bpo-37076: _thread.start_new_thread() calls _PyErr_WriteUnraisableMsg() (GH-13617)

_thread.start_new_thread() now logs uncaught exception raised by the
function using sys.unraisablehook(), rather than sys.excepthook(), so
the hook gets access to the function which raised the exception.

1 files changed, 18 insertions, 0 deletions

diff --git a/Lib/test/test_thread.py b/Lib/test/test_thread.py
index f4eb830..f946f7b 100644
--- a/Lib/test/test_thread.py
+++ b/Lib/test/test_thread.py
@@ -154,6 +154,24 @@ class ThreadRunningTests(BasicThreadTest):
                 started.acquire()
         self.assertIn("Traceback", stderr.getvalue())
 
+    def test_unraisable_exception(self):
+        def task():
+            started.release()
+            raise ValueError("task failed")
+
+        started = thread.allocate_lock()
+        with support.catch_unraisable_exception() as cm:
+            with support.wait_threads_exit():
+                started.acquire()
+                thread.start_new_thread(task, ())
+                started.acquire()
+
+            self.assertEqual(str(cm.unraisable.exc_value), "task failed")
+            self.assertIs(cm.unraisable.object, task)
+            self.assertEqual(cm.unraisable.err_msg,
+                             "Exception ignored in thread started by")
+            self.assertIsNotNone(cm.unraisable.exc_traceback)
+
 
 class Barrier:
     def __init__(self, num_threads):