[Bug c++/86288] New: Recognize __gnu and/or __gnu__ as attribute-namespace

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86288

            Bug ID: 86288
           Summary: Recognize __gnu and/or __gnu__ as attribute-namespace
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

Libstdc++ can't use C++11 attribute syntax for GNU-specific attributes like
[[gnu::nonnull]], because those identifiers are not reserved names. We can use
__nonnull__ but only "gnu" is recognized for the namespace.

Could G++ be extended to also accept [[__gnu__::__nonnull__]] ?

__gnu__ doesn't seem to clash with anything predefined by GCC, or defined by
Glibc.