Issue #4237: io.FileIO() was raising invalid warnings caused by insufficient initialization of PyFileIOObject struct members.

2 files changed, 11 insertions, 2 deletions

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index bcb37d7..ea965d7 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -1237,6 +1237,13 @@ class MiscIOTest(unittest.TestCase):
             else:
                 self.assert_(issubclass(obj, io.IOBase))
 
+    def test_fileio_warnings(self):
+        with support.check_warnings() as w:
+            self.assertEqual(w.warnings, [])
+            self.assertRaises(TypeError, io.FileIO, [])
+            self.assertEqual(w.warnings, [])
+            self.assertRaises(ValueError, io.FileIO, "/some/invalid/name", "rt")
+            self.assertEqual(w.warnings, [])
 
 def test_main():
     support.run_unittest(IOTest, BytesIOTest, StringIOTest,
diff --git a/Modules/_fileio.c b/Modules/_fileio.c
index 3b0f81b..4b35194 100644
--- a/Modules/_fileio.c
+++ b/Modules/_fileio.c
@@ -86,6 +86,10 @@ fileio_new(PyTypeObject *type, PyObject *args, PyObject *kews)
 	self = (PyFileIOObject *) type->tp_alloc(type, 0);
 	if (self != NULL) {
 		self->fd = -1;
+		self->readable = 0;
+		self->writable = 0;
+		self->seekable = -1;
+		self->closefd = 1;
 		self->weakreflist = NULL;
 	}
 
@@ -179,8 +183,6 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 	    }
 	}
 
-	self->readable = self->writable = 0;
-	self->seekable = -1;
 	s = mode;
 	while (*s) {
 		switch (*s++) {