zellij-org/zellij · error

rustc provided multiple host triples: {:?}

Error message

rustc provided multiple host triples: {:?}

What it means

Same `rustc -vV` parser, opposite failure: more than one line beginning with 'host' followed by ': ' was collected, so the host triple is ambiguous and the function refuses to guess.

Source

Thrown at xtask/src/test.rs:112

        .read()
        .context("Failed to determine host triple")?;
    let maybe_triple = rustc_ver
        .lines()
        .filter_map(|line| {
            if !line.starts_with("host") {
                return None;
            }
            if let Some((_, triple)) = line.split_once(": ") {
                Some(triple.to_string())
            } else {
                None
            }
        })
        .collect::<Vec<String>>();
    match maybe_triple.len() {
        0 => Err(anyhow!("rustc didn't output the 'host' triple")),
        1 => Ok(maybe_triple.into_iter().next().unwrap()),
        _ => Err(anyhow!(
            "rustc provided multiple host triples: {:?}",
            maybe_triple
        )),
    }
}

View on GitHub (pinned to 98a0837077)

Solutions

  1. Inspect `rustc -vV` output for duplicated 'host' lines and identify who adds them
  2. Remove the wrapper/shim (RUSTC_WRAPPER and similar env) so plain rustc answers
  3. Reproduce with a clean environment: `env -i PATH="$PATH" rustc -vV`

Example fix

# before: wrapper echoes "host: ..." twice
RUSTC_WRAPPER=my-echo-wrapper cargo xtask test

# after
unset RUSTC_WRAPPER
cargo xtask test
Defensive patterns

Strategy: validation

Validate before calling

# exactly one host line may appear in rustc -vV output
count=$(rustc -vV | grep -cE '^host: ' || true)
if [ "$count" -ne 1 ]; then
  echo "expected exactly 1 host line, got $count; inspect rustc -vV and remove wrappers"; exit 1
fi

Type guard

fn parse_host_triple(rustc_vv: &str) -> Option<&str> {
    let mut hits = rustc_vv.lines().filter_map(|l| l.starts_with("host").then(|| l.split_once(": ")).flatten().map(|(_, t)| t));
    let first = hits.next()?;
    hits.next().is_none().then_some(first)
}

Try / catch

match test::host_target_triple(&sh) {
    Ok(triple) => { /* proceed */ }
    Err(e) if e.to_string().contains("multiple host triples") => {
        // a wrapper is duplicating output; re-run with a clean env and retry once
    }
    Err(e) => return Err(e),
}

Prevention

When it happens

Trigger: A rustc wrapper echoing the command line or duplicating rustc's banner; environment noise prepended to rustc output; a custom rustc printing the host line twice.

Common situations: Verbose shims (sccache-style prefixes, logging wrappers) in CI; tools that `tee` compiler output; exotic toolchains that add extra host lines.

Related errors

AI-assisted analysis of zellij-org/zellij@98a0837077 (2026-08-16). Data as JSON: /api/errors/8763a2bec9a9f7cb. Report an issue: GitHub.