Another try with volatile

include/rapidjson/document.h

diff --git a/include/rapidjson/document.h b/include/rapidjson/document.h
index 2f6bb2a..b59cc69 100644
--- a/include/rapidjson/document.h
+++ b/include/rapidjson/document.h
@@ -791,8 +791,16 @@
     // Checks whether a number can be losslessly converted to a double.

     bool IsLosslessDouble() const {

         if (!IsNumber()) return false;

-        if (IsUint64())  return static_cast<volatile uint64_t>(static_cast<volatile double>(GetUint64())) == GetUint64();

-        if (IsInt64())   return static_cast<volatile  int64_t>(static_cast<volatile double>(GetInt64()))  == GetInt64();

+        if (IsUint64()) {

+            uint64_t u = GetUint64();

+            volatile double d = static_cast<double>(u);

+            return static_cast<uint64_t>(d) == u;

+        }

+        if (IsInt64()) {

+            int64_t i = GetInt64();

+            volatile double d = static_cast<double>(i);

+            return static_cast< int64_t>(d) == i;

+        }

         return true; // double, int, uint are always lossless

     }