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Commit c60d3b79 authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Linus Torvalds
Browse files

build_bug.h: remove negative-array fallback for BUILD_BUG_ON() 

The kernel can only be compiled with an optimization option (-O2, -Os,
or the currently proposed -Og).  Hence, __OPTIMIZE__ is always defined
in the kernel source.

The fallback for the -O0 case is just hypothetical and pointless.
Moreover, commit 0bb95f80 ("Makefile: Globally enable VLA warning")
enabled -Wvla warning.  The use of variable length arrays is banned.

Link: http://lkml.kernel.org/r/1542856462-18836-2-git-send-email-yamada.masahiro@socionext.com


Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Tested-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3fe5dbfe

include/linux/build_bug.h

+0 −14
Original line number Diff line number Diff line
@@ -51,23 +51,9 @@ 
 * If you have some code which relies on certain constants being equal, or

 * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to

 * detect if someone changes it.

 *

 * The implementation uses gcc's reluctance to create a negative array, but gcc

 * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to

 * inline functions).  Luckily, in 4.3 they added the "error" function

 * attribute just for this type of case.  Thus, we use a negative sized array

 * (should always create an error on gcc versions older than 4.4) and then call

 * an undefined function with the error attribute (should always create an

 * error on gcc 4.3 and later).  If for some reason, neither creates a

 * compile-time error, we'll still have a link-time error, which is harder to

 * track down.

 */

#ifndef __OPTIMIZE__

#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))

#else

#define BUILD_BUG_ON(condition) \

	BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)

#endif



/**

 * BUILD_BUG - break compile if used.