From 483405255628760da9af73fc07d47e1f920f9c0c Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Thu, 23 Mar 2017 22:33:41 +0900
Subject: [PATCH] bugfix: string-copy issue

---
 lib/string.c            | 10 ++++------
 t/issue/string-copy.scm |  8 ++++++++
 2 files changed, 12 insertions(+), 6 deletions(-)
 create mode 100644 t/issue/string-copy.scm

diff --git a/lib/string.c b/lib/string.c
index 832d4e3b..9a2ebd50 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -80,22 +80,20 @@ make_rope_lit(pic_state *pic, const char *str, int len)
 static struct rope *
 make_rope_slice(pic_state *pic, struct rope *owner, int i, int j)
 {
-  struct rope *rope;
+  struct rope *rope, *real_owner;
 
   assert(owner->isleaf);
 
-  if (owner->u.leaf.owner != NULL) {
-    owner = owner->u.leaf.owner;
-  }
+  real_owner = owner->u.leaf.owner == NULL ? owner : owner->u.leaf.owner;
 
   rope = pic_malloc(pic, offsetof(struct rope, buf));
   rope->refcnt = 1;
   rope->weight = j - i;
   rope->isleaf = true;
-  rope->u.leaf.owner = owner;
+  rope->u.leaf.owner = real_owner;
   rope->u.leaf.str = owner->u.leaf.str + i;
 
-  pic_rope_incref(owner);
+  pic_rope_incref(real_owner);
 
   return rope;
 }
diff --git a/t/issue/string-copy.scm b/t/issue/string-copy.scm
new file mode 100644
index 00000000..2e22c0ee
--- /dev/null
+++ b/t/issue/string-copy.scm
@@ -0,0 +1,8 @@
+(import (scheme base)
+        (picrin test))
+
+(test-begin)
+
+(test "456" (string-copy (string-copy "1234567" 3) 0 3))
+
+(test-end)