Re: [PATCH 1/2] kbuild: refactor scripts/Makefile.extrawarn
From: Masahiro Yamada
Date: Thu Aug 29 2019 - 13:56:57 EST
On Wed, Aug 28, 2019 at 11:19 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> On Wed, Aug 28, 2019 at 9:20 AM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> > On Wed, Aug 28, 2019 at 7:55 AM Masahiro Yamada
> > <yamada.masahiro@xxxxxxxxxxxxx> wrote:
> > >
> > > Instead of the warning- magic, let's accumulate compiler options
> > > to KBUILD_CFLAGS directly as the top Makefile does. I think this makes
> > > easier to understand what is going on in this file.
> > >
> > > This commit slightly changes the behavior, I think all of which are OK.
> > >
> > >  Currently, cc-option calls are needlessly evaluated. For example,
> > > warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
> > > needs evaluating only when W=3, but it is actually evaluated for
> > > W=1, W=2 as well. With this commit, only relevant cc-option calls
> > > will be evaluated. This is a slight optimization.
> > >
> > >  Currently, unsupported level like W=4 is checked by:
> > > $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
> > > This will no longer be checked, but I do not think it is a big
> > > deal.
> > >
> > Hi Masahiro Yamada,
> > thanks for your patch series.
> > If KBUILD_ENABLE_EXTRA_GCC_CHECKS does extra(-warning)-checks for GCC and Clang,
> > please rename the Kconfig into...
You repeatedly mentioned "Kconfig" in your posts,
where there is nothing related to Kconfig.
> > KBUILD_ENABLE_EXTRA_CC_CHECKS
You missed the fact this is already used
not only for C compilers, but also for Device Tree compiler.
One more thing, this is the environment variable
that Kbuild officially supports.
Keeping the backward compatibility is must.
When I mentioned to rename this before,
Arnd suggested to keep it as is.
I do not know whether he is still planning that rework, though.
> > ...or something similiar (and maybe with some notes in its Kconfig help-text?).
What did you mean by "Kconfig help-text" ?
> I have tested both patches against recent kbuild-next and can boot on
> bare metal with clang.
> I have *not* passed any W= to my make, but I see that clang's W=1
> kbuild-cflags are active.
> [ scripts/Makefile.extrawarn ]
> ifeq ("$(origin W)", "command line")
> export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)
> # W=1 - warnings that may be relevant and does not occur too often
> ifneq ($(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
> [ ... ]
> KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
> # W=1 also stops suppressing some warnings
> ifdef CONFIG_CC_IS_CLANG
> KBUILD_CFLAGS += -Wno-initializer-overrides
> KBUILD_CFLAGS += -Wno-format
> KBUILD_CFLAGS += -Wno-sign-compare
> KBUILD_CFLAGS += -Wno-format-zero-length
> endif # CONFIG_CC_IS_CLANG
> endif # KBUILD_ENABLE_EXTRA_GCC_CHECKS
> These clang KBUILD_CFLAGS are active independently of passing W=1.
> $ grep '\-Wno-initializer-overrides'
> build-log_5.3.0-rc6-2-amd64-cbl-asmgoto.txt | wc -l
> So the above comment is misleading?
> Is W=1 activated by default?
> Or do I miss something?
I won't comment back to your long analysis.
Instead, I will post v2.
I hope you will notice something.
> [ Documentation/kbuild/kbuild.rst ]
> If enabled over the make command line with "W=1", it turns on additional
> gcc -W... options for more extensive build-time checking.
> What about?
> KBUILD_CC_EXTRA_CHECKS (or KBUILD_EXTRA_CC_CHECKS)
> If enabled over the make command line with "W=...", it turns on additional
> compiler warning options like -Wmissing-declarations for more extensive
> build-time checking. For more details see <Documentation/kbuild/kbuild.rst>.
> W=1 - warnings that may be relevant and does not occur too often
> W=1 - also stops suppressing some warnings
> W=2 - warnings that occur quite often but may still be relevant
> W=3 - the more obscure warnings, can most likely be ignored
> - Sedat -