gh-108634: Py_TRACE_REFS uses a hash table (#108663)

Python built with "configure --with-trace-refs" (tracing references)
is now ABI compatible with Python release build and debug build.
Moreover, it now also supports the Limited API.

Change Py_TRACE_REFS build:

* Remove _PyObject_EXTRA_INIT macro.
* The PyObject structure no longer has two extra members (_ob_prev
  and _ob_next).
* Use a hash table (_Py_hashtable_t) to trace references (all
  objects): PyInterpreterState.object_state.refchain.
* Py_TRACE_REFS build is now ABI compatible with release build and
  debug build.
* Limited C API extensions can now be built with Py_TRACE_REFS:
  xxlimited, xxlimited_35, _testclinic_limited.
* No longer rename PyModule_Create2() and PyModule_FromDefAndSpec2()
  functions to PyModule_Create2TraceRefs() and
  PyModule_FromDefAndSpec2TraceRefs().
* _Py_PrintReferenceAddresses() is now called before
  finalize_interp_delete() which deletes the refchain hash table.
* test_tracemalloc find_trace() now also filters by size to ignore
  the memory allocated by _PyRefchain_Trace().

Test changes for Py_TRACE_REFS:

* Add test.support.Py_TRACE_REFS constant.
* Add test_sys.test_getobjects() to test sys.getobjects() function.
* test_exceptions skips test_recursion_normalizing_with_no_memory()
  and test_memory_error_in_PyErr_PrintEx() if Python is built with
  Py_TRACE_REFS.
* test_repl skips test_no_memory().
* test_capi skisp test_set_nomemory().

1 files changed, 3 insertions, 2 deletions

diff --git a/Objects/structseq.c b/Objects/structseq.c
index 6c07e63..0ca622e 100644
--- a/Objects/structseq.c
+++ b/Objects/structseq.c
@@ -573,9 +573,10 @@ PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)
     Py_ssize_t n_members, n_unnamed_members;
 
 #ifdef Py_TRACE_REFS
-    /* if the type object was chained, unchain it first
+    /* if the type object was traced, remove it first
        before overwriting its storage */
-    if (type->ob_base.ob_base._ob_next) {
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    if (_PyRefchain_IsTraced(interp, (PyObject *)type)) {
         _Py_ForgetReference((PyObject *)type);
     }
 #endif