For those looking for modern MASM-compatible assembler, try JWasm:
https://github.com/JWasm/JWasm
It's a fork of OpenWatcom assembler.
It's a fork of OpenWatcom assembler.
I prefer the latter, because the documentation is better and there's a way to specify target cpu (e.g. 8086) and get errors when instructions aren't compliant.
In both cases, still much better than traditional UNIX assemblers, desiged to massage C's output as another build stage, than to actually code by hand.
Anyway thanks for the heads up.