Neil, I was able to build the latest version of the UDUNITS package on coriolis.met.tamu.edu by setting environment variables CC to "cc" and CPPFLAGS to "-Df2cFortran" before executing the configure(1) script. The problem you encountered reveals a problem with the installation of the UDUNITS package that I will fix in the next release. Basically, the configure(1) script insists on using the "-O2" option even though the GNU C compiler doesn't accept that option with invoked as c89(1). Thanks for sending this in. Regards, Steve Emmerson