http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47599 --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-02-04 08:33:03 UTC --- It is a builtin type (for C++ it is exposed as the keyword, wchar_t). For C, the headers define the type, see the preprocessed source to show that is the case.