Objects/object.c

/* Generic object operations; and implementation of None (NoObject) */

#include "Python.h"
#include "sliceobject.h" /* For PyEllipsis_Type */
#include "frameobject.h"

#ifdef __cplusplus
extern "C" {
#endif

#ifdef Py_REF_DEBUG
Py_ssize_t _Py_RefTotal;

Py_ssize_t
_Py_GetRefTotal(void)
{
    PyObject *o;
    Py_ssize_t total = _Py_RefTotal;
    /* ignore the references to the dummy object of the dicts and sets
       because they are not reliable and not useful (now that the
       hash table code is well-tested) */
    o = _PyDict_Dummy();
    if (o != NULL)
        total -= o->ob_refcnt;
    o = _PySet_Dummy();
    if (o != NULL)
        total -= o->ob_refcnt;
    return total;
}
#endif /* Py_REF_DEBUG */

int Py_DivisionWarningFlag;

/* Object allocation routines used by NEWOBJ and NEWVAROBJ macros.
   These are used by the individual routines for object creation.
   Do not call them otherwise, they do not initialize the object! */

#ifdef Py_TRACE_REFS
/* Head of circular doubly-linked list of all objects.  These are linked
 * together via the _ob_prev and _ob_next members of a PyObject, which
 * exist only in a Py_TRACE_REFS build.
 */
static PyObject refchain = {&refchain, &refchain};

/* Insert op at the front of the list of all objects.  If force is true,
 * op is added even if _ob_prev and _ob_next are non-NULL already.  If
 * force is false amd _ob_prev or _ob_next are non-NULL, do nothing.
 * force should be true if and only if op points to freshly allocated,
 * uninitialized memory, or you've unlinked op from the list and are
 * relinking it into the front.
 * Note that objects are normally added to the list via _Py_NewReference,
 * which is called by PyObject_Init.  Not all objects are initialized that
 * way, though; exceptions include statically allocated type objects, and
 * statically allocated singletons (like Py_True and Py_None).
 */
void
_Py_AddToAllObjects(PyObject *op, int force)
{
#ifdef  Py_DEBUG
    if (!force) {
        /* If it's initialized memory, op must be in or out of
         * the list unambiguously.
         */
        assert((op->_ob_prev == NULL) == (op->_ob_next == NULL));
    }
#endif
    if (force || op->_ob_prev == NULL) {
        op->_ob_next = refchain._ob_next;
        op->_ob_prev = &refchain;
        refchain._ob_next->_ob_prev = op;
        refchain._ob_next = op;
    }
}
#endif  /* Py_TRACE_REFS */

#ifdef COUNT_ALLOCS
static PyTypeObject *type_list;
/* All types are added to type_list, at least when
   they get one object created. That makes them
   immortal, which unfortunately contributes to
   garbage itself. If unlist_types_without_objects
   is set, they will be removed from the type_list
   once the last object is deallocated. */
static int unlist_types_without_objects;
extern Py_ssize_t tuple_zero_allocs, fast_tuple_allocs;
extern Py_ssize_t quick_int_allocs, quick_neg_int_allocs;
extern Py_ssize_t null_strings, one_strings;
void
dump_counts(FILE* f)
{
    PyTypeObject *tp;

    for (tp = type_list; tp; tp = tp->tp_next)
        fprintf(f, "%s alloc'd: %" PY_FORMAT_SIZE_T "d, "
            "freed: %" PY_FORMAT_SIZE_T "d, "
            "max in use: %" PY_FORMAT_SIZE_T "d\n",
            tp->tp_name, tp->tp_allocs, tp->tp_frees,
            tp->tp_maxalloc);
    fprintf(f, "fast tuple allocs: %" PY_FORMAT_SIZE_T "d, "
        "empty: %" PY_FORMAT_SIZE_T "d\n",
        fast_tuple_allocs, tuple_zero_allocs);
    fprintf(f, "fast int allocs: pos: %" PY_FORMAT_SIZE_T "d, "
        "neg: %" PY_FORMAT_SIZE_T "d\n",
        quick_int_allocs, quick_neg_int_allocs);
    fprintf(f, "null strings: %" PY_FORMAT_SIZE_T "d, "
        "1-strings: %" PY_FORMAT_SIZE_T "d\n",
        null_strings, one_strings);
}

PyObject *
get_counts(void)
{
    PyTypeObject *tp;
    PyObject *result;
    PyObject *v;

    result = PyList_New(0);
    if (result == NULL)
        return NULL;
    for (tp = type_list; tp; tp = tp->tp_next) {
        v = Py_BuildValue("(snnn)", tp->tp_name, tp->tp_allocs,
                          tp->tp_frees, tp->tp_maxalloc);
        if (v == NULL) {
            Py_DECREF(result);
            return NULL;
        }
        if (PyList_Append(result, v) < 0) {
            Py_DECREF(v);
            Py_DECREF(result);
            return NULL;
        }
        Py_DECREF(v);
    }
    return result;
}

void
inc_count(PyTypeObject *tp)
{
    if (tp->tp_next == NULL && tp->tp_prev == NULL) {
        /* first time; insert in linked list */
        if (tp->tp_next != NULL) /* sanity check */
            Py_FatalError("XXX inc_count sanity check");
        if (type_list)
            type_list->tp_prev = tp;
        tp->tp_next = type_list;
        /* Note that as of Python 2.2, heap-allocated type objects
         * can go away, but this code requires that they stay alive
         * until program exit.  That's why we're careful with
         * refcounts here.  type_list gets a new reference to tp,
         * while ownership of the reference type_list used to hold
         * (if any) was transferred to tp->tp_next in the line above.
         * tp is thus effectively immortal after this.
         */
        Py_INCREF(tp);
        type_list = tp;
#ifdef Py_TRACE_REFS
        /* Also insert in the doubly-linked list of all objects,
         * if not already there.
         */
        _Py_AddToAllObjects((PyObject *)tp, 0);
#endif
    }
    tp->tp_allocs++;
    if (tp->tp_allocs - tp->tp_frees > tp->tp_maxalloc)
        tp->tp_maxalloc = tp->tp_allocs - tp->tp_frees;
}

void dec_count(PyTypeObject *tp)
{
    tp->tp_frees++;
    if (unlist_types_without_objects &&
        tp->tp_allocs == tp->tp_frees) {
        /* unlink the type from type_list */
        if (tp->tp_prev)
            tp->tp_prev->tp_next = tp->tp_next;
        else
            type_list = tp->tp_next;
        if (tp->tp_next)
            tp->tp_next->tp_prev = tp->tp_prev;
        tp->tp_next = tp->tp_prev = NULL;
        Py_DECREF(tp);
    }
}

#endif

#ifdef Py_REF_DEBUG
/* Log a fatal error; doesn't return. */
void
_Py_NegativeRefcount(const char *fname, int lineno, PyObject *op)
{
    char buf[300];

    PyOS_snprintf(buf, sizeof(buf),
                  "%s:%i object at %p has negative ref count "
                  "%" PY_FORMAT_SIZE_T "d",
                  fname, lineno, op, op->ob_refcnt);
    Py_FatalError(buf);
}

