From 8af71327eab81855eab2935a8b74830deb82bc46 Mon Sep 17 00:00:00 2001 From: Victor Stinner Date: Tue, 8 Oct 2019 01:50:11 +0200 Subject: [PATCH] bpo-38070: Enhance visit_decref() debug trace subtract_refs() now pass the parent object to visit_decref() which pass it to _PyObject_ASSERT(). So if the "is freed" assertion fails, the parent is used in debug trace, rather than the freed object. The parent object is more likely to contain useful information. Freed objects cannot be inspected are are displayed as "" with no other detail. --- Modules/gcmodule.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c index 2cbf573cf46eca..2b47abae1ae4d0 100644 --- a/Modules/gcmodule.c +++ b/Modules/gcmodule.c @@ -373,9 +373,9 @@ update_refs(PyGC_Head *containers) /* A traversal callback for subtract_refs. */ static int -visit_decref(PyObject *op, void *data) +visit_decref(PyObject *op, void *parent) { - _PyObject_ASSERT(op, !_PyObject_IsFreed(op)); + _PyObject_ASSERT(_PyObject_CAST(parent), !_PyObject_IsFreed(op)); if (PyObject_IS_GC(op)) { PyGC_Head *gc = AS_GC(op); @@ -401,10 +401,11 @@ subtract_refs(PyGC_Head *containers) traverseproc traverse; PyGC_Head *gc = GC_NEXT(containers); for (; gc != containers; gc = GC_NEXT(gc)) { - traverse = Py_TYPE(FROM_GC(gc))->tp_traverse; + PyObject *op = FROM_GC(gc); + traverse = Py_TYPE(op)->tp_traverse; (void) traverse(FROM_GC(gc), (visitproc)visit_decref, - NULL); + op); } }