Issue 3611: in some cases (a __del__ re-raising an exception, when called from inside

an 'except' clause), the exception __context__ would be reset to None.
This crases the interpreter if this precisely happens inside PyErr_SetObject.

- now the __context__ is properly preserved
- in any case, PyErr_SetObject now saves the current exc_value in a local variable, to
avoid such crashes in the future.

Reviewer: Antoine Pitrou.

Lib/test/test_raise.py

@@ -324,6 +324,30 @@ class TestContext(unittest.TestCase):
 
         f()
 
+    def test_3611(self):
+        # A re-raised exception in a __del__ caused the __context__
+        # to be cleared
+        class C:
+            def __del__(self):
+                try:
+                    1/0
+                except:
+                    raise
+
+        def f():
+            x = C()
+            try:
+                try:
+                    x.x
+                except AttributeError:
+                    del x
+                    raise TypeError
+            except Exception as e:
+                self.assertNotEqual(e.__context__, None)
+                self.assert_(isinstance(e.__context__, AttributeError))
+
+        with support.captured_output("stderr"):
+            f()
 
 class TestRemovedFunctionality(unittest.TestCase):
     def test_tuples(self):