renaming a class causes invalid super pointer CompiledMethod..!

Hi Chris, Hi Colin,

On Thu, Jan 15, 2015 at 2:48 PM, Chris Muller <[hidden email]> wrote:

I did a minor class-hierarchy refactoring today which resulted in a an
invalid super pointer, resulting in a confusing image lock up due to
tight recursion.  The script, below, demonstrates the issue in trunk:

Object compile: 'test  ^''Hello from Object'''.
(Object subclass: #MyClass instanceVariableNames: ''
classVariableNames: '' poolDictionaries: '' category: 'Test') compile:
'test  ^ super halt test, ''my super call lands on myself!'''.
(Smalltalk classNamed: #MyClass) rename: 'MyNewAbstraction'.
((Smalltalk classNamed: #MyNewAbstraction) subclass: #MyClass
instanceVariableNames: '' classVariableNames: '' poolDictionaries: ''
category: 'Test').
(Smalltalk classNamed: #MyNewAbstraction) new test

But an existing method in the original MyClass had a call to super
which now lands in itself, resulting in a tight recursion.

The same script without creating the new subclass results in an
instant VM crash (both interpreter 2357 and cog 3205):

Object compile: 'test  ^''Hello from Object'''.
(Object subclass: #MyClass instanceVariableNames: ''
classVariableNames: '' poolDictionaries: '' category: 'Test') compile:
'test  ^ super halt test, ''my super call lands on itself!'''.
(Smalltalk classNamed: #MyClass) rename: 'MyNewAbstraction'.
(Smalltalk classNamed: #MyNewAbstraction) new test

I even tried recompiling my entire class hierarchy which was renamed,
but it didn't help.

How can this be?  I _KNOW_ I've used rename class many times in the
past...  A regression?

This is indeed an Environments regression.  The issue is where to fix the problem.  One way to look at it is that Environment>>renameClass:from:to: does not update bindings in the renamed class's methods.

Here's what the old code did:

SystemDictionary>>renameClass: aClass from: oldName to: newName

"Rename the class, aClass, to have the title newName."

| oldref category |

category := SystemOrganization categoryOfElement: oldName.

self organization classify: newName under: category suppressIfDefault: true.

self organization removeElement: oldName.

oldref := self associationAt: oldName.

self removeKey: oldName.

** oldref key: newName.

self add: oldref.  "Old association preserves old refs"

Smalltalk renamedClass: aClass from: oldName to: newName.

self flushClassNameCache.

SystemChangeNotifier uniqueInstance classRenamed: aClass from: oldName to: newName inCategory: category 

The starred line changes the key on the old class's binding, meaning that all the methods whose methodClassAssociation is that binding get automatically updated (note that class methods have a methodClassAssociation that has no key and just points to the class object).

The new code simply forgets to do this:

Environment>>renameClass: aClass from: oldName to: newName

"Rename the class, aClass, to have the title newName."

| binding category |

category := self organization categoryOfElement: oldName.

self organization classify: newName under: category suppressIfDefault: true.

self organization removeElement: oldName.

binding := self declarationOf: oldName.

declarations removeKey: oldName.

self binding: binding removedFrom: self.

binding := newName => aClass.

declarations add: binding. 

self binding: binding addedTo: self.

Smalltalk renamedClass: aClass from: oldName to: newName.

SystemChangeNotifier uniqueInstance 

classRenamed: aClass 

from: oldName 

to: newName 

inCategory: category

But should the change go in Environment>>renameClass:from:to: or in the BindingPolicy?  i.e. it could be implemented either in Environment>>renameClass:from:to:, or in Environment>>showBinding:.  I guess the former, but I'm cc'ing Colin, because know it?, he wrote it!

In any case there needs to be a test that checks that a method's methodClassAssociation is correctly updated after a rename.  I bet Colin would have not made this slip had there been a test.

Here's the code I used to test this:

| mca1 mca2 |

Object compile: 'test  ^''Hello from Object'''.

(Object

subclass: #MyClass instanceVariableNames: ''

classVariableNames: ''

poolDictionaries: ''

category: 'Test')

compile: 'test  ^ super halt test, ''my super call lands on itself!'''.

mca1 := ((Smalltalk classNamed: #MyClass)>>#test) methodClassAssociation.

