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Deleting cyclic object comparison. 

SF patch 825639
http://mail.python.org/pipermail/python-dev/2003-October/039445.html
This commit is contained in:
Armin Rigo 2003-10-28 12:05:48 +00:00
parent 0e4f76405d
commit 2b3eb4062c
9 changed files with 109 additions and 275 deletions
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14
Include/ceval.h
View File

@ -43,9 +43,23 @@ PyAPI_FUNC(int) Py_FlushLine(void);
PyAPI_FUNC(int) Py_AddPendingCall(int (*func)(void *), void *arg);
PyAPI_FUNC(int) Py_MakePendingCalls(void);
/* Protection against deeply nested recursive calls */
PyAPI_FUNC(void) Py_SetRecursionLimit(int);
PyAPI_FUNC(int) Py_GetRecursionLimit(void);
#define Py_EnterRecursiveCall(where) \
(_Py_MakeRecCheck(PyThreadState_GET()->recursion_depth) && \
_Py_CheckRecursiveCall(where))
#define Py_LeaveRecursiveCall() \
(--PyThreadState_GET()->recursion_depth)
PyAPI_FUNC(int) _Py_CheckRecursiveCall(char *where);
PyAPI_DATA(int) _Py_CheckRecursionLimit;
#ifdef USE_STACKCHECK
# define _Py_MakeRecCheck(x) (++(x) > --_Py_CheckRecursionLimit)
#else
# define _Py_MakeRecCheck(x) (++(x) > _Py_CheckRecursionLimit)
#endif
PyAPI_FUNC(char *) PyEval_GetFuncName(PyObject *);
PyAPI_FUNC(char *) PyEval_GetFuncDesc(PyObject *);

25
Lib/test/pickletester.py
View File

@ -424,9 +424,8 @@ class AbstractPickleTests(unittest.TestCase):
for proto in protocols:
s = self.dumps(l, proto)
x = self.loads(s)
self.assertEqual(x, l)
self.assertEqual(x, x[0])
self.assertEqual(id(x), id(x[0]))
self.assertEqual(len(x), 1)
self.assert_(x is x[0])
def test_recursive_dict(self):
d = {}
@ -434,9 +433,8 @@ class AbstractPickleTests(unittest.TestCase):
for proto in protocols:
s = self.dumps(d, proto)
x = self.loads(s)
self.assertEqual(x, d)
self.assertEqual(x[1], x)
self.assertEqual(id(x[1]), id(x))
self.assertEqual(x.keys(), [1])
self.assert_(x[1] is x)
def test_recursive_inst(self):
i = C()
@ -444,9 +442,8 @@ class AbstractPickleTests(unittest.TestCase):
for proto in protocols:
s = self.dumps(i, 2)
x = self.loads(s)
self.assertEqual(x, i)
self.assertEqual(x.attr, x)
self.assertEqual(id(x.attr), id(x))
self.assertEqual(dir(x), dir(i))
self.assert_(x.attr is x)
def test_recursive_multi(self):
l = []
@ -457,12 +454,10 @@ class AbstractPickleTests(unittest.TestCase):
for proto in protocols:
s = self.dumps(l, proto)
x = self.loads(s)
self.assertEqual(x, l)
self.assertEqual(x[0], i)
self.assertEqual(x[0].attr, d)
self.assertEqual(x[0].attr[1], x)
self.assertEqual(x[0].attr[1][0], i)
self.assertEqual(x[0].attr[1][0].attr, d)
self.assertEqual(len(x), 1)
self.assertEqual(dir(x[0]), dir(i))
self.assertEqual(x[0].attr.keys(), [1])
self.assert_(x[0].attr[1] is x)
def test_garyp(self):
self.assertRaises(self.error, self.loads, 'garyp')

