The code below compiles in both Visual C++ 5.0 and 6.0. but the code
invokes the STL standard operator:

        istream & operator >> (istream &, string &)

Wouldn't the overload resolution rules indicate that the user defined
operator should be chosen, since it is a better match on the second
argument?

Is this a Microsoft bug ?


I know Stroustrup recommends that the string class not be used as a base
class (Stroustrup, C++ Programming Language, 3rd edition, Section 20.3),
but the question is, what should a conforming compilere do ?

Thanks.


#include <iostream>
#include <fstream>
#include <string>

using namespace std;

class mystring : public string
{ public:
   mystring(char *p="") : string(p)
   {}
};

istream & operator >> (istream & i, mystring & s)  // use defined
function
{  cout << "in the operator" << endl;
   return i;
}

void main()
{
   ifstream in("mary.txt");
   mystring s;

   in >> s;    // This line compiles in VC++ 5.0 and 6.0
               // but calls the  STL standard operator
               //    operator >> (istream &i, string &s)
               // instead of the user defined operator
               //    istream & operator >> (istream &, mystring &)
   cout << s;
}
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