C - Lua memory issues

Nicholas · 2014-07-31T14:49:28

Hello, it has taken me awhile to realize, but I notice that there is a spike in memory any time a lua file is being accessed, and it never goes down. I have read around that after awhile there are garbage collections, but I have yet to encounter any. I switched between my games two levels so many times it went from 4mb usage to 1gb usage. A level is loaded like so: int parse_level(const char* filename) { /* initialize Lua */ L = lua_open(); /* load Lua base libraries */ luaL_openlibs(L); /* load the Lua file */ if(luaL_loadfile( L, filename) || lua_pcall(L, 0, 1, 0)) { printf("ERROR: something is wrong with the file!\n"); } /* parse information */ /* negative indexing means (lua_gettop(L) - n) + 1 push table to -1 */ lua_pushvalue(L, -1); /* grab the lvl_width and lvl_height */ lvl_width = get_number(L, "width"); lvl_height = get_number(L, "height"); /* grab the lvl_name */ lua_getfield(L, -1, "properties"); lvl_name = get_string(L, "name"); lua_pop(L, 1); /* before we go to finish parsing, set up the level */ level_back2 = malloc(sizeof(int) * lvl_width * lvl_height); level_back1 = malloc(sizeof(int) * lvl_width * lvl_height); level_fore = malloc(sizeof(int) * lvl_width * lvl_height); /* finish parsing by analyzing the tile layers and objects */ lua_getfield(L, -1, "layers"); /* acquire the tiles placements */ /* BACKGROUND LAYER 2 */ lua_rawgeti(L, -1, 1); lua_getfield(L, -1, "data"); int i; for( i = 0; i < lvl_width * lvl_height; i++ ) { lua_rawgeti(L, -1, i + 1); level_back2[i] = lua_tonumber(L, -1); lua_pop(L, 1); } lua_pop(L, 2); /* BACKGROUND LAYER 1 */ lua_rawgeti(L, -1, 2); lua_getfield(L, -1, "data"); for( i = 0; i < lvl_width * lvl_height; i++ ) { lua_rawgeti(L, -1, i + 1); level_back1[i] = lua_tonumber(L, -1); lua_pop(L, 1); } lua_pop(L, 2); /* FOREGROUND LAYER */ lua_rawgeti(L, -1, 3); lua_getfield(L, -1, "data"); for( i = 0; i < lvl_width * lvl_height; i++ ) { lua_rawgeti(L, -1, i + 1); level_fore[i] = lua_tonumber(L, -1); lua_pop(L, 1); } lua_pop(L, 2); /* acquire objects */ lua_rawgeti(L, -1, 4); lua_getfield(L, -1, "objects"); /* get the number of objects in the table */ int t = lua_objlen( L, -1 ); total_objects = t; /* allocate the number of objects */ alloc_obj( t ); /* process each object */ for( i = 0; i < t; i++ ) { lua_rawgeti(L, -1, i + 1); /* print object information to console */ if( print_info == true ) { printf("--OBJECT--\n"); print_string(L, "name"); print_string(L, "type"); print_number(L, "x"); print_number(L, "y"); print_number(L, "width"); print_number(L, "height"); printf("----------\n"); } /* get object information */ char *obj_name = get_string(L, "name"); char *obj_type = get_string(L, "type"); int obj_x = get_number(L, "x"); int obj_y = get_number(L, "y"); int obj_w = get_number(L, "width")/2; int obj_h = get_number(L, "height"); /* create object with information */ create_obj( i, obj_name, obj_type, obj_x, obj_y, obj_w, obj_h ); lua_pop(L, 1); } lua_pop(L, 3); /* close Lua */ lua_close(L); L = NULL; } If you need to know what kind of lua file it reads, make a level in Tiled Map Editor, then go to file -> export as -> Lua. The levels are along the lines of: return { properties = { ... }, tilesets = { ... }, layers = { ... } } I also have a object script in my game, just one right now, for the player. Player = {} function Player:new() local object = { ... } setmetatable(object, { __index = Player }) return object end function obj_load() p = Player:new() p.ySpeed = p.max_vel return p end function proc() ... end When the object is created in the parse_level() function, it opens lua with it's own lua state (for example, every object has an ID, which accesses it's stuff from a struct; so it would be obj[ID].L) and pcalls it, and then lua_getglobal( obj[ID].L, "obj_load" ); lua_call( obj[ID].L, 0, 1 ); obj[ID].script_loaded = true; and that's that. In my object function which runs in a loop, it operates the object of the ID it is given, and it sits around doing: lua_getglobal( obj[ID].L, "proc" ); lua_call( obj[ID].L, 0, 1 ); So you may or may not notice any memory issues that I have, but I am still going to go into more detail. If those last two code lines I posted are not commented out, then the game increases in memory regularly; but if they are commented out, then the game increases in memory only when changing levels (because that's when a lua file is ran, but is closed). So I have pinpointed my memory issue to lua, I just do not know where or how to fix. Any ideas? Thanks Here is the results.txt I got from Dr.Memory [attachment=22812:drmemory_results_7-26-2014.txt] EDIT: I saw this recently: http://stackoverflow.com/questions/9671793/limiting-a-lua-scripts-memory-usage however while the code for the function did compile, I never could figure out how to incorporate it and have the memory limited or that second part of code he posted. So if you tell me that this is what lua does, then is there a way to limit lua's memory usage? I would like to limit it.

