[PATCH 1/2] kbuild: refactor scripts/Makefile.extrawarn

[Masahiro Yamada]

Instead of the warning-[123] 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.

[1] 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.

[2] 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.

[3] Currently, 4 Clang warnings (Winitializer-overrides, Wformat,
Wsign-compare, Wformat-zero-length) are shown by any of W=1, W=2,
and W=3. With this commit, they will be warned only by W=1. I
think this is a more correct behavior since each warning belongs
to only one warning level.

Signed-off-by: Masahiro Yamada <yamada....@socionext.com>
---

scripts/Makefile.extrawarn | 104 +++++++++++++++++++------------------
1 file changed, 53 insertions(+), 51 deletions(-)

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index a74ce2e3c33e..1fa53968e292 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -1,14 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
# ==========================================================================
-#
# make W=... settings
-#
-# W=1 - warnings that may be relevant and does not occur too often
-# W=2 - warnings that occur quite often but may still be relevant
-# W=3 - the more obscure warnings, can most likely be ignored
-#
-# $(call cc-option, -W...) handles gcc -W.. options which
-# are not supported by all versions of the compiler
# ==========================================================================

KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
@@ -17,58 +9,68 @@ ifeq ("$(origin W)", "command line")
export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)
endif

-ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS
-warning- := $(empty)
+#
+# W=1 - warnings that may be relevant and does not occur too often
+#
+ifneq ($(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)

-warning-1 := -Wextra -Wunused -Wno-unused-parameter
-warning-1 += -Wmissing-declarations
-warning-1 += -Wmissing-format-attribute
-warning-1 += -Wmissing-prototypes
-warning-1 += -Wold-style-definition
-warning-1 += -Wmissing-include-dirs
-warning-1 += $(call cc-option, -Wunused-but-set-variable)
-warning-1 += $(call cc-option, -Wunused-const-variable)
-warning-1 += $(call cc-option, -Wpacked-not-aligned)
-warning-1 += $(call cc-option, -Wstringop-truncation)
+KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
+KBUILD_CFLAGS += -Wmissing-declarations
+KBUILD_CFLAGS += -Wmissing-format-attribute
+KBUILD_CFLAGS += -Wmissing-prototypes
+KBUILD_CFLAGS += -Wold-style-definition
+KBUILD_CFLAGS += -Wmissing-include-dirs
+KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
+KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
+KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
+KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
# The following turn off the warnings enabled by -Wextra
-warning-1 += -Wno-missing-field-initializers
-warning-1 += -Wno-sign-compare
-
-warning-2 += -Wcast-align
-warning-2 += -Wdisabled-optimization
-warning-2 += -Wnested-externs
-warning-2 += -Wshadow
-warning-2 += $(call cc-option, -Wlogical-op)
-warning-2 += -Wmissing-field-initializers
-warning-2 += -Wsign-compare
-warning-2 += $(call cc-option, -Wmaybe-uninitialized)
-warning-2 += $(call cc-option, -Wunused-macros)
-
-warning-3 := -Wbad-function-cast
-warning-3 += -Wcast-qual
-warning-3 += -Wconversion
-warning-3 += -Wpacked
-warning-3 += -Wpadded
-warning-3 += -Wpointer-arith
-warning-3 += -Wredundant-decls
-warning-3 += -Wswitch-default
-warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
-
-warning := $(warning-$(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-warning += $(warning-$(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-warning += $(warning-$(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-
-ifeq ("$(strip $(warning))","")
- $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
-endif
+KBUILD_CFLAGS += -Wno-missing-field-initializers
+KBUILD_CFLAGS += -Wno-sign-compare

-KBUILD_CFLAGS += $(warning)
else

+# 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
+
+endif
+
+#
+# W=2 - warnings that occur quite often but may still be relevant
+#
+ifneq ($(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+
+KBUILD_CFLAGS += -Wcast-align
+KBUILD_CFLAGS += -Wdisabled-optimization
+KBUILD_CFLAGS += -Wnested-externs
+KBUILD_CFLAGS += -Wshadow
+KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
+KBUILD_CFLAGS += -Wmissing-field-initializers
+KBUILD_CFLAGS += -Wsign-compare
+KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
+KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
+
+endif
+
+#
+# W=3 - the more obscure warnings, can most likely be ignored
+#
+ifneq ($(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+
+KBUILD_CFLAGS += -Wbad-function-cast
+KBUILD_CFLAGS += -Wcast-qual
+KBUILD_CFLAGS += -Wconversion
+KBUILD_CFLAGS += -Wpacked
+KBUILD_CFLAGS += -Wpadded
+KBUILD_CFLAGS += -Wpointer-arith
+KBUILD_CFLAGS += -Wredundant-decls
+KBUILD_CFLAGS += -Wswitch-default
+KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)
+
endif
--
2.17.1

[Masahiro Yamada]

GCC and Clang have different policy for -Wunused-function; GCC does not
warn unused static inline functions at all whereas Clang does if they
are defined in source files instead of included headers although it has
been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress
warning for unused static inline functions").

We often miss to delete unused functions where 'static inline' is used
in *.c files since there is no tool to detect them. Unused code remains
until somebody notices. For example, commit 075ddd75680f ("regulator:
core: remove unused rdev_get_supply()").

Let's remove __maybe_unused from the inline macro to allow Clang to
start finding unused static inline functions. For now, we do this only
for W=1 build since it is not a good idea to sprinkle warnings for the
normal build.

My initial attempt was to add -Wno-unused-function for no W=1 build
(https://lore.kernel.org/patchwork/patch/1120594/)

Nathan Chancellor pointed out that would weaken Clang's checks since
we would no longer get -Wunused-function without W=1. It is true GCC
would detect unused static non-inline functions, but it would weaken
Clang as a standalone compiler at least.

Here is a counter implementation. The current problem is, W=... only
controls compiler flags, which are globally effective. There is no way
to narrow the scope to only 'static inline' functions.

This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123].
When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from
the 'inline' macro.

This makes the code a bit uglier, so personally I do not want to carry
this forever. If we can manage to fix most of the warnings, we can
drop this entirely, then enable -Wunused-function all the time.

If you contribute to code clean-up, please run "make CC=clang W=1"
and check -Wunused-function warnings. You will find lots of unused
functions.

Some of them are false-positives because the call-sites are disabled
by #ifdef. I do not like to abuse the inline keyword for suppressing
unused-function warnings because it is intended to be a hint for the
compiler optimization. I prefer #ifdef around the definition, or
__maybe_unused if #ifdef would make the code too ugly.

Signed-off-by: Masahiro Yamada <yamada....@socionext.com>
---

include/linux/compiler_types.h | 20 ++++++++++++++------
scripts/Makefile.extrawarn | 6 ++++++
2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 599c27b56c29..b056a40116da 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -130,10 +130,6 @@ struct ftrace_likely_data {

/*
* Force always-inline if the user requests it so via the .config.
- * GCC does not warn about unused static inline functions for
- * -Wunused-function. This turns out to avoid the need for complex #ifdef
- * directives. Suppress the warning in clang as well by using "unused"
- * function attribute, which is redundant but not harmful for gcc.
* Prefer gnu_inline, so that extern inline functions do not emit an
* externally visible function. This makes extern inline behave as per gnu89
* semantics rather than c99. This prevents multiple symbol definition errors
@@ -144,15 +140,27 @@ struct ftrace_likely_data {
*/
#if !defined(CONFIG_OPTIMIZE_INLINING)
#define inline inline __attribute__((__always_inline__)) __gnu_inline \
- __maybe_unused notrace
+ __inline_maybe_unused notrace
#else
#define inline inline __gnu_inline \
- __maybe_unused notrace
+ __inline_maybe_unused notrace
#endif

#define __inline__ inline
#define __inline inline

+/*
+ * GCC does not warn about unused static inline functions for -Wunused-function.
+ * Suppress the warning in clang as well by using __maybe_unused, but enable it
+ * for W=1 build. This will allow clang to find unused functions. Remove the
+ * __inline_maybe_unused entirely after fixing most of -Wunused-function warnings.
+ */
+#ifdef KBUILD_EXTRA_WARN1
+#define __inline_maybe_unused
+#else
+#define __inline_maybe_unused __maybe_unused
+#endif
+
/*
* Rather then using noinline to prevent stack consumption, use
* noinline_for_stack instead. For documentation reasons.
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 1fa53968e292..3af1770497fd 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -28,6 +28,8 @@ KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
KBUILD_CFLAGS += -Wno-missing-field-initializers
KBUILD_CFLAGS += -Wno-sign-compare

+KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
+
else

# W=1 also stops suppressing some warnings

@@ -56,6 +58,8 @@ KBUILD_CFLAGS += -Wsign-compare
KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)

+KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
+
endif

#
@@ -73,4 +77,6 @@ KBUILD_CFLAGS += -Wredundant-decls
KBUILD_CFLAGS += -Wswitch-default
KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)

+KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
+
endif
--
2.17.1

[Sedat Dilek]

On Wed, Aug 28, 2019 at 7:55 AM Masahiro Yamada
<yamada....@socionext.com> wrote:
>
> Instead of the warning-[123] 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.
>
> [1] 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.
>
> [2] 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...

KBUILD_ENABLE_EXTRA_CC_CHECKS

...or something similiar (and maybe with some notes in its Kconfig help-text?).

Regards,
- Sedat -

> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-li...@googlegroups.com.
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[Sedat Dilek]

On Wed, Aug 28, 2019 at 9:20 AM Sedat Dilek <sedat...@gmail.com> wrote:
>
> On Wed, Aug 28, 2019 at 7:55 AM Masahiro Yamada
> <yamada....@socionext.com> wrote:
> >
> > Instead of the warning-[123] 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.
> >
> > [1] 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.
> >
> > [2] 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...
>
> KBUILD_ENABLE_EXTRA_CC_CHECKS
>
> ...or something similiar (and maybe with some notes in its 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)
endif

#

# 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

else

# 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
27195

So the above comment is misleading?

