MemoryError when using selectors on Solaris

[kulikjak]

If you set ulimit -n unlimited on Solaris and its derivatives (where /dev/poll is available) and import selectors, Python crashes with a MemoryError:

> ulimit -n unlimited
> python3.11 -c "import selectors"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.11/selectors.py", line 613, in <module>
    elif _can_use('devpoll'):
         ^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/selectors.py", line 594, in _can_use
    selector_obj = selector()
                   ^^^^^^^^^^
MemoryError

The issue is that Python uses RLIMIT_NOFILE to allocated that many struct pollfds, and there is no upper limit. Infinity is represented by something close to INT_MAX, and the allocation thus fails.

Your environment

I tested this on Oracle Solaris with 3.11, 3.9 and 3.7 (where you need a slightly different way to crash it: python3.7 -c "import select; select.devpoll()").

I verified that on SmartOS, it behaves the same way (on SmartOS, you can actually set huge ulimit -n values that break it as well).

Linked PRs

• gh-102494: fix MemoryError when using selectors on Solaris #102495