Sun Studio 12: C User's Guide

7.4.1 Derived Types That Have Grown in Size

A number of derived types have changed to now represent 64-bit quantities in the 64-bit application compilation environment. This change does not affect 32-bit applications; however, any 64-bit applications that consume or export data described by these types need to be reevaluated. An example of this is in applications that directly manipulate the utmp(4) or utmpx(4) files. For correct operation in the 64-bit application environment, do not attempt to directly access these files. Instead, use the getutxent(3C) and related family of functions.