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

#include "Python.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;
int Py_Py3kWarningFlag;

/* 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);
}

/* for binary compatibility with 2.2 */
#undef _PyObject_Del
void
_PyObject_Del(PyObject *op)
{
	PyObject_FREE(op);
}

/* 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, "");
		Py_END_ALLOW_THREADS
	}
	else {
		if (op->ob_refcnt ob_refcnt, op);
			Py_END_ALLOW_THREADS
		else if (Py_TYPE(op)->tp_print == NULL) {
			PyObject *s;
			if (flags & Py_PRINT_RAW)
				s = PyObject_Str(op);
			else
				s = PyObject_Repr(op);
			if (s == NULL)
				ret = -1;
			else {
				ret = internal_print(s, fp, Py_PRINT_RAW,
						     nesting+1);
			}
			Py_XDECREF(s);
		}
		else
			ret = (*Py_TYPE(op)->tp_print)(op, fp, flags);
	}
	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.  See Misc/gdbinit for some useful gdb hooks */
void _PyObject_Dump(PyObject* op)
{
	if (op == NULL)
		fprintf(stderr, "NULL\n");
	else {
		PyGILState_STATE gil;
		fprintf(stderr, "object  : ");
		gil = PyGILState_Ensure();
		(void)PyObject_Print(op, stderr, 0);
		PyGILState_Release(gil);
		/* 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)
{
	if (PyErr_CheckSignals())
		return NULL;
#ifdef USE_STACKCHECK
	if (PyOS_CheckStack()) {
		PyErr_SetString(PyExc_MemoryError, "stack overflow");
		return NULL;
	}
#endif
	if (v == NULL)
		return PyString_FromString("");
	else if (Py_TYPE(v)->tp_repr == NULL)
		return PyString_FromFormat("",
					   Py_TYPE(v)->tp_name, v);
	else {
		PyObject *res;
		res = (*Py_TYPE(v)->tp_repr)(v);
		if (res == NULL)
			return NULL;
#ifdef Py_USING_UNICODE
		if (PyUnicode_Check(res)) {
			PyObject* str;
			str = PyUnicode_AsEncodedString(res, NULL, NULL);
			Py_DECREF(res);
			if (str)
				res = str;
			else
				return NULL;
		}
#endif
		if (!PyString_Check(res)) {
			PyErr_Format(PyExc_TypeError,
				     "__repr__ returned non-string (type %.200s)",
				     Py_TYPE(res)->tp_name);
			Py_DECREF(res);
			return NULL;
		}
		return res;
	}
}

PyObject *
_PyObject_Str(PyObject *v)
{
	PyObject *res;
	int type_ok;
	if (v == NULL)
		return PyString_FromString("");
	if (PyString_CheckExact(v)) {
		Py_INCREF(v);
		return v;
	}
#ifdef Py_USING_UNICODE
	if (PyUnicode_CheckExact(v)) {
		Py_INCREF(v);
		return v;
	}
#endif
	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;
	type_ok = PyString_Check(res);
#ifdef Py_USING_UNICODE
	type_ok = type_ok || PyUnicode_Check(res);
#endif
	if (!type_ok) {
		PyErr_Format(PyExc_TypeError,
			     "__str__ returned non-string (type %.200s)",
			     Py_TYPE(res)->tp_name);
		Py_DECREF(res);
		return NULL;
	}
	return res;
}

PyObject *
PyObject_Str(PyObject *v)
{
	PyObject *res = _PyObject_Str(v);
	if (res == NULL)
		return NULL;
#ifdef Py_USING_UNICODE
	if (PyUnicode_Check(res)) {
		PyObject* str;
		str = PyUnicode_AsEncodedString(res, NULL, NULL);
		Py_DECREF(res);
		if (str)
			res = str;
		else
		    	return NULL;
	}
#endif
	assert(PyString_Check(res));
	return res;
}

#ifdef Py_USING_UNICODE
PyObject *
PyObject_Unicode(PyObject *v)
{
	PyObject *res;
	PyObject *func;
	PyObject *str;
	int unicode_method_found = 0;
	static PyObject *unicodestr;

	if (v == NULL) {
		res = PyString_FromString("");
		if (res == NULL)
			return NULL;
		str = PyUnicode_FromEncodedObject(res, NULL, "strict");
		Py_DECREF(res);
		return str;
	} else if (PyUnicode_CheckExact(v)) {
		Py_INCREF(v);
		return v;
	}

