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LinuxKPI: change BUILD_BUG_ON()

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BUILD_BUG_ON() can be used inside functions where the definition to
CTASSERT() (_Static_assert()) seems to not work.
Go back to an old-style CTASSERT() implementation but also add a
variable dclaration to avoid "unsued typedef" errors and dummy-use
the variable to avoid "unusued variable" errors.  Given it is all
self-contained in a block and not used outside this should be
optimised away.

Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Reviewed by:	hselasky
Differential Revision: https://reviews.freebsd.org/D30431
This commit is contained in:
Bjoern A. Zeeb 2021-05-24 18:26:41 +00:00
parent 18d303b05f
commit 1082490cd8
1 changed files with 16 additions and 1 deletions
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17
sys/compat/linuxkpi/common/include/linux/kernel.h
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@ -89,8 +89,23 @@
#define S64_C(x) x ## LL
#define U64_C(x) x ## ULL
/*
* BUILD_BUG_ON() can happen inside functions where _Static_assert() does not
* seem to work. Use old-schoold-ish CTASSERT from before commit
* a3085588a88fa58eb5b1eaae471999e1995a29cf but also make sure we do not
* end up with an unused typedef or variable. The compiler should optimise
* it away entirely.
*/
#define _O_CTASSERT(x) _O__CTASSERT(x, __LINE__)
#define _O__CTASSERT(x, y) _O___CTASSERT(x, y)
#define _O___CTASSERT(x, y) while (0) { \
typedef char __assert_line_ ## y[(x) ? 1 : -1]; \
__assert_line_ ## y _x; \
_x[0] = '\0'; \
}
#define BUILD_BUG() do { CTASSERT(0); } while (0)
#define BUILD_BUG_ON(x) CTASSERT(!(x))
#define BUILD_BUG_ON(x) _O_CTASSERT(!(x))
#define BUILD_BUG_ON_MSG(x, msg) BUILD_BUG_ON(x)
#define BUILD_BUG_ON_NOT_POWER_OF_2(x) BUILD_BUG_ON(!powerof2(x))
#define BUILD_BUG_ON_INVALID(expr) while (0) { (void)(expr); }