From 74feec78f120d3a1e54ded43f6a47a8fd92d72ac Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Mon, 9 Dec 2013 09:32:30 -0800
Subject: [PATCH] always emit the same unique symbol for unbound variable

---
 src/macro.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/macro.c b/src/macro.c
index bdd30643..01b7dd38 100644
--- a/src/macro.c
+++ b/src/macro.c
@@ -240,16 +240,21 @@ macroexpand(pic_state *pic, pic_value expr, struct pic_senv *senv)
   }
   case PIC_TT_SYMBOL: {
     struct xh_entry *e;
-    while (senv) {
+    pic_sym uniq;
+    while (true) {
       if ((e = xh_get(senv->tbl, pic_symbol_name(pic, pic_sym(expr)))) != NULL) {
 	if (e->val >= 0)
 	  return pic_symbol_value((pic_sym)e->val);
 	else
 	  return pic_obj_value(senv->stx[~e->val]);
       }
+      if (! senv->up)
+        break;
       senv = senv->up;
     }
-    return pic_symbol_value(new_uniq_sym(pic, pic_sym(expr)));
+    uniq = new_uniq_sym(pic, pic_sym(expr));
+    xh_put(senv->tbl, pic_symbol_name(pic, pic_sym(expr)), (int)uniq);
+    return pic_symbol_value(uniq);
   }
   case PIC_TT_PAIR: {
     pic_value car, v;