On Wed, Aug 31, 2022 at 11:44:05AM -0700, Nick Desaulniers wrote: > as-instr uses KBUILD_AFLAGS, but as-option uses KBUILD_CFLAGS. This can > cause as-option to fail unexpectedly because clang will emit > -Werror,-Wunused-command-line-argument for various -m and -f flags for > assembler sources. Now that I am looking closer at it, where does that '-Werror' come from? For cc-option, we add it to elevate clang's warnings about unused '-f', '-m', and '-W' flags to errors so that we do not add those flags. However, I do not see '-Werror' in as-option. I am going to assume it came from CONFIG_WERROR, as I believe Android has that turned on by default. I think that is the real problem: without '-Werror', the only error that should come from as-option is when an option isn't supported by the assembler, as clang will still warn but those will not be fatal but with '-Werror', those warnings turn fatal, causing all subsequent as-option calls to fail. Do not get me wrong, I still believe this is the correct fix but I think it would be good to describe exactly under which conditions this is a real issue in case we ever have to revisit this. > Callers of as-option (and as-instr) likely want to be adding flags to > KBUILD_AFLAGS/aflags-y, not KBUILD_CFLAGS/cflags-y. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1699 > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Regardless of changes to the commit message: Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx> > --- > Changes v1 -> v2: > * Split off changes to arch/x86/boot/compressed/Makefile into parent > patch, as per Masahiro. > > scripts/Makefile.compiler | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler > index 94d0d40cddb3..d1739f0d3ce3 100644 > --- a/scripts/Makefile.compiler > +++ b/scripts/Makefile.compiler > @@ -29,13 +29,13 @@ try-run = $(shell set -e; \ > fi) > > # as-option > -# Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,) > +# Usage: aflags-y += $(call as-option,-Wa$(comma)-isa=foo,) > > as-option = $(call try-run,\ > - $(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2)) > + $(CC) $(KBUILD_AFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2)) > > # as-instr > -# Usage: cflags-y += $(call as-instr,instr,option1,option2) > +# Usage: aflags-y += $(call as-instr,instr,option1,option2) > > as-instr = $(call try-run,\ > printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3)) > -- > 2.37.2.672.g94769d06f0-goog >
