clockworklabs/SpacetimeDB · error · anyhow::Error

`emcmake` not found in PATH. Is Emscripten env active?

Error message

`emcmake` not found in PATH. Is Emscripten env active?

What it means

`build_cpp`'s third PATH check looks for `emcmake` (`emcmake.bat` on Windows) — the CMake wrapper Emscripten ships that injects the emscripten toolchain file. Its absence while `cmake` was found typically means CMake came from the system but the emsdk environment is only partially active (or an emsdk version missing the wrapper).

Source

Thrown at crates/cli/src/tasks/cpp.rs:60

        return Err(anyhow!("`emcc` not found in PATH. Activate Emscripten (emsdk_env)."));
    }

    #[cfg(windows)]
    let cmake_found = find_executable("cmake.exe").is_some();
    #[cfg(not(windows))]
    let cmake_found = find_executable("cmake").is_some();

    if !cmake_found {
        return Err(anyhow!("`cmake` not found in PATH."));
    }

    #[cfg(windows)]
    let emcmake_found = find_executable("emcmake.bat").is_some();
    #[cfg(not(windows))]
    let emcmake_found = find_executable("emcmake").is_some();

    if !emcmake_found {
        return Err(anyhow!("`emcmake` not found in PATH. Is Emscripten env active?"));
    }

    let build_type = if build_debug { "Debug" } else { "Release" };
    let build_dir = project_path.join("build");

    // === Configure (no generator flags; let emcmake/cmake decide or reuse existing) ===
    // This matches: emcmake cmake -B build .
    // We keep -S/-B so `project_path` can be anywhere, and pass CMAKE_BUILD_TYPE (ignored by multi-config).
    let cfg_args = [
        "cmake",
        "-S",
        ".",
        "-B",
        "build",
        &format!("-DCMAKE_BUILD_TYPE={}", build_type),
    ];
    run_command("emcmake", &cfg_args, project_path).context("Failed to configure C++ project with emcmake/cmake")?;

View on GitHub (pinned to 524b4487d9)

Solutions

1. Activate the full environment with `source ~/emsdk/emsdk_env.sh` rather than hand-adding to PATH
2. Check `which emcmake` resolves inside the emsdk tree, and that `emcc`/`emcmake` come from the same installation
3. Reinstall/activate the latest emsdk if the wrapper is genuinely missing
4. Reopen the terminal after activation so the updated PATH is in effect

Example fix

# before
export PATH=~/emsdk/upstream/emscripten:$PATH
spacetime build .            # `emcmake` not found
# after
source ~/emsdk/emsdk_env.sh
spacetime build .

# Require the full emsdk env, not a hand-built PATH
command -v emcmake >/dev/null && command -v emcc >/dev/null || { echo 'run: source emsdk_env.sh'; exit 2; }

When it happens

Trigger: Emscripten activated in a different shell than the build; a manually-split emsdk installation where `emcc` is on PATH but `emcmake` is not; sourcing only part of the env; ancient emsdk versions without the wrapper script.

Common situations: Users adding `~/emsdk/upstream/emscripten` to PATH by hand instead of sourcing `emsdk_env.sh` (which also exposes the wrapper); mixed toolchains where system cmake is found first, masking an inactive emsdk; stale shells after moving the emsdk directory.

Related errors

• `emcc` not found in PATH. Activate Emscripten (emsdk_env).
• `cmake` not found in PATH.
• Built successfully but couldn't find a .wasm under {}
• ERROR: Skipping multi-column index registration '%s.%s' beca
• ERROR: Skipping default-value registration '%s.%s' because c

AI-assisted analysis of clockworklabs/SpacetimeDB@524b4487d9 (2026-08-16). Data as JSON: /api/errors/3cb69972fb8a8335. Report an issue: GitHub.