gh-151814: Fix unbounded memory growth from repeated empty writes to io.TextIOWrapper#151817
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StanFromIreland
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Jun 20, 2026
| else if (!PyList_CheckExact(self->pending_bytes)) { | ||
| PyObject *list = PyList_New(2); | ||
| if (list == NULL) { | ||
| if (bytes_len > 0) { |
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Git seems to render the diff poorly, locally I see with -w (--ignore-all-space):
$ git show -w HEAD -- Modules/_io/textio.c
commit c6b5163133619febd0fbe8c327e52399b1a54ffd (HEAD -> textio-acc, origin/textio-acc)
Author: Stan Ulbrych <stan@python.org>
Date: Sat Jun 20 21:16:54 2026 +0100
Fix unbounded memory growth from repeated empty writes to io.TextIOWrapper
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index 24e08cec88f..5b2a20a30c2 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -1820,6 +1820,7 @@ _io_TextIOWrapper_write_impl(textio *self, PyObject *text)
}
}
+ if (bytes_len > 0) {
if (self->pending_bytes == NULL) {
assert(self->pending_bytes_count == 0);
self->pending_bytes = b;
@@ -1846,6 +1847,11 @@ _io_TextIOWrapper_write_impl(textio *self, PyObject *text)
}
self->pending_bytes_count += bytes_len;
+ }
+ else {
+ Py_DECREF(b);
+ }
+
if (self->pending_bytes_count >= self->chunk_size || needflush ||
text_needflush) {
if (_textiowrapper_writeflush(self) < 0)
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Cool, thanks! But, it seems to be limited and unfortunately doesn’t support all options, ?ignore-all-space=1 didn't work for me.
StanFromIreland
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io.TextIOWrapper
cmaloney
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Jun 20, 2026
cmaloney
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Jun 21, 2026
StanFromIreland
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needs backport to 3.13
|
Thanks @StanFromIreland for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15. |
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|
Thanks for the review! |
|
GH-152071 is a backport of this pull request to the 3.15 branch. |
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needs backport to 3.15
|
GH-152072 is a backport of this pull request to the 3.14 branch. |
|
GH-152073 is a backport of this pull request to the 3.13 branch. |
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