Issue 1242657: list(obj) can swallow KeyboardInterrupt.

diff --git a/Include/abstract.h b/Include/abstract.h
index b3e7030fa19a50cba5ee450fce1db399c422a50f..f4e31c77c0c8b97264315268614ea98545efb34c 100644 (file)
--- a/Include/abstract.h
+++ b/Include/abstract.h
@@ -392,7 +392,7 @@ xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx*/
        /*
          Guess the size of object o using len(o) or o.__length_hint__().
          If neither of those return a non-negative value, then return the
-         default value.  This function never fails. All exceptions are cleared.
+         default value.  If one of the calls fails, this function returns -1.
        */
 
      PyAPI_FUNC(PyObject *) PyObject_GetItem(PyObject *o, PyObject *key);

diff --git a/Lib/test/test_iterlen.py b/Lib/test/test_iterlen.py
index 72e92a580130e0b4cf17ec21c8df67a31af302d9..2123501bcb55f6599da5d2a989b5e1a0969668de 100644 (file)
--- a/Lib/test/test_iterlen.py
+++ b/Lib/test/test_iterlen.py
@@ -195,6 +195,29 @@ class TestListReversed(TestInvariantWithoutMutations):
         d.extend(range(20))
         self.assertEqual(len(it), 0)
 
+## -- Check to make sure exceptions are not suppressed by __length_hint__()
+
+
+class BadLen(object):
+    def __iter__(self): return iter(range(10))
+    def __len__(self):
+        raise RuntimeError('hello')
+
+class BadLengthHint(object):
+    def __iter__(self): return iter(range(10))
+    def __length_hint__(self):
+        raise RuntimeError('hello')
+
+class TestLengthHintExceptions(unittest.TestCase):
+
+    def test_issue1242657(self):
+        self.assertRaises(RuntimeError, list, BadLen())
+        self.assertRaises(RuntimeError, list, BadLengthHint())
+        self.assertRaises(RuntimeError, [].extend, BadLen())
+        self.assertRaises(RuntimeError, [].extend, BadLengthHint())
+        b = bytearray(range(10))
+        self.assertRaises(RuntimeError, b.extend, BadLen())
+        self.assertRaises(RuntimeError, b.extend, BadLengthHint())
 
 def test_main():
     unittests = [
@@ -210,6 +233,7 @@ def test_main():
         TestSet,
         TestList,
         TestListReversed,
+        TestLengthHintExceptions,
     ]
     support.run_unittest(*unittests)
 

diff --git a/Misc/NEWS b/Misc/NEWS
index 71f9ca19dbf641f628a72ab88a49c84b1c2ded96..54260466306bc7f3b8d29d971e6b2585d9fd2f24 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -17,6 +17,9 @@ Core and Builtins
   the type definition cmpfunc.  The tp_compare slot has been renamed
   to tp_reserved, and is reserved for future usage.
 
+- Issue 1242657: the __len__() and __length_hint__() calls in several tools
+  were suppressing all exceptions.  These include list() and bytearray().
+
 - Issue #4707: round(x, n) now returns an integer if x is an integer.
   Previously it returned a float.
 

diff --git a/Objects/abstract.c b/Objects/abstract.c
index e42008a1488bba4c5b11b5e1a50aa4ba402d50da..86e2c394804b2dd33fe9dbe0937c670623906f80 100644 (file)
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -67,8 +67,8 @@ PyObject_Length(PyObject *o)
 
 /* The length hint function returns a non-negative value from o.__len__()
    or o.__length_hint__().  If those methods aren't found or return a negative
-   value, then the defaultvalue is returned.  This function never fails. 
-   Accordingly, it will mask exceptions raised in either method.
+   value, then the defaultvalue is returned.  If one of the calls fails,
+   this function returns -1.
 */
 
 Py_ssize_t
@@ -82,29 +82,32 @@ _PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)
        rv = PyObject_Size(o);
        if (rv >= 0)
                return rv;
-       if (PyErr_Occurred())
+       if (PyErr_Occurred()) {
+               if (!PyErr_ExceptionMatches(PyExc_TypeError) &&
+                       !PyErr_ExceptionMatches(PyExc_AttributeError))
+                               return -1;
                PyErr_Clear();
+       }
 
        /* cache a hashed version of the attribute string */
        if (hintstrobj == NULL) {
                hintstrobj = PyUnicode_InternFromString("__length_hint__");
                if (hintstrobj == NULL)
-                       goto defaultcase;
+                       return -1;
        }
 
        /* try o.__length_hint__() */
        ro = PyObject_CallMethodObjArgs(o, hintstrobj, NULL);
-       if (ro == NULL)
-               goto defaultcase;
+       if (ro == NULL) {
+               if (!PyErr_ExceptionMatches(PyExc_TypeError) &&
+                       !PyErr_ExceptionMatches(PyExc_AttributeError))
+                               return -1;
+               PyErr_Clear();
+               return defaultvalue;
+       }
        rv = PyLong_AsSsize_t(ro);
        Py_DECREF(ro);
-       if (rv >= 0)
-               return rv;
-
-defaultcase:
-       if (PyErr_Occurred())
-               PyErr_Clear();
-       return defaultvalue;
+       return rv;
 }
 
 PyObject *
@@ -1742,7 +1745,7 @@ PySequence_Tuple(PyObject *v)
 {
        PyObject *it;  /* iter(v) */
        Py_ssize_t n;         /* guess for result tuple size */
-       PyObject *result;
+       PyObject *result = NULL;
        Py_ssize_t j;
 
        if (v == NULL)
@@ -1767,6 +1770,8 @@ PySequence_Tuple(PyObject *v)
 
        /* Guess result size and allocate space. */
        n = _PyObject_LengthHint(v, 10);
+       if (n == -1)
+               goto Fail;
        result = PyTuple_New(n);
        if (result == NULL)
                goto Fail;

diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index 9e93ddaf37c05380efab45c86eaa3b047488aca4..868013a89059990a16b8eb751c6698cdc884bc7f 100644 (file)
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -2616,6 +2616,10 @@ bytes_extend(PyByteArrayObject *self, PyObject *arg)
 
     /* Try to determine the length of the argument. 32 is abitrary. */
     buf_size = _PyObject_LengthHint(arg, 32);
+       if (buf_size == -1) {
+               Py_DECREF(it);
+               return NULL;
+       }
 
     bytes_obj = PyByteArray_FromStringAndSize(NULL, buf_size);
     if (bytes_obj == NULL)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index b8343631f441b8203a316815889ffa9fbee10cdb..2bab4ef26b3082ed4732d0ea3fad7acc16029150 100644 (file)
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -802,6 +802,10 @@ listextend(PyListObject *self, PyObject *b)
 
        /* Guess a result list size. */
        n = _PyObject_LengthHint(b, 8);
+       if (n == -1) {
+               Py_DECREF(it);
+               return NULL;
+       }
        m = Py_SIZE(self);
        mn = m + n;
        if (mn >= m) {