zeroclaw-labs/zeroclaw · error

Build failed:\n{}

Error message

Build failed:\n{}

What it means

flash_nucleo_firmware runs `cargo build --release --target thumbv7em-none-eabihf` inside firmware/nucleo and bails with cargo's stderr when the build exits non-zero. The most common cause is the embedded target not being installed in the active rustup toolchain; dependency fetch failures or firmware compile errors also surface here with full stderr.

Source

Thrown at crates/zeroclaw-hardware/src/peripherals/nucleo_flash.rs:50

    let repo_root = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
    let firmware_dir = repo_root.join("firmware").join("nucleo");
    if !firmware_dir.join("Cargo.toml").exists() {
        anyhow::bail!(
            "Nucleo firmware not found at {}. Run from zeroclaw repo root.",
            firmware_dir.display()
        );
    }

    println!("Building ZeroClaw Nucleo firmware...");
    let build = Command::new("cargo")
        .args(["build", "--release", "--target", TARGET])
        .current_dir(&firmware_dir)
        .output()
        .context("cargo build failed")?;

    if !build.status.success() {
        let stderr = String::from_utf8_lossy(&build.stderr);
        anyhow::bail!("Build failed:\n{}", stderr);
    }

    let elf_path = firmware_dir
        .join("target")
        .join(TARGET)
        .join("release")
        .join("nucleo");

    if !elf_path.exists() {
        anyhow::bail!(
            "Built binary not found at {}",
            elf_path.display().to_string()
        );
    }

    println!("Flashing to Nucleo-F401RE (connect via USB)...");
    let flash = Command::new("probe-rs")
        .args([

View on GitHub (pinned to 88bb9c8533)

Solutions

1. Install the target: `rustup target add thumbv7em-none-eabihf`
2. Read the embedded stderr — can't-find-core errors name the exact target; code errors name file and line
3. Verify standalone: `cd firmware/nucleo && cargo build --release --target thumbv7em-none-eabihf`
4. Ensure the required toolchain is present and crates.io is reachable (or deps are vendored)

let installed = std::process::Command::new("rustup")
    .args(["target", "list", "--installed"])
    .output()?;
if !String::from_utf8_lossy(&installed.stdout).contains("thumbv7em-none-eabihf") {
    std::process::Command::new("rustup")
        .args(["target", "add", "thumbv7em-none-eabihf"])
        .status()?;
}
flash_nucleo_firmware()?;

if let Err(e) = flash_nucleo_firmware() {
    let chain = format!("{e:#}"); // embedded cargo stderr names the exact failure
    if chain.contains("can't find crate for `core`") || chain.contains("not installed") {
        // missing target: rustup target add thumbv7em-none-eabihf, then retry
    }
}

When it happens

Trigger: Calling flash_nucleo_firmware() without thumbv7em-none-eabihf installed (`rustup target list --installed`), offline without vendored crates.io dependencies, or with a compile error in firmware/nucleo itself.

Common situations: First embedded build on a new machine (rustup ships without cross targets); CI containers without cached targets; toolchain mismatch with firmware/nucleo's rust-toolchain.toml (Embassy firmware).

Related errors

• Built binary not found at {}
• probe-rs not found. Install it: cargo install probe-rs-too
• Nucleo firmware not found at {}. Run from zeroclaw repo root

AI-assisted analysis of zeroclaw-labs/zeroclaw@88bb9c8533 (2026-08-23). Data as JSON: /api/errors/0827b7fc9995a111. Report an issue: GitHub.