Added all test cases

Author: VanshAgarwal24036

Lib/test/test_ctypes/test_arrays.py

@@ -4,7 +4,7 @@
 from ctypes import (Structure, Array, ARRAY, sizeof, addressof,
                     create_string_buffer, create_unicode_buffer,
                     c_char, c_wchar, c_byte, c_ubyte, c_short, c_ushort, c_int, c_uint,
-                    c_long, c_ulonglong, c_float, c_double, c_longdouble)
+                    c_long, c_ulonglong, c_float, c_double, c_longdouble, POINTER)
 from test.support import bigmemtest, _2G, threading_helper, Py_GIL_DISABLED
 from ._support import (_CData, PyCArrayType, Py_TPFLAGS_DISALLOW_INSTANTIATION,
                        Py_TPFLAGS_IMMUTABLETYPE)
@@ -147,6 +147,61 @@ def test_ctypes_array_class_assignment_signed_unsigned(self):
         with self.assertRaises(TypeError):
             a.__class__ = B
 
+    def test_ctypes_array_class_assignment_compatible(self):
+        A = c_int * 3
+        class SameArray(Array):
+            _type_ = c_int
+            _length_ = 3
+        a = A(1, 2, 3)
+        a.__class__ = SameArray
+
+    def test_ctypes_array_class_assignment_non_ctypes_target(self):
+        A = c_int * 3
+        a = A()
+        class Dummy:
+            pass
+
+        with self.assertRaises(TypeError):
+            a.__class__ = Dummy
+
+    def test_ctypes_array_class_assignment_abstract_target(self):
+        A = c_int * 3
+        a = A()
+        AbstractArray = PyCArrayType.__new__(PyCArrayType, "AbstractArray", (Array,), {})
+
+        with self.assertRaises(TypeError):
+            a.__class__ = AbstractArray
+
+    def test_ctypes_array_class_assignment_same_size_ints(self):
+        if sizeof(c_int) != sizeof(c_long):
+            self.skipTest("sizes differ on this platform")
+        A = c_int * 3
+        B = c_long * 3
+        a = A(1, 2, 3)
+        a.__class__ = B
+
+    def test_ctypes_array_class_assignment_structs(self):
+        class S1(Structure):
+            _fields_ = [("x", c_int)]
+        class S2(Structure):
+            _fields_ = [("x", c_int)]
+        A = S1 * 2
+        B = S2 * 2
+        a = A()
+        a.__class__ = B
+
+    def test_ctypes_array_class_assignment_pointer_arrays(self):
+        A = POINTER(c_int) * 2
+        B = POINTER(c_int) * 2
+        a = A()
+        a.__class__ = B
+
+    def test_ctypes_array_from_param_incompatible(self):
+        A = c_int * 3
+        B = c_double * 3
+        with self.assertRaises(TypeError):
+            A.from_param(B())
+
     def test_step_overflow(self):
         a = (c_int * 5)()
         a[3::sys.maxsize] = (1,)

Modules/_ctypes/_ctypes.c

@@ -5041,17 +5041,22 @@ PyCArray_setattro(PyObject *self, PyObject *key, PyObject *value)
         }
 
         /* Only care about array to array */
-        if (old_info->length >= 0 && new_info->length >= 0) {
-            if (old_info->length != new_info->length ||
-                old_info->size != new_info->size ||
-                old_info->proto != new_info->proto)
-            {
-                PyErr_SetString(
-                    PyExc_TypeError,
-                    "cannot assign incompatible ctypes array type"
-                );
-                return -1;
-            }
+        if (old_info->length < 0 || new_info->length < 0) {
+            PyErr_SetString(
+                PyExc_TypeError,
+                "cannot assign incompatible ctypes array type");
+            return -1;
+        }
+
+        /* Must match layout */
+        if (old_info->length != new_info->length ||
+            old_info->size != new_info->size ||
+            old_info->proto != new_info->proto)
+        {
+            PyErr_SetString(
+                PyExc_TypeError,
+                "cannot assign incompatible ctypes array type");
+            return -1;
         }
     }