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bpo-38070: Enhance visit_decref() debug trace (GH-16631) 

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 "<object at xxx is
freed>" with no other detail.
This commit is contained in:
Victor Stinner 2019-10-08 02:37:38 +02:00 committed by GitHub
parent 36e33c360e
commit 4d5f94b8cd
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 5 additions and 4 deletions
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9
Modules/gcmodule.c
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@ -373,9 +373,9 @@ update_refs(PyGC_Head *containers)
/* A traversal callback for subtract_refs. */ /* A traversal callback for subtract_refs. */
static int 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)) { if (PyObject_IS_GC(op)) {
PyGC_Head *gc = AS_GC(op); PyGC_Head *gc = AS_GC(op);
@ -401,10 +401,11 @@ subtract_refs(PyGC_Head *containers)
traverseproc traverse; traverseproc traverse;
PyGC_Head *gc = GC_NEXT(containers); PyGC_Head *gc = GC_NEXT(containers);
for (; gc != containers; gc = GC_NEXT(gc)) { 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), (void) traverse(FROM_GC(gc),
(visitproc)visit_decref, (visitproc)visit_decref,
NULL); op);
} }
} }