Is W=1 activated by default?

Or do I miss something?

[ Documentation/kbuild/kbuild.rst ]

KBUILD_ENABLE_EXTRA_GCC_CHECKS
------------------------------
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 -

[Sedat Dilek]

> build-time checking. For more details see <Documentation/kbuild/kbuild.rst>.

Grrr.

s/ Documentation/kbuild/kbuild.rst / scripts/Makefile.extrawarn

- Sedat -

[Sedat Dilek]

Something like that...

[PATCH 1/2] kbuild: Improve extrawarn documentation
[PATCH 2/2] kbuild: Rename extrawarn Kconfig to KBUILD_EXTRA_CC_CHECKS

- Sedat -

[Nathan Chancellor]

On Wed, Aug 28, 2019 at 02:54:24PM +0900, Masahiro Yamada wrote:
> Instead of the warning-[123] 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.
>
> [1] 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.
>
> [2] 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.
>
> [3] Currently, 4 Clang warnings (Winitializer-overrides, Wformat,
> Wsign-compare, Wformat-zero-length) are shown by any of W=1, W=2,
> and W=3. With this commit, they will be warned only by W=1. I
> think this is a more correct behavior since each warning belongs
> to only one warning level.
>
> Signed-off-by: Masahiro Yamada <yamada....@socionext.com>

Reviewed-by: Nathan Chancellor <natecha...@gmail.com>

[Nathan Chancellor]

I can still see warnings from static unused functions and with W=1, I
see plenty more. I agree that this is uglier because of the
__inline_maybe_unused but I think this is better for regular developers.
I will try to work on these unused-function warnings!

Reviewed-by: Nathan Chancellor <natecha...@gmail.com>
Tested-by: Nathan Chancellor <natecha...@gmail.com>

[Nick Desaulniers]

On Wed, Aug 28, 2019 at 12:20 AM Sedat Dilek <sedat...@gmail.com> wrote:
>
> On Wed, Aug 28, 2019 at 7:55 AM Masahiro Yamada
> <yamada....@socionext.com> wrote:
> >
> > Instead of the warning-[123] 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.
> >
> > [1] 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.
> >
> > [2] 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...
>
> KBUILD_ENABLE_EXTRA_CC_CHECKS
>
> ...or something similiar (and maybe with some notes in its Kconfig help-text?).

I too would like to see that changed.

--
Thanks,
~Nick Desaulniers

[Nick Desaulniers]

I find this part of the patch exceedingly confusing, and I think it
mistakenly changes the behavior of W=2, W=3, and W=4. If W != 1 && CC
== clang, then disable some flags? What? So W=2,3,4 those are
disabled, but at W=1 are not? Didn't the previous version set these
unless any W= was set?

--
Thanks,
~Nick Desaulniers

[Nick Desaulniers]

On Wed, Aug 28, 2019 at 11:20 AM Nathan Chancellor
<natecha...@gmail.com> wrote:
>
> On Wed, Aug 28, 2019 at 02:54:25PM +0900, Masahiro Yamada wrote:
> > GCC and Clang have different policy for -Wunused-function; GCC does not
> > warn unused static inline functions at all whereas Clang does if they
> > are defined in source files instead of included headers although it has
> > been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress
> > warning for unused static inline functions").
> >
> > We often miss to delete unused functions where 'static inline' is used
> > in *.c files since there is no tool to detect them. Unused code remains
> > until somebody notices. For example, commit 075ddd75680f ("regulator:
> > core: remove unused rdev_get_supply()").
> >
> > Let's remove __maybe_unused from the inline macro to allow Clang to
> > start finding unused static inline functions. For now, we do this only
> > for W=1 build since it is not a good idea to sprinkle warnings for the
> > normal build.
> >
> > My initial attempt was to add -Wno-unused-function for no W=1 build
> > (https://lore.kernel.org/patchwork/patch/1120594/)
> >
> > Nathan Chancellor pointed out that would weaken Clang's checks since
> > we would no longer get -Wunused-function without W=1. It is true GCC
> > would detect unused static non-inline functions, but it would weaken
> > Clang as a standalone compiler at least.

Got it. No problem.

> >
> > Here is a counter implementation. The current problem is, W=... only
> > controls compiler flags, which are globally effective. There is no way
> > to narrow the scope to only 'static inline' functions.
> >
> > This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123].
> > When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from
> > the 'inline' macro.
> >
> > This makes the code a bit uglier, so personally I do not want to carry
> > this forever. If we can manage to fix most of the warnings, we can
> > drop this entirely, then enable -Wunused-function all the time.

How many warnings?

> >
> > If you contribute to code clean-up, please run "make CC=clang W=1"
> > and check -Wunused-function warnings. You will find lots of unused
> > functions.
> >
> > Some of them are false-positives because the call-sites are disabled
> > by #ifdef. I do not like to abuse the inline keyword for suppressing
> > unused-function warnings because it is intended to be a hint for the
> > compiler optimization. I prefer #ifdef around the definition, or
> > __maybe_unused if #ifdef would make the code too ugly.
> >
> > Signed-off-by: Masahiro Yamada <yamada....@socionext.com>
>
> I can still see warnings from static unused functions and with W=1, I
> see plenty more. I agree that this is uglier because of the
> __inline_maybe_unused but I think this is better for regular developers.
> I will try to work on these unused-function warnings!

How many are we talking here?

>
> Reviewed-by: Nathan Chancellor <natecha...@gmail.com>
> Tested-by: Nathan Chancellor <natecha...@gmail.com>

This is getting kind of messy. I was more ok when the goal seemed to
be simplifying the definition of `inline`, but this is worse IMO.

--
Thanks,
~Nick Desaulniers

[Nathan Chancellor]

In an x86 defconfig build (one of the smallest builds we do), I see an
additional 35 warnings that crop up:

https://gist.github.com/003ba86ba60b4ac7e8109089d6cb1a5a

> > >
> > > If you contribute to code clean-up, please run "make CC=clang W=1"
> > > and check -Wunused-function warnings. You will find lots of unused
> > > functions.
> > >
> > > Some of them are false-positives because the call-sites are disabled
> > > by #ifdef. I do not like to abuse the inline keyword for suppressing
> > > unused-function warnings because it is intended to be a hint for the
> > > compiler optimization. I prefer #ifdef around the definition, or
> > > __maybe_unused if #ifdef would make the code too ugly.
> > >
> > > Signed-off-by: Masahiro Yamada <yamada....@socionext.com>
> >
> > I can still see warnings from static unused functions and with W=1, I
> > see plenty more. I agree that this is uglier because of the
> > __inline_maybe_unused but I think this is better for regular developers.
> > I will try to work on these unused-function warnings!
>
> How many are we talking here?
>
> >
> > Reviewed-by: Nathan Chancellor <natecha...@gmail.com>
> > Tested-by: Nathan Chancellor <natecha...@gmail.com>
>
> This is getting kind of messy. I was more ok when the goal seemed to
> be simplifying the definition of `inline`, but this is worse IMO.

I guess if you want, we can just go back to v1 and have all unused
function warnings hidden by default with clang. Fixing these warnings
will take a significant amount of time given there will probably be a
few hundred so I don't think having this warning hidden behind W=1 for
that long is a good thing.

Cheers,
Nathan

[Sedat Dilek]

Just a quick test...

...with clang-9 (built with tc-build from llvm-project.git#release/9.x)

$ mycompiler --version
ClangBuiltLinux clang version 9.0.0
(git://github.com/llvm/llvm-project
e82a53603ae3fed2215a44b5ac603db00a780c02) (based on LLVM 9.0.0)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/sdi/src/llvm-toolchain/install/bin

$ mylinker --version
LLD 9.0.0 (git://github.com/llvm/llvm-project
e82a53603ae3fed2215a44b5ac603db00a780c02) (compatible with GNU
linkers)

With each run (changing W=...), I stopped my build-script manually,
that's why the numbers differ.

[ NO W-N ]

sdi@iniza:~/src/linux-kernel$ for i in Wno-initializer-overrides
Wno-format Wno-sign-compare Wno-format-zero-length ; do echo [ $i ] ;
grep $i build-log_5.3.0-rc6-2-amd64-cbl-asmgoto.txt_NO-W-N | wc -l ;
done
[ Wno-initializer-overrides ]
178
[ Wno-format ]
178
[ Wno-sign-compare ]
178
[ Wno-format-zero-length ]
178

[ W=1 ]

sdi@iniza:~/src/linux-kernel$ for i in Wno-initializer-overrides
Wno-format Wno-sign-compare Wno-format-zero-length ; do echo [ $i ] ;
grep $i build-log_5.3.0-rc6-2-amd64-cbl-asmgoto.txt_W-1 | wc -l ; done
[ Wno-initializer-overrides ]
0
[ Wno-format ]
169
[ Wno-sign-compare ]
169
[ Wno-format-zero-length ]
0

[ W=2 ]

sdi@iniza:~/src/linux-kernel$ for i in Wno-initializer-overrides
Wno-format Wno-sign-compare Wno-format-zero-length ; do echo [ $i ] ;
grep $i build-log_5.3.0-rc6-2-amd64-cbl-asmgoto.txt_W-2 | wc -l ; done
[ Wno-initializer-overrides ]
129
[ Wno-format ]
129
[ Wno-sign-compare ]
129
[ Wno-format-zero-length ]
129

[ W=3 ]

sdi@iniza:~/src/linux-kernel$ for i in Wno-initializer-overrides
Wno-format Wno-sign-compare Wno-format-zero-length ; do echo [ $i ] ;
grep $i build-log_5.3.0-rc6-2-amd64-cbl-asmgoto.txt_W-3 | wc -l ; done
[ Wno-initializer-overrides ]
114
[ Wno-format ]
114
[ Wno-sign-compare ]
114
[ Wno-format-zero-length ]
114

[ W=4 ]

sdi@iniza:~/src/linux-kernel$ for i in Wno-initializer-overrides
Wno-format Wno-sign-compare Wno-format-zero-length ; do echo [ $i ] ;
grep $i build-log_5.3.0-rc6-2-amd64-cbl-asmgoto.txt_W-4 | wc -l ; done
[ Wno-initializer-overrides ]
495
[ Wno-format ]
495
[ Wno-sign-compare ]
495
[ Wno-format-zero-length ]
495

W=1 is not passing -Wno-initializer-overrides and -Wno-format-zero-length.
Unsure if other KBUILD_CFLAGS in W=1 disables them.

