Stackless issue #200: fix PyTasklet_Run_nr() and PyTasklet_Switch_nr()

Fix a bug in the C-API functions PyTasklet_Run_nr() and
PyTasklet_Switch_nr(). Under exotic conditions the functions could
cause undefined behavior.

Author: Anselm Kruis

Stackless/changelog.txt

@@ -9,6 +9,11 @@ What's New in Stackless 3.X.X?
 
 *Release date: 20XX-XX-XX*
 
+- https://github.com/stackless-dev/stackless/issues/200
+  Fix a bug in the C-API functions PyTasklet_Run_nr() and
+  PyTasklet_Switch_nr(). Under exotic conditions the functions could
+  cause undefined behavior.
+
 - https://github.com/stackless-dev/stackless/issues/196
   Stackless can now pickle coroutine_wrapper objects.
 

Stackless/module/taskletobject.c

@@ -936,7 +936,8 @@ impl_tasklet_run_remove(PyTaskletObject *task, int remove);
 int
 PyTasklet_Run_nr(PyTaskletObject *task)
 {
-    (_PyRuntime.st.try_stackless) = 1;
+    PyThreadState *ts = PyThreadState_GET();
+    STACKLESS_PROPOSE_ALL(ts);
     return slp_return_wrapper(impl_tasklet_run_remove(task, 0));
 }
 
@@ -1061,7 +1062,8 @@ PyTasklet_Switch_M(PyTaskletObject *task)
 int
 PyTasklet_Switch_nr(PyTaskletObject *task)
 {
-    (_PyRuntime.st.try_stackless) = 1;
+    PyThreadState *ts = PyThreadState_GET();
+    STACKLESS_PROPOSE_ALL(ts);
     return slp_return_wrapper(impl_tasklet_run_remove(task, 1));
 }