Why does this cause a stack overflow? [LUA]

function printtable (t)
    for i,v in pairs (t) do
        strbuf = ""
        for iter=1, tabs, 1 do
            strbuf = strbuf .. '\t'
        end
        print(strbuf, v)
        if type(v) == "table" then
            tabs = tabs + 1
            printtable(v)
        end
        tabs = tabs - 1
    end
end

tabs=0
printtable(_G)

It shouldn't recurse that much.

>>1
You need to either not call it on cyclic structures or add in cycle detection which either represents cyclic structures in a reasonable way or aborts.