(Smalltalk classNamed: #MyClass)

rename: 'MyNewAbstraction'.

mca2 := ((Smalltalk classNamed: #MyNewAbstraction)>>#test) methodClassAssociation.

{ mca1. mca2. mca1 == mca2. mca1 == (Smalltalk bindingOf: #MyNewAbstraction). mca2 == (Smalltalk bindingOf: #MyNewAbstraction)}

It answers { #MyClass=>nil . #MyClass=>nil . true . false . false}

i.e. the binding isn't updated, but changes from #MyClass=>MyClass to #MyClass=>nil in binding:removedFrom:.

--

HTH,

Eliot

Hi Eliot, there were TWO problems, Bert and Tobias have fixed one of
them.  The second one is still unfixed in trunk.  When you run this
script and arrive at the debugger, step INTO:

Object compile: 'test  ^''Hello from Object'''.
(Object subclass: #MyClass instanceVariableNames: ''
classVariableNames: '' poolDictionaries: '' category: 'Test') compile:
'test  ^ super halt test, ''my super call lands on itself!'''.
(Smalltalk classNamed: #MyClass) rename: 'MyNewAbstraction'.
(Smalltalk classNamed: #MyNewAbstraction) new test

then be sure to step INTO the super call to #test.  See how it lands
you in teh same method?  THAT bug exists back at least as far back as
4.2, so I don't think its Environments related.

I took a look at it and presented my findings in the other email
thread with subject "The Inbox: Environments-cmm.52.mcz", -- that
screenshot showing that the bytecodes are teh same and the literal
binding looks correct.

So I have no idea why its not calling super correctly...


