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authorMasahiro Yamada <yamada.masahiro@socionext.com>2019-02-21 13:13:38 +0900
committerMasahiro Yamada <yamada.masahiro@socionext.com>2019-02-27 21:43:20 +0900
commitb303c6df80c9f8f13785aa83a0471fca7e38b24d (patch)
treee5115e2524486b8633a4d024e9a1d2761f3c181f /init
parentbd55f96fa9fc29702ec30d75a4290bdadb00209d (diff)
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kbuild: compute false-positive -Wmaybe-uninitialized cases in Kconfig
Since -Wmaybe-uninitialized was introduced by GCC 4.7, we have patched various false positives: - commit e74fc973b6e5 ("Turn off -Wmaybe-uninitialized when building with -Os") turned off this option for -Os. - commit 815eb71e7149 ("Kbuild: disable 'maybe-uninitialized' warning for CONFIG_PROFILE_ALL_BRANCHES") turned off this option for CONFIG_PROFILE_ALL_BRANCHES - commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning for "make W=1"") turned off this option for GCC < 4.9 Arnd provided more explanation in https://lkml.org/lkml/2017/3/14/903 I think this looks better by shifting the logic from Makefile to Kconfig. Link: https://github.com/ClangBuiltLinux/linux/issues/350 Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Diffstat (limited to 'init')
-rw-r--r--init/Kconfig17
1 files changed, 17 insertions, 0 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 513fa544a134..ce43083b681d 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -26,6 +26,22 @@ config CLANG_VERSION
config CC_HAS_ASM_GOTO
def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
+config CC_HAS_WARN_MAYBE_UNINITIALIZED
+ def_bool $(cc-option,-Wmaybe-uninitialized)
+ help
+ GCC >= 4.7 supports this option.
+
+config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
+ bool
+ depends on CC_HAS_WARN_MAYBE_UNINITIALIZED
+ default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9
+ help
+ GCC's -Wmaybe-uninitialized is not reliable by definition.
+ Lots of false positive warnings are produced in some cases.
+
+ If this option is enabled, -Wno-maybe-uninitialzed is passed
+ to the compiler to suppress maybe-uninitialized warnings.
+
config CONSTRUCTORS
bool
depends on !UML
@@ -1102,6 +1118,7 @@ config CC_OPTIMIZE_FOR_PERFORMANCE
config CC_OPTIMIZE_FOR_SIZE
bool "Optimize for size"
+ imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
help
Enabling this option will pass "-Os" instead of "-O2" to
your compiler resulting in a smaller kernel.