From 77b286b2ccccc407d8ed17b0543b10f7c1ccc864 Mon Sep 17 00:00:00 2001
From: Nick Coghlan <ncoghlan@gmail.com>
Date: Mon, 27 Jan 2014 00:53:38 +1000
Subject: Close #20105: set __traceback__ when chaining exceptions in C

---
 Objects/exceptions.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

(limited to 'Objects/exceptions.c')

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index bff7f0819e..2531ead50f 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2689,8 +2689,11 @@ _PyErr_TrySetFromCause(const char *format, ...)
      * types as well, but that's quite a bit trickier due to the extra
      * state potentially stored on OSError instances.
      */
-
-    Py_XDECREF(tb);
+    /* Ensure the traceback is set correctly on the existing exception */
+    if (tb != NULL) {
+        PyException_SetTraceback(val, tb);
+        Py_DECREF(tb);
+    }
 
 #ifdef HAVE_STDARG_PROTOTYPES
     va_start(vargs, format);
-- 
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