===================================== #include<boost/integer.hpp> #ifndef SIZE_MAX #define SIZE_MAX ((size_t)-1) #endif /*It is the 'fast' size_t (unsigned integer type of the platform) */ typedef boost::uint_value_t<SIZE_MAX>::fast fsize_t; ===================================== Would the above code make any difference cross-platform? Is size_t as fast (cross-platform) as the above typedef? I believe that the above code converts whatever size_t is defined as into something that is 'fast'- the easiest for the processor to manipulate. However, what I don't know is whether size_t is already that. Also, I noticed that boost::hash returns 'size_t' so was just wondering why. I will be using hashes in different collections so had tried (above) to store them using the 'fast' boost::integer form.