| Message ID | 20240531183751.100541-3-jhubbard@nvidia.com |
|---|---|
| State | New |
| Headers | show |
| Series | selftests/lib.mk: LLVM=1, CC=clang, and warnings | expand |
On 5/31/24 11:37 AM, John Hubbard wrote: > gcc defaults to silence (off) for the following warnings, but clang > defaults to the opposite. The warnings are not useful for the kernel > itself, which is why they have remained disabled in gcc for the main > kernel build. And it is only due to including kernel data structures in > the selftests, that we get the warnings from clang. > > -Waddress-of-packed-member > -Wgnu-variable-sized-type-not-at-end Even if patch 1/1 here is not merged, I would still like to get this one reviewed and merged. It still solves the problem for LLVM=1 builds. thanks,
On Fri, May 31, 2024 at 11:37:51AM -0700, John Hubbard wrote: > gcc defaults to silence (off) for the following warnings, but clang > defaults to the opposite. The warnings are not useful for the kernel > itself, which is why they have remained disabled in gcc for the main > kernel build. And it is only due to including kernel data structures in > the selftests, that we get the warnings from clang. > > -Waddress-of-packed-member > -Wgnu-variable-sized-type-not-at-end > > In other words, the warnings are not unique to the selftests: there is > nothing that the selftests' code does that triggers these warnings, > other than the act of including the kernel's data structures. Therefore, > silence them for the clang builds as well. > > This eliminates warnings for the net/ and user_events/ kselftest > subsystems, in these files: > > ./net/af_unix/scm_rights.c > ./net/timestamping.c > ./net/ipsec.c > ./user_events/perf_test.c > > Cc: Nathan Chancellor <nathan@kernel.org> > Signed-off-by: John Hubbard <jhubbard@nvidia.com> This seems reasonable to me. Acked-by: Nathan Chancellor <nathan@kernel.org> > --- > tools/testing/selftests/lib.mk | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk > index 2902787b89b2..c179c02281e9 100644 > --- a/tools/testing/selftests/lib.mk > +++ b/tools/testing/selftests/lib.mk > @@ -50,6 +50,14 @@ else > CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > endif # CROSS_COMPILE > > +# gcc defaults to silence (off) for the following warnings, but clang defaults > +# to the opposite. The warnings are not useful for the kernel itself, which is > +# why they have remained disabled in gcc for the main kernel build. And it is > +# only due to including kernel data structures in the selftests, that we get the > +# warnings from clang. Therefore, disable the warnings for clang builds. > +CFLAGS += -Wno-address-of-packed-member > +CFLAGS += -Wno-gnu-variable-sized-type-not-at-end > + > CC := $(CLANG) $(CLANG_FLAGS) -fintegrated-as > else > CC := $(CROSS_COMPILE)gcc > -- > 2.45.1 > >
On 6/3/24 16:36, Nathan Chancellor wrote: > On Fri, May 31, 2024 at 11:37:51AM -0700, John Hubbard wrote: >> gcc defaults to silence (off) for the following warnings, but clang >> defaults to the opposite. The warnings are not useful for the kernel >> itself, which is why they have remained disabled in gcc for the main >> kernel build. And it is only due to including kernel data structures in >> the selftests, that we get the warnings from clang. >> >> -Waddress-of-packed-member >> -Wgnu-variable-sized-type-not-at-end >> >> In other words, the warnings are not unique to the selftests: there is >> nothing that the selftests' code does that triggers these warnings, >> other than the act of including the kernel's data structures. Therefore, >> silence them for the clang builds as well. >> >> This eliminates warnings for the net/ and user_events/ kselftest >> subsystems, in these files: >> >> ./net/af_unix/scm_rights.c >> ./net/timestamping.c >> ./net/ipsec.c >> ./user_events/perf_test.c >> >> Cc: Nathan Chancellor <nathan@kernel.org> >> Signed-off-by: John Hubbard <jhubbard@nvidia.com> > > This seems reasonable to me. > > Acked-by: Nathan Chancellor <nathan@kernel.org> > >> --- >> tools/testing/selftests/lib.mk | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk >> index 2902787b89b2..c179c02281e9 100644 >> --- a/tools/testing/selftests/lib.mk >> +++ b/tools/testing/selftests/lib.mk >> @@ -50,6 +50,14 @@ else >> CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) >> endif # CROSS_COMPILE >> >> +# gcc defaults to silence (off) for the following warnings, but clang defaults >> +# to the opposite. The warnings are not useful for the kernel itself, which is >> +# why they have remained disabled in gcc for the main kernel build. And it is >> +# only due to including kernel data structures in the selftests, that we get the >> +# warnings from clang. Therefore, disable the warnings for clang builds. >> +CFLAGS += -Wno-address-of-packed-member >> +CFLAGS += -Wno-gnu-variable-sized-type-not-at-end >> + Thank you for adding this comment block. >> CC := $(CLANG) $(CLANG_FLAGS) -fintegrated-as >> else >> CC := $(CROSS_COMPILE)gcc >> -- >> 2.45.1 >> >> > Thank you both. I will apply this for the next release. I want this change soaking in next for a bit. thanks, -- Shuah
diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk index 2902787b89b2..c179c02281e9 100644 --- a/tools/testing/selftests/lib.mk +++ b/tools/testing/selftests/lib.mk @@ -50,6 +50,14 @@ else CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) endif # CROSS_COMPILE +# gcc defaults to silence (off) for the following warnings, but clang defaults +# to the opposite. The warnings are not useful for the kernel itself, which is +# why they have remained disabled in gcc for the main kernel build. And it is +# only due to including kernel data structures in the selftests, that we get the +# warnings from clang. Therefore, disable the warnings for clang builds. +CFLAGS += -Wno-address-of-packed-member +CFLAGS += -Wno-gnu-variable-sized-type-not-at-end + CC := $(CLANG) $(CLANG_FLAGS) -fintegrated-as else CC := $(CROSS_COMPILE)gcc
gcc defaults to silence (off) for the following warnings, but clang defaults to the opposite. The warnings are not useful for the kernel itself, which is why they have remained disabled in gcc for the main kernel build. And it is only due to including kernel data structures in the selftests, that we get the warnings from clang. -Waddress-of-packed-member -Wgnu-variable-sized-type-not-at-end In other words, the warnings are not unique to the selftests: there is nothing that the selftests' code does that triggers these warnings, other than the act of including the kernel's data structures. Therefore, silence them for the clang builds as well. This eliminates warnings for the net/ and user_events/ kselftest subsystems, in these files: ./net/af_unix/scm_rights.c ./net/timestamping.c ./net/ipsec.c ./user_events/perf_test.c Cc: Nathan Chancellor <nathan@kernel.org> Signed-off-by: John Hubbard <jhubbard@nvidia.com> --- tools/testing/selftests/lib.mk | 8 ++++++++ 1 file changed, 8 insertions(+)