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Add '-fwrapv' to gcc CFLAGS

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This makes sure that gcc doesn't try to optimize away wrapping
arithmetic, which the kernel occasionally uses for overflow testing, ie
things like

	if (ptr + offset < ptr)

which technically is undefined for non-unsigned types. See

	http://bugzilla.kernel.org/show_bug.cgi?id=12597

for details.

Not all versions of gcc support it, so we need to make it conditional
(it looks like it was introduced in gcc-3.4).

Reminded-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2009-03-19 11:10:17 -07:00
parent a1e4ee2286
commit 68df3755e3
1 changed files with 1 additions and 0 deletions
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Makefile
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@ -347,6 +347,7 @@ KBUILD_CPPFLAGS := -D__KERNEL__
KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \ KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
-fno-strict-aliasing -fno-common \ -fno-strict-aliasing -fno-common \
-Werror-implicit-function-declaration -Werror-implicit-function-declaration
KBUILD_CFLAGS += $(call cc-option,-fwrapv)
KBUILD_AFLAGS := -D__ASSEMBLY__ KBUILD_AFLAGS := -D__ASSEMBLY__
# Read KERNELRELEASE from include/config/kernel.release (if it exists) # Read KERNELRELEASE from include/config/kernel.release (if it exists)