[Vm-dev] positive32BitValueOf: fail with LargePositiveInteger

[Nicolas Cellier]

2010/10/8 Mariano Martinez Peck <marianopeck at gmail.com>:
>
> Hi. I am trying to call #primitiveBitOr which inside calls #popPos32BitInteger which calls  #positive32BitValueOf , with two LargePositiveInteger. Example:
>
> 9999999999 bitOr: 8888888888.
>
> Now, this seems to fail since the #bitOr: of LargePositiveInteger is failing, and thus, super (Integer) is being used. Now, I don't understand why it fails.
>
> If I read the comment of positive32BitValueOf it says "Convert the given object into an integer value.
>     The object may be either a positive ST integer or a four-byte LargePositiveInteger."
>
> Its code is:
>
> positive32BitValueOf: oop
>     "Convert the given object into an integer value.
>     The object may be either a positive ST integer or a four-byte LargePositiveInteger."
>
>     | sz value |
>     (self isIntegerObject: oop) ifTrue: [
>         value := self integerValueOf: oop.
>         value < 0 ifTrue: [^ self primitiveFail].
>         ^ value].
>
>     self assertClassOf: oop is: (self splObj: ClassLargePositiveInteger).
>     successFlag ifTrue: [
>         sz := self lengthOf: oop.
>         sz = 4 ifFalse: [^ self primitiveFail]].
>     successFlag ifTrue: [
>         ^ (self fetchByte: 0 ofObject: oop) +
>           ((self fetchByte: 1 ofObject: oop) <<  8) +
>           ((self fetchByte: 2 ofObject: oop) << 16) +
>           ((self fetchByte: 3 ofObject: oop) << 24) ].
>
>
>
> as you can see, I am supposed to use ClassLargePositiveInteger.
>
> But, in addition, LargePositiveInteger >> #bitOr comment says: "Primitive. Answer an Integer whose bits are the logical OR of the
>     receiver's bits and those of the argument. Fail if the receiver or argument
>     is greater than 32 bits. See Object documentation whatIsAPrimitive."
>
> So....I don't understand...how can I have a LargePositiveInteger but that is less than 32 bits?  Wouldn't that  be a SmallInteger?
>

If you don't want to read the blue book, maybe you should try this:

^SmallInteger maxVal highBit

Then observe how the low bits of an oop are used to distinguish a true
object pointer from an immediate SmallInteger value in the VM.

Nicolas


> I put some printf in the VM and seems that with my numbers (9999999999 and 8888888888.)  when I sent positive32BitValueOf:    I got : -65536 and 65535
>
> Thanks in advance for any help.
>
> Mariano
>
>
>