Re: [Pyobjc-dev] Re: [Pyobjc-checkins] CVS: pyobjc/Modules/objc objc_util.h,1.24,1.25 objc_util.m,1.48,1.49

[Bob I. <bo...@re...>]

On Apr 7, 2004, at 1:43 PM, Ronald Oussoren wrote:

>
> On 7-apr-04, at 19:30, Bob Ippolito wrote:
>
>>
>> On Apr 7, 2004, at 1:17 PM, Ronald Oussoren wrote:
>>
>>>
>>> On 7-apr-04, at 19:11, Bob Ippolito wrote:
>>>>
>>>> Because creating one is harmless, and if you don't create one you 
>>>> leak memory.
>>>
>>> Creating one is not harmless if you never release it, you still leak 
>>> memory without any message about this.
>>>
>>> We currently leak 1 NSInvocation while creating the 
>>> NSAutoreleasePool in a new thread, and this is logged. Because it is 
>>> logged I get nagged anytime I run the unittests, which makes it more 
>>> likely that this problem will be fixed.
>>
>> The NSAutoreleasePool goes away whenever the threadstate dict does, 
>> and that's up to Python to decide.  My best guess is that it goes 
>> away as soon as you call PyGILState_Release, but I have not yet 
>> looked at the implementation.
>
> It goes away when the gilstate_counter is 0, which is when you call 
> PyGILState_Release.
>
> I'm not sure what happens when you call into ObjC from a thread that 
> already has a python threadstate (e.g. a thread created using 
> thread/threading).  From a fairly light reading of the source I assume 
> that the pool won't be released until the thread dies.

If ObjC calls into a thread that already has a Python threadstate it 
will not create an NSAutoreleasePool, if you look closely at the code 
you can see that it will only execute that code if PyGILState_Ensure is 
creating a new threadstate.  As far as this code is concerned, there 
are 3 kinds of threads:

1) The main thread.  It already has a global NSAutoreleasePool (by 
PyObjC initialization) and a Python threadstate.  When it gets a 
callback from ObjC, since it has a threadstate already, it just does 
PyGILState_Ensure().

2) A Python-created thread.  You must create an NSAutoreleasePool 
yourself if you create a python thread and then start calling into ObjC 
from it.  Since it has a threadstate already, it just does 
PyGILState_Ensure().

3) An ObjC-created thread.  These do not have a threadstate already, so 
it will do PyGILState_Ensure() and create a NSAutoreleasePool which 
will be collected at PyGILState_Release() time.

-bob