operator class&() { return *this; } considered harmful?

michael.norrish@nicta.com.au (Michael Norrish)
Tue, 30 Oct 2007 05:22:56 GMT
I was wondering if there were any serious gotchas with including a
conversion to class& in a class's public interface.


#include <iostream>
using namespace std;

class C {
   int fld;
   C(int x) : fld(x) {}
   C(const C &r) : fld(r.fld) {}
   int get_val() { return fld; }
   operator C&() { return *this; }

C f()
   C temp(2);
   return temp;

int main()
   C &x = f();
   cout << "x = " << x.get_val() << endl;
   return 0;

Without the operator C&, I can't initialise the reference x in main
(by 8.5.3, para 5). But with it in place, it seems to me as if the
language in 12.2 para 5 then guarantees that the object nominally
allocated in f will actually have a lifetime equivalent to the scope
of main's body.

But maybe there's something I'm missing?


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