Re: Exception + multiple inheritance question...

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sun, 19 Jul 2009 14:09:25 -0700 (PDT)

Message-ID:

<56fb28ce-0896-4ae7-8343-ad0313521aa4@r2g2000yqm.googlegroups.com>

On Jul 19, 6:52 pm, "Bo Persson" <b...@gmb.dk> wrote:

barcaroller wrote:

"Bo Persson" <b...@gmb.dk> wrote in message...

Then it isn't caught, because it is not an exception_base.
The inheritance goes in the other direction.

Exactly; that is why I think that the author's catch clause
is not enough. So what would be an appropriate catch clause?
The code below does not strike me as correct; why even
bother deriving from std::exception and boost::exception?

   catch (exception_base& e)
   {
        // take some action
   }
   catch (std::exception& e)
   {
        cerr << e.what() << endl
   }
   catch (boost::exception& e)
   {
       if (string const* fn=get_error_info<string>(e))
           cerr << *fn << endl;
   }

I don't know the intention of the author - could be to combine
the functionality of both exception classes, or just to show a
cool example.

Your three catch clauses will catch anything derived from
either of the base classes. Seems kind of ok to me (but a bit
weird to have both the base classes and the derived class in
the list).

Unless the derived class provides some additional details not
available in the base classes. Or represented some special type
of error, which needed separate treatment. (I would expect the
latter to be a rather frequent phenomena.)

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James Kanze (GABI Software) email:james.kanze@gmail.com
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