[Bug c/67132] New: gcc -D__WCHAR_TYPE__='unsigned int' should not complain about built-in types redefined

[giacomo at tesio dot it]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67132

            Bug ID: 67132
           Summary: gcc -D__WCHAR_TYPE__='unsigned int' should not
                    complain about built-in types redefined
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: giacomo at tesio dot it
  Target Milestone: ---

I have a 3rd party library that `typedef Rune uint32_t`, and gcc *properly*
complains about the signedness of the following assignment

    Rune *s = L"Άρχιμήδης";

because wchar_t is int32_b by default.

I have found that calling gcc with 

    -D__WCHAR_TYPE__='unsigned int'
    -D__WCHAR_MAX__=4294967295U
    -D__WCHAR_MIN__=0

fix the signedness problem completely, but gcc then warns about such built-in
types redeclared at command line.

It would be nice to be able to redefine such built-in types without rebuilding
gcc.