Get closer to the Lua 5.2 C API

Aegisub requires Luajit implementing Lua 5.2, but the code was making a
mixture of Lua 5.1 and Lua 5.2 C API calls which happened to work
because luajit's standards compliance is loose. A call to `lua_objlen()`
remains because Luajit doesn't implement Lua 5.2 fully and is missing
`lua_rawlen()`.

Tested with some out of tree patches to make Aegisub work on an
unsupported platform (OpenBSD, official Lua).

libaegisub/lua/modules/lpeg.c

@@ -39,10 +39,6 @@
 #undef lua_objlen
 #define lua_objlen	lua_rawlen
 
-#undef luaL_register
-#define luaL_register(L,n,f) \
-	{ if ((n) == NULL) luaL_setfuncs(L,f,0); else luaL_newlib(L,f); }
-
 #endif
 
 
@@ -2379,8 +2375,8 @@ int luaopen_lpeg (lua_State *L) {
   luaL_newmetatable(L, PATTERN_T);
   lua_pushnumber(L, MAXBACK);
   lua_setfield(L, LUA_REGISTRYINDEX, MAXSTACKIDX);
-  luaL_register(L, NULL, metapattreg);
-  luaL_register(L, "lpeg", pattreg);
+  luaL_setfuncs(L, metapattreg, 0);
+  luaL_newlib(L, pattreg);
   lua_pushliteral(L, "__index");
   lua_pushvalue(L, -2);
   lua_settable(L, -4);

src/auto4_lua.cpp

@@ -466,7 +466,6 @@ namespace {
 		stackcheck.check_stack(0);
 
 		// make "aegisub" table
-		lua_pushstring(L, "aegisub");
 		lua_createtable(L, 0, 13);
 
 		set_field<LuaCommand::LuaRegister>(L, "register_macro");
@@ -487,7 +486,7 @@ namespace {
 		set_field<lua_set_status_text>(L, "set_status_text");
 
 		// store aegisub table to globals
-		lua_settable(L, LUA_GLOBALSINDEX);
+		lua_setglobal(L, "aegisub");
 		stackcheck.check_stack(0);
 
 		// load user script

src/auto4_lua_assfile.cpp

@@ -72,15 +72,15 @@ namespace {
 	std::string get_string_field(lua_State *L, const char *name, const char *line_class)
 	{
 		get_field(L, name, line_class, lua_isstring);
-		std::string ret(lua_tostring(L, -1), lua_strlen(L, -1));
+		std::string ret = lua_tostring(L, -1);
 		lua_pop(L, 1);
 		return ret;
 	}
 
 	agi::Color get_color_field(lua_State *L, const char *name, const char *line_class)
 	{
 		get_field(L, name, line_class, lua_isstring);
-		agi::Color ret(std::string_view(lua_tostring(L, -1), lua_strlen(L, -1)));
+		agi::Color ret = std::string_view(lua_tostring(L, -1));
 		lua_pop(L, 1);
 		return ret;
 	}

subprojects/luabins/src/luabins.c

@@ -82,7 +82,10 @@ LUALIB_API int luaopen_luabins(lua_State * L)
   /*
   * Register module
   */
-  luaL_register(L, "luabins", R);
+  lua_newtable(L);
+  luaL_setfuncs(L, R, 0);
+  lua_pushvalue(L, -1);
+  lua_setglobal(L, "mylib");
 
   /*
   * Register module information