[Vm-dev] latest changes (no idea from when it started) are making FFI win32 crash (and FFI Callbacks are not reliable anymore either)

[Esteban Lorenzano]

> On 29 Nov 2016, at 13:04, Clément Bera <bera.clement at gmail.com> wrote:
> 
> Hi,
> 
> Can you confirm this bug happen only in Windows ?

yes, the crash is just in windows.
the callback problem is general (note that FFICallbackTests works fine, but I think this is related to the fact that it never enters the 2nd condition with the qsort function) .

> 
> Do you have version number (both VMMaker and git commit) of the last version you have that was working ?

sadly, not… I tried to get the latest working version, but with the mess I have to get the VM to build with opensmalltalk-vm, I couldn’t track it. 
I suspect is related to the work on 64bits for windows, but I have no proof of that :P

Esteban

> 
> Thanks.
> 
> 
> On Tue, Nov 29, 2016 at 11:54 AM, Esteban Lorenzano <estebanlm at gmail.com <mailto:estebanlm at gmail.com>> wrote:
> 
> Hi,
> 
> So, I’m building the PharoVM along with all his dependencies. For me, this is a major step because I can drop the old build process finally.
> Now, I’m having serious problems with FFI (that they were not present before), :
> 
> 
> 1. CRASH IN WINDOWS (32bits):
> 
> In Win32, it crashes automatically when trying to access this funtion:
> 
> getEnvSize: nameString
>         ^ self ffiCall: #( int GetEnvironmentVariableA ( String nameString, nil, 0 ) ) module: #Kernel32
> 
>  (this works perfectly fine in older versions)
> 
> 2. CALLBACKS FAILING:
> 
> Callbacks have problems. The examples passes but they are very simple… as soon as I try to do something complicates (like unqlite bindings or libgit2 bindings, who use callbacks intensively), callbacks stops working.
> I traced the problem up to this method:
> 
> StackInterpreter>>#returnAs:ThroughCallback:Context:
> 
> returnAs: returnTypeOop ThroughCallback: vmCallbackContext Context: callbackMethodContext
>         "callbackMethodContext is an activation of invokeCallback:[stack:registers:jmpbuf:].
>          Its sender is the VM's state prior to the callback.  Reestablish that state (via longjmp),
>          and mark callbackMethodContext as dead."
>         <export: true>
>         <var: #vmCallbackContext type: #'VMCallbackContext *'>
>         | calloutMethodContext theFP thePage |
>         <var: #theFP type: #'char *'>
>         <var: #thePage type: #'StackPage *'>
>         ((self isIntegerObject: returnTypeOop)
>          and: [self isLiveContext: callbackMethodContext]) ifFalse:
>                 [^false].
>         calloutMethodContext := self externalInstVar: SenderIndex ofContext: callbackMethodContext.
>         (self isLiveContext: calloutMethodContext) ifFalse:
>                 [^false].
>         "We're about to leave this stack page; must save the current frame's instructionPointer."
>         self push: instructionPointer.
>         self externalWriteBackHeadFramePointers.
>         "Mark callbackMethodContext as dead; the common case is that it is the current frame.
>          We go the extra mile for the debugger."
>         (self isSingleContext: callbackMethodContext)
>                 ifTrue: [self markContextAsDead: callbackMethodContext]
>                 ifFalse:
>                         [theFP := self frameOfMarriedContext: callbackMethodContext.
>                          framePointer = theFP "common case"
>                                 ifTrue:
>                                         [(self isBaseFrame: theFP)
>                                                 ifTrue: [stackPages freeStackPage: stackPage]
>                                                 ifFalse: "calloutMethodContext is immediately below on the same page.  Make it current."
>                                                         [instructionPointer := (self frameCallerSavedIP: framePointer) asUnsignedInteger.
>                                                          stackPointer := framePointer + (self frameStackedReceiverOffset: framePointer) + objectMemory wordSize.
>                                                          framePointer := self frameCallerFP: framePointer.
>                                                          self setMethod: (self frameMethodObject: framePointer).
>                                                          self restoreCStackStateForCallbackContext: vmCallbackContext.
>                                                          "N.B. siglongjmp is defines as _longjmp on non-win32 platforms.
>                                                           This matches the use of _setjmp in ia32abicc.c."
>                                                          self siglong: vmCallbackContext trampoline jmp: (self integerValueOf: returnTypeOop).
>                                                          ^true]]
>                                 ifFalse:
>                                         [self externalDivorceFrame: theFP andContext: callbackMethodContext.
>                                          self markContextAsDead: callbackMethodContext]].
>         "Make the calloutMethodContext the active frame.  The case where calloutMethodContext
>          is immediately below callbackMethodContext on the same page is handled above."
>         (self isStillMarriedContext: calloutMethodContext)
>                 ifTrue:
>                         [theFP := self frameOfMarriedContext: calloutMethodContext.
>                          thePage := stackPages stackPageFor: theFP.
>                          "findSPOf:on: points to the word beneath the instructionPointer, but
>                           there is no instructionPointer on the top frame of the current page."
>                          self assert: thePage ~= stackPage.
>                          stackPointer := (self findSPOf: theFP on: thePage) - objectMemory wordSize.
>                          framePointer := theFP]
>                 ifFalse:
>                         [thePage := self makeBaseFrameFor: calloutMethodContext.
>                          framePointer := thePage headFP.
>                          stackPointer := thePage headSP].
>         instructionPointer := self popStack.
>         self setMethod: (objectMemory fetchPointer: MethodIndex ofObject: calloutMethodContext).
>         self setStackPageAndLimit: thePage.
>         self restoreCStackStateForCallbackContext: vmCallbackContext.
>          "N.B. siglongjmp is defines as _longjmp on non-win32 platforms.
>           This matches the use of _setjmp in ia32abicc.c."
>         self siglong: vmCallbackContext trampoline jmp: (self integerValueOf: returnTypeOop).
>         "NOTREACHED"
>         ^true
> 
> with the first siglongjmp callbacks are passing fine.
> with the last (it would be if  framePointer = theFP AND !(isBaseFrame: theFP) ) it doesn’t.
> 
> So… from here I’m a bit lost… I need some help :)
> 
> thanks,
> Esteban
> 
> 
> 
> 

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