golang/go · error

preprocessed profile entry missing callee

Error message

preprocessed profile entry missing callee

What it means

A serialized PGO profile is a sequence of caller/callee/weight line triplets. After reading a caller line, the next Scan returned false with no error — meaning the file ended before the callee line was present. The record is therefore incomplete.

Source

Thrown at src/cmd/internal/pgo/deserialize.go:57

		if err := scanner.Err(); err != nil {
			return nil, fmt.Errorf("error reading preprocessed profile: %w", err)
		}
		return nil, fmt.Errorf("preprocessed profile missing header")
	}
	if gotHdr := scanner.Text() + "\n"; gotHdr != serializationHeader {
		return nil, fmt.Errorf("preprocessed profile malformed header; got %q want %q", gotHdr, serializationHeader)
	}

	for scanner.Scan() {
		readStr := scanner.Text()

		callerName := readStr

		if !scanner.Scan() {
			if err := scanner.Err(); err != nil {
				return nil, fmt.Errorf("error reading preprocessed profile: %w", err)
			}
			return nil, fmt.Errorf("preprocessed profile entry missing callee")
		}
		calleeName := scanner.Text()

		if !scanner.Scan() {
			if err := scanner.Err(); err != nil {
				return nil, fmt.Errorf("error reading preprocessed profile: %w", err)
			}
			return nil, fmt.Errorf("preprocessed profile entry missing weight")
		}
		readStr = scanner.Text()

		split := strings.Split(readStr, " ")

		if len(split) != 2 {
			return nil, fmt.Errorf("preprocessed profile entry got %v want 2 fields", split)
		}

		co, err := strconv.Atoi(split[0])

View on GitHub (pinned to b6b368adc5)

Solutions

1. Regenerate the profile cleanly with Profile.WriteTo.
2. Ensure the writing process completes and the file is flushed/closed.
3. Validate with IsSerialized and check the file size before parsing.

// Sanity-check that the profile has a multiple-of-three record body.
// lines := strings.Split(strings.TrimSpace(string(data)), "\n")
// if (len(lines)-1)%3 != 0 { return errors.New("profile record count not a multiple of 3") }

// prof, err := pgo.FromSerialized(r)
// if err != nil {
//     if err.Error() == "preprocessed profile entry missing callee" ||
//        err.Error() == "preprocessed profile entry missing weight" {
//         // truncated record; regenerate the profile
//     }
//     return err
// }

When it happens

Trigger: An odd number of remaining lines (a caller with no callee) due to the file being truncated mid-record.

Common situations: A profile file that was cut off while being written (disk full, process killed), leaving a dangling caller line.

Related errors

• error reading profile header: %w
• error reading preprocessed profile: %w
• preprocessed profile missing header
• preprocessed profile malformed header; got %q want %q
• error opening target for caching: %w

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/6713efd4fbe32068. Report an issue: GitHub.