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

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: default avatarMasahiro Yamada <>
Acked-by: default avatarKees Cook <>
Reviewed-by: default avatarNick Desaulniers <>
Tested-by: default avatarNick Desaulniers <>
Cc: Luc Van Oostenryck <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 3fe5dbfe
......@@ -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)]))
#define BUILD_BUG_ON(condition) \
BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
* BUILD_BUG - break compile if used.
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