	/* Try the __unicode__ method */
	if (unicodestr == NULL) {
		unicodestr= PyString_InternFromString("__unicode__");
		if (unicodestr == NULL)
			return NULL;
	}
	if (PyInstance_Check(v)) {
		/* We're an instance of a classic class */
		/* Try __unicode__ from the instance -- alas we have no type */
		func = PyObject_GetAttr(v, unicodestr);
		if (func != NULL) {
			unicode_method_found = 1;
			res = PyObject_CallFunctionObjArgs(func, NULL);
			Py_DECREF(func);
		}
		else {
			PyErr_Clear(); 
		}
	}
	else {
		/* Not a classic class instance, try __unicode__ from type */
		/* _PyType_Lookup doesn't create a reference */
		func = _PyType_Lookup(Py_TYPE(v), unicodestr);
		if (func != NULL) {
			unicode_method_found = 1;
			res = PyObject_CallFunctionObjArgs(func, v, NULL);
		}
		else {
			PyErr_Clear();
		}
	}

	/* Didn't find __unicode__ */
	if (!unicode_method_found) {
		if (PyUnicode_Check(v)) {
			/* For a Unicode subtype that's didn't overwrite __unicode__,
			   return a true Unicode object with the same data. */
			return PyUnicode_FromUnicode(PyUnicode_AS_UNICODE(v),
						     PyUnicode_GET_SIZE(v));
		}
		if (PyString_CheckExact(v)) {
			Py_INCREF(v);
			res = v;
		}
		else {
			if (Py_TYPE(v)->tp_str != NULL)
				res = (*Py_TYPE(v)->tp_str)(v);
			else
				res = PyObject_Repr(v);
		}
	}

	if (res == NULL)
		return NULL;
	if (!PyUnicode_Check(res)) {
		str = PyUnicode_FromEncodedObject(res, NULL, "strict");
		Py_DECREF(res);
		res = str;
	}
	return res;
}
#endif


/* Helper to warn about deprecated tp_compare return values.  Return:
   -2 for an exception;
   -1 if v <  w;
    0 if v == w;
    1 if v  > w.
   (This function cannot return 2.)
*/
static int
adjust_tp_compare(int c)
{
	if (PyErr_Occurred()) {
		if (c != -1 && c != -2) {
			PyObject *t, *v, *tb;
			PyErr_Fetch(&t, &v, &tb);
			if (PyErr_Warn(PyExc_RuntimeWarning,
				       "tp_compare didn't return -1 or -2 "
				       "for exception") < 0) {
				Py_XDECREF(t);
				Py_XDECREF(v);
				Py_XDECREF(tb);
			}
			else
				PyErr_Restore(t, v, tb);
		}
		return -2;
	}
	else if (c < -1 || c > 1) {
		if (PyErr_Warn(PyExc_RuntimeWarning,
			       "tp_compare didn't return -1, 0 or 1") < 0)
			return -2;
		else
			return c < -1 ? -1 : 1;
	}
	else {
		assert(c >= -1 && c tp_richcompare : NULL)

/* 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};

/* Try a genuine rich comparison, returning an object.  Return:
   NULL for exception;
   NotImplemented if this particular rich comparison is not implemented or
     undefined;
   some object not equal to NotImplemented if it is implemented
     (this latter object may not be a Boolean).
*/
static PyObject *
try_rich_compare(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 = RICHCOMPARE(w->ob_type)) != NULL) {
		res = (*f)(w, v, _Py_SwappedOp[op]);
		if (res != Py_NotImplemented)
			return res;
		Py_DECREF(res);
	}
	if ((f = RICHCOMPARE(v->ob_type)) != NULL) {
		res = (*f)(v, w, op);
		if (res != Py_NotImplemented)
			return res;
		Py_DECREF(res);
	}
	if ((f = RICHCOMPARE(w->ob_type)) != NULL) {
		return (*f)(w, v, _Py_SwappedOp[op]);
	}
	res = Py_NotImplemented;
	Py_INCREF(res);
	return res;
}

/* Try a genuine rich comparison, returning an int.  Return:
   -1 for exception (including the case where try_rich_compare() returns an
      object that's not a Boolean);
    0 if the outcome is false;
    1 if the outcome is true;
    2 if this particular rich comparison is not implemented or undefined.
*/
static int
try_rich_compare_bool(PyObject *v, PyObject *w, int op)
{
	PyObject *res;
	int ok;

	if (RICHCOMPARE(v->ob_type) == NULL && RICHCOMPARE(w->ob_type) == NULL)
		return 2; /* Shortcut, avoid INCREF+DECREF */
	res = try_rich_compare(v, w, op);
	if (res == NULL)
		return -1;
	if (res == Py_NotImplemented) {
		Py_DECREF(res);
		return 2;
	}
	ok = PyObject_IsTrue(res);
	Py_DECREF(res);
	return ok;
}