On Tue, Jan 20, 2015 at 2:38 PM, Eliot Miranda <[hidden email]> wrote:
>
> Ugh, I'm behind the times, Tobias you've already fixed it; thanks!  Tobias, I like your use of becomeForward:; it is more robust.  But I *think* the undeclared removal is misplaced.  Don't you think that that code belongs in the BindingPolicy?
>
> On Tue, Jan 20, 2015 at 12:33 PM, Eliot Miranda <[hidden email]> wrote:
>>
>>
>>
>> On Tue, Jan 20, 2015 at 12:26 PM, Eliot Miranda <[hidden email]> wrote:
>>>
>>> Hi Chris, Hi Colin,
>>>
>>>
>>> On Thu, Jan 15, 2015 at 2:48 PM, Chris Muller <[hidden email]> wrote:
>>>>
>>>> I did a minor class-hierarchy refactoring today which resulted in a an
>>>> invalid super pointer, resulting in a confusing image lock up due to
>>>> tight recursion.  The script, below, demonstrates the issue in trunk:
>>>>
>>>> Object compile: 'test  ^''Hello from Object'''.
>>>> (Object subclass: #MyClass instanceVariableNames: ''
>>>> classVariableNames: '' poolDictionaries: '' category: 'Test') compile:
>>>> 'test  ^ super halt test, ''my super call lands on myself!'''.
>>>> (Smalltalk classNamed: #MyClass) rename: 'MyNewAbstraction'.
>>>> ((Smalltalk classNamed: #MyNewAbstraction) subclass: #MyClass
>>>> instanceVariableNames: '' classVariableNames: '' poolDictionaries: ''
>>>> category: 'Test').
>>>> (Smalltalk classNamed: #MyNewAbstraction) new test
>>>>
>>>> But an existing method in the original MyClass had a call to super
>>>> which now lands in itself, resulting in a tight recursion.
>>>>
>>>> The same script without creating the new subclass results in an
>>>> instant VM crash (both interpreter 2357 and cog 3205):
>>>>
>>>> Object compile: 'test  ^''Hello from Object'''.
>>>> (Object subclass: #MyClass instanceVariableNames: ''
>>>> classVariableNames: '' poolDictionaries: '' category: 'Test') compile:
>>>> 'test  ^ super halt test, ''my super call lands on itself!'''.
>>>> (Smalltalk classNamed: #MyClass) rename: 'MyNewAbstraction'.
>>>> (Smalltalk classNamed: #MyNewAbstraction) new test
>>>>
>>>> I even tried recompiling my entire class hierarchy which was renamed,
>>>> but it didn't help.
>>>>
>>>> How can this be?  I _KNOW_ I've used rename class many times in the
>>>> past...  A regression?
>>>
>>>
>>> This is indeed an Environments regression.  The issue is where to fix the problem.  One way to look at it is that Environment>>renameClass:from:to: does not update bindings in the renamed class's methods.
>>>
>>> Here's what the old code did:
>>>
>>> SystemDictionary>>renameClass: aClass from: oldName to: newName
>>> "Rename the class, aClass, to have the title newName."
>>>
>>> | oldref category |
>>> category := SystemOrganization categoryOfElement: oldName.
>>> self organization classify: newName under: category suppressIfDefault: true.
>>> self organization removeElement: oldName.
>>> oldref := self associationAt: oldName.
>>> self removeKey: oldName.
>>> ** oldref key: newName.
>>> self add: oldref.  "Old association preserves old refs"
>>> Smalltalk renamedClass: aClass from: oldName to: newName.
>>> self flushClassNameCache.
>>> SystemChangeNotifier uniqueInstance classRenamed: aClass from: oldName to: newName inCategory: category
>>>
>>> The starred line changes the key on the old class's binding, meaning that all the methods whose methodClassAssociation is that binding get automatically updated (note that class methods have a methodClassAssociation that has no key and just points to the class object).
>>>
>>> The new code simply forgets to do this:
>>>
>>> Environment>>renameClass: aClass from: oldName to: newName
>>> "Rename the class, aClass, to have the title newName."
>>>
>>> | binding category |
>>> category := self organization categoryOfElement: oldName.
>>> self organization classify: newName under: category suppressIfDefault: true.
>>> self organization removeElement: oldName.
>>> binding := self declarationOf: oldName.
>>> declarations removeKey: oldName.
>>> self binding: binding removedFrom: self.
>>> binding := newName => aClass.
>>> declarations add: binding.
>>> self binding: binding addedTo: self.
>>> Smalltalk renamedClass: aClass from: oldName to: newName.
>>> SystemChangeNotifier uniqueInstance
>>> classRenamed: aClass
>>> from: oldName
>>> to: newName
>>> inCategory: category
>>>
>>>
>>> But should the change go in Environment>>renameClass:from:to: or in the BindingPolicy?  i.e. it could be implemented either in Environment>>renameClass:from:to:, or in Environment>>showBinding:.  I guess the former, but I'm cc'ing Colin, because know it?, he wrote it!
>>
>>
>> and if the fix should indeed go in Environment>>renameClass:from:to: , it is as simple as
>>
>> Environment>>renameClass: aClass from: oldName to: newName
>> "Rename the class, aClass, to have the title newName."
>>
>> | binding category |
>> category := self organization categoryOfElement: oldName.
>> self organization classify: newName under: category suppressIfDefault: true.
>> self organization removeElement: oldName.
>> binding := self declarationOf: oldName.
>> declarations removeKey: oldName.
>> self binding: binding removedFrom: self.
>> binding := newName => aClass.
>> declarations add: binding.
>> self binding: binding addedTo: self.
>>
>> ** aClass updateMethodBindingsTo: binding.
>> Smalltalk renamedClass: aClass from: oldName to: newName.
>> SystemChangeNotifier uniqueInstance
>> classRenamed: aClass
>> from: oldName
>> to: newName
>> inCategory: category
>>
>> I'll make this change and we can alter later if Colin thinks it's in the wrong place.
>>
>>>
>>>
>>> In any case there needs to be a test that checks that a method's methodClassAssociation is correctly updated after a rename.  I bet Colin would have not made this slip had there been a test.
>>>
>>>
>>> Here's the code I used to test this:
>>>
>>> | mca1 mca2 |
>>> Object compile: 'test  ^''Hello from Object'''.
>>> (Object
>>> subclass: #MyClass instanceVariableNames: ''
>>> classVariableNames: ''
>>> poolDictionaries: ''
>>> category: 'Test')
>>> compile: 'test  ^ super halt test, ''my super call lands on itself!'''.
>>> mca1 := ((Smalltalk classNamed: #MyClass)>>#test) methodClassAssociation.
>>> (Smalltalk classNamed: #MyClass)
>>> rename: 'MyNewAbstraction'.
>>> mca2 := ((Smalltalk classNamed: #MyNewAbstraction)>>#test) methodClassAssociation.
>>> { mca1. mca2. mca1 == mca2. mca1 == (Smalltalk bindingOf: #MyNewAbstraction). mca2 == (Smalltalk bindingOf: #MyNewAbstraction)}
>>>
>>> It answers { #MyClass=>nil . #MyClass=>nil . true . false . false}
>>> i.e. the binding isn't updated, but changes from #MyClass=>MyClass to #MyClass=>nil in binding:removedFrom:.
>>>
>>>
>>> --
>>> HTH,
>>> Eliot
>>
>>
>>
>>
>> --
>> best,
>> Eliot
>
>
>
>
> --
> best,
> Eliot
>
>
>

