lock unit_map while running filter or applying effects

This specially prevents lua form removing the unit that is currently
filtered or that currently gets effects, which would cause crashes
otherwise.

src/scripting/game_lua_kernel.cpp

@@ -149,6 +149,20 @@ static lg::log_domain log_scripting_lua("scripting/lua");
 std::vector<config> game_lua_kernel::preload_scripts;
 config game_lua_kernel::preload_config;
 
+struct map_locker
+{
+	map_locker(game_lua_kernel* kernel) : kernel_(kernel)
+	{
+		++kernel_->map_locked_;
+	}
+	~map_locker()
+	{
+		--kernel_->map_locked_;
+	}
+	game_lua_kernel* kernel_;
+};
+
+
 void game_lua_kernel::extract_preload_scripts(config const &game_config)
 {
 	game_lua_kernel::preload_scripts.clear();
@@ -2285,6 +2299,9 @@ int game_lua_kernel::intf_print(lua_State *L) {
  */
 int game_lua_kernel::intf_put_unit(lua_State *L)
 {
+	if(map_locked_) {
+		return luaL_error(L, "Attempted to move a unit while the map is locked");
+	}
 	int unit_arg = 1;
 	int fire_event_arg = 4;
 
@@ -2372,6 +2389,9 @@ int game_lua_kernel::intf_put_unit(lua_State *L)
  */
 int game_lua_kernel::intf_erase_unit(lua_State *L)
 {
+	if(map_locked_) {
+		return luaL_error(L, "Attempted to remove a unit while the map is locked");
+	}
 	map_location loc;
 
 	if (lua_isnumber(L, 1)) {
@@ -2420,6 +2440,9 @@ int game_lua_kernel::intf_erase_unit(lua_State *L)
  */
 int game_lua_kernel::intf_put_recall_unit(lua_State *L)
 {
+	if(map_locked_) {
+		return luaL_error(L, "Attempted to move a unit while the map is locked");
+	}
 	lua_unit *lu = NULL;
 	unit_ptr u = unit_ptr();
 	int side = lua_tointeger(L, 2);
@@ -2460,6 +2483,9 @@ int game_lua_kernel::intf_put_recall_unit(lua_State *L)
  */
 int game_lua_kernel::intf_extract_unit(lua_State *L)
 {
+	if(map_locked_) {
+		return luaL_error(L, "Attempted to remove a unit while the map is locked");
+	}
 	if (!luaW_hasmetatable(L, 1, getunitKey))
 		return luaL_typerror(L, 1, "unit");
 	lua_unit *lu = static_cast<lua_unit *>(lua_touserdata(L, 1));
@@ -4159,6 +4185,7 @@ game_lua_kernel::game_lua_kernel(CVideo * video, game_state & gs, play_controlle
 	, reports_(reports_object)
 	, level_lua_()
 	, queued_events_()
+	, map_locked_(0)
 {
 	static game_events::queued_event default_queued_event("_from_lua", map_location(), map_location(), config());
 	queued_events_.push(&default_queued_event);
@@ -4741,7 +4768,7 @@ bool game_lua_kernel::run_wml_conditional(std::string const &cmd, vconfig const
 bool game_lua_kernel::run_filter(char const *name, unit const &u)
 {
 	lua_State *L = mState;
-
+	map_locker(this);
 	unit_map::const_unit_iterator ui = units().find(u.get_location());
 	if (!ui.valid()) return false;
 
@@ -4774,6 +4801,7 @@ void game_lua_kernel::apply_effect(const std::string& name, unit& u, const confi
 	if (!luaW_getglobal(L, "wesnoth", "effects", name.c_str(), NULL)) {
 		return;
 	}
+	map_locker(this);
 	// Stack: effect_func
 	lua_unit* lu = luaW_pushlocalunit(L, u);
 	// Stack: effect_func, unit

src/scripting/game_lua_kernel.hpp

@@ -167,6 +167,15 @@ class game_lua_kernel : public lua_kernel_base
 
 public:
 	std::vector<team> & teams();
+	/**
+		A value != 0 means that the shouldn't remove any units from the map, usually because
+		we are currently operating on a unit& and removing it might cause memory corruptions
+		note that we don't check for the dtor of lua owned units because we assume that
+		we operate on such a unit that the lua function that invoked the operation on that unit
+		(like wesnoth.add_modification, wesnoth.match_unit ..) have a local copy of that
+		lua_unit* userdata in its stack that prevents it from beeing collected.
+	*/
+	int map_locked_;
 	game_lua_kernel(CVideo *, game_state &, play_controller &, reports &);
 
 	void set_game_display(game_display * gd);