[issue13070] segmentation fault in pure-python multi-threaded server

[Charles-François Natali]

Charles-François Natali <neologix at free.fr> added the comment:

Sorry, forgot about this issue...
Updated patch (I'm not really satisfied with the error message, don't
hesitate if you can think of a better wording).

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Added file: http://bugs.python.org/file23319/buffered_closed_gc-3.diff

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue13070>
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diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -2421,6 +2421,20 @@
         with self.open(support.TESTFN, "rb") as f:
             self.assertEqual(f.read(), b"456def")
 
+    def test_rwpair_cleared_before_textio(self):
+        # Issue 13070: TextIOWrapper's finalization would crash when called
+        # after the reference to the underlying BufferedRWPair got cleared.
+        for i in range(1000):
+            b1 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
+            t1 = self.TextIOWrapper(b1, encoding="ascii")
+            b2 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
+            t2 = self.TextIOWrapper(b2, encoding="ascii")
+            # circular references
+            t1.buddy = t2
+            t2.buddy = t1
+        support.gc_collect()
+
+
 class PyTextIOWrapperTest(TextIOWrapperTest):
     pass
 
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -2307,6 +2307,10 @@
 static PyObject *
 bufferedrwpair_closed_get(rwpair *self, void *context)
 {
+    if (self->writer == NULL) {
+        PyErr_SetString(PyExc_RuntimeError, "the writer object has been cleared");
+        return NULL;
+    }
     return PyObject_GetAttr((PyObject *) self->writer, _PyIO_str_closed);
 }