diff options
Diffstat (limited to 'Python/errors.c')
| -rw-r--r-- | Python/errors.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/Python/errors.c b/Python/errors.c index 2c020cd..8a2ba8f 100644 --- a/Python/errors.c +++ b/Python/errors.c @@ -148,12 +148,16 @@ _PyErr_SetObject(PyThreadState *tstate, PyObject *exception, PyObject *value) value = fixed_value; } - /* Avoid reference cycles through the context chain. + /* Avoid creating new reference cycles through the + context chain, while taking care not to hang on + pre-existing ones. This is O(chain length) but context chains are usually very short. Sensitive readers may try to inline the call to PyException_GetContext. */ if (exc_value != value) { PyObject *o = exc_value, *context; + PyObject *slow_o = o; /* Floyd's cycle detection algo */ + int slow_update_toggle = 0; while ((context = PyException_GetContext(o))) { Py_DECREF(context); if (context == value) { @@ -161,6 +165,16 @@ _PyErr_SetObject(PyThreadState *tstate, PyObject *exception, PyObject *value) break; } o = context; + if (o == slow_o) { + /* pre-existing cycle - all exceptions on the + path were visited and checked. */ + break; + } + if (slow_update_toggle) { + slow_o = PyException_GetContext(slow_o); + Py_DECREF(slow_o); + } + slow_update_toggle = !slow_update_toggle; } PyException_SetContext(value, exc_value); } |