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    Subject[PATCH 5.4 273/344] kbuild: use -S instead of -E for precise cc-option test in Kconfig
    Date
    From: Masahiro Yamada <masahiroy@kernel.org>

    [ Upstream commit 3bed1b7b9d79ca40e41e3af130931a3225e951a3 ]

    Currently, -E (stop after the preprocessing stage) is used to check
    whether the given compiler flag is supported.

    While it is faster than -S (or -c), it can be false-positive. You need
    to run the compilation proper to check the flag more precisely.

    For example, -E and -S disagree about the support of
    "--param asan-instrument-allocas=1".

    $ gcc -Werror --param asan-instrument-allocas=1 -E -x c /dev/null -o /dev/null
    $ echo $?
    0

    $ gcc -Werror --param asan-instrument-allocas=1 -S -x c /dev/null -o /dev/null
    cc1: error: invalid --param name ‘asan-instrument-allocas’; did you mean ‘asan-instrument-writes’?
    $ echo $?
    1

    Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
    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 d4adfbe426903..bfb44b265a948 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 $(CLANG_FLAGS) $(1) -E -x c /dev/null -o /dev/null)
    +cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -S -x c /dev/null -o /dev/null)

    # $(ld-option,<flag>)
    # Return y if the linker supports <flag>, n otherwise
    --
    2.20.1


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