tauri-apps/tauri · error

could not find `target_arch` when running `rustc --print cfg

Error message

could not find `target_arch` when running `rustc --print cfg`.

What it means

To derive the default target triple, the bundler runs rustc --print cfg and parses the target_arch line. The expect fires only when the command executed successfully but its stdout contains no target_arch assignment — i.e. the rustc on PATH is not behaving like a standard rustc. A command that fails outright takes the documented fallback to the compile-time architecture instead.

Source

Thrown at crates/tauri-bundler/src/bundle/platform.rs:46

  RustCfg { target_arch }
}

/// Try to determine the current target triple.
///
/// Returns a target triple (e.g. `x86_64-unknown-linux-gnu` or `i686-pc-windows-msvc`) or an
/// `Error::Config` if the current config cannot be determined or is not some combination of the
/// following values:
/// `linux, mac, windows` -- `i686, x86, armv7` -- `gnu, musl, msvc`
///
/// * Errors:
///     * Unexpected system config
pub fn target_triple() -> Result<String, crate::Error> {
  let arch_res = Command::new("rustc").args(["--print", "cfg"]).output_ok();

  let arch = match arch_res {
    Ok(output) => parse_rust_cfg(String::from_utf8_lossy(&output.stdout).into())
      .target_arch
      .expect("could not find `target_arch` when running `rustc --print cfg`."),
    Err(err) => {
      log::warn!(
      "failed to determine target arch using rustc, error: `{}`. The fallback is the architecture of the machine that compiled this crate.",
      err,
    );
      if cfg!(target_arch = "x86") {
        "i686".into()
      } else if cfg!(target_arch = "x86_64") {
        "x86_64".into()
      } else if cfg!(target_arch = "arm") {
        "armv7".into()
      } else if cfg!(target_arch = "aarch64") {
        "aarch64".into()
      } else if cfg!(target_arch = "riscv64") {
        "riscv64".into()
      } else {
        return Err(crate::Error::ArchError(String::from(
          "Unable to determine target-architecture",

View on GitHub (pinned to 52e4b6e71d)

Solutions

1. Run rustc --print cfg | grep target_arch in the same shell — it must print a target_arch line; fix or bypass whatever wrapper breaks it
2. Unset RUSTC_WRAPPER (or make the wrapper pass --print cfg through) and retry the bundle
3. Repair the toolchain: rustup update / rustup default stable, or reinstall rustup if the proxy is broken
4. Pass an explicit target (tauri build --target <triple>) so the bundler does not have to infer the arch from rustc output

Example fix

# before — wrapper breaks cfg printing
RUSTC_WRAPPER=sccache tauri build

# after — bypass the wrapper for the bundling run
env -u RUSTC_WRAPPER tauri build --target x86_64-unknown-linux-gnu

# preflight: the rustc on PATH must report target_arch
rustc --print cfg | grep -q '^target_arch=' || { echo 'rustc shim does not report target_arch — fix toolchain/wrapper'; exit 1; }

When it happens

Trigger: A RUSTC wrapper (RUSTC_WRAPPER such as an sccache variant, Nix/rustup shim) that swallows or rewrites --print cfg output; a rustup proxy misconfiguration; a toolchain so old it omits target_arch from --print cfg.

Common situations: CI with RUSTC_WRAPPER set; dev containers where rustc is a wrapper script; broken or partial rustup installs; environments overriding the RUSTC variable.

Related errors

• Unexpected target triple {}
• "rustc" could not be found, did you install Rust?
• cannot use both `resources` and `resources_map`
• Language {} not found. It must be one of {}
• Can't detect any appindicator library

AI-assisted analysis of tauri-apps/tauri@52e4b6e71d (2026-08-20). Data as JSON: /api/errors/0a76c32dc14358c1. Report an issue: GitHub.