gh-153903: wrap_dll_function: copy doc, etc from wrapped stub

Doc/library/ctypes.rst

@@ -708,6 +708,7 @@ Specifying function pointers using type annotations
 
       @wrap_dll_function(dll_to_wrap)
       def function_ptr_name(arg_name: ctypes_type, ...) -> ctypes_type:
+         """Optional docstring."""
          # There should be no body
          pass
 

Lib/ctypes/util.py

@@ -590,6 +590,8 @@ def decorator(func):
 
         ptr.restype = restype
         ptr.argtypes = tuple(annotations.values())
+        functools.update_wrapper(ptr, func, updated=())
+
         return ptr
 
     return decorator

Lib/test/test_ctypes/test_funcptr.py

@@ -134,12 +134,14 @@ def test_abstract(self):
     def test_wrap_dll_function(self):
         @wrap_dll_function(ctypes.pythonapi)
         def PyObject_GetAttr(op: ctypes.py_object, attr: ctypes.py_object) -> ctypes.py_object:
+            """Call the PythonAPI function underlying getattr"""
             pass
 
         class Foo:
             a = "abc"
 
         self.assertEqual(PyObject_GetAttr(Foo, "a"), "abc")
+        self.assertEqual(PyObject_GetAttr.__doc__, "Call the PythonAPI function underlying getattr")
 
         with self.assertRaises(AttributeError):
             @wrap_dll_function(ctypes.pythonapi)