kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1

[ Upstream commit 75b5ab134bb5f657ef7979a59106dce0657e8d87 ]

Clang enables -Wenum-enum-conversion and -Wenum-compare-conditional
u

kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1

[ Upstream commit 75b5ab134bb5f657ef7979a59106dce0657e8d87 ]

Clang enables -Wenum-enum-conversion and -Wenum-compare-conditional
under -Wenum-conversion. A recent change in Clang strengthened these
warnings and they appear frequently in common builds, primarily due to
several instances in common headers but there are quite a few drivers
that have individual instances as well.

include/linux/vmstat.h:508:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
508 | return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
| ~~~~~~~~~~~~~~~~~~~~~ ^
509 | item];
| ~~~~

drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c:955:24: warning: conditional expression between different enumeration types ('enum iwl_mac_beacon_flags' and 'enum iwl_mac_beacon_flags_v1') [-Wenum-compare-conditional]
955 | flags |= is_new_rate ? IWL_MAC_BEACON_CCK
| ^ ~~~~~~~~~~~~~~~~~~
956 | : IWL_MAC_BEACON_CCK_V1;
| ~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c:1120:21: warning: conditional expression between different enumeration types ('enum iwl_mac_beacon_flags' and 'enum iwl_mac_beacon_flags_v1') [-Wenum-compare-conditional]
1120 | 0) > 10 ?
| ^
1121 | IWL_MAC_BEACON_FILS :
| ~~~~~~~~~~~~~~~~~~~
1122 | IWL_MAC_BEACON_FILS_V1;
| ~~~~~~~~~~~~~~~~~~~~~~

Doing arithmetic between or returning two different types of enums could
be a bug, so each of the instance of the warning needs to be evaluated.
Unfortunately, as mentioned above, there are many instances of this
warning in many different configurations, which can break the build when
CONFIG_WERROR is enabled.

To avoid introducing new instances of the warnings while cleaning up the
disruption for the majority of users, disable these warnings for the
default build while leaving them on for W=1 builds.

Cc: stable@vger.kernel.org
Closes: https://github.com/ClangBuiltLinux/linux/issues/2002
Link: https://github.com/llvm/llvm-project/commit/8c2ae42b3e1c6aa7c18f873edcebff7c0b45a37e
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1

[ Upstream commit 75b5ab134bb5f657ef7979a59106dce0657e8d87 ]

Clang enables -Wenum-enum-conversion and -Wenum-compare-conditional
u

kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1

[ Upstream commit 75b5ab134bb5f657ef7979a59106dce0657e8d87 ]

Clang enables -Wenum-enum-conversion and -Wenum-compare-conditional
under -Wenum-conversion. A recent change in Clang strengthened these
warnings and they appear frequently in common builds, primarily due to
several instances in common headers but there are quite a few drivers
that have individual instances as well.

include/linux/vmstat.h:508:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
508 | return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
| ~~~~~~~~~~~~~~~~~~~~~ ^
509 | item];
| ~~~~

drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c:955:24: warning: conditional expression between different enumeration types ('enum iwl_mac_beacon_flags' and 'enum iwl_mac_beacon_flags_v1') [-Wenum-compare-conditional]
955 | flags |= is_new_rate ? IWL_MAC_BEACON_CCK
| ^ ~~~~~~~~~~~~~~~~~~
956 | : IWL_MAC_BEACON_CCK_V1;
| ~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c:1120:21: warning: conditional expression between different enumeration types ('enum iwl_mac_beacon_flags' and 'enum iwl_mac_beacon_flags_v1') [-Wenum-compare-conditional]
1120 | 0) > 10 ?
| ^
1121 | IWL_MAC_BEACON_FILS :
| ~~~~~~~~~~~~~~~~~~~
1122 | IWL_MAC_BEACON_FILS_V1;
| ~~~~~~~~~~~~~~~~~~~~~~

Doing arithmetic between or returning two different types of enums could
be a bug, so each of the instance of the warning needs to be evaluated.
Unfortunately, as mentioned above, there are many instances of this
warning in many different configurations, which can break the build when
CONFIG_WERROR is enabled.

