From: Gary Benson <gbenson@redhat.com>
To: Pedro Alves <palves@redhat.com>
Cc: Tom Tromey <tom@tromey.com>, gdb-patches@sourceware.org
Subject: Re: [OB PATCH] Build two gdb.cp testcases with -Wno-unused-comparison
Date: Tue, 16 Jun 2020 13:42:12 +0100 [thread overview]
Message-ID: <20200616124212.GB30305@blade.nx> (raw)
In-Reply-To: <68fd1b3e-10ae-8f1d-b96d-f35ce7ae3037@redhat.com>
Pedro Alves wrote:
> On 5/29/20 7:08 PM, Tom Tromey wrote:
> >>>>>> "Gary" == Gary Benson via Gdb-patches <gdb-patches@sourceware.org> writes:
> >
> > Gary> +if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
> > Gary> + {debug c++ additional_flags=-Wno-unused-comparison}] } {
> >
> > Won't this cause build (and therefore test) failures if the compiler
> > does not accept this option?
>
> I think that by design, while GCC errors out about unknown -Wfoo warnings,
> it ignores -Wno-foo, so that you can disable newer warnings without worrying
> about older compilers:
>
> $ gcc main.c -o main -g3 -O0 -Wfoo
> gcc: error: unrecognized command line option ‘-Wfoo’
> $ gcc main.c -o main -g3 -O0 -Wno-foo
Nice.
> However, Clang seems to output a warning in either case:
>
> $ clang main.c -o main -g3 -O0 -Wfoo
> warning: unknown warning option '-Wfoo' [-Wunknown-warning-option]
> 1 warning generated.
> $ clang main.c -o main -g3 -O0 -Wno-foo
> warning: unknown warning option '-Wno-foo' [-Wunknown-warning-option]
> 1 warning generated.
>
> (This was clang 5.0.2)
>
> So that new option can break tests with older Clangs that don't
> know about the option.
Ugh.
clang 9.0.1 behaves the same too:
$ clang -Werror -Wno-step-on-grass test.c
error: unknown warning option '-Wno-step-on-grass' [-Werror,-Wunknown-warning-option]
> I guess to prevent this sort of thing going forward, we could make
> gcc_compile always add -Wno-unknown-warning-option to the build
> flags. I don't know when was that option added to Clang, but maybe
> it's ancient enough.
Does this buy us much? Any test with a warning I disable for clang is
a test that didn't compile with clang anyway.
Cheers,
Gary
next prev parent reply other threads:[~2020-06-16 12:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-29 13:03 Gary Benson
2020-05-29 18:08 ` Tom Tromey
2020-05-29 18:31 ` Pedro Alves
2020-06-16 12:42 ` Gary Benson [this message]
2020-06-16 15:11 ` Pedro Alves
2020-06-17 17:29 ` Gary Benson
2020-06-17 19:53 ` [PATCH] W/ Clang, compile C/C++ testcases with -Wno-unknown-warning-option Pedro Alves
2020-06-18 16:18 ` Gary Benson
2020-06-24 22:26 ` Pedro Alves
2020-07-02 10:02 ` Gary Benson
2020-06-16 12:38 ` [OB PATCH] Build two gdb.cp testcases with -Wno-unused-comparison Gary Benson
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