[Vm-dev] Re: SmallInetger as methods was not ready yet....now maybe?

[Mariano Martinez Peck]

On Fri, Dec 3, 2010 at 6:42 PM, Igor Stasenko <siguctua at gmail.com> wrote:

>
> On 3 December 2010 16:58, Mariano Martinez Peck <marianopeck at gmail.com>
> wrote:
> >
> >
> >
> > On Fri, Dec 3, 2010 at 3:41 PM, Mariano Martinez Peck <
> marianopeck at gmail.com> wrote:
> >>
> >> Hi folks. After fighting and fighting about crashes using SmallInteger
> as methods, I finally could debug the VM (thanks Esteban for the help in
> compiling and debugging!!) and I think I found a problem in theGC.
> >> In the mark phase of the GC, it tries to mark all interpreter oops in
> the method:  markAndTraceInterpreterOops
> >>
> >> If you see that method....it does this (a part of it):
> >>
> >> compilerInitialized
> >>         ifTrue: [self markAndTrace: receiver.
> >>             self markAndTrace: method]
> >>         ifFalse: [self markAndTrace: activeContext].
> >>     self markAndTrace: messageSelector.
> >>     self markAndTrace: newMethod.
> >>
> >> If you are using SmallInteger as methods.....newMethod can be a
> SmallIneteger, and not a method....so if we then see the method
> markAndTrace:
> >>
> >> the first lines are:
> >>
> >>     | header lastFieldOffset action statMarkCountLocal |
> >>     header := self longAt: oop.
> >>
> >>
> >> And of course, it crash in that #longAt:
> >>
> >> :)
> >>
> >> So, solutions:
> >>
> >> 1) Put an if in each place where it uses newMethod or method or
> newNativeMethod or suspendedMethods  or whatever
> >> 2) Put an if in #markAndSweep.
> >>
> >> I think 2) is easier and it is just adding one line of code at the
> beginning:
> >>
> >>     | header lastFieldOffset action statMarkCountLocal |
> >>     (self isIntegerObject: oop) ifTrue: [ ^ 0 ].
> >>     header := self longAt: oop.
> >> ....
> >>
> >> what do you think ?
> >>
> >>
> >> Finally, I am afraid that there are more places where Interpreter uses
> any of those instVar that represent methods, and treat them as real objects.
> >> So maybe there still pending future possible crashes?
> >>
> >
> >
> > For example, take a look to the methods:
> >
> > printUnbalancedStackFromNamedPrimitive
> > primitiveMethod
> > internalJustActivateNewMethod
> > internalActivateNewMethod
> > activateNewMethod
> >
> > And all the senders of
> >
> > literal: offset ofMethod: methodPointer
> > literalCountOf: methodPointer
> > primitiveIndexOf:
> >
> no, but these  methods usually should be fired only after you already
> determined that given oop is a compiled method,
> not a smallinteger or something else.
>
>
But they do not. Let's take an example: literal: offset ofMethod:
methodPointer
sender: methodClassOf: methodPointer
sender: superclassSend
sender: doubleExtendedDoAnythingBytecode and singleExtendedSuperBytecode

did I miss something?





> > maybe supporting SmallInteger as methods was not a good idea :(
> >
> it should work.
>
> > cheers
> >
> > mariano
> >
> >
> >>
> >> Thanks
> >>
> >> Mariano
> >
> >
> >
>
>
>
> --
> Best regards,
> Igor Stasenko AKA sig.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.squeakfoundation.org/pipermail/vm-dev/attachments/20101203/c278e5b4/attachment.htm