Shared TT_ENV may need to be marked; fix #3550

src/gc.c

@@ -646,7 +646,6 @@ gc_mark_children(mrb_state *mrb, mrb_gc *gc, struct RBasic *obj)
       struct REnv *e = (struct REnv*)obj;
       mrb_int i, len;
 
-      if MRB_ENV_STACK_SHARED_P(e) break;
       len = MRB_ENV_STACK_LEN(e);
       for (i=0; i<len; i++) {
         mrb_gc_mark_value(mrb, e->stack[i]);
@@ -761,6 +760,7 @@ obj_free(mrb_state *mrb, struct RBasic *obj, int end)
   case MRB_TT_FIBER:
     {
       struct mrb_context *c = ((struct RFiber*)obj)->cxt;
+
       if (!end && c && c != mrb->root_c) {
         mrb_callinfo *ci = c->ci;
         mrb_callinfo *ce = c->cibase;