From f483ce5ffef0beb6e5ab50987691d00166e8216b Mon Sep 17 00:00:00 2001
From: Pieter Noordhuis <pcnoordhuis@gmail.com>
Date: Thu, 24 Jun 2010 15:12:42 -0700
Subject: [PATCH] fix unexpected behavior on an out of range end index for
 LRANGE and LTRIM

---
 redis.c                  |  8 ++++----
 tests/unit/type/list.tcl | 11 +++++++++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/redis.c b/redis.c
index 6ac410d0..085d3553 100644
--- a/redis.c
+++ b/redis.c
@@ -5404,9 +5404,9 @@ static void lrangeCommand(redisClient *c) {
     if (start < 0) start = llen+start;
     if (end < 0) end = llen+end;
     if (start < 0) start = 0;
-    if (end < 0) end = 0;
 
-    /* indexes sanity checks */
+    /* Invariant: start >= 0, so this test will be true when end < 0.
+     * The range is empty when start > end or start >= length. */
     if (start > end || start >= llen) {
         /* Out of range start or start > end result in empty list */
         addReply(c,shared.emptymultibulk);
@@ -5444,9 +5444,9 @@ static void ltrimCommand(redisClient *c) {
     if (start < 0) start = llen+start;
     if (end < 0) end = llen+end;
     if (start < 0) start = 0;
-    if (end < 0) end = 0;
 
-    /* indexes sanity checks */
+    /* Invariant: start >= 0, so this test will be true when end < 0.
+     * The range is empty when start > end or start >= length. */
     if (start > end || start >= llen) {
         /* Out of range start or start > end result in empty list */
         ltrim = llen;
diff --git a/tests/unit/type/list.tcl b/tests/unit/type/list.tcl
index ecae5d22..8a7ea278 100644
--- a/tests/unit/type/list.tcl
+++ b/tests/unit/type/list.tcl
@@ -340,6 +340,12 @@ start_server {
             create_$type mylist {1 2 3}
             assert_equal {1 2 3} [r lrange mylist -1000 1000]
         }
+
+        test "LRANGE out of range negative end index - $type" {
+            create_$type mylist {1 2 3}
+            assert_equal {1} [r lrange mylist 0 -3]
+            assert_equal {} [r lrange mylist 0 -4]
+        }
     }
 
     test {LRANGE against non existing key} {
@@ -369,6 +375,11 @@ start_server {
             assert_equal {1 2 3 4 5} [trim_list $type 0 10]
         }
 
+        test "LTRIM out of range negative end index - $type" {
+            assert_equal {1} [trim_list $type 0 -5]
+            assert_equal {} [trim_list $type 0 -6]
+        }
+
         tags {"slow"} {
             test "LTRIM stress testing - $type" {
                 set mylist {}