The rank of longlongint shall be greater
than the rank of longint, which shall be greater than
the rank of int, which shall be greater than the rank of
shortint, which shall be greater than the rank of
signedchar.
The rank of any extended signed integer type relative to another
extended signed integer type with the same width is implementation-defined, but still subject to the other rules for determining the integer
conversion rank.
The integer conversion rank is used in the definition of the integral
promotions ([conv.prom]) and the usual arithmetic
conversions ([expr.arith.conv]).