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

From: Rene Rivera (grafik.list_at_[hidden])
Date: 2004-03-28 11:41:11

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]
>>>
>>>>A trick I use when handling HRESULT error codes is to have a 
>>>>class like this 
>>>>(adapted for int error type):
>>>>
>>>>   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?

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