Re: Isn't this a conversion bug in gcc?

From:

Nikolay Ivchenkov <tsoae@mail.ru>

Newsgroups:

comp.lang.c++.moderated

Date:

Thu, 29 Jul 2010 18:22:35 CST

Message-ID:

<2f48884e-e95d-4df7-b666-c018fa2c90a8@g35g2000yqa.googlegroups.com>

On 29 Jul, 17:48, Daniel Kr?gler <daniel.krueg...@googlemail.com>
wrote:

ad c) I agree that the Standard in general includes the instantiation
of definitions *when* they are required to exist and *when* they
are available.

    #include <iostream>

    int n = 0;

    template <class T>
        struct B
    {
        B()
        {
            if (n)
                f();
                // pure function call
                // (see the suggested resolution for core issue 230)
        }
        virtual void f() = 0;
    };

    template <class T>
        void B<T>::f()
            { std::cout << "B<T>::f()\n"; }

    struct D : B<int>
    {
        D()
            { static_cast<B<int> &>(*this).f(); }
        void f()
            { std::cout << "D::f()\n"; }
    };

    int main()
    {
        std::cin >> n;
        D();
    }

A definition of B<int>::f is not required to be exist. Thus, we can't
apply 14.7.1/2

"Unless a function template specialization has been explicitly
instantiated or explicitly specialized, the function template
specialization is implicitly instantiated when the specialization is
referenced in a context that requires a function definition to exist."

Must the definition of B<int>::f be instantiated?

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