cross-rs/cross · error

rust-std is not available for

Error message

rust-std is not available for {target}

What it means

Warning raised in warn_on_failure after a target build/command fails: the target requested is a builtin target, and rustup reports that the rust-std component (rust-std-{target}) is not available for the selected toolchain. This usually means the target is not installed on that toolchain, so cross reminds the user to add the component before retrying.

Solutions

1. Run `rustup target add <target>` for the toolchain in use
2. Switch to a toolchain that ships the rust-std component for this target
3. If the target genuinely has no rust-std for any toolchain, use a custom target specification JSON with a core built for it

When it happens

Trigger: Thrown at src/lib.rs:486 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of cross-rs/cross@8c1a8aa4b6 (2026-09-13). Data as JSON: /api/errors/e26137483cdc904c. Report an issue: GitHub.

Appendix: source

Thrown at src/lib.rs:486

    pub fn uses_zig(self) -> bool {
        self == CommandVariant::Zig
    }

    pub(crate) fn is_shell(self) -> bool {
        self == CommandVariant::Shell
    }
}

fn warn_on_failure(
    target: &Target,
    toolchain: &QualifiedToolchain,
    msg_info: &mut MessageInfo,
) -> Result<()> {
    let rust_std = format!("rust-std-{target}");
    if target.is_builtin() {
        let component = rustup::check_component(&rust_std, toolchain, msg_info)?;
        if component.is_not_available() {
            msg_info.warn(format_args!("rust-std is not available for {target}"))?;
            msg_info.note(
                format_args!(
                    r#"you may need to build components for the target via `-Z build-std=<components>` or in your cross configuration specify `target.{target}.build-std`
              the available components are core, std, alloc, and proc_macro"#
                ),
            )?;
        }
    }
    Ok(())
}

fn add_libc_version(triple: &str, zig_version: Option<&str>) -> String {
    match zig_version {
        Some(libc) => format!("{triple}.{libc}"),
        None => triple.to_owned(),
    }
}

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