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gh-105268: Add _Py_FROM_GC() function to pycore_gc.h #105362

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Merged
merged 1 commit into from
Jun 6, 2023
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gh-105268: Add _Py_FROM_GC() function to pycore_gc.h #105362

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23 changes: 17 additions & 6 deletions Include/internal/pycore_gc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,10 +19,21 @@ typedef struct {
uintptr_t _gc_prev;
} PyGC_Head;

#define _PyGC_Head_UNUSED PyGC_Head


/* Get an object's GC head */
static inline PyGC_Head* _Py_AS_GC(PyObject *op) {
return (_Py_CAST(PyGC_Head*, op) - 1);
char *gc = ((char*)op) - sizeof(PyGC_Head);
return (PyGC_Head*)gc;
}
#define _PyGC_Head_UNUSED PyGC_Head

/* Get the object given the GC head */
static inline PyObject* _Py_FROM_GC(PyGC_Head *gc) {
char *op = ((char *)gc) + sizeof(PyGC_Head);
return (PyObject *)op;
}


/* True if the object is currently tracked by the GC. */
static inline int _PyObject_GC_IS_TRACKED(PyObject *op) {
Expand Down Expand Up @@ -57,19 +68,19 @@ static inline int _PyObject_GC_MAY_BE_TRACKED(PyObject *obj) {
// But it is always 0 for normal code.
static inline PyGC_Head* _PyGCHead_NEXT(PyGC_Head *gc) {
uintptr_t next = gc->_gc_next;
return _Py_CAST(PyGC_Head*, next);
return (PyGC_Head*)next;
}
static inline void _PyGCHead_SET_NEXT(PyGC_Head *gc, PyGC_Head *next) {
gc->_gc_next = _Py_CAST(uintptr_t, next);
gc->_gc_next = (uintptr_t)next;
}

// Lowest two bits of _gc_prev is used for _PyGC_PREV_MASK_* flags.
static inline PyGC_Head* _PyGCHead_PREV(PyGC_Head *gc) {
uintptr_t prev = (gc->_gc_prev & _PyGC_PREV_MASK);
return _Py_CAST(PyGC_Head*, prev);
return (PyGC_Head*)prev;
}
static inline void _PyGCHead_SET_PREV(PyGC_Head *gc, PyGC_Head *prev) {
uintptr_t uprev = _Py_CAST(uintptr_t, prev);
uintptr_t uprev = (uintptr_t)prev;
assert((uprev & ~_PyGC_PREV_MASK) == 0);
gc->_gc_prev = ((gc->_gc_prev & ~_PyGC_PREV_MASK) | uprev);
}
Expand Down
6 changes: 3 additions & 3 deletions Include/internal/pycore_object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -326,9 +326,9 @@ _PyObject_GET_WEAKREFS_LISTPTR_FROM_OFFSET(PyObject *op)
static inline int
_PyObject_IS_GC(PyObject *obj)
{
return (PyType_IS_GC(Py_TYPE(obj))
&& (Py_TYPE(obj)->tp_is_gc == NULL
|| Py_TYPE(obj)->tp_is_gc(obj)));
PyTypeObject *type = Py_TYPE(obj);
return (PyType_IS_GC(type)
&& (type->tp_is_gc == NULL || type->tp_is_gc(obj)));
}

// Fast inlined version of PyType_IS_GC()
Expand Down
14 changes: 6 additions & 8 deletions Modules/gcmodule.c
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Expand Up @@ -68,11 +68,9 @@ module gc
// most gc_list_* functions for it.
#define NEXT_MASK_UNREACHABLE (1)

/* Get an object's GC head */
#define AS_GC(o) ((PyGC_Head *)(((char *)(o))-sizeof(PyGC_Head)))
#define AS_GC(op) _Py_AS_GC(op)
#define FROM_GC(gc) _Py_FROM_GC(gc)

/* Get the object given the GC head */
#define FROM_GC(g) ((PyObject *)(((char *)(g))+sizeof(PyGC_Head)))

static inline int
gc_is_collecting(PyGC_Head *g)
Expand Down Expand Up @@ -861,7 +859,7 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
* to imagine how calling it later could create a problem for us. wr
* is moved to wrcb_to_call in this case.
*/
if (gc_is_collecting(AS_GC(wr))) {
if (gc_is_collecting(AS_GC((PyObject *)wr))) {
/* it should already have been cleared above */
assert(wr->wr_object == Py_None);
continue;
Expand All @@ -873,7 +871,7 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
Py_INCREF(wr);

/* Move wr to wrcb_to_call, for the next pass. */
wrasgc = AS_GC(wr);
wrasgc = AS_GC((PyObject *)wr);
assert(wrasgc != next); /* wrasgc is reachable, but
next isn't, so they can't
be the same */
Expand Down Expand Up @@ -1909,7 +1907,7 @@ static PyObject *
gc_is_finalized(PyObject *module, PyObject *obj)
/*[clinic end generated code: output=e1516ac119a918ed input=201d0c58f69ae390]*/
{
if (_PyObject_IS_GC(obj) && _PyGCHead_FINALIZED(AS_GC(obj))) {
if (_PyObject_IS_GC(obj) && _PyGC_FINALIZED(obj)) {
Py_RETURN_TRUE;
}
Py_RETURN_FALSE;
Expand Down Expand Up @@ -2409,7 +2407,7 @@ PyObject_GC_IsTracked(PyObject* obj)
int
PyObject_GC_IsFinalized(PyObject *obj)
{
if (_PyObject_IS_GC(obj) && _PyGCHead_FINALIZED(AS_GC(obj))) {
if (_PyObject_IS_GC(obj) && _PyGC_FINALIZED(obj)) {
return 1;
}
return 0;
Expand Down