Re: [PATCH 2/2] kbuild: clang: Disable the 'duplicate-decl-specifier' warning

From: Masahiro Yamada
Date: Wed Jun 21 2017 - 05:12:05 EST


2017-05-24 17:21 GMT+09:00 Arnd Bergmann <arnd@xxxxxxxx>:
> On Wed, May 24, 2017 at 2:04 AM, Matthias Kaehlcke <mka@xxxxxxxxxxxx> wrote:
>> El Wed, May 17, 2017 at 11:45:29AM -0700 Matthias Kaehlcke ha dit:
>>> El Wed, May 17, 2017 at 09:35:57AM +0200 Arnd Bergmann ha dit:
>>> > On Tue, May 16, 2017 at 11:41 PM, Doug Anderson <dianders@xxxxxxxxxxxx> wrote:
>> It seems the duplicate-decl-specifier warning targets specifically C89:
>> "The same type qualifier shall not appear more than once in the same
>> specifier list or qualifier list, either directly or via one or more
>> typedefs."
>> C89 (6.5.3)
>> gcc also raises a warning when '-pedantic' is specified and
>> -std=gnu89/c89 (or unspecified), but not with -std=gnu99/c99.
>> This bug might help to shed more light on this:
> I also notice that neither compiler differentiates between a)
> typedef const int cint;
> const cint i;
> and b)
> const int i;
> const typeof(a) j;
> I would have expected a warning for a) but not b), but both 'clang --std=gnu89'
> and 'gcc --pedantic --std=gnu89' warn about both of b as well, and don't warn
> for newer standards.
> Arnd

I think we agreed to apply 1/2.

How about 2/2?

I think we mostly discussed preferable behavior of -Wduplicate-decl-specifier,
but we did not come up with an idea to solve the problem for
already shipped clang versions.
(BTW, we have not defined the minimal supported version of clang yet.)

Best Regards
Masahiro Yamada