To avoid introducing new instances of the warnings while cleaning up the
disruption for the majority of users, disable these warnings for the
default build while leaving them on for W=1 builds.

Cc: stable@vger.kernel.org
Closes: https://github.com/ClangBuiltLinux/linux/issues/2002
Link: https://github.com/llvm/llvm-project/commit/8c2ae42b3e1c6aa7c18f873edcebff7c0b45a37e
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

extrawarn: move -Wrestrict into W=1 warnings

There are few of these, so enable them whenever W=1 is enabled.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <masahiroy@k

extrawarn: move -Wrestrict into W=1 warnings

There are few of these, so enable them whenever W=1 is enabled.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

extrawarn: enable format and stringop overflow warnings in W=1

The stringop and format warnings got disabled globally when they were
newly introduced in commit bd664f6b3e376 ("disable new gcc-7.1.1

extrawarn: enable format and stringop overflow warnings in W=1

The stringop and format warnings got disabled globally when they were
newly introduced in commit bd664f6b3e376 ("disable new gcc-7.1.1 warnings
for now"), 217c3e0196758 ("disable stringop truncation warnings for now")
and 5a76021c2eff7 ("gcc-10: disable 'stringop-overflow' warning for now").

In all cases, the sentiment at the time was that the warnings are
useful, and we actually addressed a number of real bugs based on
them, but we never managed to eliminate them all because even the
build bots using W=1 builds only see the -Wstringop-truncation
warnings that are enabled at that level.

Move these into the W=1 section to give them a larger build coverage
and actually eliminate them over time.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

kbuild: avoid duplicate warning options

Some warning options are disabled at one place and then conditionally
re-enabled later in scripts/Makefile.extrawarn.

For consistency, rework this file so ea

kbuild: avoid duplicate warning options

Some warning options are disabled at one place and then conditionally
re-enabled later in scripts/Makefile.extrawarn.

For consistency, rework this file so each of those warnings only
gets etiher enabled or disabled based on the W= flags but not both.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

kbuild: consolidate warning flags in scripts/Makefile.extrawarn

Warning options are enabled and disabled in inconsistent ways and
inconsistent locations. Start rearranging those by moving all option

kbuild: consolidate warning flags in scripts/Makefile.extrawarn

Warning options are enabled and disabled in inconsistent ways and
inconsistent locations. Start rearranging those by moving all options
into Makefile.extrawarn.

This should not change any behavior, but makes sure we can group them
in a way that ensures that each warning that got temporarily disabled
is turned back on at an appropriate W=1 level later on.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds

The use of an undefined macro in an #if directive is warned, but only
in *.c files. No warning from other files such as *.S, *.lds.S.

Since -Wu

kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds

The use of an undefined macro in an #if directive is warned, but only
in *.c files. No warning from other files such as *.S, *.lds.S.

Since -Wundef is a preprocessor-related warning, it should be added to
KBUILD_CPPFLAGS instead of KBUILD_CFLAGS.

My previous attempt [1] uncovered several issues. I could not finish
fixing them all.

This commit adds -Wundef to KBUILD_CPPFLAGS for W=1 builds in order to
block new breakages. (The kbuild test robot tests with W=1)

We can fix the warnings one by one. After fixing all of them, we can
make it default in the top Makefile, and remove -Wundef from
KBUILD_CFLAGS.

[1]: https://lore.kernel.org/all/20221012180118.331005-2-masahiroy@kernel.org/

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

show more ...

