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;