On Wed, Oct 12, 2022 at 6:10 AM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > On Mon, Oct 10, 2022 at 8:24 PM Zeng Heng <zengheng4@xxxxxxxxxx> wrote: > > > > Enable implicit enum-conversion warning option in kernel gcc build. > > When it set enabled, it can detect implicit enum type conversion > > and locate 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 in > > compile runtime and call attention on potential mistakes, which is > > firstly introduced from GNU gcc-10. > > > > Although "-Wenum-conversion" could be enabled by "-Wextra" > > when compiling with 'W=[123]' option, there are many warnings > > generated by '-Wextra' that cause too much noise in the build. > > > > Seeing the more details from the following link: > > https://gcc.gnu.org/onlinedocs/gcc-11.3.0/gcc/Warning-Options.html > > > > Therefore, "-Wenum-conversion" warning option needs to be > > explicitly requested for GCC when compilation process is only > > companied with '-Wall'. > > > > With clang, -Wenum-conversion is just default enabled, not even > > behind -Wall. > > Probably didn't need the examples below since you already provide an > example above, too, but it doesn't matter. Thanks for the patch. > > Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > > > > Provide a couple examples for reference as below: > > > > $ cat test.c > > enum enum1 { A = 1 }; > > enum enum2 { B = 2 }; > > > > enum enum1 foo(enum enum2 bar) > > { > > return bar; > > } > > > > $ gcc -Wall -fsyntax-only test.c > > > > $ gcc -Wall -Wenum-conversion -fsyntax-only test.c > > test.c: In function ‘foo’: > > test.c:6:9: warning: implicit conversion from ‘enum enum2’ to ‘enum enum1’ [-Wenum-conversion] > > 6 | return bar; > > | ^~~ > > > > $ gcc -Wextra -fsyntax-only test.c > > test.c: In function ‘foo’: > > test.c:6:9: warning: implicit conversion from ‘enum enum2’ to ‘enum enum1’ [-Wenum-conversion] > > 6 | return bar; > > | ^~~ > > > > $ clang -fsyntax-only test.c > > test.c:6:9: warning: implicit conversion from enumeration type 'enum enum2' to different enumeration type 'enum enum1' [-Wenum-conversion] > > return bar; > > ~~~~~~ ^~~ > > 1 warning generated. > > > > Signed-off-by: Zeng Heng <zengheng4@xxxxxxxxxx> > > Suggested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > Suggested-by: Nathan Chancellor <nathan@xxxxxxxxxx> > > --- > > Makefile | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/Makefile b/Makefile > > index 8f6ed52fa08f..72103d22df23 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -880,6 +880,10 @@ endif > > KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) > > KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) > > > > +# implicit enum conversion checking is supported since from gcc-10 > > +# this warning option has to be explicitly requested for GCC > > +KBUILD_CFLAGS += $(call cc-option, -Wenum-conversion) > > + > > # These result in bogus false positives > > KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer) > > > > -- > > 2.25.1 > > > > > -- > Thanks, > ~Nick Desaulniers Applied to linux-kbuild. Thanks. -- Best Regards Masahiro Yamada
