Objects/classobject.c

/* Class object implementation */

#include "Python.h"
#include "structmember.h"

/* Free list for method objects to save malloc/free overhead
 * The im_self element is used to chain the elements.
 */
static PyMethodObject *free_list;
static int numfree = 0;
#ifndef PyMethod_MAXFREELIST
#define PyMethod_MAXFREELIST 256
#endif

#define TP_DESCR_GET(t) \
    (PyType_HasFeature(t, Py_TPFLAGS_HAVE_CLASS) ? (t)->tp_descr_get : NULL)

/* Forward */
static PyObject *class_lookup(PyClassObject *, PyObject *,
                              PyClassObject **);
static PyObject *instance_getattr1(PyInstanceObject *, PyObject *);
static PyObject *instance_getattr2(PyInstanceObject *, PyObject *);

static PyObject *getattrstr, *setattrstr, *delattrstr;


PyObject *
PyClass_New(PyObject *bases, PyObject *dict, PyObject *name)
     /* bases is NULL or tuple of classobjects! */
{
    PyClassObject *op, *dummy;
    static PyObject *docstr, *modstr, *namestr;
    if (docstr == NULL) {
        docstr= PyString_InternFromString("__doc__");
        if (docstr == NULL)
            return NULL;
    }
    if (modstr == NULL) {
        modstr= PyString_InternFromString("__module__");
        if (modstr == NULL)
            return NULL;
    }
    if (namestr == NULL) {
        namestr= PyString_InternFromString("__name__");
        if (namestr == NULL)
            return NULL;
    }
    if (name == NULL || !PyString_Check(name)) {
        PyErr_SetString(PyExc_TypeError,
                        "PyClass_New: name must be a string");
        return NULL;
    }
    if (dict == NULL || !PyDict_Check(dict)) {
        PyErr_SetString(PyExc_TypeError,
                        "PyClass_New: dict must be a dictionary");
        return NULL;
    }
    if (PyDict_GetItem(dict, docstr) == NULL) {
        if (PyDict_SetItem(dict, docstr, Py_None) < 0)
            return NULL;
    }
    if (PyDict_GetItem(dict, modstr) == NULL) {
        PyObject *globals = PyEval_GetGlobals();
        if (globals != NULL) {
            PyObject *modname = PyDict_GetItem(globals, namestr);
            if (modname != NULL) {
                if (PyDict_SetItem(dict, modstr, modname) < 0)
                    return NULL;
            }
        }
    }
    if (bases == NULL) {
        bases = PyTuple_New(0);
        if (bases == NULL)
            return NULL;
    }
    else {
        Py_ssize_t i, n;
        PyObject *base;
        if (!PyTuple_Check(bases)) {
            PyErr_SetString(PyExc_TypeError,
                            "PyClass_New: bases must be a tuple");
            return NULL;
        }
        n = PyTuple_Size(bases);
        for (i = 0; i < n; i++) {
            base = PyTuple_GET_ITEM(bases, i);
            if (!PyClass_Check(base)) {
                if (PyCallable_Check(
                    (PyObject *) base->ob_type))
                    return PyObject_CallFunctionObjArgs(
                        (PyObject *) base->ob_type,
                        name, bases, dict, NULL);
                PyErr_SetString(PyExc_TypeError,
                    "PyClass_New: base must be a class");
                return NULL;
            }
        }
        Py_INCREF(bases);
    }

    if (getattrstr == NULL) {
        getattrstr = PyString_InternFromString("__getattr__");
        if (getattrstr == NULL)
            goto alloc_error;
        setattrstr = PyString_InternFromString("__setattr__");
        if (setattrstr == NULL)
            goto alloc_error;
        delattrstr = PyString_InternFromString("__delattr__");
        if (delattrstr == NULL)
            goto alloc_error;
    }

    op = PyObject_GC_New(PyClassObject, &PyClass_Type);
    if (op == NULL) {
alloc_error:
        Py_DECREF(bases);
        return NULL;
    }
    op->cl_bases = bases;
    Py_INCREF(dict);
    op->cl_dict = dict;
    Py_XINCREF(name);
    op->cl_name = name;
    op->cl_weakreflist = NULL;

    op->cl_getattr = class_lookup(op, getattrstr, &dummy);
    op->cl_setattr = class_lookup(op, setattrstr, &dummy);
    op->cl_delattr = class_lookup(op, delattrstr, &dummy);
    Py_XINCREF(op->cl_getattr);
    Py_XINCREF(op->cl_setattr);
    Py_XINCREF(op->cl_delattr);
    _PyObject_GC_TRACK(op);
    return (PyObject *) op;
}

PyObject *
PyMethod_Function(PyObject *im)
{
    if (!PyMethod_Check(im)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyMethodObject *)im)->im_func;
}

PyObject *
PyMethod_Self(PyObject *im)
{
    if (!PyMethod_Check(im)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyMethodObject *)im)->im_self;
}

PyObject *
PyMethod_Class(PyObject *im)
{
    if (!PyMethod_Check(im)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyMethodObject *)im)->im_class;
}

PyDoc_STRVAR(class_doc,
"classobj(name, bases, dict)\n\
\n\
Create a class object.  The name must be a string; the second argument\n\
a tuple of classes, and the third a dictionary.");

static PyObject *
class_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
    PyObject *name, *bases, *dict;
    static char *kwlist[] = {"name", "bases", "dict", 0};

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "SOO", kwlist,
                                     &name, &bases, &dict))
        return NULL;
    return PyClass_New(bases, dict, name);
}

/* Class methods */

static void
class_dealloc(PyClassObject *op)
{
    _PyObject_GC_UNTRACK(op);
    if (op->cl_weakreflist != NULL)
        PyObject_ClearWeakRefs((PyObject *) op);
    Py_DECREF(op->cl_bases);
    Py_DECREF(op->cl_dict);
    Py_XDECREF(op->cl_name);
    Py_XDECREF(op->cl_getattr);
    Py_XDECREF(op->cl_setattr);
    Py_XDECREF(op->cl_delattr);
    PyObject_GC_Del(op);
}

static PyObject *
class_lookup(PyClassObject *cp, PyObject *name, PyClassObject **pclass)
{
    Py_ssize_t i, n;
    PyObject *value = PyDict_GetItem(cp->cl_dict, name);
    if (value != NULL) {
        *pclass = cp;
        return value;
    }
    n = PyTuple_Size(cp->cl_bases);
    for (i = 0; i < n; i++) {
        /* XXX What if one of the bases is not a class? */
        PyObject *v = class_lookup(
            (PyClassObject *)
            PyTuple_GetItem(cp->cl_bases, i), name, pclass);
        if (v != NULL)
            return v;
    }
    return NULL;
}

static PyObject *
class_getattr(register PyClassObject *op, PyObject *name)
{
    register PyObject *v;
    register char *sname;
    PyClassObject *klass;
    descrgetfunc f;

    if (!PyString_Check(name)) {
        PyErr_SetString(PyExc_TypeError, "attribute name must be a string");
        return NULL;
    }

    sname = PyString_AsString(name);
    if (sname[0] == '_' && sname[1] == '_') {
        if (strcmp(sname, "__dict__") == 0) {
            if (PyEval_GetRestricted()) {
                PyErr_SetString(PyExc_RuntimeError,
               "class.__dict__ not accessible in restricted mode");
                return NULL;
            }
            Py_INCREF(op->cl_dict);
            return op->cl_dict;
        }
        if (strcmp(sname, "__bases__") == 0) {
            Py_INCREF(op->cl_bases);
            return op->cl_bases;
        }
        if (strcmp(sname, "__name__") == 0) {
            if (op->cl_name == NULL)
                v = Py_None;
            else
                v = op->cl_name;
            Py_INCREF(v);
            return v;
        }
    }
    v = class_lookup(op, name, &klass);
    if (v == NULL) {
        PyErr_Format(PyExc_AttributeError,
                     "class %.50s has no attribute '%.400s'",
                     PyString_AS_STRING(op->cl_name), sname);
        return NULL;
    }
    f = TP_DESCR_GET(v->ob_type);
    if (f == NULL)
        Py_INCREF(v);
    else
        v = f(v, (PyObject *)NULL, (PyObject *)op);
    return v;
}

static void
set_slot(PyObject **slot, PyObject *v)
{
    PyObject *temp = *slot;
    Py_XINCREF(v);
    *slot = v;
    Py_XDECREF(temp);
}

static void
set_attr_slots(PyClassObject *c)
{
    PyClassObject *dummy;

    set_slot(&c->cl_getattr, class_lookup(c, getattrstr, &dummy));
    set_slot(&c->cl_setattr, class_lookup(c, setattrstr, &dummy));
    set_slot(&c->cl_delattr, class_lookup(c, delattrstr, &dummy));
}

static char *
set_dict(PyClassObject *c, PyObject *v)
{
    if (v == NULL || !PyDict_Check(v))
        return "__dict__ must be a dictionary object";
    set_slot(&c->cl_dict, v);
    set_attr_slots(c);
    return "";
}

static char *
set_bases(PyClassObject *c, PyObject *v)
{
    Py_ssize_t i, n;

    if (v == NULL || !PyTuple_Check(v))
        return "__bases__ must be a tuple object";
    n = PyTuple_Size(v);
    for (i = 0; i < n; i++) {
        PyObject *x = PyTuple_GET_ITEM(v, i);
        if (!PyClass_Check(x))
            return "__bases__ items must be classes";
        if (PyClass_IsSubclass(x, (PyObject *)c))
            return "a __bases__ item causes an inheritance cycle";
    }
    set_slot(&c->cl_bases, v);
    set_attr_slots(c);
    return "";
}

static char *
set_name(PyClassObject *c, PyObject *v)
{
    if (v == NULL || !PyString_Check(v))
        return "__name__ must be a string object";
    if (strlen(PyString_AS_STRING(v)) != (size_t)PyString_GET_SIZE(v))
        return "__name__ must not contain null bytes";
    set_slot(&c->cl_name, v);
    return "";
}