#endif /* Py_REF_DEBUG */

void
Py_IncRef(PyObject *o)
{
    Py_XINCREF(o);
}

void
Py_DecRef(PyObject *o)
{
    Py_XDECREF(o);
}

PyObject *
PyObject_Init(PyObject *op, PyTypeObject *tp)
{
    if (op == NULL)
        return PyErr_NoMemory();
    /* Any changes should be reflected in PyObject_INIT (objimpl.h) */
    Py_TYPE(op) = tp;
    _Py_NewReference(op);
    return op;
}

PyVarObject *
PyObject_InitVar(PyVarObject *op, PyTypeObject *tp, Py_ssize_t size)
{
    if (op == NULL)
        return (PyVarObject *) PyErr_NoMemory();
    /* Any changes should be reflected in PyObject_INIT_VAR */
    op->ob_size = size;
    Py_TYPE(op) = tp;
    _Py_NewReference((PyObject *)op);
    return op;
}

PyObject *
_PyObject_New(PyTypeObject *tp)
{
    PyObject *op;
    op = (PyObject *) PyObject_MALLOC(_PyObject_SIZE(tp));
    if (op == NULL)
        return PyErr_NoMemory();
    return PyObject_INIT(op, tp);
}

PyVarObject *
_PyObject_NewVar(PyTypeObject *tp, Py_ssize_t nitems)
{
    PyVarObject *op;
    const size_t size = _PyObject_VAR_SIZE(tp, nitems);
    op = (PyVarObject *) PyObject_MALLOC(size);
    if (op == NULL)
        return (PyVarObject *)PyErr_NoMemory();
    return PyObject_INIT_VAR(op, tp, nitems);
}

/* Implementation of PyObject_Print with recursion checking */
static int
internal_print(PyObject *op, FILE *fp, int flags, int nesting)
{
    int ret = 0;
    if (nesting > 10) {
        PyErr_SetString(PyExc_RuntimeError, "print recursion");
        return -1;
    }
    if (PyErr_CheckSignals())
        return -1;
#ifdef USE_STACKCHECK
    if (PyOS_CheckStack()) {
        PyErr_SetString(PyExc_MemoryError, "stack overflow");
        return -1;
    }
#endif
    clearerr(fp); /* Clear any previous error condition */
    if (op == NULL) {
        Py_BEGIN_ALLOW_THREADS
        fprintf(fp, "<nil>");
        Py_END_ALLOW_THREADS
    }
    else {
        if (op->ob_refcnt <= 0)
            /* XXX(twouters) cast refcount to long until %zd is
               universally available */
            Py_BEGIN_ALLOW_THREADS
            fprintf(fp, "<refcnt %ld at %p>",
                (long)op->ob_refcnt, op);
            Py_END_ALLOW_THREADS
        else {
            PyObject *s;
            if (flags & Py_PRINT_RAW)
                s = PyObject_Str(op);
            else
                s = PyObject_Repr(op);
            if (s == NULL)
                ret = -1;
            else if (PyBytes_Check(s)) {
                fwrite(PyBytes_AS_STRING(s), 1,
                       PyBytes_GET_SIZE(s), fp);
            }
            else if (PyUnicode_Check(s)) {
                PyObject *t;
                t = PyUnicode_EncodeUTF8(PyUnicode_AS_UNICODE(s),
                                         PyUnicode_GET_SIZE(s),
                                         "backslashreplace");
                if (t == NULL)
                    ret = 0;
                else {
                    fwrite(PyBytes_AS_STRING(t), 1,
                           PyBytes_GET_SIZE(t), fp);
                    Py_DECREF(t);
                }
            }
            else {
                PyErr_Format(PyExc_TypeError,
                             "str() or repr() returned '%.100s'",
                             s->ob_type->tp_name);
                ret = -1;
            }
            Py_XDECREF(s);
        }
    }
    if (ret == 0) {
        if (ferror(fp)) {
            PyErr_SetFromErrno(PyExc_IOError);
            clearerr(fp);
            ret = -1;
        }
    }
    return ret;
}

int
PyObject_Print(PyObject *op, FILE *fp, int flags)
{
    return internal_print(op, fp, flags, 0);
}

/* For debugging convenience.  Set a breakpoint here and call it from your DLL */
void
_Py_BreakPoint(void)
{
}


/* For debugging convenience.  See Misc/gdbinit for some useful gdb hooks */
void
_PyObject_Dump(PyObject* op)
{
    if (op == NULL)
        fprintf(stderr, "NULL\n");
    else {
#ifdef WITH_THREAD
        PyGILState_STATE gil;
#endif
        fprintf(stderr, "object  : ");
#ifdef WITH_THREAD
        gil = PyGILState_Ensure();
#endif
        (void)PyObject_Print(op, stderr, 0);
#ifdef WITH_THREAD
        PyGILState_Release(gil);
#endif
        /* XXX(twouters) cast refcount to long until %zd is
           universally available */
        fprintf(stderr, "\n"
            "type    : %s\n"
            "refcount: %ld\n"
            "address : %p\n",
            Py_TYPE(op)==NULL ? "NULL" : Py_TYPE(op)->tp_name,
            (long)op->ob_refcnt,
            op);
    }
}

PyObject *
PyObject_Repr(PyObject *v)
{
    PyObject *res;
    if (PyErr_CheckSignals())
        return NULL;
#ifdef USE_STACKCHECK
    if (PyOS_CheckStack()) {
        PyErr_SetString(PyExc_MemoryError, "stack overflow");
        return NULL;
    }
#endif
    if (v == NULL)
        return PyUnicode_FromString("<NULL>");
    if (Py_TYPE(v)->tp_repr == NULL)
        return PyUnicode_FromFormat("<%s object at %p>",
                                    v->ob_type->tp_name, v);
    res = (*v->ob_type->tp_repr)(v);
    if (res != NULL && !PyUnicode_Check(res)) {
        PyErr_Format(PyExc_TypeError,
                     "__repr__ returned non-string (type %.200s)",
                     res->ob_type->tp_name);
        Py_DECREF(res);
        return NULL;
    }
    return res;
}

PyObject *
PyObject_Str(PyObject *v)
{
    PyObject *res;
    if (PyErr_CheckSignals())
        return NULL;
#ifdef USE_STACKCHECK
    if (PyOS_CheckStack()) {
        PyErr_SetString(PyExc_MemoryError, "stack overflow");
        return NULL;
    }
#endif
    if (v == NULL)
        return PyUnicode_FromString("<NULL>");
    if (PyUnicode_CheckExact(v)) {
        Py_INCREF(v);
        return v;
    }
    if (Py_TYPE(v)->tp_str == NULL)
        return PyObject_Repr(v);

    /* It is possible for a type to have a tp_str representation that loops
       infinitely. */
    if (Py_EnterRecursiveCall(" while getting the str of an object"))
        return NULL;
    res = (*Py_TYPE(v)->tp_str)(v);
    Py_LeaveRecursiveCall();
    if (res == NULL)
        return NULL;
    if (!PyUnicode_Check(res)) {
        PyErr_Format(PyExc_TypeError,
                     "__str__ returned non-string (type %.200s)",
                     Py_TYPE(res)->tp_name);
        Py_DECREF(res);
        return NULL;
    }
    return res;
}

PyObject *
PyObject_ASCII(PyObject *v)
{
    PyObject *repr, *ascii, *res;

    repr = PyObject_Repr(v);
    if (repr == NULL)
        return NULL;

