[New-bugs-announce] [issue40795] ctypes: PyErr_WriteUnraisable() called with no exception set on converting callback result failure

[STINNER Victor]

New submission from STINNER Victor <vstinner at python.org>:

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.

----------
components: Library (Lib)
messages: 370089
nosy: vstinner
priority: normal
severity: normal
status: open
title: ctypes: PyErr_WriteUnraisable() called with no exception set on converting callback result failure
versions: Python 3.10, Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40795>
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