go-delve/delve · error

malformed delve header note

Error message

malformed delve header note: %q

What it means

platformFromNotes parses the Delve header note embedded in a core dump, whose first line must be '<OS>/<arch>'. If the note type matches but the first line does not split into exactly two slash-separated parts, the note is considered malformed and this error is thrown instead of guessing the platform.

Solutions

1. Regenerate the core dump with an unmodified, matching version of delve (dlv core / dlv debug with core support).
2. Verify the note payload: the first line must be exactly 'GOOS/GOARCH', e.g. 'linux/amd64'.
3. Check for file truncation or corruption by comparing the core file size against the original.
4. If the core came from another tool, open it with the tool-appropriate debugger instead of delve.

Example fix

// before (malformed note written by custom tool)
desc := []byte("linux amd64") // no slash
// after (correct delve header note format)
desc := []byte("linux/amd64\n...")

// Inspect the delve header note before loading
parts := strings.SplitN(firstLine, "/", 2)
if len(parts) != 2 || parts[0] == "" || parts[1] == "" {
	return fmt.Errorf("note first line %q is not GOOS/GOARCH", firstLine)
}

func isWellFormedDelveHeader(desc []byte) bool {
	lines := strings.Split(string(desc), "\n")
	v := strings.Split(lines[0], "/")
	return len(v) == 2 && v[0] != "" && v[1] != ""
}

When it happens

Trigger: Calling readLinuxOrPlatformIndependentCore on a core file that contains a note with type elfwriter.DelveHeaderNoteType whose Desc payload's first line is not of the form 'linux/amd64' (e.g. no slash, or more than one slash).

Common situations: Core files produced by modified, hand-edited, or third-party tools that imitate the delve header note; truncated or corrupted note payloads; files written by a different delve version with a changed header format.

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)
• malformed delve header note (bad pid)
• reading name
• aligning after desc
• aligning after name

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/44b328ff17a80a49. Report an issue: GitHub.

Appendix: source

Thrown at pkg/proc/core/delve_core.go:23

	"encoding/binary"
	"fmt"
	"strconv"
	"strings"

	"github.com/go-delve/delve/pkg/dwarf/op"
	"github.com/go-delve/delve/pkg/elfwriter"
	"github.com/go-delve/delve/pkg/proc"
)

func platformFromNotes(notes []*note) (goos, goarch string, err error) {
	for _, note := range notes {
		if note.Type != elfwriter.DelveHeaderNoteType {
			continue
		}
		lines := strings.Split(string(note.Desc.([]byte)), "\n")
		v := strings.Split(lines[0], "/")
		if len(v) != 2 {
			return "", "", fmt.Errorf("malformed delve header note: %q", string(note.Desc.([]byte)))
		}
		return v[0], v[1], nil
	}
	panic("internal error")
}

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]

View on GitHub (pinned to a23773e6c3)