[Vm-dev] (Squeak) Compiler bug?

[Florin Mateoc]

It's weirder than that.
I don't think Compiler-eem.483 itself introduces any bug, but the changes
it introduces are enough to make the bug appear.
Compile with SistaV1 bytecode set and full blocks in the stable 6.0 release
(which is prior to Compiler-eem.483) and decompilation works there as well


On Mon, Jan 9, 2023 at 7:53 PM Eliot Miranda <eliot.miranda at gmail.com>
wrote:

>
> BTW, it's not to do with Compiler-eem.483; it's to do with the SistaV1
> bytecode set and full blocks.  Compile with the old bytecode set and
> embedded blocks and decompilation works.
>
> On Mon, Jan 9, 2023 at 10:45 AM Eliot Miranda <eliot.miranda at gmail.com>
> wrote:
>
>> Hi Florin,
>>
>>     I've found the issue, which is an infinite loop in the Decompiler for
>> your undecompilable version.  Strangely enough it has nothing to do with
>> the code you modify. It has to do with the middle ifTrue: of the three at
>> the end of the final block:
>>
>>                    mm1 eventHandler
>>                         ifNotNil: [(morphs includesAllOf: mm1
>> eventHandler allRecipients)
>>                                 ifTrue: [mm1 eventHandler: nil]].
>>
>>
>> *mm1 isMorphicModel                        ifTrue: [mm1 model
>> isMorphicModel                                ifTrue: [mm1 model
>> breakDependents]].*
>>                     mm1 isTextMorph
>>                         ifTrue: [mm1 setContainer: nil]]].
>>
>> I can fix it for this one method, but not without breaking decompilation
>> of about 40 other methods.  So I need to understand it better.  Give me a
>> few days.  I've called on a higher power (the original author is Dan
>> himself). So hopefully we'll get this sorted very soon.
>>
>> On Sun, Jan 8, 2023 at 7:01 PM Florin Mateoc <florin.mateoc at gmail.com>
>> wrote:
>>
>>>
>>> Hi,
>>>
>>> Happy New Year everybody!
>>>
>>> I hope you will forgive my transgression, I know this is not about the
>>> VM, it is about the bytecode compiler, but I am only subscribed to this
>>> list, and the Squeak compiler is somewhere in between.
>>>
>>> I have recently stumbled upon a regression introduced by Compiler-eem.483
>>> One of my generated (transformed) methods is apparently valid Smalltalk
>>> - it can still be compiled - but it cannot be decompiled anymore. I am not
>>> sure if this is a compiler bug, or a latent decompiler bug exposed by the
>>> changes in Compiler-eem.483
>>>
>>> My method is below, it is a transformed variant of
>>> NativeImageSegment>>findRogueRootsPrep
>>>
>>> The bug is somehow caused by the literal #Marker. I have started at the
>>> bytecodes and they look ok to me, but the decompiler enters an (apparently
>>> unrelated) infinite loop. It is also not just about the literal itself or
>>> the immediate surrounding code, the method needs to be big/complex enough
>>> (over a certain number of literals?) to trigger the bug.
>>>
>>>
>>> findRogueRootsPrep1
>>> "Part of the tool to track down unwanted pointers into the segment.
>>> Break all owner pointers in submorphs, scripts, and viewers in flaps."
>>> | wld players morphs |
>>> wld := arrayOfRoots detect: [:obj | obj isMorph and: [obj isWorldMorph]]
>>> ifNone: [].
>>> wld == nil ifTrue: [
>>>   (wld := arrayOfRoots
>>>     detect: [:obj1 | obj1 isMorph]
>>>     ifNone: [#Marker]
>>>   ) == #Marker ifTrue: [
>>>     ^ self error: 'can''t find a root morph']].
>>> morphs := IdentitySet new: 400.
>>> wld allMorphsAndBookPagesInto: morphs.
>>> players := wld presenter allExtantPlayers. "just the cached list"
>>> players do: [:pp | | scriptEditors |
>>>   scriptEditors := pp class tileScriptNames collect: [:nn | pp
>>> scriptEditorFor: nn].
>>>   scriptEditors do: [:se | morphs addAll: se allMorphs]].
>>> wld submorphs do: [:mm | "non showing flaps"
>>>   (mm isKindOf: FlapTab) ifTrue: [
>>>     mm referent allMorphsAndBookPagesInto: morphs]].
>>> morphs do: [:mm1 | "break the back pointers"
>>>   mm1 isInMemory ifTrue: [
>>>     (mm1 respondsTo: #target) ifTrue: [
>>>       mm1 nearestOwnerThat: [:ow | | zzzTemp |
>>>         ow == mm1 target ifTrue: [
>>>           mm1 target: nil.
>>>           zzzTemp := true
>>>         ] ifFalse: [
>>>           zzzTemp := false].
>>>         zzzTemp]].
>>>     (mm1 respondsTo: #arguments) ifTrue: [
>>>       mm1 arguments do: [:arg |
>>>         arg == nil ifFalse: [
>>>           mm1 nearestOwnerThat: [:ow1 | | zzzTemp1 |
>>>             ow1 == arg ifTrue: [
>>>               mm1 arguments at: (mm1 arguments indexOf: arg) put: nil.
>>>               zzzTemp1 := true
>>>             ] ifFalse: [
>>>               zzzTemp1 := false].
>>>             zzzTemp1]]]].
>>>     mm1 eventHandler == nil ifFalse: ["recipients point back up"
>>>       (morphs includesAllOf: mm1 eventHandler allRecipients) ifTrue: [
>>>         mm1 eventHandler: nil]].
>>>     "temporary, until using Model for PartsBin"
>>>     mm1 isMorphicModel ifTrue: [
>>>       mm1 model isMorphicModel ifTrue: [
>>>         mm1 model breakDependents]].
>>>     mm1 isTextMorph ifTrue: [
>>>       mm1 setContainer: nil]]].
>>> (Smalltalk includesKey: #Owners) ifTrue: [
>>>   Smalltalk at: #Owners put: nil].
>>> "in case findOwnerMap: is commented out"
>>> "self findOwnerMap: morphs."
>>> morphs do: [:mm2 | "break the back pointers"
>>>   mm2 isInMemory ifTrue: [
>>>     mm2 privateOwner: nil]]
>>>
>>>
>>> Florin
>>>
>>
>>
>> --
>> _,,,^..^,,,_
>> best, Eliot
>>
>
>
> --
> _,,,^..^,,,_
> best, Eliot
>
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