go-delve/delve · error

malformed delve header note (bad entry point): %v

Error message

malformed delve header note (bad entry point): %v

What it means

In threadsFromDelveNotes the entry-point line of the delve header note must parse as a number; it is parsed with strconv.ParseUint using base 0 so 0x-prefixed hex is accepted. Any other malformed value produces this error.

Source

Thrown at pkg/proc/core/delve_core.go:53

			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)

		var readerr error
		read := func(out any) {
			if readerr != nil {
				return
			}

View on GitHub (pinned to a23773e6c3)

Solutions

1. Ensure the entry-point line contains a valid number (decimal or 0x-prefixed hex).
2. Regenerate the core file with the same delve version that will read it.
3. Check the note for truncation and re-dump if bytes are missing.
4. If editing notes manually, validate with strconv.ParseUint(value, 0, 64) first.

Example fix

// before
"entry point: main.main" // symbolic not accepted
// after
"entry point: 0x401000" // hex (base 0) or decimal

// Validate entry point line before parsing (base 0 allows 0x hex)
entryStr := strings.TrimPrefix(line, DelveHeaderEntryPointPrefix)
if _, err := strconv.ParseUint(entryStr, 0, 64); err != nil {
	return fmt.Errorf("core note entry point %q is not a number", entryStr)
}

func isIntegerBase0(s string) bool {
	_, err := strconv.ParseUint(s, 0, 64)
	return err == nil
}

When it happens

Trigger: readLinuxOrPlatformIndependentCore -> threadsFromDelveNotes reads a DelveHeaderEntryPointPrefix line whose value (after the prefix) is not a valid integer in base 0, e.g. 'entry point: xyz'.

Common situations: Corrupted or truncated note payload; a third-party core writer emitting a symbolic address instead of a literal; manual edits introducing stray characters.

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 pid): %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/4974fcbc5c73e358. Report an issue: GitHub.