prog.cpp: In function ‘int main()’:
prog.cpp:17:10: error: no matching function for call to ‘Foo::Foo(Foo&)’
Foo c = a; // ERROR, copy ctor is explicit
^
prog.cpp:17:10: note: candidate is:
prog.cpp:7:2: note: Foo::Foo()
Foo() { }
^
prog.cpp:7:2: note: candidate expects 0 arguments, 1 provided