go-delve/delve · error

invalid interface type: %v

Error message

invalid interface type: %v

What it means

When unwrapping an interface value, Delve reads the itab's type pointer field. It first tries the field named 'Type' (internal/abi.Itab layout) then falls back to '_type' (older runtime layouts); if neither struct field exists in the itab DWARF type, the interface is marked unreadable.

Source

Thrown at pkg/proc/variables.go:2091

	// +rtype -field iface.tab *itab|*internal/abi.ITab
	// +rtype -field iface.data unsafe.Pointer
	// +rtype -field eface._type *_type|*internal/abi.Type
	// +rtype -field eface.data unsafe.Pointer

	for _, f := range ityp.Field {
		switch f.Name {
		case "tab": // for runtime.iface
			tab, _ := v.toField(f) // +rtype *itab|*internal/abi.ITab
			tab = tab.maybeDereference()
			isnil = tab.Addr == 0
			if !isnil {
				var err error
				_type, err = tab.structField("Type") // +rtype *internal/abi.Type
				if err != nil {
					_type, err = tab.structField("_type") // +rtype *_type|*internal/abi.Type
					if err != nil {
						v.Unreadable = fmt.Errorf("invalid interface type: %v", err)
						return
					}
				}
			}
		case "_type": // for runtime.eface
			_type, _ = v.toField(f)
			isnil = _type.maybeDereference().Addr == 0
		case "data":
			data, _ = v.toField(f)
		}
	}
	return
}

func (v *Variable) loadInterface(recurseLevel int, loadData bool, cfg LoadConfig) {
	_type, data, isnil := v.readInterface()

	if isnil {

View on GitHub (pinned to a23773e6c3)

Solutions

1. Rebuild the debuggee with a Go version supported by your Delve build (or upgrade Delve to match the Go version)
2. Verify the binary includes DWARF for the runtime package (don't strip with -w)
3. Check the runtime ABI layout: search the binary's DWARF for internal/abi.Itab field names
4. If inspecting a core dump, ensure the core and binary are from the same build

Example fix

// before: mismatched toolchain
go build -gcflags="-N -l" main.go   // built with go1.9-era runtime
// after
go1.21 build -gcflags="-N -l" main.go  // + matching delve version

// Confirm runtime DWARF exposes abi.Itab fields before evaluating interfaces
// search DWARF for struct internal/abi.Itab fields Type/_type

v, err := dbg.EvalVariable(scope, "myIface", cfg)
if err != nil && strings.Contains(fmt.Sprint(err), "invalid interface type") {
    // upgrade delve / rebuild debuggee with supported Go version
}

When it happens

Trigger: Printing an iface-typed value whose itab struct type (from the binary's runtime DWARF) lacks both 'Type' and '_type' fields — usually a Go version mismatch between the debugger's expectations and the debuggee runtime, or missing runtime DWARF.

Common situations: Debugging a binary built with a Go runtime whose internal abi.Type layout differs from what Delve expects; core dumps with incomplete runtime type info; optimized/stripped runtimes.

Related errors

• error loading module data: %v
• invalid interface type
• could not read %d bytes from register %d (size: %d), also er
• could not read %d bytes from register %d (size: %d)
• could not read %d bytes from address %#x: %v

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/7e39f27e3b78de61. Report an issue: GitHub.