So, if it is desired to pass the CLANG extrawarn compiler-options to
all W=... then I ask myself why the CLANG block is in the W=1 block
only?
So if CLANG extrawarn options are independent of any W=... make-option
then I prefer to put it in a seperate block with an appropriate
comment.

According to the commit message W=4 is unsupported, but I can do a
'make V=1 W=4'.
If I pass an unsupported value to W=... then I expect an warning or
info or exit or whatever.

My €0,02.

- Sedat -

[Sedat Dilek]

> So, if it is desired to pass the CLANG extrawarn compiler-options to
> all W=... then I ask myself why the CLANG block is in the W=1 block
> only?
> So if CLANG extrawarn options are independent of any W=... make-option
> then I prefer to put it in a seperate block with an appropriate
> comment.
>

Maybe something like that (on top of the two patches I had sent).

From: Sedat Dilek <sedat...@credativ.de>
Date: Thu, 29 Aug 2019 11:35:21 +0200
Subject: [PATCH 3/3] kbuild: Move extra warnings for Clang

---
Documentation/kbuild/kbuild.rst | 5 +++--
scripts/Makefile.extrawarn | 21 ++++++++++-----------
2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
index 3e65d32af875..fa9772ae2367 100644
--- a/Documentation/kbuild/kbuild.rst
+++ b/Documentation/kbuild/kbuild.rst
@@ -245,10 +245,11 @@ 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 <scripts/Makefile.extrawarn>.
+build-time checking.
+Some extra warning options are set for all W=... settings when using Clang.
+For more details see <scripts/Makefile.extrawarn>.

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

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 72677ee9f202..86c0f8ae7e35 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -5,6 +5,16 @@

KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)

+#
+# W=... - stops suppressing some warnings when using Clang
+#
+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
+

ifeq ("$(origin W)", "command line")

export KBUILD_EXTRA_CC_CHECKS := $(W)
endif
@@ -30,17 +40,6 @@ KBUILD_CFLAGS += -Wno-sign-compare

KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1

-else
-
-# 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
-
endif

#
--
2.20.1

- Sedat -

[Masahiro Yamada]

On Wed, Aug 28, 2019 at 11:19 PM Sedat Dilek <sedat...@gmail.com> wrote:
>
> On Wed, Aug 28, 2019 at 9:20 AM Sedat Dilek <sedat...@gmail.com> wrote:
> >
> > On Wed, Aug 28, 2019 at 7:55 AM Masahiro Yamada
> > <yamada....@socionext.com> wrote:
> > >
> > > Instead of the warning-[123] 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.
> > >
> > > [1] 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.
> > >
> > > [2] 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.
(see scripts/Makefile.lib)

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.
https://patchwork.kernel.org/patch/10172331/#21385013

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 won't comment back to your long analysis.

Instead, I will post v2.
I hope you will notice something.

> [ Documentation/kbuild/kbuild.rst ]
>
> KBUILD_ENABLE_EXTRA_GCC_CHECKS
> ------------------------------
> 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 -

--
Best Regards

Masahiro Yamada

[Masahiro Yamada]

Instead of the warning-[123] 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.

[1] 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.

[2] 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.

[3] Currently, 4 Clang warnings (Winitializer-overrides, Wformat,
Wsign-compare, Wformat-zero-length) are shown by any of W=1, W=2,
and W=3. With this commit, they will be warned only by W=1. I
think this is a more correct behavior since each warning belongs

to only one group.

For understanding this commit correctly:

We have 3 warning groups, W=1, W=2, and W=3. You may think W=3 has a
higher level than W=1, but they are actually independent. If you like,
you can combine them like W=13. To enable all the warnings, you can
pass W=123. This is shown by 'make help', but it is often missed
unfortunately. Since we support W= combination, there should not exist
intersection among the three groups. If we enable Winitializer-overrides
for W=1, we do not need to for W=2 or W=3. This is why I believe the
change [3] makes sense.

The documentation says -Winitializer-overrides is enabled by default.
(https://clang.llvm.org/docs/DiagnosticsReference.html#winitializer-overrides)
We negate it by passing -Wno-initializer-overrides for the normal
build, but we do not do that for W=1. This means, W=1 effectively
enables -Winitializer-overrides by the clang's default. The same for
the other three. I wonder if this logic needs detailed commenting,
but I do not want to be bothered any more. I added comments.

Signed-off-by: Masahiro Yamada <yamada....@socionext.com>
Reviewed-by: Nathan Chancellor <natecha...@gmail.com>

---

Changes in v2:
- Added comments and more commit log

scripts/Makefile.extrawarn | 105 +++++++++++++++++++------------------
1 file changed, 54 insertions(+), 51 deletions(-)

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index a74ce2e3c33e..3680445823b7 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn

@@ -1,14 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
# ==========================================================================
-#
# make W=... settings
-#
-# W=1 - warnings that may be relevant and does not occur too often
-# W=2 - warnings that occur quite often but may still be relevant
-# W=3 - the more obscure warnings, can most likely be ignored
-#
-# $(call cc-option, -W...) handles gcc -W.. options which
-# are not supported by all versions of the compiler
# ==========================================================================

KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)

@@ -17,58 +9,69 @@ ifeq ("$(origin W)", "command line")

export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)
endif

+# Some diagnostics such as -Winitializer-overrides are enabled by default.
+# We suppress them by using -Wno... except for W=1.
+

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

[Sedat Dilek]

Thanks for the v2.

I am impressed by the very informative commit-log.

But... I still miss relevant infos in the "kbuild-docs" aka in
<Documentation/kbuild/kbuild.rst file>

I also was not aware I can combine W=... settings like W=123 (W=132
and W=321 does the same I guess).
In my little world W=3 should include W=1 and W=2.
Such informations I would like to have in kbuild-docs.

BTW, I mixed up kbuild-system with kconfig-system as I normally get in
touch with the 2nd.

Renaming the kbuild-variable is up to you.
I am OK when you want to wait for Arnd's rework of extrawarn compiler options.
I did change it in one of my patches treewide.

- Sedat -

[Sedat Dilek]

On Thu, Aug 29, 2019 at 8:13 PM Masahiro Yamada
<yamada....@socionext.com> wrote:
>

Tested-by: Sedat Dilek <sedat...@gmail.com> (on top of kbuild-next
as of 2019-08-30).

- Sedat -

[Sedat Dilek]

On Thu, Aug 29, 2019 at 1:28 AM 'Nick Desaulniers' via Clang Built
Linux <clang-bu...@googlegroups.com> wrote:
[...]

> > >
> > > Here is a counter implementation. The current problem is, W=... only
> > > controls compiler flags, which are globally effective. There is no way
> > > to narrow the scope to only 'static inline' functions.
> > >
> > > This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123].
> > > When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from
> > > the 'inline' macro.
> > >
> > > This makes the code a bit uglier, so personally I do not want to carry
> > > this forever. If we can manage to fix most of the warnings, we can
> > > drop this entirely, then enable -Wunused-function all the time.
>
> How many warnings?
>

I tried or adapted this 2-2 patch with v2 of 1-2 patch which is in
kbuild.git#kbuild (see below [1]).

