Index: ctypes/test/test_parameters.py
===================================================================
RCS file: /cvsroot/ctypes/ctypes/ctypes/test/test_parameters.py,v
retrieving revision 1.3
diff -u -r1.3 test_parameters.py
--- ctypes/test/test_parameters.py	14 Mar 2006 19:09:21 -0000	1.3
+++ ctypes/test/test_parameters.py	5 Jul 2006 20:16:37 -0000
@@ -147,6 +147,41 @@
 ##    def test_performance(self):
 ##        check_perf()
 
+    def test_noctypes_argtype(self):
+        import _ctypes_test
+        from ctypes import CDLL, c_void_p, ArgumentError
+
+        func = CDLL(_ctypes_test.__file__)._testfunc_p_p
+        func.restype = c_void_p
+        # TypeError: has no from_param method
+        self.assertRaises(TypeError, setattr, func, "argtypes", (object,))
+
+        class Adapter(object):
+            def from_param(cls, obj):
+                return None
+
+        func.argtypes = (Adapter(),)
+        self.failUnlessEqual(func(None), None)
+        self.failUnlessEqual(func(object()), None)
+
+        class Adapter(object):
+            def from_param(cls, obj):
+                return obj
+
+        func.argtypes = (Adapter(),)
+        # don't know how to convert parameter 1
+        self.assertRaises(ArgumentError, func, object())
+        self.failUnlessEqual(func(c_void_p(42)), 42)
+
+        class Adapter(object):
+            def from_param(cls, obj):
+                raise ValueError(obj)
+
+        func.argtypes = (Adapter(),)
+        # ArgumentError: argument 1: ValueError: 99
+        self.assertRaises(ArgumentError, func, 99)
+
+
 ################################################################
 
 if __name__ == '__main__':
Index: docs/manual/reference.txt
===================================================================
RCS file: /cvsroot/ctypes/ctypes/docs/manual/reference.txt,v
retrieving revision 1.43
diff -u -r1.43 reference.txt
--- docs/manual/reference.txt	3 Jul 2006 14:29:12 -0000	1.43
+++ docs/manual/reference.txt	5 Jul 2006 20:20:15 -0000
@@ -231,6 +231,12 @@
     convert a unicode string passed as argument into an byte string
     using ctypes conversion rules.
 
+    New: It is now possible to put items in argtypes which are not
+    ctypes types, but each item must have a ``from_param`` method
+    which returns a value usable as argument (integer, string, ctypes
+    instance).  This allows to define adapters that can adapt custom
+    objects as function parameters.
+
 ``errcheck`` : memberdesc
     Assign a Python function or another callable to this attribute.
     The callable will be called with three or more arguments:
Index: source/_ctypes.c
===================================================================
RCS file: /cvsroot/ctypes/ctypes/source/_ctypes.c,v
retrieving revision 1.341
diff -u -r1.341 _ctypes.c
--- source/_ctypes.c	5 Jul 2006 08:32:33 -0000	1.341
+++ source/_ctypes.c	5 Jul 2006 20:01:59 -0000
@@ -1633,9 +1633,8 @@
 
 	for (i = 0; i < nArgs; ++i) {
 		PyObject *tp = PyTuple_GET_ITEM(ob, i);
-		StgDictObject *dict = PyType_stgdict(tp);
 		PyObject *cnv = PyObject_GetAttrString(tp, "from_param");
-		if (!dict || !cnv)
+		if (!cnv)
 			goto argtypes_error_1;
 		PyTuple_SET_ITEM(converters, i, cnv);
 	}
@@ -1646,7 +1645,7 @@
 	Py_XDECREF(converters);
 	Py_DECREF(ob);
 	PyErr_Format(PyExc_TypeError,
-		     "item %d in _argtypes_ is not a valid C type", i+1);
+		     "item %d in _argtypes_ has no from_param method", i+1);
 	return NULL;
 }