-----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. Florian > Garth > >> -- >> Anders > > -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.12 (MingW32) iEYEARECAAYFAkxXrlAACgkQ8Z6llsctAxaMqgCfSqDc/Ii5B41knpwHFVWsjSLF H3AAn1pOlxXJd/PnDbVWNcyF5GNNmPt8 =uibh -----END PGP SIGNATURE-----
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