MontaukOS/toolchain

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:

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)

Native binutils (runs on MontaukOS)

Binutils can be cross-compiled to run on MontaukOS itself (--host=x86_64-montauk), the first step toward a self-hosted GCC:

mkdir -p toolchain/build/binutils-native && cd toolchain/build/binutils-native
export PATH=$PWD/../../local/bin:$PATH
../../src/binutils-2.43.1/configure \
    --build=x86_64-pc-linux-gnu --host=x86_64-montauk \
    --target=x86_64-montauk --prefix=/usr \
    --disable-nls --disable-werror --disable-gprofng --disable-gold \
    --disable-plugins --disable-shared --enable-static
make -j$(nproc) all-gas all-ld all-binutils
make install-strip-gas install-strip-ld install-strip-binutils \
    DESTDIR=$PWD/../../native

Notes:

• Build only all-gas all-ld all-binutils. gprof needs fscanf with %[] scansets (not in the Montauk libc); gold and gprofng are disabled outright.
• The libc gained a large POSIX surface for this port (fd functions, full errno/signal sets, struct stat, sys/wait.h, utime.h, wchar.h, sys/param.h, memory.h, bsearch, sscanf field widths, ...). pex-style process spawning (fork/exec/pipe) is stubbed to fail with ENOSYS: the tools themselves never spawn, and real process plumbing is the posix_spawn milestone that needs kernel support (exit codes in SYS_WAITPID, fd redirection wiring).
• The staged tree in toolchain/native/ is not yet integrated into the OS image; that needs a target-side sysroot layout decision (where headers, libc.a and crt objects live on 0:/).