Fix enif_compare on 64bits machines

In 64bits machines the Sint type has a size of 8 bytes,
while on 32bits machines it has a 4 bytes size.
enif_compare was ignoring this and therefore returning
incorrect values when the result of the CMP function
(which returns a Sint value) doesn't fit in 4 bytes.

For example, passing the operands -1294536544000 and
-1178704800000 to enif_compare would trigger the bug.

1 files changed, 9 insertions, 1 deletions

diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index d9b1a8e89d..6e7ac43676 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -578,7 +578,15 @@ int enif_is_identical(Eterm lhs, Eterm rhs)
 
 int enif_compare(Eterm lhs, Eterm rhs)
 {
-    return CMP(lhs,rhs);
+    Sint result = CMP(lhs,rhs);
+
+    if (result < 0) {
+        return -1;
+    } else if (result > 0) {
+        return 1;
+    }
+
+    return result;
 }
 
 int enif_get_tuple(ErlNifEnv* env, Eterm tpl, int* arity, const Eterm** array)