| Message ID | 20220927153125.811911-1-zengheng4@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [-next] Makefile: add implicit enum-conversion check for compile build | expand |
On Tue, Sep 27, 2022 at 8:15 AM Zeng Heng <zengheng4@huawei.com> wrote: > > Provide implicit enum-conversion warning option > in general build. When it set enabled, it can > detect implicit enum type conversion and find > potential conversion errors like below > (use "allmodconfig"): > > drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn20/display_mode_vba_20.c:3904:46: > error: implicit conversion from ‘enum <anonymous>’ to ‘enum odm_combine_mode’ [-Werror=enum-conversion] > 3904 | locals->ODMCombineEnablePerState[i][k] = true; > | ^ > > The '-Wenum-conversion' could be regarded as > effective check on compile runtime and > call attention on potential mistakes. > > Anothor practical example could be referred to: > https://lore.kernel.org/all/CADnq5_OE0yZvEYGu82QJHL9wvVcTFZrmeTgX7URgh7FVA=jqYg@mail.gmail.com > > "-Wenum-conversion" was firstly introduced from > GNU gcc-10. What about clang? ;) > > Although "-Wenum-conversion" could be enabled > by "-Wextra" when compiling with 'W=1' option, > there are many warnings generated by '-Wextra' > that cause too much noise in a build. With clang, I believe that -Wenum-conversion is part of -Wall or -Wextra; so enabling this explicitly is only necessary for GCC. I wonder why it's not part of -Wall or -Wextra for GCC? Perhaps worth a bug report/feature request? > > Seeing the details from the following link: > https://gcc.gnu.org/onlinedocs/gcc-11.3.0/gcc/Warning-Options.html > > Because there are still some concerned warnings > exist, the patch marks the option disabled in default > for avoiding compile failed like using "allmodconfig". > > Signed-off-by: Zeng Heng <zengheng4@huawei.com> > --- > Makefile | 5 +++++ > lib/Kconfig.debug | 7 +++++++ > 2 files changed, 12 insertions(+) > > diff --git a/Makefile b/Makefile > index ebd48fc956a3..1790a3624358 100644 > --- a/Makefile > +++ b/Makefile > @@ -880,6 +880,11 @@ endif > KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) > KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) > > +# check implicit enum conversion > +ifdef CONFIG_ENUM_CONVERSION > +KBUILD_CFLAGS += -Wenum-conversion > +endif Having a kconfig for this is overkill. cc-option with a comment about the compiler default versions is the way to go. > + > # These result in bogus false positives > KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer) > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 4f2b81229a2f..a64e06a747d8 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -417,6 +417,13 @@ config FRAME_WARN > Setting this too low will cause a lot of warnings. > Setting it to 0 disables the warning. > > +config ENUM_CONVERSION > + bool "Warn for implicit enum conversion" > + depends on GCC_VERSION >= 100300 > + default n > + help > + Tell gcc to warn at build time for implicit enum conversion. > + > config STRIP_ASM_SYMS > bool "Strip assembler-generated symbols during link" > default n > -- > 2.25.1 >
On Tue, Sep 27, 2022 at 09:45:17AM -0700, Nick Desaulniers wrote: > On Tue, Sep 27, 2022 at 8:15 AM Zeng Heng <zengheng4@huawei.com> wrote: > > > > Provide implicit enum-conversion warning option > > in general build. When it set enabled, it can > > detect implicit enum type conversion and find > > potential conversion errors like below > > (use "allmodconfig"): > > > > drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn20/display_mode_vba_20.c:3904:46: > > error: implicit conversion from ‘enum <anonymous>’ to ‘enum odm_combine_mode’ [-Werror=enum-conversion] > > 3904 | locals->ODMCombineEnablePerState[i][k] = true; > > | ^ > > > > The '-Wenum-conversion' could be