go-delve/delve · error

expression %q is unreadable: %v

Error message

expression %q is unreadable: %v

What it means

Error "expression %q is unreadable: %v" thrown in go-delve/delve.

Source

Thrown at pkg/proc/breakpoints.go:737

// process wide break point table.
func (t *Target) SetWatchpoint(logicalID int, scope *EvalScope, expr string, wtype WatchType, cond ast.Expr) (*Breakpoint, error) {
	if (wtype&WatchWrite == 0) && (wtype&WatchRead == 0) {
		return nil, errors.New("at least one of read and write must be set for watchpoint")
	}

	n, err := parser.ParseExpr(expr)
	if err != nil {
		return nil, err
	}
	xv, err := scope.evalAST(n)
	if err != nil {
		return nil, err
	}
	if xv.Addr == 0 || xv.Flags&VariableFakeAddress != 0 || xv.DwarfType == nil {
		return nil, fmt.Errorf("can not watch %q", expr)
	}
	if xv.Unreadable != nil {
		return nil, fmt.Errorf("expression %q is unreadable: %v", expr, xv.Unreadable)
	}
	if xv.Kind == reflect.UnsafePointer || xv.Kind == reflect.Invalid {
		return nil, fmt.Errorf("can not watch variable of type %s", xv.Kind.String())
	}

	// Special handling for interface types
	if xv.Kind == reflect.Interface {
		// For interfaces, we want to watch the data they point to
		// Read the interface to get the data pointer
		_, data, _ := xv.readInterface()
		if xv.Unreadable != nil {
			return nil, fmt.Errorf("error reading interface %q: %v", expr, xv.Unreadable)
		}
		if data == nil {
			return nil, fmt.Errorf("invalid interface %q", expr)
		}

		// Use the data field as our watch target

View on GitHub (pinned to a23773e6c3)

When it happens

Trigger: Thrown at pkg/proc/breakpoints.go:737 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/1ea86b471559afa4. Report an issue: GitHub.