Re: [boost] Re: Standard C Library and C++ / BOOST

From: Rob Stewart (stewart_at_[hidden])
Date: 2004-03-30 10:46:01

From: Rene Rivera <grafik.list_at_[hidden]>
> Gennaro Prota wrote:
> > On Sat, 27 Mar 2004 19:23:50 -0500, David Abrahams
> > <dave_at_[hidden]> wrote:
> >>"Klaus Nowikow" <nowikow_at_[hidden]> writes:
> >>>Reece Dunn wrote:
> >>>[snip]
> >>>
> >>>>   class errorcheck
> >>>>   {
> >>>[snip]
> >>>>      public:
> >>>>         inline errorcheck( int ec ): error( ec )
> >>>>         {
> >>>>            if( ec < 0 ) throw( *this );
> >>>>         }
> >>>
> >>>Careful. Throwing an exception from a constructor
> >>>means that the object won't be constructed (i. e., does not exist).
> >>>So you are throwing a non-existing object here.
> >>>
> >>>Or am I wrong?
> >>
> >>You're wrong.  *this is copied before it is thrown.  Still, the idiom
> >>above seems a bit suspicious, unless you somehow prevent derivation
> >>from errorcheck.
> > 
> > I can't believe you are justifying the above. You copy an object that
> > doesn't exist yet! (The class is not a POD and has a non trivial
> > constructor - and even if this wasn't the case...)
> 
> I don't see how the object is not fully initialized inside its constructor?? 
> Could you explain your objection?

Until the ctor finishes -- after the closing } -- there is no
object (see 3.8/1).

-- 
Rob Stewart                           stewart_at_[hidden]
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;