selectmodule.c: errno < 0 comparison is always false

[aisk]

Bug report

Bug description:

Summary

Multiple sites in Modules/selectmodule.c check if (errno < 0) after close/epoll_ctl calls. Since errno is an int set to positive values (POSIX), this check is always false. Close errors are silently swallowed.

Fix

Change if (errno < 0) to if (retval < 0) (check the return value, not errno directly).

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-146205: Check the errno with != 0 in close impls in select module #146206