[Pkg] The Trunk: Tools-eem.633.mcz

commits at source.squeak.org commits at source.squeak.org
Thu Sep 17 20:18:29 UTC 2015

Eliot Miranda uploaded a new version of Tools to project The Trunk:

==================== Summary ====================

Name: Tools-eem.633
Author: eem
Time: 17 September 2015, 1:18:07.129 pm
UUID: 2a5a8395-fa44-4d48-b6ed-a920c18dbc02
Ancestors: Tools-mt.632

Fix hard VM crash when defining quick methods from MNUs in the debugger.  The bug is that the sender context (Message>>sentTo:) is doing a perform:withArguments:[inSuperclass:] but the receiver and arguments have already been removed from the context, so simply backing up to the point of send and proceeding will have disastrous consequences; there must be a receiver and arguments on the stack.  So if the arguments are unavailable we simply restart the context inmstead of backing up to the point of send.

To reproduce:
0. make sure e.g. Object>>#zork is unimplemented
1. evaluate "nil zork"
2. in the debugger examine the doesNotUnderstand: context and then hit proceed.
3. click the Create button and define 
4. (the debugger sets the active context to Message>>sentTo:) hit proceed

Before the VM woudl crash.  Now the debugger sets the pc to the start of the Message>>sentTo: method.

=============== Diff against Tools-mt.632 ===============

Item was changed:
  ----- Method: Debugger>>contents:notifying: (in category 'accessing') -----
  contents: aText notifying: aController
  	"The retrieved information has changed and its source must now be updated.
  	 In this case, the retrieved information is the method of the selected context."
  	| result selector classOfMethod category h ctxt newMethod |
  	contextStackIndex = 0 ifTrue:
  	self selectedContext isExecutingBlock ifTrue:
  		[h := self selectedContext activeHome.
  		 h ifNil:
  			[self inform: 'Method for block not found on stack, can''t edit and continue'.
  		 (self confirm: 'I will have to revert to the method from\which this block originated.  Is that OK?' withCRs) ifFalse:
  		self resetContext: h changeContents: false.
  		"N.B. Only reset the contents if the compilation succeeds.  If contents are reset
  		 when compilation fails both compiler error message and modifications are lost."
  		(result := self contents: aText notifying: aController) ifTrue:
  			[self contentsChanged].
  	classOfMethod := self selectedClass.
  	category := self selectedMessageCategoryName.
  	selector := self selectedClass newParser parseSelector: aText.
  	(selector == self selectedMessageName
  	 or: [(self selectedMessageName beginsWith: 'DoIt')
  		and: [selector numArgs = self selectedMessageName numArgs]]) ifFalse:
  		[self inform: 'can''t change selector'.
  	selector := classOfMethod
  				compile: aText
  				classified: category
  				notifying: aController.
  	selector ifNil: [^false]. "compile cancelled"
  	contents := aText.
  	newMethod := classOfMethod compiledMethodAt: selector.
  	newMethod isQuick ifTrue:
+ 		[self cutBackExecutionToSenderContext].
- 		[self down.
- 		 self selectedContext jump: (self selectedContext previousPc - self selectedContext pc)].
  	ctxt := interruptedProcess popTo: self selectedContext.
  	ctxt == self selectedContext
  			[self inform: 'Method saved, but current context unchanged\because of unwind error. Click OK to see error' withCRs]
  			[newMethod isQuick ifFalse:
  					restartTopWith: newMethod;
  			contextVariablesInspector object: nil].
  	self resetContext: ctxt.
  	Smalltalk isMorphic ifTrue:
  			addAlarm: #changed:
  			withArguments: #(contentsSelection)
  			for: self
  			at: (Time millisecondClockValue + 200)].

Item was added:
+ ----- Method: Debugger>>cutBackExecutionToSenderContext (in category 'private') -----
+ cutBackExecutionToSenderContext
+ 	"When accepting a new version of a method which can't be simulated (i.e. a quick method) we
+ 	 must cut back to the sender.  But this is non-trivial. If the quick method has been reached via
+ 	 a perform: (as it is when one uses Create toi implement a method from an MNU) then the relevant
+ 	 arguments won't be on the stack and we can't simply proceed without crashing the VM."
+ 	| oldContext context sel |
+ 	oldContext := self selectedContext.
+ 	self down.
+ 	context := self selectedContext.
+ 	context jump: (context previousPc - context pc).
+ 	sel := context selectorToSendOrSelf.
+ 	sel numArgs = oldContext method numArgs
+ 		ifTrue:
+ 			[context push: oldContext receiver.
+ 			 oldContext arguments do:
+ 				[:arg| context push: arg]]
+ 		ifFalse:
+ 			[context privRefresh; stepToSendOrReturn]!

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