Hi Chris

On 21.01.2015, at 17:39, Chris Muller <[hidden email]> wrote:

> Okay, I found the invalid super-pointer behavior.
>
> It's a lot better with Bert & Tobias' fix, but still there to a smaller degree..
>
> Object compile: 'test  ^''Hello from Object'''.
> (Object subclass: #MyClass instanceVariableNames: ''
> classVariableNames: '' poolDictionaries: '' category: 'Test') compile:
> 'test  self halt.  ^ super test, ''my super call lands on myself!'''.
> (Smalltalk classNamed: #MyClass) rename: 'MyNewAbstraction'.
> ((Smalltalk classNamed: #MyNewAbstraction) subclass: #MyClass
> instanceVariableNames: '' classVariableNames: '' poolDictionaries: ''
> category: 'Test').
> (Smalltalk classNamed: #MyClass) new test
>
> Do-it on the above.  When the debugger appears, simply highlight the
> code "super test" in the debugger and press "Print It".
>
> I expected to see 'Hello from Object' but it seems to be calculating
> super from the receiver class rather than the method's home class...
>
> WITHOUT Bert and Tobias' fix, the above results in the super call
> truly landing on itself, and if you take the halt out, the
> tight-recursion I mentioned from teh first paragraph of this thread.
> WITH their fix, the problem only manifests in the debugger as
> demonstrated.

If you hit step-into, you actually end up in the Superclass.
_Only_ if you select 'super test' and PrintIt (or DoIt), the
apparent “recursion” is triggered.
  This is due to the way DoIt work, they compile an anonymous class
that are “homed” in the receivers class, in this case MyClass. Hence,
super ends up in MyNewAbstraction[1].
  Yes, this is a bit surprising, but I don't know whether it is wrong.


Compiler>>evaluate:in:to:notifying:ifFail:logged:

calculates the home class of the DoIt via this:

        | theClass |
        theClass := ((aContext == nil ifTrue: [receiver] ifFalse: [aContext receiver]) class).

that is, the _Receiver_ of the context, not the home class of the context's method.

@Bert, Eliot: Which one do you think would be correct? the Stack is down below[1].

Best
        -Tobias


[1]:

Compiler>>evaluateCue:ifFail:
        Receiver: a Compiler
        Arguments and temporary variables:
                aCue:   a CompilationCue
                failBlock:      [closure] in Compiler>>evaluateCue:ifFail:logged:
                methodNode:     DoItIn: ThisContext
        ^ super test
                method:         (MyClass>>#DoItIn: "a CompiledMethod(374)")
                value:  nil
        Receiver's instance variables:
                parser:         a Parser
                cue:    a CompilationCue

Compiler>>evaluateCue:ifFail:logged:
        Receiver: a Compiler
        Arguments and temporary variables:
                aCue:   a CompilationCue
                failBlock:      [closure] in [] in SmalltalkEditor(TextEditor)>>evaluateSelectionAnd...etc...
                logFlag:        true
                value:  nil
        Receiver's instance variables:
                parser:         a Parser
                cue:    a CompilationCue

Compiler>>evaluate:in:to:notifying:ifFail:logged:
        Receiver: a Compiler
        Arguments and temporary variables:
                textOrStream:   a ReadStream
                aContext:       MyClass(MyNewAbstraction)>>test
                receiver:       a MyClass
                aRequestor:     a SmalltalkEditor
                failBlock:      [closure] in [] in SmalltalkEditor(TextEditor)>>evaluateSelectionAnd...etc...
                logFlag:        true
                theClass:       MyClass
        Receiver's instance variables:
                parser:         a Parser
                cue:    a CompilationCue

