Re: Internal compiler error

[Mark Crosland <mjc at c1000907-b dot sttls1 dot wa dot home dot com>]

A couple of observations that muddy the waters a little for me...

- If the typename qualifier is removed from the aStructPtr definition,
gcc(egcs 1.1.2) suggests trying typename.

- I have modified my example so the typename construct is accepted by
gcc (egcs-1.1.2) inside a function within the B template class. It looks
like the statement "typename derivedClass::aStruct * aStructPtr;" is being
handled differently depending on whether it is a member variable or a
function variable (?).

Here is the modified example.

Thanks,
Mark

//////////////////////////////////////////////////////////////////

#include <stdio.h>

template <class derivedClass> class B {


    public:
        B(){}
        ~B(){}
        bOperation1()
        {
            typename derivedClass::aStruct aStructPtr;
            aStructPtr.x = -1;
            printf("aStructPtr.x:%d\n",aStructPtr.x);
            aPtr->aOperation();
        }

    protected:
        int x;
        derivedClass * aPtr;
        //typename derivedClass::aStruct * aStructPtr;
};

class A : public B <A> {

    protected:
        typedef struct { int x; } aStruct;

    public:
        A(){}
        ~A(){}

        void aOperation()
        {
            aStruct as;
            as.x = 1;
            printf("as.x:%d\n",as.x);
        }
};

int main()
{
    A anA;

    anA.bOperation1();
}

///////////////////////////////////////////////////////////////////


On Sun, 24 Oct 1999, Martin v. Loewis wrote:
> 
> The problem is the specific member declaration:
> 
>   typename derivedClass::aStruct * aStructPtr;
> 
> which is not accepted. In a previous message, I wrote that I thought
> the construct was ok and that there was a bug in gcc; after thinking
> about it again, I now believe that gcc is right.
> 
> The question is when exactly the template is instantiated. Clearly,
> the instantiation must be complete before the template can be used as
> a base class, since the base class must be a complete class. This is
> necessary as the parsing of the derived class might refer to names in
> the base class.
> 
> The point-of-instantiation is defined in 14.6.4.1/3:
> 
> # Otherwise, the point of instantiation for such a specialization
> # immediately precedes the namespace scope declaration or definition
> # that refers to the specialization.
> 
> So the template is instantiated immediately before the derived class
> is defined (which is immediately after the point-of-declaration of the
> derived class).
> 
> Therefore, inside the template instantiation, the template parameter
> is an incomplete type. typename derivedClass::aStruct is an error; the
> declaration of A::aStruct has not been seen, yet. Hence the error
> message.
> 
> Hope this clarifies it,
> Martin
>