Makefile.extrawarn: Move -Wcast-function-type-strict to W=1

We enable -Wcast-function-type globally in the kernel to warn about
mismatching types in function pointer casts. Compilers currently
warn

Makefile.extrawarn: Move -Wcast-function-type-strict to W=1

We enable -Wcast-function-type globally in the kernel to warn about
mismatching types in function pointer casts. Compilers currently
warn only about ABI incompability with this flag, but Clang 16 will
enable a stricter version of the check by default that checks for an
exact type match. This will be very noisy in the kernel, so disable
-Wcast-function-type-strict without W=1 until the new warnings have
been addressed.

Cc: stable@vger.kernel.org
Link: https://reviews.llvm.org/D134831
Link: https://github.com/ClangBuiltLinux/linux/issues/1724
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220930203310.4010564-1-samitolvanen@google.com

show more ...

Makefile.compiler: replace cc-ifversion with compiler-specific macros

cc-ifversion is GCC specific. Replace it with compiler specific
variants. Update the users of cc-ifversion to use these new macr

Makefile.compiler: replace cc-ifversion with compiler-specific macros

cc-ifversion is GCC specific. Replace it with compiler specific
variants. Update the users of cc-ifversion to use these new macros.

Link: https://github.com/ClangBuiltLinux/linux/issues/350
Link: https://lore.kernel.org/llvm/CAGG=3QWSAUakO42kubrCap8fp-gm1ERJJAYXTnP1iHk_wrH=BQ@mail.gmail.com/
Suggested-by: Bill Wendling <morbo@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

Makefile.extrawarn: re-enable -Wformat for clang; take 2

-Wformat was recently re-enabled for builds with clang, then quickly
re-disabled, due to concerns stemming from the frequency of default
argu

Makefile.extrawarn: re-enable -Wformat for clang; take 2

-Wformat was recently re-enabled for builds with clang, then quickly
re-disabled, due to concerns stemming from the frequency of default
argument promotion related warning instances.

commit 258fafcd0683 ("Makefile.extrawarn: re-enable -Wformat for clang")
commit 21f9c8a13bb2 ("Revert "Makefile.extrawarn: re-enable -Wformat for clang"")

ISO WG14 has ratified N2562 to address default argument promotion
explicitly for printf, as part of the upcoming ISO C2X standard.

The behavior of clang was changed in clang-16 to not warn for the cited
cases in all language modes.

Add a version check, so that users of clang-16 now get the full effect
of -Wformat. For older clang versions, re-enable flags under the
-Wformat group that way users still get some useful checks related to
format strings, without noisy default argument promotion warnings. I
intentionally omitted -Wformat-y2k and -Wformat-security from being
re-enabled, which are also part of -Wformat in clang-16.

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Link: https://github.com/llvm/llvm-project/issues/57102
Link: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2562.pdf
Suggested-by: Justin Stitt <jstitt007@gmail.com>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Youngmin Nam <youngmin.nam@samsung.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

scripts/Makefile.extrawarn: Do not disable clang's -Wformat-zero-length

There are no instances of this warning in the tree across several
difference architectures and configurations. This was added

scripts/Makefile.extrawarn: Do not disable clang's -Wformat-zero-length

There are no instances of this warning in the tree across several
difference architectures and configurations. This was added by
commit 26ea6bb1fef0 ("kbuild, LLVMLinux: Supress warnings unless W=1-3")
back in 2014, where it might have been necessary, but there are no
instances of it now so stop disabling it to increase warning coverage
for clang.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

Revert "Makefile.extrawarn: re-enable -Wformat for clang"

This reverts commit 258fafcd0683d9ccfa524129d489948ab3ddc24c.

The clang -Wformat warning is terminally broken, and the clang people
can't s

Revert "Makefile.extrawarn: re-enable -Wformat for clang"

This reverts commit 258fafcd0683d9ccfa524129d489948ab3ddc24c.

The clang -Wformat warning is terminally broken, and the clang people
can't seem to get their act together.

