https://github.com/python/cpython/commit/db68bfc771e6a85573732e0b579e8f68841c9b5c
commit: db68bfc771e6a85573732e0b579e8f68841c9b5c
branch: main
author: Cody Maloney <[email protected]>
committer: encukou <[email protected]>
date: 2025-09-18T12:02:29+02:00
summary:
gh-138720: Make Buffered closed check match flush (GH-138724)
In `_io__Buffered_flush_impl` the macro `CHECK_CLOSED` is used to check
the `buffered*` is in a good state to be flushed. That differs slightly
from `buffered_closed`.
In some cases, that difference would result in `close()` thinking the
file needed to be flushed and closed while `flush()` thought the file
was already closed.
This could happen during GC and would result in an unraisable exception.
files:
A Misc/NEWS.d/next/Library/2025-09-09-17-57-49.gh-issue-138720.hAtsm-.rst
M Lib/test/test_io/test_general.py
M Modules/_io/bufferedio.c
diff --git a/Lib/test/test_io/test_general.py b/Lib/test/test_io/test_general.py
index c2f0e1877a6901..b9abea71e01f0b 100644
--- a/Lib/test/test_io/test_general.py
+++ b/Lib/test/test_io/test_general.py
@@ -1980,6 +1980,10 @@ def test_readinto(self):
self.assertEqual(getattr(pair, method)(data), 5)
self.assertEqual(bytes(data), b"abcde")
+ # gh-138720: C BufferedRWPair would destruct in a bad order resulting
in
+ # an unraisable exception.
+ support.gc_collect()
+
def test_write(self):
w = self.MockRawIO()
pair = self.tp(self.MockRawIO(), w)
diff --git
a/Misc/NEWS.d/next/Library/2025-09-09-17-57-49.gh-issue-138720.hAtsm-.rst
b/Misc/NEWS.d/next/Library/2025-09-09-17-57-49.gh-issue-138720.hAtsm-.rst
new file mode 100644
index 00000000000000..4f3f54e1deb89f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-09-09-17-57-49.gh-issue-138720.hAtsm-.rst
@@ -0,0 +1,4 @@
+Fix an issue where :class:`io.BufferedWriter` and :class:`io.BufferedRandom`
+had different definitions of "closed" for :meth:`~io.IOBase.close` and
+:meth:`~io.IOBase.flush` which resulted in an exception when close called
+flush but flush thought the file was already closed.
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index d0fe7ad61547da..2d2559c8219230 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -553,8 +553,8 @@ _io__Buffered_close_impl(buffered *self)
if (!ENTER_BUFFERED(self)) {
return NULL;
}
-
- r = buffered_closed(self);
+ /* gh-138720: Use IS_CLOSED to match flush CHECK_CLOSED. */
+ r = IS_CLOSED(self);
if (r < 0)
goto end;
if (r > 0) {
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