[boost] Re: implicit smart pointer conversions

From: Greg Colvin (gcolvin_at_[hidden])
Date: 2000-03-19 05:06:54

From: Nathan Myers <ncm_at_[hidden]>
> On Sat, Mar 18, 2000 at 10:01:31AM -0500, Mark Borgerding wrote:
> > Greg Colvin wrote:
> > > (somebody) wrote: 
> > > > The idea was that the implicit casts like:
> > > >   operator T*() const throw() { return ptr; }
> > > > be replaced with:
> > > >   operator void*() const throw() { return ptr; }
> > > > [so that] such a pointer can be checked for NULLness...
> > > > but cannot be dereferenced by accident.
> > >
> > > The impasse is that some users of smart pointers, myself
> > > included, actually want operator T*().  If you have generic
> > > code written to accept pointers then operator void*() won't
> > > do, and neither will get().
> > ... 
> > I think the slight unwieldiness of using get() is a small 
> > price to pay for fewer runtime errors.  If I have to choose between 
> > compile-time checks and ease of use,  I will choose the compile-time 
> > checks nearly every time.
> 
> Indeed, some of us argued for naming them member of auto_ptr<> that
> reveals the raw pointer value "auto_ptr<>::leak()".  To me it seems
> a grave, grave design error to provide an automatic conversion for
> that purpose.  Automatic conversions are dangerous enough in general, 
> but when they contradict the base purpose of the component, it makes
> me wonder why somebody wants such a component at all.
> 
> If I may be allowed an analogy, it's like nipping the ground post off
> of a three-prong power cord so it can be used in a two-hole power socket.

True.  But rather than chop them off we have these nice little adaptors
called ground lifts.  Risky, but often necessary to stop the hum in a sound
system, and when the electrical power to a stage is improperly wired it is
sometimes safer not to be grounded.