This test program causes a warning with clang:

#include <stdio.h>

int main(int argc, char **argv)
{
printf("%hhu\n", 'a');
}

resulting in

t.c:5:19: warning: format specifies type 'unsigned char' but the argument has type 'int' [-Wformat]
printf("%hhu\n", 'a');
~~~~ ^~~
%d

and apparently clang people consider that a feature, because they don't
want to face the reality of how either C character constants, C
arithmetic, and C varargs functions work.

The rest of the world just shakes their head at that kind of
incompetence, and turns off -Wformat for clang again.

And no, the "you should use a pointless cast to shut this up" is not a
valid answer. That warning should not exist in the first place, or at
least be optinal with some "-Wformat-me-harder" kind of option.

[ Admittedly, there's also very little reason to *ever* use '%hh[ud]' in
C, but what little reason there is is entirely about 'I want to see
only the low 8 bits of the argument'. So I would suggest nobody ever
use that format in the first place, but if they do, the clang
behavious is simply always wrong. Because '%hhu' takes an 'int'. It's
that simple. ]

Reported-by: Sudip Mukherjee (Codethink) <sudipm.mukherjee@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

Makefile.extrawarn: re-enable -Wformat for clang

There's been an ongoing mission to re-enable the -Wformat warning for
Clang. A previous attempt at enabling the warning showed that there were
many i

Makefile.extrawarn: re-enable -Wformat for clang

There's been an ongoing mission to re-enable the -Wformat warning for
Clang. A previous attempt at enabling the warning showed that there were
many instances of this warning throughout the codebase. The sheer amount
of these warnings really polluted builds and thus -Wno-format was added
to _temporarily_ toggle them off.

After many patches the warning has largely been eradicated for x86,
x86_64, arm, and arm64 on a variety of configs. The time to enable the
warning has never been better as it seems for the first time we are
ahead of them and can now solve them as they appear rather than tackling
from a backlog.

As to the root cause of this large backlog of warnings, Clang seems to
pickup on some more nuanced cases of format warnings caused by implicit
integer conversion as well as default argument promotions from
printf-like functions.

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

kbuild: support W=e to make build abort in case of warning

When developing new code/feature, CONFIG_WERROR is most
often turned off, especially for people using make W=12 to
get more warnings.

In s

kbuild: support W=e to make build abort in case of warning

When developing new code/feature, CONFIG_WERROR is most
often turned off, especially for people using make W=12 to
get more warnings.

In such case, turning on -Werror temporarily would require
switching on CONFIG_WERROR in the configuration, building,
then switching off CONFIG_WERROR.

For this use case, this patch introduces a new 'e' modifier
to W= as a short hand for KCFLAGS+=-Werror" so that -Werror
got added to the kernel (built-in) and modules' CFLAGS.

Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

Kbuild: add -Wno-shift-negative-value where -Wextra is used

As a preparation for moving to -std=gnu11, turn off the
-Wshift-negative-value option. This warning is enabled by gcc when
building with -

Kbuild: add -Wno-shift-negative-value where -Wextra is used

As a preparation for moving to -std=gnu11, turn off the
-Wshift-negative-value option. This warning is enabled by gcc when
building with -Wextra for c99 or higher, but not for c89. Since
the kernel already relies on well-defined overflow behavior,
the warning is not helpful and can simply be disabled in
all locations that use -Wextra.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang v13.0.0 (x86-64)
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

Makefile.extrawarn: Move -Wunaligned-access to W=1

-Wunaligned-access is a new warning in clang that is default enabled for
arm and arm64 under certain circumstances within the clang frontend (see
L

Makefile.extrawarn: Move -Wunaligned-access to W=1

-Wunaligned-access is a new warning in clang that is default enabled for
arm and arm64 under certain circumstances within the clang frontend (see
LLVM commit below). On v5.17-rc2, an ARCH=arm allmodconfig build shows
