test_tkinter leaks references on Windows

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• Latest successful build: https://buildbot.python.org/all/#/builders/920/builds/543
• First failing build: https://buildbot.python.org/all/#/builders/920/builds/549

test_tkinter leaked [336, 336, 337] references, sum=1009
test_tkinter leaked [151, 151, 152] memory blocks, sum=454

Linked PRs

• gh-111531: Tkinter: fix reference leaks in bind_class() and bind_all() #111533
• [3.12] gh-111531: Tkinter: fix reference leaks in bind_class() and bind_all() (GH-111533) #111535
• [3.11] gh-111531: Tkinter: fix reference leaks in bind_class() and bind_all() (GH-111533) #111536

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git bisect points me to PR #111202 and commit 9bb202a:

9bb202a1a90ef0edce20c495c9426d9766df11bb is the first bad commit
commit 9bb202a1a90ef0edce20c495c9426d9766df11bb
Author: Serhiy Storchaka <[email protected]>
Date:   Tue Oct 24 13:02:12 2023 +0300

    gh-75666: Tkinter: add tests for binding (GH-111202)

 Lib/test/test_tkinter/test_misc.py | 307 +++++++++++++++++++++++++++++++++++++
 1 file changed, 307 insertions(+)

[terryjreedy]

@serhiy-storchaka
f:\dev\3x>python -m test -ugui -R3:3 -m BindTest test_tkinter.test_misc
...
test_tkinter.test_misc leaked [336, 336, 336] references, sum=1008
test_tkinter.test_misc leaked [151, 151, 151] memory blocks, sum=453
test_tkinter.test_misc failed (reference leak)

I am running experiments to see which individual tests leak.

[terryjreedy]

I initially commented out blocks, then changed the -m arg to a test name and checked for only 1 match.
Leaks are pretty well spread out. Results, possibly with errors:
test_??? name(s): references, blocks

bind, unbind, unbind2: 6, 0
rebind, bind_class: 30,16
unbind_class: 30, 8
bind_class_rebind: 46, 18
bind_all: 30, 18
bind_tags: 0, 0
bind_events: 102, 59
unbind_all: 38, 20
bind_all_rebind: 53, 20

[serhiy-storchaka]

Thank you for your report Victor. It is not only on Windows.

I knew that something may be wrong with bind_class() and bind_all(), and was going to open a new issue when found a reproducer, but I did not know that it also causes leaks.

[serhiy-storchaka]

Thank you for your tests Terry. Could you please also check if #111533 fixes leaks? I do not see leaks in bind() on Linux, all leaks were in bind_class() and bind_all().

[vstinner]

Oh, that was a quick fix 👍