Access protected base class template variable

I am trying to access a protected member variable of a base class template from within the derived class template. My compiler (g++ 4.1.2) complains however:

test.cc: In member function ‘int Derived<T>::protectedVariable() const’:
test.cc:14: error: ‘protectedVariable_’ was not declared in this scope

Why is this considered an error?

I have browsed through the C++ standard and sofar I have only found confirmation that this code should compile for non-template classes (which indeed it does). As far as templates go however, I did not find anything that could shed light on this error. Did I overlook something?

Sample code (test.cc) attached.

Code:

template <class T>
class Base
{
protected:
	int protectedVariable_;
};

template <class T>
class Derived: public Base<T>
{
public:
	int protectedVariable() const
	{
		return protectedVariable_;
	}
};

int
main()
{
	Derived<int> derived;
	
	int var = derived.protectedVariable();
	
	return 0;
}

You'll want to use:

Code:

return Base<T>::protectedVariable_;

Probably has to due with template instantiation rules - but I'll defer to someone else on where the standard addresses this

gg

I think "14.6.2 Dependent Names" in the (draft) standard covers it.

gg

So it does. Personally, I prefer prefixing stuff from the base class with this->, not base_name::. That's necessary, for example, to properly resolve virtual calls.

This was also discussed recently, here.