http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48224
Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution| |INVALID --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-03-21 19:24:26 UTC --- I think this is correct as structure is incomplete when the instantiation of std::pair<const int, structure> happens which is in SetMos. Try: #include <map> struct structure; typedef std::map<int, structure> mapOfStructure; class simpleClass { mapOfStructure m_mos; const mapOfStructure& GetMos () const { return m_mos; } inline void SetMos ( const mapOfStructure& v ); }; struct structure { int i; }; inline void simpleClass::SetMos ( const mapOfStructure& v ) { m_mos = v; } --- CUT --- Which is fixes the problem as pair needs both template arguments to be complete when SetMos is declared. Note I think it is needed for simpleClass is also declared really. So moving the declaration of structure before simpleClass is the correct fix really.