check if the attribute is set before deleting it with T_OBJECT_EX (fixes #7604)

Also, add a note to the docs about the better behavior of T_OBJECT_EX as
compared to T_OBJECT.

diff --git a/Doc/c-api/structures.rst b/Doc/c-api/structures.rst
index c4fb218749bc26e14f617c817f2a54b544f377ed..c2847e8c95e38e48e61f0618fc230458bde2fa1b 100644 (file)
--- a/Doc/c-api/structures.rst
+++ b/Doc/c-api/structures.rst
@@ -281,7 +281,10 @@ definition with the same method name.
 
    :cmacro:`T_OBJECT` and :cmacro:`T_OBJECT_EX` differ in that
    :cmacro:`T_OBJECT` returns ``None`` if the member is *NULL* and
-   :cmacro:`T_OBJECT_EX` raises an :exc:`AttributeError`.
+   :cmacro:`T_OBJECT_EX` raises an :exc:`AttributeError`.  Try to use
+   :cmacro:`T_OBJECT_EX` over :cmacro:`T_OBJECT` because :cmacro:`T_OBJECT_EX`
+   handles use of the :stmt:`del` statement on that attribute more correctly
+   than :cmacro:`T_OBJECT`.
 
    :attr:`flags` can be 0 for write and read access or :cmacro:`READONLY` for
    read-only access.  Using :cmacro:`T_STRING` for :attr:`type` implies

diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 87d30eb9fafe105542b863d90428ebfb5eafcd4e..10b5af9250cf2f6ee7028e6573c3df756f0de3bd 100644 (file)
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -1166,6 +1166,11 @@ order (MRO) for bases """
             del h
         self.assertEqual(s.getvalue(), '')
 
+        class X(object):
+            __slots__ = "a"
+        with self.assertRaises(AttributeError):
+            del X().a
+
     def test_slots_special(self):
         # Testing __dict__ and __weakref__ in __slots__...
         class D(object):

diff --git a/Misc/NEWS b/Misc/NEWS
index 3098505218cd181578115a5ea83d83173c2b51a6..87242b17362cc354bcbcef057dff05687b6d3c59 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@ What's New in Python 2.7 alpha 2?
 Core and Builtins
 -----------------
 
+- Issue #7604: Deleting an unset slotted attribute did not raise an
+  AttributeError.
+
 - Issue #7534: Fix handling of IEEE specials (infinities, nans,
   negative zero) in ** operator.  The behaviour now conforms to that
   described in C99 Annex F.

diff --git a/Python/structmember.c b/Python/structmember.c
index d2305903303f421e78240254ac0331c77ebaef3c..9f87c076e3d37df6534e492d6aef635b9f9d97d7 100644 (file)
--- a/Python/structmember.c
+++ b/Python/structmember.c
@@ -170,6 +170,8 @@ PyMember_SetOne(char *addr, PyMemberDef *l, PyObject *v)
 {
        PyObject *oldv;
 
+       addr += l->offset;
+
        if ((l->flags & READONLY) || l->type == T_STRING)
        {
                PyErr_SetString(PyExc_TypeError, "readonly attribute");
@@ -179,12 +181,20 @@ PyMember_SetOne(char *addr, PyMemberDef *l, PyObject *v)
                PyErr_SetString(PyExc_RuntimeError, "restricted attribute");
                return -1;
        }
-       if (v == NULL && l->type != T_OBJECT_EX && l->type != T_OBJECT) {
-               PyErr_SetString(PyExc_TypeError,
-                               "can't delete numeric/char attribute");
-               return -1;
+       if (v == NULL) {
+               if (l->type == T_OBJECT_EX) {
+                       /* Check if the attribute is set. */
+                       if (*(PyObject **)addr == NULL) {
+                               PyErr_SetString(PyExc_AttributeError, l->name);
+                               return -1;
+                       }
+               }
+               else if (l->type != T_OBJECT) {
+                       PyErr_SetString(PyExc_TypeError,
+                                       "can't delete numeric/char attribute");
+                       return -1;
+               }
        }
-       addr += l->offset;
        switch (l->type) {
        case T_BOOL:{
                if (!PyBool_Check(v)) {