diff options
Diffstat (limited to 'Python/gc.c')
| -rw-r--r-- | Python/gc.c | 27 |
1 files changed, 23 insertions, 4 deletions
diff --git a/Python/gc.c b/Python/gc.c index 7b0e6d6e803..88849a43680 100644 --- a/Python/gc.c +++ b/Python/gc.c @@ -1,6 +1,6 @@ // This implements the reference cycle garbage collector. // The Python module interface to the collector is in gcmodule.c. -// See https://devguide.python.org/internals/garbage-collector/ +// See InternalDocs/garbage_collector.md for more infromation. #include "Python.h" #include "pycore_ceval.h" // _Py_set_eval_breaker_bit() @@ -870,7 +870,7 @@ move_legacy_finalizer_reachable(PyGC_Head *finalizers) * no object in `unreachable` is weakly referenced anymore. */ static int -handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old) +handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old, bool allow_callbacks) { PyGC_Head *gc; PyObject *op; /* generally FROM_GC(gc) */ @@ -879,7 +879,9 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old) PyGC_Head *next; int num_freed = 0; - gc_list_init(&wrcb_to_call); + if (allow_callbacks) { + gc_list_init(&wrcb_to_call); + } /* Clear all weakrefs to the objects in unreachable. If such a weakref * also has a callback, move it into `wrcb_to_call` if the callback @@ -935,6 +937,11 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old) _PyObject_ASSERT((PyObject *)wr, wr->wr_object == op); _PyWeakref_ClearRef(wr); _PyObject_ASSERT((PyObject *)wr, wr->wr_object == Py_None); + + if (!allow_callbacks) { + continue; + } + if (wr->wr_callback == NULL) { /* no callback */ continue; @@ -987,6 +994,10 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old) } } + if (!allow_callbacks) { + return 0; + } + /* Invoke the callbacks we decided to honor. It's safe to invoke them * because they can't reference unreachable objects. */ @@ -1737,7 +1748,7 @@ gc_collect_region(PyThreadState *tstate, } /* Clear weakrefs and invoke callbacks as necessary. */ - stats->collected += handle_weakrefs(&unreachable, to); + stats->collected += handle_weakrefs(&unreachable, to, true); gc_list_validate_space(to, gcstate->visited_space); validate_list(to, collecting_clear_unreachable_clear); validate_list(&unreachable, collecting_set_unreachable_clear); @@ -1751,6 +1762,14 @@ gc_collect_region(PyThreadState *tstate, gc_list_init(&final_unreachable); handle_resurrected_objects(&unreachable, &final_unreachable, to); + /* Clear weakrefs to objects in the unreachable set. No Python-level + * code must be allowed to access those unreachable objects. During + * delete_garbage(), finalizers outside the unreachable set might run + * and create new weakrefs. If those weakrefs were not cleared, they + * could reveal unreachable objects. Callbacks are not executed. + */ + handle_weakrefs(&final_unreachable, NULL, false); + /* Call tp_clear on objects in the final_unreachable set. This will cause * the reference cycles to be broken. It may also cause some objects * in finalizers to be freed. |