Fix module operation to conform to IEEE 754 arithmic.

When the two operands are integers, and the result is 0 AND the
left-hand side is negative, then discard it and do the calculation based
on doubles. The reason is that the integer mod can only return +0,
while (-1 % -1) and (-1 % 1) should return -0.

Change-Id: I676e5bbdf3a7dcb29006d9101a9e5e7c33467c49
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/v4/qv4runtime.h b/src/v4/qv4runtime.h
index 74549c68a1..09581c9f4f 100644
--- a/src/v4/qv4runtime.h
+++ b/src/v4/qv4runtime.h
@@ -495,8 +495,11 @@ inline void __qmljs_mod(ExecutionContext *ctx, Value *result, const Value &left,
     TRACE2(left, right);
 
     if (Value::integerCompatible(left, right) && right.integerValue() != 0) {
-        *result = Value::fromInt32(left.integerValue() % right.integerValue());
-        return;
+        int intRes = left.integerValue() % right.integerValue();
+        if (intRes != 0 || left.integerValue() >= 0) {
+            *result = Value::fromInt32(intRes);
+            return;
+        }
     }
 
     double lval = __qmljs_to_number(left, ctx);