[Vm-dev] handleCallOrJumpSimulationTrap: curiousity

[Ben Coman]

On Fri, May 20, 2016 at 8:44 PM, Clément Bera <bera.clement at gmail.com> wrote:
>
> Hi Ben,
>
> The primitives present here are the primitives which create a new stack frame or switch to another one.
>
> In your new primitives:
> - do you create a new stack frame ? For example, primitiveClosureValue creates a new stack frame for the block evaluation. I don't think that is the case.

Correct.  It doesn't create a stack frame.

> - do you potentially switch to another process ?

It does when trying to acquire a lock held by someone else, the
process sleeps and does wakeHighestPriority to which it transferTo:

> For example, primitiveResume may switch execution to the resumed process if it has a higher priority, so the active stack frame may have changed. It could be that you have primitives like that.
>
> I'd recommend you not to change that method right now. Instead, you implement your code, then run it in the VM simulator to ensure everything works fine. If the simulator halts in handleCallOrJumpSimulationTrap, then add your primitive here if relevant, else just ignore that method.  Changing this method ahead of time doesn't feel like a good idea.

Thanks for the tip.  I hadn't come across that method yet.  I had
already decided to try and get the simulator working for the first
time this weekend.  Its been interesting poking through the VM with
gdb, but its not "exactly" fun.

cheers -ben


> Have fun :-)
>
> On Fri, May 20, 2016 at 1:46 PM, Ben Coman <btc at openinworld.com> wrote:
>>
>>
>> Minor curiosity & clueless speculation...  in passing I came across
>> the following in #handleCallOrJumpSimulationTrap and given the
>> similarity of critical section and  ownedlock primitives to alter the
>> running process like primitiveWait, I wondered if they should also be
>> in this list ...
>>
>>
>> "Verify the stack layout assumption compileInterpreterPrimitive:
>> makes, provided we've not called something that has built a frame,
>> such as closure value or evaluate method, **or switched frames**,
>> such as primitiveSignal, primitiveWait, primitiveResume,
>> primitiveSuspend et al."
>>
>> ifTrue: [(#( primitiveClosureValue primitiveClosureValueWithArgs
>> primitiveClosureValueNoContextSwitch
>> primitiveFullClosureValue primitiveFullClosureValueWithArgs
>> primitiveFullClosureValueNoContextSwitch
>> primitiveSignal primitiveWait primitiveResume primitiveSuspend primitiveYield
>> primitiveExecuteMethodArgsArray primitiveExecuteMethod
>> primitivePerform primitivePerformWithArgs primitivePerformInSuperclass
>> primitiveTerminateTo primitiveStoreStackp primitiveDoPrimitiveWithArgs)
>>
>> cheers -ben
>
>
>