static int
class_setattr(PyClassObject *op, PyObject *name, PyObject *v)
{
    char *sname;
    if (PyEval_GetRestricted()) {
        PyErr_SetString(PyExc_RuntimeError,
                   "classes are read-only in restricted mode");
        return -1;
    }
    if (!PyString_Check(name)) {
        PyErr_SetString(PyExc_TypeError, "attribute name must be a string");
        return -1;
    }
    sname = PyString_AsString(name);
    if (sname[0] == '_' && sname[1] == '_') {
        Py_ssize_t n = PyString_Size(name);
        if (sname[n-1] == '_' && sname[n-2] == '_') {
            char *err = NULL;
            if (strcmp(sname, "__dict__") == 0)
                err = set_dict(op, v);
            else if (strcmp(sname, "__bases__") == 0)
                err = set_bases(op, v);
            else if (strcmp(sname, "__name__") == 0)
                err = set_name(op, v);
            else if (strcmp(sname, "__getattr__") == 0)
                set_slot(&op->cl_getattr, v);
            else if (strcmp(sname, "__setattr__") == 0)
                set_slot(&op->cl_setattr, v);
            else if (strcmp(sname, "__delattr__") == 0)
                set_slot(&op->cl_delattr, v);
            /* For the last three, we fall through to update the
               dictionary as well. */
            if (err != NULL) {
                if (*err == '\0')
                    return 0;
                PyErr_SetString(PyExc_TypeError, err);
                return -1;
            }
        }
    }
    if (v == NULL) {
        int rv = PyDict_DelItem(op->cl_dict, name);
        if (rv < 0)
            PyErr_Format(PyExc_AttributeError,
                         "class %.50s has no attribute '%.400s'",
                         PyString_AS_STRING(op->cl_name), sname);
        return rv;
    }
    else
        return PyDict_SetItem(op->cl_dict, name, v);
}

static PyObject *
class_repr(PyClassObject *op)
{
    PyObject *mod = PyDict_GetItemString(op->cl_dict, "__module__");
    char *name;
    if (op->cl_name == NULL || !PyString_Check(op->cl_name))
        name = "?";
    else
        name = PyString_AsString(op->cl_name);
    if (mod == NULL || !PyString_Check(mod))
        return PyString_FromFormat("<class ?.%s at %p>", name, op);
    else
        return PyString_FromFormat("<class %s.%s at %p>",
                                   PyString_AsString(mod),
                                   name, op);
}

static PyObject *
class_str(PyClassObject *op)
{
    PyObject *mod = PyDict_GetItemString(op->cl_dict, "__module__");
    PyObject *name = op->cl_name;
    PyObject *res;
    Py_ssize_t m, n;

    if (name == NULL || !PyString_Check(name))
        return class_repr(op);
    if (mod == NULL || !PyString_Check(mod)) {
        Py_INCREF(name);
        return name;
    }
    m = PyString_GET_SIZE(mod);
    n = PyString_GET_SIZE(name);
    res = PyString_FromStringAndSize((char *)NULL, m+1+n);
    if (res != NULL) {
        char *s = PyString_AS_STRING(res);
        memcpy(s, PyString_AS_STRING(mod), m);
        s += m;
        *s++ = '.';
        memcpy(s, PyString_AS_STRING(name), n);
    }
    return res;
}

static int
class_traverse(PyClassObject *o, visitproc visit, void *arg)
{
    Py_VISIT(o->cl_bases);
    Py_VISIT(o->cl_dict);
    Py_VISIT(o->cl_name);
    Py_VISIT(o->cl_getattr);
    Py_VISIT(o->cl_setattr);
    Py_VISIT(o->cl_delattr);
    return 0;
}

PyTypeObject PyClass_Type = {
    PyObject_HEAD_INIT(&PyType_Type)
    0,
    "classobj",
    sizeof(PyClassObject),
    0,
    (destructor)class_dealloc,                  /* tp_dealloc */
    0,                                          /* tp_print */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    0,                                          /* tp_compare */
    (reprfunc)class_repr,                       /* tp_repr */
    0,                                          /* tp_as_number */
    0,                                          /* tp_as_sequence */
    0,                                          /* tp_as_mapping */
    0,                                          /* tp_hash */
    PyInstance_New,                             /* tp_call */
    (reprfunc)class_str,                        /* tp_str */
    (getattrofunc)class_getattr,                /* tp_getattro */
    (setattrofunc)class_setattr,                /* tp_setattro */
    0,                                          /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
    class_doc,                                  /* tp_doc */
    (traverseproc)class_traverse,               /* tp_traverse */
    0,                                          /* tp_clear */
    0,                                          /* tp_richcompare */
    offsetof(PyClassObject, cl_weakreflist), /* tp_weaklistoffset */
    0,                                          /* tp_iter */
    0,                                          /* tp_iternext */
    0,                                          /* tp_methods */
    0,                                          /* tp_members */
    0,                                          /* tp_getset */
    0,                                          /* tp_base */
    0,                                          /* tp_dict */
    0,                                          /* tp_descr_get */
    0,                                          /* tp_descr_set */
    0,                                          /* tp_dictoffset */
    0,                                          /* tp_init */
    0,                                          /* tp_alloc */
    class_new,                                  /* tp_new */
};

int
PyClass_IsSubclass(PyObject *klass, PyObject *base)
{
    Py_ssize_t i, n;
    PyClassObject *cp;
    if (klass == base)
        return 1;
    if (PyTuple_Check(base)) {
        n = PyTuple_GET_SIZE(base);
        for (i = 0; i < n; i++) {
            if (PyClass_IsSubclass(klass, PyTuple_GET_ITEM(base, i)))
                return 1;
        }
        return 0;
    }
    if (klass == NULL || !PyClass_Check(klass))
        return 0;
    cp = (PyClassObject *)klass;
    n = PyTuple_Size(cp->cl_bases);
    for (i = 0; i < n; i++) {
        if (PyClass_IsSubclass(PyTuple_GetItem(cp->cl_bases, i), base))
            return 1;
    }
    return 0;
}


/* Instance objects */

PyObject *
PyInstance_NewRaw(PyObject *klass, PyObject *dict)
{
    PyInstanceObject *inst;

    if (!PyClass_Check(klass)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    if (dict == NULL) {
        dict = PyDict_New();
        if (dict == NULL)
            return NULL;
    }
    else {
        if (!PyDict_Check(dict)) {
            PyErr_BadInternalCall();
            return NULL;
        }
        Py_INCREF(dict);
    }
    inst = PyObject_GC_New(PyInstanceObject, &PyInstance_Type);
    if (inst == NULL) {
        Py_DECREF(dict);
        return NULL;
    }
    inst->in_weakreflist = NULL;
    Py_INCREF(klass);
    inst->in_class = (PyClassObject *)klass;
    inst->in_dict = dict;
    _PyObject_GC_TRACK(inst);
    return (PyObject *)inst;
}

PyObject *
PyInstance_New(PyObject *klass, PyObject *arg, PyObject *kw)
{
    register PyInstanceObject *inst;
    PyObject *init;
    static PyObject *initstr;

    if (initstr == NULL) {
        initstr = PyString_InternFromString("__init__");
        if (initstr == NULL)
            return NULL;
    }
    inst = (PyInstanceObject *) PyInstance_NewRaw(klass, NULL);
    if (inst == NULL)
        return NULL;
    init = instance_getattr2(inst, initstr);
    if (init == NULL) {
        if (PyErr_Occurred()) {
            Py_DECREF(inst);
            return NULL;
        }
        if ((arg != NULL && (!PyTuple_Check(arg) ||
                             PyTuple_Size(arg) != 0))
            || (kw != NULL && (!PyDict_Check(kw) ||
                              PyDict_Size(kw) != 0))) {
            PyErr_SetString(PyExc_TypeError,
                       "this constructor takes no arguments");
            Py_DECREF(inst);
            inst = NULL;
        }
    }
    else {
        PyObject *res = PyEval_CallObjectWithKeywords(init, arg, kw);
        Py_DECREF(init);
        if (res == NULL) {
            Py_DECREF(inst);
            inst = NULL;
        }
        else {
            if (res != Py_None) {
                PyErr_SetString(PyExc_TypeError,
                           "__init__() should return None");
                Py_DECREF(inst);
                inst = NULL;
            }
            Py_DECREF(res);
        }
    }
    return (PyObject *)inst;
}

/* Instance methods */

PyDoc_STRVAR(instance_doc,
"instance(class[, dict])\n\
\n\
Create an instance without calling its __init__() method.\n\
The class must be a classic class.\n\
If present, dict must be a dictionary or None.");

static PyObject *
instance_new(PyTypeObject* type, PyObject* args, PyObject *kw)
{
    PyObject *klass;
    PyObject *dict = Py_None;

    if (!PyArg_ParseTuple(args, "O!|O:instance",
                          &PyClass_Type, &klass, &dict))
        return NULL;

    if (dict == Py_None)
        dict = NULL;
    else if (!PyDict_Check(dict)) {
        PyErr_SetString(PyExc_TypeError,
              "instance() second arg must be dictionary or None");
        return NULL;
    }
    return PyInstance_NewRaw(klass, dict);
}


static void
instance_dealloc(register PyInstanceObject *inst)
{
    PyObject *error_type, *error_value, *error_traceback;
    PyObject *del;
    static PyObject *delstr;

    _PyObject_GC_UNTRACK(inst);
    if (inst->in_weakreflist != NULL)
        PyObject_ClearWeakRefs((PyObject *) inst);

    /* Temporarily resurrect the object. */
    assert(inst->ob_type == &PyInstance_Type);
    assert(inst->ob_refcnt == 0);
    inst->ob_refcnt = 1;

    /* Save the current exception, if any. */
    PyErr_Fetch(&error_type, &error_value, &error_traceback);
    /* Execute __del__ method, if any. */
    if (delstr == NULL) {
        delstr = PyString_InternFromString("__del__");
        if (delstr == NULL)
            PyErr_WriteUnraisable((PyObject*)inst);
    }
    if (delstr && (del = instance_getattr2(inst, delstr)) != NULL) {
        PyObject *res = PyEval_CallObject(del, (PyObject *)NULL);
        if (res == NULL)
            PyErr_WriteUnraisable(del);
        else
            Py_DECREF(res);
        Py_DECREF(del);
    }
    /* Restore the saved exception. */
    PyErr_Restore(error_type, error_value, error_traceback);