$ grep warning: build-log.txt | grep '\[-Wunused-function]' | wc -l
214

$ grep warning: build-log.txt | grep '\[-Wunused-function]' | sort
arch/x86/kernel/apic/io_apic.c:162:19: warning: unused function
'mp_init_irq_at_boot' [-Wunused-function]
arch/x86/kernel/cpu/common.c:298:19: warning: unused function
'flag_is_changeable_p' [-Wunused-function]
arch/x86/kvm/lapic.c:302:19: warning: unused function
'apic_lvt_vector' [-Wunused-function]
arch/x86/xen/p2m.c:137:24: warning: unused function 'p2m_index'
[-Wunused-function]
block/blk-zoned.c:23:24: warning: unused function 'blk_zone_start'
[-Wunused-function]
block/partitions/mac.c:23:20: warning: unused function
'mac_fix_string' [-Wunused-function]
drivers/acpi/ec.c:2047:20: warning: unused function
'acpi_ec_query_exit' [-Wunused-function]
drivers/atm/horizon.c:465:20: warning: unused function 'dump_regs'
[-Wunused-function]
drivers/atm/horizon.c:479:20: warning: unused function 'dump_framer'
[-Wunused-function]
drivers/atm/idt77252.c:1786:1: warning: unused function
'idt77252_fbq_level' [-Wunused-function]
drivers/cpufreq/intel_pstate.c:77:23: warning: unused function
'percent_fp' [-Wunused-function]
drivers/cpufreq/intel_pstate.c:92:23: warning: unused function
'percent_ext_fp' [-Wunused-function]
drivers/crypto/chelsio/chcr_algo.c:129:19: warning: unused function
'is_ofld_imm' [-Wunused-function]
drivers/crypto/qat/qat_common/qat_asym_algs.c:252:34: warning: unused
function 'qat_dh_get_params' [-Wunused-function]
drivers/dma/ioat/dca.c:44:19: warning: unused function
'dca2_tag_map_valid' [-Wunused-function]
drivers/edac/i5100_edac.c:247:19: warning: unused function
'i5100_nrecmema_dm_buf_id' [-Wunused-function]
drivers/gpu/drm/drm_mm.c:155:1: warning: unused function
'drm_mm_interval_tree_insert' [-Wunused-function]
drivers/gpu/drm/drm_mm.c:155:1: warning: unused function
'drm_mm_interval_tree_iter_next' [-Wunused-function]
drivers/gpu/drm/drm_mm.c:294:19: warning: unused function
'rb_hole_size' [-Wunused-function]
drivers/gpu/drm/gma500/psb_drv.c:400:20: warning: unused function
'get_brightness' [-Wunused-function]
drivers/gpu/drm/gma500/psb_irq.c:49:1: warning: unused function
'mid_pipe_vsync' [-Wunused-function]
drivers/gpu/drm/i915/display/intel_hdmi.c:1696:26: warning: unused
function 'intel_hdmi_hdcp2_protocol' [-Wunused-function]
drivers/gpu/drm/i915/i915_sw_fence.c:105:20: warning: unused function
'debug_fence_free' [-Wunused-function]
drivers/gpu/drm/i915/i915_sw_fence.c:84:20: warning: unused function
'debug_fence_init_onstack' [-Wunused-function]
drivers/gpu/drm/i915/intel_guc_submission.c:1117:20: warning: unused
function 'ctx_save_restore_disabled' [-Wunused-function]
drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:58:35: warning: unused
function 'vmw_overlay' [-Wunused-function]
drivers/hv/ring_buffer.c:89:1: warning: unused function
'hv_set_next_read_location' [-Wunused-function]
drivers/hwmon/nct6683.c:485:19: warning: unused function 'in_to_reg'
[-Wunused-function]
drivers/hwmon/sis5595.c:158:18: warning: unused function 'DIV_TO_REG'
[-Wunused-function]
drivers/hwmon/vt1211.c:198:20: warning: unused function 'superio_outb'
[-Wunused-function]
drivers/infiniband/core/cm.c:1528:19: warning: unused function
'cm_is_active_peer' [-Wunused-function]
drivers/infiniband/core/device.c:2747:1: warning: unused function
'__chk_RDMA_NL_LS' [-Wunused-function]
drivers/infiniband/core/iwcm.c:1208:1: warning: unused function
'__chk_RDMA_NL_IWCM' [-Wunused-function]
drivers/infiniband/core/nldev.c:2105:1: warning: unused function
'__chk_RDMA_NL_NLDEV' [-Wunused-function]
drivers/infiniband/hw/qib/qib_iba7322.c:803:19: warning: unused
function 'qib_read_ureg' [-Wunused-function]
drivers/infiniband/sw/rdmavt/vt.c:287:36: warning: unused function
'to_iucontext' [-Wunused-function]
drivers/isdn/hardware/mISDN/hfcmulti.c:667:1: warning: unused function
'vpm_read_address' [-Wunused-function]
drivers/leds/leds-pca955x.c:140:19: warning: unused function
'pca95xx_num_led_regs' [-Wunused-function]
drivers/md/raid0.c:444:19: warning: unused function
'is_io_in_chunk_boundary' [-Wunused-function]
drivers/media/dvb-frontends/drxk_hard.c:159:19: warning: unused
function 'MulDiv32' [-Wunused-function]
drivers/media/dvb-frontends/stb6100.c:113:20: warning: unused function
'stb6100_normalise_regs' [-Wunused-function]
drivers/media/i2c/cs3308.c:30:19: warning: unused function
'cs3308_read' [-Wunused-function]
drivers/media/i2c/cx25840/cx25840-ir.c:139:19: warning: unused
function 'ns_to_clock_divider' [-Wunused-function]
drivers/media/i2c/cx25840/cx25840-ir.c:145:28: warning: unused
function 'clock_divider_to_ns' [-Wunused-function]
drivers/media/i2c/cx25840/cx25840-ir.c:163:19: warning: unused
function 'freq_to_clock_divider' [-Wunused-function]
drivers/media/mc/mc-entity.c:17:27: warning: unused function
'gobj_type' [-Wunused-function]
drivers/media/pci/cx18/cx18-alsa-main.c:56:23: warning: unused
function 'p_to_snd_cx18_card' [-Wunused-function]
drivers/media/pci/cx23885/cx23888-ir.c:178:19: warning: unused
function 'ns_to_clock_divider' [-Wunused-function]
drivers/media/pci/cx23885/cx23888-ir.c:184:28: warning: unused
function 'clock_divider_to_ns' [-Wunused-function]
drivers/media/pci/cx23885/cx23888-ir.c:202:19: warning: unused
function 'freq_to_clock_divider' [-Wunused-function]
drivers/media/pci/ivtv/ivtv-alsa-main.c:53:23: warning: unused
function 'p_to_snd_ivtv_card' [-Wunused-function]
drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:394:19: warning: unused
function 'vop_interlaced' [-Wunused-function]
drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:399:18: warning: unused
function 'vop_channel' [-Wunused-function]
drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:414:18: warning: unused
function 'vop_hsize' [-Wunused-function]
drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:419:18: warning: unused
function 'vop_vsize' [-Wunused-function]
drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:439:19: warning: unused
function 'vop_sec' [-Wunused-function]
drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:444:19: warning: unused
function 'vop_usec' [-Wunused-function]
drivers/media/rc/fintek-cir.c:55:20: warning: unused function
'fintek_clear_reg_bit' [-Wunused-function]
drivers/media/rc/nuvoton-cir.c:78:20: warning: unused function
'nvt_clear_reg_bit' [-Wunused-function]
drivers/media/usb/au0828/au0828-i2c.c:26:19: warning: unused function
'i2c_slave_did_write_ack' [-Wunused-function]
drivers/media/usb/usbvision/usbvision-video.c:145:37: warning: unused
function 'cd_to_usbvision' [-Wunused-function]
drivers/misc/hpilo.c:396:19: warning: unused function
'is_device_reset' [-Wunused-function]
drivers/mmc/host/sdricoh_cs.c:104:28: warning: unused function
'sdricoh_readw' [-Wunused-function]
drivers/net/ethernet/atheros/atl1c/atl1c_main.c:184:20: warning:
unused function 'atl1c_irq_reset' [-Wunused-function]
drivers/net/ethernet/broadcom/b44.c:201:20: warning: unused function
'__b44_cam_read' [-Wunused-function]
drivers/net/ethernet/broadcom/bnx2x/bnx2x_sriov.c:334:20: warning:
unused function 'bnx2x_vf_vlan_credit' [-Wunused-function]
drivers/net/ethernet/cavium/liquidio/request_manager.c:43:19: warning:
unused function 'IQ_INSTR_MODE_64B' [-Wunused-function]
drivers/net/ethernet/chelsio/cxgb3/sge.c:167:32: warning: unused
function 'fl_to_qset' [-Wunused-function]
drivers/net/ethernet/chelsio/cxgb4/sge.c:857:28: warning: unused
function 'calc_tx_descs' [-Wunused-function]
drivers/net/ethernet/intel/ixgbe/ixgbe_main.c:2952:20: warning: unused
function 'ixgbe_irq_disable_queues' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:1546:20: warning: unused
function 'hw_ena_intr_bit' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2120:19: warning: unused
function 'port_chk_broad_storm' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2278:20: warning: unused
function 'port_cfg_force_flow_ctrl' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2284:19: warning: unused
function 'port_chk_back_pressure' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2290:19: warning: unused
function 'port_chk_force_flow_ctrl' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2298:20: warning: unused
function 'port_cfg_rx' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2304:20: warning: unused
function 'port_cfg_tx' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2315:20: warning: unused
function 'sw_flush_dyn_mac_table' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2326:20: warning: unused
function 'port_cfg_ins_tag' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2332:20: warning: unused
function 'port_cfg_rmv_tag' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2338:19: warning: unused
function 'port_chk_ins_tag' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2344:19: warning: unused
function 'port_chk_rmv_tag' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2350:20: warning: unused
function 'port_cfg_dis_non_vid' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2356:20: warning: unused
function 'port_cfg_in_filter' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2362:19: warning: unused
function 'port_chk_dis_non_vid' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2368:19: warning: unused
function 'port_chk_in_filter' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2411:20: warning: unused
function 'sw_cfg_unk_def_deliver' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2417:19: warning: unused
function 'sw_cfg_chk_unk_def_deliver' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2423:20: warning: unused
function 'sw_cfg_unk_def_port' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2428:19: warning: unused
function 'sw_chk_unk_def_port' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2459:19: warning: unused
function 'port_chk_diffserv' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2465:19: warning: unused
function 'port_chk_802_1p' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2471:19: warning: unused
function 'port_chk_replace_vid' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2477:19: warning: unused
function 'port_chk_prio' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2689:20: warning: unused
function 'sw_get_addr' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2906:20: warning: unused
function 'hw_r_phy_link_stat' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2911:20: warning: unused
function 'hw_r_phy_auto_neg' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2916:20: warning: unused
function 'hw_w_phy_auto_neg' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2921:20: warning: unused
function 'hw_r_phy_rem_cap' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2926:20: warning: unused
function 'hw_r_phy_crossover' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2931:20: warning: unused
function 'hw_w_phy_crossover' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2936:20: warning: unused
function 'hw_r_phy_polarity' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2941:20: warning: unused
function 'hw_w_phy_polarity' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2946:20: warning: unused
function 'hw_r_phy_link_md' [-Wunused-function]