regarded as > > effective check on compile runtime and > > call attention on potential mistakes. > > > > Anothor practical example could be referred to: > > https://lore.kernel.org/all/CADnq5_OE0yZvEYGu82QJHL9wvVcTFZrmeTgX7URgh7FVA=jqYg@mail.gmail.com > > > > "-Wenum-conversion" was firstly introduced from > > GNU gcc-10. > > What about clang? ;) > > > > > Although "-Wenum-conversion" could be enabled > > by "-Wextra" when compiling with 'W=1' option, > > there are many warnings generated by '-Wextra' > > that cause too much noise in a build. > > With clang, I believe that -Wenum-conversion is part of -Wall or > -Wextra; so enabling this explicitly is only necessary for GCC. I > wonder why it's not part of -Wall or -Wextra for GCC? Perhaps worth a > bug report/feature request? With clang, -Wenum-conversion is just default enabled, not even behind -Wall: $ cat test.c enum enum1 { A = 1 }; enum enum2 { B = 2 }; enum enum1 foo(enum enum2 bar) { return bar; } $ clang -fsyntax-only test.c test.c:11:9: warning: implicit conversion from enumeration type 'enum enum2' to different enumeration type 'enum enum1' [-Wenum-conversion] return bar; ~~~~~~ ^~~ 1 warning generated. On the other hand, GCC does have it under -Wextra: $ gcc -fsyntax-only test.c $ gcc -Wextra -fsyntax-only test.c test.c: In function ‘foo’: test.c:6:16: warning: implicit conversion from ‘enum enum2’ to ‘enum enum1’ [-Wenum-conversion] 6 | return bar; | ^~~ But the kernel does not build with -Wextra aside from W=[123], hence this warning has to be explicitly requested for GCC. > > > > Seeing the details from the following link: > > https://gcc.gnu.org/onlinedocs/gcc-11.3.0/gcc/Warning-Options.html > > > > Because there are still some concerned warnings > > exist, the patch marks the option disabled in default > > for avoiding compile failed like using "allmodconfig". But there is no dependency to avoid this getting enabled by allmodconfig (such as 'depends on !COMPILE_TEST') so I don't see the point in the current form; 'default n' does nothing to prevent it. Regardless, I agree with Nick's sentiment below. > > Signed-off-by: Zeng Heng <zengheng4@huawei.com> > > --- > > Makefile | 5 +++++ > > lib/Kconfig.debug | 7 +++++++ > > 2 files changed, 12 insertions(+) > > > > diff --git a/Makefile b/Makefile > > index ebd48fc956a3..1790a3624358 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -880,6 +880,11 @@ endif > > KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) > > KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) > > > > +# check implicit enum conversion > > +ifdef CONFIG_ENUM_CONVERSION > > +KBUILD_CFLAGS += -Wenum-conversion > > +endif > > Having a kconfig for this is overkill. cc-option with a comment about > the compiler default versions is the way to go. Agreed. If there is some reason -Wenum-conversion cannot be enabled for GCC right now (such as existing warnings, which the commit message appears to alude to), they should be cleaned up first then -Wenum-conversion should just be unconditionally enabled for all compilers that support it via cc-option, not half enabled via Kconfig so that maybe people will clean up the warnings. That is not how enabling warnings works: https://lore.kernel.org/CAHk-=wg-mH-_GYpkhz_psjBWG6ZcjKnPo83fg7YMj_by+-LRTQ@mail.gmail.com/ > > + > > # These result in bogus false positives > > KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer) > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > index 4f2b81229a2f..a64e06a747d8 100644 > > --- a/lib/Kconfig.debug > > +++ b/lib/Kconfig.debug > > @@ -417,6 +417,13 @@ config FRAME_WARN > > Setting this too low will cause a lot of warnings. > > Setting it to 0 disables the warning. > > > > +config ENUM_CONVERSION > > + bool "Warn for implicit enum conversion" > > + depends on GCC_VERSION >= 100300 > > + default n > > + help > > + Tell gcc to warn at build time for implicit enum conversion. > > + > > config STRIP_ASM_SYMS > > bool "Strip assembler-generated symbols during link" > > default n > > -- > > 2.25.1 > > > > > -- > Thanks, > ~Nick Desaulniers >
