Things you mustn't do:
1) end an enum with a comma

2) #include <cxxxx> and not use std::

3) use anonymous structures

All three things are invalid C++. Anonymous structures inside
anonymous unions are allowed by GCC, but that doesn't mean it's valid.

expression, which subsequently got overwritten by the (real) expression.

There were both variants, with and without extra semicolon.

Done with Thorbjørn Lindeijer