From 69c88f74a377380eb34e1040f320039e3ab4d014 Mon Sep 17 00:00:00 2001
From: Benjamin Peterson <benjamin@python.org>
Date: Thu, 31 Jul 2008 01:47:08 +0000
Subject: Merged revisions 65320 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/trunk

........
  r65320 | amaury.forgeotdarc | 2008-07-30 19:42:16 -0500 (Wed, 30 Jul 2008) | 3 lines

  #2542: now that issubclass() may call arbitrary code,
  make sure that PyErr_ExceptionMatches returns 0 when an exception occurs there.
........
---
 Lib/test/test_exceptions.py | 35 +++++++++++++++++++++++++++++++++--
 Python/errors.c             | 15 ++++++++++++---
 2 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index aa77292..2b248e1 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -6,12 +6,20 @@ import unittest
 import pickle
 import weakref
 
-from test.support import TESTFN, unlink, run_unittest
+from test.support import TESTFN, unlink, run_unittest, captured_output
 
 # XXX This is not really enough, each *operation* should be tested!
 
 class ExceptionTests(unittest.TestCase):
 
+    def test00(self):
+        try:
+            sys.exit(ValueError('aaa'))
+        except SystemExit:
+            pass
+        finally:
+            pass
+
     def raise_catch(self, exc, excname):
         try:
             raise exc("spam")
@@ -404,7 +412,6 @@ class ExceptionTests(unittest.TestCase):
     def testExceptionCleanupNames(self):
         # Make sure the local variable bound to the exception instance by
         # an "except" statement is only visible inside the except block.
-
         try:
             raise Exception()
         except Exception as e:
@@ -565,6 +572,30 @@ class ExceptionTests(unittest.TestCase):
             pass
         self.assertEquals(e, (None, None, None))
 
+    def test_badisinstance(self):
+        # Bug #2542: if issubclass(e, MyException) raises an exception,
+        # it should be ignored
+        class Meta(type):
+            def __subclasscheck__(cls, subclass):
+                raise ValueError()
+        class MyException(Exception, metaclass=Meta):
+            pass
+
+        with captured_output("stderr") as stderr:
+            try:
+                raise KeyError()
+            except MyException as e:
+                self.fail("exception should not be a MyException")
+            except KeyError:
+                pass
+            except:
+                self.fail("Should have raised TypeError")
+            else:
+                self.fail("Should have raised TypeError")
+        self.assertEqual(stderr.getvalue(),
+                         "Exception ValueError: ValueError() "
+                         "in <class 'KeyError'> ignored\n")
+
 def test_main():
     run_unittest(ExceptionTests)
 
diff --git a/Python/errors.c b/Python/errors.c
index 3b86c48..a06ec02 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -157,9 +157,18 @@ PyErr_GivenExceptionMatches(PyObject *err, PyObject *exc)
 		err = PyExceptionInstance_Class(err);
 
 	if (PyExceptionClass_Check(err) && PyExceptionClass_Check(exc)) {
-		/* problems here!?  not sure PyObject_IsSubclass expects to
-		   be called with an exception pending... */
-		return PyObject_IsSubclass(err, exc);
+		int res = 0;
+		PyObject *exception, *value, *tb;
+		PyErr_Fetch(&exception, &value, &tb);
+		res = PyObject_IsSubclass(err, exc);
+		/* This function must not fail, so print the error here */
+		if (res == -1) {
+			PyErr_WriteUnraisable(err);
+			/* issubclass did not succeed */
+			res = 0;
+		}
+		PyErr_Restore(exception, value, tb);
+		return res;
 	}
 
 	return err == exc;
-- 
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