drivers/net/ethernet/micrel/ksz884x.c:2951:20: warning: unused
function 'hw_w_phy_link_md' [-Wunused-function]
drivers/net/ethernet/myricom/myri10ge/myri10ge.c:1177:20: warning:
unused function 'myri10ge_vlan_ip_csum' [-Wunused-function]
drivers/net/ethernet/sun/cassini.c:240:20: warning: unused function
'cas_lock_all' [-Wunused-function]
drivers/net/ethernet/sun/cassini.c:269:20: warning: unused function
'cas_unlock_all' [-Wunused-function]
drivers/net/ethernet/tehuti/tehuti.c:1368:19: warning: unused function
'bdx_tx_db_size' [-Wunused-function]
drivers/net/usb/plusb.c:67:1: warning: unused function
'pl_clear_QuickLink_features' [-Wunused-function]
drivers/net/usb/sierra_net.c:357:19: warning: unused function
'sierra_net_is_valid_addrlen' [-Wunused-function]
drivers/net/wireless/ath/ath10k/ce.c:127:1: warning: unused function
'ath10k_get_ring_byte' [-Wunused-function]
drivers/net/wireless/ath/ath10k/ce.c:212:1: warning: unused function
'ath10k_ce_shadow_dest_ring_write_index_set' [-Wunused-function]
drivers/net/wireless/ath/ath10k/ce.c:449:20: warning: unused function
'ath10k_ce_error_intr_enable' [-Wunused-function]
drivers/net/wireless/broadcom/b43legacy/dma.c:130:19: warning: unused
function 'prev_slot' [-Wunused-function]
drivers/net/wireless/broadcom/b43legacy/dma.c:217:19: warning: unused
function 'txring_to_priority' [-Wunused-function]
drivers/net/wireless/broadcom/b43legacy/radio.c:1713:5: warning:
unused function 'freq_r3A_value' [-Wunused-function]
drivers/net/wireless/intel/ipw2x00/ipw2200.c:3010:19: warning: unused
function 'ipw_alive' [-Wunused-function]
drivers/net/wireless/intel/ipw2x00/ipw2200.c:381:19: warning: unused
function '_ipw_read16' [-Wunused-function]
drivers/net/wireless/intel/iwlegacy/3945.c:226:1: warning: unused
function 'il3945_get_tx_fail_reason' [-Wunused-function]
drivers/net/wireless/intel/iwlwifi/mvm/sta.c:1370:18: warning: unused
function 'iwl_mvm_tid_to_ac_queue' [-Wunused-function]
drivers/net/wireless/realtek/rtw88/pci.c:81:21: warning: unused
function 'rtw_pci_get_tx_desc' [-Wunused-function]
drivers/nvme/target/fc.c:151:1: warning: unused function
'nvmet_fc_iodnum' [-Wunused-function]
drivers/nvme/target/fc.c:157:1: warning: unused function
'nvmet_fc_fodnum' [-Wunused-function]
drivers/pci/hotplug/shpchp_hpc.c:177:20: warning: unused function
'shpc_writeb' [-Wunused-function]
drivers/pcmcia/yenta_socket.c:147:18: warning: unused function
'exca_readw' [-Wunused-function]
drivers/scsi/aacraid/aachba.c:1880:19: warning: unused function
'aac_get_safw_phys_device_type' [-Wunused-function]
drivers/scsi/cxgbi/libcxgbi.c:2287:19: warning: unused function
'csk_print_port' [-Wunused-function]
drivers/scsi/cxgbi/libcxgbi.c:2298:19: warning: unused function
'csk_print_ip' [-Wunused-function]
drivers/scsi/myrb.c:2557:20: warning: unused function
'DAC960_LA_gen_intr' [-Wunused-function]
drivers/scsi/myrb.c:2591:20: warning: unused function
'DAC960_LA_ack_mem_mbox_intr' [-Wunused-function]
drivers/scsi/myrb.c:2609:20: warning: unused function
'DAC960_LA_mem_mbox_status_available' [-Wunused-function]
drivers/scsi/myrb.c:2632:20: warning: unused function
'DAC960_LA_intr_enabled' [-Wunused-function]
drivers/scsi/myrb.c:2661:29: warning: unused function
'DAC960_LA_read_status_cmd_ident' [-Wunused-function]
drivers/scsi/myrb.c:2834:20: warning: unused function
'DAC960_PG_gen_intr' [-Wunused-function]
drivers/scsi/myrb.c:2868:20: warning: unused function
'DAC960_PG_ack_mem_mbox_intr' [-Wunused-function]
drivers/scsi/myrb.c:2886:20: warning: unused function
'DAC960_PG_mem_mbox_status_available' [-Wunused-function]
drivers/scsi/myrb.c:2908:20: warning: unused function
'DAC960_PG_intr_enabled' [-Wunused-function]
drivers/scsi/myrb.c:2938:1: warning: unused function
'DAC960_PG_read_status_cmd_ident' [-Wunused-function]
drivers/scsi/myrb.c:3112:20: warning: unused function
'DAC960_PD_gen_intr' [-Wunused-function]
drivers/scsi/myrb.c:3158:20: warning: unused function
'DAC960_PD_intr_enabled' [-Wunused-function]
drivers/scsi/myrs.c:2416:20: warning: unused function
'DAC960_GEM_gen_intr' [-Wunused-function]
drivers/scsi/myrs.c:2460:20: warning: unused function
'DAC960_GEM_ack_mem_mbox_intr' [-Wunused-function]
drivers/scsi/myrs.c:2483:20: warning: unused function
'DAC960_GEM_mem_mbox_status_available' [-Wunused-function]
drivers/scsi/myrs.c:2505:20: warning: unused function
'DAC960_GEM_intr_enabled' [-Wunused-function]
drivers/scsi/myrs.c:2533:30: warning: unused function
'DAC960_GEM_read_cmd_ident' [-Wunused-function]
drivers/scsi/myrs.c:2682:20: warning: unused function
'DAC960_BA_gen_intr' [-Wunused-function]
drivers/scsi/myrs.c:2718:20: warning: unused function
'DAC960_BA_ack_mem_mbox_intr' [-Wunused-function]
drivers/scsi/myrs.c:2737:20: warning: unused function
'DAC960_BA_mem_mbox_status_available' [-Wunused-function]
drivers/scsi/myrs.c:2755:20: warning: unused function
'DAC960_BA_intr_enabled' [-Wunused-function]
drivers/scsi/myrs.c:2782:30: warning: unused function
'DAC960_BA_read_cmd_ident' [-Wunused-function]
drivers/scsi/myrs.c:2932:20: warning: unused function
'DAC960_LP_gen_intr' [-Wunused-function]
drivers/scsi/myrs.c:2968:20: warning: unused function
'DAC960_LP_ack_mem_mbox_intr' [-Wunused-function]
drivers/scsi/myrs.c:2987:20: warning: unused function
'DAC960_LP_mem_mbox_status_available' [-Wunused-function]
drivers/scsi/myrs.c:3005:20: warning: unused function
'DAC960_LP_intr_enabled' [-Wunused-function]
drivers/scsi/myrs.c:3031:30: warning: unused function
'DAC960_LP_read_cmd_ident' [-Wunused-function]
drivers/scsi/qla2xxx/qla_nx.c:384:1: warning: unused function
'qla82xx_pci_set_crbwindow' [-Wunused-function]
drivers/scsi/qla4xxx/ql4_nx.c:3654:1: warning: unused function
'flash_data_addr' [-Wunused-function]
drivers/staging/comedi/drivers/cb_pcidas64.c:232:19: warning: unused
function 'analog_trig_low_threshold_bits' [-Wunused-function]
drivers/staging/comedi/drivers/cb_pcidas64.c:383:28: warning: unused
function 'dma_chain_flag_bits' [-Wunused-function]
drivers/staging/isdn/gigaset/bas-gigaset.c:241:21: warning: unused
function 'usb_pipetype_str' [-Wunused-function]
drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c:2072:18: warning:
unused function 'ieee80211_SignalStrengthTranslate'
[-Wunused-function]
drivers/staging/rts5208/xd.c:34:19: warning: unused function
'xd_check_err_code' [-Wunused-function]
drivers/tty/isicom.c:369:19: warning: unused function
'__isicom_paranoia_check' [-Wunused-function]
drivers/usb/host/sl811-hcd.c:588:18: warning: unused function
'checkdone' [-Wunused-function]
drivers/usb/host/u132-hcd.c:220:28: warning: unused function
'udev_to_u132' [-Wunused-function]
drivers/usb/serial/quatech2.c:179:19: warning: unused function
'qt2_setdevice' [-Wunused-function]
drivers/usb/typec/tps6598x.c:158:19: warning: unused function
'tps6598x_write16' [-Wunused-function]
drivers/usb/typec/tps6598x.c:163:19: warning: unused function
'tps6598x_write32' [-Wunused-function]
drivers/vhost/vhost.c:52:1: warning: unused function
'vhost_umem_interval_tree_iter_next' [-Wunused-function]
drivers/video/fbdev/arkfb.c:321:18: warning: unused function
'dac_read_reg' [-Wunused-function]
drivers/video/fbdev/arkfb.c:328:20: warning: unused function
'dac_read_regs' [-Wunused-function]
drivers/video/fbdev/aty/aty128fb.c:548:18: warning: unused function
'_aty_ld_8' [-Wunused-function]
drivers/video/fbdev/neofb.c:145:20: warning: unused function
'write_le32' [-Wunused-function]
drivers/video/fbdev/tridentfb.c:1127:20: warning: unused function
'shadowmode_off' [-Wunused-function]
drivers/watchdog/it87_wdt.c:152:20: warning: unused function
'superio_outw' [-Wunused-function]
fs/btrfs/extent-tree.c:2723:19: warning: unused function
'heads_to_leaves' [-Wunused-function]
fs/cifs/dfs_cache.c:317:20: warning: unused function
'is_sysvol_or_netlogon' [-Wunused-function]
fs/dlm/lock.c:238:19: warning: unused function 'is_granted' [-Wunused-function]
fs/lockd/xdr.c:109:1: warning: unused function 'nlm_encode_oh'
[-Wunused-function]
fs/nfsd/nfs4state.c:6034:1: warning: unused function 'end_offset'
[-Wunused-function]
fs/ocfs2/dlm/dlmrecovery.c:129:20: warning: unused function
'dlm_reset_recovery' [-Wunused-function]
fs/xfs/xfs_sysfs.c:72:1: warning: unused function 'to_mp' [-Wunused-function]
kernel/locking/rwsem.c:219:20: warning: unused function
'is_rwsem_reader_owned' [-Wunused-function]
kernel/locking/rwsem.c:284:35: warning: unused function 'rwsem_owner'
[-Wunused-function]
kernel/power/snapshot.c:1260:21: warning: unused function
'saveable_highmem_page' [-Wunused-function]
kernel/sched/cputime.c:255:19: warning: unused function
'account_other_time' [-Wunused-function]
kernel/sched/fair.c:4383:19: warning: unused function
'cfs_rq_clock_task' [-Wunused-function]
kernel/trace/trace_events_filter.c:1563:1: warning: unused function
'event_set_no_set_filter_flag' [-Wunused-function]
kernel/trace/trace_events_filter.c:1569:1: warning: unused function
'event_clear_no_set_filter_flag' [-Wunused-function]
kernel/trace/trace_events_filter.c:1575:1: warning: unused function
'event_no_set_filter_flag' [-Wunused-function]
kernel/trace/trace_kprobe.c:96:38: warning: unused function
'trace_kprobe_offset' [-Wunused-function]
lib/zlib_inflate/inffast.c:31:1: warning: unused function
'get_unaligned16' [-Wunused-function]
mm/memcontrol.c:4661:20: warning: unused function 'mem_cgroup_id_get'
[-Wunused-function]
mm/slub.c:1401:29: warning: unused function 'slab_free_hook' [-Wunused-function]
mm/slub.c:2007:28: warning: unused function 'tid_to_cpu' [-Wunused-function]
mm/slub.c:2012:29: warning: unused function 'tid_to_event' [-Wunused-function]
mm/zsmalloc.c:479:20: warning: unused function 'set_zspage_inuse'
[-Wunused-function]
net/bluetooth/6lowpan.c:105:35: warning: unused function
'peer_lookup_ba' [-Wunused-function]
net/bluetooth/6lowpan.c:912:20: warning: unused function 'bdaddr_type'
[-Wunused-function]
net/ipv6/exthdrs.c:712:33: warning: unused function 'ipv6_skb_idev'
[-Wunused-function]
net/ipv6/ip6_gre.c:846:20: warning: unused function
'ip6gre_tnl_addr_conflict' [-Wunused-function]
net/sched/sch_choke.c:145:20: warning: unused function
'choke_set_classid' [-Wunused-function]
net/sunrpc/svcauth_unix.c:301:30: warning: unused function
'ip_map_lookup' [-Wunused-function]
net/sunrpc/svcauth_unix.c:330:19: warning: unused function
'ip_map_update' [-Wunused-function]
security/apparmor/file.c:159:20: warning: unused function 'is_deleted'
[-Wunused-function]
security/apparmor/label.c:1230:20: warning: unused function
'label_is_visible' [-Wunused-function]
sound/drivers/portman2x4.c:186:18: warning: unused function
'portman_read_command' [-Wunused-function]
sound/drivers/portman2x4.c:196:18: warning: unused function
'portman_read_data' [-Wunused-function]
sound/pci/asihpi/asihpi.c:261:19: warning: unused function
'hpi_stream_group_get_map' [-Wunused-function]
sound/pci/azt3328.c:368:1: warning: unused function
'snd_azf3328_codec_outl' [-Wunused-function]
sound/pci/rme9652/hdspm.c:6154:19: warning: unused function
'copy_u32_le' [-Wunused-function]
sound/pci/trident/trident_memory.c:109:21: warning: unused function
'offset_ptr' [-Wunused-function]
sound/pci/ymfpci/ymfpci_main.c:34:18: warning: unused function
'snd_ymfpci_readb' [-Wunused-function]

