[Vm-dev] Request for review of VMMaker-dtl.262.mcz

[Stefan Marr]

Hi Dave:

Ok, I tell you that there might be an edge case in your code, and you are renaming the helper? ;)

On 05 Jan 2012, at 14:51, David T. Lewis wrote:

>> Item was changed:
>>  ----- Method: Interpreter>>primitivePerformInSuperclass (in category 'control primitives') -----
>>  primitivePerformInSuperclass
>>  	| lookupClass rcvr currentClass |
>>  	lookupClass := self stackTop.
>> + 	rcvr := self stackValue: 3.
>> - 	rcvr := self stackValue: argumentCount.
>>  	currentClass := self fetchClassOf: rcvr.
>>  	[currentClass ~= lookupClass]
>>  		whileTrue:
>>  		[currentClass := self superclassOf: currentClass.
>>  		currentClass = nilObj ifTrue: [^ self primitiveFail]].
>> 
>> + 	argumentCount = 3
>> + 		ifTrue: ["normal primitive call with 3 arguments expected on the stack"
>> + 			self popStack.
>> + 			self primitivePerformAt: lookupClass.
>> + 			self successful ifFalse:
>> + 				[self push: lookupClass]]

This looks correct, that is just the old code I assume.




>> + 		ifFalse: ["mirror primitive call with extra argument specifying object to serve as receiver"
>> + 			| s1 s2 s3 s4 s5 |
>> + 			"save stack contents"
>> + 			s1 := self popStack. "lookupClass"
>> + 			s2 := self popStack. "args"
>> + 			s3 := self popStack. "selector"
>> + 			s4 := self popStack. "mirror receiver"
>> + 			s5 := self popStack. "actual receiver"

Could it be that if somebody like me, calls the primitive without understanding it, that there are less than 3 items on the stack? What would happen then?
You restore the stack on failure, but I guess the at least the stack pointer could be wrong after the restore.

Best regards
Stefan

-- 
Stefan Marr
Software Languages Lab
Vrije Universiteit Brussel
Pleinlaan 2 / B-1050 Brussels / Belgium
http://soft.vub.ac.be/~smarr
Phone: +32 2 629 2974
Fax:   +32 2 629 3525