go-delve/delve · error · errSwissMapBadTableField

swiss table bad table field

Error message

swiss table bad table field

What it means

While resolving the swiss map table type, loadTypes validates the 'table' field's structure. errSwissMapBadTableField is returned when the table field does not have the expected shape (the linker records dirPtr as **table, but it can be either *[dirLen]*table for large maps or *group for small maps when dirLen==0, and Delve found neither a usable table type).

Source

Thrown at pkg/proc/mapiter.go:383

type swissTable struct {
	index  int64
	groups *Variable
}

type swissGroup struct {
	ctrls []byte

	// GOEXPERIMENT=nomapsplitgroup
	slots *Variable

	// GOEXPERIMENT=mapsplitgroup
	keys, elems *Variable
}

var (
	errSwissTableCouldNotLoad  = errors.New("could not load one of the tables")
	errSwissMapBadType         = errors.New("swiss table type does not have some required fields")
	errSwissMapBadTableField   = errors.New("swiss table bad table field")
	errSwissMapBadGroupTypeErr = errors.New("bad swiss map type, group type lacks some required fields")
	errSwissTableNilGroups     = errors.New("bad swiss map, groups pointer is nil")
)

// loadTypes determines the correct type for it.dirPtr:  the linker records
// this type as **table but in reality it is either *[dirLen]*table for
// large maps or *group for small maps, when it.dirLen == 0.
func (it *mapIteratorSwiss) loadTypes() {
	tableptrptrtyp, ok := it.dirPtr.DwarfType.(*godwarf.PtrType)
	if !ok {
		it.v.Unreadable = errSwissMapBadTableField
		return
	}
	tableptrtyp, ok := tableptrptrtyp.Type.(*godwarf.PtrType)
	if !ok {
		it.v.Unreadable = errSwissMapBadTableField
		return
	}

View on GitHub (pinned to a23773e6c3)

Solutions

1. Upgrade Delve to the latest release supporting the target Go version
2. Rebuild the target binary with a supported, stock Go toolchain release
3. If the map is small, note that small maps use *group layout — ensure Delve supports the dirLen==0 path (update if not)

// Confirm binary/Delve alignment before iterating swiss maps:
//   go version <binary> && dlv version
// Mismatch here is the primary cause of table-field decode failures.

if errors.Is(err, errSwissMapBadTableField) || strings.Contains(err.Error(), "bad table field") {
    log.Printf("swiss map layout mismatch; upgrade delve for this Go release")
    return nil
}

When it happens

Trigger: Iterating a swiss map whose directory element/table field type does not decode to the expected table struct — hit in loadTypes during the first mapIteratorSwiss step for a given map.

Common situations: Go minor-version changes to internal/runtime/maps table struct fields not yet handled by the installed Delve; nonstandard toolchain builds; DWARF that describes the table field differently than the real runtime layout.

Related errors

• swiss table type does not have some required fields
• bad swiss map type, group type lacks some required fields
• wrong real type for map
• malformed map type: keys, values or tophash of a bucket is n
• malformed map type: inconsistent array length in bucket

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/40a7f7eb41995879. Report an issue: GitHub.