Issue #4606: Passing 'None' if ctypes argtype is set to POINTER(...)

does now always result in NULL.

Lib/ctypes/test/test_parameters.py

@@ -97,7 +97,7 @@ class SimpleTypesTestCase(unittest.TestCase):
         self.assertEqual(x.contents.value, 42)
         self.assertEqual(LPINT(c_int(42)).contents.value, 42)
 
-        self.assertEqual(LPINT.from_param(None), 0)
+        self.assertEqual(LPINT.from_param(None), None)
 
         if c_int != c_long:
             self.assertRaises(TypeError, LPINT.from_param, pointer(c_long(42)))

Misc/NEWS

@@ -376,8 +376,11 @@ Core and Builtins
 Library
 -------
 
-- Issue #5042: Structure sub-subclass does now initialize correctly
-  with base class positional arguments.
+- Issue #4606: Passing 'None' if ctypes argtype is set to POINTER(...)
+  does now always result in NULL.
+
+- Issue #5042: ctypes Structure sub-subclass does now initialize
+  correctly with base class positional arguments.
 
 - Issue #6938: Fix a TypeError in string formatting of a multiprocessing
   debug message.

Modules/_ctypes/_ctypes.c

@@ -972,8 +972,11 @@ PyCPointerType_from_param(PyObject *type, PyObject *value)
 {
 	StgDictObject *typedict;
 
-	if (value == Py_None)
-		return PyInt_FromLong(0); /* NULL pointer */
+	if (value == Py_None) {
+		/* ConvParam will convert to a NULL pointer later */
+		Py_INCREF(value);
+		return value;
+	}
 
 	typedict = PyType_stgdict(type);
 	assert(typedict); /* Cannot be NULL for pointer types */

Modules/_ctypes/callproc.c

@@ -542,6 +542,7 @@ PyTypeObject PyCArg_Type = {
  * C function call.
  *
  * 1. Python integers are converted to C int and passed by value.
+ *    Py_None is converted to a C NULL pointer.
  *
  * 2. 3-tuples are expected to have a format character in the first
  *    item, which must be 'i', 'f', 'd', 'q', or 'P'.