/* Try rich comparisons to determine a 3-way comparison.  Return:
   -2 for an exception;
   -1 if v  < w;
    0 if v == w;
    1 if v  > w;
    2 if this particular rich comparison is not implemented or undefined.
*/
static int
try_rich_to_3way_compare(PyObject *v, PyObject *w)
{
	static struct { int op; int outcome; } tries[3] = {
		/* Try this operator, and if it is true, use this outcome: */
		{Py_EQ, 0},
		{Py_LT, -1},
		{Py_GT, 1},
	};
	int i;

	if (RICHCOMPARE(v->ob_type) == NULL && RICHCOMPARE(w->ob_type) == NULL)
		return 2; /* Shortcut */

	for (i = 0; i < 3; i++) {
		switch (try_rich_compare_bool(v, w, tries[i].op)) {
		case -1:
			return -2;
		case 1:
			return tries[i].outcome;
		}
	}

	return 2;
}

/* Try a 3-way comparison, returning an int.  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
try_3way_compare(PyObject *v, PyObject *w)
{
	int c;
	cmpfunc f;

	/* Comparisons involving instances are given to instance_compare,
	   which has the same return conventions as this function. */

	f = v->ob_type->tp_compare;
	if (PyInstance_Check(v))
		return (*f)(v, w);
	if (PyInstance_Check(w))
		return (*w->ob_type->tp_compare)(v, w);

	/* If both have the same (non-NULL) tp_compare, use it. */
	if (f != NULL && f == w->ob_type->tp_compare) {
		c = (*f)(v, w);
		return adjust_tp_compare(c);
	}

	/* If either tp_compare is _PyObject_SlotCompare, that's safe. */
	if (f == _PyObject_SlotCompare ||
	    w->ob_type->tp_compare == _PyObject_SlotCompare)
		return _PyObject_SlotCompare(v, w);

	/* If we're here, v and w,
	    a) are not instances;
	    b) have different types or a type without tp_compare; and
	    c) don't have a user-defined tp_compare.
	   tp_compare implementations in C assume that both arguments
	   have their type, so we give up if the coercion fails or if
	   it yields types which are still incompatible (which can
	   happen with a user-defined nb_coerce).
	*/
	c = PyNumber_CoerceEx(&v, &w);
	if (c < 0)
		return -2;
	if (c > 0)
		return 2;
	f = v->ob_type->tp_compare;
	if (f != NULL && f == w->ob_type->tp_compare) {
		c = (*f)(v, w);
		Py_DECREF(v);
		Py_DECREF(w);
		return adjust_tp_compare(c);
	}

	/* No comparison defined */
	Py_DECREF(v);
	Py_DECREF(w);
	return 2;
}

/* Final fallback 3-way comparison, returning an int.  Return:
   -2 if an error occurred;
   -1 if v <  w;
    0 if v == w;
    1 if v >  w.
*/
static int
default_3way_compare(PyObject *v, PyObject *w)
{
	int c;
	const char *vname, *wname;

	if (v->ob_type == w->ob_type) {
		/* When comparing these pointers, they must be cast to
		 * integer types (i.e. Py_uintptr_t, our spelling of C9X's
		 * uintptr_t).  ANSI specifies that pointer compares other
		 * than == and != to non-related structures are undefined.
		 */
		Py_uintptr_t vv = (Py_uintptr_t)v;
		Py_uintptr_t ww = (Py_uintptr_t)w;
		return (vv < ww) ? -1 : (vv > ww) ? 1 : 0;
	}

	/* None is smaller than anything */
	if (v == Py_None)
		return -1;
	if (w == Py_None)
		return 1;

	/* different type: compare type names; numbers are smaller */
	if (PyNumber_Check(v))
		vname = "";
	else
		vname = v->ob_type->tp_name;
	if (PyNumber_Check(w))
		wname = "";
	else
		wname = w->ob_type->tp_name;
	c = strcmp(vname, wname);
	if (c < 0)
		return -1;
	if (c > 0)
		return 1;
	/* Same type name, or (more likely) incomparable numeric types */
	return ((Py_uintptr_t)(v->ob_type) < (
		Py_uintptr_t)(w->ob_type)) ? -1 : 1;
}

