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Fix segmentation fault on Python 3.13 #960

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Fix segmentation fault on Python 3.13 #960

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452fddb
Fix segmentation fault on Python 3.13
shadchin Nov 27, 2025
d14b921
Re-enable the regular tests for 3.13
shadchin Nov 27, 2025
639f7ee
Add include
shadchin Nov 27, 2025
6ffe4e3
Disable `Py_TPFLAGS_INLINE_VALUES`
shadchin Dec 13, 2025
24da222
Switch to `type->tp_alloc`
shadchin Dec 19, 2025
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3 changes: 1 addition & 2 deletions .github/workflows/ci.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -60,8 +60,7 @@ jobs:
- "3.10"
- "3.11"
- "3.12"
# TODO: Enable this once fixed https://github.com/jcrist/msgspec/issues/910
# - "3.13"
- "3.13"
- "3.14"

steps:
Expand Down
49 changes: 17 additions & 32 deletions src/msgspec/_core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5322,22 +5322,9 @@ ms_maybe_wrap_validation_error(PathNode *path) {
static PyTypeObject StructMixinType;


/* Note this always allocates an UNTRACKED object */
static PyObject *
Struct_alloc(PyTypeObject *type) {
PyObject *obj;
bool is_gc = MS_TYPE_IS_GC(type);

if (is_gc) {
obj = PyObject_GC_New(PyObject, type);
}
else {
obj = PyObject_New(PyObject, type);
}
if (obj == NULL) return NULL;
/* Zero out slot fields */
memset((char *)obj + sizeof(PyObject), '\0', type->tp_basicsize - sizeof(PyObject));
return obj;
return type->tp_alloc(type, type->tp_itemsize);
}

/* Mirrored from cpython Objects/typeobject.c */
Expand Down Expand Up @@ -7489,7 +7476,6 @@ Struct_decode_post_init(StructMetaObject *st_type, PyObject *obj, PathNode *path
return 0;
}

/* ASSUMPTION - obj is untracked and allocated via Struct_alloc */
static int
Struct_fill_in_defaults(StructMetaObject *st_type, PyObject *obj, PathNode *path) {
Py_ssize_t nfields, ndefaults, i;
Expand Down Expand Up @@ -7517,8 +7503,8 @@ Struct_fill_in_defaults(StructMetaObject *st_type, PyObject *obj, PathNode *path
}
}

if (is_gc && !should_untrack)
PyObject_GC_Track(obj);
if (is_gc && should_untrack && MS_IS_TRACKED(obj))
PyObject_GC_UnTrack(obj);

if (Struct_decode_post_init(st_type, obj, path) < 0) return -1;

Expand Down Expand Up @@ -7694,8 +7680,8 @@ Struct_vectorcall(PyTypeObject *cls, PyObject *const *args, size_t nargsf, PyObj
}
}

if (is_gc && !should_untrack)
PyObject_GC_Track(self);
if (is_gc && should_untrack && MS_IS_TRACKED(self))
PyObject_GC_UnTrack(self);

if (Struct_post_init(st_type, self) < 0) goto error;
return self;
Expand Down Expand Up @@ -7930,8 +7916,8 @@ Struct_copy(PyObject *self, PyObject *args)
Struct_set_index(res, i, val);
}
/* If self is tracked, then copy is tracked */
if (MS_OBJECT_IS_GC(self) && MS_IS_TRACKED(self))
PyObject_GC_Track(res);
if (MS_OBJECT_IS_GC(self) && !MS_IS_TRACKED(self))
PyObject_GC_UnTrack(res);
return res;
error:
Py_DECREF(res);
Expand Down Expand Up @@ -8002,9 +7988,8 @@ Struct_replace(
}
}

if (is_gc && !should_untrack) {
PyObject_GC_Track(out);
}
if (is_gc && should_untrack && MS_IS_TRACKED(out))
PyObject_GC_UnTrack(out);
return out;

error:
Expand Down Expand Up @@ -15826,8 +15811,8 @@ mpack_decode_struct_array_inner(
}
if (Struct_decode_post_init(st_type, res, path) < 0) goto error;
Py_LeaveRecursiveCall();
if (is_gc && !should_untrack)
PyObject_GC_Track(res);
if (is_gc && should_untrack && MS_IS_TRACKED(res))
PyObject_GC_UnTrack(res);
return res;
error:
Py_LeaveRecursiveCall();
Expand Down Expand Up @@ -18099,8 +18084,8 @@ json_decode_struct_array_inner(
}
if (Struct_decode_post_init(st_type, out, path) < 0) goto error;
Py_LeaveRecursiveCall();
if (is_gc && !should_untrack)
PyObject_GC_Track(out);
if (is_gc && should_untrack && MS_IS_TRACKED(out))
PyObject_GC_UnTrack(out);
return out;
error:
Py_LeaveRecursiveCall();
Expand Down Expand Up @@ -21250,8 +21235,8 @@ convert_seq_to_struct_array_inner(
}
if (Struct_decode_post_init(st_type, out, path) < 0) goto error;
Py_LeaveRecursiveCall();
if (is_gc && !should_untrack)
PyObject_GC_Track(out);
if (is_gc && should_untrack && MS_IS_TRACKED(out))
PyObject_GC_UnTrack(out);
return out;
error:
Py_LeaveRecursiveCall();
Expand Down Expand Up @@ -21743,8 +21728,8 @@ convert_object_to_struct(
if (Struct_decode_post_init(struct_type, out, path) < 0) goto error;

Py_LeaveRecursiveCall();
if (is_gc && !should_untrack)
PyObject_GC_Track(out);
if (is_gc && should_untrack && MS_IS_TRACKED(out))
PyObject_GC_UnTrack(out);
return out;

error:
Expand Down