weakrefs and avoiding bad gc cycles

[Aaron Bentley]

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On 11-06-14 03:21 PM, Martin Pool wrote:
> On 14 June 2011 11:26, Aaron Bentley <aaron at aaronbentley.com> wrote:
> 
>> On 11-06-13 05:57 PM, Martin Pool wrote:
>>> When we want to for instance
>>> assert that something is definitely closed before the end of a test,
>>> there are better deterministic ways to do it without involving gc.
>>
>> For objects where we do want to warn about failure to clean up, perhaps
>> they should register themselves with a singleton, and unregister on
>> cleanup?  Then we can ask the singleton whether any items still need
>> cleanup.
> 
> In production

I only meant for testing.

> when a particular bit of code finishes, we want it to
> clean up after itself.  This is probably most easily done using
> addCleanup or with, hanging off something with the appropriate
> lifetime.

Agreed.

> Generally this shouldn't really hang off a real global; if
> it's something that should last as long as the bzr process there is a
> library state object.

Ah, true.

> I would probably incline away from having the global
> registry always present just in case we want to use it in the test,
> because it might impede gc and it might encourage people to keep
> things for ever.

You're right.  I was thinking of something we could turn on for testing
purposes.

> Perhaps in some cases it's enough to just observe
> all the cleanups were called.  For things like locks where it is
> possible to independently observe if the cleanup has been done, I
> would rather just directly check that: it avoids adding infrastructure
> and is a stronger assertion.  Things like network connections where we
> can't directly observe them probably need to be tracked.

Sure.

Aaron
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