1284 total/70 unique instances of this warning (most of the instances
are in header files), which is quite noisy.

To keep a normal build green through CONFIG_WERROR, only show this
warning with W=1, which will allow automated build systems to catch new
instances of the warning so that the total number can be driven down to
zero eventually since catching unaligned accesses at compile time would
be generally useful.

Cc: stable@vger.kernel.org
Link: https://github.com/llvm/llvm-project/commit/35737df4dcd28534bd3090157c224c19b501278a
Link: https://github.com/ClangBuiltLinux/linux/issues/1569
Link: https://github.com/ClangBuiltLinux/linux/issues/1576
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

Makefile.extrawarn: Move -Wcast-function-type-strict to W=1

commit 2120635108b35ecad9c59c8b44f6cbdf4f98214e upstream.

We enable -Wcast-function-type globally in the kernel to warn about
mismatching

Makefile.extrawarn: Move -Wcast-function-type-strict to W=1

commit 2120635108b35ecad9c59c8b44f6cbdf4f98214e upstream.

We enable -Wcast-function-type globally in the kernel to warn about
mismatching types in function pointer casts. Compilers currently
warn only about ABI incompability with this flag, but Clang 16 will
enable a stricter version of the check by default that checks for an
exact type match. This will be very noisy in the kernel, so disable
-Wcast-function-type-strict without W=1 until the new warnings have
been addressed.

Cc: stable@vger.kernel.org
Link: https://reviews.llvm.org/D134831
Link: https://github.com/ClangBuiltLinux/linux/issues/1724
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220930203310.4010564-1-samitolvanen@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Makefile.extrawarn: Move -Wunaligned-access to W=1

commit 1cf5f151d25fcca94689efd91afa0253621fb33a upstream.

-Wunaligned-access is a new warning in clang that is default enabled for
arm and arm64 u

Makefile.extrawarn: Move -Wunaligned-access to W=1

commit 1cf5f151d25fcca94689efd91afa0253621fb33a upstream.

-Wunaligned-access is a new warning in clang that is default enabled for
arm and arm64 under certain circumstances within the clang frontend (see
LLVM commit below). On v5.17-rc2, an ARCH=arm allmodconfig build shows
1284 total/70 unique instances of this warning (most of the instances
are in header files), which is quite noisy.

To keep a normal build green through CONFIG_WERROR, only show this
warning with W=1, which will allow automated build systems to catch new
instances of the warning so that the total number can be driven down to
zero eventually since catching unaligned accesses at compile time would
be generally useful.

Cc: stable@vger.kernel.org
Link: https://github.com/llvm/llvm-project/commit/35737df4dcd28534bd3090157c224c19b501278a
Link: https://github.com/ClangBuiltLinux/linux/issues/1569
Link: https://github.com/ClangBuiltLinux/linux/issues/1576
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Makefile.extrawarn: remove -Wnested-externs warning

The -Wnested-externs warning has become useless with gcc, since
this warns every time that BUILD_BUG_ON() or similar macros
are used.

With clang,

Makefile.extrawarn: remove -Wnested-externs warning

The -Wnested-externs warning has become useless with gcc, since
this warns every time that BUILD_BUG_ON() or similar macros
are used.

With clang, the warning option does nothing to start with, so
just remove it entirely.

Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

Makefile.extrawarn: move -Wcast-align to W=3

This warning behaves differently depending on the architecture
and compiler. Using x86 gcc, we get no output at all because
gcc knows the architecture ca

Makefile.extrawarn: move -Wcast-align to W=3

This warning behaves differently depending on the architecture
and compiler. Using x86 gcc, we get no output at all because
gcc knows the architecture can handle unaligned accesses.

Using x86 clang, or gcc on an architecture that needs to
manually deal with unaligned accesses, the build log is
completely flooded with these warnings, as they are commonly
invoked by inline functions of networking headers, e.g.

include/linux/skbuff.h:1426:26: warning: cast increases required alignment of target type [-Wcast-align]

The compiler is correct to point this out, as we are dealing
with undefined behavior that does cause problems in practice,