    /* repr is guaranteed to be a PyUnicode object by PyObject_Repr */
    ascii = PyUnicode_EncodeASCII(
        PyUnicode_AS_UNICODE(repr),
        PyUnicode_GET_SIZE(repr),
        "backslashreplace");

    Py_DECREF(repr);
    if (ascii == NULL)
        return NULL;

    res = PyUnicode_DecodeASCII(
        PyBytes_AS_STRING(ascii),
        PyBytes_GET_SIZE(ascii),
        NULL);

    Py_DECREF(ascii);
    return res;
}

PyObject *
PyObject_Bytes(PyObject *v)
{
    PyObject *result, *func;
    static PyObject *bytesstring = NULL;

    if (v == NULL)
        return PyBytes_FromString("<NULL>");

    if (PyBytes_CheckExact(v)) {
        Py_INCREF(v);
        return v;
    }

    func = _PyObject_LookupSpecial(v, "__bytes__", &bytesstring);
    if (func != NULL) {
        result = PyObject_CallFunctionObjArgs(func, NULL);
        Py_DECREF(func);
        if (result == NULL)
        return NULL;
        if (!PyBytes_Check(result)) {
        PyErr_Format(PyExc_TypeError,
                     "__bytes__ returned non-bytes (type %.200s)",
                     Py_TYPE(result)->tp_name);
        Py_DECREF(result);
        return NULL;
        }
        return result;
    }
    else if (PyErr_Occurred())
        return NULL;
    return PyBytes_FromObject(v);
}

/* For Python 3.0.1 and later, the old three-way comparison has been
   completely removed in favour of rich comparisons.  PyObject_Compare() and
   PyObject_Cmp() are gone, and the builtin cmp function no longer exists.
   The old tp_compare slot has been renamed to tp_reserved, and should no
   longer be used.  Use tp_richcompare instead.

   See (*) below for practical amendments.

   tp_richcompare gets called with a first argument of the appropriate type
   and a second object of an arbitrary type.  We never do any kind of
   coercion.

   The tp_richcompare slot should return an object, as follows:

    NULL if an exception occurred
    NotImplemented if the requested comparison is not implemented
    any other false value if the requested comparison is false
    any other true value if the requested comparison is true

  The PyObject_RichCompare[Bool]() wrappers raise TypeError when they get
  NotImplemented.

  (*) Practical amendments:

  - If rich comparison returns NotImplemented, == and != are decided by
    comparing the object pointer (i.e. falling back to the base object
    implementation).

*/

/* Map rich comparison operators to their swapped version, e.g. LT <--> GT */
int _Py_SwappedOp[] = {Py_GT, Py_GE, Py_EQ, Py_NE, Py_LT, Py_LE};

static char *opstrings[] = {"<", "<=", "==", "!=", ">", ">="};

/* Perform a rich comparison, raising TypeError when the requested comparison
   operator is not supported. */
static PyObject *
do_richcompare(PyObject *v, PyObject *w, int op)
{
    richcmpfunc f;
    PyObject *res;

    if (v->ob_type != w->ob_type &&
        PyType_IsSubtype(w->ob_type, v->ob_type) &&
        (f = w->ob_type->tp_richcompare) != NULL) {
        res = (*f)(w, v, _Py_SwappedOp[op]);
        if (res != Py_NotImplemented)
            return res;
        Py_DECREF(res);
    }
    if ((f = v->ob_type->tp_richcompare) != NULL) {
        res = (*f)(v, w, op);
        if (res != Py_NotImplemented)
            return res;
        Py_DECREF(res);
    }
    if ((f = w->ob_type->tp_richcompare) != NULL) {
        res = (*f)(w, v, _Py_SwappedOp[op]);
        if (res != Py_NotImplemented)
            return res;
        Py_DECREF(res);
    }
    /* If neither object implements it, provide a sensible default
       for == and !=, but raise an exception for ordering. */
    switch (op) {
    case Py_EQ:
        res = (v == w) ? Py_True : Py_False;
        break;
    case Py_NE:
        res = (v != w) ? Py_True : Py_False;
        break;
    default:
        /* XXX Special-case None so it doesn't show as NoneType() */
        PyErr_Format(PyExc_TypeError,
                     "unorderable types: %.100s() %s %.100s()",
                     v->ob_type->tp_name,
                     opstrings[op],
                     w->ob_type->tp_name);
        return NULL;
    }
    Py_INCREF(res);
    return res;
}

/* Perform a rich comparison with object result.  This wraps do_richcompare()
   with a check for NULL arguments and a recursion check. */

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

    assert(Py_LT <= op && op <= Py_GE);
    if (v == NULL || w == NULL) {
        if (!PyErr_Occurred())
            PyErr_BadInternalCall();
        return NULL;
    }
    if (Py_EnterRecursiveCall(" in comparison"))
        return NULL;
    res = do_richcompare(v, w, op);
    Py_LeaveRecursiveCall();
    return res;
}

/* Perform a rich comparison with integer result.  This wraps
   PyObject_RichCompare(), returning -1 for error, 0 for false, 1 for true. */
int
PyObject_RichCompareBool(PyObject *v, PyObject *w, int op)
{
    PyObject *res;
    int ok;

    /* Quick result when objects are the same.
       Guarantees that identity implies equality. */
    if (v == w) {
        if (op == Py_EQ)
            return 1;
        else if (op == Py_NE)
            return 0;
    }

    res = PyObject_RichCompare(v, w, op);
    if (res == NULL)
        return -1;
    if (PyBool_Check(res))
        ok = (res == Py_True);
    else
        ok = PyObject_IsTrue(res);
    Py_DECREF(res);
    return ok;
}

/* Set of hash utility functions to help maintaining the invariant that
    if a==b then hash(a)==hash(b)

   All the utility functions (_Py_Hash*()) return "-1" to signify an error.
*/

long
_Py_HashDouble(double v)
{
    double intpart, fractpart;
    int expo;
    long hipart;
    long x;             /* the final hash value */
    /* This is designed so that Python numbers of different types
     * that compare equal hash to the same value; otherwise comparisons
     * of mapping keys will turn out weird.
     */

    fractpart = modf(v, &intpart);
    if (fractpart == 0.0) {
        /* This must return the same hash as an equal int or long. */
        if (intpart > LONG_MAX/2 || -intpart > LONG_MAX/2) {
            /* Convert to long and use its hash. */
            PyObject *plong;                    /* converted to Python long */
            if (Py_IS_INFINITY(intpart))
                /* can't convert to long int -- arbitrary */
                v = v < 0 ? -271828.0 : 314159.0;
            plong = PyLong_FromDouble(v);
            if (plong == NULL)
                return -1;
            x = PyObject_Hash(plong);
            Py_DECREF(plong);
            return x;
        }
        /* Fits in a C long == a Python int, so is its own hash. */
        x = (long)intpart;
        if (x == -1)
            x = -2;
        return x;
    }
    /* The fractional part is non-zero, so we don't have to worry about
     * making this match the hash of some other type.
     * Use frexp to get at the bits in the double.
     * Since the VAX D double format has 56 mantissa bits, which is the
     * most of any double format in use, each of these parts may have as
     * many as (but no more than) 56 significant bits.
     * So, assuming sizeof(long) >= 4, each part can be broken into two
     * longs; frexp and multiplication are used to do that.
     * Also, since the Cray double format has 15 exponent bits, which is
     * the most of any double format in use, shifting the exponent field
     * left by 15 won't overflow a long (again assuming sizeof(long) >= 4).
     */
    v = frexp(v, &expo);
    v *= 2147483648.0;          /* 2**31 */
    hipart = (long)v;           /* take the top 32 bits */
    v = (v - (double)hipart) * 2147483648.0; /* get the next 32 bits */
    x = hipart + (long)v + (expo << 15);
    if (x == -1)
        x = -2;
    return x;
}

