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.

2 files changed, 15 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)
diff --git a/erts/emulator/test/nif_SUITE.erl b/erts/emulator/test/nif_SUITE.erl
index 2867e8e2e4..f6344791f1 100644
--- a/erts/emulator/test/nif_SUITE.erl
+++ b/erts/emulator/test/nif_SUITE.erl
@@ -281,6 +281,12 @@ types(Config) when is_list(Config) ->
 		  end, int_list()),
 
     ?line verify_tmpmem(TmpMem),
+    ?line true = (compare(-1294536544000, -1178704800000) < 0),
+    ?line true = (compare(-1178704800000, -1294536544000) > 0),
+    ?line true = (compare(-295147905179352825856, -36893488147419103232) < 0),
+    ?line true = (compare(-36893488147419103232, -295147905179352825856) > 0),
+    ?line true = (compare(-29514790517935282585612345678, -36893488147419103232) < 0),
+    ?line true = (compare(-36893488147419103232, -29514790517935282585612345678) > 0),
     ok.
 
 int_list() ->