Stackless issue #149: Move exc state from thread to tasklet

bpo-25612 (python#1773) moves the exception state information from frame
object to coroutine (generator/thread) object where it belongs.
As a consequence Stackless moves the exception state information for
non-current tasklets from thread-state to the tasklet. This changes the
pickle format of frame, tasklet and generator objects.
The commit adds three test cases.

Author: Anselm Kruis

Include/frameobject.h

@@ -52,7 +52,7 @@ typedef struct _frame {
     char f_executing;           /* whether the frame is still executing */
     PyTryBlock f_blockstack[CO_MAXBLOCKS]; /* for try and loop blocks */
 #ifdef STACKLESS
-    PyCodeObject *f_code;	    /* code segment */
+    PyCodeObject *f_code;           /* code segment */
 #endif
     PyObject *f_localsplus[1];  /* locals+stack, dynamically sized */
 } PyFrameObject;

Objects/frameobject.c

@@ -363,14 +363,14 @@ frame_settrace(PyFrameObject *f, PyObject* v, void *closure)
 static PyObject *
 frame_getback(PyFrameObject *f, void *nope)
 {
-	PyFrameObject *fb = f->f_back;
-	PyObject *ret;
+        PyFrameObject *fb = f->f_back;
+        PyObject *ret;
     /* move over cframe objects but halt at NULL or None */
-	while (fb != NULL && (PyObject*)fb != Py_None && !PyFrame_Check(fb))
-		fb = fb->f_back;
-	ret = (PyObject *) fb;
-	if (ret == NULL)
-		ret = Py_None;
+        while (fb != NULL && (PyObject*)fb != Py_None && !PyFrame_Check(fb))
+                fb = fb->f_back;
+        ret = (PyObject *) fb;
+        if (ret == NULL)
+                ret = Py_None;
     Py_INCREF(ret);
     return ret;
 }
@@ -380,7 +380,7 @@ frame_getback(PyFrameObject *f, void *nope)
 
 static PyGetSetDef frame_getsetlist[] = {
 #ifdef STACKLESS
-    {"f_back",	(getter)frame_getback, NULL, NULL},
+    {"f_back",  (getter)frame_getback, NULL, NULL},
 #endif
     {"f_locals",        (getter)frame_getlocals, NULL, NULL},
     {"f_lineno",        (getter)frame_getlineno,

Objects/genobject.c

@@ -274,6 +274,9 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
     f->f_back->f_back = stopframe;
 
     gen->gi_running = 1;
+    assert(gen->gi_exc_state.previous_item == NULL);
+    gen->gi_exc_state.previous_item = tstate->exc_info;
+    tstate->exc_info = &gen->gi_exc_state;
 
     f->f_execute = PyEval_EvalFrameEx_slp;
 
@@ -321,6 +324,10 @@ gen_iternext_callback(PyFrameObject *f, int exc, PyObject *result)
     /* Check, that this cframe belongs to gen */
     assert(f->f_back == (PyFrameObject *)cf);
 
+    assert(gen->gi_exc_state.previous_item != NULL);
+    ts->exc_info = gen->gi_exc_state.previous_item;
+    gen->gi_exc_state.previous_item = NULL;
+    gen->gi_running = 0;
 #endif
     /* If the generator just returned (as opposed to yielding), signal
      * that the generator is exhausted. */
@@ -405,8 +412,6 @@ gen_iternext_callback(PyFrameObject *f, int exc, PyObject *result)
     }
 
 #ifdef STACKLESS
-    gen->gi_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. */

Stackless/changelog.txt

@@ -9,6 +9,13 @@ What's New in Stackless 3.X.X?
 
 *Release date: 20XX-XX-XX*
 
+- https://github.com/stackless-dev/stackless/issues/149
+  C-Python bpo-25612 (#1773) moves the exception state information from frame
+  object to coroutine (generator/thread) object where it belongs. As a
+  consequence Stackless moves the exception state information from thread
+  to tasklet. This changes the pickle format of frame, tasklet and generator
+  objects compared to previous major versions of Stackless.
+
 - https://github.com/stackless-dev/stackless/issues/166
   Fix C-API functions PyEval_EvalFrameEx() and PyEval_EvalFrame().
   They are now compatible with C-Python.

Stackless/core/stackless_impl.h

@@ -402,7 +402,6 @@ PyObject * slp_eval_frame_iter(struct _frame *f,  int throwflag, PyObject *retva
 PyObject * slp_eval_frame_setup_with(struct _frame *f,  int throwflag, PyObject *retval);
 PyObject * slp_eval_frame_with_cleanup(struct _frame *f,  int throwflag, PyObject *retval);
 /* other eval_frame functions from module/scheduling.c */
-PyObject * slp_restore_exception(PyFrameObject *f, int exc, PyObject *retval);
 PyObject * slp_restore_tracing(PyFrameObject *f, int exc, PyObject *retval);
 /* other eval_frame functions from Objects/typeobject.c */
 PyObject * slp_tp_init_callback(PyFrameObject *f, int exc, PyObject *retval);
@@ -748,6 +747,7 @@ PyObject * slp_curexc_to_bomb(void);
 PyObject * slp_nomemory_bomb(void);
 PyObject * slp_bomb_explode(PyObject *bomb);
 int slp_init_bombtype(void);
+PyObject * slp_get_obj_for_exc_state(_PyErr_StackItem *exc_info);
 
 /* handy abbrevations */
 

Stackless/core/stackless_structs.h

@@ -102,10 +102,6 @@ typedef struct _tasklet_tstate {
     Py_tracefunc c_tracefunc;
     PyObject *c_profileobj;
     PyObject *c_traceobj;
-
-    PyObject *exc_type;
-    PyObject *exc_value;
-    PyObject *exc_traceback;
 } PyTaskletTStateStruc;
 
 typedef struct _tasklet {
@@ -117,10 +113,17 @@ typedef struct _tasklet {
         struct _cframe *cframe;
     } f;
     PyObject *tempval;
+    struct _cstack *cstate;
+    /* Pointer to the top of the stack of the exceptions currently
+     * being handled */
+    _PyErr_StackItem *exc_info;
+    /* The exception currently being handled, if no coroutines/generators
+     * are present. Always last element on the stack referred to be exc_info.
+     */
+    _PyErr_StackItem exc_state;
     /* bits stuff */
     struct _tasklet_flags flags;
     int recursion_depth;
-    struct _cstack *cstate;
     PyObject *def_globals;
     PyObject *tsk_weakreflist;
 } PyTaskletObject;