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gh-146152: Fix memory leak in _json encoder error paths #146164

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okiemute04 wants to merge 15 commits into from
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gh-146152: Fix memory leak in _json encoder error paths #146164

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0597100
gh-146152: Fix memory leak in _json encoder recursion path
okiemute04 Mar 19, 2026
9ec9348
Add test for JSON encoder memory leak on recursion error
okiemute04 Mar 20, 2026
cd9cc6f
Add test for JSON encoder memory leak on recursion error
okiemute04 Mar 20, 2026
5428b5e
Use support.gc_collect() in JSON encoder memory leak test
okiemute04 Mar 22, 2026
b68b52b
Trigger CI rebuild
okiemute04 Mar 22, 2026
cafe9ba
Address review feedback for JSON encoder memory leak fix
okiemute04 Mar 22, 2026
a4be61f
Add fresh NEWS entry for JSON encoder memory leak fix
okiemute04 Mar 22, 2026
f7bdb6f
Trigger CI: all review feedback addressed
okiemute04 Mar 22, 2026
f09ce9a
Trigger CI: all review feedback addressed
okiemute04 Mar 22, 2026
5359ecd
Merge branch 'fix-json-encoder-leak' of https://github.com/okiemute04…
okiemute04 Mar 22, 2026
753a88e
Trigger CI: all review comments resolved
okiemute04 Mar 22, 2026
6498f26
Fix test to use infinite_recursion pattern and catch RecursionError
okiemute04 Mar 22, 2026
6b69fea
Merge branch 'fix-json-encoder-leak' of https://github.com/okiemute04…
okiemute04 Mar 22, 2026
81332c7
Fix blank lines
okiemute04 Mar 23, 2026
a9c895e
simplify error path cleanup
okiemute04 Mar 23, 2026
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-03-19-04-18-27.gh-issue-146152.Ifrd7O.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix a memory leak in the :mod:`json` module when encoding objects with a
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custom ``default()`` function that raises an exception, when a recursion
error occurs, or when nested encoding fails.
7 changes: 6 additions & 1 deletion Modules/_json.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1632,8 +1632,12 @@ encoder_listencode_obj(PyEncoderObject *s, PyUnicodeWriter *writer,
}

if (_Py_EnterRecursiveCall(" while encoding a JSON object")) {
if (ident != NULL) {
PyDict_DelItem(s->markers, ident);
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Py_XDECREF(ident);
}
Comment on lines +1635 to +1637
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@picnixz picnixz Mar 23, 2026

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Suggested change
if (ident != NULL) {
int del_rv = PyDict_DelItem(s->markers, ident);
Py_DECREF(ident);
if (del_rv < 0) {
Py_DECREF(newobj);
return -1;
}
}
if (ident != NULL) {
(void)PyDict_DelItem(s->markers, ident);
}

Actually since we are anyway falling through the return -1 case we can simplify this as follows. Then keep the XDECREF for indent. However explicitly suppress the error code of DelItem.

Py_DECREF(newobj);
Py_XDECREF(ident);

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return -1;
}
rv = encoder_listencode_obj(s, writer, newobj, indent_level, indent_cache);
Expand All @@ -1642,6 +1646,7 @@ encoder_listencode_obj(PyEncoderObject *s, PyUnicodeWriter *writer,
Py_DECREF(newobj);
if (rv) {
_PyErr_FormatNote("when serializing %T object", obj);
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@picnixz picnixz Mar 22, 2026

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Please revert this

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@okiemute04 okiemute04 Mar 22, 2026

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okay

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@picnixz picnixz Mar 22, 2026

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Revert cosmetic changes. Nothing was properly reverted.

Py_XDECREF(ident);
return -1;
}
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