After PR22360 merged, we can move the codecs' register operation to testcases.

New changeset c9f696c by Hai Shi in branch 'master':
bpo-41919, test_codecs: Move codecs.register calls to setUp() (GH-22513)
c9f696c

Commit c9f696c introduced a reference leak in the test suite. See https://bugs.python.org/issue42145:

c9f696c is the first bad commit
commit c9f696c
Author: Hai Shi <shihai1992@gmail.com>
Date: Fri Oct 16 16:34:15 2020 +0800

bpo-41919, test_codecs: Move codecs.register calls to setUp() (GH-22513)

Reverting the commit eliminates the problem:

rences, sum=12
test_io leaked [1, 1, 1, 1] memory blocks, sum=4
test_io failed

== Tests result: FAILURE ==

1 test failed:
test_io

Total duration: 397 ms
Tests result: FAILURE
g
~/github/python/master master|bisect*
❯ git revert c9f696c
Auto-merging Lib/test/test_codecs.py
[master f3de7c00b4] Revert "bpo-41919, test_codecs: Move codecs.register calls to setUp() (GH-22513)"
7 files changed, 112 insertions(+), 16 deletions(-)

~/github/python/master master|bisect* ⇡
❯ make -j -s
CC='gcc -pthread' LDSHARED='gcc -pthread -shared ' OPT='-g -Og -Wall' _TCLTK_INCLUDES='' _TCLTK_LIBS='' ./python -E ./setup.py -q build

The following modules found by detect_modules() in setup.py, have been
built by the Makefile instead, as configured by the Setup files:
_abc atexit pwd
time

~/github/python/master master|bisect* ⇡
❯ ./python -m test test_io -m test.test_io.CTextIOWrapperTest.test_read_one_by_one -R :
0:00:00 load avg: 2.57 Run tests sequentially
0:00:00 load avg: 2.57 [1/1] test_io
beginning 9 repetitions
123456789
.........

== Tests result: SUCCESS ==

1 test OK.

Total duration: 455 ms
Tests result: SUCCESS

* Move the codecs' (un)register operation to testcases.
* Remove _codecs._forget_codec() and _PyCodec_Forget()

Lib/test/test_charmapcodec.py | 7 +++++--
Lib/test/test_codecs.py | 25 +++----------------------
Lib/test/test_io.py | 7 +++----
Lib/test/test_unicode.py | 5 ++++-
Modules/_codecsmodule.c | 20 --------------------
Modules/clinic/_codecsmodule.c.h | 39 +--------------------------------------
Python/codecs.c | 25 -------------------------
7 files changed, 16 insertions(+), 112 deletions(-)

AS this is masking other issues in the build bots, we need to revert the commit unless is fixed in 24 hours per the buildbot workflow

AS this is masking other issues in the build bots, we need to revert the commit unless is fixed in 24 hours per the buildbot workflow

Thanks, Pablo. I checked that only test_io.py have resource leak.
I create PR-22973, pls take a look if you have free time, thanks.

New changeset 14cdc21 by Hai Shi in branch 'master':
bpo-41919: Avoid resource leak in test_io (GH-22973)
14cdc21