[Vm-dev] Re: [Vm-beginners] how can I check which selector is the VM executing?

[Mariano Martinez Peck]

On Sat, Apr 30, 2011 at 4:23 AM, Yoshiki Ohshima <yoshiki at vpri.org> wrote:

>
> At Thu, 28 Apr 2011 12:22:33 +0200,
> Mariano Martinez Peck wrote:
> >
> > Hi. Suppose I am doing something in #commonSend:
> >
> > 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 internalFindNewMethod.
> > self internalExecuteNewMethod.
> > self fetchNextBytecode
> >
> > and somewhere there I want to do something like this:
> >
> > (messageSelector = '#foo') ifTrue: [ self print: 'the message foo was
> called'; cr ].
> >
> > messageSelector is the instVar of Interpreter and it is already in the
> stack.
> >
> > Of course, the part that doesn't work is (messageSelector = '#foo')
> > I tried several things but I don't find how to do it.
>
>   Perhaps something along the line of:
>
>  (self cCode: 'stSizeOf(messageSelector) == sizeOf('foo') &&
> (strncmp(firstIndexableField(messageSelector), 'foo',
>     sizeOf('foo')) == 0)) ifTrue: [self print: 'the message foo was
> called': cr].
>
>  (Not tested this particualr one, but have done similar thing
> before.  This assumes that messageSelector is always a Symbol, which
> may not be the case for you...)
>
>
Thanks Yoshiki. After I sent this mail, and with a help of a friend, I was
also trying to do something similar to that. Just by coincidense, Eliot
answered me in another thread, a way to solve this in Cog, and it is using
the command line argument -breaksel.  With such parameter you can send a
seletor as an argument, put a breakpoint with gdb, and the VM will stop in a
place. It is not EXACTLY the same as what I was asking, but it is useful.

If you are interested, read his answer here:
http://forum.world.st/Cog-and-commonSend-are-getting-me-crazy-td3480836.html

And yes, his code is similar to yours:

CoInterpreter >>  compilationBreak: selectorOop point: selectorLength
    <api>
    <cmacro: '(sel, len) do { \
    if ((len) == breakSelectorLength \
     && !strncmp((char *)((sel) + BaseHeaderSize), breakSelector,
breakSelectorLength)) { \
        suppressHeartbeatFlag = 1; \
        compilationBreakpointFor(sel); \
    } \
} while (0)'>
    | i |
    breakSelectorLength = selectorLength ifTrue:
        [i := breakSelectorLength.
         [i > 0] whileTrue:
            [(self byteAt: selectorOop + i + BaseHeaderSize - 1) =
(breakSelector at: i) asInteger
                ifTrue: [(i := i - 1) = 0 ifTrue:
                            [self compilationBreakpointFor: selectorOop]]
                ifFalse: [i := 0]]]


Once again, thanks for your help.

-- 
Mariano
http://marianopeck.wordpress.com
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