Table print improvements

This helps to distinguish C functions which do not have parameter information available from Lua functions without parameters.

daemon/lua/sandbox.lua.in

@@ -377,28 +377,23 @@ local function funcsign(f)
 		local function hook()
 			delay = delay - 1
 			if delay == 0 then  -- call this only for the introspected function
-				for i = 1, math.huge do
-					-- stack depth 2 is the introspected function
+				-- stack depth 2 is the introspected function
+				local debuginfo = debug.getinfo(2)
+				for i = 1, debuginfo.nparams do
 					local k = debug.getlocal(2, i)
-					if (k or '('):sub(1, 1) == '(' then
-						break  -- internal variable, skip
-					else
-						table.insert(func_args, k)
-					end
+					table.insert(func_args, k)
 				end
-			if debug.getlocal(2, -1) then
-				-- vararg function
-				table.insert(func_args, "...")
+				if debuginfo.what == 'C' then  -- names N/A
+					table.insert(func_args, '?')
+				elseif debuginfo.isvararg then
+					table.insert(func_args, "...")
+				end
+				debug.sethook(oldhook)
+				error('aborting the call to introspected function')
 			end
-			debug.sethook(oldhook)
-			error('aborting the call to introspected function')
 		end
-	end
-	oldhook = debug.sethook(hook, "c")  -- invoke hook() on function call
-	-- fake arguments, necessary to detect vararg functions
-	local fakearg = {}
-	for _ = 1, 64 do fakearg[#fakearg + 1] = true end
-	f(unpack(fakearg)) -- huh?
+		oldhook = debug.sethook(hook, "c")  -- invoke hook() on function call
+		f(unpack({}))  -- huh?
 	end)
 	return "(" .. table.concat(func_args, ", ") .. ")"
 end