Commit 3bed1b7b authored Jan 18, 2020 by Masahiro Yamada

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>

parent 1a7f0a34

scripts/Kconfig.include

+1 −1

Original line number	Diff line number	Diff line
		@@ -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

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