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authorNathan Chancellor <natechancellor@gmail.com>2019-06-11 11:43:31 -0700
committerMasahiro Yamada <yamada.masahiro@socionext.com>2019-06-24 03:43:03 +0900
commit589834b3a0097a4908f4112eac0ca2feb486fa32 (patch)
tree5f8b5daeceedb90db6a58446e4f2247ce8413ddf /Makefile
parente846f0dc57f441e5e93194d39bc9b8ac2ab5e0a4 (diff)
downloadlwn-589834b3a0097a4908f4112eac0ca2feb486fa32.tar.gz
lwn-589834b3a0097a4908f4112eac0ca2feb486fa32.zip
kbuild: Add -Werror=unknown-warning-option to CLANG_FLAGS
In commit ebcc5928c5d9 ("arm64: Silence gcc warnings about arch ABI drift"), the arm64 Makefile added -Wno-psabi to KBUILD_CFLAGS, which is a GCC only option so clang rightfully complains: warning: unknown warning option '-Wno-psabi' [-Wunknown-warning-option] https://clang.llvm.org/docs/DiagnosticsReference.html#wunknown-warning-option However, by default, this is merely a warning so the build happily goes on with a slew of these warnings in the process. Commit c3f0d0bc5b01 ("kbuild, LLVMLinux: Add -Werror to cc-option to support clang") worked around this behavior in cc-option by adding -Werror so that unknown flags cause an error. However, this all happens silently and when an unknown flag is added to the build unconditionally like -Wno-psabi, cc-option will always fail because there is always an unknown flag in the list of flags. This manifested as link time failures in the arm64 libstub because -fno-stack-protector didn't get added to KBUILD_CFLAGS. To avoid these weird cryptic failures in the future, make clang behave like gcc and immediately error when it encounters an unknown flag by adding -Werror=unknown-warning-option to CLANG_FLAGS. This can be added unconditionally for clang because it is supported by at least 3.0.0, according to godbolt [1] and 4.0.0, according to its documentation [2], which is far earlier than we typically support. [1]: https://godbolt.org/z/7F7rm3 [2]: https://releases.llvm.org/4.0.0/tools/clang/docs/DiagnosticsReference.html#wunknown-warning-option Link: https://github.com/ClangBuiltLinux/linux/issues/511 Link: https://github.com/ClangBuiltLinux/linux/issues/517 Suggested-by: Peter Smith <peter.smith@linaro.org> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Diffstat (limited to 'Makefile')
-rw-r--r--Makefile1
1 files changed, 1 insertions, 0 deletions
diff --git a/Makefile b/Makefile
index aefdb5661382..1f35aca4fe05 100644
--- a/Makefile
+++ b/Makefile
@@ -528,6 +528,7 @@ ifneq ($(GCC_TOOLCHAIN),)
CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN)
endif
CLANG_FLAGS += -no-integrated-as
+CLANG_FLAGS += -Werror=unknown-warning-option
KBUILD_CFLAGS += $(CLANG_FLAGS)
KBUILD_AFLAGS += $(CLANG_FLAGS)
export CLANG_FLAGS