/* Do a 3-way comparison, by hook or by crook.  Return:
   -2 for an exception (but see below);
   -1 if v <  w;
    0 if v == w;
    1 if v >  w;
   BUT: if the object implements a tp_compare function, it returns
   whatever this function returns (whether with an exception or not).
*/
static int
do_cmp(PyObject *v, PyObject *w)
{
	int c;
	cmpfunc f;

	if (v->ob_type == w->ob_type
	    && (f = v->ob_type->tp_compare) != NULL) {
		c = (*f)(v, w);
		if (PyInstance_Check(v)) {
			/* Instance tp_compare has a different signature.
			   But if it returns undefined we fall through. */
			if (c != 2)
				return c;
			/* Else fall through to try_rich_to_3way_compare() */
		}
		else
			return adjust_tp_compare(c);
	}
	/* We only get here if one of the following is true:
	   a) v and w have different types
	   b) v and w have the same type, which doesn't have tp_compare
	   c) v and w are instances, and either __cmp__ is not defined or
	      __cmp__ returns NotImplemented
	*/
	c = try_rich_to_3way_compare(v, w);
	if (c < 2)
		return c;
	c = try_3way_compare(v, w);
	if (c < 2)
		return c;
	return default_3way_compare(v, w);
}

/* Compare v to w.  Return
   -1 if v <  w or exception (PyErr_Occurred() true in latter case).
    0 if v == w.
    1 if v > w.
   XXX The docs (C API manual) say the return value is undefined in case
   XXX of error.
*/
int
PyObject_Compare(PyObject *v, PyObject *w)
{
	int result;

	if (v == NULL || w == NULL) {
		PyErr_BadInternalCall();
		return -1;
	}
	if (v == w)
		return 0;
	if (Py_EnterRecursiveCall(" in cmp"))
		return -1;
	result = do_cmp(v, w);
	Py_LeaveRecursiveCall();
	return result < 0 ? -1 : result;
}

/* Return (new reference to) Py_True or Py_False. */
static PyObject *
convert_3way_to_object(int op, int c)
{
	PyObject *result;
	switch (op) {
	case Py_LT: c = c <  0; break;
	case Py_LE: c = c   0; break;
	case Py_GE: c = c >= 0; break;
	}
	result = c ? Py_True : Py_False;
	Py_INCREF(result);
	return result;
}

/* We want a rich comparison but don't have one.  Try a 3-way cmp instead.
   Return
   NULL      if error
   Py_True   if v op w
   Py_False  if not (v op w)
*/
static PyObject *
try_3way_to_rich_compare(PyObject *v, PyObject *w, int op)
{
	int c;

	c = try_3way_compare(v, w);
	if (c >= 2) {

		/* Py3K warning if types are not equal and comparison isn't == or !=  */
		if (Py_Py3kWarningFlag &&
		    v->ob_type != w->ob_type && op != Py_EQ && op != Py_NE &&
		    PyErr_WarnEx(PyExc_DeprecationWarning,
			       "comparing unequal types not supported "
			       "in 3.x", 1) < 0) {
			return NULL;
		}

		c = default_3way_compare(v, w);
	}
	if (c ob_type->tp_compare;
		if (fcmp != NULL) {
			int c = (*fcmp)(v, w);
			c = adjust_tp_compare(c);
			if (c == -2) {
				res = NULL;
				goto Done;
			}
			res = convert_3way_to_object(op, c);
			goto Done;
		}
	}

	/* Fast path not taken, or couldn't deliver a useful result. */
	res = do_richcmp(v, w, op);
Done:
	Py_LeaveRecursiveCall();
	return res;
}

/* Return -1 if error; 1 if v op w; 0 if not (v op w). */
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 = SIZEOF_VOID_P
	return (long)p;
#else
	/* convert to a Python long and hash that */
	PyObject* longobj;
	long x;

	if ((longobj = PyLong_FromVoidPtr(p)) == NULL) {
		x = -1;
		goto finally;
	}
	x = PyObject_Hash(longobj);

