From: Stephen Boyd swboyd@chromium.org
[ Upstream commit e8de12fb7cde2c85bc31097cd098da79a4818305 ]
If the particular version of clang a user has doesn't enable -Werror=unknown-warning-option by default, even though it is the default[1], then make sure to pass the option to the Kconfig cc-option command so that testing options from Kconfig files works properly. Otherwise, depending on the default values setup in the clang toolchain we will silently assume options such as -Wmaybe-uninitialized are supported by clang, when they really aren't.
A compilation issue only started happening for me once commit 589834b3a009 ("kbuild: Add -Werror=unknown-warning-option to CLANG_FLAGS") was applied on top of commit b303c6df80c9 ("kbuild: compute false-positive -Wmaybe-uninitialized cases in Kconfig"). This leads kbuild to try and test for the existence of the -Wmaybe-uninitialized flag with the cc-option command in scripts/Kconfig.include, and it doesn't see an error returned from the option test so it sets the config value to Y. Then the Makefile tries to pass the unknown option on the command line and -Werror=unknown-warning-option catches the invalid option and breaks the build. Before commit 589834b3a009 ("kbuild: Add -Werror=unknown-warning-option to CLANG_FLAGS") the build works fine, but any cc-option test of a warning option in Kconfig files silently evaluates to true, even if the warning option flag isn't supported on clang.
Note: This doesn't change cc-option usages in Makefiles because those use a different rule that includes KBUILD_CFLAGS by default (see the __cc-option command in scripts/Kbuild.incluide). The KBUILD_CFLAGS variable already has the -Werror=unknown-warning-option flag set. Thanks to Doug for pointing out the different rule.
[1] https://clang.llvm.org/docs/DiagnosticsReference.html#wunknown-warning-optio... Cc: Peter Smith peter.smith@linaro.org Cc: Nick Desaulniers ndesaulniers@google.com Cc: Douglas Anderson dianders@chromium.org Signed-off-by: Stephen Boyd swboyd@chromium.org Reviewed-by: Nathan Chancellor natechancellor@gmail.com Signed-off-by: Masahiro Yamada yamada.masahiro@socionext.com Signed-off-by: Sasha Levin sashal@kernel.org --- scripts/Kconfig.include | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include index 8a5c4d645eb14..4bbf4fc163a29 100644 --- a/scripts/Kconfig.include +++ b/scripts/Kconfig.include @@ -25,7 +25,7 @@ failure = $(if-success,$(1),n,y)
# $(cc-option,<flag>) # Return y if the compiler supports <flag>, n otherwise -cc-option = $(success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null) +cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -E -x c /dev/null -o /dev/null)
# $(ld-option,<flag>) # Return y if the linker supports <flag>, n otherwise