🚀 go-pugleaf

James Kanze US/ESC 60/3/141 #40763 <kanze@lts.sel.alcatel.de> wrote:

>The real danger is in the following:
>
>	auto_ptr< T >	p1 ;
>	auto_ptr< T >	p2 ;
>
>	if ( p1 == p2 ) ...
>
>You thought you were comparing two pointers, but in fact, you are
>comparing the results of comparing these pointers to null.  The
>expression in the if (illegal with the current definition) will cause
>the conversion operator bool to be called for both pointers.

> ...  The `obvious' solution for
>auto_ptr is to add an `isValid' function; in the meantime, just use
>`if ( ptr.get() == NULL )'.  (Another possible alternative is to
>provide a conversion operator to the underlying pointer type, so that
>you can write `if ( ptr == NULL )', just as you would with a normal
>pointer.  I personally don't like the fact that this might result in
>free pointers to the memory without having called a function
>explicitly.) 

Why not just have

private:
  bool auto_ptr<T>::operator==(const auto_ptr<T>&)

public:
  bool auto_ptr<t>::operator==(void *p)
    { return (this->get() == NULL) && (p == NULL); }

The latter would return true if and only if both the auto_ptr and the
passed pointer were NULL.
-------------------------------------------------------------
Pablo Halpern                   phalpern@truffle.ultranet.com

I am self-employed. Therefore, my opinions *do* represent 
those of my employer.
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