    /* Undo the temporary resurrection; can't use DECREF here, it would
     * cause a recursive call.
     */
    assert(inst->ob_refcnt > 0);
    if (--inst->ob_refcnt == 0) {

        /* New weakrefs could be created during the finalizer call.
            If this occurs, clear them out without calling their
            finalizers since they might rely on part of the object
            being finalized that has already been destroyed. */
        while (inst->in_weakreflist != NULL) {
            _PyWeakref_ClearRef((PyWeakReference *)
                                (inst->in_weakreflist));
        }

        Py_DECREF(inst->in_class);
        Py_XDECREF(inst->in_dict);
        PyObject_GC_Del(inst);
    }
    else {
        Py_ssize_t refcnt = inst->ob_refcnt;
        /* __del__ resurrected it!  Make it look like the original
         * Py_DECREF never happened.
         */
        _Py_NewReference((PyObject *)inst);
        inst->ob_refcnt = refcnt;
        _PyObject_GC_TRACK(inst);
        /* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
         * we need to undo that. */
        _Py_DEC_REFTOTAL;
        /* If Py_TRACE_REFS, _Py_NewReference re-added self to the
         * object chain, so no more to do there.
         * If COUNT_ALLOCS, the original decref bumped tp_frees, and
         * _Py_NewReference bumped tp_allocs: both of those need to be
         * undone.
         */
#ifdef COUNT_ALLOCS
        --inst->ob_type->tp_frees;
        --inst->ob_type->tp_allocs;
#endif
    }
}

static PyObject *
instance_getattr1(register PyInstanceObject *inst, PyObject *name)
{
    register PyObject *v;
    register char *sname;

    if (!PyString_Check(name)) {
        PyErr_SetString(PyExc_TypeError, "attribute name must be a string");
        return NULL;
    }

    sname = PyString_AsString(name);
    if (sname[0] == '_' && sname[1] == '_') {
        if (strcmp(sname, "__dict__") == 0) {
            if (PyEval_GetRestricted()) {
                PyErr_SetString(PyExc_RuntimeError,
            "instance.__dict__ not accessible in restricted mode");
                return NULL;
            }
            Py_INCREF(inst->in_dict);
            return inst->in_dict;
        }
        if (strcmp(sname, "__class__") == 0) {
            Py_INCREF(inst->in_class);
            return (PyObject *)inst->in_class;
        }
    }
    v = instance_getattr2(inst, name);
    if (v == NULL && !PyErr_Occurred()) {
        PyErr_Format(PyExc_AttributeError,
                     "%.50s instance has no attribute '%.400s'",
                     PyString_AS_STRING(inst->in_class->cl_name), sname);
    }
    return v;
}

static PyObject *
instance_getattr2(register PyInstanceObject *inst, PyObject *name)
{
    register PyObject *v;
    PyClassObject *klass;
    descrgetfunc f;

    v = PyDict_GetItem(inst->in_dict, name);
    if (v != NULL) {
        Py_INCREF(v);
        return v;
    }
    v = class_lookup(inst->in_class, name, &klass);
    if (v != NULL) {
        Py_INCREF(v);
        f = TP_DESCR_GET(v->ob_type);
        if (f != NULL) {
            PyObject *w = f(v, (PyObject *)inst,
                            (PyObject *)(inst->in_class));
            Py_DECREF(v);
            v = w;
        }
    }
    return v;
}

static PyObject *
instance_getattr(register PyInstanceObject *inst, PyObject *name)
{
    register PyObject *func, *res;
    res = instance_getattr1(inst, name);
    if (res == NULL && (func = inst->in_class->cl_getattr) != NULL) {
        PyObject *args;
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return NULL;
        PyErr_Clear();
        args = PyTuple_Pack(2, inst, name);
        if (args == NULL)
            return NULL;
        res = PyEval_CallObject(func, args);
        Py_DECREF(args);
    }
    return res;
}

/* See classobject.h comments:  this only does dict lookups, and is always
 * safe to call.
 */
PyObject *
_PyInstance_Lookup(PyObject *pinst, PyObject *name)
{
    PyObject *v;
    PyClassObject *klass;
    PyInstanceObject *inst;     /* pinst cast to the right type */

    assert(PyInstance_Check(pinst));
    inst = (PyInstanceObject *)pinst;

    assert(PyString_Check(name));

    v = PyDict_GetItem(inst->in_dict, name);
    if (v == NULL)
        v = class_lookup(inst->in_class, name, &klass);
    return v;
}

static int
instance_setattr1(PyInstanceObject *inst, PyObject *name, PyObject *v)
{
    if (v == NULL) {
        int rv = PyDict_DelItem(inst->in_dict, name);
        if (rv < 0)
            PyErr_Format(PyExc_AttributeError,
                         "%.50s instance has no attribute '%.400s'",
                         PyString_AS_STRING(inst->in_class->cl_name),
                         PyString_AS_STRING(name));
        return rv;
    }
    else
        return PyDict_SetItem(inst->in_dict, name, v);
}

static int
instance_setattr(PyInstanceObject *inst, PyObject *name, PyObject *v)
{
    PyObject *func, *args, *res, *tmp;
    char *sname;

    if (!PyString_Check(name)) {
        PyErr_SetString(PyExc_TypeError, "attribute name must be a string");
        return -1;
    }

    sname = PyString_AsString(name);
    if (sname[0] == '_' && sname[1] == '_') {
        Py_ssize_t n = PyString_Size(name);
        if (sname[n-1] == '_' && sname[n-2] == '_') {
            if (strcmp(sname, "__dict__") == 0) {
                if (PyEval_GetRestricted()) {
                    PyErr_SetString(PyExc_RuntimeError,
                 "__dict__ not accessible in restricted mode");
                    return -1;
                }
                if (v == NULL || !PyDict_Check(v)) {
                    PyErr_SetString(PyExc_TypeError,
                       "__dict__ must be set to a dictionary");
                    return -1;
                }
                tmp = inst->in_dict;
                Py_INCREF(v);
                inst->in_dict = v;
                Py_DECREF(tmp);
                return 0;
            }
            if (strcmp(sname, "__class__") == 0) {
                if (PyEval_GetRestricted()) {
                    PyErr_SetString(PyExc_RuntimeError,
                "__class__ not accessible in restricted mode");
                    return -1;
                }
                if (v == NULL || !PyClass_Check(v)) {
                    PyErr_SetString(PyExc_TypeError,
                       "__class__ must be set to a class");
                    return -1;
                }
                tmp = (PyObject *)(inst->in_class);
                Py_INCREF(v);
                inst->in_class = (PyClassObject *)v;
                Py_DECREF(tmp);
                return 0;
            }
        }
    }
    if (v == NULL)
        func = inst->in_class->cl_delattr;
    else
        func = inst->in_class->cl_setattr;
    if (func == NULL)
        return instance_setattr1(inst, name, v);
    if (v == NULL)
        args = PyTuple_Pack(2, inst, name);
    else
        args = PyTuple_Pack(3, inst, name, v);
    if (args == NULL)
        return -1;
    res = PyEval_CallObject(func, args);
    Py_DECREF(args);
    if (res == NULL)
        return -1;
    Py_DECREF(res);
    return 0;
}

static PyObject *
instance_repr(PyInstanceObject *inst)
{
    PyObject *func;
    PyObject *res;
    static PyObject *reprstr;

    if (reprstr == NULL) {
        reprstr = PyString_InternFromString("__repr__");
        if (reprstr == NULL)
            return NULL;
    }
    func = instance_getattr(inst, reprstr);
    if (func == NULL) {
        PyObject *classname, *mod;
        char *cname;
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return NULL;
        PyErr_Clear();
        classname = inst->in_class->cl_name;
        mod = PyDict_GetItemString(inst->in_class->cl_dict,
                                   "__module__");
        if (classname != NULL && PyString_Check(classname))
            cname = PyString_AsString(classname);
        else
            cname = "?";
        if (mod == NULL || !PyString_Check(mod))
            return PyString_FromFormat("<?.%s instance at %p>",
                                       cname, inst);
        else
            return PyString_FromFormat("<%s.%s instance at %p>",
                                       PyString_AsString(mod),
                                       cname, inst);
    }
    res = PyEval_CallObject(func, (PyObject *)NULL);
    Py_DECREF(func);
    return res;
}

static PyObject *
instance_str(PyInstanceObject *inst)
{
    PyObject *func;
    PyObject *res;
    static PyObject *strstr;

    if (strstr == NULL) {
        strstr = PyString_InternFromString("__str__");
        if (strstr == NULL)
            return NULL;
    }
    func = instance_getattr(inst, strstr);
    if (func == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return NULL;
        PyErr_Clear();
        return instance_repr(inst);
    }
    res = PyEval_CallObject(func, (PyObject *)NULL);
    Py_DECREF(func);
    return res;
}

static long
instance_hash(PyInstanceObject *inst)
{
    PyObject *func;
    PyObject *res;
    long outcome;
    static PyObject *hashstr, *eqstr, *cmpstr;

    if (hashstr == NULL) {
        hashstr = PyString_InternFromString("__hash__");
        if (hashstr == NULL)
            return -1;
    }
    func = instance_getattr(inst, hashstr);
    if (func == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return -1;
        PyErr_Clear();
        /* If there is no __eq__ and no __cmp__ method, we hash on the
           address.  If an __eq__ or __cmp__ method exists, there must
           be a __hash__. */
        if (eqstr == NULL) {
            eqstr = PyString_InternFromString("__eq__");
            if (eqstr == NULL)
                return -1;
        }
        func = instance_getattr(inst, eqstr);
        if (func == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
                return -1;
            PyErr_Clear();
            if (cmpstr == NULL) {
                cmpstr = PyString_InternFromString("__cmp__");
                if (cmpstr == NULL)
                    return -1;
            }
            func = instance_getattr(inst, cmpstr);
            if (func == NULL) {
                if (!PyErr_ExceptionMatches(
                    PyExc_AttributeError))
                    return -1;
                PyErr_Clear();
                return _Py_HashPointer(inst);
            }
        }
        Py_XDECREF(func);
        PyErr_SetString(PyExc_TypeError, "unhashable instance");
        return -1;
    }
    res = PyEval_CallObject(func, (PyObject *)NULL);
    Py_DECREF(func);
    if (res == NULL)
        return -1;
    if (PyInt_Check(res) || PyLong_Check(res))
        /* This already converts a -1 result to -2. */
        outcome = res->ob_type->tp_hash(res);
    else {
        PyErr_SetString(PyExc_TypeError,
                        "__hash__() should return an int");
        outcome = -1;
    }
    Py_DECREF(res);
    return outcome;
}

