netdev - Re: [PATCH bpf-next 1/7] libbpf: disable -Wswitch-enum compiler warning

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Message-ID: <d69666c9-9c63-386f-130c-e30aba92e7c1@fb.com>
Date:   Tue, 18 Aug 2020 22:44:26 -0700
From:   Yonghong Song <yhs@...com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
CC:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next 1/7] libbpf: disable -Wswitch-enum compiler
 warning



On 8/18/20 6:39 PM, Andrii Nakryiko wrote:
> On Tue, Aug 18, 2020 at 6:23 PM Yonghong Song <yhs@...com> wrote:
>>
>>
>>
>> On 8/18/20 2:33 PM, Andrii Nakryiko wrote:
>>> That compilation warning is more annoying, than helpful.
>>
>> Curious which compiler and which version caused this issue?
>> I did not hit with gcc 8.2 or latest clang in my environment.
>>
> 
> Strange, I just tried on bpf-next, removed -Wno-switch-enum and got
> tons of errors:
> 
> libbpf.c: In function ‘bpf_object__sanitize_prog’:
> libbpf.c:5560:3: error: enumeration value ‘BPF_FUNC_unspec’ not
> handled in switch [-Werror=switch-enum]
>     switch (func_id) {
>     ^~~~~~
> libbpf.c:5560:3: error: enumeration value ‘BPF_FUNC_map_lookup_elem’
> not handled in switch [-Werror=switch-enum]
> libbpf.c:5560:3: error: enumeration value ‘BPF_FUNC_map_update_elem’
> not handled in switch [-Werror=switch-enum]
> ... and many more ...

Okay I can reproduce now with latest bpf-next but not bpf.
Now I understand why you introduced this additional option.
The issue is introduced by the above code in Patch #4. To compile
patch #4, you need -Wno-switch-enum.

> 
> My compiler:
> 
> $ cc --version
> cc (GCC) 8.2.1 20180801 (Red Hat 8.2.1-2)
> 
> 
>>>
>>> Signed-off-by: Andrii Nakryiko <andriin@...com>
>>> ---
>>>    tools/lib/bpf/Makefile | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
>>> index bf8ed134cb8a..95c946e94ca5 100644
>>> --- a/tools/lib/bpf/Makefile
>>> +++ b/tools/lib/bpf/Makefile
>>> @@ -107,7 +107,7 @@ ifeq ($(feature-reallocarray), 0)
>>>    endif
>>>
>>>    # Append required CFLAGS
>>> -override CFLAGS += $(EXTRA_WARNINGS)
>>> +override CFLAGS += $(EXTRA_WARNINGS) -Wno-switch-enum
>>>    override CFLAGS += -Werror -Wall
>>>    override CFLAGS += -fPIC
>>>    override CFLAGS += $(INCLUDES)
>>>