Hope this helps.

- Sedat -

[1] https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/commit/?h=kbuild&id=025960c034eacc433afd366085077991f8ed6e4e

[Sedat Dilek]

Just as a sidenote:

From [PATCH v2] kbuild: enable unused-function warnings for W= build with Clang:

"Per the documentation [1], -Wno-unused-function will also disable
-Wunneeded-internal-declaration, which can help find bugs like
commit 8289c4b6f2e5 ("platform/x86: mlx-platform: Properly use
mlxplat_mlxcpld_msn201x_items"). (pointed out by Nathan Chancellor)
I added -Wunneeded-internal-declaration to address it.

If you contribute to code clean-up, please run "make CC=clang W=1"
and check -Wunused-function warnings. You will find lots of unused
functions."

Isn't that missing in your double?

- Sedat -

[1] https://lkml.org/lkml/2019/8/27/729

[Nick Desaulniers]

On Thu, Aug 29, 2019 at 11:12 AM Masahiro Yamada
<yamada....@socionext.com> wrote:
>
> Instead of the warning-[123] 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.
>
> [1] 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.
>
> [2] 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.
>
> [3] Currently, 4 Clang warnings (Winitializer-overrides, Wformat,
> Wsign-compare, Wformat-zero-length) are shown by any of W=1, W=2,
> and W=3. With this commit, they will be warned only by W=1. I
> think this is a more correct behavior since each warning belongs
> to only one group.
>
> For understanding this commit correctly:
>
> We have 3 warning groups, W=1, W=2, and W=3. You may think W=3 has a
> higher level than W=1, but they are actually independent. If you like,

What?! Ok now things make much more sense. (This is a great addition
to this patch). Maybe this should additionally be a comment in the
source code?

> you can combine them like W=13. To enable all the warnings, you can
> pass W=123. This is shown by 'make help', but it is often missed
> unfortunately. Since we support W= combination, there should not exist
> intersection among the three groups. If we enable Winitializer-overrides
> for W=1, we do not need to for W=2 or W=3. This is why I believe the
> change [3] makes sense.
>
> The documentation says -Winitializer-overrides is enabled by default.
> (https://clang.llvm.org/docs/DiagnosticsReference.html#winitializer-overrides)
> We negate it by passing -Wno-initializer-overrides for the normal
> build, but we do not do that for W=1. This means, W=1 effectively
> enables -Winitializer-overrides by the clang's default. The same for
> the other three. I wonder if this logic needs detailed commenting,
> but I do not want to be bothered any more. I added comments.
>
> Signed-off-by: Masahiro Yamada <yamada....@socionext.com>
> Reviewed-by: Nathan Chancellor <natecha...@gmail.com>

Acked-by: Nick Desaulniers <ndesau...@google.com>

--
Thanks,
~Nick Desaulniers

[Miguel Ojeda]

On Thu, Aug 29, 2019 at 8:13 PM Masahiro Yamada
<yamada....@socionext.com> wrote:
>

> +# W=1 - warnings that may be relevant and does not occur too often

s/does/do/

Acked-by: Miguel Ojeda <miguel.oje...@gmail.com>

Cheers,
Miguel

[Masahiro Yamada]

Instead of the warning-[123] 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.

[1] 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.

[2] 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.

[3] Currently, 4 Clang warnings (Winitializer-overrides, Wformat,
Wsign-compare, Wformat-zero-length) are shown by any of W=1, W=2,
and W=3. With this commit, they will be warned only by W=1. I
think this is a more correct behavior since each warning belongs
to only one group.

For understanding this commit correctly:

We have 3 warning groups, W=1, W=2, and W=3. You may think W=3 has a
higher level than W=1, but they are actually independent. If you like,

you can combine them like W=13. To enable all the warnings, you can

pass W=123. It is shown by 'make help', but not noticed much. Since we

support W= combination, there should not exist intersection among the
three groups. If we enable Winitializer-overrides for W=1, we do not

need to for W=2 or W=3. This is the reason why I think the change [3]

makes sense.

The documentation says -Winitializer-overrides is enabled by default.
(https://clang.llvm.org/docs/DiagnosticsReference.html#winitializer-overrides)
We negate it by passing -Wno-initializer-overrides for the normal
build, but we do not do that for W=1. This means, W=1 effectively
enables -Winitializer-overrides by the clang's default. The same for
the other three.

Add comments in case people are confused with the code.

Signed-off-by: Masahiro Yamada <yamada....@socionext.com>
Reviewed-by: Nathan Chancellor <natecha...@gmail.com>

Tested-by: Sedat Dilek <sedat...@gmail.com>
Acked-by: Nick Desaulniers <ndesau...@google.com>
Acked-by: Miguel Ojeda <miguel.oje...@gmail.com>
---

Changes in v3:
- Added yet more comments.
Fix grammatical mistake 'does' -> 'do'.