static int
instance_traverse(PyInstanceObject *o, visitproc visit, void *arg)
{
    Py_VISIT(o->in_class);
    Py_VISIT(o->in_dict);
    return 0;
}

static PyObject *getitemstr, *setitemstr, *delitemstr, *lenstr;
static PyObject *iterstr, *nextstr;

static Py_ssize_t
instance_length(PyInstanceObject *inst)
{
    PyObject *func;
    PyObject *res;
    Py_ssize_t outcome;

    if (lenstr == NULL) {
        lenstr = PyString_InternFromString("__len__");
        if (lenstr == NULL)
            return -1;
    }
    func = instance_getattr(inst, lenstr);
    if (func == NULL)
        return -1;
    res = PyEval_CallObject(func, (PyObject *)NULL);
    Py_DECREF(func);
    if (res == NULL)
        return -1;
    if (PyInt_Check(res)) {
        outcome = PyInt_AsSsize_t(res);
        if (outcome == -1 && PyErr_Occurred()) {
            Py_DECREF(res);
            return -1;
        }
#if SIZEOF_SIZE_T < SIZEOF_INT
        /* Overflow check -- range of PyInt is more than C int */
        if (outcome != (int)outcome) {
            PyErr_SetString(PyExc_OverflowError,
             "__len__() should return 0 <= outcome < 2**31");
            outcome = -1;
        }
        else
#endif
        if (outcome < 0) {
            PyErr_SetString(PyExc_ValueError,
                            "__len__() should return >= 0");
            outcome = -1;
        }
    }
    else {
        PyErr_SetString(PyExc_TypeError,
                        "__len__() should return an int");
        outcome = -1;
    }
    Py_DECREF(res);
    return outcome;
}

static PyObject *
instance_subscript(PyInstanceObject *inst, PyObject *key)
{
    PyObject *func;
    PyObject *arg;
    PyObject *res;

    if (getitemstr == NULL) {
        getitemstr = PyString_InternFromString("__getitem__");
        if (getitemstr == NULL)
            return NULL;
    }
    func = instance_getattr(inst, getitemstr);
    if (func == NULL)
        return NULL;
    arg = PyTuple_Pack(1, key);
    if (arg == NULL) {
        Py_DECREF(func);
        return NULL;
    }
    res = PyEval_CallObject(func, arg);
    Py_DECREF(func);
    Py_DECREF(arg);
    return res;
}

static int
instance_ass_subscript(PyInstanceObject *inst, PyObject *key, PyObject *value)
{
    PyObject *func;
    PyObject *arg;
    PyObject *res;

    if (value == NULL) {
        if (delitemstr == NULL) {
            delitemstr = PyString_InternFromString("__delitem__");
            if (delitemstr == NULL)
                return -1;
        }
        func = instance_getattr(inst, delitemstr);
    }
    else {
        if (setitemstr == NULL) {
            setitemstr = PyString_InternFromString("__setitem__");
            if (setitemstr == NULL)
                return -1;
        }
        func = instance_getattr(inst, setitemstr);
    }
    if (func == NULL)
        return -1;
    if (value == NULL)
        arg = PyTuple_Pack(1, key);
    else
        arg = PyTuple_Pack(2, key, value);
    if (arg == NULL) {
        Py_DECREF(func);
        return -1;
    }
    res = PyEval_CallObject(func, arg);
    Py_DECREF(func);
    Py_DECREF(arg);
    if (res == NULL)
        return -1;
    Py_DECREF(res);
    return 0;
}

static PyMappingMethods instance_as_mapping = {
    (lenfunc)instance_length,                   /* mp_length */
    (binaryfunc)instance_subscript,             /* mp_subscript */
    (objobjargproc)instance_ass_subscript,      /* mp_ass_subscript */
};

static PyObject *
instance_item(PyInstanceObject *inst, Py_ssize_t i)
{
    PyObject *func, *res;

    if (getitemstr == NULL) {
        getitemstr = PyString_InternFromString("__getitem__");
        if (getitemstr == NULL)
            return NULL;
    }
    func = instance_getattr(inst, getitemstr);
    if (func == NULL)
        return NULL;
    res = PyObject_CallFunction(func, "n", i);
    Py_DECREF(func);
    return res;
}

static PyObject *
instance_slice(PyInstanceObject *inst, Py_ssize_t i, Py_ssize_t j)
{
    PyObject *func, *arg, *res;
    static PyObject *getslicestr;

    if (getslicestr == NULL) {
        getslicestr = PyString_InternFromString("__getslice__");
        if (getslicestr == NULL)
            return NULL;
    }
    func = instance_getattr(inst, getslicestr);

    if (func == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return NULL;
        PyErr_Clear();

        if (getitemstr == NULL) {
            getitemstr = PyString_InternFromString("__getitem__");
            if (getitemstr == NULL)
                return NULL;
        }
        func = instance_getattr(inst, getitemstr);
        if (func == NULL)
            return NULL;
        arg = Py_BuildValue("(N)", _PySlice_FromIndices(i, j));
    }
    else {
        if (PyErr_WarnPy3k("in 3.x, __getslice__ has been removed; "
                           "use __getitem__", 1) < 0) {
            Py_DECREF(func);
            return NULL;
        }
        arg = Py_BuildValue("(nn)", i, j);
    }

    if (arg == NULL) {
        Py_DECREF(func);
        return NULL;
    }
    res = PyEval_CallObject(func, arg);
    Py_DECREF(func);
    Py_DECREF(arg);
    return res;
}

static int
instance_ass_item(PyInstanceObject *inst, Py_ssize_t i, PyObject *item)
{
    PyObject *func, *arg, *res;

    if (item == NULL) {
        if (delitemstr == NULL) {
            delitemstr = PyString_InternFromString("__delitem__");
            if (delitemstr == NULL)
                return -1;
        }
        func = instance_getattr(inst, delitemstr);
    }
    else {
        if (setitemstr == NULL) {
            setitemstr = PyString_InternFromString("__setitem__");
            if (setitemstr == NULL)
                return -1;
        }
        func = instance_getattr(inst, setitemstr);
    }
    if (func == NULL)
        return -1;
    if (item == NULL)
        arg = Py_BuildValue("(n)", i);
    else
        arg = Py_BuildValue("(nO)", i, item);
    if (arg == NULL) {
        Py_DECREF(func);
        return -1;
    }
    res = PyEval_CallObject(func, arg);
    Py_DECREF(func);
    Py_DECREF(arg);
    if (res == NULL)
        return -1;
    Py_DECREF(res);
    return 0;
}

static int
instance_ass_slice(PyInstanceObject *inst, Py_ssize_t i, Py_ssize_t j, PyObject *value)
{
    PyObject *func, *arg, *res;
    static PyObject *setslicestr, *delslicestr;

    if (value == NULL) {
        if (delslicestr == NULL) {
            delslicestr =
                PyString_InternFromString("__delslice__");
            if (delslicestr == NULL)
                return -1;
        }
        func = instance_getattr(inst, delslicestr);
        if (func == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
                return -1;
            PyErr_Clear();
            if (delitemstr == NULL) {
                delitemstr =
                    PyString_InternFromString("__delitem__");
                if (delitemstr == NULL)
                    return -1;
            }
            func = instance_getattr(inst, delitemstr);
            if (func == NULL)
                return -1;

            arg = Py_BuildValue("(N)",
                                _PySlice_FromIndices(i, j));
        }
        else {
            if (PyErr_WarnPy3k("in 3.x, __delslice__ has been "
                                "removed; use __delitem__", 1) < 0) {
                Py_DECREF(func);
                return -1;
            }
            arg = Py_BuildValue("(nn)", i, j);
        }
    }
    else {
        if (setslicestr == NULL) {
            setslicestr =
                PyString_InternFromString("__setslice__");
            if (setslicestr == NULL)
                return -1;
        }
        func = instance_getattr(inst, setslicestr);
        if (func == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
                return -1;
            PyErr_Clear();
            if (setitemstr == NULL) {
                setitemstr =
                    PyString_InternFromString("__setitem__");
                if (setitemstr == NULL)
                    return -1;
            }
            func = instance_getattr(inst, setitemstr);
            if (func == NULL)
                return -1;

            arg = Py_BuildValue("(NO)",
                                _PySlice_FromIndices(i, j), value);
        }
        else {
            if (PyErr_WarnPy3k("in 3.x, __setslice__ has been "
                               "removed; use __setitem__", 1) < 0) {
                Py_DECREF(func);
                return -1;
            }
            arg = Py_BuildValue("(nnO)", i, j, value);
        }
    }
    if (arg == NULL) {
        Py_DECREF(func);
        return -1;
    }
    res = PyEval_CallObject(func, arg);
    Py_DECREF(func);
    Py_DECREF(arg);
    if (res == NULL)
        return -1;
    Py_DECREF(res);
    return 0;
}

static int
instance_contains(PyInstanceObject *inst, PyObject *member)
{
    static PyObject *__contains__;
    PyObject *func;

    /* Try __contains__ first.
     * If that can't be done, try iterator-based searching.
     */

    if(__contains__ == NULL) {
        __contains__ = PyString_InternFromString("__contains__");
        if(__contains__ == NULL)
            return -1;
    }
    func = instance_getattr(inst, __contains__);
    if (func) {
        PyObject *res;
        int ret;
        PyObject *arg = PyTuple_Pack(1, member);
        if(arg == NULL) {
            Py_DECREF(func);
            return -1;
        }
        res = PyEval_CallObject(func, arg);
        Py_DECREF(func);
        Py_DECREF(arg);
        if(res == NULL)
            return -1;
        ret = PyObject_IsTrue(res);
        Py_DECREF(res);
        return ret;
    }

