_socket: socket.sethostname() reports a failed buffer export as an OS error, raising SystemError #161665

Bug report

Summary

socket.sethostname() accepts a bytes subclass, and if getting a buffer from that object fails, the error is not reported. Instead SystemError is returned to caller.

SystemError: <class 'OSError'> returned a result with an exception set

Reproducer

import os
import socket

class B(bytes):
    def __buffer__(self, flags):
        raise KeyError("boom")

try:
    os.stat("/nonexistent")
except OSError:
    pass

socket.sethostname(B(b"h"))

Traceback (most recent call last):
  File "min.py", line 23, in <module>
    socket.sethostname(B(b"h"))
    ~~~~~~~~~~~~~~~~~~^^^^^^^^^
SystemError: <class 'OSError'> returned a result with an exception set

CPython versions tested on:

3.15

Operating systems tested on:

Linux

Linked PRs

• gh-161665: Propagate buffer errors in socket.sethostname() #161684