[Python-Dev] test_minidom non-failure failure? (take 2)

[Neil Schemenauer]

On Thu, Oct 12, 2000 at 04:26:49PM -0500, Guido van Rossum wrote:
> > This is a policy decision.  Is it okay for the test suite to
> > create garbage that is not collectable by reference counting?
> 
> I don't see why that should be forbidden.  After all some of the code
> we test has such leaks -- we haven't declared those absolute bugs.

Again, "-l" should probably not be a default.  I don't know who
added it to TESTOPTS but it wasn't me.

> Can you give an example of how such garbage can be created?

Look at test_gc.  Here is an example:

    class Foo:
        def __del__(self):
            pass
    foo = Foo()
    foo.foo = foo
    del foo

Theoretically this structure could be collected without problem
but the GC is too simple minded to realize that there is only one
finalizer involved.  Here's a better example:

    foo = Foo()
    bar = Foo()
    foo.bar = bar
    bar.foo = foo
    del foo, bar

The GC cannot safely break this cycle so it punts and adds the
instance objects involved to gc.garbage and forgets about it.

  Neil