    /* Couldn't find __contains__. */
    if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
        Py_ssize_t rc;
        /* Assume the failure was simply due to that there is no
         * __contains__ attribute, and try iterating instead.
         */
        PyErr_Clear();
        rc = _PySequence_IterSearch((PyObject *)inst, member,
                                    PY_ITERSEARCH_CONTAINS);
        if (rc >= 0)
            return rc > 0;
    }
    return -1;
}

static PySequenceMethods
instance_as_sequence = {
    (lenfunc)instance_length,                   /* sq_length */
    0,                                          /* sq_concat */
    0,                                          /* sq_repeat */
    (ssizeargfunc)instance_item,                /* sq_item */
    (ssizessizeargfunc)instance_slice,          /* sq_slice */
    (ssizeobjargproc)instance_ass_item,         /* sq_ass_item */
    (ssizessizeobjargproc)instance_ass_slice,/* sq_ass_slice */
    (objobjproc)instance_contains,              /* sq_contains */
};

static PyObject *
generic_unary_op(PyInstanceObject *self, PyObject *methodname)
{
    PyObject *func, *res;

    if ((func = instance_getattr(self, methodname)) == NULL)
        return NULL;
    res = PyEval_CallObject(func, (PyObject *)NULL);
    Py_DECREF(func);
    return res;
}

static PyObject *
generic_binary_op(PyObject *v, PyObject *w, char *opname)
{
    PyObject *result;
    PyObject *args;
    PyObject *func = PyObject_GetAttrString(v, opname);
    if (func == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return NULL;
        PyErr_Clear();
        Py_INCREF(Py_NotImplemented);
        return Py_NotImplemented;
    }
    args = PyTuple_Pack(1, w);
    if (args == NULL) {
        Py_DECREF(func);
        return NULL;
    }
    result = PyEval_CallObject(func, args);
    Py_DECREF(args);
    Py_DECREF(func);
    return result;
}


static PyObject *coerce_obj;

/* Try one half of a binary operator involving a class instance. */
static PyObject *
half_binop(PyObject *v, PyObject *w, char *opname, binaryfunc thisfunc,
                int swapped)
{
    PyObject *args;
    PyObject *coercefunc;
    PyObject *coerced = NULL;
    PyObject *v1;
    PyObject *result;

    if (!PyInstance_Check(v)) {
        Py_INCREF(Py_NotImplemented);
        return Py_NotImplemented;
    }

    if (coerce_obj == NULL) {
        coerce_obj = PyString_InternFromString("__coerce__");
        if (coerce_obj == NULL)
            return NULL;
    }
    coercefunc = PyObject_GetAttr(v, coerce_obj);
    if (coercefunc == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return NULL;
        PyErr_Clear();
        return generic_binary_op(v, w, opname);
    }

    args = PyTuple_Pack(1, w);
    if (args == NULL) {
        Py_DECREF(coercefunc);
        return NULL;
    }
    coerced = PyEval_CallObject(coercefunc, args);
    Py_DECREF(args);
    Py_DECREF(coercefunc);
    if (coerced == NULL) {
        return NULL;
    }
    if (coerced == Py_None || coerced == Py_NotImplemented) {
        Py_DECREF(coerced);
        return generic_binary_op(v, w, opname);
    }
    if (!PyTuple_Check(coerced) || PyTuple_Size(coerced) != 2) {
        Py_DECREF(coerced);
        PyErr_SetString(PyExc_TypeError,
                        "coercion should return None or 2-tuple");
        return NULL;
    }
    v1 = PyTuple_GetItem(coerced, 0);
    w = PyTuple_GetItem(coerced, 1);
    if (v1->ob_type == v->ob_type && PyInstance_Check(v)) {
        /* prevent recursion if __coerce__ returns self as the first
         * argument */
        result = generic_binary_op(v1, w, opname);
    } else {
        if (Py_EnterRecursiveCall(" after coercion"))
            return NULL;
        if (swapped)
            result = (thisfunc)(w, v1);
        else
            result = (thisfunc)(v1, w);
        Py_LeaveRecursiveCall();
    }
    Py_DECREF(coerced);
    return result;
}

/* Implement a binary operator involving at least one class instance. */
static PyObject *
do_binop(PyObject *v, PyObject *w, char *opname, char *ropname,
                   binaryfunc thisfunc)
{
    PyObject *result = half_binop(v, w, opname, thisfunc, 0);
    if (result == Py_NotImplemented) {
        Py_DECREF(result);
        result = half_binop(w, v, ropname, thisfunc, 1);
    }
    return result;
}

static PyObject *
do_binop_inplace(PyObject *v, PyObject *w, char *iopname, char *opname,
                        char *ropname, binaryfunc thisfunc)
{
    PyObject *result = half_binop(v, w, iopname, thisfunc, 0);
    if (result == Py_NotImplemented) {
        Py_DECREF(result);
        result = do_binop(v, w, opname, ropname, thisfunc);
    }
    return result;
}

static int
instance_coerce(PyObject **pv, PyObject **pw)
{
    PyObject *v = *pv;
    PyObject *w = *pw;
    PyObject *coercefunc;
    PyObject *args;
    PyObject *coerced;

    if (coerce_obj == NULL) {
        coerce_obj = PyString_InternFromString("__coerce__");
        if (coerce_obj == NULL)
            return -1;
    }
    coercefunc = PyObject_GetAttr(v, coerce_obj);
    if (coercefunc == NULL) {
        /* No __coerce__ method */
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return -1;
        PyErr_Clear();
        return 1;
    }
    /* Has __coerce__ method: call it */
    args = PyTuple_Pack(1, w);
    if (args == NULL) {
        return -1;
    }
    coerced = PyEval_CallObject(coercefunc, args);
    Py_DECREF(args);
    Py_DECREF(coercefunc);
    if (coerced == NULL) {
        /* __coerce__ call raised an exception */
        return -1;
    }
    if (coerced == Py_None || coerced == Py_NotImplemented) {
        /* __coerce__ says "I can't do it" */
        Py_DECREF(coerced);
        return 1;
    }
    if (!PyTuple_Check(coerced) || PyTuple_Size(coerced) != 2) {
        /* __coerce__ return value is malformed */
        Py_DECREF(coerced);
        PyErr_SetString(PyExc_TypeError,
                   "coercion should return None or 2-tuple");
        return -1;
    }
    /* __coerce__ returned two new values */
    *pv = PyTuple_GetItem(coerced, 0);
    *pw = PyTuple_GetItem(coerced, 1);
    Py_INCREF(*pv);
    Py_INCREF(*pw);
    Py_DECREF(coerced);
    return 0;
}

#define UNARY(funcname, methodname) \
static PyObject *funcname(PyInstanceObject *self) { \
    static PyObject *o; \
    if (o == NULL) { o = PyString_InternFromString(methodname); \
                     if (o == NULL) return NULL; } \
    return generic_unary_op(self, o); \
}

/* unary function with a fallback */
#define UNARY_FB(funcname, methodname, funcname_fb) \
static PyObject *funcname(PyInstanceObject *self) { \
    static PyObject *o; \
    if (o == NULL) { o = PyString_InternFromString(methodname); \
                     if (o == NULL) return NULL; } \
    if (PyObject_HasAttr((PyObject*)self, o)) \
        return generic_unary_op(self, o); \
    else \
        return funcname_fb(self); \
}

#define BINARY(f, m, n) \
static PyObject *f(PyObject *v, PyObject *w) { \
    return do_binop(v, w, "__" m "__", "__r" m "__", n); \
}

#define BINARY_INPLACE(f, m, n) \
static PyObject *f(PyObject *v, PyObject *w) { \
    return do_binop_inplace(v, w, "__i" m "__", "__" m "__", \
                    "__r" m "__", n); \
}

UNARY(instance_neg, "__neg__")
UNARY(instance_pos, "__pos__")
UNARY(instance_abs, "__abs__")

BINARY(instance_or, "or", PyNumber_Or)
BINARY(instance_and, "and", PyNumber_And)
BINARY(instance_xor, "xor", PyNumber_Xor)
BINARY(instance_lshift, "lshift", PyNumber_Lshift)
BINARY(instance_rshift, "rshift", PyNumber_Rshift)
BINARY(instance_add, "add", PyNumber_Add)
BINARY(instance_sub, "sub", PyNumber_Subtract)
BINARY(instance_mul, "mul", PyNumber_Multiply)
BINARY(instance_div, "div", PyNumber_Divide)
BINARY(instance_mod, "mod", PyNumber_Remainder)
BINARY(instance_divmod, "divmod", PyNumber_Divmod)
BINARY(instance_floordiv, "floordiv", PyNumber_FloorDivide)
BINARY(instance_truediv, "truediv", PyNumber_TrueDivide)

BINARY_INPLACE(instance_ior, "or", PyNumber_InPlaceOr)
BINARY_INPLACE(instance_ixor, "xor", PyNumber_InPlaceXor)
BINARY_INPLACE(instance_iand, "and", PyNumber_InPlaceAnd)
BINARY_INPLACE(instance_ilshift, "lshift", PyNumber_InPlaceLshift)
BINARY_INPLACE(instance_irshift, "rshift", PyNumber_InPlaceRshift)
BINARY_INPLACE(instance_iadd, "add", PyNumber_InPlaceAdd)
BINARY_INPLACE(instance_isub, "sub", PyNumber_InPlaceSubtract)
BINARY_INPLACE(instance_imul, "mul", PyNumber_InPlaceMultiply)
BINARY_INPLACE(instance_idiv, "div", PyNumber_InPlaceDivide)
BINARY_INPLACE(instance_imod, "mod", PyNumber_InPlaceRemainder)
BINARY_INPLACE(instance_ifloordiv, "floordiv", PyNumber_InPlaceFloorDivide)
BINARY_INPLACE(instance_itruediv, "truediv", PyNumber_InPlaceTrueDivide)

