netdev - Re: [PATCH bpf] bpf: Use option "help" in the llvm-objcopy test

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Message-ID: <537c2d77-a10d-e108-e6a3-75c5c7a4b954@fb.com>
Date:   Tue, 24 Jul 2018 17:30:23 -0700
From:   Yonghong Song <yhs@...com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>, <netdev@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...com>, <kernel-team@...com>
Subject: Re: [PATCH bpf] bpf: Use option "help" in the llvm-objcopy test



On 7/20/18 1:37 AM, Daniel Borkmann wrote:
> On 07/20/2018 07:34 AM, Martin KaFai Lau wrote:
>> I noticed the "--version" option of the llvm-objcopy command has recently
>> disappeared from the master llvm branch.  It is currently used as a BTF
>> support test in tools/testing/selftests/bpf/Makefile.
>>
>> This patch replaces it with "--help" which should be
>> less error prone in the future.
>>
>> Fixes: c0fa1b6c3efc ("bpf: btf: Add BTF tests")
>> Signed-off-by: Martin KaFai Lau <kafai@...com>
> 
> Looks good, ran into the same recently as well from llvm git. Wondering whether
> the "--version" removal there was by accident or on purpose. In any case, applied

The option "--version" seems removed by accident.
On 6.0.0, the option handling is done by llvm.
      static cl::opt<std::string>
              OutputFormat("O", cl::desc("Set output format to one of the
                           following:"
                           "\n\tbinary"));
      cl::ParseCommandLineOptions(argc, argv, "llvm objcopy utility\n");
That is, the options are defined through llvm option handling system and
option "--version" is handled by llvm automatically.

In 7.0.0, llvm-objcopy tries to handle the options itself. 
Unfortunately, it did not define "version" option in its option file, so
"llvm-objcopy --version" won't work any more.

I will raise a bug or fix the issue properly.

> to bpf tree, thanks! If we make another change to the Makefile in near future,
> we should also make a comment there that the llvm-objcopy is used by pahole -J
> internally to make it a bit more clear in case someone is wondering why it's not
> used in the Makefile itself.
> 
> Thanks,
> Daniel
>