bpo-44172: Keep reference to original window in curses subwindow objects

[michaelforney]

The X/Open curses specification[0] and ncurses documentation[1]
both state that subwindows must be deleted before the main window.

Deleting the windows in the wrong order causes a double-free with
NetBSD's curses implementation.

To fix this, keep track of the original window object in the subwindow
object, and keep a reference to the original for the lifetime of
the subwindow.

[0] https://pubs.opengroup.org/onlinepubs/7908799/xcurses/delwin.html
[1] https://invisible-island.net/ncurses/man/curs_window.3x.html

https://bugs.python.org/issue44172

[the-knights-who-say-ni]

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[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[michaelforney]

Still waiting for a review.

[serhiy-storchaka]

Thank you for your contribution, @michaelforney. I apologize for the delay in the review.

The code LGTM. I resolved conflicts and added a test. I'll try to test it on NetBSD, but it can take a time. Could you please test that the added test exposes the issue with unpatched code?

[miss-islington-app]

Thanks @michaelforney for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @michaelforney and @serhiy-storchaka, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 0af61fe2f41048d66b0a973bbff056690446d3df 3.13

[bedevere-app]

GH-133370 is a backport of this pull request to the 3.13 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot PPC64LE RHEL8 LTO + PGO 3.x (tier-2) has failed when building commit 0af61fe.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/458/builds/6121) and take a look at the build logs.
4. Check if the failure is related to this commit (0af61fe) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/458/builds/6121

Failed tests:

• test_frame

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 19, done.        
remote: Counting objects:   7% (1/14)        
remote: Counting objects:  14% (2/14)        
remote: Counting objects:  21% (3/14)        
remote: Counting objects:  28% (4/14)        
remote: Counting objects:  35% (5/14)        
remote: Counting objects:  42% (6/14)        
remote: Counting objects:  50% (7/14)        
remote: Counting objects:  57% (8/14)        
remote: Counting objects:  64% (9/14)        
remote: Counting objects:  71% (10/14)        
remote: Counting objects:  78% (11/14)        
remote: Counting objects:  85% (12/14)        
remote: Counting objects:  92% (13/14)        
remote: Counting objects: 100% (14/14)        
remote: Counting objects: 100% (14/14), done.        
remote: Compressing objects:   8% (1/12)        
remote: Compressing objects:  16% (2/12)        
remote: Compressing objects:  25% (3/12)        
remote: Compressing objects:  33% (4/12)        
remote: Compressing objects:  41% (5/12)        
remote: Compressing objects:  50% (6/12)        
remote: Compressing objects:  58% (7/12)        
remote: Compressing objects:  66% (8/12)        
remote: Compressing objects:  75% (9/12)        
remote: Compressing objects:  83% (10/12)        
remote: Compressing objects:  91% (11/12)        
remote: Compressing objects: 100% (12/12)        
remote: Compressing objects: 100% (12/12), done.        
remote: Total 19 (delta 2), reused 3 (delta 2), pack-reused 5 (from 2)        
From https://github.com/python/cpython
 * branch                    main       -> FETCH_HEAD
Note: switching to '0af61fe2f41048d66b0a973bbff056690446d3df'.

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Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at 0af61fe2f41 bpo-44172: Keep reference to original window in curses subwindow objects (GH-26226)
Switched to and reset branch 'main'

configure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled for removal in Python 3.15)

find: ‘build’: No such file or directory
find: ‘build’: No such file or directory
find: ‘build’: No such file or directory
find: ‘build’: No such file or directory
make[2]: [Makefile:3340: clean-retain-profile] Error 1 (ignored)
./Modules/_testlimitedcapi/unicode.c: In function ‘test_string_from_format’:
./Modules/_testlimitedcapi/unicode.c:1416:1: note: variable tracking size limit exceeded with -fvar-tracking-assignments, retrying without
 test_string_from_format(PyObject *self, PyObject *Py_UNUSED(ignored))
 ^~~~~~~~~~~~~~~~~~~~~~~
Python/Python-ast.c: In function ‘init_types’:
Python/Python-ast.c:6137:1: note: variable tracking size limit exceeded with -fvar-tracking-assignments, retrying without
 init_types(void *arg)
 ^~~~~~~~~~
./Modules/_testlimitedcapi/unicode.c: In function ‘test_string_from_format’:
./Modules/_testlimitedcapi/unicode.c:1416:1: note: variable tracking size limit exceeded with -fvar-tracking-assignments, retrying without
 test_string_from_format(PyObject *self, PyObject *Py_UNUSED(ignored))
 ^
Python/Python-ast.c: In function ‘init_types’:
Python/Python-ast.c:6137:1: note: variable tracking size limit exceeded with -fvar-tracking-assignments, retrying without
 init_types(void *arg)
 ^
Python/Python-ast.c: In function ‘init_types’:
Python/Python-ast.c:6137:1: note: variable tracking size limit exceeded with -fvar-tracking-assignments, retrying without
 init_types(void *arg)
 ^
Python/Python-ast.c: In function ‘init_types’:
Python/Python-ast.c:6137:1: note: variable tracking size limit exceeded with -fvar-tracking-assignments, retrying without
 init_types(void *arg)
 ^

make: *** [Makefile:2454: buildbottest] Error 2