Move exc state to generator. Fixes bpo-25612 (#1773)

Move exception state information from frame objects to coroutine (generator/thread) object where it belongs.

2 files changed, 36 insertions, 23 deletions

diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 8739596..6ab3a22 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -379,8 +379,7 @@ static PyGetSetDef frame_getsetlist[] = {
 
      * ob_type, ob_size, f_code, f_valuestack;
 
-     * f_locals, f_trace,
-       f_exc_type, f_exc_value, f_exc_traceback are NULL;
+     * f_locals, f_trace are NULL;
 
      * f_localsplus does not require re-allocation and
        the local variables in f_localsplus are NULL.
@@ -438,9 +437,6 @@ frame_dealloc(PyFrameObject *f)
     Py_DECREF(f->f_globals);
     Py_CLEAR(f->f_locals);
     Py_CLEAR(f->f_trace);
-    Py_CLEAR(f->f_exc_type);
-    Py_CLEAR(f->f_exc_value);
-    Py_CLEAR(f->f_exc_traceback);
 
     co = f->f_code;
     if (co->co_zombieframe == NULL)
@@ -469,9 +465,6 @@ frame_traverse(PyFrameObject *f, visitproc visit, void *arg)
     Py_VISIT(f->f_globals);
     Py_VISIT(f->f_locals);
     Py_VISIT(f->f_trace);
-    Py_VISIT(f->f_exc_type);
-    Py_VISIT(f->f_exc_value);
-    Py_VISIT(f->f_exc_traceback);
 
     /* locals */
     slots = f->f_code->co_nlocals + PyTuple_GET_SIZE(f->f_code->co_cellvars) + PyTuple_GET_SIZE(f->f_code->co_freevars);
@@ -502,9 +495,6 @@ frame_tp_clear(PyFrameObject *f)
     f->f_stacktop = NULL;
     f->f_executing = 0;
 
-    Py_CLEAR(f->f_exc_type);
-    Py_CLEAR(f->f_exc_value);
-    Py_CLEAR(f->f_exc_traceback);
     Py_CLEAR(f->f_trace);
 
     /* locals */
@@ -698,7 +688,6 @@ _PyFrame_New_NoTrack(PyThreadState *tstate, PyCodeObject *code,
             f->f_localsplus[i] = NULL;
         f->f_locals = NULL;
         f->f_trace = NULL;
-        f->f_exc_type = f->f_exc_value = f->f_exc_traceback = NULL;
     }
     f->f_stacktop = f->f_valuestack;
     f->f_builtins = builtins;
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 5d5798c..7793a54 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -16,6 +16,15 @@ static char *NON_INIT_CORO_MSG = "can't send non-None value to a "
 static char *ASYNC_GEN_IGNORED_EXIT_MSG =
                                  "async generator ignored GeneratorExit";
 
+static inline int
+exc_state_traverse(_PyErr_StackItem *exc_state, visitproc visit, void *arg)
+{
+    Py_VISIT(exc_state->exc_type);
+    Py_VISIT(exc_state->exc_value);
+    Py_VISIT(exc_state->exc_traceback);
+    return 0;
+}
+
 static int
 gen_traverse(PyGenObject *gen, visitproc visit, void *arg)
 {
@@ -23,7 +32,7 @@ gen_traverse(PyGenObject *gen, visitproc visit, void *arg)
     Py_VISIT(gen->gi_code);
     Py_VISIT(gen->gi_name);
     Py_VISIT(gen->gi_qualname);
-    return 0;
+    return exc_state_traverse(&gen->gi_exc_state, visit, arg);
 }
 
 void
@@ -87,6 +96,21 @@ _PyGen_Finalize(PyObject *self)
     PyErr_Restore(error_type, error_value, error_traceback);
 }
 
+static inline void
+exc_state_clear(_PyErr_StackItem *exc_state)
+{
+    PyObject *t, *v, *tb;
+    t = exc_state->exc_type;
+    v = exc_state->exc_value;
+    tb = exc_state->exc_traceback;
+    exc_state->exc_type = NULL;
+    exc_state->exc_value = NULL;
+    exc_state->exc_traceback = NULL;
+    Py_XDECREF(t);
+    Py_XDECREF(v);
+    Py_XDECREF(tb);
+}
+
 static void
 gen_dealloc(PyGenObject *gen)
 {
@@ -116,6 +140,7 @@ gen_dealloc(PyGenObject *gen)
     Py_CLEAR(gen->gi_code);
     Py_CLEAR(gen->gi_name);
     Py_CLEAR(gen->gi_qualname);
+    exc_state_clear(&gen->gi_exc_state);
     PyObject_GC_Del(gen);
 }
 
@@ -187,7 +212,11 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
     f->f_back = tstate->frame;
 
     gen->gi_running = 1;
+    gen->gi_exc_state.previous_item = tstate->exc_info;
+    tstate->exc_info = &gen->gi_exc_state;
     result = PyEval_EvalFrameEx(f, exc);
+    tstate->exc_info = gen->gi_exc_state.previous_item;
+    gen->gi_exc_state.previous_item = NULL;
     gen->gi_running = 0;
 
     /* Don't keep the reference to f_back any longer than necessary.  It
@@ -281,16 +310,7 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
     if (!result || f->f_stacktop == NULL) {
         /* generator can't be rerun, so release the frame */
         /* first clean reference cycle through stored exception traceback */
-        PyObject *t, *v, *tb;
-        t = f->f_exc_type;
-        v = f->f_exc_value;
-        tb = f->f_exc_traceback;
-        f->f_exc_type = NULL;
-        f->f_exc_value = NULL;
-        f->f_exc_traceback = NULL;
-        Py_XDECREF(t);
-        Py_XDECREF(v);
-        Py_XDECREF(tb);
+        exc_state_clear(&gen->gi_exc_state);
         gen->gi_frame->f_gen = NULL;
         gen->gi_frame = NULL;
         Py_DECREF(f);
@@ -810,6 +830,10 @@ gen_new_with_qualname(PyTypeObject *type, PyFrameObject *f,
     gen->gi_code = (PyObject *)(f->f_code);
     gen->gi_running = 0;
     gen->gi_weakreflist = NULL;
+    gen->gi_exc_state.exc_type = NULL;
+    gen->gi_exc_state.exc_value = NULL;
+    gen->gi_exc_state.exc_traceback = NULL;
+    gen->gi_exc_state.previous_item = NULL;
     if (name != NULL)
         gen->gi_name = name;
     else