>>> os.dup2(-1, 0)Traceback (most recent call last):  File "<stdin>", line 1, in <module>  OSError: [Errno 0] Error

The bug is caused by the old manual sign check that at some point lost the part that seterrno:

I'm going to submit a PR with the fix.

Linked PRs

• gh-102179: Fix os.dup2() error reporting for negative fds #102180
• [3.10] gh-102179: Fixos.dup2 error reporting for negative fds (GH-102180) #102419
• [3.11] gh-102179: Fixos.dup2 error reporting for negative fds (GH-102180) #102420