[Bug c++/104787] New: [12 Regression] False positive -Wreturn-type since r12-5638-ga3e75c1491cd2d50

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104787

            Bug ID: 104787
           Summary: [12 Regression] False positive -Wreturn-type since
                    r12-5638-ga3e75c1491cd2d50
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marxin at gcc dot gnu.org
                CC: jason at gcc dot gnu.org
  Target Milestone: ---

Similarly to PR103597, the following triggers false positive without an
optimization level (reduced from godot game engine):

$ cat godot.ii
struct String {
  String(const char *);
};
struct FileAccessRef {
  FileAccessRef(int);
  ~FileAccessRef();
};
struct OS_LinuxBSD {
  String get_processor_name() const;
};
String OS_LinuxBSD::get_processor_name() const {
  FileAccessRef f = 0;
  if (true)
    return "";
}

$ g++ godot.ii -Werror=return-type -c
godot.ii: In member function ‘String OS_LinuxBSD::get_processor_name() const’:
godot.ii:15:1: error: control reaches end of non-void function
[-Werror=return-type]
   15 | }
      | ^
cc1plus: some warnings being treated as errors