[] in SmalltalkEditor(TextEditor)>>evaluateSelectionAndDo:
        Receiver: a SmalltalkEditor
        Arguments and temporary variables:
<<error during printing>
        Receiver's instance variables:
                morph:  a TextMorphForEditView(3464)
                selectionShowing:       false
                model:  a Debugger
                paragraph:      a NewParagraph
                markBlock:      a CharacterBlock with index 21 and character $s and rectangle 110@0 ...etc...
                pointBlock:     a CharacterBlock with index 31 and character $, and rectangle 174@0...etc...
                beginTypeInIndex:       nil
                emphasisHere:   {a TextColor code: (Color r: 0.0 g: 0.0 b: 0.5)}
                lastParenLocation:      nil
                otherInterval:  (20 to: 19)
                oldInterval:    (20 to: 19)
                typeAhead:      nil
                styler:         nil

BlockClosure>>on:do:
        Receiver: [closure] in SmalltalkEditor(TextEditor)>>evaluateSelectionAndDo:
        Arguments and temporary variables:
                exception:      OutOfScopeNotification
                handlerAction:  [closure] in SmalltalkEditor(TextEditor)>>evaluateSelectionAndDo...etc...
                handlerActive:  true
        Receiver's instance variables:
                outerContext:   SmalltalkEditor(TextEditor)>>evaluateSelectionAndDo:
                startpc:        97
                numArgs:        0

SmalltalkEditor(TextEditor)>>evaluateSelectionAndDo:
        Receiver: a SmalltalkEditor
        Arguments and temporary variables:
                aBlock:         [closure] in [] in PluggableTextMorphPlus(PluggableTextMorph)>>printIt
                result:         nil
                rcvr:   a MyClass
                ctxt:   MyClass(MyNewAbstraction)>>test
        Receiver's instance variables:
                morph:  a TextMorphForEditView(3464)
                selectionShowing:       false
                model:  a Debugger
                paragraph:      a NewParagraph
                markBlock:      a CharacterBlock with index 21 and character $s and rectangle 110@0 ...etc...
                pointBlock:     a CharacterBlock with index 31 and character $, and rectangle 174@0...etc...
                beginTypeInIndex:       nil
                emphasisHere:   {a TextColor code: (Color r: 0.0 g: 0.0 b: 0.5)}
                lastParenLocation:      nil
                otherInterval:  (20 to: 19)
                oldInterval:    (20 to: 19)
                typeAhead:      nil
                styler:         nil

[] in PluggableTextMorphPlus(PluggableTextMorph)>>printIt
        Receiver: a PluggableTextMorphPlus(473)
        Arguments and temporary variables:
                oldEditor:      {a SmalltalkEditor}
        Receiver's instance variables:
                bounds:         36@380 corner: 740@592
                owner:  a PluggablePanelMorph(3130)
                submorphs:      {a ScrollBar(1013) . a TransformMorph(3047)}
                fullBounds:     36@380 corner: 740@592
                color:  Color white
                extension:      a MorphExtension (3891) [other:  (layoutFrame -> a LayoutFrame) (vSc...etc...
                borderWidth:    1
                borderColor:    Color lightGray
                model:  a Debugger
                slotName:       nil
                open:   false
                scrollBar:      a ScrollBar(1013)
                scroller:       a TransformMorph(3047)
                retractableScrollBar:   false
                scrollBarOnLeft:        false
                getMenuSelector:        #codePaneMenu:shifted:
                getMenuTitleSelector:   nil
                scrollBarHidden:        nil
                hasFocus:       false
                hScrollBar:     a ScrollBar(2030)
                textMorph:      a TextMorphForEditView(3464)
                getTextSelector:        #contents
                setTextSelector:        #contents:notifying:
                getSelectionSelector:   #contentsSelection
                hasUnacceptedEdits:     false
                askBeforeDiscardingEdits:       true
                selectionInterval:      (21 to: 30)
                hasEditingConflicts:    false
                getColorSelector:       nil
                acceptAction:   nil
                unstyledAcceptText:     nil
                styler:         a SHTextStylerST80