Engines and Middleware Programming

Started by NicholasLopez July 26, 2014 05:06 PM

12 comments, last by NicholasLopez 9 years, 8 months ago

snake5

1,589

July 30, 2014 07:11 AM

the game crashes if I just make everything L

There could be many reasons behind the crash. It's probably one of the last unaddressable access errors in the log. I see invalid printf usage (which probably comes from `lvl_name = get_string(L, "name");`, which could've been freed somewhere) and issues with SDL (though I don't see any SDL code there).

I'm not entirely sure how to do that

Use tables. Store object-specific data in tables, which could then be stored in a global [object_id -> object_table] table. I'm rusty with my Lua API skills as well as I don't quite understand your code so I can't give the exact code for this. But I can say that it involves lua_getfield, lua_setfield, lua_getglobal and lua_setglobal, most of which were already used in your code.

SGScript scripting language | GitHub | Pastebin

NicholasLopez

130

Author

July 30, 2014 03:51 PM

get_string is like this:


char *get_string(lua_State *L, const char *key) { 
	/*	assumes there's a table at -1
		this puts the table[key] value at -1 on the stack */
	lua_getfield(L, -1, key); /* -- (top) table[key] table ... */
	/* get the value at -1 as a string */
	const char* result = lua_tostring(L, -1);    
	/* remove it from the stack */
	lua_pop(L, 1);	
	/* return the value */
	return (char *)result;
}

and I know it's not an SDL issue, and there are no memory leakages right now. However that is because I commented out the code inside the object functions that pertain to lua. Don't understand what you mean with tables. Isn't there a way to copy the script into a c side variable, and than just have that read from/cleared when it's done?

snake5

1,589

July 31, 2014 06:51 AM

The problem is not in get_string, it's in the global variable you assign a string with unknown lifetime to. As soon as that string is freed (lua_close at the latest, possibly before that), the variable becomes invalid, it's what people call a dangling pointer.

Don't understand what you mean with tables.

Tables. Tables. Tables. Tables. (click on each link to learn something). At this point it seems like there's no place for not understanding things anymore - if you still don't understand, I suggest practicing with something easier first. If you want to solve the problem, I expect you to know something about Lua tables and be able to look up the things you don't know yourself.

Isn't there a way to copy the script into a c side variable, and than just have that read from/cleared when it's done?

Sure, there is. Compiling the script every time you want to run it will probably be slower than you expect, though.

SGScript scripting language | GitHub | Pastebin

NicholasLopez

130

Author

July 31, 2014 02:49 PM


-- the object
Player = {}

-- ID is set upon object load
ID = nil

-- define the object
function Player:new()
	-- define our parameters here
	local object = {
		x = 0,
		y = 0,
		w = 16,
		h = 32,
		dir = 1,
		xSpeed = 0,
		ySpeed = 0,
		gravity = 30,
		max_vel = 160,
		onground = true,
		jumping = false,
		falling = false,
		jump_held = false,
	}
	setmetatable(object, { __index = Player })
	return object
end

I suppose I can change this first part around again. I understand how to do things, but not the vocabulary they are given. So do I just call the tables creation, and then stuff all of it's contents into a variable in C, and then run the script in my loop process with that table being placed in?

C - Lua memory issues

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