build_bug.h: remove negative-array fallback for BUILD_BUG_ON() (c60d3b79) · Commits · 戴 / test

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 ("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:

Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by:

Kees Cook <keescook@chromium.org> Reviewed-by:

Nick Desaulniers <ndesaulniers@google.com> Tested-by:

Nick Desaulniers <ndesaulniers@google.com> Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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.

Admin message