On Monday, 6 October 2014 at 13:48:07 UTC, Andrei Alexandrescu
wrote:
On 10/6/14, 12:27 AM, Walter Bright wrote:
On 10/5/2014 10:09 AM, Dicebot wrote:
On Sunday, 5 October 2014 at 17:03:07 UTC, Andrei
Alexandrescu wrote:
On 10/5/14, 9:42 AM, Dicebot wrote:
On Sunday, 5 October 2014 at 16:30:47 UTC, Ola Fosheim
Grøstad wrote:
Does D have exception chaining?
Yes. http://dlang.org/phobos/object.html#.Throwable.next
Though it seems to do more harm then good so far.
What harm does it do? -- Andrei
Good chunk of issues with pre-allocated exceptions (and
possible
cycles in
reference counted ones) comes from the chanining possibility.
At the
same time I
have yet to see it actively used as a feature.
Doesn't mean it is bad thing, just not used wide enough to
compensate for
trouble right now.
FWIW, I'm skeptical as well of the value of chaining relative
to its
cost in complexity.
It's one of those designs in which there's little room to turn.
We wanted to (a) allow destructors to throw, (b) conserve
information. Offering access to all exceptions caught was a
natural consequence. -- Andrei
Well, then again, even that promise isn't really held.
If your "catch" throws an exception, then the new exception
simply "squashes" replaces the old one:
//----
catch (Exception e)
{
thisMightThrow(); //Lose "e" here
throw e;
}
//----
I've seen literally no-one ever chain exceptions once one has
been caught. Not even druntime does it. For example, if an
exception occurs during a static array construction, this
triggers the destruction of already constructed items. If one of
*those* fails, then the cleanup loop terminates (without cleaning
the rest of the items mind you). And the user is greeted with a
"Object destruction failed", even though the array was never
constructed to begin with!
There's merit in the goal, but I don't think the current design
has achieved it.
