I think this warning is starting to happen for valid code because of 64-bit machines.
You can avoid it by using unsigned types. I think that something like this will do the trick: #define FIXNUM_OVERFLOW_P(i) \ ((unsigned long long)(i) > MOST_POSITIVE_FIXNUM \ && (unsigned long long)(i) < MOST_NEGATIVE_FIXNUM) Thanks. I will ask people to give that a try. Is this documented as a way to avoid problems with that warning?