[Scons-dev] Announcement: Core changes for v2.4 ahead, Switching the Node class to using slots...

[Kenny, Jason L]

Hi dirk,

I need to give this a run. As I am one of the people that would be in a dangerous area :-)

My first thought however would be this:

1) did we add a __dict__ to the __slots__ ? if not can we, this would probally fix 99% of the issues I would have in Parts
2)  stuff like t.abspath -> t.get_abspath(), can the t.abspath be a property that calls t.get_abspath()? 

This seems like this would deal with most of the concerns people might have. I understand that there might be good reason not to do this. I haven't looked in detail yet myself.

Just some thoughts.

Jason


-----Original Message-----
From: Scons-dev [mailto:scons-dev-bounces at scons.org] On Behalf Of Dirk Bächle
Sent: Saturday, February 28, 2015 6:03 AM
To: SCons users mailing list
Cc: SCons developer list
Subject: [Scons-dev] Announcement: Core changes for v2.4 ahead, Switching the Node class to using slots...

Hello there,

as has been pre-announced at

   https://pairlist4.pair.net/pipermail/scons-users/2014-July/002734.html

and

   https://pairlist2.pair.net/pipermail/scons-dev/2014-December/002107.html

we're still planning to switch the Node class to using "slots" in the core sources, mainly for reducing the overall memory consumption by up to 35% in large build projects.

We have now pushed a new branch named "switch_to_slots" to the main SCons repo, and ran it against our test suite in Buildbot ( http://buildbot.scons.org/waterfall ). So far, the implementation looks stable and for the normal user there shouldn't be any danger of scripts/builds breaking after an update to the new release 2.4 (coming probably in a month or so).

However, if you write and maintain your own extensions, where you regularly reach into the bowels of SCons to extract internal data or to override methods (monkey-patching), there is a chance that you'll get bitten by the changes as described in the appendix below.

We invite any interested user/developer to try out the current "slots" branch, by cloning

   hg clone http://bitbucket.org/scons/scons -r switch_to_slots

to a local folder (not your standard SCons repo!), and starting it via the "bootstrap.py" script:

   python ~/try_out_folder/scons/bootstrap.py

Please report back any errors or inconveniences that you find, such that we can work on a solution together.
If you have further questions, better ask them now. We won't look back after merging this. ;)


Best regards,

Dirk


Appendix: Short list of changes to the Node* classes ====================================================

- Introduction of decorators for memoizer debugging/counting (we can't use metaclasses anymore).
- Adding interface for accessing node attributes that may get initialized lazily:
      t.abspath -> t.get_abspath()
      t.labspath -> t.get_labspath()
      t.tpath -> t.get_tpath()
      t.path_elements -> t.get_path_elements()
      t.path -> t.get_internal_path()

- Methods like t.exists(), t.rexists() and t.get_contents() can't be re-assigned directly anymore. They'll be realized via function maps internally ( {int : func} ).

- NodeInfo and BuildInfo will also get switched to __slots__, and get a new internal version number (1.0 -> 2.0). This means that after the switch *all* targets are regarded to be out-of-date on the first build.
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