What causes "failed to validate startup order {}: {error}" in denoland/deno?

Check encoding: `file "$DENO_STARTUP_ORDER_FILE"` — it must be ASCII/UTF-8 text, one symbol per line

failed to validate startup order {}: {error}

Error message

failed to validate startup order {}: {error}

What it means

Build-script panic in cli/build.rs. Immediately after writing the copied order file, the script reads it back with fs::read_to_string to validate its contents (counting non-empty, non-comment lines). read_to_string requires valid UTF-8; a non-UTF-8 order file (binary garbage, wrong encoding, LZ4/gzip bytes despite the extension) makes this read fail and panics as "failed to validate startup order <path>".

Source

Thrown at cli/build.rs:505

    })
  } else {
    std::fs::read(&source).unwrap_or_else(|error| {
      panic!("failed to read startup order {}: {error}", source.display())
    })
  };

  // Always use the same linker path for generated orders. Full-LTO output can
  // change when only the order-file path changes.
  let order_file = out_dir.join(format!("startup-order-{target}.order"));
  std::fs::write(&order_file, contents).unwrap_or_else(|error| {
    panic!(
      "failed to write startup order {}: {error}",
      order_file.display()
    )
  });

  let contents = std::fs::read_to_string(&order_file).unwrap_or_else(|error| {
    panic!(
      "failed to validate startup order {}: {error}",
      order_file.display()
    )
  });
  let symbol_count = contents
    .lines()
    .filter(|line| !line.is_empty() && !line.starts_with('#'))
    .count();
  if symbol_count < 1_000 {
    panic!(
      "startup order {} has only {symbol_count} symbols",
      order_file.display()
    );
  }

  let order_file = order_file.canonicalize().unwrap();
  match target.as_str() {
    "aarch64-apple-darwin" => println!(

View on GitHub (pinned to 9ad36f7a2c)

Solutions

Check encoding: `file "$DENO_STARTUP_ORDER_FILE"` — it must be ASCII/UTF-8 text, one symbol per line
If the payload is another compression format, decompress it and supply the raw text file (or properly .zst-compress it)
Regenerate the order file with the supported generator so it is plain text lines with optional # comments

Example fix

# before
DENO_STARTUP_ORDER_FILE=deno.order.gz    # gz bytes, not utf-8
# after
gunzip -c deno.order.gz > deno.order
DENO_STARTUP_ORDER_FILE=$PWD/deno.order

Defensive patterns

Strategy: validation

Validate before calling

file "$DENO_STARTUP_ORDER_FILE"            # expect: ASCII text / UTF-8
iconv -f utf-8 -t utf-8 "$DENO_STARTUP_ORDER_FILE" >/dev/null || echo 'not valid UTF-8'

Prevention

Generate order files as plain UTF-8/ASCII text, one symbol per line
On Windows avoid PowerShell redirects that emit UTF-16 (use cmd redirect or set output encoding)

When it happens

Trigger: The decoded order-file bytes are not UTF-8 text — e.g. the file is still compressed under a non-.zst name, is UTF-16 output from a PowerShell redirect, or the .zst decoded to something that is not an order list.

Common situations: Toolchains on Windows writing UTF-16 with BOM; a generation script emitting the wrong format; an artifact naming mismatch (gzip'd file named .order).

Related errors

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/c5c7dfd77360561d. Report an issue: GitHub.