origX := *px
	*px = ast.NewIdent(fmt.Sprintf("_cgoBase%d", i))
	fmt.Fprintf(sb, "_cgo%d := %s; ", i, gofmtPos(arg, arg.Pos()))
	*px = origX

	// Use "0 == 0" to do the right thing in the unlikely event
	// that "true" is shadowed.
	fmt.Fprintf(sbCheck, "_cgoCheckPointer(_cgoBase%d, 0 == 0); ", i)

	return true
}

// checkSlice checks whether arg has the form x[i:j], possibly inside