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

From: Gennaro Prota (gennaro_prota_at_[hidden])
Date: 2004-03-28 10:40:21

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...)

Genny.