Greptile Summary

This PR fixes a bug where a musl-compiled mise binary running inside a minimal container (scratch, busybox — no /lib/ld-* files) would incorrectly identify itself as running on a glibc system, causing it to select glibc lockfile entries instead of musl ones. The fix adds a compile-time fallback (cfg!(target_env = "musl")) used only when neither a glibc nor a musl dynamic linker is found at runtime. A new MISE_LIBC env var override is also introduced and documented.

Key changes:

• src/platform.rs and crates/vfox/src/config.rs: Detection chain now falls back to the binary's compile-time target_env when no linker is found. Both "keep in sync" implementations are updated consistently.
• MISE_LIBC env var override: Users can explicitly force detection to musl or gnu; unknown values are ignored and fall through to runtime detection.
• /lib64 musl check: The musl linker search is extended to also scan /lib64 — this mirrors the glibc check but is dead code in practice since musl distros only use /lib.
• Docs: New section in docs/mise-cookbook/docker.md documents the MISE_LIBC override.
• Tests: New tests cover the Linux-always-returns-Some property and the musl-binary-returns-musl property; the musl-gated tests have a known CI concern discussed in prior review threads.

Confidence Score: 4/5

Core runtime logic is correct and safe to ship; minor cleanup and known test-robustness concerns remain before merge.

The fix itself is correct — the compile-time fallback is sound, MISE_LIBC validation is properly restricted to gnu/musl, and the two mirrored implementations stay in sync. Score is 4 rather than 5 because (a) the musl-gated tests can produce false failures when run on a glibc CI host, an unresolved concern noted in prior review threads, and (b) the /lib64 musl check is unnecessary dead code introduced alongside the real fix.

src/platform.rs and crates/vfox/src/config.rs — the musl-gated tests and the /lib64-for-musl filesystem scan.

Important Files Changed

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[is_musl_system / env_type called] --> B{MISE_LIBC set?}
    B -- "musl" --> R_MUSL[return musl]
    B -- "gnu" --> R_GNU[return gnu/false]
    B -- invalid / unset --> C{"/lib or /lib64\nhas ld-linux-*?"}
    C -- yes --> R_GNU
    C -- no --> D{"/lib or /lib64\nhas ld-musl-*?"}
    D -- yes --> R_MUSL
    D -- no --> E{"cfg!(target_env = musl)?"}
    E -- true --> R_MUSL
    E -- false --> F{"config.rs only:\ncfg!(target_env = gnu)?"}
    F -- true --> R_GNU
    F -- false --> R_NONE[return None]

_{Reviews (8): Last reviewed commit: "[autofix.ci] apply automated fixes" | Re-trigger Greptile}

A few things to address before merging:

1. Fix MISE_LIBC validation in config.rs — platform.rs correctly only accepts "musl" via eq_ignore_ascii_case, but config.rs blindly passes through any value (Some(val.to_lowercase())). MISE_LIBC=typo would silently produce Some("typo") and cause wrong tool selection. Validate it the same way as platform.rs.
2. Remove the tautology tests — test_mise_libc_env_var_parsing and test_mise_libc_env_var_accepted test Rust's eq_ignore_ascii_case and to_lowercase, not your actual code. The Lazy/LazyLock caching means you can't test the env var override in-process anyway, so these tests just add noise. Remove them.
3. Document MISE_LIBC — This is a useful escape hatch but it's not discoverable anywhere. Add it to the docs/settings so users can find it.

This comment was generated by Claude Code.

All addressed.