I am still working on the implementation of the traits to detect operators. I have an issue with operators returning a volatile object (being a reference or not). This breaks the code I wrote to detect if the return type is void or not. In particular, the following code compiles with RET=int but not with RET=ret. Can somebody tell me why? It seems that any volatile object (reference or not) cannot be bound to a const reference apart for fundamental types. So is there any useful case to return a volatile object? If not, I can maybe just ignore those cases or it becomes to be a nightmare. By the way, it is 1:30am. I am going to bed! Frédéric struct ret { }; #define RET int RET result; RET r() { return result; } RET const rc() { return result; } RET volatile rv() { return result; } // fails to compile RET const volatile rcv() { return result; } // fails to compile RET & rr() { return result; } RET const & rcr() { return result; } RET volatile & rvr() { return result; } // fails to compile RET const volatile & rcvr() { return result; } // fails to compile int main() { RET x; x=r(); x=rc(); x=rv(); // fails with RET=ret x=rcv(); // fails with RET=ret x=rr(); x=rcr(); x=rvr(); x=rcvr(); return 0; }