diff -r cd282dd0cfe8 Lib/_pyio.py
--- a/Lib/_pyio.py	Thu Dec 04 01:26:35 2014 -0500
+++ b/Lib/_pyio.py	Thu Dec 04 15:00:35 2014 +0100
@@ -1168,6 +1168,7 @@
         self.buffer_size = buffer_size
         self._write_buf = bytearray()
         self._write_lock = Lock()
+        _register_writer(self)
 
     def write(self, b):
         if self.closed:
@@ -2182,3 +2183,18 @@
     def detach(self):
         # This doesn't make sense on StringIO.
         self._unsupported("detach")
+
+
+# ____________________________________________________________
+
+import atexit, weakref
+
+_all_writers = weakref.WeakKeyDictionary()
+
+def _register_writer(w):
+    _all_writers[w] = True
+
+def _flush_all_writers():
+    for w in _all_writers:
+        w.flush()
+atexit.register(_flush_all_writers)
diff -r cd282dd0cfe8 Modules/_io/_iomodule.c
--- a/Modules/_io/_iomodule.c	Thu Dec 04 01:26:35 2014 -0500
+++ b/Modules/_io/_iomodule.c	Thu Dec 04 15:00:35 2014 +0100
@@ -758,6 +758,8 @@
         !(_PyIO_zero = PyLong_FromLong(0L)))
         goto fail;
 
+    _Py_PyAtExit(_PyIO_atexit_flush);
+
     state->initialized = 1;
 
     return m;
diff -r cd282dd0cfe8 Modules/_io/_iomodule.h
--- a/Modules/_io/_iomodule.h	Thu Dec 04 01:26:35 2014 -0500
+++ b/Modules/_io/_iomodule.h	Thu Dec 04 15:00:35 2014 +0100
@@ -170,3 +170,5 @@
 extern PyObject *_PyIO_zero;
 
 extern PyTypeObject _PyBytesIOBuffer_Type;
+
+extern void _PyIO_atexit_flush(void);
diff -r cd282dd0cfe8 Modules/_io/bufferedio.c
--- a/Modules/_io/bufferedio.c	Thu Dec 04 01:26:35 2014 -0500
+++ b/Modules/_io/bufferedio.c	Thu Dec 04 15:00:35 2014 +0100
@@ -242,6 +242,10 @@
 };
 
 
+struct doubly_linked_s {
+    struct doubly_linked_s *prev, *next;
+};
+
 typedef struct {
     PyObject_HEAD
 
@@ -286,8 +290,15 @@
 
     PyObject *dict;
     PyObject *weakreflist;
+
+    /* a doubly-linked chained list of "buffered" objects that need to
+       be flushed when the process exits */
+    struct doubly_linked_s buffered_writers_list;
 } buffered;
 
+static struct doubly_linked_s doubly_linked_end = {
+    &doubly_linked_end, &doubly_linked_end };
+
 /*
     Implementation notes:
 
@@ -412,6 +423,15 @@
 
 
 static void
+remove_from_linked_list(buffered *self)
+{
+    self->buffered_writers_list.next->prev = self->buffered_writers_list.prev;
+    self->buffered_writers_list.prev->next = self->buffered_writers_list.next;
+    self->buffered_writers_list.prev = NULL;
+    self->buffered_writers_list.next = NULL;
+}
+
+static void
 buffered_dealloc(buffered *self)
 {
     self->finalizing = 1;
@@ -419,6 +439,8 @@
         return;
     _PyObject_GC_UNTRACK(self);
     self->ok = 0;
+    if (self->buffered_writers_list.next != NULL)
+        remove_from_linked_list(self);
     if (self->weakreflist != NULL)
         PyObject_ClearWeakRefs((PyObject *)self);
     Py_CLEAR(self->raw);
@@ -1911,10 +1933,28 @@
     self->fast_closed_checks = (Py_TYPE(self) == &PyBufferedWriter_Type &&
                                 Py_TYPE(raw) == &PyFileIO_Type);
 
+    if (self->buffered_writers_list.next == NULL) {
+        self->buffered_writers_list.prev = &doubly_linked_end;
+        self->buffered_writers_list.next = doubly_linked_end.next;
+        doubly_linked_end.next->prev = &self->buffered_writers_list;
+        doubly_linked_end.next = &self->buffered_writers_list;
+    }
+
     self->ok = 1;
     return 0;
 }
 
+void _PyIO_atexit_flush(void)
+{
+    while (doubly_linked_end.next != &doubly_linked_end) {
+        buffered *buf = (buffered *)(((char *)doubly_linked_end.next) -
+                                     offsetof(buffered, buffered_writers_list));
+        remove_from_linked_list(buf);
+        buffered_flush(buf, NULL);
+        PyErr_Clear();
+    }
+}
+
 static Py_ssize_t
 _bufferedwriter_raw_write(buffered *self, char *start, Py_ssize_t len)
 {