TextMorphForEditView(TextMorph)>>handleEdit:
        Receiver: a TextMorphForEditView(3464)
        Arguments and temporary variables:
                editBlock:      [closure] in PluggableTextMorphPlus(PluggableTextMorph)>>printIt
                result:         nil
        Receiver's instance variables:
                bounds:         0@0 corner: 683@18
                owner:  a TransformMorph(3047)
                submorphs:      #()
                fullBounds:     0@0 corner: 683@18
                color:  Color black
                extension:      a MorphExtension (3814) [other:  (blinkStart -> 1091554)]
                borderWidth:    0
                borderColor:    Color black
                textStyle:      a TextStyle Bitmap DejaVu Sans 9
                text:   a Text for 'test  self halt.  ^ super test, ''my super call lands on myse...etc...
                wrapFlag:       true
                paragraph:      a NewParagraph
                editor:         a SmalltalkEditor
                container:      nil
                predecessor:    nil
                successor:      nil
                backgroundColor:        nil
                margins:        nil
                editHistory:    nil
                editView:       a PluggableTextMorphPlus(473)
                acceptOnCR:     false

PluggableTextMorphPlus(PluggableTextMorph)>>printIt
        Receiver: a PluggableTextMorphPlus(473)
        Arguments and temporary variables:
                oldEditor:      {a SmalltalkEditor}
        Receiver's instance variables:
                bounds:         36@380 corner: 740@592
                owner:  a PluggablePanelMorph(3130)
                submorphs:      {a ScrollBar(1013) . a TransformMorph(3047)}
                fullBounds:     36@380 corner: 740@592
                color:  Color white
                extension:      a MorphExtension (3891) [other:  (layoutFrame -> a LayoutFrame) (vSc...etc...
                borderWidth:    1
                borderColor:    Color lightGray
                model:  a Debugger
                slotName:       nil
                open:   false
                scrollBar:      a ScrollBar(1013)
                scroller:       a TransformMorph(3047)
                retractableScrollBar:   false
                scrollBarOnLeft:        false
                getMenuSelector:        #codePaneMenu:shifted:
                getMenuTitleSelector:   nil
                scrollBarHidden:        nil
                hasFocus:       false
                hScrollBar:     a ScrollBar(2030)
                textMorph:      a TextMorphForEditView(3464)
                getTextSelector:        #contents
                setTextSelector:        #contents:notifying:
                getSelectionSelector:   #contentsSelection
                hasUnacceptedEdits:     false
                askBeforeDiscardingEdits:       true
                selectionInterval:      (21 to: 30)
                hasEditingConflicts:    false
                getColorSelector:       nil
                acceptAction:   nil
                unstyledAcceptText:     nil
                styler:         a SHTextStylerST80

Debugger(StringHolder)>>perform:orSendTo:
        Receiver: a Debugger
        Arguments and temporary variables:
                selector:       #printIt
                otherTarget:    a PluggableTextMorphPlus(473)
        Receiver's instance variables:
                dependents:     a DependentsArray(a PluggableSystemWindow(1857) a PluggableListMorp...etc...
                contents:       a Text for 'test  self halt.  ^ super test, ''my super call lands on ...etc...
                currentCompiledMethod:  nil
                contentsSymbol:         #source
                multiWindowState:       nil
                interruptedProcess:     a Process in Debugger class>>morphicOpenOn:context:label:co...etc...
                interruptedController:  nil
                contextStack:   an OrderedCollection(MyClass(Object)>>halt MyClass(MyNewAbstracti...etc...
                contextStackIndex:      2
                contextStackList:       an OrderedCollection('MyClass(Object)>>halt' 'MyClass(MyNewAb...etc...
                receiverInspector:      an Inspector
                contextVariablesInspector:      a ContextVariablesInspector
                externalInterrupt:      false
                proceedValue:   nil
                selectingPC:    true
                savedCursor:    ((CursorWithMask
        extent: 16@16
        depth: 1
        fromArray: #(
                2r0
                2...etc...
                isolationHead:  nil
                failedProject:  nil
                errorWasInUIProcess:    true
                labelString:    nil
                message:        nil
                untilExpression:        nil

