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Docs: add the Zig self-hosting roadmap

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A forward-looking design note on making danos a real Zig target
(-target x86_64-danos) and eventually running the compiler on it, focused on
the standard-library surface (not the editor/terminal).

The core realisation: Zig 0.16 (post-writergate) collapses an OS port to ONE
seam — std.fs is gone, everything routes through the std.Io vtable, and
std.posix is generic over a single per-OS `system` module (std.os.<tag>). So the
port is "write std.os.danos once" and the whole fs/process/Io tower lights up,
rather than reimplementing the namespaces.

Records the decisions this shapes now: build runtime.os (the seam, promoted into
a forked std/os/danos.zig later) plus a thin runtime.fs; retire the premature
library/posix shim (only 5 unistd call sites); do NOT hand-mirror the high-level
std namespaces; do NOT emulate the Linux ABI; defer musl. Covers the host/target/
self-host roles and the four-part compiler fork, a coverage table of what danos
has vs the gaps (mkdir/unlink/rename/truncate, richer stat, wall-clock, env, cwd,
entropy, stdio bytes), a phased plan (target -> read-side+retire-posix ->
fs-mutation+stat -> single-threaded self-linked compiler), and the risks
(fork rebase treadmill, -fsingle-threaded and -fno-llvm/-fno-lld being
load-bearing, the "w"-does-not-truncate corruption bug). Linked from the docs index.
This commit is contained in:
Daniel Samson
2026-07-13 19:26:51 +01:00
parent f52c591f5e
commit 53e42837e0
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@@ -82,6 +82,12 @@ Start with the north star:
- **[resilience.md](resilience.md) — resilience.** A design note (not built yet) on
fault isolation + live restart — the reincarnation-server + capability model that
makes "if I break it, I can restart it" real. danos's core motivation.
- **[zig-self-hosting.md](zig-self-hosting.md) — running Zig on danos.** A design note
(not built yet) on making danos a real Zig target (`-target x86_64-danos`) and
eventually running the compiler on it. The key realisation: Zig 0.16 reduces an OS
port to **one seam** (`std.os.danos`), so we build `runtime.os` (→ that seam) plus a
thin `runtime.fs`, retire the `posix` shim, and follow a phased path to
`zig build-exe hello.zig` running on danos — **not** Linux-ABI emulation.
Cutting across all of these: