Recursive table function causes stack overflow?
So I wrote this function to print the contents of a table for debugging purposes. I've tested it in cases that I have generated, but I keep getting stack overflow errors when using it on certain tables (these being ones made by the Roblox Animation Editor, so I don't exactly know their contents hence the function) .
My question is: What could I throw at this to create a stack overflow? I get that excessive recursion could cause this, but I'm not exactly sure how I could achieve that by just traversing tables. I don't believe they're excessively large or anything, but maybe I under estimate what it takes to cause a stack overflow with this.
function DisplayTable(tab, depth) --returns a string representation of a table and it's contents.
depth = depth and depth + 1 or 1
local str = ""
for i,v in pairs(tab) do
str = str..string.rep("\t", depth)..tostring(v).."\n"
if type(v) == "table" then
str = str..DisplayTable(v, depth).."\n"
end
end
if depth == 1 then
return tostring(tab).."\n"..str --tack the original table at start.
end
return str
end
What the output looks like given a fairly normal table:
local t = {
a = "test",
1,
{5,2,5},
{"b",{1,2,3}},
{"goback",5,4,3}
}
>
table: 210EC6E0
1
table: 210EB9C0
5
2
5
table: 210EBC90
b
table: 210EC650
1
2
3
table: 210EB150
goback
5
4
3
test
1 answer
Lua has a max recursion limit of 16,000+.
Tables shouldn't be that deep. One possibility would be circular references in tables, for example, something like this:
local one = {};
local two = {};
table.insert(two,one);
table.insert(one,two);
What exactly you want to show for a loop is difficult. One option would be to just stop and show ellipses instead of the table if you've already seen it, or instead refer to a number which is printed at the beginning of each table entry (I implement this here)
I would also make a minor change to your function to make it a little cleaner; make it process all objects and check at the top whether or not it's a table, rather than inside. It cleans it up a bit:
function DisplayTable(tab, depth, visited,numvisited)
--returns a string representation of a table and its contents.
visited = visited or {new=1};
depth = depth and depth + 1 or 1
local tabs = string.rep("\t",depth - 1);
local name = tostring(tab);
if type(tab) == "table" then
local loop = visited[tab];
local new = visited.new;
loop = loop or new;
visited[tab] = loop;
name = name .. " {" .. loop .. "}";
if loop == new then
visited.new = new + 1;
else
return tabs .. name .. "\n";
end
end
local out = tabs .. name .. "\n";
if type(tab) == "table" then
for i,v in ipairs(tab) do
out = out .. DisplayTable(v, depth + 1, visited);
end
end
return out;
end
0