library_once ctor
    module ctor
        private static integer max = 0
        private static boolean array empty

        static method create takes nothing returns thistype
            local thistype this = 0
            loop
                if this >= max then
                    set max = max + 1
                    call this.ctor_new()
                    exitwhen true
                endif
                exitwhen empty[this]
                set this = this + 1
            endloop
            set empty[this] = false
            return this
        endmethod

        method destroy takes nothing returns nothing
            set empty[this] = true
        endmethod
    endmodule
endlibrary

struct mystruct extends array
    timer t
    unit u

    private method ctor_new takes nothing returns nothing
        set .t = CreateTimer()
    endmethod

    implement ctor
endstruct