🚀 go-pugleaf

In article <bill-0504961003150001@bgibbons.vip.best.com>,
Bill Gibbons <bill@gibbons.org> wrote:
>
>Transfer of ownership is not the end goal - the end goal is
>to make auto_ptr useful for the "resource acquisition is
>initialization" idiom.  That is very painful without transfer
>of ownership.
>
>In particular, if you want to do the resource acquisition in a
>function called by the function which needs to hold the resource,
>there is no good exception-safe way to pass the pointer from the
>callee to the caller.
>
>You can get close (at some cost in clarity):
>
       [ snip... ]

It is not clear at all that the copy semantics of auto_ptr
are essential for exception-safe transfer of resources.
The same example coded as follows does not use
the copy semantics of auto_ptr:


    extern X* get_X();   // returns a resource acquired
			 // by the callee, to be deleted
			 // by the caller.

    void f() {
        auto_ptr<X> ptr = get_X();
			// resource allocated by get_X()
        ...
   }

And get_X() is not unnecessarily complicated either:

   X* get_X()
   {
      auto_ptr<X> p = new X;

      // ... stuff that could throw an exception

      // We got here. Means normal return.
      return p.release();
   }


What's wrong with this? It doesn't require copy semantics
for auto_ptr. Yet both the caller and the callee
are exception safe and there is no loss of clarity.

-- 
Ajay Kamdar        |    Email: ajay@lehman.com    |    Standard Disclaimer 
Lehman Brothers    |    Phone: (201) 524-5048     |
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