The GCC compiler suite in slackware-current got a major version bump last week in a dual update (the second update added the new ‘gcc-gdc’ package).
GCC version went up from 8.3.0 to 9.1.0.

I just uploaded the multilib version of the GCC packages, including that ‘gcc-gdc‘ package containing the new ‘D’ compiler.
The set of ‘*compat32’ packages was also refreshed with the latest 32bit binaries from Slackware 14.2 and -current.

Grab the packages from my server or from any mirror (those will have a few hours delay until they catch up).

Have fun, Eric