go-delve/delve · error

malformed delve header note (bad pid): %v

Error message

malformed delve header note (bad pid): %v

What it means

threadsFromDelveNotes reads the delve header note line-by-line; the line beginning with DelveHeaderTargetPidPrefix must be a decimal number for strconv.ParseUint to succeed. A non-numeric PID value causes this error, aborting core parsing.

Source

Thrown at pkg/proc/core/delve_core.go:47

func threadsFromDelveNotes(p *process, notes []*note) (proc.Thread, error) {
	var currentThread proc.Thread
	for _, note := range notes {
		if note.Type == elfwriter.DelveHeaderNoteType {
			buf := bytes.NewBuffer(note.Desc.([]byte))
			for {
				line, err := buf.ReadString('\n')
				if err != nil {
					break
				}
				if len(line) > 0 && line[len(line)-1] == '\n' {
					line = line[:len(line)-1]
				}
				switch {
				case strings.HasPrefix(line, elfwriter.DelveHeaderTargetPidPrefix):
					pid, err := strconv.ParseUint(line[len(elfwriter.DelveHeaderTargetPidPrefix):], 10, 64)
					if err != nil {
						return nil, fmt.Errorf("malformed delve header note (bad pid): %v", err)
					}
					p.pid = int(pid)
				case strings.HasPrefix(line, elfwriter.DelveHeaderEntryPointPrefix):
					entry, err := strconv.ParseUint(line[len(elfwriter.DelveHeaderEntryPointPrefix):], 0, 64)
					if err != nil {
						return nil, fmt.Errorf("malformed delve header note (bad entry point): %v", err)
					}
					p.entryPoint = entry
				}
			}
		}

		if note.Type != elfwriter.DelveThreadNodeType {
			continue
		}
		body := bytes.NewReader(note.Desc.([]byte))
		th := new(delveThread)
		th.regs = new(delveRegisters)

View on GitHub (pinned to a23773e6c3)

Solutions

1. Fix the header note so the PID line is a plain decimal number, e.g. 'pid: 12345'.
2. Regenerate the core dump with delve rather than editing the note manually.
3. Verify the note payload was not truncated (check Descsz vs actual bytes).
4. Confirm the producing tool's delve version matches the reading version's note format.

Example fix

// before
"pid: 0x3039" // hex not accepted
// after
"pid: 12345" // decimal only

// Validate PID line before parsing
pidStr := strings.TrimPrefix(line, DelveHeaderTargetPidPrefix)
if _, err := strconv.ParseUint(pidStr, 10, 64); err != nil {
	return fmt.Errorf("core note pid %q is not decimal", pidStr)
}

func isDecimal(s string) bool {
	_, err := strconv.ParseUint(s, 10, 64)
	return err == nil
}

When it happens

Trigger: readLinuxOrPlatformIndependentCore -> threadsFromDelveNotes encounters a header-note line like 'pid: abc' or an empty value after the PID prefix, so ParseUint(base 10, 64) fails.

Common situations: Hand-edited core notes; writing tools that emit the PID in hex (0x...) or with extra characters; truncated note payload cutting off digits.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• malformed delve header note (bad entry point): %v
• malformed delve header note: %q
• reading name: %v
• short read
• can not continue execution of core process

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/6284a6729d996c3c. Report an issue: GitHub.