Add '-fwrapv' to gcc CFLAGS
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>
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@ -347,6 +347,7 @@ KBUILD_CPPFLAGS := -D__KERNEL__
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KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
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-fno-strict-aliasing -fno-common \
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-Werror-implicit-function-declaration
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KBUILD_CFLAGS += $(call cc-option,-fwrapv)
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KBUILD_AFLAGS := -D__ASSEMBLY__
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# Read KERNELRELEASE from include/config/kernel.release (if it exists)
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