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

Thu Apr 28 21:59:00 UTC 2011

Hi Eliot. Thanks for answering. Your answer was EXTREMELY useful. Not only
because it helped me to solve the problem I was having, but also because I
discovered a wonderful tool.

You are smart :)  I like the solution. So, if I understood correctly, I can
put a breakpoint in the function warning() with "break warning". With the
-breaksel  parameter you set an instVar with the selector name and size.
Then after, anywhere I can send  #compilationBreak: selectorOop point:
selectorLength   and that will magically check whether the selectorOop is
the one I passes with -breaksel and if true, it will call warning, who has a
breakpoint, hence, I can debug :)   AWESOME!!!!   Now with CMake I can even
generate a xcode project and debug it :)  (I don't know why attaching gdb
from Xcode crash the vm).

One little comment....I have an error using Cocoa VM builds because
sqMacUnixCommandLineInterface.c  is only for /platforms/MacOS   and not for
/platforms/IOS/
I am not sure how this should be integrated in Cocoa branch.

Thanks Eliot, I like having a kind of #haltIf: in the vm :)

Mariano

On Thu, Apr 28, 2011 at 7:00 PM, Eliot Miranda <eliot.miranda at gmail.com>wrote:

>
> Mariano,
>
>     here's a hint.  Look at the command-line argument breaksel and see
> where it is used.  This will call warning whenever a specific message is
> sent.  e.g.
>
> McStalker.macbuild$ gdb Debug.app/
> GNU gdb 6.3.50-20050815 (Apple version gdb-1515) (Sat Jan 15 08:33:48 UTC
> 2011)
> Copyright 2004 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you
> are
> welcome to change it and/or distribute copies of it under certain
> conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for details.
> This GDB was configured as "x86_64-apple-darwin"...Reading symbols for
> shared libraries ................ done
>
> (gdb) break warning
> Breakpoint 1 at 0x105e2b: file
> /Users/eliot/Cog/oscogvm/macbuild/../src/vm/gcc3x-cointerp.c, line 39.
> (gdb) run -breaksel initialize ~/Squeak/Squeak4.2/trunk4.2.image
> Starting program:
> /Users/eliot/Cog/oscogvm/macbuild/Debug.app/Contents/MacOS/Croquet -breaksel
> initialize ~/Squeak/Squeak4.2/trunk4.2.image
> Reading symbols for shared libraries
> .+++++++++++++++.....................................................................................
> done
> Reading symbols for shared libraries . done
>
> Breakpoint 1, warning (s=0x16487c "send breakpoint (heartbeat suppressed)")
> at /Users/eliot/Cog/oscogvm/macbuild/../src/vm/gcc3x-cointerp.c:39
> 39              printf("\n%s\n", s);
>  (gdb) where 5
> #0  warning (s=0x16487c "send breakpoint (heartbeat suppressed)") at
> /Users/eliot/Cog/oscogvm/macbuild/../src/vm/gcc3x-cointerp.c:39
> #1  0x0010b490 in interpret () at
> /Users/eliot/Cog/oscogvm/macbuild/../src/vm/gcc3x-cointerp.c:4747
> #2  0x0011d521 in enterSmalltalkExecutiveImplementation () at
> /Users/eliot/Cog/oscogvm/macbuild/../src/vm/gcc3x-cointerp.c:14103
> #3  0x00124bc7 in initStackPagesAndInterpret () at
> /Users/eliot/Cog/oscogvm/macbuild/../src/vm/gcc3x-cointerp.c:17731
> #4  0x00105ec9 in interpret () at
> /Users/eliot/Cog/oscogvm/macbuild/../src/vm/gcc3x-cointerp.c:1933
> (More stack frames follow...)
>
> On Thu, Apr 28, 2011 at 5:26 AM, Mariano Martinez Peck <
> marianopeck at gmail.com> wrote:
>
>>
>> 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:
>>
>> testBlah
>>
>>     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:
>> TraceIsFromInterpreter].
>>     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.
>>
>> --
>> Mariano
>> http://marianopeck.wordpress.com
>>
>>
>>
>
>

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