long
_Py_HashPointer(void *p)
{
    long x;
    size_t y = (size_t)p;
    /* bottom 3 or 4 bits are likely to be 0; rotate y by 4 to avoid
       excessive hash collisions for dicts and sets */
    y = (y >> 4) | (y << (8 * SIZEOF_VOID_P - 4));
    x = (long)y;
    if (x == -1)
        x = -2;
    return x;
}

long
PyObject_HashNotImplemented(PyObject *v)
{
    PyErr_Format(PyExc_TypeError, "unhashable type: '%.200s'",
                 Py_TYPE(v)->tp_name);
    return -1;
}

long
PyObject_Hash(PyObject *v)
{
    PyTypeObject *tp = Py_TYPE(v);
    if (tp->tp_hash != NULL)
        return (*tp->tp_hash)(v);
    /* To keep to the general practice that inheriting
     * solely from object in C code should work without
     * an explicit call to PyType_Ready, we implicitly call
     * PyType_Ready here and then check the tp_hash slot again
     */
    if (tp->tp_dict == NULL) {
        if (PyType_Ready(tp) < 0)
            return -1;
        if (tp->tp_hash != NULL)
            return (*tp->tp_hash)(v);
    }
    /* Otherwise, the object can't be hashed */
    return PyObject_HashNotImplemented(v);
}

PyObject *
PyObject_GetAttrString(PyObject *v, const char *name)
{
    PyObject *w, *res;

    if (Py_TYPE(v)->tp_getattr != NULL)
        return (*Py_TYPE(v)->tp_getattr)(v, (char*)name);
    w = PyUnicode_InternFromString(name);
    if (w == NULL)
        return NULL;
    res = PyObject_GetAttr(v, w);
    Py_XDECREF(w);
    return res;
}

int
PyObject_HasAttrString(PyObject *v, const char *name)
{
    PyObject *res = PyObject_GetAttrString(v, name);
    if (res != NULL) {
        Py_DECREF(res);
        return 1;
    }
    PyErr_Clear();
    return 0;
}

int
PyObject_SetAttrString(PyObject *v, const char *name, PyObject *w)
{
    PyObject *s;
    int res;

    if (Py_TYPE(v)->tp_setattr != NULL)
        return (*Py_TYPE(v)->tp_setattr)(v, (char*)name, w);
    s = PyUnicode_InternFromString(name);
    if (s == NULL)
        return -1;
    res = PyObject_SetAttr(v, s, w);
    Py_XDECREF(s);
    return res;
}

PyObject *
PyObject_GetAttr(PyObject *v, PyObject *name)
{
    PyTypeObject *tp = Py_TYPE(v);

    if (!PyUnicode_Check(name)) {
        PyErr_Format(PyExc_TypeError,
                     "attribute name must be string, not '%.200s'",
                     name->ob_type->tp_name);
        return NULL;
    }
    if (tp->tp_getattro != NULL)
        return (*tp->tp_getattro)(v, name);
    if (tp->tp_getattr != NULL) {
        char *name_str = _PyUnicode_AsString(name);
        if (name_str == NULL)
            return NULL;
        return (*tp->tp_getattr)(v, name_str);
    }
    PyErr_Format(PyExc_AttributeError,
                 "'%.50s' object has no attribute '%U'",
                 tp->tp_name, name);
    return NULL;
}

int
PyObject_HasAttr(PyObject *v, PyObject *name)
{
    PyObject *res = PyObject_GetAttr(v, name);
    if (res != NULL) {
        Py_DECREF(res);
        return 1;
    }
    PyErr_Clear();
    return 0;
}

int
PyObject_SetAttr(PyObject *v, PyObject *name, PyObject *value)
{
    PyTypeObject *tp = Py_TYPE(v);
    int err;

    if (!PyUnicode_Check(name)) {
        PyErr_Format(PyExc_TypeError,
                     "attribute name must be string, not '%.200s'",
                     name->ob_type->tp_name);
        return -1;
    }
    Py_INCREF(name);

    PyUnicode_InternInPlace(&name);
    if (tp->tp_setattro != NULL) {
        err = (*tp->tp_setattro)(v, name, value);
        Py_DECREF(name);
        return err;
    }
    if (tp->tp_setattr != NULL) {
        char *name_str = _PyUnicode_AsString(name);
        if (name_str == NULL)
            return -1;
        err = (*tp->tp_setattr)(v, name_str, value);
        Py_DECREF(name);
        return err;
    }
    Py_DECREF(name);
    assert(name->ob_refcnt >= 1);
    if (tp->tp_getattr == NULL && tp->tp_getattro == NULL)
        PyErr_Format(PyExc_TypeError,
                     "'%.100s' object has no attributes "
                     "(%s .%U)",
                     tp->tp_name,
                     value==NULL ? "del" : "assign to",
                     name);
    else
        PyErr_Format(PyExc_TypeError,
                     "'%.100s' object has only read-only attributes "
                     "(%s .%U)",
                     tp->tp_name,
                     value==NULL ? "del" : "assign to",
                     name);
    return -1;
}

/* Helper to get a pointer to an object's __dict__ slot, if any */

PyObject **
_PyObject_GetDictPtr(PyObject *obj)
{
    Py_ssize_t dictoffset;
    PyTypeObject *tp = Py_TYPE(obj);

    dictoffset = tp->tp_dictoffset;
    if (dictoffset == 0)
        return NULL;
    if (dictoffset < 0) {
        Py_ssize_t tsize;
        size_t size;

        tsize = ((PyVarObject *)obj)->ob_size;
        if (tsize < 0)
            tsize = -tsize;
        size = _PyObject_VAR_SIZE(tp, tsize);

        dictoffset += (long)size;
        assert(dictoffset > 0);
        assert(dictoffset % SIZEOF_VOID_P == 0);
    }
    return (PyObject **) ((char *)obj + dictoffset);
}

PyObject *
PyObject_SelfIter(PyObject *obj)
{
    Py_INCREF(obj);
    return obj;
}

/* Helper used when the __next__ method is removed from a type:
   tp_iternext is never NULL and can be safely called without checking
   on every iteration.
 */

PyObject *
_PyObject_NextNotImplemented(PyObject *self)
{
    PyErr_Format(PyExc_TypeError,
                 "'%.200s' object is not iterable",
                 Py_TYPE(self)->tp_name);
    return NULL;
}

