From: Yonghong Song <yhs@fb.com>
To: Nick Desaulniers <ndesaulniers@google.com>,
Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf <bpf@vger.kernel.org>, Andrii Nakryiko <andrii@kernel.org>,
Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
Kernel Team <kernel-team@fb.com>,
Sedat Dilek <sedat.dilek@gmail.com>
Subject: Re: [PATCH bpf-next v3 4/5] selftests/bpf: silence clang compilation warnings
Date: Tue, 13 Apr 2021 15:37:40 -0700 [thread overview]
Message-ID: <d1c28757-3fd9-4395-53c1-deb3161e89d2@fb.com> (raw)
In-Reply-To: <CAKwvOdmgJBV5yv5robxvmpdYhkw1epY6FNYYwiszqZ0zyE0UAw@mail.gmail.com>
On 4/13/21 3:17 PM, Nick Desaulniers wrote:
> On Tue, Apr 13, 2021 at 3:08 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
>>
>> On Tue, Apr 13, 2021 at 8:34 AM Yonghong Song <yhs@fb.com> wrote:
>>>
>>> With clang compiler:
>>> make -j60 LLVM=1 LLVM_IAS=1 <=== compile kernel
>>> make -j60 -C tools/testing/selftests/bpf LLVM=1 LLVM_IAS=1
>>> Some linker flags are not used/effective for some binaries and
>>> we have warnings like:
>>> warning: -lelf: 'linker' input unused [-Wunused-command-line-argument]
>>>
>>> We also have warnings like:
>>> .../selftests/bpf/prog_tests/ns_current_pid_tgid.c:74:57: note: treat the string as an argument to avoid this
>>> if (CHECK(waitpid(cpid, &wstatus, 0) == -1, "waitpid", strerror(errno)))
>>> ^
>>> "%s",
>>> .../selftests/bpf/test_progs.h:129:35: note: expanded from macro 'CHECK'
>>> _CHECK(condition, tag, duration, format)
>>> ^
>>> .../selftests/bpf/test_progs.h:108:21: note: expanded from macro '_CHECK'
>>> fprintf(stdout, ##format); \
>>> ^
>>> The first warning can be silenced with clang option -Wno-unused-command-line-argument.
>>> For the second warning, source codes are modified as suggested by the compiler
>>> to silence the warning. Since gcc does not support the option
>>> -Wno-unused-command-line-argument and the warning only happens with clang
>>> compiler, the option -Wno-unused-command-line-argument is enabled only when
>>> clang compiler is used.
>>>
>>> Signed-off-by: Yonghong Song <yhs@fb.com>
>>> ---
>>
>> LGTM, please see the question below.
>>
>> Acked-by: Andrii Nakryiko <andrii@kernel.org>
>>
>>> tools/testing/selftests/bpf/Makefile | 5 +++++
>>> tools/testing/selftests/bpf/prog_tests/fexit_sleep.c | 4 ++--
>>> tools/testing/selftests/bpf/prog_tests/ns_current_pid_tgid.c | 4 ++--
>>> 3 files changed, 9 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
>>> index dcc2dc1f2a86..c45ae13b88a0 100644
>>> --- a/tools/testing/selftests/bpf/Makefile
>>> +++ b/tools/testing/selftests/bpf/Makefile
>>> @@ -28,6 +28,11 @@ CFLAGS += -g -Og -rdynamic -Wall $(GENFLAGS) $(SAN_CFLAGS) \
>>> -Dbpf_load_program=bpf_test_load_program
>>> LDLIBS += -lcap -lelf -lz -lrt -lpthread
>>>
>>> +# Silence some warnings when compiled with clang
>>> +ifneq ($(LLVM),)
>>
>> This won't handle the case where someone does `make CC=clang`, right?
>> Do we care at all?
>
> Right; it would be better to check CC=clang and have LLVM=1 enable
> CC=clang from a higher level Makefile (since tools/build/Makefile
> seems to override the top level $CC). See the top level Makefile
> L448-456. Then it should work for CC=clang or LLVM=1.
I would consider LLVM=1 is recommended and should be supported
first. Support for CC=clang CXX=clang++ etc. can be done later
if people find cases where LLVM=1 does not fit their need.
>
>>
>>
>>> +CFLAGS += -Wno-unused-command-line-argument
>>> +endif
>>> +
>>
>> [...]
>
>
>
next prev parent reply other threads:[~2021-04-13 22:37 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 15:34 [PATCH bpf-next v3 0/5] bpf: tools: support build selftests/bpf with clang Yonghong Song
2021-04-13 15:34 ` [PATCH bpf-next v3 1/5] selftests: set CC to clang in lib.mk if LLVM is set Yonghong Song
2021-04-13 22:04 ` Andrii Nakryiko
2021-04-13 22:13 ` Nick Desaulniers
2021-04-13 22:27 ` Yonghong Song
2021-04-13 22:34 ` Nick Desaulniers
2021-04-13 23:22 ` Andrii Nakryiko
2021-04-13 15:34 ` [PATCH bpf-next v3 2/5] tools: allow proper CC/CXX/... override with LLVM=1 in Makefile.include Yonghong Song
2021-04-13 15:34 ` [PATCH bpf-next v3 3/5] selftests/bpf: fix test_cpp compilation failure with clang Yonghong Song
2021-04-13 22:05 ` Andrii Nakryiko
2021-04-13 15:34 ` [PATCH bpf-next v3 4/5] selftests/bpf: silence clang compilation warnings Yonghong Song
2021-04-13 22:07 ` Andrii Nakryiko
2021-04-13 22:17 ` Nick Desaulniers
2021-04-13 22:37 ` Yonghong Song [this message]
2021-04-13 15:34 ` [PATCH bpf-next v3 5/5] bpftool: fix a clang compilation warning Yonghong Song
2021-04-13 19:36 ` [PATCH bpf-next v3 0/5] bpf: tools: support build selftests/bpf with clang Martin KaFai Lau
2021-04-16 0:21 ` Alexei Starovoitov
2021-04-16 3:59 ` Yonghong Song
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