12
Lib/test/test_builtin.py
View File

@ -167,16 +167,16 @@ class BuiltinTest(unittest.TestCase):
self.assertEqual(cmp(-1, 1), -1)
self.assertEqual(cmp(1, -1), 1)
self.assertEqual(cmp(1, 1), 0)
# verify that circular objects are handled
# verify that circular objects are not handled
a = []; a.append(a)
b = []; b.append(b)
from UserList import UserList
c = UserList(); c.append(c)
self.assertEqual(cmp(a, b), 0)
self.assertEqual(cmp(b, c), 0)
self.assertEqual(cmp(c, a), 0)
self.assertEqual(cmp(a, c), 0)
# okay, now break the cycles
self.assertRaises(RuntimeError, cmp, a, b)
self.assertRaises(RuntimeError, cmp, b, c)
self.assertRaises(RuntimeError, cmp, c, a)
self.assertRaises(RuntimeError, cmp, a, c)
# okay, now break the cycles
a.pop(); b.pop(); c.pop()
self.assertRaises(TypeError, cmp)

12
Lib/test/test_copy.py
View File

@ -272,10 +272,10 @@ class TestCopy(unittest.TestCase):
x = []
x.append(x)
y = copy.deepcopy(x)
self.assertEqual(y, x)
self.assertRaises(RuntimeError, cmp, y, x)
self.assert_(y is not x)
self.assert_(y[0] is not x[0])
self.assert_(y is y[0])
self.assert_(y[0] is y)
self.assertEqual(len(y), 1)
def test_deepcopy_tuple(self):
x = ([1, 2], 3)
@ -288,7 +288,7 @@ class TestCopy(unittest.TestCase):
x = ([],)
x[0].append(x)
y = copy.deepcopy(x)
self.assertEqual(y, x)
self.assertRaises(RuntimeError, cmp, y, x)
self.assert_(y is not x)
self.assert_(y[0] is not x[0])
self.assert_(y[0][0] is y)
@ -304,10 +304,10 @@ class TestCopy(unittest.TestCase):
x = {}
x['foo'] = x
y = copy.deepcopy(x)
self.assertEqual(y, x)
self.assertRaises(RuntimeError, cmp, y, x)
self.assert_(y is not x)
self.assert_(y['foo'] is y)
self.assertEqual(y, {'foo': y})
self.assertEqual(len(y), 1)
def test_deepcopy_keepalive(self):
memo = {}

63
Lib/test/test_richcmp.py
View File

@ -224,57 +224,36 @@ class MiscTest(unittest.TestCase):
self.assertRaises(Exc, func, Bad())
def test_recursion(self):
# Check comparison for recursive objects
# Check that comparison for recursive objects fails gracefully
from UserList import UserList
a = UserList(); a.append(a)
b = UserList(); b.append(b)
self.assert_(a == b)
self.assert_(not a != b)
a.append(1)
self.assert_(a == a[0])
self.assert_(not a != a[0])
self.assert_(a != b)
self.assert_(not a == b)
b.append(0)
self.assert_(a != b)
self.assert_(not a == b)
a[1] = -1
self.assert_(a != b)
self.assert_(not a == b)
a = UserList()
b = UserList()
a.append(b)
b.append(a)
self.assert_(a == b)
self.assert_(not a != b)
self.assertRaises(RuntimeError, operator.eq, a, b)
self.assertRaises(RuntimeError, operator.ne, a, b)
self.assertRaises(RuntimeError, operator.lt, a, b)
self.assertRaises(RuntimeError, operator.le, a, b)
self.assertRaises(RuntimeError, operator.gt, a, b)
self.assertRaises(RuntimeError, operator.ge, a, b)
b.append(17)
# Even recursive lists of different lengths are different,
# but they cannot be ordered
self.assert_(not (a == b))
self.assert_(a != b)
self.assert_(not a == b)
self.assertRaises(RuntimeError, operator.lt, a, b)
self.assertRaises(RuntimeError, operator.le, a, b)
self.assertRaises(RuntimeError, operator.gt, a, b)
self.assertRaises(RuntimeError, operator.ge, a, b)
a.append(17)
self.assert_(a == b)
self.assert_(not a != b)
def test_recursion2(self):
# This test exercises the circular structure handling code
# in PyObject_RichCompare()
class Weird(object):
def __eq__(self, other):
return self != other
def __ne__(self, other):
return self == other
def __lt__(self, other):
return self > other
def __gt__(self, other):
return self < other
self.assert_(Weird() == Weird())
self.assert_(not (Weird() != Weird()))
for op in opmap["lt"]:
self.assertRaises(ValueError, op, Weird(), Weird())
self.assertRaises(RuntimeError, operator.eq, a, b)
self.assertRaises(RuntimeError, operator.ne, a, b)
a.insert(0, 11)
b.insert(0, 12)
self.assert_(not (a == b))
self.assert_(a != b)
self.assert_(a < b)
class DictTest(unittest.TestCase):

