go-delve/delve · error

wrong number of arguments to cap: %d

Error message

wrong number of arguments to cap: %d

What it means

Error "wrong number of arguments to cap: %d" thrown in go-delve/delve.

Source

Thrown at pkg/proc/eval.go:1894

		// sign extension
		r |= ^uint64(0) &^ mask
	}
	return r
}

var supportedBuiltins = map[string]func([]*Variable, []ast.Expr) (*Variable, error){
	"cap":     capBuiltin,
	"len":     lenBuiltin,
	"complex": complexBuiltin,
	"imag":    imagBuiltin,
	"real":    realBuiltin,
	"min":     minBuiltin,
	"max":     maxBuiltin,
}

func capBuiltin(args []*Variable, nodeargs []ast.Expr) (*Variable, error) {
	if len(args) != 1 {
		return nil, fmt.Errorf("wrong number of arguments to cap: %d", len(args))
	}

	arg := args[0]
	invalidArgErr := fmt.Errorf("invalid argument %s (type %s) for cap", astutil.ExprToString(nodeargs[0]), arg.TypeString())

	switch arg.Kind {
	case reflect.Ptr:
		arg = arg.maybeDereference()
		if arg.Kind != reflect.Array {
			return nil, invalidArgErr
		}
		fallthrough
	case reflect.Array:
		return newConstant(constant.MakeInt64(arg.Len), arg.bi, arg.mem), nil
	case reflect.Slice:
		return newConstant(constant.MakeInt64(arg.Cap), arg.bi, arg.mem), nil
	case reflect.Chan:
		arg.loadValue(LoadFullValue())

View on GitHub (pinned to a23773e6c3)

When it happens

Trigger: Thrown at pkg/proc/eval.go:1894 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/eb6393c32ee0fb51. Report an issue: GitHub.