bpo-39947: Remove old private trashcan C API functions (GH-26869)

Remove 4 C API private trashcan functions which were only kept for
the backward compatibility of the stable ABI with Python 3.8 and
older, since the trashcan API was not usable with the limited C API
on Python 3.8 and older. The trashcan API was excluded from the
limited C API in Python 3.9.

Removed functions:

* _PyTrash_deposit_object()
* _PyTrash_destroy_chain()
* _PyTrash_thread_deposit_object()
* _PyTrash_thread_destroy_chain()

The trashcan C API was never usable with the limited C API, since old
trashcan macros accessed directly PyThreadState members like
"_tstate->trash_delete_nesting", whereas the PyThreadState structure
is opaque in the limited C API.

Exclude also the PyTrash_UNWIND_LEVEL constant from the C API.

The trashcan C API was modified in Python 3.9 by commit
38965ec5411da60d312b59be281f3510d58e0cf1 and in Python 3.10 by commit
ed1a5a5baca8f61e9a99c5be3adc16b1801514fe to hide implementation
details.

1 files changed, 8 insertions, 48 deletions

diff --git a/Objects/object.c b/Objects/object.c
index 854cc85..c87a83f 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -2092,25 +2092,13 @@ finally:
 
 /* Trashcan support. */
 
-/* Add op to the _PyTrash_delete_later list.  Called when the current
+#define _PyTrash_UNWIND_LEVEL 50
+
+/* Add op to the gcstate->trash_delete_later list.  Called when the current
  * call-stack depth gets large.  op must be a currently untracked gc'ed
  * object, with refcount 0.  Py_DECREF must already have been called on it.
  */
-void
-_PyTrash_deposit_object(PyObject *op)
-{
-    PyInterpreterState *interp = _PyInterpreterState_GET();
-    struct _gc_runtime_state *gcstate = &interp->gc;
-
-    _PyObject_ASSERT(op, _PyObject_IS_GC(op));
-    _PyObject_ASSERT(op, !_PyObject_GC_IS_TRACKED(op));
-    _PyObject_ASSERT(op, Py_REFCNT(op) == 0);
-    _PyGCHead_SET_PREV(_Py_AS_GC(op), gcstate->trash_delete_later);
-    gcstate->trash_delete_later = op;
-}
-
-/* The equivalent API, using per-thread state recursion info */
-void
+static void
 _PyTrash_thread_deposit_object(PyObject *op)
 {
     PyThreadState *tstate = _PyThreadState_GET();
@@ -2121,37 +2109,9 @@ _PyTrash_thread_deposit_object(PyObject *op)
     tstate->trash_delete_later = op;
 }
 
-/* Deallocate all the objects in the _PyTrash_delete_later list.  Called when
- * the call-stack unwinds again.
- */
-void
-_PyTrash_destroy_chain(void)
-{
-    PyInterpreterState *interp = _PyInterpreterState_GET();
-    struct _gc_runtime_state *gcstate = &interp->gc;
-
-    while (gcstate->trash_delete_later) {
-        PyObject *op = gcstate->trash_delete_later;
-        destructor dealloc = Py_TYPE(op)->tp_dealloc;
-
-        gcstate->trash_delete_later =
-            (PyObject*) _PyGCHead_PREV(_Py_AS_GC(op));
-
-        /* Call the deallocator directly.  This used to try to
-         * fool Py_DECREF into calling it indirectly, but
-         * Py_DECREF was already called on this object, and in
-         * assorted non-release builds calling Py_DECREF again ends
-         * up distorting allocation statistics.
-         */
-        _PyObject_ASSERT(op, Py_REFCNT(op) == 0);
-        ++gcstate->trash_delete_nesting;
-        (*dealloc)(op);
-        --gcstate->trash_delete_nesting;
-    }
-}
-
-/* The equivalent API, using per-thread state recursion info */
-void
+/* Deallocate all the objects in the gcstate->trash_delete_later list.
+ * Called when the call-stack unwinds again. */
+static void
 _PyTrash_thread_destroy_chain(void)
 {
     PyThreadState *tstate = _PyThreadState_GET();
@@ -2192,7 +2152,7 @@ _PyTrash_thread_destroy_chain(void)
 int
 _PyTrash_begin(PyThreadState *tstate, PyObject *op)
 {
-    if (tstate->trash_delete_nesting >= PyTrash_UNWIND_LEVEL) {
+    if (tstate->trash_delete_nesting >= _PyTrash_UNWIND_LEVEL) {
         /* Store the object (to be deallocated later) and jump past
          * Py_TRASHCAN_END, skipping the body of the deallocator */
         _PyTrash_thread_deposit_object(op);