Dusk OS is simple

Many software projects claim to be simple. I believe that Dusk's claim to simplicity is stronger than most non-Forth software projects.

Dusk's simplicity comes from it being a Forth. Forth's approach to simplicity is revolutionary, but it's difficult to comprehend without a good hands on experience with it. To describe this simplicity to the uninitiated, I'd say that Forth's approach to complexity is to sidestep it.

Let's try to illustrate this simplicity with examples. Because Dusk's main innovation compared to other Forths is to include a C compiler, my main reference when comparing complexity is Fabrice Bellard's Tiny C Compiler.

Tcc enjoys a very good reputation among geeks, and Fabrice Bellard is generally considered to be a genius. Nevertheless, Dusk's C compiler is 1400 lines of code and tcc, excluding backends is roughly 30,000 lines of code. At the time of this writing, Dusk CC isn't quite completed yet, but there isn't much left to add, I don't think it will exceed 2000 lines by much.

In tcc, the i386 backend weighs in at 1600 lines of code. DuskCC's "backend" is the HAL (see doc/hal), so they're not directly comparable, but Dusk's i386 kernel, which includes the whole HAL as well as everything else it needs to cold boot, is about 1000 lines of assembler code.

How can we explain this difference? It's true that Forth code is generally denser than C, but not by a factor of 15. It's true that I'm sometimes clever, but not more than Fabrice. There are multiple reasons for these differences and they all have to do with Forth's habit of side-stepping complexity.

First of all, there's relocation and binary format. tcc produces ELF binaries where Dusk CC compiles code in memory designed to run where its written. Tcc dedicates 10,000 lines of code to only file format logic. That's huge, but if you want to build a compiler in the UNIX world, you have to do this.

Forth is a memory oriented system. It comes with constraints, but it also comes with simplicity benefits. As UNIX users, we're blind to these benefits and see some of the complexity associated with computing as unavoidable. It's not. That is why Forth's approach to simplicity is revolutionary, because it removes a blindfold.

Another simplicity factor is parsing boilerplate. Tcc's assembler's input is text formatted in GNU assembler format. This parsing boilerplate is a significant part of tcc assembler-related complexity. This contraint in UNIX is inevitable because inter-process communication in UNIX generally has to be done through streams, usually in text format for maximum compatibility. This implies serialization and deserialization boilerplate at multiple levels. In Forth, memory is shared and no such constraint exists. Words communicate through structured memory. We can thus afford to sidestep this complexity and use regular Forth words to assemble binaries.

We have a good example of the kind of constraints UNIX imposes on programs by looking at i386-gen.c. In there, we see that the assembler included in tcc isn't used. Instead opcodes are directly generated in binary format. This makes sense because proceeding this way is simpler than generating textual assembler syntax in a buffer and then processing it through the assembler.

It is unfortunate, however, to have to do this because it makes the code more cryptic than in has to be. DuskCC can freely use the words from its HAL, which encapsulates encoding logic, and doesn't have to go through a clunky text interface.

Inline assembly is another interesting one. Yes, it's nice to have the option to add inline assembly to a C unit. To this end, tcc includes an assembler that weights 1200 lines with 2100 lines for the i386 backend. It's nice, but DuskCC doesn't need it because we already have the ability to mix and match C and Forth words freely and Forth words can be written in native code. We simply don't need this, we have this feature for free.

In conclusion, I think we can say that DuskCC is simpler than TinyCC because it has less features. Some of these features would, if implemented in DuskCC, make it nicer, but a good chunk of them are simply not needed in a Forth world. That is what I call "side-stepping".