[vtkusers] VTK/Java crashes -- WeakGlobalRef or garbage collection problem...solution?

[Denis Barbier]

On 2009/12/17 Jeff Baumes wrote:
> On Thu, Dec 17, 2009 at 6:01 AM, Denis Barbier <bouzim at gmail.com> wrote:
>> On 2009/12/16 Clinton Stimpson wrote:
>>>
>>> How does this relate?
>>> <http://publib.boulder.ibm.com/infocenter/javasdk/v6r0/index.jsp?topic=/com.ibm.java.doc.diagnostics.60/html/mm_gc_coexist.html>
>>> "The Java service team strongly recommends that applications avoid the use of
>>> finalizers as far as possible.  The JVM specification states that finalizers
>>> should be used as an emergency clear-up of, for example, hardware resources."
>>>
>>> Seems to me a can of worms if one attempts to make the garbage collector
>>> thread safe.
>>
>> +1
>>
>> It would certainly be much safer to drop those finalizers and learn to
>> call Delete() when needed.
>
> This could certainly be accomplished by commenting out one line in
> Wrapping/vtkParseJava.c :
>
> fprintf(fp,"\n  protected void finalize() { if (!this.vtkDeleted)
> this.Delete(); }\n");
>
> I agree with the diagnosis of the issue; thanks Nathan for digging
> into this. It appears due the the lack of public outcry in the past
> that the cases that these issues occur are fairly rare. Since we don't
> want to break existing code that assumes garbage collection will take
> care of things, we can make a CMake flag to disable auto-deletion of
> garbage collected objects, which would essentially be this one line
> change to vtkParseJava.c. We would also need to change code in classes
> like vtkPanel to use VTKDelete.
>
> If someone wants to get a patch ready for this, I could look it over
> and commit to CVS head.
>
> The only other solution I can think of is to make all Java-wrapped VTK
> method calls (including finalize()) check a Java mutex lock, to ensure
> that only one thread is accessing the VTK C++ layer at a time. But
> would that affect performance too much?

Hi Jeff, there is another issue about Java, reported by Luke Dodd in
  http://www.vtk.org/pipermail/vtkusers/2009-December/104726.html

It is easy to write Java code which confuses VTK reference counters, I
translated his code into C++ in
  http://www.vtk.org/pipermail/vtkusers/2009-December/104744.html
Can you please tell us what we do wrong wrt reference counters?
Thanks.

Denis