From e2bd2a718602bf6d6d607fc9a0b7574a18874847 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 8 Oct 2014 22:31:52 +0300
Subject: Issue #21715: Extracted shared complicated code in the _io module to
 new _PyErr_ChainExceptions() function.

---
 Include/pyerrors.h       |  4 +++-
 Modules/_io/_iomodule.c  | 15 ++-------------
 Modules/_io/bufferedio.c | 16 ++--------------
 Modules/_io/textio.c     | 16 ++--------------
 Python/errors.c          | 24 ++++++++++++++++++++++++
 5 files changed, 33 insertions(+), 42 deletions(-)

diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index e44fb5f..02f65d6 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -123,7 +123,9 @@ PyAPI_FUNC(void) PyException_SetCause(PyObject *, PyObject *);
 /* Context manipulation (PEP 3134) */
 PyAPI_FUNC(PyObject *) PyException_GetContext(PyObject *);
 PyAPI_FUNC(void) PyException_SetContext(PyObject *, PyObject *);
-
+#ifndef Py_LIMITED_API
+PyAPI_FUNC(void) _PyErr_ChainExceptions(PyObject *, PyObject *, PyObject *);
+#endif
 
 /* */
 
diff --git a/Modules/_io/_iomodule.c b/Modules/_io/_iomodule.c
index 7c4f9cb..45c31a5 100644
--- a/Modules/_io/_iomodule.c
+++ b/Modules/_io/_iomodule.c
@@ -468,19 +468,8 @@ io_open(PyObject *self, PyObject *args, PyObject *kwds)
         PyObject *exc, *val, *tb, *close_result;
         PyErr_Fetch(&exc, &val, &tb);
         close_result = _PyObject_CallMethodId(result, &PyId_close, NULL);
-        if (close_result != NULL) {
-            Py_DECREF(close_result);
-            PyErr_Restore(exc, val, tb);
-        } else {
-            PyObject *exc2, *val2, *tb2;
-            PyErr_Fetch(&exc2, &val2, &tb2);
-            PyErr_NormalizeException(&exc, &val, &tb);
-            Py_XDECREF(exc);
-            Py_XDECREF(tb);
-            PyErr_NormalizeException(&exc2, &val2, &tb2);
-            PyException_SetContext(val2, val);
-            PyErr_Restore(exc2, val2, tb2);
-        }
+        _PyErr_ChainExceptions(exc, val, tb);
+        Py_XDECREF(close_result);
         Py_DECREF(result);
     }
     Py_XDECREF(modeobj);
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 302db0a..8084aae 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -543,20 +543,8 @@ buffered_close(buffered *self, PyObject *args)
     }
 
     if (exc != NULL) {
-        if (res != NULL) {
-            Py_CLEAR(res);
-            PyErr_Restore(exc, val, tb);
-        }
-        else {
-            PyObject *exc2, *val2, *tb2;
-            PyErr_Fetch(&exc2, &val2, &tb2);
-            PyErr_NormalizeException(&exc, &val, &tb);
-            Py_DECREF(exc);
-            Py_XDECREF(tb);
-            PyErr_NormalizeException(&exc2, &val2, &tb2);
-            PyException_SetContext(val2, val);
-            PyErr_Restore(exc2, val2, tb2);
-        }
+        _PyErr_ChainExceptions(exc, val, tb);
+        Py_CLEAR(res);
     }
 
 end:
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index 635093e..a3e82a8 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -2608,20 +2608,8 @@ textiowrapper_close(textio *self, PyObject *args)
 
         res = _PyObject_CallMethodId(self->buffer, &PyId_close, NULL);
         if (exc != NULL) {
-            if (res != NULL) {
-                Py_CLEAR(res);
-                PyErr_Restore(exc, val, tb);
-            }
-            else {
-                PyObject *exc2, *val2, *tb2;
-                PyErr_Fetch(&exc2, &val2, &tb2);
-                PyErr_NormalizeException(&exc, &val, &tb);
-                Py_DECREF(exc);
-                Py_XDECREF(tb);
-                PyErr_NormalizeException(&exc2, &val2, &tb2);
-                PyException_SetContext(val2, val);
-                PyErr_Restore(exc2, val2, tb2);
-            }
+            _PyErr_ChainExceptions(exc, val, tb);
+            Py_CLEAR(res);
         }
         return res;
     }
diff --git a/Python/errors.c b/Python/errors.c
index 996292a..a980481 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -384,6 +384,30 @@ PyErr_SetExcInfo(PyObject *p_type, PyObject *p_value, PyObject *p_traceback)
     Py_XDECREF(oldtraceback);
 }
 
+/* Like PyErr_Restore(), but if an exception is already set,
+   set the context associated with it.
+ */
+void
+_PyErr_ChainExceptions(PyObject *exc, PyObject *val, PyObject *tb)
+{
+    if (exc == NULL)
+        return;
+
+    if (PyErr_Occurred()) {
+        PyObject *exc2, *val2, *tb2;
+        PyErr_Fetch(&exc2, &val2, &tb2);
+        PyErr_NormalizeException(&exc, &val, &tb);
+        Py_DECREF(exc);
+        Py_XDECREF(tb);
+        PyErr_NormalizeException(&exc2, &val2, &tb2);
+        PyException_SetContext(val2, val);
+        PyErr_Restore(exc2, val2, tb2);
+    }
+    else {
+        PyErr_Restore(exc, val, tb);
+    }
+}
+
 /* Convenience functions to set a type error exception and return 0 */
 
 int
-- 
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