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gh-117142: Slightly hacky fix for memory leak of StgInfo #119424

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Merged
merged 4 commits into from
May 23, 2024
Merged

gh-117142: Slightly hacky fix for memory leak of StgInfo #119424

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c3fdc38
gh-117142: Slightliy hacky fix for memory leak of StgInfo
encukou May 22, 2024
6aa0075
Mark _ctypes as safe for multiple interpreters
encukou May 22, 2024
d535ff2
Remove get_module_state_by_def_final
encukou May 22, 2024
c73d0be
Align PyType_Type.tp_basicsize up
encukou May 23, 2024
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gh-117142: Slightliy hacky fix for memory leak of StgInfo 
Add a funciton that inlines PyObject_GetTypeData and skips
type-checking, so it doesn't need access to the CType_Type object.
This will break if the memory layout changes, but should
be an acceptable solution to enable ctypes in subinterpreters in
Python 3.13.
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@encukou
encukou committed May 22, 2024
commit c3fdc38fa664dbe239858fc477dcd1b0b51ad4ac
68 changes: 30 additions & 38 deletions Modules/_ctypes/_ctypes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -454,20 +454,17 @@ class _ctypes.CType_Type "PyObject *" "clinic_state()->CType_Type"
static int
CType_Type_traverse(PyObject *self, visitproc visit, void *arg)
{
ctypes_state *st = get_module_state_by_def_final(Py_TYPE(self));
if (st && st->PyCType_Type) {
StgInfo *info;
if (PyStgInfo_FromType(st, self, &info) < 0) {
PyErr_WriteUnraisable(self);
}
if (info) {
Py_VISIT(info->proto);
Py_VISIT(info->argtypes);
Py_VISIT(info->converters);
Py_VISIT(info->restype);
Py_VISIT(info->checker);
Py_VISIT(info->module);
}
StgInfo *info = _PyStgInfo_FromType_NoState(self);
if (!info) {
PyErr_WriteUnraisable(self);
}
if (info) {
Py_VISIT(info->proto);
Py_VISIT(info->argtypes);
Py_VISIT(info->converters);
Py_VISIT(info->restype);
Py_VISIT(info->checker);
Py_VISIT(info->module);
}
Py_VISIT(Py_TYPE(self));
return PyType_Type.tp_traverse(self, visit, arg);
Expand All @@ -488,38 +485,33 @@ ctype_clear_stginfo(StgInfo *info)
static int
CType_Type_clear(PyObject *self)
{
ctypes_state *st = get_module_state_by_def_final(Py_TYPE(self));
if (st && st->PyCType_Type) {
StgInfo *info;
if (PyStgInfo_FromType(st, self, &info) < 0) {
PyErr_WriteUnraisable(self);
}
if (info) {
ctype_clear_stginfo(info);
}
StgInfo *info = _PyStgInfo_FromType_NoState(self);
if (!info) {
PyErr_WriteUnraisable(self);
}
if (info) {
ctype_clear_stginfo(info);
}
return PyType_Type.tp_clear(self);
}

static void
CType_Type_dealloc(PyObject *self)
{
ctypes_state *st = get_module_state_by_def_final(Py_TYPE(self));
if (st && st->PyCType_Type) {
StgInfo *info;
if (PyStgInfo_FromType(st, self, &info) < 0) {
PyErr_WriteUnraisable(self);
}
if (info) {
PyMem_Free(info->ffi_type_pointer.elements);
info->ffi_type_pointer.elements = NULL;
PyMem_Free(info->format);
info->format = NULL;
PyMem_Free(info->shape);
info->shape = NULL;
ctype_clear_stginfo(info);
}
StgInfo *info = _PyStgInfo_FromType_NoState(self);
if (!info) {
PyErr_WriteUnraisable(self);
}
if (info) {
PyMem_Free(info->ffi_type_pointer.elements);
info->ffi_type_pointer.elements = NULL;
PyMem_Free(info->format);
info->format = NULL;
PyMem_Free(info->shape);
info->shape = NULL;
ctype_clear_stginfo(info);
}

PyTypeObject *tp = Py_TYPE(self);
PyType_Type.tp_dealloc(self);
Py_DECREF(tp);
Expand Down
13 changes: 13 additions & 0 deletions Modules/_ctypes/ctypes.h
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Original file line number Diff line number Diff line change
Expand Up @@ -508,6 +508,19 @@ PyStgInfo_FromAny(ctypes_state *state, PyObject *obj, StgInfo **result)
return _stginfo_from_type(state, Py_TYPE(obj), result);
}

/* A variant of PyStgInfo_FromType that doesn't need the state,
* so it can be called from finalization functions when the module
* state is torn down. Does no checks; cannot fail.
* This inlines the current implementation PyObject_GetTypeData,
* so it might break in the future.
*/
static inline StgInfo *
_PyStgInfo_FromType_NoState(PyObject *type)
{
assert(PyType_Type.tp_basicsize % ALIGNOF_MAX_ALIGN_T == 0);
return (StgInfo *)((char *)type + PyType_Type.tp_basicsize);
}

// Initialize StgInfo on a newly created type
static inline StgInfo *
PyStgInfo_Init(ctypes_state *state, PyTypeObject *type)
Expand Down
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