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Readme.md

@@ -18,6 +18,14 @@ Particularly useful when writing new mods that don't target older Minetest versi
 
 Potentially partially redundant with the `deprecated_lua_api_handling` setting.
 
-## License
+## Usage
 
-Written by Lars Müller and licensed under the MIT license.
+Install & enable `strictest`, then **make sure to optionally depend on it** in `mod.conf`.
+
+Note that runtime strictness always comes at a cost. Running `strictest` on production servers under heavy load is thus not advisable.
+
+---
+
+Links: [GitHub](https://github.com/appgurueu/strictest), [ContentDB](https://content.minetest.net/packages/LMD/strictest/), [Minetest Forums](https://forum.minetest.net/viewtopic.php?t=28327)
+
+License: Written by Lars Müller and licensed under the MIT license.

lua.lua

@@ -18,14 +18,9 @@ function str_mt.__index(_, key)
 	return func
 end
 
--- Completely disable string-to-number coercion
+-- Disable string-to-number coercion as much as possible
 
-local arithmetic_ops = {"add", "sub", "mul", "div", "mod", "pow", "unm"}
-for _, op in pairs(arithmetic_ops) do
-	str_mt["__" .. op] = function()
-		action"attempt to perform arithmetic on a string value"
-	end
-end
+-- Setting the metamethods unfortunately doesn't work - Lua ignores them
 
 -- Override string methods to reject anything that isn't a string
 for name, func in pairs(string) do
@@ -64,3 +59,52 @@ for name, func in pairs(math) do
 		end
 	end
 end
+
+-- `math.random` strictness
+
+-- Signed 32-bit int check
+local function int32(num)
+	if num ~= num or math.abs(num) == math.huge then
+		action"expected 32-bit signed int, got nan or inf"
+	elseif num % 1 ~= 0 then
+		action"expected 32-bit signed int, got number with fractional part"
+	elseif num >= 2^31 then
+		action"expected 32-bit signed int, got too large number"
+	elseif num < -2^31 then
+		action"expected 32-bit signed int, got too small number"
+	end
+end
+
+-- PUC Lua uses 32-bit ints internally for math.random calls with intervals:
+--[[
+	For one argument:
+
+	int u = luaL_checkint(L, 1);
+	luaL_argcheck(L, 1<=u, 1, "interval is empty");
+	lua_pushnumber(L, floor(r*u)+1);  /* int between 1 and `u' */
+
+	For two arguments:
+
+	int l = luaL_checkint(L, 1);
+	int u = luaL_checkint(L, 2);
+	luaL_argcheck(L, l<=u, 2, "interval is empty");
+	lua_pushnumber(L, floor(r*(u-l+1))+l);  /* int between `l' and `u' */
+]]
+local math_random = math.random
+function math.random(...)
+	local n = select("#", ...)
+	if n == 0 then
+		return math_random()
+	elseif n == 1 then
+		local a = ...
+		int32(a)
+		return math_random(a)
+	elseif n == 2 then
+		local a, b = ...
+		int32(a); int32(b) -- limits must be inside int32 bounds
+		int32(b - a + 1) -- range may not overflow
+		return math_random(a, b)
+	else
+		action"expected at most 2 arguments in call to math.random"
+	end
+end

mod.conf

@@ -1,4 +1,3 @@
-# HACK use a double underscore to load before "all" other mods (reverse alphabetical order)
-name = __strictest
+name = strictest
 title = Runtime Strictness
 description = Disallows questionable usage of the Lua API & Lua itself to help catch errors