Segfault at exit when calling `sys.activate_stack_trampoline("perf")` after loading a native library

[GuillaumeLagrange]

Crash report

What happened?

import sys, ctypes
ctypes.CDLL(None)
sys.activate_stack_trampoline("perf")
sys.activate_stack_trampoline("perf")
sys.activate_stack_trampoline("perf")

100% reproducible on 3.13.12, exits cleanly on 3.13.11.
Same between 3.14.3 and 3.14.2

Things of note:

• The crash occurs during interpreter finalization, not at the point of the call
• No exception is raised; is_stack_trampoline_active() returns True after each call
• Without ctypes.CDLL, 3 calls don't crash (but 10 calls do crash with "no more code watcher IDs available" + segfault)
• 2 calls + ctypes.CDLL doesn't crash; 3 calls is the threshold

Repeated calls to activate_stack_trampoline("perf") when the trampoline is already active should either be a no-op or raise an error.

CPython versions tested on:

3.13, 3.14

Operating systems tested on:

Linux

Output from running 'python -VV' on the command line:

Python 3.13.12 (main, Mar 10 2026, 18:17:38) [Clang 21.1.4 ]