Sun Studio 12: C User's Guide <sys/types.h>

Include <sys/types.h> in an application source file to gain access to the definition of _LP64 and _ILP32. This header also contains a number of basic derived types that should be used whenever appropriate. In particular, the following are of special interest:

All of these types remain 32-bit quantities in the ILP32 compilation environment and grow to 64-bit quantities in the LP64 compilation environment.