Changes in v2:
- Added comments and more commit log

scripts/Makefile.extrawarn | 106 ++++++++++++++++++++-----------------
1 file changed, 56 insertions(+), 50 deletions(-)

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index a74ce2e3c33e..d226c5fb13e2 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -1,14 +1,9 @@

# SPDX-License-Identifier: GPL-2.0
# ==========================================================================
-#
# make W=... settings

#
-# W=1 - warnings that may be relevant and does not occur too often
-# W=2 - warnings that occur quite often but may still be relevant
-# W=3 - the more obscure warnings, can most likely be ignored
-#
-# $(call cc-option, -W...) handles gcc -W.. options which
-# are not supported by all versions of the compiler

+# There are three warning groups enabled by W=1, W=2, W=3.
+# They are independent, and can be combined like W=12 or W=123.

# ==========================================================================

KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)

@@ -17,58 +12,69 @@ ifeq ("$(origin W)", "command line")

export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)
endif

-ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS
-warning- := $(empty)
+#

+# W=1 - warnings which may be relevant and do not occur too often

+# Some diagnostics enabled by default are noisy.
+# Suppress them by using -Wno... except for W=1.

+
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
+
+endif
+
+#

+# W=2 - warnings which occur quite often but may still be relevant

+#
+ifneq ($(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+
+KBUILD_CFLAGS += -Wcast-align
+KBUILD_CFLAGS += -Wdisabled-optimization
+KBUILD_CFLAGS += -Wnested-externs
+KBUILD_CFLAGS += -Wshadow
+KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
+KBUILD_CFLAGS += -Wmissing-field-initializers
+KBUILD_CFLAGS += -Wsign-compare
+KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
+KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
+
+endif
+
+#

+# W=3 - more obscure warnings, can most likely be ignored

[Masahiro Yamada]

KBUILD_ENABLE_EXTRA_GCC_CHECKS started as a switch to add extra warning
options for GCC, but now it is a historical misnomer since we use it
also for Clang, DTC, and even kernel-doc.

Rename it to more sensible, and shorter KBUILD_EXTRA_WARN.

For the backward compatibility, KBUILD_ENABLE_EXTRA_GCC_CHECKS is still
supported (but not advertised in the documentation).

I also fixed up 'make help', and updated the documentation.

Signed-off-by: Masahiro Yamada <yamada....@socionext.com>
---

Changes in v3:
- new patch

Changes in v2: None

Documentation/kbuild/kbuild.rst | 14 +++++++++-----
Makefile | 2 +-
scripts/Makefile.build | 2 +-
scripts/Makefile.extrawarn | 13 +++++++++----
scripts/Makefile.lib | 4 ++--
scripts/genksyms/Makefile | 2 +-
6 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
index 62f9d86c082c..f1e5dce86af7 100644
--- a/Documentation/kbuild/kbuild.rst
+++ b/Documentation/kbuild/kbuild.rst
@@ -105,6 +105,15 @@ The output directory can also be specified using "O=...".

Setting "O=..." takes precedence over KBUILD_OUTPUT.

+KBUILD_EXTRA_WARN
+-----------------
+Specify the extra build checks. The same value can be assigned by passing
+W=... from the command line.
+
+See `make help` for the list of the supported values.
+
+Setting "W=..." takes precedence over KBUILD_EXTRA_WARN.
+
KBUILD_DEBARCH
--------------
For the deb-pkg target, allows overriding the normal heuristics deployed by
@@ -241,11 +250,6 @@ To get all available archs you can also specify all. E.g.::

$ make ALLSOURCE_ARCHS=all tags

-KBUILD_ENABLE_EXTRA_GCC_CHECKS
-------------------------------
-If enabled over the make command line with "W=1", it turns on additional
-gcc -W... options for more extensive build-time checking.
-
KBUILD_BUILD_TIMESTAMP
----------------------
Setting this to a date string overrides the timestamp used in the
diff --git a/Makefile b/Makefile
index 06e1e21c0f45..016d72eb3ddf 100644
--- a/Makefile
+++ b/Makefile
@@ -1538,7 +1538,7 @@ help:
@echo ' make C=1 [targets] Check re-compiled c source with $$CHECK (sparse by default)'
@echo ' make C=2 [targets] Force check of all c source with $$CHECK'
@echo ' make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections'
- @echo ' make W=n [targets] Enable extra gcc checks, n=1,2,3 where'
+ @echo ' make W=n [targets] Enable extra checks, n=1,2,3 where'
@echo ' 1: warnings which may be relevant and do not occur too often'
@echo ' 2: warnings which occur quite often but may still be relevant'
@echo ' 3: more obscure warnings, can most likely be ignored'
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 2a21ca86b720..f72aba64d611 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -85,7 +85,7 @@ else ifeq ($(KBUILD_CHECKSRC),2)
cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
endif

-ifneq ($(KBUILD_ENABLE_EXTRA_GCC_CHECKS),)
+ifneq ($(KBUILD_EXTRA_WARN),)
cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $<
endif

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index d226c5fb13e2..53eb7e0c6a5a 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -8,14 +8,19 @@

KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)

+# backward compatibility
+KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)
+

ifeq ("$(origin W)", "command line")

- export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)
+ KBUILD_EXTRA_WARN := $(W)
endif

+export KBUILD_EXTRA_WARN
+
#

# W=1 - warnings which may be relevant and do not occur too often

#
-ifneq ($(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)

KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
KBUILD_CFLAGS += -Wmissing-declarations
@@ -48,7 +53,7 @@ endif
#

# W=2 - warnings which occur quite often but may still be relevant

#
-ifneq ($(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)

KBUILD_CFLAGS += -Wcast-align
KBUILD_CFLAGS += -Wdisabled-optimization
@@ -65,7 +70,7 @@ endif
#

# W=3 - more obscure warnings, can most likely be ignored

#
-ifneq ($(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)

KBUILD_CFLAGS += -Wbad-function-cast
KBUILD_CFLAGS += -Wcast-qual
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 7ab17712ab24..df83967268ba 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -248,7 +248,7 @@ quiet_cmd_gzip = GZIP $@
DTC ?= $(objtree)/scripts/dtc/dtc

# Disable noisy checks by default
-ifeq ($(findstring 1,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+ifeq ($(findstring 1,$(KBUILD_EXTRA_WARN)),)
DTC_FLAGS += -Wno-unit_address_vs_reg \
-Wno-unit_address_format \
-Wno-avoid_unnecessary_addr_size \
@@ -259,7 +259,7 @@ DTC_FLAGS += -Wno-unit_address_vs_reg \
-Wno-pci_device_reg
endif

-ifneq ($(findstring 2,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+ifneq ($(findstring 2,$(KBUILD_EXTRA_WARN)),)
DTC_FLAGS += -Wnode_name_chars_strict \
-Wproperty_name_chars_strict
endif
diff --git a/scripts/genksyms/Makefile b/scripts/genksyms/Makefile
index baf44ed0a93a..78629f515e78 100644
--- a/scripts/genksyms/Makefile
+++ b/scripts/genksyms/Makefile
@@ -12,7 +12,7 @@ genksyms-objs := genksyms.o parse.tab.o lex.lex.o
#
# Just in case, run "$(YACC) --version" without suppressing stderr
# so that 'bison: not found' will be displayed if it is missing.
-ifeq ($(findstring 1,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
+ifeq ($(findstring 1,$(KBUILD_EXTRA_WARN)),)

quiet_cmd_bison_no_warn = $(quiet_cmd_bison)
cmd_bison_no_warn = $(YACC) --version >/dev/null; \
--
2.17.1

[Nathan Chancellor]

On Sun, Sep 01, 2019 at 01:25:55AM +0900, Masahiro Yamada wrote:
> KBUILD_ENABLE_EXTRA_GCC_CHECKS started as a switch to add extra warning
> options for GCC, but now it is a historical misnomer since we use it
> also for Clang, DTC, and even kernel-doc.
>
> Rename it to more sensible, and shorter KBUILD_EXTRA_WARN.
>
> For the backward compatibility, KBUILD_ENABLE_EXTRA_GCC_CHECKS is still
> supported (but not advertised in the documentation).
>
> I also fixed up 'make help', and updated the documentation.
>
> Signed-off-by: Masahiro Yamada <yamada....@socionext.com>

Reviewed-by: Nathan Chancellor <natecha...@gmail.com>

[Masahiro Yamada]

On Thu, Aug 29, 2019 at 9:05 AM Nathan Chancellor

I slightly prefer this version.

Either way we go, I want to fix -Wunused-function warnings,
then revert this patch as soon as possible.

[Masahiro Yamada]

On Fri, Aug 30, 2019 at 6:52 PM Sedat Dilek <sedat...@gmail.com> wrote:
>
> Just as a sidenote:
>
> From [PATCH v2] kbuild: enable unused-function warnings for W= build with Clang:
>
> "Per the documentation [1], -Wno-unused-function will also disable
> -Wunneeded-internal-declaration, which can help find bugs like
> commit 8289c4b6f2e5 ("platform/x86: mlx-platform: Properly use
> mlxplat_mlxcpld_msn201x_items"). (pointed out by Nathan Chancellor)
> I added -Wunneeded-internal-declaration to address it.
>
> If you contribute to code clean-up, please run "make CC=clang W=1"
> and check -Wunused-function warnings. You will find lots of unused
> functions."

This information is unrelated to this version,
so I dropped it.

> Isn't that missing in your double?
>
> - Sedat -
>
> [1] https://lkml.org/lkml/2019/8/27/729

[Nick Desaulniers]

On Sat, Aug 31, 2019 at 9:26 AM Masahiro Yamada
<yamada....@socionext.com> wrote:
>
> KBUILD_ENABLE_EXTRA_GCC_CHECKS started as a switch to add extra warning
> options for GCC, but now it is a historical misnomer since we use it
> also for Clang, DTC, and even kernel-doc.

