linux-kernel - [PATCH AUTOSEL 5.5 430/542] kbuild: use -S instead of -E for precise cc-option test in Kconfig

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Message-Id: <20200214154854.6746-430-sashal@kernel.org>
Date:   Fri, 14 Feb 2020 10:47:02 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-kbuild@...r.kernel.org
Subject: [PATCH AUTOSEL 5.5 430/542] kbuild: use -S instead of -E for precise cc-option test in Kconfig

From: Masahiro Yamada <masahiroy@...nel.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@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.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