Add some extra checks and tests

Author: sergey-miryanov

Lib/ctypes/__init__.py

@@ -276,8 +276,9 @@ def POINTER(cls):
     except AttributeError:
         pass
     if isinstance(cls, str):
-        return type(f'LP_{cls}', (_Pointer,), {})  # deprecated
+        return type(f'LP_{cls}', (_Pointer,), {})
     return type(f'LP_{cls.__name__}', (_Pointer,), {'_type_': cls})
+
 def pointer(arg):
     typ = POINTER(type(arg))
     return typ(arg)

Lib/test/test_ctypes/test_pointers.py

@@ -216,6 +216,31 @@ def test_pointer_type_str_name(self):
     def test_abstract(self):
         self.assertRaises(TypeError, _Pointer.set_type, 42)
 
+    def test_pointer_types_equal(self):
+        t1 = POINTER(c_int)
+        t2 = POINTER(c_int)
+
+        self.assertIs(t1, t2)
+
+    def test_incomplete_pointer_types_not_equal(self):
+        t1 = POINTER("LP_C")
+        t2 = POINTER("LP_C")
+
+        self.assertIsNot(t1, t2)
+
+    def test_pointer_set_type_twice(self):
+        t1 = POINTER(c_int)
+        t1.set_type(c_int)
+
+    def test_pointer_set_wrong_type(self):
+        t1 = POINTER(c_int)
+        with self.assertRaisesRegex(TypeError, "pointer type already set"):
+            t1.set_type(c_float)
+
+    def test_pointer_not_ctypes_type(self):
+        with self.assertRaisesRegex(TypeError, "must have storage info"):
+            POINTER(int)
+
 
 if __name__ == '__main__':
     unittest.main()

Modules/_ctypes/_ctypes.c

@@ -580,7 +580,11 @@ ctype_get_pointer_type(PyObject *self, void *Py_UNUSED(ignored))
     if (PyStgInfo_FromType(st, self, &info) < 0) {
         return NULL;
     }
-    assert(info); /* Cannot be NULL  */
+    if (!info) {
+        PyErr_Format(PyExc_TypeError, "%R must have storage info", self);
+        return NULL;
+    }
+
     if (info->pointer_type) {
         return Py_NewRef(info->pointer_type);
     }
@@ -1215,21 +1219,29 @@ PyCPointerType_SetProto(ctypes_state *st, PyObject *self, StgInfo *stginfo, PyOb
         return -1;
     }
     if (!info) {
-        PyErr_SetString(PyExc_TypeError,
-                        "_type_ must have storage info");
+        PyErr_Format(PyExc_TypeError, "%R must have storage info", proto);
         return -1;
     }
-    if (info->pointer_type) {
+    if (info->pointer_type && info->pointer_type != self) {
         PyErr_Format(PyExc_TypeError,
             "pointer type already set: old=%R, new=%R",
             info->pointer_type, self);
         return -1;
     }
+    if (stginfo->proto && stginfo->proto != proto) {
+        PyErr_Format(PyExc_TypeError,
+            "cls type already set: old=%R, new=%R",
+            stginfo->proto, proto);
+        return -1;
+    }
 
-    Py_INCREF(proto);
-    Py_XSETREF(stginfo->proto, proto);
+    if (!stginfo->proto) {
+        Py_XSETREF(stginfo->proto, Py_NewRef(proto));
+    }
 
-    Py_XSETREF(info->pointer_type, Py_NewRef(self));
+    if (!info->pointer_type) {
+        Py_XSETREF(info->pointer_type, Py_NewRef(self));
+    }
     return 0;
 }