http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46004
Summary: [C++0x] template constructor used to copy object Product: gcc Version: 4.6.0 Status: UNCONFIRMED Keywords: rejects-valid Severity: normal Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: r...@gcc.gnu.org CC: ja...@gcc.gnu.org [class.copy]p7 says "A member function template is never instantiated to perform the copy of a class object to an object of its class type." struct B { int i; template<typename I> explicit B(I&& ii) : i(ii) { } B(const B&) = default; }; int main() { B b(0); B bb(b); } cc.cc: In constructor 'B::B(I&&) [with I = B&]': cc.cc:15:11: instantiated from here cc.cc:7:25: error: cannot convert 'B' to 'int' in initialization Even with an explicitly declared copy constructor the template is still chosen. This only happens if the template constructor parameter type is an rvalue-reference, so only affects C++0x mode. In http://gcc.gnu.org/viewcvs?view=revision&revision=165144 I had to workaround this behaviour by replacing the template constructor by a pair of overloads, one for lvalues and one for rvalues: explicit B(const int& ii) : i(ii) { } explicit B(int&& ii) : i(ii) { }