Debugger>>perform:orSendTo:
        Receiver: a Debugger
        Arguments and temporary variables:
                selector:       #printIt
                otherTarget:    a PluggableTextMorphPlus(473)
                result:         nil
        Receiver's instance variables:
                dependents:     a DependentsArray(a PluggableSystemWindow(1857) a PluggableListMorp...etc...
                contents:       a Text for 'test  self halt.  ^ super test, ''my super call lands on ...etc...
                currentCompiledMethod:  nil
                contentsSymbol:         #source
                multiWindowState:       nil
                interruptedProcess:     a Process in Debugger class>>morphicOpenOn:context:label:co...etc...
                interruptedController:  nil
                contextStack:   an OrderedCollection(MyClass(Object)>>halt MyClass(MyNewAbstracti...etc...
                contextStackIndex:      2
                contextStackList:       an OrderedCollection('MyClass(Object)>>halt' 'MyClass(MyNewAb...etc...
                receiverInspector:      an Inspector
                contextVariablesInspector:      a ContextVariablesInspector
                externalInterrupt:      false
                proceedValue:   nil
                selectingPC:    true
                savedCursor:    ((CursorWithMask
        extent: 16@16
        depth: 1
        fromArray: #(
                2r0
                2...etc...
                isolationHead:  nil
                failedProject:  nil
                errorWasInUIProcess:    true
                labelString:    nil
                message:        nil
                untilExpression:        nil

MenuItemMorph>>DoIt
        Receiver: a MenuItemMorph(77)'print it (p)'
        Arguments and temporary variables:

        Receiver's instance variables:
                bounds:         216@558 corner: 359@576
                owner:  a MenuMorph(2209)
                submorphs:      #()
                fullBounds:     216@558 corner: 359@576
                color:  Color black
                extension:      a MorphExtension (264) [other:  (layoutProperties -> a LayoutPropert...etc...
                font:   a StrikeFont(Bitmap DejaVu Sans 9 14)
                emphasis:       0
                contents:       'print it (p)'
                hasFocus:       false
                isEnabled:      true
                subMenu:        nil
                isSelected:     false
                target:         a Debugger
                selector:       #perform:orSendTo:
                arguments:      {#printIt . a PluggableTextMorphPlus(473)}
                icon:   Form(16x16x32)
                lastMousePosition:      nil

CompiledMethod>>valueWithReceiver:arguments:
        Receiver: (MenuItemMorph>>#DoIt "a CompiledMethod(1420)")
        Arguments and temporary variables:
                aReceiver:      a MenuItemMorph(77)'print it (p)'
                anArray:        #()
        Receiver's instance variables:
(MenuItemMorph>>#DoIt "a CompiledMethod(1420)")

[] in SmalltalkEditor(TextEditor)>>debug:receiver:in:
        Receiver: a SmalltalkEditor
        Arguments and temporary variables:
<<error during printing>
        Receiver's instance variables:
                morph:  a TextMorphForEditView(4064)
                selectionShowing:       false
                model:  an ObjectExplorer
                paragraph:      a NewParagraph
                markBlock:      a CharacterBlock with index 1 and character $s and rectangle 0@0 cor...etc...
                pointBlock:     a CharacterBlock with index 62 and rectangle 366@0 corner: 366@16
 ...etc...
                beginTypeInIndex:       nil
                emphasisHere:   {a TextFontChange font: 2}
                lastParenLocation:      nil
                otherInterval:  (61 to: 61)
                oldInterval:    (55 to: 54)
                typeAhead:      a WriteStream
                styler:         nil

[] in BlockClosure>>newProcess
        Receiver: [closure] in SmalltalkEditor(TextEditor)>>debug:receiver:in:
        Arguments and temporary variables:

        Receiver's instance variables:
                outerContext:   SmalltalkEditor(TextEditor)>>debug:receiver:in:
                startpc:        112
                numArgs:        0


--- The full stack ---
Compiler>>evaluateCue:ifFail:
Compiler>>evaluateCue:ifFail:logged:
Compiler>>evaluate:in:to:notifying:ifFail:logged:
[] in SmalltalkEditor(TextEditor)>>evaluateSelectionAndDo:
BlockClosure>>on:do:
SmalltalkEditor(TextEditor)>>evaluateSelectionAndDo:
[] in PluggableTextMorphPlus(PluggableTextMorph)>>printIt
TextMorphForEditView(TextMorph)>>handleEdit:
PluggableTextMorphPlus(PluggableTextMorph)>>printIt
Debugger(StringHolder)>>perform:orSendTo:
Debugger>>perform:orSendTo:
MenuItemMorph>>DoIt
CompiledMethod>>valueWithReceiver:arguments:
[] in SmalltalkEditor(TextEditor)>>debug:receiver:in:
[] in BlockClosure>>newProcess