Merge from py3k branch:

Correction for issue1265 (pdb bug with "with" statement).

When an unfinished generator-iterator is garbage collected, PyEval_EvalFrameEx
is called with a GeneratorExit exception set.  This leads to funny results
if the sys.settrace function itself makes use of generators.
A visible effect is that the settrace function is reset to None.
Another is that the eventual "finally" block of the generator is not called.

It is necessary to save/restore the exception around the call to the trace
function.

This happens a lot with py3k: isinstance() of an ABCMeta instance runs
    def __instancecheck__(cls, instance):
        """Override for isinstance(instance, cls)."""
        return any(cls.__subclasscheck__(c)
                   for c in {instance.__class__, type(instance)})
which lets an opened generator expression each time it returns True.

Backport candidate, even if the case is less frequent in 2.5.

1 files changed, 4 insertions, 0 deletions

diff --git a/Misc/NEWS b/Misc/NEWS
index dfc5256..9da2ba8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,10 @@ What's New in Python 2.6 alpha 1?
 Core and builtins
 -----------------
 
+- Issue #1265: Fix a problem with sys.settrace, if the tracing function uses a
+  generator expression when at the same time the executed code is closing a
+  paused generator.
+
 - sets and frozensets now have an isdisjoint() method.
 
 - optimize the performance of builtin.sum().