denoland/deno · error

startup ordering is only supported by the release profile

Error message

startup ordering is only supported by the release profile

What it means

Build-script panic in cli/build.rs. Startup ordering reorders functions based on a profile of a previous run, which is only meaningful for an optimized release binary with full LTO. The build script reads cargo's PROFILE and refuses to continue if DENO_USE_STARTUP_ORDER=1 is combined with a non-release profile (debug, dev, test).

Source

Thrown at cli/build.rs:452

#[allow(clippy::disallowed_methods, reason = "build code")]
fn emit_startup_order_link_args(out_dir: &Path) {
  const ENABLE_ENV: &str = "DENO_USE_STARTUP_ORDER";
  const ORDER_FILE_ENV: &str = "DENO_STARTUP_ORDER_FILE";

  println!("cargo:rerun-if-env-changed={ENABLE_ENV}");
  println!("cargo:rerun-if-env-changed={ORDER_FILE_ENV}");

  if env::var_os(ENABLE_ENV).is_none() {
    return;
  }
  if env::var(ENABLE_ENV).ok().as_deref() != Some("1") {
    panic!("{ENABLE_ENV} must be unset or set to 1");
  }

  let profile = env::var("PROFILE").unwrap();
  if profile != "release" {
    panic!("startup ordering is only supported by the release profile");
  }

  let target = env::var("TARGET").unwrap();
  match target.as_str() {
    "aarch64-apple-darwin"
    | "aarch64-unknown-linux-gnu"
    | "x86_64-unknown-linux-gnu" => {}
    _ => return,
  }

  let source =
    PathBuf::from(env::var_os(ORDER_FILE_ENV).unwrap_or_else(|| {
      panic!(
        "{ORDER_FILE_ENV} must point to an order generated from the baseline \
       release binary using the default linker layout"
      )
    }));
  let source = source.canonicalize().unwrap_or_else(|error| {

View on GitHub (pinned to 9ad36f7a2c)

Solutions

1. Build with the release profile: `DENO_USE_STARTUP_ORDER=1 cargo build --release`
2. Or unset the flag for debug builds: `unset DENO_USE_STARTUP_ORDER && cargo build`
3. Scope the env var to the single release command instead of exporting it globally

Example fix

# before
export DENO_USE_STARTUP_ORDER=1
cargo build   # panics: debug profile
# after
DENO_USE_STARTUP_ORDER=1 cargo build --release

# only enable startup ordering when also building release
if [ -n "${DENO_USE_STARTUP_ORDER:-}" ]; then
  case "$*" in *--release*) ;; *) unset DENO_USE_STARTUP_ORDER;; esac
fi
cargo build "$@"

When it happens

Trigger: DENO_USE_STARTUP_ORDER=1 is exported while running `cargo build` (debug), `cargo check`'s build scripts under a dev profile, `cargo test`, or any non---release invocation of the deno crate.

Common situations: A developer enables startup ordering in their shell or .cargo/config env block and then does a quick debug build for iteration; CI caching an env var from a release job into a debug job.

Related errors

• {ENABLE_ENV} must be unset or set to 1
• {ORDER_FILE_ENV} must point to an order generated from the b
• expected file "{file}" to exist
• cli/laufey_sums.lock has no pinned laufey version — populate
• cli/laufey_sums.lock pins Laufey v{pinned} but this build ex

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/1be9ca3f0ac4777a. Report an issue: GitHub.