[armedbear-devel] Serious bug involving UWP

[Erik Huelsmann]

Hi Mark,

On Fri, Sep 18, 2009 at 8:50 AM, Mark Evenson <evenson at panix.com> wrote:
>
> On 9/17/09 10:36 PM, Tobias C. Rittweiler wrote:
>
> > There is another issue I'd like to raise.
> >
> >      The reason for the funny behaviour, and why it consumed a lot of
> >      time to track this bug down is because there's no global handler
> >      which prints a Stack Trace for uncaught Exceptions.
> >
> >      Instead of such a global handler, local "catch (...) { Debug.Trace
> >      ... }" are sprinkled all over the code base. And, obviously, they're
> >      easy to miss---as it has been the case here.
> >
> >      So the exception is swept under the carpet and ABCL seems to unwind
> >      the stack to some safe point, probably the toplevel, and proceed
> >      from there.
>
> Acknowledged.
>
> The current codebase seemingly suffers from a lack of a coherent plan
> for how to deal with exceptions, at least to my understanding of it.  I
> think the use of 'org.armedbear.lisp.ConditionThrowable' subclassing
> 'java.lang.Throwable' should be reconsidered, to make more consistent
> use of the [exception chaining mechanism introduced in Java 1.4][1].

I've thought about that for a bit, but I don't understand what you
mean. Do we agree that ConditionThrowable is the superclass to Go,
Return, Throw and ThreadDestroyed only? (And not to any of the Lisp
exceptions.)

> But going through the code to remove all the instances of swallowing
> exceptions to at least print diagnostic information should be rather
> easily gathered low hanging fruit.

The ConditionThrowable should probably be named TransferOfControl
instead, is what I'm now thinking. That would add to the
"self-explanatory" level in the sources, I'd say.

Bye,


Erik.