[squeakdev] Re: Bug with valueWithReceiver:arguments:
Andreas Raab
andreas.raab at gmx.de
Sun Oct 26 12:39:04 UTC 2008
Hi Frederic 
Congrats! You found the first real VM bug in five years or so ;) I'm
not completely sure what the problem is but there is obviously something
wrong here. It's easiest to recreate the problem by copying the #/
method and simply do something like:
SmallInteger>>foo: aNumber
"(SmallInteger>>#foo:) valueWithReceiver: 11 arguments: {2}"
<primitive: 10>
self halt.
aNumber isZero ifTrue: [^(ZeroDivide dividend: self) signal].
(aNumber isMemberOf: SmallInteger)
ifTrue: [^(Fraction numerator: self denominator: aNumber) reduced]
ifFalse: [^super / aNumber]
When you run this, you'll see that the debugger shows *two* frames with
SmallInteger>>foo: on them. Inspecting the "parent" frame will
eventually crash the system since it has a completely bogus stack
pointer (1).
It seems that in a failing primitive method we end up with a bogus
activation record in primitiveExecMethodWithArgs (removing the primitive
from the above makes it work fine). I'm somewhat at a loss here as to
what the problem might be given that the implementations of
primPerformWithArgs and primExecWithArgs are so similar but
interestingly, the equivalent:
11 perform: #foo: withArguments:{2}.
works fine with or without the primitive. Somewhere there must be a
difference ...
Cheers,
 Andreas
Frederic Pluquet wrote:
> Hello,
>
> I found a fondamental bug in Squeak and Pharo. The next code
>
> 11 / 2
>
> gives the fraction (11/2). It's correct. But the next code
>
> (SmallInteger>>#/) valueWithReceiver: 11 arguments: {2}
>
> gives 1 !
>
> The problem is the method valueWithReceiver:arguements: is used hugely
> with method wrappers...
>
> After long time of debugging, I found a point to debug: this method
> don't have the good behavior with compiled methods having a primitive
> that fails and executes some code after (as in SmallInteger>>#/ method
> when the division don't give a whole integer). In fact, when I send this
> message, the vm executes normally the compiled method but, in place of
> returns simply the good result, seems to rerun the the compiled method
> with other arguments (completly wrong) and returns so a wrong result.
>
> For example,
> (SmallInteger>>#/) valueWithReceiver: 11 arguments: {2}
>
> has the following execution trace :
>
> 2 isZero
>  2 = 0
>  returns: false
> returns: false
> 2 isMemberOf: SmallInteger
>  2 class
>  returns: SmallInteger
>  SmallInteger == SmallInteger
>  returns: true
> returns: true
> Fraction numerator: 101 denominator: 2
>  Fraction new
>   Fraction basicNew
>   returns: a Fraction instance
>   (a Fraction instance) initialize
>   returns: a Fraction instance
>  returns: a Fraction instance
>  a Fraction instance setNumerator: 101 denominator: 2
>   2 = 0
>   returns: false
>   101 asInteger
>   returns: 101
>   2 asInteger
>   returns: 2
>   2 abs
>    2 < 0
>    returns: false
>   returns: 2
>   2 < 0
>   returns: false
>  returns: (101/2)
> returns: (101/2)
> (101/2) reduced
>  101 = 0
>  returns: false
>  101 gcd: 2
>   101 = 0
>   returns: false
>   2 \\ 101
>   returns: 2
>   2 = 0
>   returns: false
>   101 \\ 2
>   returns: 1
>   1 = 0
>   returns: false
>   2 \\ 1
>   returns: 0
>   0 = 0
>   returns: true
>   1 abs
>    1 < 0
>    returns: false
>   returns: 1
>  returns: 1
>  101 // 1
>  returns: 101
>  2 // 1
>  returns: 2
>  2 = 1
>  returns: false
>  Fraction numerator: 101 denominator: 2
>   Fraction new
>    Fraction basicNew
>    returns: a Fraction instance
>    (a Fraction instance) initialize
>    returns: a Fraction instance
>   returns: a Fraction instance
>   (a Fraction instance) setNumerator: 101 denominator: 2
>    2 = 0
>    returns: false
>    101 asInteger
>    returns: 101
>    2 asInteger
>    returns: 2
>    2 abs
>     2 < 0
>     returns: false
>    returns: 2
>    2 < 0
>    returns: false
>   returns: (101/2)
>  returns: (101/2)
> returns: (101/2)
> 2 isZero
>  2 = 0
>  returns: false
> returns: false
> false isMemberOf: SmallInteger
>  false class
>  returns: False
>  False == SmallInteger
>  returns: false
> returns: false
>
>
> Please help me to fix this bug. I really need it works fine !
>
> Fréd
> 
> Frédéric Pluquet
> Université Libre de Bruxelles (ULB)
> Assistant
> http://www.ulb.ac.be/di/fpluquet
>
>
> 
>
>
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