From 9ed77358d618e4c65fbe5df67a87618be29fc391 Mon Sep 17 00:00:00 2001
From: Amaury Forgeot d'Arc <amauryfa@gmail.com>
Date: Fri, 4 Apr 2008 23:25:27 +0000
Subject: [PATCH] Issue2221: in Idle, exec('xx') raised a SystemError('error
 return without exception set') instead of the expected NameError

This happens when sys.stdout is redirected to something that cannot flush().
the flush_io() function must be exception-neutral: don't raise, and don't clear exceptions.

Next step: exec() is not supposed to flush sys.stdout...
---
 Lib/test/test_builtin.py | 11 +++++++++++
 Python/pythonrun.c       |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index 111090c1ab0..7244aff8eff 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -448,6 +448,17 @@ class BuiltinTest(unittest.TestCase):
             del l['__builtins__']
         self.assertEqual((g, l), ({'a': 1}, {'b': 2}))
 
+    def test_exec_redirected(self):
+        savestdout = sys.stdout
+        sys.stdout = None # Whatever that cannot flush()
+        try:
+            # Used to raise SystemError('error return without exception set')
+            exec('a')
+        except NameError:
+            pass
+        finally:
+            sys.stdout = savestdout
+
     def test_filter(self):
         self.assertEqual(list(filter(lambda c: 'a' <= c <= 'z', 'Hello World')), list('elloorld'))
         self.assertEqual(list(filter(None, [1, 'hello', [], [3], '', None, 9, 0])), [1, 'hello', [3], 9])
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 74e3430e972..3207fb8b817 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -1467,6 +1467,11 @@ static void
 flush_io(void)
 {
 	PyObject *f, *r;
+	PyObject *type, *value, *traceback;
+
+	/* Save the current exception */
+	PyErr_Fetch(&type, &value, &traceback);
+
 	f = PySys_GetObject("stderr");
 	if (f != NULL) {
 		r = PyObject_CallMethod(f, "flush", "");
@@ -1483,6 +1488,8 @@ flush_io(void)
 		else
 			PyErr_Clear();
 	}
+
+	PyErr_Restore(type, value, traceback);
 }
 
 static PyObject *