# HG changeset patch
# Parent 4e84e45e191b3b063387fdd68075f47f4576e215
Issue #22836: Keep exception reports sensible despite errors

diff -r 4e84e45e191b Doc/c-api/exceptions.rst
--- a/Doc/c-api/exceptions.rst	Fri Dec 19 11:21:56 2014 -0500
+++ b/Doc/c-api/exceptions.rst	Wed Jun 10 01:37:18 2015 +0000
@@ -74,8 +74,8 @@
    :meth:`__del__` method.
 
    The function is called with a single argument *obj* that identifies the context
-   in which the unraisable exception occurred. The repr of *obj* will be printed in
-   the warning message.
+   in which the unraisable exception occurred. If possible,
+   the repr of *obj* will be printed in the warning message.
 
 
 Raising exceptions
diff -r 4e84e45e191b Lib/test/test_exceptions.py
--- a/Lib/test/test_exceptions.py	Fri Dec 19 11:21:56 2014 -0500
+++ b/Lib/test/test_exceptions.py	Wed Jun 10 01:37:18 2015 +0000
@@ -7,7 +7,7 @@
 import weakref
 import errno
 
-from test.support import (TESTFN, captured_output, check_impl_detail,
+from test.support import (TESTFN, captured_stderr, check_impl_detail,
                           check_warnings, cpython_only, gc_collect, run_unittest,
                           no_tracing, unlink)
 
@@ -20,6 +20,10 @@
     def __init__(self, x):
         self.x = x
 
+class BrokenStrException(Exception):
+    def __str__(self):
+        raise Exception("str() is broken")
+
 # XXX This is not really enough, each *operation* should be tested!
 
 class ExceptionTests(unittest.TestCase):
@@ -816,7 +820,7 @@
         class MyException(Exception, metaclass=Meta):
             pass
 
-        with captured_output("stderr") as stderr:
+        with captured_stderr() as stderr:
             try:
                 raise KeyError()
             except MyException as e:
@@ -945,6 +949,58 @@
             os.listdir(__file__)
         self.assertEqual(cm.exception.errno, errno.ENOTDIR, cm.exception)
 
+    def test_unraisable(self):
+        # Issue #22836: PyErr_WriteUnraisable() should give sensible reports
+        class BrokenDel:
+            exc_type = ValueError
+            def __del__(self):
+                exc = self.exc_type("del is broken")
+                raise exc
+        class BrokenRepr(BrokenDel):
+            def __repr__(self):
+                raise AttributeError("repr() is broken")
+        class BrokenExceptionDel(BrokenDel):
+            exc_type = BrokenStrException
+        for test_class in (BrokenDel, BrokenRepr, BrokenExceptionDel):
+            with self.subTest(test_class):
+                obj = test_class()
+                with captured_stderr() as stderr:
+                    del obj
+                report = stderr.getvalue()
+                self.assertIn("Exception ignored", report)
+                if test_class is BrokenRepr:
+                    self.assertIn("<repr() failed>", report)
+                else:
+                    self.assertIn(test_class.__del__.__qualname__, report)
+                self.assertIn("test_exceptions.py", report)
+                self.assertIn("raise exc", report)
+                self.assertIn(test_class.exc_type.__name__, report)
+                if test_class.exc_type is BrokenStrException:
+                    self.assertIn("<str() failed>", report)
+                else:
+                    self.assertIn("del is broken", report)
+                self.assertTrue(report.endswith("\n"))
+
+    def test_unhandled(self):
+        # Check for sensible reporting of unhandled exceptions
+        for exc_type in (ValueError, BrokenStrException):
+            with self.subTest(exc_type):
+                try:
+                    exc = exc_type("test message")
+                    raise exc
+                except Exception:
+                    with captured_stderr() as stderr:
+                        sys.__excepthook__(*sys.exc_info())
+                report = stderr.getvalue()
+                self.assertIn("test_exceptions.py", report)
+                self.assertIn("raise exc", report)
+                self.assertIn(exc_type.__name__, report)
+                if exc_type is BrokenStrException:
+                    self.assertIn("<str() failed>", report)
+                else:
+                    self.assertIn("test message", report)
+                self.assertTrue(report.endswith("\n"))
+
 
 class ImportErrorTests(unittest.TestCase):
 
diff -r 4e84e45e191b Python/errors.c
--- a/Python/errors.c	Fri Dec 19 11:21:56 2014 -0500
+++ b/Python/errors.c	Wed Jun 10 01:37:18 2015 +0000
@@ -910,8 +910,12 @@
     if (obj) {
         if (PyFile_WriteString("Exception ignored in: ", f) < 0)
             goto done;
-        if (PyFile_WriteObject(obj, f, 0) < 0)
-            goto done;
+        if (PyFile_WriteObject(obj, f, 0) < 0) {
+            PyErr_Clear();
+            if (PyFile_WriteString("<repr() failed>", f) < 0) {
+                goto done;
+            }
+        }
         if (PyFile_WriteString("\n", f) < 0)
             goto done;
     }
@@ -956,8 +960,12 @@
     if (v && v != Py_None) {
         if (PyFile_WriteString(": ", f) < 0)
             goto done;
-        if (PyFile_WriteObject(v, f, Py_PRINT_RAW) < 0)
-            goto done;
+        if (PyFile_WriteObject(v, f, Py_PRINT_RAW) < 0) {
+            PyErr_Clear();
+            if (PyFile_WriteString("<str() failed>", f) < 0) {
+                goto done;
+            }
+        }
     }
     if (PyFile_WriteString("\n", f) < 0)
         goto done;
diff -r 4e84e45e191b Python/pythonrun.c
--- a/Python/pythonrun.c	Fri Dec 19 11:21:56 2014 -0500
+++ b/Python/pythonrun.c	Wed Jun 10 01:37:18 2015 +0000
@@ -764,8 +764,11 @@
         /* only print colon if the str() of the
            object is not the empty string
         */
-        if (s == NULL)
+        if (s == NULL) {
+            PyErr_Clear();
             err = -1;
+            err += PyFile_WriteString(": <str() failed>", f);
+        }
         else if (!PyUnicode_Check(s) ||
             PyUnicode_GetLength(s) != 0)
             err = PyFile_WriteString(": ", f);
@@ -774,6 +777,9 @@
         Py_XDECREF(s);
     }
     /* try to write a newline in any case */
+    if (err < 0) {
+        PyErr_Clear();
+    }
     err += PyFile_WriteString("\n", f);
     Py_XDECREF(tb);
     Py_DECREF(value);