The patch titled
Subject: build_bug.h: remove negative-array fallback for BUILD_BUG_ON()
has been added to the -mm tree. Its filename is
build_bugh-remove-negative-array-fallback-for-build_bug_on.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/build_bugh-remove-negative-array-fallback-for-build_bug_on.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/build_bugh-remove-negative-array-fallback-for-build_bug_on.patch
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------------------------------------------------------
From: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Subject: 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 0bb95f80a38f ("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@xxxxxxxxxxxxx
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/build_bug.h~build_bugh-remove-negative-array-fallback-for-build_bug_on
+++ a/include/linux/build_bug.h
@@ -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.
_
Patches currently in -mm which might be from yamada.masahiro@xxxxxxxxxxxxx are
kernelh-disable-type-checks-in-container_of-for-sparse.patch
build_bugh-remove-negative-array-fallback-for-build_bug_on.patch
build_bugh-remove-most-of-dummy-build_bug_on-stubs-for-sparse.patch
