No such supported compiler option in C or C++ (check the docs for equivalent ifort option). Usual way is to define such variables with a local type, e.g. MYINT64,MYUINT64 and use e.g. #include typedef int_64t MYINT64 typedef uint_64t MYUINT64
Apparently, the relevant standard headers may not be supported for 32-bit Windows (where you must make appropriate change to your typedef), but should be present in 64-bit VS2010 as well as many years of linux.
The best and standards conform (C99) solution is to use stdint.h. In your case you'd like to use types int_64t & uint_64t. Older versions of Visual Studio (before 2010) don't have such a header. However, the Intel compiler comes with this header included and hence you won't need to define your own types if you use it. Thus using stdint.h with Intel compiler should be easy, reliable and even portable (e.g. from Windows to Linux). You only need to take care when using another compiler instead (depends on how this compiler conforms to C99 then).