TST: Join threads in test_printoptions_thread_safety

[pareshjoshij]

The test_printoptions_thread_safety function spawns two threading.Thread objects but never calls .join() on them.

This causes multiple problems:

• The test function can return and be marked as "passed" by pytest before the assertions inside the threads have executed → intermittent failures or false positives.
• Threads are left running when the test process exits → thread leakage, occasional segmentation faults, and “daemon thread still running” warnings.
• Unnecessary non-determinism in an otherwise stable thread-safety regression test.

All other threading tests in the same file already join their threads properly (via run_threaded or ThreadPoolExecutor).

Fix
Add the two missing lines:

    task1.start()
    task2.start()
    task1.join()
    task2.join()

[ngoldbaum]

Thanks! I re-triggered the failing test runs, the failures should be unrelated.

This is one reason I want to republish the threading_helper from CPython's test module: https://docs.python.org/3/library/test.html#module-test.support.threading_helper. Alas it's hard to find the time for projects like that...

[seberg]

Makes sense, thanks @pareshjoshij and Nathan.

[pareshjoshij]

Thanks a lot @ngoldbaum sir & @seberg sir for reviewing and merging! 🎉
Feels great to have my first NumPy contribution accepted. Can’t wait to work on more issues