but there is also no good way to rewrite the code in commonly
included headers to a safer method.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

Makefile.extrawarn: Move sign-compare from W=2 to W=3

This -Wsign-compare compiler warning can be very noisy
and most of the suggested conversions are unnecessary.

Make the warning W=3 so it's desc

Makefile.extrawarn: Move sign-compare from W=2 to W=3

This -Wsign-compare compiler warning can be very noisy
and most of the suggested conversions are unnecessary.

Make the warning W=3 so it's described under the
"can most likely be ignored" block.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

kbuild: Move -Wtype-limits to W=2

-Wtype-limits is included in -Wextra which is added at W=1. It warns
(among other things) that 'comparison of an unsigned variable `< 0` is
always false. This cause

kbuild: Move -Wtype-limits to W=2

-Wtype-limits is included in -Wextra which is added at W=1. It warns
(among other things) that 'comparison of an unsigned variable `< 0` is
always false. This causes noisy warnings, especially when used in
macros, hence it is more suitable for W=2.

Link: https://lore.kernel.org/lkml/CAHk-=wiKCXEWKJ9dWUimGbrVRo_N2RosESUw8E7m9AEtyZcu=w@mail.gmail.com/
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

kbuild: Enable -Wtautological-compare

Currently, we disable -Wtautological-compare, which in turn disables a
bunch of more specific tautological comparison warnings that are useful
for the kernel su

kbuild: Enable -Wtautological-compare

Currently, we disable -Wtautological-compare, which in turn disables a
bunch of more specific tautological comparison warnings that are useful
for the kernel such as -Wtautological-bitwise-compare. See clang's
documentation below for the other warnings that are suppressed by
-Wtautological-compare. Now that all of the major/noisy warnings have
been fixed, enable -Wtautological-compare so that more issues can be
caught at build time by various continuous integration setups.

-Wtautological-constant-out-of-range-compare is kept disabled under a
normal build but visible at W=1 because there are places in the kernel
where a constant or variable size can change based on the kernel
configuration. These are not fixed in a clean/concise way and the ones
I have audited so far appear to be harmless. It is not a subgroup but
rather just one warning so we do not lose out on much coverage by
default.

Link: https://github.com/ClangBuiltLinux/linux/issues/488
Link: http://releases.llvm.org/10.0.0/tools/clang/docs/DiagnosticsReference.html#wtautological-compare
Link: https://bugs.llvm.org/show_bug.cgi?id=42666
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

kbuild: Disable -Wpointer-to-enum-cast

Clang's -Wpointer-to-int-cast deviates from GCC in that it warns when
casting to enums. The kernel does this in certain places, such as device
tree matches to

kbuild: Disable -Wpointer-to-enum-cast

Clang's -Wpointer-to-int-cast deviates from GCC in that it warns when
casting to enums. The kernel does this in certain places, such as device
tree matches to set the version of the device being used, which allows
the kernel to avoid using a gigantic union.

https://elixir.bootlin.com/linux/v5.5.8/source/drivers/ata/ahci_brcm.c#L428
https://elixir.bootlin.com/linux/v5.5.8/source/drivers/ata/ahci_brcm.c#L402
https://elixir.bootlin.com/linux/v5.5.8/source/include/linux/mod_devicetable.h#L264

To avoid a ton of false positive warnings, disable this particular part
of the warning, which has been split off into a separate diagnostic so
that the entire warning does not need to be turned off for clang. It
will be visible under W=1 in case people want to go about fixing these
easily and enabling the warning treewide.

Cc: stable@vger.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/887
Link: https://github.com/llvm/llvm-project/commit/2a41b31fcdfcb67ab7038fc2ffb606fd50b83a84
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

kbuild: allow Clang to find unused static inline functions for W=1 build

GCC and Clang have different policy for -Wunused-function; GCC does not
warn unused static inline functions at all whereas Cl

kbuild: allow Clang to find unused static inline functions for W=1 build

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.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>

show more ...