10000 gh-99266: ctypes: Preserve more detailed exception in `ArgumentError` · python/cpython@b4e11a7 · GitHub
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gh-99266: ctypes: Preserve more detailed exception in ArgumentError
Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>
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‎Doc/library/ctypes.rst

Lines changed: 13 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -466,6 +466,14 @@ integer, string, bytes, a :mod:`ctypes` instance, or an object with an
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Return types
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^^^^^^^^^^^^
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469+
.. testsetup::
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from ctypes import CDLL, c_char, c_char_p
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from ctypes.util import find_library
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libc = CDLL(find_library('c'))
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strchr = libc.strchr
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By default functions are assumed to return the C :c:expr:`int` type. Other
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return types can be specified by setting the :attr:`restype` attribute of the
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function object.
@@ -502,18 +510,19 @@ If you want to avoid the ``ord("x")`` calls above, you can set the
502510
:attr:`argtypes` attribute, and the second argument will be converted from a
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single character Python bytes object into a C char::
504512

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.. doctest::
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505515
>>> strchr.restype = c_char_p
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>>> strchr.argtypes = [c_char_p, c_char]
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>>> strchr(b"abcdef", b"d")
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'def'
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b'def'
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>>> strchr(b"abcdef", b"def")
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
512-
ArgumentError: argument 2: TypeError: one character string expected
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ctypes.ArgumentError: argument 2: TypeError: one character bytes, bytearray or integer expected
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>>> print(strchr(b"abcdef", b"x"))
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None
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>>> strchr(b"abcdef", b"d")
516-
'def'
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b'def'
517526
>>>
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You can also use a callable Python object (a function or a class for example) as

‎Lib/test/test_ctypes/test_functions.py

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -54,6 +54,23 @@ class X(object, _SimpleCData):
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class X(object, Structure):
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_fields_ = []
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def test_c_char_parm(self):
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proto = CFUNCTYPE(c_int, c_char)
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def callback(*args):
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return 0
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callback = proto(callback)
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self.assertEqual(callback(b"a"), 0)
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with self.assertRaises(ArgumentError) as cm:
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callback(b"abc")
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self.assertEqual(str(cm.exception),
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"argument 1: TypeError: one character bytes, "
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"bytearray or integer expected")
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5774
@need_symbol('c_wchar')
5875
def test_wchar_parm(self):
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f = dll._testfunc_i_bhilfd
@@ -62,6 +79,18 @@ def test_wchar_parm(self):
6279
self.assertEqual(result, 139)
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self.assertEqual(type(result), int)
6481

82+
with self.assertRaises(ArgumentError) as cm:
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f(1, 2, 3, 4, 5.0, 6.0)
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self.assertEqual(str(cm.exception),
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"argument 2: TypeError: unicode string expected "
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"instead of int instance")
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with self.assertRaises(ArgumentError) as cm:
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f(1, "abc", 3, 4, 5.0, 6.0)
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self.assertEqual(str(cm.exception),
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"argument 2: TypeError: one character unicode string "
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"expected")
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@need_symbol('c_wchar')
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def test_wchar_result(self):
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f = dll._testfunc_i_bhilfd

‎Lib/test/test_ctypes/test_parameters.py

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -78,6 +78,29 @@ def test_cw_strings(self):
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pa = c_wchar_p.from_param(c_wchar_p("123"))
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self.assertEqual(type(pa), c_wchar_p)
8080

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def test_c_char(self):
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from ctypes import c_char
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with self.assertRaises(TypeError) as cm:
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c_char.from_param(b"abc")
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self.assertEqual(str(cm.exception),
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"one character bytes, bytearray or integer expected")
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@need_symbol('c_wchar')
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def test_c_wchar(self):
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from ctypes import c_wchar
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with self.assertRaises(TypeError) as cm:
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c_wchar.from_param("abc")
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self.assertEqual(str(cm.exception),
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"one character unicode string expected")
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with self.assertRaises(TypeError) as cm:
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c_wchar.from_param(123)
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self.assertEqual(str(cm.exception),
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"unicode string expected instead of int instance")
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def test_int_pointers(self):
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from ctypes import c_short, c_uint, c_int, c_long, POINTER, pointer
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LPINT = POINTER(c_int)

‎Misc/NEWS.d/next/Library/2022-11-24-21-52-31.gh-issue-99266.88GcV9.rst

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
Preserve more detailed error messages in :mod:`ctypes`.

‎Modules/_ctypes/_ctypes.c

Lines changed: 17 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2197,6 +2197,7 @@ PyCSimpleType_from_param(PyObject *type, PyObject *value)
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struct fielddesc *fd;
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PyObject *as_parameter;
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int res;
2200+
PyObject *exc, *val, *tb;
22002201

22012202
/* If the value is already an instance of the requested type,
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we can use it as is */
@@ -2230,24 +2231,37 @@ PyCSimpleType_from_param(PyObject *type, PyObject *value)
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parg->obj = fd->setfunc(&parg->value, value, 0);
22312232
if (parg->obj)
22322233
return (PyObject *)parg;
2233-
PyErr_Clear();
2234+
PyErr_Fetch(&exc, &val, &tb);
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Py_DECREF(parg);
22352236

22362237
if (_PyObject_LookupAttr(value, &_Py_ID(_as_parameter_), &as_parameter) < 0) {
2238+
Py_XDECREF(exc);
2239+
Py_XDECREF(val);
2240+
Py_XDECREF(tb);
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return NULL;
22382242
}
22392243
if (as_parameter) {
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if (_Py_EnterRecursiveCall("while processing _as_parameter_")) {
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Py_DECREF(as_parameter);
2246+
Py_XDECREF(exc);
2247+
Py_XDECREF(val);
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Py_XDECREF(tb);
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return NULL;
22432250
}
22442251
value = PyCSimpleType_from_param(type, as_parameter);
22452252
_Py_LeaveRecursiveCall();
22462253
Py_DECREF(as_parameter);
2254+
Py_XDECREF(exc);
2255+
Py_XDECREF(val);
2256+
Py_XDECREF(tb);
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return value;
22482258
}
2249-
PyErr_SetString(PyExc_TypeError,
2250-
"wrong type");
2259+
if (exc) {
2260+
PyErr_Restore(exc, val, tb);
2261+
}
2262+
else {
2263+
PyErr_SetString(PyExc_TypeError, "wrong type");
2264+
}
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return NULL;
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}
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