c++ - Accessing base member data error when derived class is templated -

i have following problem curiously recurring template, problem when try access data member of crtp base class.

template<typename t> struct base {   int protecteddata=10; };  struct derived : public base<derived> { public:   void method() {     std::cout<<protecteddata<<std::endl;   }; };  int main () {   derived a;   a.method(); } 

the above code compiles , runs fine , can "10" printed, if have derived class templated, like:

template<typename t> struct base {   int protecteddata=10; };  template<typename t> struct derived : public base<derived<t> > { public:   void method() {     std::cout<<protecteddata<<std::endl;   }; };  class a{};  int main () {   derived<a> a;   a.method(); } 

class dummy class served template parameter. compiler complains cannot find "protecteddata". error information following:

g++-4.9 test.cc -wall -std=c++1y -wconversion -wextra test.cc: in member function ‘void derived<t>::method()’: test.cc:26:11: error: ‘protecteddata’ not declared in scope     cout<<protecteddata<<endl; 

it doesn't have crtp, rather fact dependent-base-accessing derived code, need qualify things.

changing line to

std::cout<<this->protecteddata<<std::endl; 

solved it.

see accessing base class member in derived class.