Introduce _Py_stackref_get_borrowed_from

Author: efimov-mikhail

Include/internal/pycore_stackref.h

@@ -63,6 +63,7 @@ PyAPI_FUNC(PyObject *) _Py_stackref_get_object(_PyStackRef ref);
 PyAPI_FUNC(PyObject *) _Py_stackref_close(_PyStackRef ref, const char *filename, int linenumber);
 PyAPI_FUNC(_PyStackRef) _Py_stackref_create(PyObject *obj, uint16_t flags, const char *filename, int linenumber);
 PyAPI_FUNC(void) _Py_stackref_record_borrow(_PyStackRef ref, const char *filename, int linenumber);
+PyAPI_FUNC(void) _Py_stackref_get_borrowed_from(_PyStackRef ref, _PyStackRef *p_borrowed_from, const char *filename, int linenumber);
 PyAPI_FUNC(void) _Py_stackref_set_borrowed_from(_PyStackRef ref, _PyStackRef borrowed_from, const char *filename, int linenumber);
 PyAPI_FUNC(void) _Py_stackref_copy_borrowed_from(_PyStackRef ref, _PyStackRef ref_orig, const char *filename, int linenumber);
 extern void _Py_stackref_associate(PyInterpreterState *interp, PyObject *obj, _PyStackRef ref);
@@ -252,7 +253,9 @@ _PyStackRef_DUP(_PyStackRef ref, const char *filename, int linenumber)
     }
     _PyStackRef new_ref = _Py_stackref_create(obj, flags, filename, linenumber);
     if (flags == Py_TAG_REFCNT && !_Py_IsImmortal(obj)) {
-        _Py_stackref_copy_borrowed_from(new_ref, ref, filename, linenumber);
+        _PyStackRef borrowed_from;
+        _Py_stackref_get_borrowed_from(ref, &borrowed_from, filename, linenumber);
+        _Py_stackref_set_borrowed_from(new_ref, borrowed_from, filename, linenumber);
     }
     return new_ref;
 }

Python/stackrefs.c

@@ -111,9 +111,8 @@ _Py_stackref_close(_PyStackRef ref, const char *filename, int linenumber)
                 _Py_FatalErrorFormat(__func__,
                     "Invalid borrowed StackRef with ID %" PRIu64 " at %s:%d\n",
                     borrowed_from.index, filename, linenumber);
-            } else {
-                entry_borrowed->borrows--;
             }
+            entry_borrowed->borrows--;
         }
         if (entry->borrows > 0) {
             _Py_FatalErrorFormat(__func__,
@@ -181,9 +180,32 @@ _Py_stackref_record_borrow(_PyStackRef ref, const char *filename, int linenumber
     entry->linenumber_borrow = linenumber;
 }
 
+void
+_Py_stackref_get_borrowed_from(_PyStackRef ref, _PyStackRef *p_borrowed_from, const char *filename, int linenumber)
+{
+    assert(!PyStackRef_IsError(ref));
+    PyInterpreterState *interp = PyInterpreterState_Get();
+
+    TableEntry *entry = _Py_hashtable_get(interp->open_stackrefs_table, (void *)ref.index);
+    if (entry == NULL) {
+        _Py_FatalErrorFormat(__func__,
+            "Invalid StackRef with ID %" PRIu64 " at %s:%d\n",
+            ref.index, filename, linenumber);
+    }
+
+    if (p_borrowed_from != NULL) {
+        *p_borrowed_from = entry->borrowed_from;
+    }
+}
+
+// This function should be used no more than once per ref.
 void
 _Py_stackref_set_borrowed_from(_PyStackRef ref, _PyStackRef borrowed_from, const char *filename, int linenumber)
 {
+    if (PyStackRef_IsNull(borrowed_from)) {
+        return;
+    }
+
     assert(!PyStackRef_IsError(ref));
     PyInterpreterState *interp = PyInterpreterState_Get();
 
@@ -205,11 +227,6 @@ _Py_stackref_set_borrowed_from(_PyStackRef ref, _PyStackRef borrowed_from, const
     entry_borrowed->borrows++;
 }
 
-void
-_Py_stackref_copy_borrowed_from(_PyStackRef ref, _PyStackRef ref_orig, const char *filename, int linenumber)
-{
-}
-
 void
 _Py_stackref_associate(PyInterpreterState *interp, PyObject *obj, _PyStackRef ref)
 {