/* Try a 3-way comparison, returning an int; v is an instance.  Return:
   -2 for an exception;
   -1 if v < w;
   0 if v == w;
   1 if v > w;
   2 if this particular 3-way comparison is not implemented or undefined.
*/
static int
half_cmp(PyObject *v, PyObject *w)
{
    static PyObject *cmp_obj;
    PyObject *args;
    PyObject *cmp_func;
    PyObject *result;
    long l;

    assert(PyInstance_Check(v));

    if (cmp_obj == NULL) {
        cmp_obj = PyString_InternFromString("__cmp__");
        if (cmp_obj == NULL)
            return -2;
    }

    cmp_func = PyObject_GetAttr(v, cmp_obj);
    if (cmp_func == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return -2;
        PyErr_Clear();
        return 2;
    }

    args = PyTuple_Pack(1, w);
    if (args == NULL) {
        Py_DECREF(cmp_func);
        return -2;
    }

    result = PyEval_CallObject(cmp_func, args);
    Py_DECREF(args);
    Py_DECREF(cmp_func);

    if (result == NULL)
        return -2;

    if (result == Py_NotImplemented) {
        Py_DECREF(result);
        return 2;
    }

    l = PyInt_AsLong(result);
    Py_DECREF(result);
    if (l == -1 && PyErr_Occurred()) {
        PyErr_SetString(PyExc_TypeError,
                     "comparison did not return an int");
        return -2;
    }

    return l < 0 ? -1 : l > 0 ? 1 : 0;
}

/* Try a 3-way comparison, returning an int; either v or w is an instance.
   We first try a coercion.  Return:
   -2 for an exception;
   -1 if v < w;
   0 if v == w;
   1 if v > w;
   2 if this particular 3-way comparison is not implemented or undefined.
   THIS IS ONLY CALLED FROM object.c!
*/
static int
instance_compare(PyObject *v, PyObject *w)
{
    int c;

    c = PyNumber_CoerceEx(&v, &w);
    if (c < 0)
        return -2;
    if (c == 0) {
        /* If neither is now an instance, use regular comparison */
        if (!PyInstance_Check(v) && !PyInstance_Check(w)) {
            c = PyObject_Compare(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            if (PyErr_Occurred())
                return -2;
            return c < 0 ? -1 : c > 0 ? 1 : 0;
        }
    }
    else {
        /* The coercion didn't do anything.
           Treat this the same as returning v and w unchanged. */
        Py_INCREF(v);
        Py_INCREF(w);
    }

    if (PyInstance_Check(v)) {
        c = half_cmp(v, w);
        if (c <= 1) {
            Py_DECREF(v);
            Py_DECREF(w);
            return c;
        }
    }
    if (PyInstance_Check(w)) {
        c = half_cmp(w, v);
        if (c <= 1) {
            Py_DECREF(v);
            Py_DECREF(w);
            if (c >= -1)
                c = -c;
            return c;
        }
    }
    Py_DECREF(v);
    Py_DECREF(w);
    return 2;
}

static int
instance_nonzero(PyInstanceObject *self)
{
    PyObject *func, *res;
    long outcome;
    static PyObject *nonzerostr;

    if (nonzerostr == NULL) {
        nonzerostr = PyString_InternFromString("__nonzero__");
        if (nonzerostr == NULL)
            return -1;
    }
    if ((func = instance_getattr(self, nonzerostr)) == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return -1;
        PyErr_Clear();
        if (lenstr == NULL) {
            lenstr = PyString_InternFromString("__len__");
            if (lenstr == NULL)
                return -1;
        }
        if ((func = instance_getattr(self, lenstr)) == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
                return -1;
            PyErr_Clear();
            /* Fall back to the default behavior:
               all instances are nonzero */
            return 1;
        }
    }
    res = PyEval_CallObject(func, (PyObject *)NULL);
    Py_DECREF(func);
    if (res == NULL)
        return -1;
    if (!PyInt_Check(res)) {
        Py_DECREF(res);
        PyErr_SetString(PyExc_TypeError,
                        "__nonzero__ should return an int");
        return -1;
    }
    outcome = PyInt_AsLong(res);
    Py_DECREF(res);
    if (outcome < 0) {
        PyErr_SetString(PyExc_ValueError,
                        "__nonzero__ should return >= 0");
        return -1;
    }
    return outcome > 0;
}

static PyObject *
instance_index(PyInstanceObject *self)
{
    PyObject *func, *res;
    static PyObject *indexstr = NULL;

    if (indexstr == NULL) {
        indexstr = PyString_InternFromString("__index__");
        if (indexstr == NULL)
            return NULL;
    }
    if ((func = instance_getattr(self, indexstr)) == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return NULL;
        PyErr_Clear();
        PyErr_SetString(PyExc_TypeError,
                        "object cannot be interpreted as an index");
        return NULL;
    }
    res = PyEval_CallObject(func, (PyObject *)NULL);
    Py_DECREF(func);
    return res;
}


UNARY(instance_invert, "__invert__")
UNARY(_instance_trunc, "__trunc__")

static PyObject *
instance_int(PyInstanceObject *self)
{
    PyObject *truncated;
    static PyObject *int_name;
    if (int_name == NULL) {
        int_name = PyString_InternFromString("__int__");
        if (int_name == NULL)
            return NULL;
    }
    if (PyObject_HasAttr((PyObject*)self, int_name))
        return generic_unary_op(self, int_name);

    truncated = _instance_trunc(self);
    /* __trunc__ is specified to return an Integral type, but
       int() needs to return an int. */
    return _PyNumber_ConvertIntegralToInt(
        truncated,
        "__trunc__ returned non-Integral (type %.200s)");
}

UNARY_FB(instance_long, "__long__", instance_int)
UNARY(instance_float, "__float__")
UNARY(instance_oct, "__oct__")
UNARY(instance_hex, "__hex__")

static PyObject *
bin_power(PyObject *v, PyObject *w)
{
    return PyNumber_Power(v, w, Py_None);
}

/* This version is for ternary calls only (z != None) */
static PyObject *
instance_pow(PyObject *v, PyObject *w, PyObject *z)
{
    if (z == Py_None) {
        return do_binop(v, w, "__pow__", "__rpow__", bin_power);
    }
    else {
        PyObject *func;
        PyObject *args;
        PyObject *result;

        /* XXX Doesn't do coercions... */
        func = PyObject_GetAttrString(v, "__pow__");
        if (func == NULL)
            return NULL;
        args = PyTuple_Pack(2, w, z);
        if (args == NULL) {
            Py_DECREF(func);
            return NULL;
        }
        result = PyEval_CallObject(func, args);
        Py_DECREF(func);
        Py_DECREF(args);
        return result;
    }
}

static PyObject *
bin_inplace_power(PyObject *v, PyObject *w)
{
    return PyNumber_InPlacePower(v, w, Py_None);
}


static PyObject *
instance_ipow(PyObject *v, PyObject *w, PyObject *z)
{
    if (z == Py_None) {
        return do_binop_inplace(v, w, "__ipow__", "__pow__",
            "__rpow__", bin_inplace_power);
    }
    else {
        /* XXX Doesn't do coercions... */
        PyObject *func;
        PyObject *args;
        PyObject *result;

        func = PyObject_GetAttrString(v, "__ipow__");
        if (func == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
                return NULL;
            PyErr_Clear();
            return instance_pow(v, w, z);
        }
        args = PyTuple_Pack(2, w, z);
        if (args == NULL) {
            Py_DECREF(func);
            return NULL;
        }
        result = PyEval_CallObject(func, args);
        Py_DECREF(func);
        Py_DECREF(args);
        return result;
    }
}


/* Map rich comparison operators to their __xx__ namesakes */
#define NAME_OPS 6
static PyObject **name_op = NULL;

static int
init_name_op(void)
{
    int i;
    char *_name_op[] = {
        "__lt__",
        "__le__",
        "__eq__",
        "__ne__",
        "__gt__",
        "__ge__",
    };

    name_op = (PyObject **)malloc(sizeof(PyObject *) * NAME_OPS);
    if (name_op == NULL)
        return -1;
    for (i = 0; i < NAME_OPS; ++i) {
        name_op[i] = PyString_InternFromString(_name_op[i]);
        if (name_op[i] == NULL)
            return -1;
    }
    return 0;
}

static PyObject *
half_richcompare(PyObject *v, PyObject *w, int op)
{
    PyObject *method;
    PyObject *args;
    PyObject *res;

    assert(PyInstance_Check(v));

    if (name_op == NULL) {
        if (init_name_op() < 0)
            return NULL;
    }
    /* If the instance doesn't define an __getattr__ method, use
       instance_getattr2 directly because it will not set an
       exception on failure. */
    if (((PyInstanceObject *)v)->in_class->cl_getattr == NULL)
        method = instance_getattr2((PyInstanceObject *)v,
                                   name_op[op]);
    else
        method = PyObject_GetAttr(v, name_op[op]);
    if (method == NULL) {
        if (PyErr_Occurred()) {
            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
                return NULL;
            PyErr_Clear();
        }
        res = Py_NotImplemented;
        Py_INCREF(res);
        return res;
    }

    args = PyTuple_Pack(1, w);
    if (args == NULL) {
        Py_DECREF(method);
        return NULL;
    }

    res = PyEval_CallObject(method, args);
    Py_DECREF(args);
    Py_DECREF(method);

    return res;
}

static PyObject *
instance_richcompare(PyObject *v, PyObject *w, int op)
{
    PyObject *res;

    if (PyInstance_Check(v)) {
        res = half_richcompare(v, w, op);
        if (res != Py_NotImplemented)
            return res;
        Py_DECREF(res);
    }

    if (PyInstance_Check(w)) {
        res = half_richcompare(w, v, _Py_SwappedOp[op]);
        if (res != Py_NotImplemented)
            return res;
        Py_DECREF(res);
    }