/* Generic GetAttr functions - put these in your tp_[gs]etattro slot */

PyObject *
PyObject_GenericGetAttr(PyObject *obj, PyObject *name)
{
    PyTypeObject *tp = Py_TYPE(obj);
    PyObject *descr = NULL;
    PyObject *res = NULL;
    descrgetfunc f;
    Py_ssize_t dictoffset;
    PyObject **dictptr;

    if (!PyUnicode_Check(name)){
        PyErr_Format(PyExc_TypeError,
                     "attribute name must be string, not '%.200s'",
                     name->ob_type->tp_name);
        return NULL;
    }
    else
        Py_INCREF(name);

    if (tp->tp_dict == NULL) {
        if (PyType_Ready(tp) < 0)
            goto done;
    }

#if 0 /* XXX this is not quite _PyType_Lookup anymore */
    /* Inline _PyType_Lookup */
    {
        Py_ssize_t i, n;
        PyObject *mro, *base, *dict;

        /* Look in tp_dict of types in MRO */
        mro = tp->tp_mro;
        assert(mro != NULL);
        assert(PyTuple_Check(mro));
        n = PyTuple_GET_SIZE(mro);
        for (i = 0; i < n; i++) {
            base = PyTuple_GET_ITEM(mro, i);
            assert(PyType_Check(base));
            dict = ((PyTypeObject *)base)->tp_dict;
            assert(dict && PyDict_Check(dict));
            descr = PyDict_GetItem(dict, name);
            if (descr != NULL)
                break;
        }
    }
#else
    descr = _PyType_Lookup(tp, name);
#endif

    Py_XINCREF(descr);

    f = NULL;
    if (descr != NULL) {
        f = descr->ob_type->tp_descr_get;
        if (f != NULL && PyDescr_IsData(descr)) {
            res = f(descr, obj, (PyObject *)obj->ob_type);
            Py_DECREF(descr);
            goto done;
        }
    }

    /* Inline _PyObject_GetDictPtr */
    dictoffset = tp->tp_dictoffset;
    if (dictoffset != 0) {
        PyObject *dict;
        if (dictoffset < 0) {
            Py_ssize_t tsize;
            size_t size;

            tsize = ((PyVarObject *)obj)->ob_size;
            if (tsize < 0)
                tsize = -tsize;
            size = _PyObject_VAR_SIZE(tp, tsize);

            dictoffset += (long)size;
            assert(dictoffset > 0);
            assert(dictoffset % SIZEOF_VOID_P == 0);
        }
        dictptr = (PyObject **) ((char *)obj + dictoffset);
        dict = *dictptr;
        if (dict != NULL) {
            Py_INCREF(dict);
            res = PyDict_GetItem(dict, name);
            if (res != NULL) {
                Py_INCREF(res);
                Py_XDECREF(descr);
                Py_DECREF(dict);
                goto done;
            }
            Py_DECREF(dict);
        }
    }

    if (f != NULL) {
        res = f(descr, obj, (PyObject *)Py_TYPE(obj));
        Py_DECREF(descr);
        goto done;
    }

    if (descr != NULL) {
        res = descr;
        /* descr was already increfed above */
        goto done;
    }

    PyErr_Format(PyExc_AttributeError,
                 "'%.50s' object has no attribute '%U'",
                 tp->tp_name, name);
  done:
    Py_DECREF(name);
    return res;
}

int
PyObject_GenericSetAttr(PyObject *obj, PyObject *name, PyObject *value)
{
    PyTypeObject *tp = Py_TYPE(obj);
    PyObject *descr;
    descrsetfunc f;
    PyObject **dictptr;
    int res = -1;

    if (!PyUnicode_Check(name)){
        PyErr_Format(PyExc_TypeError,
                     "attribute name must be string, not '%.200s'",
                     name->ob_type->tp_name);
        return -1;
    }
    else
        Py_INCREF(name);

    if (tp->tp_dict == NULL) {
        if (PyType_Ready(tp) < 0)
            goto done;
    }

    descr = _PyType_Lookup(tp, name);
    f = NULL;
    if (descr != NULL) {
        f = descr->ob_type->tp_descr_set;
        if (f != NULL && PyDescr_IsData(descr)) {
            res = f(descr, obj, value);
            goto done;
        }
    }

    dictptr = _PyObject_GetDictPtr(obj);
    if (dictptr != NULL) {
        PyObject *dict = *dictptr;
        if (dict == NULL && value != NULL) {
            dict = PyDict_New();
            if (dict == NULL)
                goto done;
            *dictptr = dict;
        }
        if (dict != NULL) {
            Py_INCREF(dict);
            if (value == NULL)
                res = PyDict_DelItem(dict, name);
            else
                res = PyDict_SetItem(dict, name, value);
            if (res < 0 && PyErr_ExceptionMatches(PyExc_KeyError))
                PyErr_SetObject(PyExc_AttributeError, name);
            Py_DECREF(dict);
            goto done;
        }
    }

    if (f != NULL) {
        res = f(descr, obj, value);
        goto done;
    }

    if (descr == NULL) {
        PyErr_Format(PyExc_AttributeError,
                     "'%.100s' object has no attribute '%U'",
                     tp->tp_name, name);
        goto done;
    }

    PyErr_Format(PyExc_AttributeError,
                 "'%.50s' object attribute '%U' is read-only",
                 tp->tp_name, name);
  done:
    Py_DECREF(name);
    return res;
}

/* Test a value used as condition, e.g., in a for or if statement.
   Return -1 if an error occurred */

int
PyObject_IsTrue(PyObject *v)
{
    Py_ssize_t res;
    if (v == Py_True)
        return 1;
    if (v == Py_False)
        return 0;
    if (v == Py_None)
        return 0;
    else if (v->ob_type->tp_as_number != NULL &&
             v->ob_type->tp_as_number->nb_bool != NULL)
        res = (*v->ob_type->tp_as_number->nb_bool)(v);
    else if (v->ob_type->tp_as_mapping != NULL &&
             v->ob_type->tp_as_mapping->mp_length != NULL)
        res = (*v->ob_type->tp_as_mapping->mp_length)(v);
    else if (v->ob_type->tp_as_sequence != NULL &&
             v->ob_type->tp_as_sequence->sq_length != NULL)
        res = (*v->ob_type->tp_as_sequence->sq_length)(v);
    else
        return 1;
    /* if it is negative, it should be either -1 or -2 */
    return (res > 0) ? 1 : Py_SAFE_DOWNCAST(res, Py_ssize_t, int);
}

/* equivalent of 'not v'
   Return -1 if an error occurred */

int
PyObject_Not(PyObject *v)
{
    int res;
    res = PyObject_IsTrue(v);
    if (res < 0)
        return res;
    return res == 0;
}

/* Test whether an object can be called */

int
PyCallable_Check(PyObject *x)
{
    if (x == NULL)
        return 0;
    return x->ob_type->tp_call != NULL;
}

/* ------------------------- PyObject_Dir() helpers ------------------------- */

/* Helper for PyObject_Dir.
   Merge the __dict__ of aclass into dict, and recursively also all
   the __dict__s of aclass's base classes.  The order of merging isn't
   defined, as it's expected that only the final set of dict keys is
   interesting.
   Return 0 on success, -1 on error.
*/

static int
merge_class_dict(PyObject* dict, PyObject* aclass)
{
    PyObject *classdict;
    PyObject *bases;

    assert(PyDict_Check(dict));
    assert(aclass);

