On 04/08/2016 08:54 PM, Martin Sebor wrote:
>> The name for new option "-Wduplicate-decl-specifier" and wording was
>> chosen to match the same option in Clang.
> 
> My version of Clang also warns in C++ mode but if I'm reading
> the patch right, GCC would warn only C mode.  I would find it
> surprising if GCC provided the same option as Clang but didn't
> make it available in the same languages.  Do you have some
> reason for leaving it out that I'm not thinking of?
It is an error in C++ mode. Do we want to change this behavior?

> 
> Also, in C11 mode, Clang issues the warning for duplicated
> _Atomic qualifiers but it doesn't look like GCC would with
> the patch.  Here again, unless there's some reason not to,
> I would expect GCC to issue the same warning as Clang for
> the same code.
> 
Fixed.

-- 
Regards,
    Mikhail Maltsev

gcc/c/ChangeLog:

2016-04-08  Mikhail Maltsev  <maltsevm@gmail.com>

        PR c/43651
        * c-decl.c (declspecs_add_qual): Warn when -Wduplicate-decl-specifier
        is enabled.
        * c-errors.c (pedwarn_c90): Return true if warned.
        * c-tree.h (pedwarn_c90): Change return type to bool.
        (enum c_declspec_word): Add new enumerator cdw_atomic.

gcc/ChangeLog:

2016-04-08  Mikhail Maltsev  <maltsevm@gmail.com>

        PR c/43651
        * doc/invoke.texi (Wduplicate-decl-specifier): Document new option.

gcc/testsuite/ChangeLog:

2016-04-08  Mikhail Maltsev  <maltsevm@gmail.com>

        PR c/43651
        * gcc.dg/Wduplicate-decl-specifier-c11.c: New test.
        * gcc.dg/Wduplicate-decl-specifier.c: Likewise.


gcc/c-family/ChangeLog:

2016-04-08  Mikhail Maltsev  <maltsevm@gmail.com>

        PR c/43651
        * c.opt (Wduplicate-decl-specifier): New option.