Re: Help with explicit instantiation

[Yevgen Muntyan]

E. Robert Tisdale wrote:
> > > What did I do wrong?

Hi,
it seems to be very old bug - look at 
http://gcc.gnu.org/ml/gcc-prs/2000-q3/msg00288.html

To workaround it maybe try to use extra parameter: X<T>(X<S>, int).
The following code compiles well with gcc-3.4.

Yevgen


/////////////////////////////////////////////////
// X.h

#ifndef GUARD_X_H
#define GUARD_X_H 1
#include <iostream>

template<class T>
class X {
private:
        // representation
        T     D;
public:
        // functions
        T data(void) const { return D; }
        // constructors
        X(T d = 0): D(d) { }
        X(const X& x);
        template<class S>
        X(const X<S>& x, int i = 0);
        friend
        std::ostream& operator<<(std::ostream& os, const X<T>& x) {
                return os << x.data();
        }
};

#endif//GUARD_X_H 1

///////////////////////////////////////////
// X.cc

#include "X.h"

template<class T>
X<T>::X(const X& x): D(x.D)
{
        std::cerr << "copy constructor" << std::endl;
}

template<class T>
template<class S>
X<T>::X(const X<S>& x, int i): D(x.data())
{
        std::cerr << "conversion constructor" << std::endl;
}


template X<float>::X(const X<int>& x, int);
template X<float>::X(const X<float>& x);

void f()
{
        X<float> a(X<float>(1.0));
        X<float> b(X<int>(1));
}