Make int, long and float subclassable.

This uses a slightly wimpy and wasteful approach, but it works. :-)

Objects/floatobject.c

@@ -626,13 +626,17 @@ float_float(PyObject *v)
 }
 
 
+staticforward PyObject *
+float_subtype_new(PyTypeObject *type, PyObject *args, PyObject *kwds);
+
 static PyObject *
 float_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 {
 	PyObject *x = Py_False; /* Integer zero */
 	static char *kwlist[] = {"x", 0};
 
-	assert(type == &PyFloat_Type);
+	if (type != &PyFloat_Type)
+		return float_subtype_new(type, args, kwds); /* Wimp out */
 	if (!PyArg_ParseTupleAndKeywords(args, kwds, "|O:float", kwlist, &x))
 		return NULL;
 	if (PyString_Check(x))
@@ -640,6 +644,29 @@ float_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 	return PyNumber_Float(x);
 }
 
+/* Wimpy, slow approach to tp_new calls for subtypes of float:
+   first create a regular float from whatever arguments we got,
+   then allocate a subtype instance and initialize its ob_fval
+   from the regular float.  The regular float is then thrown away.
+*/
+static PyObject *
+float_subtype_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+	PyObject *tmp, *new;
+
+	assert(PyType_IsSubtype(type, &PyFloat_Type));
+	tmp = float_new(&PyFloat_Type, args, kwds);
+	if (tmp == NULL)
+		return NULL;
+	assert(PyFloat_Check(tmp));
+	new = type->tp_alloc(type, 0);;
+	if (new == NULL)
+		return NULL;
+	((PyFloatObject *)new)->ob_fval = ((PyFloatObject *)tmp)->ob_fval;
+	Py_DECREF(tmp);
+	return new;
+}
+
 static char float_doc[] =
 "float(x) -> floating point number\n\
 \n\
@@ -708,7 +735,8 @@ PyTypeObject PyFloat_Type = {
 	PyObject_GenericGetAttr,		/* tp_getattro */
 	0,					/* tp_setattro */
 	0,					/* tp_as_buffer */
-	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES, /* tp_flags */
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES |
+		Py_TPFLAGS_BASETYPE,		/* tp_flags */
 	float_doc,				/* tp_doc */
  	0,					/* tp_traverse */
 	0,					/* tp_clear */
@@ -750,7 +778,7 @@ PyFloat_Fini(void)
 		for (i = 0, p = &list->objects[0];
 		     i < N_FLOATOBJECTS;
 		     i++, p++) {
-			if (PyFloat_Check(p) && p->ob_refcnt != 0)
+			if (p->ob_type == &PyFloat_Type && p->ob_refcnt != 0)
 				frem++;
 		}
 		next = list->next;
@@ -760,7 +788,8 @@ PyFloat_Fini(void)
 			for (i = 0, p = &list->objects[0];
 			     i < N_FLOATOBJECTS;
 			     i++, p++) {
-				if (!PyFloat_Check(p) || p->ob_refcnt == 0) {
+				if (p->ob_type != &PyFloat_Type ||
+				    p->ob_refcnt == 0) {
 					p->ob_type = (struct _typeobject *)
 						free_list;
 					free_list = p;
@@ -792,7 +821,8 @@ PyFloat_Fini(void)
 			for (i = 0, p = &list->objects[0];
 			     i < N_FLOATOBJECTS;
 			     i++, p++) {
-				if (PyFloat_Check(p) && p->ob_refcnt != 0) {
+				if (p->ob_type == &PyFloat_Type &&
+				    p->ob_refcnt != 0) {
 					char buf[100];
 					PyFloat_AsString(buf, p);
 					fprintf(stderr,

Objects/intobject.c

@@ -134,8 +134,12 @@ PyInt_FromLong(long ival)
 static void
 int_dealloc(PyIntObject *v)
 {
+	if (v->ob_type == &PyInt_Type) {
 		v->ob_type = (struct _typeobject *)free_list;
 		free_list = v;
+	}
+	else
+		v->ob_type->tp_free((PyObject *)v);
 }
 
 long
@@ -783,6 +787,9 @@ int_hex(PyIntObject *v)
 	return PyString_FromString(buf);
 }
 
+staticforward PyObject *
+int_subtype_new(PyTypeObject *type, PyObject *args, PyObject *kwds);
+
 static PyObject *
 int_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 {
@@ -790,7 +797,8 @@ int_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 	int base = -909;
 	static char *kwlist[] = {"x", "base", 0};
 
-	assert(type == &PyInt_Type);
+	if (type != &PyInt_Type)
+		return int_subtype_new(type, args, kwds); /* Wimp out */
 	if (!PyArg_ParseTupleAndKeywords(args, kwds, "|Oi:int", kwlist,
 					 &x, &base))
 		return NULL;
@@ -811,6 +819,29 @@ int_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 	return NULL;
 }
 
