[Python-checkins] cpython (2.7): prevent writing to stderr from messing up the exception state (closes #14474)

[benjamin.peterson]

http://hg.python.org/cpython/rev/8609d7fcdcc7
changeset:   76066:8609d7fcdcc7
branch:      2.7
parent:      76049:d3a82a26c705
user:        Benjamin Peterson <benjamin at python.org>
date:        Mon Apr 02 11:15:17 2012 -0400
summary:
  prevent writing to stderr from messing up the exception state (closes #14474)

files:
  Lib/test/test_thread.py |  24 ++++++++++++++++++++++++
  Misc/NEWS               |   3 +++
  Modules/threadmodule.c  |   3 +++
  3 files changed, 30 insertions(+), 0 deletions(-)


diff --git a/Lib/test/test_thread.py b/Lib/test/test_thread.py
--- a/Lib/test/test_thread.py
+++ b/Lib/test/test_thread.py
@@ -130,6 +130,30 @@
             time.sleep(0.01)
         self.assertEqual(thread._count(), orig)
 
+    def test_save_exception_state_on_error(self):
+        # See issue #14474
+        def task():
+            started.release()
+            sys.stderr = stderr
+            raise SyntaxError
+        def mywrite(self, *args):
+            try:
+                raise ValueError
+            except ValueError:
+                pass
+            real_write(self, *args)
+        c = thread._count()
+        started = thread.allocate_lock()
+        with test_support.captured_output("stderr") as stderr:
+            real_write = stderr.write
+            stderr.write = mywrite
+            started.acquire()
+            thread.start_new_thread(task, ())
+            started.acquire()
+            while thread._count() > c:
+                pass
+        self.assertIn("Traceback", stderr.getvalue())
+
 
 class Barrier:
     def __init__(self, num_threads):
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -9,6 +9,9 @@
 Core and Builtins
 -----------------
 
+- Issue #14474: Save and restore exception state in thread.start_new_thread()
+  while writing error message if the thread leaves a unhandled exception.
+
 - Issue #13019: Fix potential reference leaks in bytearray.extend().  Patch
   by Suman Saha.
 
diff --git a/Modules/threadmodule.c b/Modules/threadmodule.c
--- a/Modules/threadmodule.c
+++ b/Modules/threadmodule.c
@@ -618,6 +618,8 @@
             PyErr_Clear();
         else {
             PyObject *file;
+            PyObject *exc, *value, *tb;
+            PyErr_Fetch(&exc, &value, &tb);
             PySys_WriteStderr(
                 "Unhandled exception in thread started by ");
             file = PySys_GetObject("stderr");
@@ -625,6 +627,7 @@
                 PyFile_WriteObject(boot->func, file, 0);
             else
                 PyObject_Print(boot->func, stderr, 0);
+            PyErr_Restore(exc, value, tb);
             PySys_WriteStderr("\n");
             PyErr_PrintEx(0);
         }

-- 
Repository URL: http://hg.python.org/cpython