[Bug c++/84177] New: Attributes on C++17 nested namespaces

["akim.demaille at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84177

            Bug ID: 84177
           Summary: Attributes on C++17 nested namespaces
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: akim.demaille at gmail dot com
  Target Milestone: ---

One would expect this to work:

$ cat /tmp/foo.cc
namespace a::b __attribute__ ((visibility ("protected")) {}

$ g++-mp-7 -std=c++17 /tmp/foo.cc
/tmp/foo.cc:1:16: error: expected '{' before '__attribute__'
 namespace a::b __attribute__ ((visibility ("protected")) {}
                ^~~~~~~~~~~~~
/tmp/foo.cc:1:58: error: expected ')' before '{' token
 namespace a::b __attribute__ ((visibility ("protected")) {}
                                                          ^
/tmp/foo.cc:1:59: error: expected unqualified-id at end of input
 namespace a::b __attribute__ ((visibility ("protected")) {}
                                                           ^
/tmp/foo.cc:1:59: error: expected '}' at end of input


This is:

$ g++-mp-7 --version
g++-mp-7 (MacPorts gcc7 7.2.0_0) 7.2.0
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

FWIW, it's quite hard to navigate in the documentation to find
information about attributes for namespaces.  I have not found
clear evidence that this feature had been considered and eliminated,
or whether it's just an overlook.

Cheers!