# MontaukOS Toolchains

Two cross toolchains live here, both installed to `toolchain/local/`:

| Script | Triple | Purpose |
|--------|--------|---------|
| `build-toolchain.sh` | `x86_64-elf` | Bare-metal compiler for the kernel |
| `build-montauk-toolchain.sh` | `x86_64-montauk` | OS-aware compiler for userspace programs |

Both use Binutils 2.43.1 + GCC 14.2.0 and share the source trees in
`src/`. The Montauk target is added by the patches in `patches/` plus
the target header `files/montauk.h` (installed as
`gcc/config/montauk.h` in the GCC tree).

## The x86_64-montauk target

`x86_64-montauk-gcc` knows the Montauk userspace ABI, so a hosted
program builds with no special flags:

```bash
toolchain/local/bin/x86_64-montauk-gcc hello.c -o hello.elf
```

What the target does by default:

- Links static, non-PIE `ET_EXEC` binaries (what the kernel ELF loader
  in `kernel/src/Sched/ElfLoader.cpp` accepts), text at 0x400000.
- `-z max-page-size=0x1000` — the loader maps 4 KiB pages; the x86-64
  default of 2 MiB segment alignment would bloat every binary.
- Startup/link line: `crt1.o crti.o crtbegin.o ... -lc crtend.o crtn.o`
  taken from the sysroot (`toolchain/sysroot/usr/lib`), which is
  assembled from `programs/lib/libc` by the build script.
- Headers resolve against the sysroot (`toolchain/sysroot/usr/include`),
  assembled from `programs/include/libc` plus the `montauk/` SDK
  headers. `#include <stdio.h>` just works; no `-nostdinc` needed.
- `-mno-red-zone` (the project-wide userspace convention). Standard
  hard-float SysV ABI otherwise; pass `-mno-sse` etc. per program if
  wanted.
- Defines `__montauk__` / `__MONTAUK__`.

C++ works with `-fno-exceptions -fno-rtti` (the project convention).
There is no libstdc++ yet — only libgcc is built. A hosted libstdc++
needs a more complete libc and is the next step toward self-hosting.

## Refreshing the sysroot

The sysroot is rebuilt every time `build-montauk-toolchain.sh` runs
(the compiler build steps are skipped once installed). After changing
libc headers or the libc itself, re-run the script to refresh it.

## Layout

```
toolchain/
  build-toolchain.sh           # bare-metal x86_64-elf (kernel)
  build-montauk-toolchain.sh   # x86_64-montauk (userspace)
  patches/                     # Montauk target patches (checked in)
  files/montauk.h              # GCC target header (checked in)
  src/                         # downloaded + patched sources (ignored)
  build/                       # build trees (ignored)
  local/                       # install prefix (ignored)
  sysroot/                     # generated target sysroot (ignored)
```