This command is identical to the unbundled C compiler in /usr/ccs/bin/acc, except that the following directories are included:
User-specified include directories and libraries
The compatibility include files and directories
The default SunOS 5.x headers and libraries, if unresolved symbols remain
Compatibility package header files and libraries referenced by the compiler (cc) and linker (ld) are located in /usr/ucbinclude and /usr/ucblib.