ctypes: PyErr_WriteUnraisable() called with no exception set on converting callback result failure

[vstinner]

BPO	40795
Nosy	@vstinner, @miss-islington
PRs	bpo-40795: ctypes calls unraisablehook with an exception #20452 [3.9] bpo-40795: ctypes calls unraisablehook with an exception (GH-20452) #20469 [3.8] bpo-40795: ctypes calls unraisablehook with an exception (GH-20452) #20470

^{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 = <Date 2020-05-27.23:01:28.076>
created_at = <Date 2020-05-27.14:44:18.344>
labels = ['3.8', 'library', '3.9', '3.10']
title = 'ctypes: PyErr_WriteUnraisable() called with no exception set on converting callback result failure'
updated_at = <Date 2020-05-27.23:01:28.075>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2020-05-27.23:01:28.075>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2020-05-27.23:01:28.076>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2020-05-27.14:44:18.344>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 40795
keywords = ['patch']
message_count = 4.0
messages = ['370089', '370145', '370148', '370149']
nosy_count = 2.0
nosy_names = ['vstinner', 'miss-islington']
pr_nums = ['20452', '20469', '20470']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue40795'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[vstinner]

Example:
---

from ctypes import c_int, CFUNCTYPE

def func():
    return (1, 2, 3)

cb = CFUNCTYPE(c_int)(func)
cb()

---

Output:
---

Traceback (most recent call last):
  File "_ctypes/callbacks.c", line 262, in 'converting callback result'
TypeError: an integer is required (got type tuple)
Exception ignored in: <function func at 0x7f0c267ff1f0>

---

Assertion error in debug mode:
---

Traceback (most recent call last):
  File "_ctypes/callbacks.c", line 262, in 'converting callback result'
TypeError: 'tuple' object cannot be interpreted as an integer
python: Python/errors.c:1435: _PyErr_WriteUnraisableMsg: Assertion `exc_type != NULL' failed.
Abandon (core dumped)

---

Attached PR fix the issue.

[vstinner]

New changeset 10228ba by Victor Stinner in branch 'master':
bpo-40795: ctypes calls unraisablehook with an exception (GH-20452)
10228ba

[miss-islington]

New changeset 45ce0db by Miss Islington (bot) in branch '3.8':
bpo-40795: ctypes calls unraisablehook with an exception (GH-20452)
45ce0db

[miss-islington]

New changeset 9e3c583 by Miss Islington (bot) in branch '3.9':
bpo-40795: ctypes calls unraisablehook with an exception (GH-20452)
9e3c583