This is a port of the old Geoworks DOS assembly toolchain, consisting of the ESP macro assembler and the Glue linker. It's really intended to produce Geoworks .geo executables, but it's also a highly competent assembler and linker for producing DOS .com and .exe executables which is mostly compatible with masm.
This was pulled out of the main Geoworks PC-GEOS repository and then hacked and modified by me until it builds and mostly runs (as far as I've tested it, which isn't much) on my modern amd64 Linux PC. The code is extremely old, with timestamps from about 1988, and C compilers and the machines they've run on have rather changed since then. It does, however, build without warnings (although I did have to turn some of the warnings off).
ESP has its own GEOS-specific object file format, but Glue supports GEOS or Microsoft format object files.
To build it you'll need a Unixoid and the bazel build system. This is in Debian
as bazel-bootstrap or you can install it yourself from
https://bazel.build/install. Then just do make. The two binaries will end up
in bazel-bin/src/esp/esp and bazel-bin/src/glue/glue.
There's some really good documentation in the GEOS repository; it's kinda oriented around GEOS, but you can skip those bits (e.g. you probably don't want to use GEOS classes in DOS!):
None of this (except for the build scripts) was written by me, David Given dg@cowlark.com. Feel free to contact me by email at dg@cowlark.com. You may also like to visit my website; there may or may not be something interesting there.
You probably also want to visit the main GEOS github repository at https://github.com/bluewaysw/pcgeos where the upstream code is.
All of GEOS is open source software available under the Apache 2.0 license, and therefore everything here is to. I, David Given, declare that all my modifications fall under the terms of the same license.