bpo-35081: Add Include/internal/pycore_object.h (GH-10640)

Move _PyObject_GC_TRACK() and _PyObject_GC_UNTRACK() from
Include/objimpl.h to Include/internal/pycore_object.h.

1 files changed, 56 insertions, 0 deletions

diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
new file mode 100644
index 0000000..a263834
--- /dev/null
+++ b/Include/internal/pycore_object.h
@@ -0,0 +1,56 @@
+#ifndef Py_INTERNAL_OBJECT_H
+#define Py_INTERNAL_OBJECT_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if !defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_BUILTIN)
+#  error "this header requires Py_BUILD_CORE or Py_BUILD_CORE_BUILTIN defined"
+#endif
+
+/* Tell the GC to track this object.
+ *
+ * NB: While the object is tracked by the collector, it must be safe to call the
+ * ob_traverse method.
+ *
+ * Internal note: _PyRuntime.gc.generation0->_gc_prev doesn't have any bit flags
+ * because it's not object header.  So we don't use _PyGCHead_PREV() and
+ * _PyGCHead_SET_PREV() for it to avoid unnecessary bitwise operations.
+ *
+ * The PyObject_GC_Track() function is the public version of this macro.
+ */
+#define _PyObject_GC_TRACK(o) do { \
+        PyGC_Head *g = _Py_AS_GC(o); \
+        if (g->_gc_next != 0) { \
+            Py_FatalError("GC object already tracked"); \
+        } \
+        assert((g->_gc_prev & _PyGC_PREV_MASK_COLLECTING) == 0); \
+        PyGC_Head *last = (PyGC_Head*)(_PyRuntime.gc.generation0->_gc_prev); \
+        _PyGCHead_SET_NEXT(last, g); \
+        _PyGCHead_SET_PREV(g, last); \
+        _PyGCHead_SET_NEXT(g, _PyRuntime.gc.generation0); \
+        _PyRuntime.gc.generation0->_gc_prev = (uintptr_t)g; \
+    } while (0);
+
+/* Tell the GC to stop tracking this object.
+ *
+ * Internal note: This may be called while GC.  So _PyGC_PREV_MASK_COLLECTING must
+ * be cleared.  But _PyGC_PREV_MASK_FINALIZED bit is kept.
+ *
+ * The PyObject_GC_UnTrack() function is the public version of this macro.
+ */
+#define _PyObject_GC_UNTRACK(o) do { \
+        PyGC_Head *g = _Py_AS_GC(o); \
+        PyGC_Head *prev = _PyGCHead_PREV(g); \
+        PyGC_Head *next = _PyGCHead_NEXT(g); \
+        assert(next != NULL); \
+        _PyGCHead_SET_NEXT(prev, next); \
+        _PyGCHead_SET_PREV(next, prev); \
+        g->_gc_next = 0; \
+        g->_gc_prev &= _PyGC_PREV_MASK_FINALIZED; \
+    } while (0);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_OBJECT_H */