Add shutdown hook interface to Lua API

Scripts can call minetest.register_on_shutdown() to register a
shutdown hook.

Document that minetest.register_on_shutdown() callbacks may not be run

If the server crashes, it is unlikely that callbacks registered using
minetest.register_on_shutdown() will be called.

3 files changed, 21 insertions, 0 deletions

diff --git a/src/scriptapi.cpp b/src/scriptapi.cpp
index 91100d311..e5815c462 100644
--- a/src/scriptapi.cpp
+++ b/src/scriptapi.cpp
@@ -5576,6 +5576,19 @@ bool scriptapi_on_chat_message(lua_State *L, const std::string &name,
 	return ate;
 }
 
+void scriptapi_on_shutdown(lua_State *L)
+{
+	realitycheck(L);
+	assert(lua_checkstack(L, 20));
+	StackUnroller stack_unroller(L);
+
+	// Get registered shutdown hooks
+	lua_getglobal(L, "minetest");
+	lua_getfield(L, -1, "registered_on_shutdown");
+	// Call callbacks
+	scriptapi_run_callbacks(L, 0, RUN_CALLBACKS_MODE_FIRST);
+}
+
 void scriptapi_on_newplayer(lua_State *L, ServerActiveObject *player)
 {
 	realitycheck(L);
diff --git a/src/scriptapi.h b/src/scriptapi.h
index 144cb3bc6..d71b8fe41 100644
--- a/src/scriptapi.h
+++ b/src/scriptapi.h
@@ -55,6 +55,9 @@ void scriptapi_environment_step(lua_State *L, float dtime);
 void scriptapi_environment_on_generated(lua_State *L, v3s16 minp, v3s16 maxp,
 		u32 blockseed);
 
+/* server */
+void scriptapi_on_shutdown(lua_State *L);
+
 /* misc */
 void scriptapi_on_newplayer(lua_State *L, ServerActiveObject *player);
 void scriptapi_on_dieplayer(lua_State *L, ServerActiveObject *player);
diff --git a/src/server.cpp b/src/server.cpp
index 961bdeaf9..67c1ce927 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -1112,6 +1112,11 @@ Server::~Server()
 			{}
 		}
 	}
+
+	/*
+		Execute script shutdown hooks
+	*/
+	scriptapi_on_shutdown(m_lua);
 	
 	{
 		JMutexAutoLock envlock(m_env_mutex);