    /* Merge in the type's dict (if any). */
    classdict = PyObject_GetAttrString(aclass, "__dict__");
    if (classdict == NULL)
        PyErr_Clear();
    else {
        int status = PyDict_Update(dict, classdict);
        Py_DECREF(classdict);
        if (status < 0)
            return -1;
    }

    /* Recursively merge in the base types' (if any) dicts. */
    bases = PyObject_GetAttrString(aclass, "__bases__");
    if (bases == NULL)
        PyErr_Clear();
    else {
        /* We have no guarantee that bases is a real tuple */
        Py_ssize_t i, n;
        n = PySequence_Size(bases); /* This better be right */
        if (n < 0)
            PyErr_Clear();
        else {
            for (i = 0; i < n; i++) {
                int status;
                PyObject *base = PySequence_GetItem(bases, i);
                if (base == NULL) {
                    Py_DECREF(bases);
                    return -1;
                }
                status = merge_class_dict(dict, base);
                Py_DECREF(base);
                if (status < 0) {
                    Py_DECREF(bases);
                    return -1;
                }
            }
        }
        Py_DECREF(bases);
    }
    return 0;
}

/* Helper for PyObject_Dir without arguments: returns the local scope. */
static PyObject *
_dir_locals(void)
{
    PyObject *names;
    PyObject *locals = PyEval_GetLocals();

    if (locals == NULL) {
        PyErr_SetString(PyExc_SystemError, "frame does not exist");
        return NULL;
    }

    names = PyMapping_Keys(locals);
    if (!names)
        return NULL;
    if (!PyList_Check(names)) {
        PyErr_Format(PyExc_TypeError,
            "dir(): expected keys() of locals to be a list, "
            "not '%.200s'", Py_TYPE(names)->tp_name);
        Py_DECREF(names);
        return NULL;
    }
    /* the locals don't need to be DECREF'd */
    return names;
}

/* Helper for PyObject_Dir of type objects: returns __dict__ and __bases__.
   We deliberately don't suck up its __class__, as methods belonging to the
   metaclass would probably be more confusing than helpful.
*/
static PyObject *
_specialized_dir_type(PyObject *obj)
{
    PyObject *result = NULL;
    PyObject *dict = PyDict_New();

    if (dict != NULL && merge_class_dict(dict, obj) == 0)
        result = PyDict_Keys(dict);

    Py_XDECREF(dict);
    return result;
}

/* Helper for PyObject_Dir of module objects: returns the module's __dict__. */
static PyObject *
_specialized_dir_module(PyObject *obj)
{
    PyObject *result = NULL;
    PyObject *dict = PyObject_GetAttrString(obj, "__dict__");

    if (dict != NULL) {
        if (PyDict_Check(dict))
            result = PyDict_Keys(dict);
        else {
            const char *name = PyModule_GetName(obj);
            if (name)
                PyErr_Format(PyExc_TypeError,
                             "%.200s.__dict__ is not a dictionary",
                             name);
        }
    }

    Py_XDECREF(dict);
    return result;
}

/* Helper for PyObject_Dir of generic objects: returns __dict__, __class__,
   and recursively up the __class__.__bases__ chain.
*/
static PyObject *
_generic_dir(PyObject *obj)
{
    PyObject *result = NULL;
    PyObject *dict = NULL;
    PyObject *itsclass = NULL;

    /* Get __dict__ (which may or may not be a real dict...) */
    dict = PyObject_GetAttrString(obj, "__dict__");
    if (dict == NULL) {
        PyErr_Clear();
        dict = PyDict_New();
    }
    else if (!PyDict_Check(dict)) {
        Py_DECREF(dict);
        dict = PyDict_New();
    }
    else {
        /* Copy __dict__ to avoid mutating it. */
        PyObject *temp = PyDict_Copy(dict);
        Py_DECREF(dict);
        dict = temp;
    }

    if (dict == NULL)
        goto error;

    /* Merge in attrs reachable from its class. */
    itsclass = PyObject_GetAttrString(obj, "__class__");
    if (itsclass == NULL)
        /* XXX(tomer): Perhaps fall back to obj->ob_type if no
                       __class__ exists? */
        PyErr_Clear();
    else {
        if (merge_class_dict(dict, itsclass) != 0)
            goto error;
    }

    result = PyDict_Keys(dict);
    /* fall through */
error:
    Py_XDECREF(itsclass);
    Py_XDECREF(dict);
    return result;
}

/* Helper for PyObject_Dir: object introspection.
   This calls one of the above specialized versions if no __dir__ method
   exists. */
static PyObject *
_dir_object(PyObject *obj)
{
    PyObject * result = NULL;
    PyObject * dirfunc = PyObject_GetAttrString((PyObject*)obj->ob_type,
                                                "__dir__");

    assert(obj);
    if (dirfunc == NULL) {
        /* use default implementation */
        PyErr_Clear();
        if (PyModule_Check(obj))
            result = _specialized_dir_module(obj);
        else if (PyType_Check(obj))
            result = _specialized_dir_type(obj);
        else
            result = _generic_dir(obj);
    }
    else {
        /* use __dir__ */
        result = PyObject_CallFunctionObjArgs(dirfunc, obj, NULL);
        Py_DECREF(dirfunc);
        if (result == NULL)
            return NULL;

        /* result must be a list */
        /* XXX(gbrandl): could also check if all items are strings */
        if (!PyList_Check(result)) {
            PyErr_Format(PyExc_TypeError,
                         "__dir__() must return a list, not %.200s",
                         Py_TYPE(result)->tp_name);
            Py_DECREF(result);
            result = NULL;
        }
    }

    return result;
}

/* Implementation of dir() -- if obj is NULL, returns the names in the current
   (local) scope.  Otherwise, performs introspection of the object: returns a
   sorted list of attribute names (supposedly) accessible from the object
*/
PyObject *
PyObject_Dir(PyObject *obj)
{
    PyObject * result;

    if (obj == NULL)
        /* no object -- introspect the locals */
        result = _dir_locals();
    else
        /* object -- introspect the object */
        result = _dir_object(obj);

    assert(result == NULL || PyList_Check(result));

    if (result != NULL && PyList_Sort(result) != 0) {
        /* sorting the list failed */
        Py_DECREF(result);
        result = NULL;
    }

    return result;
}

/*
NoObject is usable as a non-NULL undefined value, used by the macro None.
There is (and should be!) no way to create other objects of this type,
so there is exactly one (which is indestructible, by the way).
(XXX This type and the type of NotImplemented below should be unified.)
*/

/* ARGSUSED */
static PyObject *
none_repr(PyObject *op)
{
    return PyUnicode_FromString("None");
}

/* ARGUSED */
static void
none_dealloc(PyObject* ignore)
{
    /* This should never get called, but we also don't want to SEGV if
     * we accidentally decref None out of existence.
     */
    Py_FatalError("deallocating None");
}


static PyTypeObject PyNone_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "NoneType",
    0,
    0,
    none_dealloc,       /*tp_dealloc*/ /*never called*/
    0,                  /*tp_print*/
    0,                  /*tp_getattr*/
    0,                  /*tp_setattr*/
    0,                  /*tp_reserved*/
    none_repr,          /*tp_repr*/
    0,                  /*tp_as_number*/
    0,                  /*tp_as_sequence*/
    0,                  /*tp_as_mapping*/
    0,                  /*tp_hash */
};

