Fix wrong erl_compare_ext result comparing lists

Function erl_compare_ext of erl_interface library returns
1 instead -1 when comparing lists like [0] and [0, 1000].

Credits to: Evgeny Khirin <evgeny.khirin <at> erlios.com>

2 files changed, 20 insertions, 5 deletions

diff --git a/lib/erl_interface/src/legacy/erl_marshal.c b/lib/erl_interface/src/legacy/erl_marshal.c
index a6c2f64dd0..70949a7adf 100644
--- a/lib/erl_interface/src/legacy/erl_marshal.c
+++ b/lib/erl_interface/src/legacy/erl_marshal.c
@@ -1646,11 +1646,14 @@ static int cmp_exe2(unsigned char **e1, unsigned char **e2)
       min = (i < j) ? i : j;
       k = 0;
       while (1) {
-	if (k++ == min)
-	  return compare_top_ext(e1 , e2);
-	if ((ret = compare_top_ext(e1 , e2)) == 0) 
-	  continue;
-	return ret;
+	  if (k++ == min){
+	      if (i == j) return 0;
+	      if (i < j) return -1;
+	      return 1;
+	  }
+	  if ((ret = compare_top_ext(e1 , e2)) == 0)
+	      continue;
+	  return ret;
       }
     case ERL_STRING_EXT:
       i = (**e1 << 8) | ((*e1)[1]);
diff --git a/lib/erl_interface/test/erl_ext_SUITE_data/ext_test.c b/lib/erl_interface/test/erl_ext_SUITE_data/ext_test.c
index ba1a6c66da..59e0e0cce7 100644
--- a/lib/erl_interface/test/erl_ext_SUITE_data/ext_test.c
+++ b/lib/erl_interface/test/erl_ext_SUITE_data/ext_test.c
@@ -82,6 +82,11 @@ TESTCASE(compare_list) {
     // erlang:term_to_binary([34,{a,n},a,erlang])
     unsigned char term2[] = {131,108,0,0,0,4,97,34,104,2,100,0,1,97,100,0,1,110,100,0,1,97,100,0,6,101,114,108,97,110,103,106};
 
+    // erlang:term_to_binary([0])
+    unsigned char term3[] = {131,107,0,1,0};
+    // erlang:term_to_binary([0, 1000])
+    unsigned char term4[] = {131,108,0,0,0,2,97,0,98,0,0,3,232,106};
+
     erl_init(NULL, 0);
     start_a = term1;
     start_b = term2;
@@ -90,6 +95,13 @@ TESTCASE(compare_list) {
     
     test_compare_ext("lists", start_a, end_a, start_b, end_b, 1);
 
+    start_a = term3;
+    start_b = term4;
+    end_a   = term3 + sizeof(term3);
+    end_b   = term4 + sizeof(term4);
+
+    test_compare_ext("lists1", start_a, end_a, start_b, end_b, -1);
+
     report(1);
 }