Solaris 64-bit Developer's Guide

Check Whether Literal Uses of long Still Make Sense

Because a long is 32 bits in the ILP32 model and 64 bits in the LP64 model, there might be cases where what was previously defined as a long is neither appropriate nor necessary. In this case, it might be possible to use a more portable derived type.

Related to this, a number of derived types might have changed under the LP64 data model for the reason stated above. For example, pid_t remains a long in the 32-bit environment, but under the 64-bit environment, a pid_t is an int. For a list of derived types modified for the LP64 compilation environment, see Appendix A, Changes in Derived Types.