[3.15] gh-107689: add docstrings to abstract classes (GH-108882) (#159988)

gh-107689: add docstrings to abstract classes (GH-108882)
(cherry picked from commit 13a807a)

Co-authored-by: Martin Škopek <kiblik1@gmail.com>

Author: miss-islington

Misc/NEWS.d/next/Documentation/2023-09-04-16-01-20.gh-issue-107689.LFLFtG.rst

@@ -0,0 +1 @@
+Added docstrings to abstract ctypes.

Modules/_ctypes/_ctypes.c

@@ -5546,7 +5546,12 @@ Simple_repr(PyObject *self)
 
 static PyType_Slot pycsimple_slots[] = {
     {Py_tp_repr, &Simple_repr},
-    {Py_tp_doc, PyDoc_STR("XXX to be provided")},
+    {Py_tp_doc, PyDoc_STR("This non-public class is the base class of all "
+                          "fundamental ctypes data types.\n"
+                          "It contains the common attributes of the fundamental "
+                          "ctypes data types.\n"
+                          "_SimpleCData is a subclass of _CData, so it inherits "
+                          "their methods and attributes.")},
     {Py_tp_methods, Simple_methods},
     {Py_tp_getset, Simple_getsets},
     {Py_tp_init, Simple_init},
@@ -5987,7 +5992,19 @@ Pointer_bool(PyObject *self)
 }
 
 static PyType_Slot pycpointer_slots[] = {
-    {Py_tp_doc, (void *)PyDoc_STR("XXX to be provided")},
+    {Py_tp_doc, (void *)PyDoc_STR(
+                    "Private, abstract base class for pointers.\n"
+                    "\n"
+                    "Concrete pointer types are created by calling POINTER() "
+                    "with the type that will be pointed to; this is done "
+                    "automatically by pointer().\n"
+                    "\n"
+                    "If a pointer points to an array, its elements can be read "
+                    "and written using standard subscript and slice accesses. "
+                    "Pointer objects have no size, so len() will raise "
+                    "TypeError. Negative subscripts will read from the memory "
+                    "before the pointer (as in C), and out-of-range subscripts "
+                    "will probably crash with an access violation (if you’re lucky).")},
     {Py_tp_getset, Pointer_getsets},
     {Py_tp_init, Pointer_init},
     {Py_tp_new, Pointer_new},