http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59579
Bug ID: 59579 Summary: Defaulted copy constructor of template class is instantiated even when not called (probably bug 57153) Product: gcc Version: 4.7.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: Konstantin.Sadov at gmail dot com The following code struct A{A()=default;A(A&)=default;}; template<typename B>struct C:B{C()=default; #if 1 C(const C&)=default;//Fails #else C(const C&c):B(c){};//Works #endif }; C<A> d; int main(){} produces the following error $g++ -std=c++11 main.cpp main.cpp: In instantiation of 'struct C<A>': main.cpp:9:6: required from here main.cpp:4:1: error: 'C<B>::C(const C<B>&) [with B = A]' declared to take const reference, but implicit declaration would take non-const C(const C&)=default;//Fails ^ Looks like defaulted function is implicitly instantiated even if it's not used (it's not so for user-defined functions). GCC 4.4 worked well with this case.