Issue #5016: FileIO.seekable() could return False if the file position
was negative when truncated to a C int. Patch by Victor Stinner.
diff --git a/Lib/test/test_largefile.py b/Lib/test/test_largefile.py
index 584a206..d932659 100644
--- a/Lib/test/test_largefile.py
+++ b/Lib/test/test_largefile.py
@@ -133,6 +133,15 @@
f.seek(0)
self.assertEqual(len(f.read()), 1) # else wasn't truncated
+ def test_seekable(self):
+ # Issue #5016; seekable() can return False when the current position
+ # is negative when truncated to an int.
+ for pos in (2**31-1, 2**31, 2**31+1):
+ with self.open(TESTFN, 'rb') as f:
+ f.seek(pos)
+ self.assert_(f.seekable())
+
+
def test_main():
# On Windows and Mac OSX this test comsumes large resources; It
# takes a long time to build the >2GB file and takes >2GB of disk
@@ -172,6 +181,7 @@
with _open(TESTFN, 'wb') as f:
if hasattr(f, 'truncate'):
suite.addTest(TestCase('test_truncate'))
+ suite.addTest(TestCase('test_seekable'))
unlink(TESTFN)
try:
run_unittest(suite)
diff --git a/Misc/NEWS b/Misc/NEWS
index 21b4a9b..d1b1463 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -21,6 +21,9 @@
- The error detection code in FileIO.close() could fail to reflect the `errno`
value, and report it as -1 instead.
+- Issue #5016: FileIO.seekable() could return False if the file position
+ was negative when truncated to a C int. Patch by Victor Stinner.
+
What's New in Python 3.1 alpha 1
================================
diff --git a/Modules/_fileio.c b/Modules/_fileio.c
index 32f6790..88ee54c 100644
--- a/Modules/_fileio.c
+++ b/Modules/_fileio.c
@@ -66,6 +66,8 @@
static PyObject *
portable_lseek(int fd, PyObject *posobj, int whence);
+static PyObject *portable_lseek(int fd, PyObject *posobj, int whence);
+
/* Returns 0 on success, -1 with exception set on failure. */
static int
internal_close(PyFileIOObject *self)
@@ -441,14 +443,14 @@
if (self->fd < 0)
return err_closed();
if (self->seekable < 0) {
- int ret;
- Py_BEGIN_ALLOW_THREADS
- ret = lseek(self->fd, 0, SEEK_CUR);
- Py_END_ALLOW_THREADS
- if (ret < 0)
+ PyObject *pos = portable_lseek(self->fd, NULL, SEEK_CUR);
+ if (pos == NULL) {
+ PyErr_Clear();
self->seekable = 0;
- else
+ } else {
+ Py_DECREF(pos);
self->seekable = 1;
+ }
}
return PyBool_FromLong((long) self->seekable);
}