[PATCH v2] kbuild: refactor scripts/Makefile.extrawarn

[PATCH v2] 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 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.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@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
 
-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
 
+# 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
+
+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

Re: [PATCH v2] kbuild: refactor scripts/Makefile.extrawarn

[Sedat Dilek]

On Thu, Aug 29, 2019 at 8:13 PM Masahiro Yamada
<yamada.masahiro@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,
> 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.masahiro@socionext.com>
> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
>
> Changes in v2:
>   - Added comments and more commit log
>
>  scripts/Makefile.extrawarn | 105 +++++++++++++++++++------------------
>  1 file changed, 54 insertions(+), 51 deletions(-)
>

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 -

Re: [PATCH v2] kbuild: refactor scripts/Makefile.extrawarn

[Sedat Dilek]

On Thu, Aug 29, 2019 at 8:13 PM Masahiro Yamada
<yamada.masahiro@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,
> 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.masahiro@socionext.com>
> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

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

- Sedat -

> ---
>
> 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
>
> -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 += $(warning)
>  else
>
> +# Some diagnostics such as -Winitializer-overrides are enabled by default.
> +# We suppress them by using -Wno... except for W=1.
> +
>  ifdef CONFIG_CC_IS_CLANG
>  KBUILD_CFLAGS += -Wno-initializer-overrides
>  KBUILD_CFLAGS += -Wno-format
>  KBUILD_CFLAGS += -Wno-sign-compare
>  KBUILD_CFLAGS += -Wno-format-zero-length
>  endif
> +
> +endif
> +
> +#
> +# W=2 - warnings that occur quite often but may still be relevant
> +#
> +ifneq ($(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
>

Re: [PATCH v2] kbuild: refactor scripts/Makefile.extrawarn

[Nick Desaulniers]

On Thu, Aug 29, 2019 at 11:12 AM Masahiro Yamada
<yamada.masahiro@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.masahiro@socionext.com>
> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

Acked-by: Nick Desaulniers <ndesaulniers@google.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
>
> -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 += $(warning)
>  else
>
> +# Some diagnostics such as -Winitializer-overrides are enabled by default.
> +# We suppress them by using -Wno... except for W=1.
> +
>  ifdef CONFIG_CC_IS_CLANG
>  KBUILD_CFLAGS += -Wno-initializer-overrides
>  KBUILD_CFLAGS += -Wno-format
>  KBUILD_CFLAGS += -Wno-sign-compare
>  KBUILD_CFLAGS += -Wno-format-zero-length
>  endif
> +
> +endif
> +
> +#
> +# W=2 - warnings that occur quite often but may still be relevant
> +#
> +ifneq ($(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
>


-- 
Thanks,
~Nick Desaulniers

Re: [PATCH v2] kbuild: refactor scripts/Makefile.extrawarn

[Miguel Ojeda]

On Thu, Aug 29, 2019 at 8:13 PM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> +# W=1 - warnings that may be relevant and does not occur too often

s/does/do/

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

Cheers,
Miguel