PyObject _Py_NoneStruct = {
  _PyObject_EXTRA_INIT
  1, &PyNone_Type
};

/* NotImplemented is an object that can be used to signal that an
   operation is not implemented for the given type combination. */

static PyObject *
NotImplemented_repr(PyObject *op)
{
    return PyUnicode_FromString("NotImplemented");
}

static PyTypeObject PyNotImplemented_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "NotImplementedType",
    0,
    0,
    none_dealloc,       /*tp_dealloc*/ /*never called*/
    0,                  /*tp_print*/
    0,                  /*tp_getattr*/
    0,                  /*tp_setattr*/
    0,                  /*tp_reserved*/
    NotImplemented_repr, /*tp_repr*/
    0,                  /*tp_as_number*/
    0,                  /*tp_as_sequence*/
    0,                  /*tp_as_mapping*/
    0,                  /*tp_hash */
};

PyObject _Py_NotImplementedStruct = {
    _PyObject_EXTRA_INIT
    1, &PyNotImplemented_Type
};

void
_Py_ReadyTypes(void)
{
    if (PyType_Ready(&PyType_Type) < 0)
        Py_FatalError("Can't initialize type type");

    if (PyType_Ready(&_PyWeakref_RefType) < 0)
        Py_FatalError("Can't initialize weakref type");

    if (PyType_Ready(&_PyWeakref_CallableProxyType) < 0)
        Py_FatalError("Can't initialize callable weakref proxy type");

    if (PyType_Ready(&_PyWeakref_ProxyType) < 0)
        Py_FatalError("Can't initialize weakref proxy type");

    if (PyType_Ready(&PyBool_Type) < 0)
        Py_FatalError("Can't initialize bool type");

    if (PyType_Ready(&PyByteArray_Type) < 0)
        Py_FatalError("Can't initialize bytearray type");

    if (PyType_Ready(&PyBytes_Type) < 0)
        Py_FatalError("Can't initialize 'str'");

    if (PyType_Ready(&PyList_Type) < 0)
        Py_FatalError("Can't initialize list type");

    if (PyType_Ready(&PyNone_Type) < 0)
        Py_FatalError("Can't initialize None type");

    if (PyType_Ready(Py_Ellipsis->ob_type) < 0)
        Py_FatalError("Can't initialize type(Ellipsis)");

    if (PyType_Ready(&PyNotImplemented_Type) < 0)
        Py_FatalError("Can't initialize NotImplemented type");

    if (PyType_Ready(&PyTraceBack_Type) < 0)
        Py_FatalError("Can't initialize traceback type");

    if (PyType_Ready(&PySuper_Type) < 0)
        Py_FatalError("Can't initialize super type");

    if (PyType_Ready(&PyBaseObject_Type) < 0)
        Py_FatalError("Can't initialize object type");

    if (PyType_Ready(&PyRange_Type) < 0)
        Py_FatalError("Can't initialize range type");

    if (PyType_Ready(&PyDict_Type) < 0)
        Py_FatalError("Can't initialize dict type");

    if (PyType_Ready(&PySet_Type) < 0)
        Py_FatalError("Can't initialize set type");

    if (PyType_Ready(&PyUnicode_Type) < 0)
        Py_FatalError("Can't initialize str type");

    if (PyType_Ready(&PySlice_Type) < 0)
        Py_FatalError("Can't initialize slice type");

    if (PyType_Ready(&PyStaticMethod_Type) < 0)
        Py_FatalError("Can't initialize static method type");

#ifndef WITHOUT_COMPLEX
    if (PyType_Ready(&PyComplex_Type) < 0)
        Py_FatalError("Can't initialize complex type");
#endif
    if (PyType_Ready(&PyFloat_Type) < 0)
        Py_FatalError("Can't initialize float type");

    if (PyType_Ready(&PyLong_Type) < 0)
        Py_FatalError("Can't initialize int type");

    if (PyType_Ready(&PyFrozenSet_Type) < 0)
        Py_FatalError("Can't initialize frozenset type");

    if (PyType_Ready(&PyProperty_Type) < 0)
        Py_FatalError("Can't initialize property type");

    if (PyType_Ready(&PyMemoryView_Type) < 0)
        Py_FatalError("Can't initialize memoryview type");

    if (PyType_Ready(&PyTuple_Type) < 0)
        Py_FatalError("Can't initialize tuple type");

    if (PyType_Ready(&PyEnum_Type) < 0)
        Py_FatalError("Can't initialize enumerate type");

    if (PyType_Ready(&PyReversed_Type) < 0)
        Py_FatalError("Can't initialize reversed type");

    if (PyType_Ready(&PyStdPrinter_Type) < 0)
        Py_FatalError("Can't initialize StdPrinter");

    if (PyType_Ready(&PyCode_Type) < 0)
        Py_FatalError("Can't initialize code type");

    if (PyType_Ready(&PyFrame_Type) < 0)
        Py_FatalError("Can't initialize frame type");

    if (PyType_Ready(&PyCFunction_Type) < 0)
        Py_FatalError("Can't initialize builtin function type");

    if (PyType_Ready(&PyMethod_Type) < 0)
        Py_FatalError("Can't initialize method type");

    if (PyType_Ready(&PyFunction_Type) < 0)
        Py_FatalError("Can't initialize function type");

    if (PyType_Ready(&PyDictProxy_Type) < 0)
        Py_FatalError("Can't initialize dict proxy type");

    if (PyType_Ready(&PyGen_Type) < 0)
        Py_FatalError("Can't initialize generator type");

    if (PyType_Ready(&PyGetSetDescr_Type) < 0)
        Py_FatalError("Can't initialize get-set descriptor type");

    if (PyType_Ready(&PyWrapperDescr_Type) < 0)
        Py_FatalError("Can't initialize wrapper type");

    if (PyType_Ready(&PyEllipsis_Type) < 0)
        Py_FatalError("Can't initialize ellipsis type");

    if (PyType_Ready(&PyMemberDescr_Type) < 0)
        Py_FatalError("Can't initialize member descriptor type");

    if (PyType_Ready(&PyFilter_Type) < 0)
        Py_FatalError("Can't initialize filter type");

    if (PyType_Ready(&PyMap_Type) < 0)
        Py_FatalError("Can't initialize map type");

    if (PyType_Ready(&PyZip_Type) < 0)
        Py_FatalError("Can't initialize zip type");
}


#ifdef Py_TRACE_REFS

void
_Py_NewReference(PyObject *op)
{
    _Py_INC_REFTOTAL;
    op->ob_refcnt = 1;
    _Py_AddToAllObjects(op, 1);
    _Py_INC_TPALLOCS(op);
}

void
_Py_ForgetReference(register PyObject *op)
{
#ifdef SLOW_UNREF_CHECK
    register PyObject *p;
#endif
    if (op->ob_refcnt < 0)
        Py_FatalError("UNREF negative refcnt");
    if (op == &refchain ||
        op->_ob_prev->_ob_next != op || op->_ob_next->_ob_prev != op) {
        fprintf(stderr, "* ob\n");
        _PyObject_Dump(op);
        fprintf(stderr, "* op->_ob_prev->_ob_next\n");
        _PyObject_Dump(op->_ob_prev->_ob_next);
        fprintf(stderr, "* op->_ob_next->_ob_prev\n");
        _PyObject_Dump(op->_ob_next->_ob_prev);
        Py_FatalError("UNREF invalid object");
    }
#ifdef SLOW_UNREF_CHECK
    for (p = refchain._ob_next; p != &refchain; p = p->_ob_next) {
        if (p == op)
            break;
    }
    if (p == &refchain) /* Not found */
        Py_FatalError("UNREF unknown object");
#endif
    op->_ob_next->_ob_prev = op->_ob_prev;
    op->_ob_prev->_ob_next = op->_ob_next;
    op->_ob_next = op->_ob_prev = NULL;
    _Py_INC_TPFREES(op);
}

void
_Py_Dealloc(PyObject *op)
{
    destructor dealloc = Py_TYPE(op)->tp_dealloc;
    _Py_ForgetReference(op);
    (*dealloc)(op);
}

