ZERO()'s bitfield size hack. Instead rely on
__BUILD_BUG_ON_ZERO_MSG() which in turn relies on C11's
_Static_assert().
Use some macro magic, similarly to static_assert(), to either use an
optional error message provided by the user or, when omitted, to
produce a default error message by stringifying the tested
expression. With this, for example:
BUILD_BUG_ON_ZERO(1 > 0)
would now throw:
./include/linux/compiler.h:197:62: error: static assertion failed: "1 > 0 is true"
197 | define __BUILD_BUG_ON_ZERO_MSG(e, msg) ((int)sizeof(struct {_Static_assert(!(e), msg);}))
| ^~~~~~~~~~~~~~
Finally, __BUILD_BUG_ON_ZERO_MSG() is already guarded by an:
#ifdef __CHECKER__
So no need any more for that guard clause for BUILD_BUG_ON_ZERO().
Remove it.
[1] commit d7a516c6eeae ("compiler.h: Fix undefined BUILD_BUG_ON_ZERO()")
Link: https://git.kernel.org/torvalds/c/d7a516c6eeae
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://git.kernel.org/next/linux-next/c/b88937277df
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 27725f1ab5ab..6f04a1d8c720 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -192,9 +192,9 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, }) #ifdef __CHECKER__ -#define __BUILD_BUG_ON_ZERO_MSG(e, msg) (0) +#define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) (0) #else /* __CHECKER__ */ -#define __BUILD_BUG_ON_ZERO_MSG(e, msg) ((int)sizeof(struct {_Static_assert(!(e), msg);})) +#define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) ((int)sizeof(struct {_Static_assert(!(e), msg);})) #endif /* __CHECKER__ */ /* &a[0] degrades to a pointer: a different type from an array */ |