diff options
| -rw-r--r-- | Python/ceval.c | 41 |
1 files changed, 27 insertions, 14 deletions
diff --git a/Python/ceval.c b/Python/ceval.c index ea5c537..a71d48f 100644 --- a/Python/ceval.c +++ b/Python/ceval.c @@ -138,6 +138,7 @@ gen_dealloc(genobject *gen) static PyObject * gen_iternext(genobject *gen) { + PyThreadState *tstate = PyThreadState_GET(); PyFrameObject *f = gen->frame; PyObject *result; @@ -149,15 +150,24 @@ gen_iternext(genobject *gen) if (f->f_stackbottom == NULL) { return NULL; } - gen->running = 1; + + /* Generators always return to their most recent caller, not + * necessarily their creator. */ + Py_INCREF(tstate->frame); + assert(f->f_back == NULL); + f->f_back = tstate->frame; + + gen->running = 1; result = eval_frame(f); - gen->running = 0; - /* The connection between this frame and its parent is over now, so - must NULL out f_back lest it get decref'ed when gen dies (note - that eval_frame sets f->f_back without bumping its refcount: we - never had a fully legit reference to it). */ + gen->running = 0; + + /* Don't keep the reference to f_back any longer than necessary. It + * may keep a chain of frames alive or it could create a reference + * cycle. */ + Py_DECREF(f->f_back); f->f_back = NULL; - return result; + + return result; } static PyObject * @@ -168,12 +178,12 @@ gen_next(genobject *gen, PyObject *args) if (!PyArg_ParseTuple(args, ":next")) return NULL; - result = gen_iternext(gen); + result = gen_iternext(gen); - if (result == NULL && !PyErr_Occurred()) { + if (result == NULL && !PyErr_Occurred()) { PyErr_SetObject(PyExc_StopIteration, Py_None); return NULL; - } + } return result; } @@ -568,9 +578,7 @@ eval_frame(PyFrameObject *f) return NULL; } - f->f_back = tstate->frame; tstate->frame = f; - co = f->f_code; fastlocals = f->f_localsplus; freevars = f->f_localsplus + f->f_nlocals; @@ -2482,8 +2490,13 @@ eval_code2(PyCodeObject *co, PyObject *globals, PyObject *locals, } if (co->co_flags & CO_GENERATOR) { - /* create a new generator that owns the ready to run frame - * and return that as the value */ + /* Don't need to keep the reference to f_back, it will be set + * when the generator is resumed. */ + Py_DECREF(f->f_back); + f->f_back = NULL; + + /* Create a new generator that owns the ready to run frame + * and return that as the value. */ return gen_new(f); } |