On 2022/9/28 1:02, Nathan Chancellor wrote: > On Tue, Sep 27, 2022 at 09:45:17AM -0700, Nick Desaulniers wrote: >> On Tue, Sep 27, 2022 at 8:15 AM Zeng Heng <zengheng4@huawei.com> wrote: >>> Provide implicit enum-conversion warning option >>> in general build. When it set enabled, it can >>> detect implicit enum type conversion and find >>> potential conversion errors like below >>> (use "allmodconfig"): >>> >>> drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn20/display_mode_vba_20.c:3904:46: >>> error: implicit conversion from ‘enum <anonymous>’ to ‘enum odm_combine_mode’ [-Werror=enum-conversion] >>> 3904 | locals->ODMCombineEnablePerState[i][k] = true; >>> | ^ >>> >>> The '-Wenum-conversion' could be regarded as >>> effective check on compile runtime and >>> call attention on potential mistakes. >>> >>> Anothor practical example could be referred to: >>> https://lore.kernel.org/all/CADnq5_OE0yZvEYGu82QJHL9wvVcTFZrmeTgX7URgh7FVA=jqYg@mail.gmail.com >>> >>> "-Wenum-conversion" was firstly introduced from >>> GNU gcc-10. >> What about clang? ;) >> >>> Although "-Wenum-conversion" could be enabled >>> by "-Wextra" when compiling with 'W=1' option, >>> there are many warnings generated by '-Wextra' >>> that cause too much noise in a build. >> With clang, I believe that -Wenum-conversion is part of -Wall or >> -Wextra; so enabling this explicitly is only necessary for GCC. I >> wonder why it's not part of -Wall or -Wextra for GCC? Perhaps worth a >> bug report/feature request? > With clang, -Wenum-conversion is just default enabled, not even behind > -Wall: > > $ cat test.c > enum enum1 { A = 1 }; > enum enum2 { B = 2 }; > > enum enum1 foo(enum enum2 bar) > { > return bar; > } > > $ clang -fsyntax-only test.c > test.c:11:9: warning: implicit conversion from enumeration type 'enum enum2' to different enumeration type 'enum enum1' [-Wenum-conversion] > return bar; > ~~~~~~ ^~~ > 1 warning generated. > > On the other hand, GCC does have it under -Wextra: > > $ gcc -fsyntax-only test.c > > $ gcc -Wextra -fsyntax-only test.c > test.c: In function ‘foo’: > test.c:6:16: warning: implicit conversion from ‘enum enum2’ to ‘enum enum1’ [-Wenum-conversion] > 6 | return bar; > | ^~~ > > But the kernel does not build with -Wextra aside from W=[123], hence > this warning has to be explicitly requested for GCC. Thanks to your replenish about clang. >>> Seeing the details from the following link: >>> https://gcc.gnu.org/onlinedocs/gcc-11.3.0/gcc/Warning-Options.html >>> >>> Because there are still some concerned warnings >>> exist, the patch marks the option disabled in default >>> for avoiding compile failed like using "allmodconfig". > But there is no dependency to avoid this getting enabled by allmodconfig > (such as 'depends on !COMPILE_TEST') so I don't see the point in the > current form; 'default n' does nothing to prevent it. Regardless, I > agree with Nick's sentiment below. > >>> Signed-off-by: Zeng Heng <zengheng4@huawei.com> >>> --- >>> Makefile | 5 +++++ >>> lib/Kconfig.debug | 7 +++++++ >>> 2 files changed, 12 insertions(+) >>> >>> diff --git a/Makefile b/Makefile >>> index ebd48fc956a3..1790a3624358 100644 >>> --- a/Makefile >>> +++ b/Makefile >>> @@ -880,6 +880,11 @@ endif >>> KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) >>> KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) >>> >>> +# check implicit enum conversion >>> +ifdef CONFIG_ENUM_CONVERSION >>> +KBUILD_CFLAGS += -Wenum-conversion >>> +endif >> Having a kconfig for