Re: [boost] Re: auto_array_ptr

From: Peter Dimov (pdimov_at_[hidden])
Date: 2001-04-07 07:45:34

From: "Stephen C. Gilardi" <squeegee_at_[hidden]>

> >  > The caveat about temporary smart pointer objects still applies. My
rule is
> >  > "never create an unnamed temporary smart pointer." The non-const
reference
> >  > idiom tries to enforce this rule... although I have another reason
for
> >  > preferring pass by non-const reference:
> >  >
> >>  void f(T arg);
> >  >
> >  > T t;
> >>
> >>  f(t);
> >  >
> >  > // now t is unchanged, right?
> >
> >Wrong, of course. Usually, the declaration of f isn't visible near the
call,
> >so you can't assume much about what's changed. But this case could be
seen
> >as an argument for using the unnamed temporary... then there's no object
> >hanging around with a confusing value.
>
> I don't see how t's value could be changed in the above example.
> Could you please explain?

My point exactly. Pass by value is supposed not to modify the passed object.
But, when T is std::auto_ptr, it does, changing the meaning of a built-in
language construct (pass by value) to do something "cooler."

--
Peter Dimov
Multi Media Ltd.