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| author | pfg <pfg@FreeBSD.org> | 2015-05-14 15:49:48 +0000 |
|---|---|---|
| committer | pfg <pfg@FreeBSD.org> | 2015-05-14 15:49:48 +0000 |
| commit | f7984cfbeee89ab50566d7d09e6d0238505f0a83 (patch) | |
| tree | 2911157c89ddf65d9209ac5640b0e5ba973d3c58 /sys/sys/cdefs.h | |
| parent | 1288a9c61937a95d6586948da68c17b9b867bee3 (diff) | |
| download | FreeBSD-src-f7984cfbeee89ab50566d7d09e6d0238505f0a83.zip FreeBSD-src-f7984cfbeee89ab50566d7d09e6d0238505f0a83.tar.gz | |
Add new __unreachable() builtin
This is one of the few post gcc4.2 builtins that has been implemented by
clang:
__builtin_unreachable is used to indicate that a specific point in the
program cannot be reached, even if the compiler might otherwise think it
can. This is useful to improve optimization and eliminates certain
warnings.
Hinted by: NetBSD
Differential Revision: https://reviews.freebsd.org/D2536
Diffstat (limited to 'sys/sys/cdefs.h')
| -rw-r--r-- | sys/sys/cdefs.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h index a7286ab..73734cb 100644 --- a/sys/sys/cdefs.h +++ b/sys/sys/cdefs.h @@ -388,6 +388,12 @@ #define __alloc_size(x) #endif +#if __has_builtin(__builtin_unreachable) || __GNUC_PREREQ__(4, 6) +#define __unreachable() __builtin_unreachable() +#else +#define __unreachable() do {} while (/*CONSTCOND*/0) +#endif + #if __has_attribute(alloc_align) || __GNUC_PREREQ__(4, 9) #define __alloc_align(x) __attribute__((__alloc_align__(x))) #else |
