FileIO.__init__ aborts when opener returns bad fd

[tekknolagi]

BPO	38031
Nosy	@ZackerySpytz, @tekknolagi, @iritkatriel
PRs	bpo-38031: Fix a possible assertion failure in _io.FileIO() #15688

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-09-04.21:19:41.772>
labels = ['interpreter-core', '3.9', 'expert-IO', '3.11', '3.10', 'type-crash']
title = 'FileIO.__init__ aborts when opener returns bad fd'
updated_at = <Date 2021-10-18.23:22:00.544>
user = 'https://github.com/tekknolagi'

bugs.python.org fields:

activity = <Date 2021-10-18.23:22:00.544>
actor = 'iritkatriel'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core', 'IO']
creation = <Date 2019-09-04.21:19:41.772>
creator = 'tekknolagi'
dependencies = []
files = []
hgrepos = []
issue_num = 38031
keywords = ['patch']
message_count = 3.0
messages = ['351150', '351159', '404246']
nosy_count = 3.0
nosy_names = ['ZackerySpytz', 'tekknolagi', 'iritkatriel']
pr_nums = ['15688']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue38031'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[tekknolagi]

On a debug build, the following causes an abort:

import _io
_io.FileIO("foobar", opener=lambda name, flags: 1000000)

1000000 is not a valid fd. FileIO attempts to raise an IOError from errno, but there is already an exception set when PyErr_SetFromErrno uses PyObject_Call to create the exception.

[ZackerySpytz]

Thank you for the report.

[iritkatriel]

Reproduced on 3.11.