[kepler-dev] Memory leak.

[Edward A. Lee]

Kevin:

You are right...

When a parser is used to open a model, the model itself acquires an
instance of ParserAttribute, which contains a reference to the parser.
Thus, as long as there is an active reference to the model, there
will be a reference to the parser.  We could perhaps change ParserAttribute
to have a weak reference to the parser.

I think the real issue is that the model should pass out of scope,
and maybe it is not being passed out of scope.

Moreover, references to models may persist longer than they should...
Although I think we made an effort to make sure all references to the
model were weak references, I'm not sure we did it exactly right...
Unfortunately, in Java, it seems you can't actually force a weak
reference to dissociate...

Edward


At 01:34 PM 12/21/2005 -0600, Kevin Ruland wrote:

>Edward,
>
>I don't fully understand the situation and defer to you or Christopher for 
>greater details.   Perhaps there is something in the Kepler code which is 
>holding onto a MoMLParser too long.
>
>In kepler there is this code in ActorMetadata.ActorMetadata( InputStream 
>moml):
>
>{
>
>MoMLParser parser = new MoMLParser();
>NamedObj obj = parser.parse( null, moml );
>
>...
>
>}
>
>So in theory the parser should be local and go out of scope.
>
>But in the MoMLParser.parse( URL, Reader ) method, it looks like this is 
>being held onto.  parser returns a variable called _topLevel.  But there 
>is code in the parse() method which assigns this (MoMLParser) to an 
>attribute of _topLevel called "_parser".  I believe this is where the 
>reference to the MoMLParser is being retained.
>
>Kevin
>
>Edward A. Lee wrote:
>
>>At 12:29 AM 12/21/2005 -0800, Christopher Brooks wrote:
>>
>>>Yep, this looks like a leak of some sort.
>>>
>>>In MoMLParser, _parser is declared as:
>>>     private XmlParser _parser = new XmlParser();
>>
>>
>>
>>I'm confused... Wouldn't the leak then actually be
>>in the creation of multiple instances of MoMLParser without
>>deleting them?
>
>------------
>Edward A. Lee
>Professor, Chair of the EE Division, Associate Chair of EECS
>231 Cory Hall, UC Berkeley, Berkeley, CA 94720
>phone: 510-642-0253 or 510-642-0455, fax: 510-642-2845
>eal at eecs.Berkeley.EDU, http://ptolemy.eecs.berkeley.edu/~eal