Adds a flag to the standalone vm to throw an exception on 53-bit integer overflow.

runtime/lib/double.cc

Index: runtime/lib/double.cc
===================================================================
--- runtime/lib/double.cc	(revision 23032)
+++ runtime/lib/double.cc	(working copy)
@@ -16,6 +16,7 @@
 
 namespace dart {
 
+DECLARE_FLAG(bool, throw_on_53bit_overflow);

[siva, 2013/05/23 01:28:22]

I wonder if the flag needs to be:
throw_on_javascript_int_overflow
or something like that.

[zra, 2013/05/23 15:59:07]

Done.

 DECLARE_FLAG(bool, trace_intrinsified_natives);
 
 DEFINE_NATIVE_ENTRY(Double_doubleFromInteger, 2) {
@@ -81,7 +82,15 @@
   }
   const Bigint& big = Bigint::Handle(BigintOperations::NewFromDouble(val));
   if (BigintOperations::FitsIntoInt64(big)) {
-    return Integer::New(BigintOperations::ToInt64(big));
+    const Integer& i = Integer::Handle(
+        Integer::New(BigintOperations::ToInt64(big)));
+    if (FLAG_throw_on_53bit_overflow && !i.FitsIn53Bits()) {
+      const Array& exc_args = Array::Handle(Array::New(1));
+      exc_args.SetAt(0, Object::Handle(String::New("DoubleToInteger")));
+      Exceptions::ThrowByType(Exceptions::kFiftyThreeBitOverflowError,
+          exc_args);
+    }
+    return i.AsValidInteger();

[siva, 2013/05/23 01:28:22]

Integer::New(...) above has already done the Smi/Mint demarcation why do we need
to call AsValidInteger again over here and not just do a
return i.raw();

[zra, 2013/05/23 15:59:07]

Done.

   } else {
     return big.raw();
   }