[Bug objc/77404] New: Add Wobjc-root-class

["vries at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77404

            Bug ID: 77404
           Summary: Add Wobjc-root-class
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: objc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

clang supports:
- the objc_root_class attribute, and 
- a warning Wobjc-root-class that warns if a class both:
  - does not have a superclass, and
  - does not have the objc_root_class attribute

gcc:
- does not support the -Wobjc-root-class warning, and 
- when encountering the objc_root_class attribute, gives an unsupported
  attribute warning.

Is the -Wobjc-root-class warning something we want to have in gcc objc as well?