finally:
	Py_XDECREF(longobj);
	return x;
#endif
}

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

long
PyObject_Hash(PyObject *v)
{
	PyTypeObject *tp = v->ob_type;
	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);
	}
	if (tp->tp_compare == NULL && RICHCOMPARE(tp) == NULL) {
		return _Py_HashPointer(v); /* Use address as hash value */
	}
	/* If there's a cmp but no hash defined, 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 = PyString_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 = PyString_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 (!PyString_Check(name)) {
#ifdef Py_USING_UNICODE
		/* The Unicode to string conversion is done here because the
		   existing tp_getattro slots expect a string object as name
		   and we wouldn't want to break those. */
		if (PyUnicode_Check(name)) {
			name = _PyUnicode_AsDefaultEncodedString(name, NULL);
			if (name == NULL)
				return NULL;
		}
		else
#endif
		{
			PyErr_Format(PyExc_TypeError,
				     "attribute name must be string, not '%.200s'",
				     Py_TYPE(name)->tp_name);
			return NULL;
		}
	}
	if (tp->tp_getattro != NULL)
		return (*tp->tp_getattro)(v, name);
	if (tp->tp_getattr != NULL)
		return (*tp->tp_getattr)(v, PyString_AS_STRING(name));
	PyErr_Format(PyExc_AttributeError,
		     "'%.50s' object has no attribute '%.400s'",
		     tp->tp_name, PyString_AS_STRING(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 (!PyString_Check(name)){
#ifdef Py_USING_UNICODE
		/* The Unicode to string conversion is done here because the
		   existing tp_setattro slots expect a string object as name
		   and we wouldn't want to break those. */
		if (PyUnicode_Check(name)) {
			name = PyUnicode_AsEncodedString(name, NULL, NULL);
			if (name == NULL)
				return -1;
		}
		else
#endif
		{
			PyErr_Format(PyExc_TypeError,
				     "attribute name must be string, not '%.200s'",
				     Py_TYPE(name)->tp_name);
			return -1;
		}
	}
	else
		Py_INCREF(name);

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

	if (!(tp->tp_flags & Py_TPFLAGS_HAVE_CLASS))
		return NULL;
	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 (!PyString_Check(name)){
#ifdef Py_USING_UNICODE
		/* The Unicode to string conversion is done here because the
		   existing tp_setattro slots expect a string object as name
		   and we wouldn't want to break those. */
		if (PyUnicode_Check(name)) {
			name = PyUnicode_AsEncodedString(name, NULL, NULL);
			if (name == NULL)
				return NULL;
		}
		else
#endif
		{
			PyErr_Format(PyExc_TypeError,
				     "attribute name must be string, not '%.200s'",
				     Py_TYPE(name)->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);
			if (PyClass_Check(base))
				dict = ((PyClassObject *)base)->cl_dict;
			else {
				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 &&
	    PyType_HasFeature(descr->ob_type, Py_TPFLAGS_HAVE_CLASS)) {
		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 '%.400s'",
		     tp->tp_name, PyString_AS_STRING(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 (!PyString_Check(name)){
#ifdef Py_USING_UNICODE
		/* The Unicode to string conversion is done here because the
		   existing tp_setattro slots expect a string object as name
		   and we wouldn't want to break those. */
		if (PyUnicode_Check(name)) {
			name = PyUnicode_AsEncodedString(name, NULL, NULL);
			if (name == NULL)
				return -1;
		}
		else
#endif
		{
			PyErr_Format(PyExc_TypeError,
				     "attribute name must be string, not '%.200s'",
				     Py_TYPE(name)->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 &&
	    PyType_HasFeature(descr->ob_type, Py_TPFLAGS_HAVE_CLASS)) {
		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 '%.200s'",
			     tp->tp_name, PyString_AS_STRING(name));
		goto done;
	}

	PyErr_Format(PyExc_AttributeError,
		     "'%.50s' object attribute '%.400s' is read-only",
		     tp->tp_name, PyString_AS_STRING(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_nonzero != NULL)
		res = (*v->ob_type->tp_as_number->nb_nonzero)(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;
}

/* Coerce two numeric types to the "larger" one.
   Increment the reference count on each argument.
   Return value:
   -1 if an error occurred;
   0 if the coercion succeeded (and then the reference counts are increased);
   1 if no coercion is possible (and no error is raised).
*/
int
PyNumber_CoerceEx(PyObject **pv, PyObject **pw)
{
	register PyObject *v = *pv;
	register PyObject *w = *pw;
	int res;

	/* Shortcut only for old-style types */
	if (v->ob_type == w->ob_type &&
	    !PyType_HasFeature(v->ob_type, Py_TPFLAGS_CHECKTYPES))
	{
		Py_INCREF(v);
		Py_INCREF(w);
		return 0;
	}
	if (v->ob_type->tp_as_number && v->ob_type->tp_as_number->nb_coerce) {
		res = (*v->ob_type->tp_as_number->nb_coerce)(pv, pw);
		if (res ob_type->tp_as_number && w->ob_type->tp_as_number->nb_coerce) {
		res = (*w->ob_type->tp_as_number->nb_coerce)(pw, pv);
		if (res 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)
		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 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

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