netdev - Re: [PATCH bpf-next v1 7/8] selftests/bpf: Fix using stdout, stderr as struct field names

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Message-ID: <CAEf4BzauQQgWfc8eKsWF+Fr-j--oY6tJAM2+ZfAPHP7JJqZ6Zg@mail.gmail.com>
Date: Thu, 25 Jul 2024 13:27:03 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Tony Ambardar <tony.ambardar@...il.com>
Cc: bpf@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	netdev@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>, 
	Björn Töpel <bjorn@...nel.org>, 
	Magnus Karlsson <magnus.karlsson@...el.com>, 
	Maciej Fijalkowski <maciej.fijalkowski@...el.com>, Jonathan Lemon <jonathan.lemon@...il.com>, 
	"David S. Miller" <davem@...emloft.net>, Yan Zhai <yan@...udflare.com>
Subject: Re: [PATCH bpf-next v1 7/8] selftests/bpf: Fix using stdout, stderr
 as struct field names

On Thu, Jul 25, 2024 at 3:39 AM Tony Ambardar <tony.ambardar@...il.com> wrote:
>
> From: Tony Ambardar <tony.ambardar@...il.com>
>
> Typically stdin, stdout, stderr are treated as reserved identifiers under
> ISO/ANSI C, and a libc implementation is free to define these as macros.

Ok, wow that. Do you have a pointer to where in the standard it is
said that stdin/stdout/stderr is some sort of reserved identifier that
can't be used as a field name?


I really don't like these underscored field names. If we have to
rename, I'd prefer something like env.saved_stdout instead of
env._stdout. But I'd prefer even more if musl wasn't doing this macro
definition, of course...

> This is the case in musl libc and results in compile errors when these
> names are reused as struct fields, as with 'struct test_env' and related
> usage in test_progs.[ch] and reg_bounds.c.
>
> Rename the fields to _stdout and _stderr to avoid many errors seen building
> against musl, e.g.:
>
>   In file included from test_progs.h:6,
>                    from test_progs.c:5:
>   test_progs.c: In function 'print_test_result':
>   test_progs.c:237:21: error: expected identifier before '(' token
>     237 |         fprintf(env.stdout, "#%-*d %s:", TEST_NUM_WIDTH, test->test_num, test->test_name);
>         |                     ^~~~~~
>   test_progs.c:237:9: error: too few arguments to function 'fprintf'
>     237 |         fprintf(env.stdout, "#%-*d %s:", TEST_NUM_WIDTH, test->test_num, test->test_name);
>         |         ^~~~~~~
>
> Signed-off-by: Tony Ambardar <tony.ambardar@...il.com>
> ---
>  .../selftests/bpf/prog_tests/reg_bounds.c     |  2 +-
>  tools/testing/selftests/bpf/test_progs.c      | 66 +++++++++----------
>  tools/testing/selftests/bpf/test_progs.h      |  8 +--
>  3 files changed, 38 insertions(+), 38 deletions(-)
>

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