Add stack test

src/common/LuaSupport.cpp

@@ -129,7 +129,7 @@ bool Surge::LuaSupport::setSurgeFunctionEnvironment(lua_State *L)
     // stack is now func > table
 
     // List of whitelisted functions and modules
-    std::vector<std::string> sandboxWhitelist = {"ipairs", "error", "math", "surge"};
+    std::vector<std::string> sandboxWhitelist = {"ipairs", "error", "math", "surge", "global"};
 
     for (const auto &f : sandboxWhitelist)
     {
@@ -165,16 +165,20 @@ bool Surge::LuaSupport::setSurgeFunctionEnvironment(lua_State *L)
     lua_pop(L, 1);
 
     // clear global table
+    int stacktest = lua_gettop(L);
     lua_getglobal(L, "global");
-    lua_pushnil(L);
-    while (lua_next(L, -2))
-    {
-        lua_pop(L, 1);        // pop value
-        lua_pushvalue(L, -1); // duplicate the key
+    int stacktest2 = lua_gettop(L);
+    if (lua_type(L, -1) == LUA_TTABLE && lua_type(L, -2) == LUA_TTABLE && (stacktest2 - stacktest == 1)) {
         lua_pushnil(L);
-        lua_settable(L, -4); // clear the key
+        while (lua_next(L, -2))
+        {
+            lua_pop(L, 1);        // pop value
+            lua_pushvalue(L, -1); // duplicate the key
+            lua_pushnil(L);
+            lua_settable(L, -4); // clear the key
+        }
+        lua_pop(L, 1);
     }
-    lua_pop(L, 1);
 
     // and now we are back to f>t so we can setfenv it
     lua_setfenv(L, -2);