On Dec 5, 2011, at 2:58 PM, Marcus Denker wrote:

> Hi,
>
> With this change set, we get an error when doing the following:
>
> In the workspace do a "debug it" on this code:
>
> Transcript show: Class name
>
> then two times "step over" --> Subscript out of bounds error. Without
> the change it works.

this shows that squeak related fix should be applied with care and that we should understand deeply our system.

I'm trying but I'm not happy with my knowledge on certain parts. But since there is little documentation and some abstractions
are not aligned, this makes everything more challenging.

When I see the senders, I think that it will be delicate to fix

Process>>terminate
� � � �"Stop the process that the receiver represents forever. �Unwind to execute pending ensure:/ifCurtailed: blocks before terminating."

� � � �| ctxt unwindBlock oldList |
� � � �self isActiveProcess
� � � � � � � �ifTrue: [
� � � � � � � � � � � �ctxt := thisContext.
� � � � � � � � � � � �[ ctxt := ctxt findNextUnwindContextUpTo: nil.
� � � � � � � � � � � �ctxt isNil ] whileFalse:
� � � � � � � � � � � � � � � �[ (ctxt tempAt: 2) ifNil:
� � � � � � � � � � � � � � � � � � � �[ ctxt tempAt: 2 put: nil.
� � � � � � � � � � � � � � � � � � � �unwindBlock := ctxt tempAt: 1.
� � � � � � � � � � � � � � � � � � � �thisContext terminateTo: ctxt.
� � � � � � � � � � � � � � � � � � � �unwindBlock value ]].
� � � � � � � � � � � �thisContext terminateTo: nil.
� � � � � � � � � � � �self suspend ]
� � � � � � � � ifFalse: [
� � � � � � � � � � � �"Always suspend the process first so it doesn't accidentally get woken up"
� � � � � � � � � � � � oldList := self suspend.
� � � � � � � � � � � �suspendedContext ifNotNil:[
� � � � � � � � � � � � � � � �"Figure out if we are terminating the process while waiting in Semaphore>>critical:
� � � � � � � � � � � � � � � �In this case, pop the suspendedContext so that we leave the ensure: block inside
� � � � � � � � � � � � � � � �Semaphore>>critical: without signaling the semaphore."
� � � � � � � � � � � � � � � �(oldList class == Semaphore and:[
� � � � � � � � � � � � � � � � � � � �suspendedContext method == (Semaphore compiledMethodAt: #critical:)]) ifTrue:[
� � � � � � � � � � � � � � � � � � � � � � � �suspendedContext := suspendedContext home.].

� � � � � � � � � � � � �"If we are terminating a process halfways through an unwind, try to complete that unwind block first."
� � � � � � � � � � � � � � � �(suspendedContext findNextUnwindContextUpTo: nil) ifNotNil: [ :outer |
� � � � � � � � � � � � � � � �(suspendedContext findContextSuchThat: [ :c | c closure == (outer tempAt: 1)])
� � � � � � � � � � � � � � � � � � � �ifNotNil: [ :inner |
� � � � � � � � � � � � � � � � � � � � � � � � "This is an unwind block currently under evaluation"
� � � � � � � � � � � � � � � � � � � � � � � �suspendedContext runUntilErrorOrReturnFrom: inner ]].
� � � � � � � � � � � �ctxt := self popTo: suspendedContext bottomContext.
� � � � � � � � � � � �ctxt == suspendedContext bottomContext ifFalse: [
� � � � � � � � � � � � � � � �self debug: ctxt title: 'Unwind error during termination']] ].

Process>>complete: aContext
� � � �"Run self until aContext is popped or an unhandled error is raised. �Return self's new top context, unless an unhandled error was raised then return the signaler context (rather than open a debugger)."

� � � �| ctxt pair error |
� � � �ctxt := suspendedContext.
� � � �suspendedContext := nil. �"disable this process while running its stack in active process below"
� � � �pair := ctxt runUntilErrorOrReturnFrom: aContext.
� � � �suspendedContext := pair first.
� � � �error := pair second.
� � � �error ifNotNil: [^ error signalerContext].
� � � �^ suspendedContext

>
> On Wed, Nov 16, 2011 at 8:58 PM, Eliot Miranda <eliot.miranda@gmail.com> wrote:
>> Hi All,
>>
>> � � I've found a bug in ContextPart>>#runUntilErrorOrReturnFrom: that in a
>> certain rare circumstance causes the method to peel back too much of the
>> stack. �This method is used in the debugger (e.g. completeStep: et al) but
>> also in Process termination. �So it is right at the heart of the system.
>> �I'm loath to simply commit it �I'd really appreciate y'all testing with the
>> fix and reporting any changes you see. �It does not affect the trunk test
>> suite (there is a test, WeakSetInspectorTest, which is unreliable, but apart
>> form that no observed effects). �So, brave souls, please try with the
>> attached and see if you come to grief or not.
>> --
>> thanks,
>> Eliot
>>
>
>
>
> --
> --
> Marcus Denker �-- �denker@acm.org
> http://www.marcusdenker.de
>