From: Thomas A Caswell <tcaswell@gmail.com>
Date: Thu, 29 Aug 2019 16:30:04 +0000 (-0400)
Subject: bpo-37933: Fix faulthandler.cancel_dump_traceback_later() (GH-15440)
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e278335a6eb049e6028db9a8dcb8baac6cb365ee;p=python

bpo-37933: Fix faulthandler.cancel_dump_traceback_later() (GH-15440)

Fix faulthandler.cancel_dump_traceback_later() call
if cancel_dump_traceback_later() was not called previously.
---

diff --git a/Lib/test/test_faulthandler.py b/Lib/test/test_faulthandler.py
index 1cf20db1c7..b1aa8c3228 100644
--- a/Lib/test/test_faulthandler.py
+++ b/Lib/test/test_faulthandler.py
@@ -817,6 +817,17 @@ class FaultHandlerTests(unittest.TestCase):
         self.assertEqual(output, [])
         self.assertEqual(exitcode, 0xC0000005)
 
+    def test_cancel_later_without_dump_traceback_later(self):
+        # bpo-37933: Calling cancel_dump_traceback_later()
+        # without dump_traceback_later() must not segfault.
+        code = dedent("""
+            import faulthandler
+            faulthandler.cancel_dump_traceback_later()
+        """)
+        output, exitcode = self.get_output(code)
+        self.assertEqual(output, [])
+        self.assertEqual(exitcode, 0)
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c
index 35e7b34c29..011ab5fa28 100644
--- a/Modules/faulthandler.c
+++ b/Modules/faulthandler.c
@@ -631,6 +631,11 @@ faulthandler_thread(void *unused)
 static void
 cancel_dump_traceback_later(void)
 {
+    /* If not scheduled, nothing to cancel */
+    if (!thread.cancel_event) {
+        return;
+    }
+
     /* Notify cancellation */
     PyThread_release_lock(thread.cancel_event);