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesau...@google.com>

--
Thanks,
~Nick Desaulniers

[Sedat Dilek]

On Tue, Sep 3, 2019 at 11:50 PM Nick Desaulniers
<ndesau...@google.com> wrote:
>
> On Sat, Aug 31, 2019 at 9:26 AM Masahiro Yamada
> <yamada....@socionext.com> wrote:
> >
> > KBUILD_ENABLE_EXTRA_GCC_CHECKS started as a switch to add extra warning
> > options for GCC, but now it is a historical misnomer since we use it
> > also for Clang, DTC, and even kernel-doc.
>
> Thanks for the patch!
> Reviewed-by: Nick Desaulniers <ndesau...@google.com>
>

Thanks for the patch.
I like the backward compatibility and am OK with pointing to 'make
--help' for the documentation part (KISS - Keep It Simple and
Short/Stupid).

Reviewed-by: Sedat Dilek <sedat...@gmail.com>

- Sedat -

[Sedat Dilek]

On Wed, Sep 4, 2019 at 8:58 AM Sedat Dilek <sedat...@gmail.com> wrote:
>
> On Tue, Sep 3, 2019 at 11:50 PM Nick Desaulniers
> <ndesau...@google.com> wrote:
> >
> > On Sat, Aug 31, 2019 at 9:26 AM Masahiro Yamada
> > <yamada....@socionext.com> wrote:
> > >
> > > KBUILD_ENABLE_EXTRA_GCC_CHECKS started as a switch to add extra warning
> > > options for GCC, but now it is a historical misnomer since we use it
> > > also for Clang, DTC, and even kernel-doc.
> >
> > Thanks for the patch!
> > Reviewed-by: Nick Desaulniers <ndesau...@google.com>
> >
>
> Thanks for the patch.
> I like the backward compatibility and am OK with pointing to 'make
> --help' for the documentation part (KISS - Keep It Simple and
> Short/Stupid).
>
> Reviewed-by: Sedat Dilek <sedat...@gmail.com>

If you will do a next version...

- @echo ' make W=n [targets] Enable extra gcc checks, n=1,2,3 where'
+ @echo ' make W=n [targets] Enable extra checks, n=1,2,3 where'

...clarify on extra checks for compiler...

+ @echo ' make W=n [targets] Enable extra *compiler* checks, n=1,2,3 where'

Thanks in advance.

- Sedat -

[Sedat Dilek]

+KBUILD_EXTRA_WARN
+-----------------
+Specify the extra build checks. The same value can be assigned by passing
+W=... from the command line.

For consistency reasons might be better:

- @echo ' make W=n [targets] Enable extra gcc checks, n=1,2,3 where'

+ @echo ' make W=n [targets] Enable extra build checks, n=1,2,3 where'

- Sedat -

[Masahiro Yamada]

OK, I will squash this. Thanks.

[Arnd Bergmann]

On Sat, Aug 31, 2019 at 6:26 PM Masahiro Yamada
<yamada....@socionext.com> wrote:

> +# Some diagnostics enabled by default are noisy.
> +# Suppress them by using -Wno... except for W=1.
> +
> 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

FWIW, I just found out I missed a bug that clang failed to warn about
because of the -Wno-format. Apparently gcc warns only about type
mismatches that result in incompatible calling conventions (e.g.
int vs int64_t) but not smaller types (int, short) that get converted to an
int anyway. Passing -Wno-format turns both off.

Arnd

[Nathan Chancellor]

Hi Arnd,

This has been fixed in clang 10.0.0 but this areas has not been updated
as nobody has sent a patch yet:

https://github.com/ClangBuiltLinux/linux/issues/378#issuecomment-524411147

Cheers,
Nathan

[Arnd Bergmann]

Ok, that's good. I see that on clang-9, the documentation also
mentions that -Wformat control -Wformat-extra-args -Wformat-invalid-specifier
-Wformat-y2k -Wformat-zero-length -Wnonnull and -Wformat-security.
We can probably turn these all on, regardless. The only warning
that produces output here is -Wformat-security, and only in a couple of
files (number of warnings per file from a few hundred randconfig builds):

384 kernel/trace/ring_buffer_benchmark.c
176 samples/trace_printk/trace-printk.c
174 kernel/debug/kdb/kdb_io.c
102 arch/x86/kernel/e820.c
80 fs/btrfs/check-integrity.c
67 fs/reiserfs/prints.c
63 fs/xfs/xfs_log_recover.c
54 fs/quota/dquot.c
53 lib/test_printf.c
39 sound/core/sound.c
28 arch/x86/kernel/cpu/mce/core.c
21 kernel/trace/preemptirq_delay_test.c
19 sound/core/seq/seq_clientmgr.c
17 sound/pci/hda/hda_bind.c
16 sound/usb/mixer_quirks.c
16 arch/x86/kernel/cpu/mce/amd.c
15 net/smc/smc_ism.c
12 kernel/debug/kdb/kdb_main.c
8 net/netfilter/nf_conntrack_helper.c
4 kernel/power/suspend_test.c
3 sound/pci/rme32.c
3 net/dsa/dsa.c
2 sound/pci/rme96.c
1 sound/soc/sof/intel/hda-codec.c
1 sound/pci/korg1212/korg1212.c

Arnd

[Masahiro Yamada]

Both applied to linux-kbuild.

[Masahiro Yamada]

GCC and Clang have different policy for -Wunused-function; GCC does not
warn unused static inline functions at all whereas Clang does if they
are defined in source files instead of included headers although it has
been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress
warning for unused static inline functions").

We often miss to delete unused functions where 'static inline' is used
in *.c files since there is no tool to detect them. Unused code remains
until somebody notices. For example, commit 075ddd75680f ("regulator:
core: remove unused rdev_get_supply()").

Let's remove __maybe_unused from the inline macro to allow Clang to
start finding unused static inline functions. For now, we do this only
for W=1 build since it is not a good idea to sprinkle warnings for the

normal build (e.g. 35 warnings for arch/x86/configs/x86_64_defconfig).

My initial attempt was to add -Wno-unused-function for no W= build

(https://lore.kernel.org/patchwork/patch/1120594/)

Nathan Chancellor pointed out that would weaken Clang's checks since
we would no longer get -Wunused-function without W=1. It is true GCC

would catch unused static non-inline functions, but it would weaken
Clang as a standalone compiler, at least.

Hence, here is a counter implementation. The current problem is, W=...

only controls compiler flags, which are globally effective. There is

no way to address only 'static inline' functions.

This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123].
When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from
the 'inline' macro.

The new macro __inline_maybe_unused makes the code a bit uglier, so I
hope we can remove it entirely after fixing most of the warnings.

If you contribute to code clean-up, please run "make CC=clang W=1"
and check -Wunused-function warnings. You will find lots of unused
functions.

Some of them are false-positives because the call-sites are disabled
by #ifdef. I do not like to abuse the inline keyword for suppressing
unused-function warnings because it is intended to be a hint for the
compiler optimization. I prefer #ifdef around the definition, or
__maybe_unused if #ifdef would make the code too ugly.

Signed-off-by: Masahiro Yamada <yamada....@socionext.com>
Reviewed-by: Nathan Chancellor <natecha...@gmail.com>

Tested-by: Nathan Chancellor <natecha...@gmail.com>
---

Changes in v2:
- Rebase on top of https://patchwork.kernel.org/patch/11124933/

include/linux/compiler_types.h | 20 ++++++++++++++------
scripts/Makefile.extrawarn | 6 ++++++
2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 599c27b56c29..b056a40116da 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -130,10 +130,6 @@ struct ftrace_likely_data {

/*
* Force always-inline if the user requests it so via the .config.
- * GCC does not warn about unused static inline functions for
- * -Wunused-function. This turns out to avoid the need for complex #ifdef
- * directives. Suppress the warning in clang as well by using "unused"
- * function attribute, which is redundant but not harmful for gcc.
* Prefer gnu_inline, so that extern inline functions do not emit an
* externally visible function. This makes extern inline behave as per gnu89
* semantics rather than c99. This prevents multiple symbol definition errors
@@ -144,15 +140,27 @@ struct ftrace_likely_data {
*/
#if !defined(CONFIG_OPTIMIZE_INLINING)
#define inline inline __attribute__((__always_inline__)) __gnu_inline \
- __maybe_unused notrace
+ __inline_maybe_unused notrace
#else
#define inline inline __gnu_inline \
- __maybe_unused notrace
+ __inline_maybe_unused notrace
#endif

#define __inline__ inline
#define __inline inline

+/*
+ * GCC does not warn about unused static inline functions for -Wunused-function.
+ * Suppress the warning in clang as well by using __maybe_unused, but enable it
+ * for W=1 build. This will allow clang to find unused functions. Remove the
+ * __inline_maybe_unused entirely after fixing most of -Wunused-function warnings.
+ */
+#ifdef KBUILD_EXTRA_WARN1
+#define __inline_maybe_unused
+#else
+#define __inline_maybe_unused __maybe_unused
+#endif
+
/*
* Rather then using noinline to prevent stack consumption, use
* noinline_for_stack instead. For documentation reasons.
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 53eb7e0c6a5a..ecddf83ac142 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -36,6 +36,8 @@ KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
KBUILD_CFLAGS += -Wno-missing-field-initializers
KBUILD_CFLAGS += -Wno-sign-compare

+KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
+
else

# Some diagnostics enabled by default are noisy.

@@ -65,6 +67,8 @@ KBUILD_CFLAGS += -Wsign-compare
KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)

+KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
+
endif

#
@@ -82,4 +86,6 @@ KBUILD_CFLAGS += -Wredundant-decls
KBUILD_CFLAGS += -Wswitch-default
KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)

+KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
+
endif
--
2.17.1

[Masahiro Yamada]

Applied to linux-kbuild.