[3.13] gh-92347: Document pitfalls of ctypes.pointer iteration (GH-157801) (GH-157927)

(cherry picked from commit a3e389d)

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

Author: miss-islington

Doc/library/ctypes.rst

@@ -835,6 +835,15 @@ Generally you only use this feature if you receive a pointer from a C function,
 and you *know* that the pointer actually points to an array instead of a single
 item.
 
+.. warning::
+
+   Because pointer objects support subscription, they implicitly support
+   :term:`iteration <iterator>`. Unless doing this in a controlled manner,
+   such as by manually calling :func:`next` on a :func:`pointer` iterator, this
+   will typically lead to infinite loops or crashes, because ctypes has no way
+   of knowing when to stop iteration. In other words, a ``pointer`` iterator
+   will infinitely yield arbitrary memory.
+
 Behind the scenes, the :func:`pointer` function does more than simply create
 pointer instances, it has to create pointer *types* first. This is done with the
 :func:`POINTER` function, which accepts any :mod:`ctypes` type, and returns a