[boost] cref with VC++ 6 calls copy ctor

From: Robin (darkaurora_at_[hidden])
Date: 2002-05-28 23:10:14

The below snippet shows the cref calls the copy ctor when compiled
with VC++ 6 sp5. I believe it shouldn't occur  yet I can't find out
where the copy is created.

I would think making a copy would defeat the purpose of ref. So, can
anyone confirm/suggest alternatives?

Note: Comeau and g++2.95 (mingw) does NOT call the copy ctor.

// BEGIN
#include <boost/ref.hpp>
#include <iostream>

using  namespace       boost;
using  namespace       std;

class  C
{
public:

       C()     :       i_(0)
       {
               cout << "Default ctor\n";
       }

       C( int i )      :       i_(i)
       {
               cout << "Explicit ctor\n";
       }

       C( const C &c ) :       i_(c.i_)
       {
               cout << "Copy ctor\n";
       }

       C&      operator=( const C &c )
       {
               cout << "= operator\n";
               i_ = c.i_;
               return  *this;
       }

       int     i_;
};

void   Print( int i, const C &c )
{
       cout << i << " " << c.i_ << endl;
}

int    main()
{
       C c(4);

       //      Print( 3,  c );

       // Generates extra copy ctor in VC++ 6
       Print( 3, cref( c ) );

       return  0;
}