From 36d4c9298f4be2d1c1fb803dc16948e3c11a3a49 Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Sun, 28 Sep 2014 20:41:37 +0200
Subject: Clean the Lua context after a script has run

---
 src/control/ScriptContext.hpp | 44 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/src/control/ScriptContext.hpp b/src/control/ScriptContext.hpp
index 34dc8fc..23f0fab 100644
--- a/src/control/ScriptContext.hpp
+++ b/src/control/ScriptContext.hpp
@@ -44,13 +44,7 @@ class ScriptContext {
 private:
 	lua_State *L;
 
-public:
-	ScriptContext(const ScriptContext &other) = delete;
-	ScriptContext(ScriptContext &&other) = delete;
-	ScriptContext & operator=(const ScriptContext &other) = delete;
-	ScriptContext & operator=(ScriptContext &&other) = delete;
-
-	ScriptContext() {
+	void setupEnv() {
 		const std::pair<const char *, lua_CFunction> libs[] = {
 			{"_G", luaopen_base},
 			{"bit32", luaopen_bit32},
@@ -59,8 +53,6 @@ public:
 			{"table", luaopen_table},
 		};
 
-		L = luaL_newstate();
-
 		for (auto &lib : libs) {
 			luaL_requiref(L, lib.first, lib.second, 1);
 			lua_pop(L, 1);
@@ -70,6 +62,35 @@ public:
 			lua_pushnil(L);
 			lua_setglobal(L, f);
 		}
+	}
+
+	void cleanupEnv() {
+		lua_pushglobaltable(L);
+
+		lua_pushnil(L);
+		lua_setmetatable(L, -2);
+
+		lua_pushnil(L);
+		while (lua_next(L, -2) != 0) {
+			lua_pop(L, 1);
+
+			lua_pushvalue(L, -1);
+			lua_pushnil(L);
+
+			lua_rawset(L, -4);
+		}
+
+		lua_pop(L, 1);
+	}
+
+public:
+	ScriptContext(const ScriptContext &other) = delete;
+	ScriptContext(ScriptContext &&other) = delete;
+	ScriptContext & operator=(const ScriptContext &other) = delete;
+	ScriptContext & operator=(ScriptContext &&other) = delete;
+
+	ScriptContext() {
+		L = luaL_newstate();
 
 		lua_newtable(L);
 		lua_rawsetp(L, LUA_REGISTRYINDEX, this);
@@ -90,10 +111,15 @@ public:
 	}
 
 	void run(const std::string &name) {
+		setupEnv();
+
 		lua_rawgetp(L, LUA_REGISTRYINDEX, this);
 		lua_getfield(L, -1, name.c_str());
 		lua_remove(L, -2);
+
 		lua_call(L, 0, 0);
+
+		cleanupEnv();
 	}
 };
 
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