[Vm-dev] Cog and #commonSend are getting me crazy :(

Mariano Martinez Peck marianopeck at gmail.com
Thu Apr 28 12:26:19 UTC 2011

Hi Eliot. I am fighting since several hours with something in Cog and I
cannot realize it. I am blind.

I need to intercept all messages sent to an object. I have already done this
for Interpreter VM and for StackVM. Now,  I am trying latest CogMTVM, and
there is something I am not sying...I have this test:


    ClassWith1Var new fooLong.
    ClassWith1Var new fooLong.
    ClassWith1Var new fooLong.

ClassWith1Var >> fooLong
    | aaa |
    Object new.
    self foo.

Now, I modified

CoInterpreter >> commonSend
    "Send a message, starting lookup with the receiver's class."
    "Assume: messageSelector and argumentCount have been set, and that
    the receiver and arguments have been pushed onto the stack,"
    "Note: This method is inlined into the interpreter dispatch loop."
    <sharedCodeNamed: 'commonSend' inCase: 131>
    self sendBreak: messageSelector + BaseHeaderSize
        point: (objectMemory lengthOf: messageSelector)
        receiver: (self internalStackValue: argumentCount).
    cogit recordSendTrace ifTrue:
        [self recordTrace: lkupClass thing: messageSelector source:
    self internalFindNewMethod.
    self print: 'called: '; printStringOf: messageSelector; cr.
    self internalExecuteNewMethod.
    self fetchNextBytecode

And when running the VM from gdb, 'called: fooLong'  doesn't appear at
all!!!  why ?
In addition, it appears 'called: foo' which is correct because #fooLong
sends #foo
but it appears only ONCE.

#fooLong as I can see is not a quick return method but instead it goes by
#sendLiteralSelector0ArgsBytecode. But the same happens if I put the print
in that method... (which makes sense).
I tried with a StackVM and the same....so it seems that #fooLong is going by
another place than #commonSend.

As far as I understand, there is nothing related with PIC or Jitt. In any of
those cases, as what I can see, the #commonSend is called anyways.

So...I am completly lost.

Thanks in advance for any help.

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