+/* Wimpy, slow approach to tp_new calls for subtypes of int:
+   first create a regular int from whatever arguments we got,
+   then allocate a subtype instance and initialize its ob_ival
+   from the regular int.  The regular int is then thrown away.
+*/
+static PyObject *
+int_subtype_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+	PyObject *tmp, *new;
+
+	assert(PyType_IsSubtype(type, &PyInt_Type));
+	tmp = int_new(&PyInt_Type, args, kwds);
+	if (tmp == NULL)
+		return NULL;
+	assert(PyInt_Check(tmp));
+	new = type->tp_alloc(type, 0);;
+	if (new == NULL)
+		return NULL;
+	((PyIntObject *)new)->ob_ival = ((PyIntObject *)tmp)->ob_ival;
+	Py_DECREF(tmp);
+	return new;
+}
+
 static char int_doc[] =
 "int(x[, base]) -> integer\n\
 \n\
@@ -882,7 +913,8 @@ PyTypeObject PyInt_Type = {
 	PyObject_GenericGetAttr,		/* tp_getattro */
 	0,					/* tp_setattro */
 	0,					/* tp_as_buffer */
-	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES, /* tp_flags */
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES |
+		Py_TPFLAGS_BASETYPE,		/* tp_flags */
 	int_doc,				/* tp_doc */
 	0,					/* tp_traverse */
 	0,					/* tp_clear */
@@ -934,7 +966,7 @@ PyInt_Fini(void)
 		for (i = 0, p = &list->objects[0];
 		     i < N_INTOBJECTS;
 		     i++, p++) {
-			if (PyInt_Check(p) && p->ob_refcnt != 0)
+			if (p->ob_type == &PyInt_Type && p->ob_refcnt != 0)
 				irem++;
 		}
 		next = list->next;
@@ -944,7 +976,8 @@ PyInt_Fini(void)
 			for (i = 0, p = &list->objects[0];
 			     i < N_INTOBJECTS;
 			     i++, p++) {
-				if (!PyInt_Check(p) || p->ob_refcnt == 0) {
+				if (p->ob_type != &PyInt_Type ||
+				    p->ob_refcnt == 0) {
 					p->ob_type = (struct _typeobject *)
 						free_list;
 					free_list = p;
@@ -986,7 +1019,7 @@ PyInt_Fini(void)
 			for (i = 0, p = &list->objects[0];
 			     i < N_INTOBJECTS;
 			     i++, p++) {
-				if (PyInt_Check(p) && p->ob_refcnt != 0)
+				if (p->ob_type == &PyInt_Type && p->ob_refcnt != 0)
 					fprintf(stderr,
 				"#   <int at %p, refcnt=%d, val=%ld>\n",
 						p, p->ob_refcnt, p->ob_ival);

Objects/longobject.c

@@ -2038,6 +2038,8 @@ long_hex(PyObject *v)
 {
 	return long_format(v, 16, 1);
 }
+staticforward PyObject *
+long_subtype_new(PyTypeObject *type, PyObject *args, PyObject *kwds);
 
 static PyObject *
 long_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
@@ -2046,7 +2048,8 @@ long_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 	int base = -909;		     /* unlikely! */
 	static char *kwlist[] = {"x", "base", 0};
 
-	assert(type == &PyLong_Type);
+	if (type != &PyLong_Type)
+		return long_subtype_new(type, args, kwds); /* Wimp out */
 	if (!PyArg_ParseTupleAndKeywords(args, kwds, "|Oi:long", kwlist,
 					 &x, &base))
 		return NULL;
@@ -2069,6 +2072,36 @@ long_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 	}
 }
 
+/* Wimpy, slow approach to tp_new calls for subtypes of long:
+   first create a regular long from whatever arguments we got,
+   then allocate a subtype instance and initialize it from
+   the regular long.  The regular long is then thrown away.
+*/
+static PyObject *
+long_subtype_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+	PyLongObject *tmp, *new;
+	int i, n;
+
+	assert(PyType_IsSubtype(type, &PyLong_Type));
+	tmp = (PyLongObject *)long_new(&PyLong_Type, args, kwds);
+	if (tmp == NULL)
+		return NULL;
+	assert(PyLong_Check(tmp));
+	n = tmp->ob_size;
+	if (n < 0)
+		n = -n;
+	new = (PyLongObject *)type->tp_alloc(type, n);
+	if (new == NULL)
+		return NULL;
+	assert(PyLong_Check(new));
+	new->ob_size = type->ob_size;
+	for (i = 0; i < n; i++)
+		new->ob_digit[i] = tmp->ob_digit[i];
+	Py_DECREF(tmp);
+	return (PyObject *)new;
+}
+
 static char long_doc[] =
 "long(x[, base]) -> integer\n\
 \n\
@@ -2140,7 +2173,8 @@ PyTypeObject PyLong_Type = {
 	PyObject_GenericGetAttr,		/* tp_getattro */
 	0,					/* tp_setattro */
 	0,					/* tp_as_buffer */
-	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES, /* tp_flags */
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES |
+		Py_TPFLAGS_BASETYPE,		/* tp_flags */
 	long_doc,				/* tp_doc */
 	0,					/* tp_traverse */
 	0,					/* tp_clear */