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>
# $(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