    Py_INCREF(Py_NotImplemented);
    return Py_NotImplemented;
}


/* Get the iterator */
static PyObject *
instance_getiter(PyInstanceObject *self)
{
    PyObject *func;

    if (iterstr == NULL) {
        iterstr = PyString_InternFromString("__iter__");
        if (iterstr == NULL)
            return NULL;
    }
    if (getitemstr == NULL) {
        getitemstr = PyString_InternFromString("__getitem__");
        if (getitemstr == NULL)
            return NULL;
    }

    if ((func = instance_getattr(self, iterstr)) != NULL) {
        PyObject *res = PyEval_CallObject(func, (PyObject *)NULL);
        Py_DECREF(func);
        if (res != NULL && !PyIter_Check(res)) {
            PyErr_Format(PyExc_TypeError,
                         "__iter__ returned non-iterator "
                         "of type '%.100s'",
                         res->ob_type->tp_name);
            Py_DECREF(res);
            res = NULL;
        }
        return res;
    }
    if (!PyErr_ExceptionMatches(PyExc_AttributeError))
        return NULL;
    PyErr_Clear();
    if ((func = instance_getattr(self, getitemstr)) == NULL) {
        PyErr_SetString(PyExc_TypeError,
                        "iteration over non-sequence");
        return NULL;
    }
    Py_DECREF(func);
    return PySeqIter_New((PyObject *)self);
}


/* Call the iterator's next */
static PyObject *
instance_iternext(PyInstanceObject *self)
{
    PyObject *func;

    if (nextstr == NULL) {
        nextstr = PyString_InternFromString("next");
        if (nextstr == NULL)
            return NULL;
    }

    if ((func = instance_getattr(self, nextstr)) != NULL) {
        PyObject *res = PyEval_CallObject(func, (PyObject *)NULL);
        Py_DECREF(func);
        if (res != NULL) {
            return res;
        }
        if (PyErr_ExceptionMatches(PyExc_StopIteration)) {
            PyErr_Clear();
            return NULL;
        }
        return NULL;
    }
    PyErr_SetString(PyExc_TypeError, "instance has no next() method");
    return NULL;
}

static PyObject *
instance_call(PyObject *func, PyObject *arg, PyObject *kw)
{
    PyObject *res, *call = PyObject_GetAttrString(func, "__call__");
    if (call == NULL) {
        PyInstanceObject *inst = (PyInstanceObject*) func;
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return NULL;
        PyErr_Clear();
        PyErr_Format(PyExc_AttributeError,
                     "%.200s instance has no __call__ method",
                     PyString_AsString(inst->in_class->cl_name));
        return NULL;
    }
    /* We must check and increment the recursion depth here. Scenario:
           class A:
           pass
           A.__call__ = A() # that's right
           a = A() # ok
           a() # infinite recursion
       This bounces between instance_call() and PyObject_Call() without
       ever hitting eval_frame() (which has the main recursion check). */
    if (Py_EnterRecursiveCall(" in __call__")) {
        res = NULL;
    }
    else {
        res = PyObject_Call(call, arg, kw);
        Py_LeaveRecursiveCall();
    }
    Py_DECREF(call);
    return res;
}


static PyNumberMethods instance_as_number = {
    instance_add,                       /* nb_add */
    instance_sub,                       /* nb_subtract */
    instance_mul,                       /* nb_multiply */
    instance_div,                       /* nb_divide */
    instance_mod,                       /* nb_remainder */
    instance_divmod,                    /* nb_divmod */
    instance_pow,                       /* nb_power */
    (unaryfunc)instance_neg,            /* nb_negative */
    (unaryfunc)instance_pos,            /* nb_positive */
    (unaryfunc)instance_abs,            /* nb_absolute */
    (inquiry)instance_nonzero,          /* nb_nonzero */
    (unaryfunc)instance_invert,         /* nb_invert */
    instance_lshift,                    /* nb_lshift */
    instance_rshift,                    /* nb_rshift */
    instance_and,                       /* nb_and */
    instance_xor,                       /* nb_xor */
    instance_or,                        /* nb_or */
    instance_coerce,                    /* nb_coerce */
    (unaryfunc)instance_int,            /* nb_int */
    (unaryfunc)instance_long,           /* nb_long */
    (unaryfunc)instance_float,          /* nb_float */
    (unaryfunc)instance_oct,            /* nb_oct */
    (unaryfunc)instance_hex,            /* nb_hex */
    instance_iadd,                      /* nb_inplace_add */
    instance_isub,                      /* nb_inplace_subtract */
    instance_imul,                      /* nb_inplace_multiply */
    instance_idiv,                      /* nb_inplace_divide */
    instance_imod,                      /* nb_inplace_remainder */
    instance_ipow,                      /* nb_inplace_power */
    instance_ilshift,                   /* nb_inplace_lshift */
    instance_irshift,                   /* nb_inplace_rshift */
    instance_iand,                      /* nb_inplace_and */
    instance_ixor,                      /* nb_inplace_xor */
    instance_ior,                       /* nb_inplace_or */
    instance_floordiv,                  /* nb_floor_divide */
    instance_truediv,                   /* nb_true_divide */
    instance_ifloordiv,                 /* nb_inplace_floor_divide */
    instance_itruediv,                  /* nb_inplace_true_divide */
    (unaryfunc)instance_index,          /* nb_index */
};

PyTypeObject PyInstance_Type = {
    PyObject_HEAD_INIT(&PyType_Type)
    0,
    "instance",
    sizeof(PyInstanceObject),
    0,
    (destructor)instance_dealloc,               /* tp_dealloc */
    0,                                          /* tp_print */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    instance_compare,                           /* tp_compare */
    (reprfunc)instance_repr,                    /* tp_repr */
    &instance_as_number,                        /* tp_as_number */
    &instance_as_sequence,                      /* tp_as_sequence */
    &instance_as_mapping,                       /* tp_as_mapping */
    (hashfunc)instance_hash,                    /* tp_hash */
    instance_call,                              /* tp_call */
    (reprfunc)instance_str,                     /* tp_str */
    (getattrofunc)instance_getattr,             /* tp_getattro */
    (setattrofunc)instance_setattr,             /* tp_setattro */
    0,                                          /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_CHECKTYPES,/*tp_flags*/
    instance_doc,                               /* tp_doc */
    (traverseproc)instance_traverse,            /* tp_traverse */
    0,                                          /* tp_clear */
    instance_richcompare,                       /* tp_richcompare */
    offsetof(PyInstanceObject, in_weakreflist), /* tp_weaklistoffset */
    (getiterfunc)instance_getiter,              /* tp_iter */
    (iternextfunc)instance_iternext,            /* tp_iternext */
    0,                                          /* tp_methods */
    0,                                          /* tp_members */
    0,                                          /* tp_getset */
    0,                                          /* tp_base */
    0,                                          /* tp_dict */
    0,                                          /* tp_descr_get */
    0,                                          /* tp_descr_set */
    0,                                          /* tp_dictoffset */
    0,                                          /* tp_init */
    0,                                          /* tp_alloc */
    instance_new,                               /* tp_new */
};


/* Instance method objects are used for two purposes:
   (a) as bound instance methods (returned by instancename.methodname)
   (b) as unbound methods (returned by ClassName.methodname)
   In case (b), im_self is NULL
*/

PyObject *
PyMethod_New(PyObject *func, PyObject *self, PyObject *klass)
{
    register PyMethodObject *im;
    im = free_list;
    if (im != NULL) {
        free_list = (PyMethodObject *)(im->im_self);
        PyObject_INIT(im, &PyMethod_Type);
        numfree--;
    }
    else {
        im = PyObject_GC_New(PyMethodObject, &PyMethod_Type);
        if (im == NULL)
            return NULL;
    }
    im->im_weakreflist = NULL;
    Py_INCREF(func);
    im->im_func = func;
    Py_XINCREF(self);
    im->im_self = self;
    Py_XINCREF(klass);
    im->im_class = klass;
    _PyObject_GC_TRACK(im);
    return (PyObject *)im;
}

/* Descriptors for PyMethod attributes */

/* im_class, im_func and im_self are stored in the PyMethod object */

#define OFF(x) offsetof(PyMethodObject, x)

static PyMemberDef instancemethod_memberlist[] = {
    {"im_class",        T_OBJECT,       OFF(im_class),  READONLY|RESTRICTED,
     "the class associated with a method"},
    {"im_func",         T_OBJECT,       OFF(im_func),   READONLY|RESTRICTED,
     "the function (or other callable) implementing a method"},
    {"__func__",        T_OBJECT,       OFF(im_func),   READONLY|RESTRICTED,
     "the function (or other callable) implementing a method"},
    {"im_self",         T_OBJECT,       OFF(im_self),   READONLY|RESTRICTED,
     "the instance to which a method is bound; None for unbound methods"},
    {"__self__",        T_OBJECT,       OFF(im_self),   READONLY|RESTRICTED,
     "the instance to which a method is bound; None for unbound methods"},
    {NULL}      /* Sentinel */
};

/* Christian Tismer argued convincingly that method attributes should
   (nearly) always override function attributes.
   The one exception is __doc__; there's a default __doc__ which
   should only be used for the class, not for instances */

static PyObject *
instancemethod_get_doc(PyMethodObject *im, void *context)
{
    static PyObject *docstr;
    if (docstr == NULL) {
        docstr= PyString_InternFromString("__doc__");
        if (docstr == NULL)
            return NULL;
    }
    return PyObject_GetAttr(im->im_func, docstr);
}

static PyGetSetDef instancemethod_getset[] = {
    {"__doc__", (getter)instancemethod_get_doc, NULL, NULL},
    {0}
};

static PyObject *
instancemethod_getattro(PyObject *obj, PyObject *name)
{
    PyMethodObject *im = (PyMethodObject *)obj;
    PyTypeObject *tp = obj->ob_type;
    PyObject *descr = NULL;

    if (PyType_HasFeature(tp, Py_TPFLAGS_HAVE_CLASS)) {
        if (tp->tp_dict == NULL) {
            if (PyType_Ready(tp) < 0)
                return NULL;
        }
        descr = _PyType_Lookup(tp, name);
    }

    if (descr != NULL) {
        descrgetfunc f = TP_DESCR_GET(descr->ob_type);
        if (f != NULL)
            return f(descr, obj, (PyObject *)obj->ob_type);
        else {
            Py_INCREF(descr);
            return descr;
        }
    }

    return PyObject_GetAttr(im->im_func, name);
}

PyDoc_STRVAR(instancemethod_doc,
"instancemethod(function, instance, class)\n\
\n\
Create an instance method object.");

static PyObject *
instancemethod_new(PyTypeObject* type, PyObject* args, PyObject *kw)
{
    PyObject *func;
    PyObject *self;
    PyObject *classObj = NULL;

