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author | Konstantin Khlebnikov <khlebnikov@openvz.org> | 2012-05-29 15:06:27 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-05-29 16:22:20 -0700 |
commit | baf05aa9271bdbc07d3160035a231abc5fbd429a (patch) | |
tree | 201c4f1df332fa2baef4ddfeda6806faf9e2dbc8 /include/linux | |
parent | 5febcbe99d4766cc383909c447e002e63d8b4592 (diff) | |
download | linux-stable-baf05aa9271bdbc07d3160035a231abc5fbd429a.tar.gz linux-stable-baf05aa9271bdbc07d3160035a231abc5fbd429a.tar.bz2 linux-stable-baf05aa9271bdbc07d3160035a231abc5fbd429a.zip |
bug: introduce BUILD_BUG_ON_INVALID() macro
Sometimes we want to check some expressions correctness at compile time.
"(void)(e);" or "if (e);" can be dangerous if the expression has
side-effects, and gcc sometimes generates a lot of code, even if the
expression has no effect.
This patch introduces macro BUILD_BUG_ON_INVALID() for such checks, it
forces a compilation error if expression is invalid without any extra
code.
[Cast to "long" required because sizeof does not work for bit-fields.]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r-- | include/linux/bug.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/bug.h b/include/linux/bug.h index 72961c39576a..aaac4bba6f5c 100644 --- a/include/linux/bug.h +++ b/include/linux/bug.h @@ -30,6 +30,13 @@ struct pt_regs; #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); })) #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); })) +/* + * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the + * expression but avoids the generation of any code, even if that expression + * has side-effects. + */ +#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) + /** * BUILD_BUG_ON - break compile if a condition is true. * @condition: the condition which the compiler should know is false. |