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
