>From 2d0a23e8c84bc8b1c5f5dbc9f464866c0677c5ad Mon Sep 17 00:00:00 2001
From: Mario Domenech Goulart <address@hidden>
Date: Wed, 10 Jun 2015 15:03:38 -0300
Subject: [PATCH] data-structures: fix substring-index[-ci] corner case ("" as
 2nd arg)

Fix regression introduced by 25db851b90260:

$ ~/local/chicken-4.9.0.1/bin/csi -p '(substring-index "foo" "")'

$ ~/local/chicken-4.10.0rc1/bin/csi -p '(substring-index "foo" "")'

Error: (substring-index) out of range
0
0

        Call history:

        <syntax>          (substring-index "foo" "")
        <eval>    (substring-index "foo" "")    <--
---
 data-structures.scm             |   22 ++++++++++++----------
 tests/data-structures-tests.scm |    2 ++
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/data-structures.scm b/data-structures.scm
index b67065e..0a457eb 100644
--- a/data-structures.scm
+++ b/data-structures.scm
@@ -311,16 +311,18 @@
 	   (whichlen (##sys#size which))
 	   (end (fx- wherelen whichlen)))
       (##sys#check-exact start loc)
-      (if (and (fx>= start 0)
-	       (fx> wherelen start))
-	  (let loop ((istart start))
-	    (cond ((fx> istart end) #f)
-		  ((test istart whichlen) istart)
-		  (else (loop (fx+ istart 1)))))
-	  (##sys#error-hook (foreign-value "C_OUT_OF_RANGE_ERROR" int)
-			    loc
-			    start
-			    wherelen))))
+      (if (fx= wherelen 0)
+          (and (fx= whichlen 0) 0)
+          (if (and (fx>= start 0)
+                   (fx> wherelen start))
+              (let loop ((istart start))
+                (cond ((fx> istart end) #f)
+                      ((test istart whichlen) istart)
+                      (else (loop (fx+ istart 1)))))
+              (##sys#error-hook (foreign-value "C_OUT_OF_RANGE_ERROR" int)
+                                loc
+                                start
+                                wherelen)))))
 
   (set! ##sys#substring-index 
     (lambda (which where start)
diff --git a/tests/data-structures-tests.scm b/tests/data-structures-tests.scm
index 51c25a9..d5e1d7f 100644
--- a/tests/data-structures-tests.scm
+++ b/tests/data-structures-tests.scm
@@ -47,6 +47,8 @@
 (assert (not (substring-ci=? "foo\x00a" "foo\x00b" 1 1)))
 (assert (not (substring-index "o\x00bar" "foo\x00baz")))
 (assert (not (substring-index-ci "o\x00bar" "foo\x00baz")))
+(assert (= 0 (substring-index "" "")))
+(assert (not (substring-index "foo" "")))
 (assert (= 0 (string-compare3 "foo\x00a" "foo\x00a")))
 (assert (> 0 (string-compare3 "foo\x00a" "foo\x00b")))
 (assert (< 0 (string-compare3 "foo\x00b" "foo\x00a")))
-- 
1.7.10.4