Restructure `irep->outer` chain; fix #3804

Instead of `irep -> proc` chain, we use `irep -> irep` chain to
avoid GC bugs like #3804. We added `target_class` reference to
`mrb_irep` struct. That means one more word consumption per `irep`.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/gc.c b/src/gc.c
index 65727ece9..d602bfb70 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -648,7 +648,7 @@ gc_mark_children(mrb_state *mrb, mrb_gc *gc, struct RBasic *obj)
       mrb_gc_mark(mrb, (struct RBasic*)p->env);
       mrb_gc_mark(mrb, (struct RBasic*)p->target_class);
       if (!MRB_PROC_CFUNC_P(p) && p->body.irep) {
-        mrb_gc_mark(mrb, (struct RBasic*)p->body.irep->outer);
+        mrb_gc_mark(mrb, (struct RBasic*)p->body.irep->target_class);
       }
     }
     break;