4
Misc/NEWS
View File

@ -47,6 +47,10 @@ Core and builtins
- obj.__contains__() now returns True/False instead of 1/0. SF patch
820195.
- Python no longer tries to be smart about recursive comparisons.
When comparing containers with cyclic references to themselves it
will now just hit the recursion limit. See SF patch 825639.
Extension modules
-----------------

10
Objects/classobject.c
View File

@ -1970,7 +1970,6 @@ instance_iternext(PyInstanceObject *self)
static PyObject *
instance_call(PyObject *func, PyObject *arg, PyObject *kw)
{
PyThreadState *tstate = PyThreadState_GET();
PyObject *res, *call = PyObject_GetAttrString(func, "__call__");
if (call == NULL) {
PyInstanceObject *inst = (PyInstanceObject*) func;
@ -1990,14 +1989,13 @@ instance_call(PyObject *func, PyObject *arg, PyObject *kw)
a() # infinite recursion
This bounces between instance_call() and PyObject_Call() without
ever hitting eval_frame() (which has the main recursion check). */
if (tstate->recursion_depth++ > Py_GetRecursionLimit()) {
PyErr_SetString(PyExc_RuntimeError,
"maximum __call__ recursion depth exceeded");
if (Py_EnterRecursiveCall(" in __call__")) {
res = NULL;
}
else
else {
res = PyObject_Call(call, arg, kw);
tstate->recursion_depth--;
Py_LeaveRecursiveCall();
}
Py_DECREF(call);
return res;
}