this is overkill. cc-option with a comment about >> the compiler default versions is the way to go. Got it. > Agreed. If there is some reason -Wenum-conversion cannot be enabled for > GCC right now (such as existing warnings, which the commit message > appears to alude to), they should be cleaned up first then > -Wenum-conversion should just be unconditionally enabled for all > compilers that support it via cc-option, not half enabled via Kconfig so > that maybe people will clean up the warnings. That is not how enabling > warnings works: > > https://lore.kernel.org/CAHk-=wg-mH-_GYpkhz_psjBWG6ZcjKnPo83fg7YMj_by+-LRTQ@mail.gmail.com/ Have sent the patches to fix the involving warnings. If all the concerned warnings were repaired, I would send the v2 again. Thanks all. >>> + >>> # These result in bogus false positives >>> KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer) >>> >>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug >>> index 4f2b81229a2f..a64e06a747d8 100644 >>> --- a/lib/Kconfig.debug >>> +++ b/lib/Kconfig.debug >>> @@ -417,6 +417,13 @@ config FRAME_WARN >>> Setting this too low will cause a lot of warnings. >>> Setting it to 0 disables the warning. >>> >>> +config ENUM_CONVERSION >>> + bool "Warn for implicit enum conversion" >>> + depends on GCC_VERSION >= 100300 >>> + default n >>> + help >>> + Tell gcc to warn at build time for implicit enum conversion. >>> + >>> config STRIP_ASM_SYMS >>> bool "Strip assembler-generated symbols during link" >>> default n >>> -- >>> 2.25.1 >>> >> >> -- >> Thanks, >> ~Nick Desaulniers >>
diff --git a/Makefile b/Makefile index ebd48fc956a3..1790a3624358 100644 --- a/Makefile +++ b/Makefile @@ -880,6 +880,11 @@ endif KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) +# check implicit enum conversion +ifdef CONFIG_ENUM_CONVERSION +KBUILD_CFLAGS += -Wenum-conversion +endif + # These result in bogus false positives KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 4f2b81229a2f..a64e06a747d8 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -417,6 +417,13 @@ config FRAME_WARN Setting this too low will cause a lot of warnings. Setting it to 0 disables the warning. +config ENUM_CONVERSION + bool "Warn for implicit enum conversion" + depends on GCC_VERSION >= 100300 + default n + help + Tell gcc to warn at build time for implicit enum conversion. + config STRIP_ASM_SYMS bool "Strip assembler-generated symbols during link" default n
Provide implicit enum-conversion warning option in general build. When it set enabled, it can detect implicit enum type conversion and find potential conversion errors like below (use "allmodconfig"): drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn20/display_mode_vba_20.c:3904:46: error: implicit conversion from ‘enum <anonymous>’ to ‘enum odm_combine_mode’ [-Werror=enum-conversion] 3904 | locals->ODMCombineEnablePerState[i][k] = true; | ^ The '-Wenum-conversion' could be regarded as effective check on compile runtime and call attention on potential mistakes. Anothor practical example could be referred to: https://lore.kernel.org/all/CADnq5_OE0yZvEYGu82QJHL9wvVcTFZrmeTgX7URgh7FVA=jqYg@mail.gmail.com "-Wenum-conversion" was firstly introduced from GNU gcc-10. Although "-Wenum-conversion" could be enabled by "-Wextra" when compiling with 'W=1' option, there are many warnings generated by '-Wextra' that cause too much noise in a build. Seeing the details from the following link: https://gcc.gnu.org/onlinedocs/gcc-11.3.0/gcc/Warning-Options.html Because there are still some concerned warnings exist, the patch marks the option disabled in default for avoiding compile failed like using "allmodconfig". Signed-off-by: Zeng Heng <zengheng4@huawei.com> --- Makefile | 5 +++++ lib/Kconfig.debug | 7 +++++++ 2 files changed, 12 insertions(+)