Encountered it again today. This time while stepping over something it ran
into a self break, but instead of interrupting, the image froze until I
pressed Cmd+. Now I get countless debuggers on the self break frame plus
many more countless debuggers on Context>>cannotReturn:to: with a
BlockCannotReturn exception.

It only hang for about 10 seconds and is still spawning debuggers after
half an hour... I don't know whether this will ever come to an end.

--- The full stack ---
[] in DosFileDirectory(FileDirectory)>>deleteFileNamed:ifAbsent:
StandardFileStream class>>retryWithGC:until:forFileNamed:
DosFileDirectory(FileDirectory)>>deleteFileNamed:ifAbsent:
SmalltalkImage>>logError:inContext:to:
SmalltalkImage>>logSqueakError:inContext:
[] in Debugger class>>openOn:context:label:contents:fullView:
BlockClosure>>on:do:
Debugger class>>openOn:context:label:contents:fullView:
ECToolSet class(StandardToolSet
class)>>debugProcess:context:label:contents:fullView:
ToolSet class>>debugProcess:context:label:contents:fullView:
Process>>debug:title:full:contents:
Process>>debug:title:full:
Process>>debug:title:
ECToolSet class(StandardToolSet class)>>handleError:
ToolSet class>>handleError:
UnhandledError>>defaultAction
UndefinedObject>>handleSignal:
UnhandledError(Exception)>>signal
UnhandledError class>>signalForException:
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
BlockCannotReturn(Error)>>defaultAction
BlockCannotReturn>>defaultAction
UndefinedObject>>handleSignal:
BlockCannotReturn(Exception)>>signal
Context>>cannotReturn:to:
Context>>cannotReturn:
[] in BlockClosure>>newProcess

Am Mo., 23. Dez. 2019 um 20:05 Uhr schrieb Thiede, Christoph <
Christoph.Thiede at student.hpi.uni-potsdam.de>:

> Hi Jakob,
>
>
> yes, these observations are very well known to me ... :)
>
> > Is there a way to stop this if it happens? I have "Open tools attached
> to hand" activated so I cannot click on Do > Utilities closeAllDebuggers...
>
> FYI, you can also press Ctrl + 5 to open the "Do" menu and then type "De"
> + Enter to perform "Utilities closeAllDebuggers".
> Or modify Marcel's changeset from May (cmd-dot-dialog.cs) and add the
> command there :)
>
> However, we should sharpen our error detection while opening a debugger.
> This would make it so much easier to debug such problems ...
>
> Best,
> Christoph
>
> ------------------------------
> *Von:* Squeak-dev <squeak-dev-bounces at lists.squeakfoundation.org> im
> Auftrag von Jakob Reschke <forums.jakob at resfarm.de>
> *Gesendet:* Montag, 23. Dezember 2019 17:55:38
> *An:* The general-purpose Squeak developers list
> *Betreff:* [squeak-dev] Endless debuggers (was: The Inbox:
> Morphic-ct.1610.mcz)
>
> Am Mo., 16. Dez. 2019 um 14:32 Uhr schrieb Marcel Taeumel <
> marcel.taeumel at hpi.de>:
>
>> Hi Christoph,
>>
>> hmm... I would rather not spread that recursion flag to outside Debugger
>> class >> #openOn:... I will look into it. Thanks for those two bug reports
>> that cause endless debuggers:
>>
>> 1. Generator step-over
>> Generator on: [:g | g yield: #foo].
>>
>> 2. Error in a debugger's build-with method.
>>
>> Best,
>> Marcel
>>
>
> FYI today there are still some cases that spawn endless debuggers.
>
> It had it twice today, but unfortunately can't give you exacts steps for
> reproduction.
> 1. Debug a test case, step over some long operation, interrupt with Cmd+.
> to because of impatience, step so far in the second debugger that control
> could theoretically return to the first one. Then there was some Context on
> the top of the stack that did not seem to belong there, with a return
> handler... Well I had a manual ping-pong situation between the two
> debuggers. After pressing the wrong button it resulted in an endless stream
> of new debuggers about not being able to return.
> 2. Press Into at the wrong place during a return handler (ensure:).
> Endless debuggers about aboutToReturn:through: (I saw that somewhere). The
> stack trace shows back-and-forth between Message>>sentTo: and
> UndefinedObject doesNotUnderStand: #findContextSuchThat: -- see attachment.
>
> Maybe I should finally start to remember taking screenshots. Both cases
> seemed to be related to stack unwinding or ensure: actions though.
>
> Is there a way to stop this if it happens? I have "Open tools attached to
> hand" activated so I cannot click on Do > Utilities closeAllDebuggers...
>
> Merry Christmas everyone.
> Kind regards,
> Jakob
>
>
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