/* Print all live objects.  Because PyObject_Print is called, the
 * interpreter must be in a healthy state.
 */
void
_Py_PrintReferences(FILE *fp)
{
    PyObject *op;
    fprintf(fp, "Remaining objects:\n");
    for (op = refchain._ob_next; op != &refchain; op = op->_ob_next) {
        fprintf(fp, "%p [%" PY_FORMAT_SIZE_T "d] ", op, op->ob_refcnt);
        if (PyObject_Print(op, fp, 0) != 0)
            PyErr_Clear();
        putc('\n', fp);
    }
}

/* Print the addresses of all live objects.  Unlike _Py_PrintReferences, this
 * doesn't make any calls to the Python C API, so is always safe to call.
 */
void
_Py_PrintReferenceAddresses(FILE *fp)
{
    PyObject *op;
    fprintf(fp, "Remaining object addresses:\n");
    for (op = refchain._ob_next; op != &refchain; op = op->_ob_next)
        fprintf(fp, "%p [%" PY_FORMAT_SIZE_T "d] %s\n", op,
            op->ob_refcnt, Py_TYPE(op)->tp_name);
}

PyObject *
_Py_GetObjects(PyObject *self, PyObject *args)
{
    int i, n;
    PyObject *t = NULL;
    PyObject *res, *op;

    if (!PyArg_ParseTuple(args, "i|O", &n, &t))
        return NULL;
    op = refchain._ob_next;
    res = PyList_New(0);
    if (res == NULL)
        return NULL;
    for (i = 0; (n == 0 || i < n) && op != &refchain; i++) {
        while (op == self || op == args || op == res || op == t ||
               (t != NULL && Py_TYPE(op) != (PyTypeObject *) t)) {
            op = op->_ob_next;
            if (op == &refchain)
                return res;
        }
        if (PyList_Append(res, op) < 0) {
            Py_DECREF(res);
            return NULL;
        }
        op = op->_ob_next;
    }
    return res;
}

#endif

/* Hack to force loading of cobject.o */
PyTypeObject *_Py_cobject_hack = &PyCObject_Type;


/* Hack to force loading of pycapsule.o */
PyTypeObject *_PyCapsule_hack = &PyCapsule_Type;


/* Hack to force loading of abstract.o */
Py_ssize_t (*_Py_abstract_hack)(PyObject *) = PyObject_Size;


/* Python's malloc wrappers (see pymem.h) */

void *
PyMem_Malloc(size_t nbytes)
{
    return PyMem_MALLOC(nbytes);
}

void *
PyMem_Realloc(void *p, size_t nbytes)
{
    return PyMem_REALLOC(p, nbytes);
}

void
PyMem_Free(void *p)
{
    PyMem_FREE(p);
}


/* These methods are used to control infinite recursion in repr, str, print,
   etc.  Container objects that may recursively contain themselves,
   e.g. builtin dictionaries and lists, should used Py_ReprEnter() and
   Py_ReprLeave() to avoid infinite recursion.

   Py_ReprEnter() returns 0 the first time it is called for a particular
   object and 1 every time thereafter.  It returns -1 if an exception
   occurred.  Py_ReprLeave() has no return value.

   See dictobject.c and listobject.c for examples of use.
*/

#define KEY "Py_Repr"

int
Py_ReprEnter(PyObject *obj)
{
    PyObject *dict;
    PyObject *list;
    Py_ssize_t i;

    dict = PyThreadState_GetDict();
    if (dict == NULL)
        return 0;
    list = PyDict_GetItemString(dict, KEY);
    if (list == NULL) {
        list = PyList_New(0);
        if (list == NULL)
            return -1;
        if (PyDict_SetItemString(dict, KEY, list) < 0)
            return -1;
        Py_DECREF(list);
    }
    i = PyList_GET_SIZE(list);
    while (--i >= 0) {
        if (PyList_GET_ITEM(list, i) == obj)
            return 1;
    }
    PyList_Append(list, obj);
    return 0;
}

void
Py_ReprLeave(PyObject *obj)
{
    PyObject *dict;
    PyObject *list;
    Py_ssize_t i;

    dict = PyThreadState_GetDict();
    if (dict == NULL)
        return;
    list = PyDict_GetItemString(dict, KEY);
    if (list == NULL || !PyList_Check(list))
        return;
    i = PyList_GET_SIZE(list);
    /* Count backwards because we always expect obj to be list[-1] */
    while (--i >= 0) {
        if (PyList_GET_ITEM(list, i) == obj) {
            PyList_SetSlice(list, i, i + 1, NULL);
            break;
        }
    }
}

/* Trashcan support. */

/* Current call-stack depth of tp_dealloc calls. */
int _PyTrash_delete_nesting = 0;

/* List of objects that still need to be cleaned up, singly linked via their
 * gc headers' gc_prev pointers.
 */
PyObject *_PyTrash_delete_later = NULL;

/* Add op to the _PyTrash_delete_later list.  Called when the current
 * call-stack depth gets large.  op must be a currently untracked gc'ed
 * object, with refcount 0.  Py_DECREF must already have been called on it.
 */
void
_PyTrash_deposit_object(PyObject *op)
{
    assert(PyObject_IS_GC(op));
    assert(_Py_AS_GC(op)->gc.gc_refs == _PyGC_REFS_UNTRACKED);
    assert(op->ob_refcnt == 0);
    _Py_AS_GC(op)->gc.gc_prev = (PyGC_Head *)_PyTrash_delete_later;
    _PyTrash_delete_later = op;
}

/* Dealloccate all the objects in the _PyTrash_delete_later list.  Called when
 * the call-stack unwinds again.
 */
void
_PyTrash_destroy_chain(void)
{
    while (_PyTrash_delete_later) {
        PyObject *op = _PyTrash_delete_later;
        destructor dealloc = Py_TYPE(op)->tp_dealloc;

        _PyTrash_delete_later =
            (PyObject*) _Py_AS_GC(op)->gc.gc_prev;

        /* Call the deallocator directly.  This used to try to
         * fool Py_DECREF into calling it indirectly, but
         * Py_DECREF was already called on this object, and in
         * assorted non-release builds calling Py_DECREF again ends
         * up distorting allocation statistics.
         */
        assert(op->ob_refcnt == 0);
        ++_PyTrash_delete_nesting;
        (*dealloc)(op);
        --_PyTrash_delete_nesting;
    }
}

#ifdef __cplusplus
}
#endif