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, 4 insertions, 6 deletions

diff --git a/src/kernel.c b/src/kernel.c
index 9fcee2413..4e95ab24b 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -1151,8 +1151,8 @@ static mrb_value
 mrb_local_variables(mrb_state *mrb, mrb_value self)
 {
   struct RProc *proc;
+  mrb_irep *irep;
   mrb_value vars;
-  struct mrb_irep *irep;
   size_t i;
 
   proc = mrb->c->ci[-1].proc;
@@ -1161,18 +1161,16 @@ mrb_local_variables(mrb_state *mrb, mrb_value self)
     return mrb_ary_new(mrb);
   }
   vars = mrb_hash_new(mrb);
-  while (proc) {
-    if (MRB_PROC_CFUNC_P(proc)) break;
-    irep = proc->body.irep;
+  irep = proc->body.irep;
+  while (irep) {
     if (!irep->lv) break;
     for (i = 0; i + 1 < irep->nlocals; ++i) {
       if (irep->lv[i].name) {
         mrb_hash_set(mrb, vars, mrb_symbol_value(irep->lv[i].name), mrb_true_value());
       }
     }
-    if (MRB_PROC_CLASS_P(proc)) break;
     if (!proc->env) break;
-    proc = proc->body.irep->outer;
+    irep = irep->outer;
   }
 
   return mrb_hash_keys(mrb, vars);