[Python-checkins] cpython (2.7): Issue #13070: Fix a crash when a TextIOWrapper caught in a reference cycle

[charles-francois.natali]

http://hg.python.org/cpython/rev/89b9e4bf6f1f
changeset:   72754:89b9e4bf6f1f
branch:      2.7
parent:      72725:83c486c1112c
user:        Charles-François Natali <neologix at free.fr>
date:        Thu Oct 06 19:09:45 2011 +0200
summary:
  Issue #13070: Fix a crash when a TextIOWrapper caught in a reference cycle
would be finalized after the reference to its underlying BufferedRWPair's
writer got cleared by the GC.

files:
  Lib/test/test_io.py      |  15 +++++++++++++++
  Misc/NEWS                |   4 ++++
  Modules/_io/bufferedio.c |   5 +++++
  3 files changed, 24 insertions(+), 0 deletions(-)


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
@@ -2338,6 +2338,21 @@
         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's writer got
+        # cleared by the GC.
+        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/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -217,6 +217,10 @@
 Extension Modules
 -----------------
 
+- Issue #13070: Fix a crash when a TextIOWrapper caught in a reference cycle
+  would be finalized after the reference to its underlying BufferedRWPair's
+  writer got cleared by the GC.
+
 - Issue #12881: ctypes: Fix segfault with large structure field names.
 
 - Issue #13013: ctypes: Fix a reference leak in PyCArrayType_from_ctype.
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -2179,6 +2179,11 @@
 static PyObject *
 bufferedrwpair_closed_get(rwpair *self, void *context)
 {
+    if (self->writer == NULL) {
+        PyErr_SetString(PyExc_RuntimeError,
+                "the BufferedRWPair object is being garbage-collected");
+        return NULL;
+    }
     return PyObject_GetAttr((PyObject *) self->writer, _PyIO_str_closed);
 }
 

-- 
Repository URL: http://hg.python.org/cpython