Address #876 Don't allow scheduling a fiber once it has been canceled already.

We were effectively cancelling the cancellation.

src/core/ev.c

@@ -464,7 +464,9 @@ const JanetAbstractType janet_stream_type = {
 
 /* Register a fiber to resume with value */
 void janet_schedule_signal(JanetFiber *fiber, Janet value, JanetSignal sig) {
+    if (fiber->flags & JANET_FIBER_FLAG_CANCELED) return;
     JanetTask t = { fiber, value, sig, ++fiber->sched_id };
+    if (sig == JANET_SIGNAL_ERROR) fiber->flags |= JANET_FIBER_FLAG_CANCELED;
     janet_q_push(&janet_vm.spawn, &t, sizeof(t));
 }
 
@@ -1226,6 +1228,7 @@ JanetFiber *janet_loop1(void) {
     while (janet_vm.spawn.head != janet_vm.spawn.tail) {
         JanetTask task = {NULL, janet_wrap_nil(), JANET_SIGNAL_OK, 0};
         janet_q_pop(&janet_vm.spawn, &task, sizeof(task));
+        task.fiber->flags &= ~JANET_FIBER_FLAG_CANCELED;
         if (task.expected_sched_id != task.fiber->sched_id) continue;
         Janet res;
         JanetSignal sig = janet_continue_signal(task.fiber, task.value, &res, task.sig);

src/core/fiber.h

@@ -48,6 +48,7 @@
 
 #define JANET_FIBER_STATUS_MASK 0x3F0000
 #define JANET_FIBER_RESUME_SIGNAL 0x400000
+#define JANET_FIBER_FLAG_CANCELED 0x400000
 #define JANET_FIBER_STATUS_OFFSET 16
 
 #define JANET_FIBER_BREAKPOINT       0x1000000

src/core/os.c

@@ -689,12 +689,12 @@ static int janet_proc_get(void *p, Janet key, Janet *out) {
         *out = (NULL == proc->err) ? janet_wrap_nil() : janet_wrap_abstract(proc->err);
         return 1;
     }
-    #ifndef JANET_WINDOWS
+#ifndef JANET_WINDOWS
     if (janet_keyeq(key, "pid")) {
         *out = janet_wrap_number(proc->pid);
         return 1;
     }
-    #endif
+#endif
     if ((-1 != proc->return_code) && janet_keyeq(key, "return-code")) {
         *out = janet_wrap_integer(proc->return_code);
         return 1;

src/mainclient/shell.c

@@ -759,7 +759,7 @@ static int line() {
             case 3:     /* ctrl-c */
                 norawmode();
                 kill(getpid(), SIGINT);
-                /* fallthrough */
+            /* fallthrough */
             case 17:    /* ctrl-q */
                 gbl_cancel_current_repl_form = 1;
                 clearlines();