# Finch, for SchOS's own programs **Later. Not being worked on** — it is behind [1.0.md](1.0.md)'s freeze like everything else here that is not named there. This records the decision so it is not rediscovered. Finch is the author's own language: (GitHub mirror: `Nexoniarz/Finch`). The plan is to write SchOS's own applications and tools in it, in place of C, and so leave behind what C does badly: silent narrowing, signed/unsigned mixing, undefined behaviour on an out-of-range index, a forgotten `free`. ## What it is today (version 2.4.0) Measured from the repository, not from its README alone: - **LLVM front end**, C-like syntax, no semicolons, no headers, no preprocessor. It compiles through LLVM's `-O2` pipeline to native code; there is no garbage collector. - **Values, not references:** lists, text and structs copy on assignment and are freed at the end of their block. Out-of-range indexes, division by zero and null pointers stop with a runtime error rather than undefined behaviour. - **Errors as values** (`int(s) or 0`, `try read_file(p)`), maps, methods, modules. - **C interop through libclang:** `import "foo.h"` plus `link "foo"` calls any C library, structs by value and callbacks included. That is the way in to everything SchOS already has — musl, the `/dev/*` interfaces, Alpine's libraries. - **Targets:** Linux, macOS, Windows, on x86-64 and ARM64 (`src/target.cpp`; the System V, AAPCS64 and Microsoft x64 ABIs are in `src/abi.cpp`). - **Tooling:** a language server (`finch lsp`), VS Code and Kate support, 74 tests. - **Self-hosting:** `boot/` is a Finch compiler written in Finch (about 3,100 lines, against about 5,000 for the C++ one in `src/`) that builds itself to a byte-identical result — `tests/boot.sh`. ## What SchOS would need to do 1. **A `schos` target.** `finch` picks a triple, a C compiler and a linker per target. SchOS runs unmodified Alpine binaries and Alpine's musl (see [alpine.md](alpine.md)), so the first target is **the existing `x86_64-unknown-linux-musl`**, and a Finch program built on the host should run on SchOS before anything in Finch is made SchOS-specific. Test that before writing a line of target code. 2. **The compiler on SchOS.** Needs LLVM 21 and libclang, both of which Alpine packages. That is a question of apk and memory, not of SchOS. 3. **`boot/` as the SchOS-hosted compiler.** The C++ compiler needs LLVM's C++ libraries; the one in `boot/` is the candidate for being the compiler that ships in the image, once it emits through LLVM's C API or a smaller back end. 4. **Bindings** for SchOS's own interfaces (`/dev/pci`, `/dev/netdev`, schinit's job protocol, the framebuffer) — generated by the C importer from the headers in `include/uapi/`, so they are not hand-written and cannot drift from the kernel. ## What "finishing Finch" means is not settled The repository has no list of what is unfinished. Before work starts, the author names it. Candidates seen in the tree: `note.txt` and `notatka.txt` are scratch files; `OpenGL.fn` was deleted in the last commit; the `boot/` compiler is shorter than the C++ one, so some language features may exist only in the latter. **The first task is to diff the two feature sets**, not to guess. ## Rules - Nothing in the kernel is rewritten in Finch. It is for applications and tools. - No new capability starts until [the register of unfinished work](1.0.md#the-freeze-and-the-register-of-unfinished-work) is empty; this document is a plan, not an exception to that.