    if (!_PyArg_NoKeywords("instancemethod", kw))
        return NULL;
    if (!PyArg_UnpackTuple(args, "instancemethod", 2, 3,
                          &func, &self, &classObj))
        return NULL;
    if (!PyCallable_Check(func)) {
        PyErr_SetString(PyExc_TypeError,
                        "first argument must be callable");
        return NULL;
    }
    if (self == Py_None)
        self = NULL;
    if (self == NULL && classObj == NULL) {
        PyErr_SetString(PyExc_TypeError,
            "unbound methods must have non-NULL im_class");
        return NULL;
    }

    return PyMethod_New(func, self, classObj);
}

static void
instancemethod_dealloc(register PyMethodObject *im)
{
    _PyObject_GC_UNTRACK(im);
    if (im->im_weakreflist != NULL)
        PyObject_ClearWeakRefs((PyObject *)im);
    Py_DECREF(im->im_func);
    Py_XDECREF(im->im_self);
    Py_XDECREF(im->im_class);
    if (numfree < PyMethod_MAXFREELIST) {
        im->im_self = (PyObject *)free_list;
        free_list = im;
        numfree++;
    }
    else {
        PyObject_GC_Del(im);
    }
}

static int
instancemethod_compare(PyMethodObject *a, PyMethodObject *b)
{
    int cmp;
    cmp = PyObject_Compare(a->im_func, b->im_func);
    if (cmp)
        return cmp;

    if (a->im_self == b->im_self)
        return 0;
    if (a->im_self == NULL || b->im_self == NULL)
        return (a->im_self < b->im_self) ? -1 : 1;
    else
        return PyObject_Compare(a->im_self, b->im_self);
}

static PyObject *
instancemethod_repr(PyMethodObject *a)
{
    PyObject *self = a->im_self;
    PyObject *func = a->im_func;
    PyObject *klass = a->im_class;
    PyObject *funcname = NULL, *klassname = NULL, *result = NULL;
    char *sfuncname = "?", *sklassname = "?";

    funcname = PyObject_GetAttrString(func, "__name__");
    if (funcname == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return NULL;
        PyErr_Clear();
    }
    else if (!PyString_Check(funcname)) {
        Py_DECREF(funcname);
        funcname = NULL;
    }
    else
        sfuncname = PyString_AS_STRING(funcname);
    if (klass == NULL)
        klassname = NULL;
    else {
        klassname = PyObject_GetAttrString(klass, "__name__");
        if (klassname == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
                return NULL;
            PyErr_Clear();
        }
        else if (!PyString_Check(klassname)) {
            Py_DECREF(klassname);
            klassname = NULL;
        }
        else
            sklassname = PyString_AS_STRING(klassname);
    }
    if (self == NULL)
        result = PyString_FromFormat("<unbound method %s.%s>",
                                     sklassname, sfuncname);
    else {
        /* XXX Shouldn't use repr() here! */
        PyObject *selfrepr = PyObject_Repr(self);
        if (selfrepr == NULL)
            goto fail;
        if (!PyString_Check(selfrepr)) {
            Py_DECREF(selfrepr);
            goto fail;
        }
        result = PyString_FromFormat("<bound method %s.%s of %s>",
                                     sklassname, sfuncname,
                                     PyString_AS_STRING(selfrepr));
        Py_DECREF(selfrepr);
    }
  fail:
    Py_XDECREF(funcname);
    Py_XDECREF(klassname);
    return result;
}

static long
instancemethod_hash(PyMethodObject *a)
{
    long x, y;
    if (a->im_self == NULL)
        x = PyObject_Hash(Py_None);
    else
        x = PyObject_Hash(a->im_self);
    if (x == -1)
        return -1;
    y = PyObject_Hash(a->im_func);
    if (y == -1)
        return -1;
    x = x ^ y;
    if (x == -1)
        x = -2;
    return x;
}

static int
instancemethod_traverse(PyMethodObject *im, visitproc visit, void *arg)
{
    Py_VISIT(im->im_func);
    Py_VISIT(im->im_self);
    Py_VISIT(im->im_class);
    return 0;
}

static void
getclassname(PyObject *klass, char *buf, int bufsize)
{
    PyObject *name;

    assert(bufsize > 1);
    strcpy(buf, "?"); /* Default outcome */
    if (klass == NULL)
        return;
    name = PyObject_GetAttrString(klass, "__name__");
    if (name == NULL) {
        /* This function cannot return an exception */
        PyErr_Clear();
        return;
    }
    if (PyString_Check(name)) {
        strncpy(buf, PyString_AS_STRING(name), bufsize);
        buf[bufsize-1] = '\0';
    }
    Py_DECREF(name);
}

static void
getinstclassname(PyObject *inst, char *buf, int bufsize)
{
    PyObject *klass;

    if (inst == NULL) {
        assert(bufsize > 0 && (size_t)bufsize > strlen("nothing"));
        strcpy(buf, "nothing");
        return;
    }

    klass = PyObject_GetAttrString(inst, "__class__");
    if (klass == NULL) {
        /* This function cannot return an exception */
        PyErr_Clear();
        klass = (PyObject *)(inst->ob_type);
        Py_INCREF(klass);
    }
    getclassname(klass, buf, bufsize);
    Py_XDECREF(klass);
}

static PyObject *
instancemethod_call(PyObject *func, PyObject *arg, PyObject *kw)
{
    PyObject *self = PyMethod_GET_SELF(func);
    PyObject *klass = PyMethod_GET_CLASS(func);
    PyObject *result;

    func = PyMethod_GET_FUNCTION(func);
    if (self == NULL) {
        /* Unbound methods must be called with an instance of
           the class (or a derived class) as first argument */
        int ok;
        if (PyTuple_Size(arg) >= 1)
            self = PyTuple_GET_ITEM(arg, 0);
        if (self == NULL)
            ok = 0;
        else {
            ok = PyObject_IsInstance(self, klass);
            if (ok < 0)
                return NULL;
        }
        if (!ok) {
            char clsbuf[256];
            char instbuf[256];
            getclassname(klass, clsbuf, sizeof(clsbuf));
            getinstclassname(self, instbuf, sizeof(instbuf));
            PyErr_Format(PyExc_TypeError,
                         "unbound method %s%s must be called with "
                         "%s instance as first argument "
                         "(got %s%s instead)",
                         PyEval_GetFuncName(func),
                         PyEval_GetFuncDesc(func),
                         clsbuf,
                         instbuf,
                         self == NULL ? "" : " instance");
            return NULL;
        }
        Py_INCREF(arg);
    }
    else {
        Py_ssize_t argcount = PyTuple_Size(arg);
        PyObject *newarg = PyTuple_New(argcount + 1);
        int i;
        if (newarg == NULL)
            return NULL;
        Py_INCREF(self);
        PyTuple_SET_ITEM(newarg, 0, self);
        for (i = 0; i < argcount; i++) {
            PyObject *v = PyTuple_GET_ITEM(arg, i);
            Py_XINCREF(v);
            PyTuple_SET_ITEM(newarg, i+1, v);
        }
        arg = newarg;
    }
    result = PyObject_Call((PyObject *)func, arg, kw);
    Py_DECREF(arg);
    return result;
}

static PyObject *
instancemethod_descr_get(PyObject *meth, PyObject *obj, PyObject *cls)
{
    /* Don't rebind an already bound method, or an unbound method
       of a class that's not a base class of cls. */

    if (PyMethod_GET_SELF(meth) != NULL) {
        /* Already bound */
        Py_INCREF(meth);
        return meth;
    }
    /* No, it is an unbound method */
    if (PyMethod_GET_CLASS(meth) != NULL && cls != NULL) {
        /* Do subclass test.  If it fails, return meth unchanged. */
        int ok = PyObject_IsSubclass(cls, PyMethod_GET_CLASS(meth));
        if (ok < 0)
            return NULL;
        if (!ok) {
            Py_INCREF(meth);
            return meth;
        }
    }
    /* Bind it to obj */
    return PyMethod_New(PyMethod_GET_FUNCTION(meth), obj, cls);
}

PyTypeObject PyMethod_Type = {
    PyObject_HEAD_INIT(&PyType_Type)
    0,
    "instancemethod",
    sizeof(PyMethodObject),
    0,
    (destructor)instancemethod_dealloc,         /* tp_dealloc */
    0,                                          /* tp_print */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    (cmpfunc)instancemethod_compare,            /* tp_compare */
    (reprfunc)instancemethod_repr,              /* tp_repr */
    0,                                          /* tp_as_number */
    0,                                          /* tp_as_sequence */
    0,                                          /* tp_as_mapping */
    (hashfunc)instancemethod_hash,              /* tp_hash */
    instancemethod_call,                        /* tp_call */
    0,                                          /* tp_str */
    instancemethod_getattro,                    /* tp_getattro */
    PyObject_GenericSetAttr,                    /* tp_setattro */
    0,                                          /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC  | Py_TPFLAGS_HAVE_WEAKREFS, /* tp_flags */
    instancemethod_doc,                         /* tp_doc */
    (traverseproc)instancemethod_traverse,      /* tp_traverse */
    0,                                          /* tp_clear */
    0,                                          /* tp_richcompare */
    offsetof(PyMethodObject, im_weakreflist), /* tp_weaklistoffset */
    0,                                          /* tp_iter */
    0,                                          /* tp_iternext */
    0,                                          /* tp_methods */
    instancemethod_memberlist,                  /* tp_members */
    instancemethod_getset,                      /* tp_getset */
    0,                                          /* tp_base */
    0,                                          /* tp_dict */
    instancemethod_descr_get,                   /* tp_descr_get */
    0,                                          /* tp_descr_set */
    0,                                          /* tp_dictoffset */
    0,                                          /* tp_init */
    0,                                          /* tp_alloc */
    instancemethod_new,                         /* tp_new */
};

/* Clear out the free list */

int
PyMethod_ClearFreeList(void)
{
    int freelist_size = numfree;

    while (free_list) {
        PyMethodObject *im = free_list;
        free_list = (PyMethodObject *)(im->im_self);
        PyObject_GC_Del(im);
        numfree--;
    }
    assert(numfree == 0);
    return freelist_size;
}

void
PyMethod_Fini(void)
{
    (void)PyMethod_ClearFreeList();
}