user/sven/linux.git/scripts/Makefile.extrawarn, branch v5.4.177

kbuild: Disable -Wpointer-to-enum-cast

2020-03-25T07:25:54Z

commit 82f2bc2fcc0160d6f82dd1ac64518ae0a4dd183f upstream. 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 Signed-off-by: Masahiro Yamada Signed-off-by: Greg Kroah-Hartman

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

2019-09-09T14:55:43Z

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 Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor

kbuild: rename KBUILD_ENABLE_EXTRA_GCC_CHECKS to KBUILD_EXTRA_WARN

2019-09-06T14:46:52Z

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, 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 Reviewed-by: Nathan Chancellor Reviewed-by: Nick Desaulniers Reviewed-by: Sedat Dilek

kbuild: refactor scripts/Makefile.extrawarn

2019-09-06T14:46:52Z

Instead of the warning-[123] magic, let's accumulate compiler options to KBUILD_CFLAGS directly as the top Makefile does. I think this makes it 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 Reviewed-by: Nathan Chancellor Tested-by: Sedat Dilek Acked-by: Nick Desaulniers Acked-by: Miguel Ojeda

kbuild: Remove unnecessary -Wno-unused-value

2019-06-23T18:43:03Z

This flag turns off several other warnings that would be useful. Most notably -warn_unused_result is disabled. All of the following warnings are currently disabled: UnusedValue |-UnusedComparison |-warn_unused_comparison |-UnusedResult |-warn_unused_result |-UnevaluatedExpression |-PotentiallyEvaluatedExpression |-warn_side_effects_typeid |-warn_side_effects_unevaluated_context |-warn_unused_expr |-warn_unused_voidptr |-warn_unused_container_subscript_expr |-warn_unused_call With this flag removed there are ~10 warnings. Patches have been submitted for each of these warnings. Reported-by: Nick Desaulniers Cc: clang-built-linux@googlegroups.com Link: https://github.com/ClangBuiltLinux/linux/issues/520 Signed-off-by: Nathan Huckleberry Reviewed-by: Nick Desaulniers Signed-off-by: Masahiro Yamada

kbuild: Enable -Wuninitialized

2019-06-23T18:43:03Z

This helps fine very dodgy behavior through both -Wuninitialized (warning that a variable is always uninitialized) and -Wsometimes-uninitialized (warning that a variable is sometimes uninitialized, like GCC's -Wmaybe-uninitialized). These warnings catch things that GCC doesn't such as: https://lore.kernel.org/lkml/86649ee4-9794-77a3-502c-f4cd10019c36@lca.pw/ We very much want to catch these so turn this warning on so that CI is aware of it. Link: https://github.com/ClangBuiltLinux/linux/issues/381 Signed-off-by: Nathan Chancellor Reviewed-by: Nick Desaulniers Signed-off-by: Masahiro Yamada

kbuild: Remove -Waggregate-return from scripts/Makefile.extrawarn

2019-06-09T06:07:52Z

It makes little sense to pass -Waggregate-return these days since large part of the linux kernel rely on returning struct(s). For instance: ../include/linux/timekeeping.h: In function 'show_uptime': ../include/linux/ktime.h:91:34: error: function call has aggregate value [-Werror=aggregate-return] #define ktime_to_timespec64(kt) ns_to_timespec64((kt)) ^~~~~~~~~~~~~~~~~~~~~~ ../include/linux/timekeeping.h:166:8: note: in expansion of macro 'ktime_to_timespec64' *ts = ktime_to_timespec64(ktime_get_coarse_boottime()); Remove this warning from W=2 completely. Signed-off-by: Mathieu Malaterre Signed-off-by: Masahiro Yamada

kbuild: add all Clang-specific flags unconditionally

2019-05-18T02:49:53Z

We do not support old Clang versions. Upgrade your clang version if any of these flags is unsupported. Let's add all flags inside ifdef CONFIG_CC_IS_CLANG unconditionally. Signed-off-by: Masahiro Yamada Reviewed-by: Sedat Dilek Reviewed-by: Nathan Chancellor Tested-by: Nick Desaulniers

kbuild: add some extra warning flags unconditionally

2019-05-18T02:49:53Z

These flags are documented in the GCC 4.6 manual, and recognized by Clang as well. Let's rip off the cc-option / cc-disable-warning switches. Signed-off-by: Masahiro Yamada Reviewed-by: Nathan Chancellor Tested-by: Nick Desaulniers

Merge tag 'kbuild-v4.20-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

2018-11-03T17:47:33Z

Pull Kbuild updates from Masahiro Yamada: - clean-up leftovers in Kconfig files - remove stale oldnoconfig and silentoldconfig targets - remove unneeded cc-fullversion and cc-name variables - improve merge_config script to allow overriding option prefix * tag 'kbuild-v4.20-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: kbuild: remove cc-name variable kbuild: replace cc-name test with CONFIG_CC_IS_CLANG merge_config.sh: Allow to define config prefix kbuild: remove unused cc-fullversion variable kconfig: remove silentoldconfig target kconfig: remove oldnoconfig target powerpc: PCI_MSI needs PCI powerpc: remove CONFIG_MCA leftovers powerpc: remove CONFIG_PCI_QSPAN scsi: aha152x: rename the PCMCIA define