On Tue, Aug 03, 2010 at 03:41:35PM +0100, Garth N. Wells wrote: > On Tue, 2010-08-03 at 07:51 +0200, Florian Rathgeber wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > > Hash: SHA1 > > > > On 02.08.2010 18:50, Garth N. Wells wrote: > > > On Mon, 2010-08-02 at 10:33 +0200, Anders Logg wrote: > > >> On Sun, Aug 01, 2010 at 06:35:22PM +0100, Garth N. Wells wrote: > > >>> On Sun, 2010-08-01 at 12:40 +0200, Florian Rathgeber wrote: > > >>>> -----BEGIN PGP SIGNED MESSAGE----- > > >>>> Hash: SHA1 > > >>>> > > >>>> Hi, > > >>>> > > >>>> When using GenericTensor::down_cast() for a tentative down cast it > > >>>> would > > >>>> be helpful if it would throw std::bad_alloc (as any dynamic_cast would > > >>>> do) > > >>> > > >>> Do you mean std::bad_cast? > > >>> > > >>>> instead of invoking dolfin::error. Currently you would have to catch > > >>>> std::runtime_error and check what() to distinguish a failed cast from > > >>>> another dolfin::error, which is pretty inconvenient. Is there a > > >>>> specific > > >>>> reason why it is implemented this way? > > >>>> > > >>> > > >>> Not really. > > >>> > > >>> It's not too clear to me what you'd like. Would you prefer that > > >>> down_cast doesn't throw an error, but leave it up to the programmer to > > >>> check that a cast was successful, or just that DOLFIN catch a > > >>> std::bad_cast and print more information before throwing an error? > > >> > > >> I think the best would be if DOLFIN caught the error, then wrote an > > >> informative message (since it knows exactly what went wrong) and then > > >> threw bad_cast. > > >> > > > > > > Looks like there isn't much that can be done - std::bad_cast is only > > > thrown when casting references, not pointers (as we do internally). From > > > what I've read, our way of checking for a null pointer is correct. > > > > If down_cast() were implemented as casting the reference directly, > > dynamic_cast would throw std::bad_cast if it fails. > > > > The check for the null pointer is correct, my point is that in this case > > not a std::runtime_error should be thrown (which happens by calling > > dolfin::error), but instead the message should be printed e.g. by > > dolfin::warning and then a std::bad_cast thrown. That was Anders' > > suggestion if I got that right. > > > > In that way down_cast() could be used as a tentative cast which is not > > really possible if it throws the same exception that could be caused by > > and DOLFIN error. > > > > GenericTensor::down_cast now catches an exception and then throws an > error. It was simpler than I thought because return statements can be > used inside a try block (which I didn't know). > > Garth
Does this work as intended? It still looks like we catch the exception
and let then throw a runtime error by calling error():
catch (std::exception& e)
{
error("GenericTensor cannot be cast to the requested type: %s", e.what());
}
--
Anders
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