If you have BOTH GNU make and the normal make shipped with your system,
DO NOT use the GNU make to build this package.  If you have any errors
relating to "(" or "TOP", check that you are using /usr/ccs/bin/make as
shipped with Solaris 2.

If you get the following error whilst compiling:

In file included from /usr/local/lib/gcc-lib/sparc-sun-solaris2.3/2.6.3/include/sys/user.h:48,
                 from /usr/include/sys/file.h:15,
                 from ../ip_nat.c:15:
/usr/include/sys/psw.h:19: #error Kernel include of psw.h

That means that you have a version of gcc build under on older release
of Solaris 2.x

You need to reinstall gcc after each Solaris upgrade; gcc creates its own
set of modified system include files which are only valid for the exact
release on which gcc was build.