https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117382
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- [dcl.enum] p5: Each enumeration also has an underlying type. The underlying type can be explicitly specified using an enum-base. For a scoped enumeration type, the underlying type is int if it is not explicitly specified. In both of these cases, the underlying type is said to be fixed.
