[gc] Gix order-of-destruction bug discovered by Chandon++. The check …

…for aliveness of the scheduler in Parrot_cx_delete_taskwas failing, so in Scheduler.destroy I null out the ->scheduler field of the interpreter to ensure it gets around the segfault here. I don't think gc finalization adds PMCs back onto the free list, so the test there was failing

git-svn-id: https://svn.parrot.org/parrot/trunk@47560 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

src/pmc/scheduler.pmc

@@ -251,6 +251,7 @@ Frees the scheduler's underlying struct.
 */
     VTABLE void destroy() {
         Parrot_Scheduler_attributes * const core_struct = PARROT_SCHEDULER(SELF);
+        core_struct->interp->scheduler = NULL;
         /* TT #946: this line is causing an order-of-destruction error
            because the scheduler is being freed before its tasks.
            Commenting this out till we get a real fix (although it's a hack) */

src/scheduler.c

@@ -403,7 +403,7 @@ void
 Parrot_cx_delete_task(PARROT_INTERP, ARGIN(PMC *task))
 {
     ASSERT_ARGS(Parrot_cx_delete_task)
-    if (interp->scheduler && !PObj_on_free_list_TEST(interp->scheduler)) {
+    if (interp->scheduler) {
         const INTVAL tid = VTABLE_get_integer(interp, task);
         VTABLE_delete_keyed_int(interp, interp->scheduler, tid);
     }