Squeak (and Pharo) has two basic mechanisms of interfacing with the C world:
- Squeak VM plugins. That pdf is old, but still fairly accurate I guess.
- Squeak FFI, Foreign Function Interface.
The VM plugins are basically a controlled way to introduce new “named” primitives in Smalltalk that can be invoked from Smalltalk. A plugin can be built either linked into the VM binary (statically) or as a dynamically loaded library (dll, so, dylib etc). When “all else fails” a plugin is the way to go, but they are a bit awkward to work with.
Then we have the FFI which is a generic way to dynamically call dynamically loaded libraries. In other words, no compilation step needed - just type the correct Smalltalk line and the library will load and the calls work. Now… sure, the FFI mechanism is a bit slower, since it needs to look at arguments and make the proper type conversions for the call. But the FFI is heavily used in the commercial Terf system, in fact, all the OpenGL calls are done through it. So its quite proven, and not that slow.
NOTE: There are in fact several FFIs today, the old one, the one called Alien and Pharo is brewing a new one called UFFI.
Let’s see if we can use the good old FFI with Nim.