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Assertion failed: typeinfo->proto in PyCPointerType_from_param_impl when using deprecated POINTER(str) in argtypes #144100
Description
Bug report
Bug description:
import ctypes
# The specific bug is triggered by creating a POINTER type using a string
# (which issues a DeprecationWarning) and then using it for argument conversion.
BadType = ctypes.POINTER("BugTrigger")
# Load standard library (Linux/POSIX specific, matches the crash environment)
libc = ctypes.CDLL(None)
# Use any standard function (e.g., getpid) to attach argtypes
func = libc.getpid
func.argtypes = (BadType,)
try:
# Calling the function forces ctypes to run PyCPointerType_from_param_impl
# on the argument, triggering the "Assertion `typeinfo->proto' failed".
func(ctypes.byref(ctypes.c_int(0)))
except Exception:
passpython: ../Modules/_ctypes/_ctypes.c:1422: PyObject *PyCPointerType_from_param_impl(PyObject *, PyTypeObject *, PyObject *): Assertion `typeinfo->proto' failed.
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Activity
pythongh-144100: Fix crash for POINTER(str) used in ctypes argtypes
gh-144100: Fix crash for POINTER(str) used in ctypes argtypes (#144108)
pythongh-144100: Fix crash for POINTER(str) used in ctypes argtypes (p…
vstinner commentedon Jan 26, 2026
Fixed. Thanks for the bug report.
[3.14] gh-144100: Fix crash for POINTER(str) used in ctypes argtypes (G…
[3.13] gh-144100: Fix crash for POINTER(str) used in ctypes argtypes (#…
pythongh-144100: Fix crash for POINTER(str) used in ctypes argtypes (p…