On Sat, Jan 18, 2020 at 2:16 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > 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, when testing "--param asan-instrument-allocas=1", my gcc > gives a different result for -E vs -S. > > $ 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@xxxxxxxxxx> > --- Applied to linux-kbuild. > scripts/Kconfig.include | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include > index d4adfbe42690..bfb44b265a94 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 > -- > 2.17.1 > -- Best Regards Masahiro Yamada
