Extraneous error output when process exits after using subinterpreters

[a-reich]

Bug report

Bug description:

I opened an issue earlier on the repo for the PyPI backport, but now that PEP 734 is implemented (🎉!) I am doing so here.

Reproducer:

>>> from concurrent import interpreters
>>> interp1 = interpreters.create()
>>> interp1.close() # same output occurs without this
>>> exit
Exception ignored while calling deallocator <function Interpreter.__del__ at 0x7308402c8460>:
Traceback (most recent call last):
 File "/usr/lib/python3.14/concurrent/interpreters/__init__.py", line 146, in __del__
 File "/usr/lib/python3.14/concurrent/interpreters/__init__.py", line 162, in _decref
TypeError: catching classes that do not inherit from BaseException is not allowed

I am on release 3.14.0b3 installed as an ubuntu distribution, running on WSL.

CPython versions tested on:

3.14

Operating systems tested on:

Linux

Linked PRs

• gh-135729: Store reference to globals in Interpreter._decref #139104
• [3.14] gh-135729: Store reference to globals in Interpreter._decref (GH-139104) #139112

[brianschubert]

Also reproduces on main, cc @ericsnowcurrently

[sobolevn]

This happens because InterpreterNotFoundError is already None at this point:

cpython/Lib/concurrent/interpreters/__init__.py

Lines 156 to 163 in 1ddfe59

	def _decref(self):
	if not self._ownsref:
	return
	self._ownsref = False
	try:
	_interpreters.decref(self._id)
	except InterpreterNotFoundError:
	pass

[sergey-miryanov]

This doesn't reproduce on main (b57b619) on windows.

[sobolevn]

It does on 0d9d489 on macos:

Python 3.15.0a0 (heads/main:0d9d48959e0, Jun 23 2025, 12:06:51) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from concurrent import interpreters
>>> interp1 = interpreters.create()
>>> 
KeyboardInterrupt
Exception ignored while calling deallocator <function Interpreter.__del__ at 0x1060634d0>:
Traceback (most recent call last):
 File "/Users/sobolev/Desktop/cpython/Lib/concurrent/interpreters/__init__.py", line 146, in __del__
 File "/Users/sobolev/Desktop/cpython/Lib/concurrent/interpreters/__init__.py", line 162, in _decref
TypeError: catching classes that do not inherit from BaseException is not allowed
 

[sergey-miryanov]

@sobolevn can you check with this fix #135728 ?

[sobolevn]

Still happens even after #135728