Issue #19023: Document ctypes array and pointer classes

Also add some more tests. Based on patch by Sye van der Veen.

2 files changed, 15 insertions, 6 deletions

diff --git a/Lib/ctypes/test/test_arrays.py b/Lib/ctypes/test/test_arrays.py
index 8ca77e0..4ed566b 100644
--- a/Lib/ctypes/test/test_arrays.py
+++ b/Lib/ctypes/test/test_arrays.py
@@ -24,20 +24,24 @@ class ArrayTestCase(unittest.TestCase):
             self.assertEqual(len(ia), alen)
 
             # slot values ok?
-            values = [ia[i] for i in range(len(init))]
+            values = [ia[i] for i in range(alen)]
             self.assertEqual(values, init)
 
+            # out-of-bounds accesses should be caught
+            with self.assertRaises(IndexError): ia[alen]
+            with self.assertRaises(IndexError): ia[-alen-1]
+
             # change the items
             from operator import setitem
             new_values = list(range(42, 42+alen))
             [setitem(ia, n, new_values[n]) for n in range(alen)]
-            values = [ia[i] for i in range(len(init))]
+            values = [ia[i] for i in range(alen)]
             self.assertEqual(values, new_values)
 
             # are the items initialized to 0?
             ia = int_array()
-            values = [ia[i] for i in range(len(init))]
-            self.assertEqual(values, [0] * len(init))
+            values = [ia[i] for i in range(alen)]
+            self.assertEqual(values, [0] * alen)
 
             # Too many initializers should be caught
             self.assertRaises(IndexError, int_array, *range(alen*2))
diff --git a/Lib/ctypes/test/test_pointers.py b/Lib/ctypes/test/test_pointers.py
index 225b9d1..751f85f 100644
--- a/Lib/ctypes/test/test_pointers.py
+++ b/Lib/ctypes/test/test_pointers.py
@@ -56,9 +56,13 @@ class PointersTestCase(unittest.TestCase):
         # C code:
         #   int x = 12321;
         #   res = &x
-        res.contents = c_int(12321)
+        x = c_int(12321)
+        res.contents = x
         self.assertEqual(i.value, 54345)
 
+        x.value = -99
+        self.assertEqual(res.contents.value, -99)
+
     def test_callbacks_with_pointers(self):
         # a function type receiving a pointer
         PROTOTYPE = CFUNCTYPE(c_int, POINTER(c_int))
@@ -131,9 +135,10 @@ class PointersTestCase(unittest.TestCase):
 
     def test_basic(self):
         p = pointer(c_int(42))
-        # Although a pointer can be indexed, it ha no length
+        # Although a pointer can be indexed, it has no length
         self.assertRaises(TypeError, len, p)
         self.assertEqual(p[0], 42)
+        self.assertEqual(p[0:1], [42])
         self.assertEqual(p.contents.value, 42)
 
     def test_charpp(self):