Issue #4129: Belatedly document which C API functions had their argument(s) or
return type changed from int or int * to Py_ssize_t or Py_ssize_t * as this
might cause problems on 64-bit platforms.
diff --git a/Doc/c-api/mapping.rst b/Doc/c-api/mapping.rst
index cff0759..78787e3 100644
--- a/Doc/c-api/mapping.rst
+++ b/Doc/c-api/mapping.rst
@@ -12,7 +12,8 @@
    function always succeeds.
 
 
-.. cfunction:: Py_ssize_t PyMapping_Length(PyObject *o)
+.. cfunction:: Py_ssize_t PyMapping_Size(PyObject *o)
+               Py_ssize_t PyMapping_Length(PyObject *o)
 
    .. index:: builtin: len
 
@@ -20,6 +21,10 @@
    objects that do not provide mapping protocol, this is equivalent to the Python
    expression ``len(o)``.
 
+   .. versionchanged:: 2.5
+      These functions returned an :ctype:`int` type. This might require
+      changes in your code for properly supporting 64-bit systems.
+
 
 .. cfunction:: int PyMapping_DelItemString(PyObject *o, char *key)