# Vendored `libc` Fork — Redox `waitid` Surface

**Status:** TEMPORARY. Vendored for as long as it is required; delete once
upstream `libc` carries the Redox bindings.
**Location:** `local/sources/libc/`
**Base:** crates.io `libc` 0.2.189, unmodified except `src/unix/redox/mod.rs`.
**Version label:** `0.2.189+rb<branch>` — Cat 2 convention. `+rb` is build
metadata, which semver ignores when matching, so `^0.2` requirements still
resolve to the fork. A `-rb` suffix would read as a pre-release and fail.
**Established:** 2026-08-03.

Related: `LOCAL-FORK-SUPREMACY-POLICY.md`, `FORK-BUMP-PATCHING-POLICY.md`,
`local/AGENTS.md` § "Local fork dependency rule".

---

## Why this fork exists

relibc implements the POSIX `waitid` surface in full, but the `libc` crate's
Redox bindings never exposed it — and still do not as of 0.2.189. Any crate
that calls `waitid` therefore cannot build for `x86_64-unknown-redox`:

```
error[E0531]: cannot find unit struct, unit variant or constant
              `CLD_EXITED` in crate `libc`
error[E0531]: cannot find unit struct, unit variant or constant
              `P_ALL` in crate `libc`
```

That breaks `nix`, and through it `ctrlc` and rustc's bootstrap tooling — which
is what blocked `rust-native`, and with it the whole native toolchain
(`gcc-native`, `llvm-native`, `rust-native`) that `config/redbear-full.toml`
requires.

This is a **binding gap, not a missing implementation**. Every symbol added
here is already real in relibc:

| Symbol | relibc source | Evidence |
|---|---|---|
| `waitid()` | `src/header/sys_wait/mod.rs:153` | `nm libc.a` → `T waitid` |
| `idtype_t` | `src/header/sys_wait/mod.rs:17` | `pub type idtype_t = c_int` |
| `P_ALL` / `P_PID` / `P_PGID` | `src/header/sys_wait/mod.rs:20-24` | `0` / `1` / `2` |
| `CLD_*` (6) | `include/signal.h:457-467` | `CLD_EXITED 1` … `CLD_CONTINUED 6` |

Values and types are taken from **relibc**, not from Linux. Redox's `idtype_t`
is `c_int` where glibc uses an enum, and copying the Linux definitions would
have produced a silently wrong ABI.

## What is actually changed

One file: `src/unix/redox/mod.rs`. Every other target is byte-for-byte upstream
0.2.189, so host builds and all non-Redox targets are unaffected.

## How it is wired

`[patch.crates-io]` in the rust workspace, carried durably as
`local/patches/rust/02-libc-redox-fork.patch`:

```toml
libc = { path = "../../../../local/sources/libc" }
```

`+rb` build metadata is what makes this safe: it leaves the upstream semver
(`0.2.189`) intact, so `^0.2` requirements still resolve. A `-rb` suffix would
be read as a pre-release and fail to satisfy them — see `local/AGENTS.md`
§ "Version conventions".

Registered in `local/fork-upstream-map.toml` as `diverged`. The fork is vendored
from the crates.io **package**, whose file set differs from the upstream git tag
by construction — the package omits `.github/` and adds `.cargo_vcs_info.json` —
so a tag content-diff reports differences that mean nothing. `snapshot` mode was
tried first and produced exactly that noise. `src/unix/redox/mod.rs` is also on
the expected-differ list in `verify-fork-versions.sh` for when the mode changes.

## Retiring this fork

Upstream-reportable: the gap belongs in the `libc` crate. When upstream exposes
the Redox `waitid` surface:

1. Confirm `CLD_*`, `P_*`, `idtype_t` and `waitid` are all present in
   `src/unix/redox/mod.rs` for the version being resolved.
2. Drop `02-libc-redox-fork.patch` from `recipes/dev/rust/recipe.toml`.
3. Remove the `libc` row from `local/fork-upstream-map.toml` and both
   `libc)` arms from `verify-fork-versions.sh`.
4. Delete `local/sources/libc/`.
5. Rebuild `rust-native` to confirm `nix` still compiles.

Until then this fork stays. Bumping it follows
`FORK-BUMP-PATCHING-POLICY.md`: re-vendor the newer upstream and re-apply the
Redox block — never carry the old base forward.