188
Objects/object.c
View File

@ -740,120 +740,6 @@ do_cmp(PyObject *v, PyObject *w)
return default_3way_compare(v, w);
}
/* compare_nesting is incremented before calling compare (for
some types) and decremented on exit. If the count exceeds the
nesting limit, enable code to detect circular data structures.
This is a tunable parameter that should only affect the performance
of comparisons, nothing else. Setting it high makes comparing deeply
nested non-cyclical data structures faster, but makes comparing cyclical
data structures slower.
*/
#define NESTING_LIMIT 20
static int compare_nesting = 0;
static PyObject*
get_inprogress_dict(void)
{
static PyObject *key;
PyObject *tstate_dict, *inprogress;
if (key == NULL) {
key = PyString_InternFromString("cmp_state");
if (key == NULL)
return NULL;
}
tstate_dict = PyThreadState_GetDict();
if (tstate_dict == NULL) {
PyErr_BadInternalCall();
return NULL;
}
inprogress = PyDict_GetItem(tstate_dict, key);
if (inprogress == NULL) {
inprogress = PyDict_New();
if (inprogress == NULL)
return NULL;
if (PyDict_SetItem(tstate_dict, key, inprogress) == -1) {
Py_DECREF(inprogress);
return NULL;
}
Py_DECREF(inprogress);
}
return inprogress;
}
/* If the comparison "v op w" is already in progress in this thread, returns
* a borrowed reference to Py_None (the caller must not decref).
* If it's not already in progress, returns "a token" which must eventually
* be passed to delete_token(). The caller must not decref this either
* (delete_token decrefs it). The token must not survive beyond any point
* where v or w may die.
* If an error occurs (out-of-memory), returns NULL.
*/
static PyObject *
check_recursion(PyObject *v, PyObject *w, int op)
{
PyObject *inprogress;
PyObject *token;
Py_uintptr_t iv = (Py_uintptr_t)v;
Py_uintptr_t iw = (Py_uintptr_t)w;
PyObject *x, *y, *z;
inprogress = get_inprogress_dict();
if (inprogress == NULL)
return NULL;
token = PyTuple_New(3);
if (token == NULL)
return NULL;
if (iv <= iw) {
PyTuple_SET_ITEM(token, 0, x = PyLong_FromVoidPtr((void *)v));
PyTuple_SET_ITEM(token, 1, y = PyLong_FromVoidPtr((void *)w));
if (op >= 0)
op = swapped_op[op];
} else {
PyTuple_SET_ITEM(token, 0, x = PyLong_FromVoidPtr((void *)w));
PyTuple_SET_ITEM(token, 1, y = PyLong_FromVoidPtr((void *)v));
}
PyTuple_SET_ITEM(token, 2, z = PyInt_FromLong((long)op));
if (x == NULL || y == NULL || z == NULL) {
Py_DECREF(token);
return NULL;
}
if (PyDict_GetItem(inprogress, token) != NULL) {
Py_DECREF(token);
return Py_None; /* Without INCREF! */
}
if (PyDict_SetItem(inprogress, token, token) < 0) {
Py_DECREF(token);
return NULL;
}
return token;
}
static void
delete_token(PyObject *token)
{
PyObject *inprogress;
if (token == NULL || token == Py_None)
return;
inprogress = get_inprogress_dict();
if (inprogress == NULL)
PyErr_Clear();
else
PyDict_DelItem(inprogress, token);
Py_DECREF(token);
}
/* Compare v to w. Return
-1 if v < w or exception (PyErr_Occurred() true in latter case).
0 if v == w.
@ -867,12 +753,6 @@ PyObject_Compare(PyObject *v, PyObject *w)
PyTypeObject *vtp;
int result;
#if defined(USE_STACKCHECK)
if (PyOS_CheckStack()) {
PyErr_SetString(PyExc_MemoryError, "Stack overflow");
return -1;
}
#endif
if (v == NULL || w == NULL) {
PyErr_BadInternalCall();
return -1;
@ -880,31 +760,10 @@ PyObject_Compare(PyObject *v, PyObject *w)
if (v == w)
return 0;
vtp = v->ob_type;
compare_nesting++;
if (compare_nesting > NESTING_LIMIT &&
(vtp->tp_as_mapping || vtp->tp_as_sequence) &&
!PyString_CheckExact(v) &&
!PyTuple_CheckExact(v)) {
/* try to detect circular data structures */
PyObject *token = check_recursion(v, w, -1);
if (token == NULL) {
result = -1;
}
else if (token == Py_None) {
/* already comparing these objects. assume
they're equal until shown otherwise */
result = 0;
}
else {
result = do_cmp(v, w);
delete_token(token);
}
}
else {
result = do_cmp(v, w);
}
compare_nesting--;
if (Py_EnterRecursiveCall(" in cmp"))
return -1;
result = do_cmp(v, w);
Py_LeaveRecursiveCall();
return result < 0 ? -1 : result;
}
@ -975,41 +834,10 @@ PyObject_RichCompare(PyObject *v, PyObject *w, int op)
PyObject *res;
assert(Py_LT <= op && op <= Py_GE);
if (Py_EnterRecursiveCall(" in cmp"))
return NULL;
compare_nesting++;
if (compare_nesting > NESTING_LIMIT &&
(v->ob_type->tp_as_mapping || v->ob_type->tp_as_sequence) &&
!PyString_CheckExact(v) &&
!PyTuple_CheckExact(v)) {
/* try to detect circular data structures */
PyObject *token = check_recursion(v, w, op);
if (token == NULL) {
res = NULL;
goto Done;
}
else if (token == Py_None) {
/* already comparing these objects with this operator.
assume they're equal until shown otherwise */
if (op == Py_EQ)
res = Py_True;
else if (op == Py_NE)
res = Py_False;
else {
PyErr_SetString(PyExc_ValueError,
"can't order recursive values");
res = NULL;
}
Py_XINCREF(res);
}
else {
res = do_richcmp(v, w, op);
delete_token(token);
}
goto Done;
}
/* No nesting extremism.
If the types are equal, and not old-style instances, try to
/* If the types are equal, and not old-style instances, try to
get out cheap (don't bother with coercions etc.). */
if (v->ob_type == w->ob_type && !PyInstance_Check(v)) {
cmpfunc fcmp;
@ -1041,7 +869,7 @@ PyObject_RichCompare(PyObject *v, PyObject *w, int op)
/* Fast path not taken, or couldn't deliver a useful result. */
res = do_richcmp(v, w, op);
Done:
compare_nesting--;
Py_LeaveRecursiveCall();
return res;
}

56
Python/ceval.c
View File

@ -497,6 +497,7 @@ Py_MakePendingCalls(void)
/* The interpreter's recursion limit */
static int recursion_limit = 1000;
int _Py_CheckRecursionLimit = 1000;
int
Py_GetRecursionLimit(void)
@ -508,8 +509,38 @@ void
Py_SetRecursionLimit(int new_limit)
{
recursion_limit = new_limit;
_Py_CheckRecursionLimit = recursion_limit;
}
/* the macro Py_EnterRecursiveCall() only calls _Py_CheckRecursiveCall()
if the recursion_depth reaches _Py_CheckRecursionLimit.
If USE_STACKCHECK, the macro decrements _Py_CheckRecursionLimit
to guarantee that _Py_CheckRecursiveCall() is regularly called.
Without USE_STACKCHECK, there is no need for this. */
int
_Py_CheckRecursiveCall(char *where)
{
PyThreadState *tstate = PyThreadState_GET();
#ifdef USE_STACKCHECK
if (PyOS_CheckStack()) {
--tstate->recursion_depth;
PyErr_SetString(PyExc_MemoryError, "Stack overflow");
return -1;
}
#endif
if (tstate->recursion_depth > recursion_limit) {
--tstate->recursion_depth;
PyErr_Format(PyExc_RuntimeError,
"maximum recursion depth exceeded%s",
where);
return -1;
}
_Py_CheckRecursionLimit = recursion_limit;
return 0;
}
/* Status code for main loop (reason for stack unwind) */
enum why_code {
@ -674,21 +705,9 @@ eval_frame(PyFrameObject *f)
if (f == NULL)
return NULL;
#ifdef USE_STACKCHECK
if (tstate->recursion_depth%10 == 0 && PyOS_CheckStack()) {
PyErr_SetString(PyExc_MemoryError, "Stack overflow");
return NULL;
}
#endif
/* push frame */
if (++tstate->recursion_depth > recursion_limit) {
--tstate->recursion_depth;
PyErr_SetString(PyExc_RuntimeError,
"maximum recursion depth exceeded");
tstate->frame = f->f_back;
if (Py_EnterRecursiveCall(""))
return NULL;
}
tstate->frame = f;
@ -710,9 +729,7 @@ eval_frame(PyFrameObject *f)
if (call_trace(tstate->c_tracefunc, tstate->c_traceobj,
f, PyTrace_CALL, Py_None)) {
/* Trace function raised an error */
--tstate->recursion_depth;
tstate->frame = f->f_back;
return NULL;
goto exit_eval_frame;
}
}
if (tstate->c_profilefunc != NULL) {
@ -722,9 +739,7 @@ eval_frame(PyFrameObject *f)
tstate->c_profileobj,
f, PyTrace_CALL, Py_None)) {
/* Profile function raised an error */
--tstate->recursion_depth;
tstate->frame = f->f_back;
return NULL;
goto exit_eval_frame;
}
}
}
@ -2428,7 +2443,8 @@ eval_frame(PyFrameObject *f)
reset_exc_info(tstate);
/* pop frame */
--tstate->recursion_depth;
exit_eval_frame:
Py_LeaveRecursiveCall();
tstate->frame = f->f_back;
return retval;