From: Masahiro Yamada <masahiroy@kernel.org>
Date: Fri, 17 Jan 2020 17:14:35 +0000 (+0900)
Subject: kbuild: use -S instead of -E for precise cc-option test in Kconfig
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=3bed1b7b9d79ca40e41e3af130931a3225e951a3;p=linux.git

kbuild: use -S instead of -E for precise cc-option test in Kconfig

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>
---

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