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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 commit589834b3a0("kbuild: Add -Werror=unknown-warning-option to CLANG_FLAGS") was applied on top of commitb303c6df80("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 commit589834b3a0("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-option 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>
40 lines
1.2 KiB
Plaintext
40 lines
1.2 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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# Kconfig helper macros
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# Convenient variables
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comma := ,
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quote := "
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squote := '
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empty :=
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space := $(empty) $(empty)
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dollar := $
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right_paren := )
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left_paren := (
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# $(if-success,<command>,<then>,<else>)
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# Return <then> if <command> exits with 0, <else> otherwise.
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if-success = $(shell,{ $(1); } >/dev/null 2>&1 && echo "$(2)" || echo "$(3)")
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# $(success,<command>)
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# Return y if <command> exits with 0, n otherwise
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success = $(if-success,$(1),y,n)
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# $(failure,<command>)
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# Return n if <command> exits with 0, y otherwise
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failure = $(if-success,$(1),n,y)
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# $(cc-option,<flag>)
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# Return y if the compiler supports <flag>, n otherwise
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cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -E -x c /dev/null -o /dev/null)
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# $(ld-option,<flag>)
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# Return y if the linker supports <flag>, n otherwise
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ld-option = $(success,$(LD) -v $(1))
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# check if $(CC) and $(LD) exist
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$(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
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$(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
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# gcc version including patch level
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gcc-version := $(shell,$(srctree)/scripts/gcc-version.sh $(CC))
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