https://github.com/python/cpython/commit/1fc2b38d63170dd065efc2bc60e861f32c033b17
commit: 1fc2b38d63170dd065efc2bc60e861f32c033b17
branch: main
author: Mazin Sharaf <[email protected]>
committer: tim-one <[email protected]>
date: 2026-05-02T22:03:13-05:00
summary:
GH-148189: Fix miscalculation of type-specific free list memory use (#148190)
* Fix calculation of PyListObject size in allocator
* Fix size calculation in _PyDict_DebugMallocStats
* Fix memory size calculation in tupleobject.c
Adjusted memory calculation for PyTupleObject freelist entries.
* Revert in tupleobject.c
Removed unnecessary comment regarding memory calculation and the memory
calculation itself.
* 📜🤖 Added by blurb_it.
* Update tupleobject.c
---------
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2026-04-08-02-49-07.gh-issue-148189.0KpXID.rst
M Objects/dictobject.c
M Objects/listobject.c
M Objects/tupleobject.c
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-08-02-49-07.gh-issue-148189.0KpXID.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-08-02-49-07.gh-issue-148189.0KpXID.rst
new file mode 100644
index 00000000000000..d90e30b3d3fba8
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-08-02-49-07.gh-issue-148189.0KpXID.rst
@@ -0,0 +1 @@
+Repaired undercount of bytes in type-specific free lists reported by
sys._debugmallocstats(). For types that participate in cyclic garbage
collection, it was missing two pointers used by GC.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 09db93b2d31820..5be5baf8fc4cfe 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -443,7 +443,7 @@ _PyDict_DebugMallocStats(FILE *out)
{
_PyDebugAllocatorStats(out, "free PyDictObject",
_Py_FREELIST_SIZE(dicts),
- sizeof(PyDictObject));
+ _PyType_PreHeaderSize(&PyDict_Type) +
sizeof(PyDictObject));
_PyDebugAllocatorStats(out, "free PyDictKeysObject",
_Py_FREELIST_SIZE(dictkeys),
sizeof(PyDictKeysObject));
diff --git a/Objects/listobject.c b/Objects/listobject.c
index 685b30bb9eebd6..10e25bbdcdcb6c 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -234,7 +234,7 @@ _PyList_DebugMallocStats(FILE *out)
_PyDebugAllocatorStats(out,
"free PyListObject",
_Py_FREELIST_SIZE(lists),
- sizeof(PyListObject));
+ _PyType_PreHeaderSize(&PyList_Type) +
sizeof(PyListObject));
}
PyObject *
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 7757a102677e2c..753c270f525976 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -1286,6 +1286,6 @@ _PyTuple_DebugMallocStats(FILE *out)
PyOS_snprintf(buf, sizeof(buf),
"free %d-sized PyTupleObject", len);
_PyDebugAllocatorStats(out, buf, _Py_FREELIST_SIZE(tuples[i]),
- _PyObject_VAR_SIZE(&PyTuple_Type, len));
+ _PyType_PreHeaderSize(&PyTuple_Type) +
_PyObject_VAR_SIZE(&PyTuple_Type, len));
}
}
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