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[adonf]

Hi,

First of all, I recently discovered WME and I'm really impressed by the amount of good work that was put into it. You did a truly amazing job, Mnemonic !

I'm working on a simple minigame to be included in an adventure game and I'm getting a crash in wme.exe when my scripts add dynamic game objects to an Array. I made a simple project that documents that, I'll post the code at the end of this message. Actually, adding the dynamic objets seems to work, but when I try to read the array's first element the executable crashes.

I tried it with v. 1.6b2 and 1.5.2, both crash. Is it something that I did wrong ?


I suppose it might have something to do with objects being freed when they're still referenced, which leads me to my next question:

How does object deallocation work in WME ? I couldn't find any documentation about it, is there some kind of garbage management that frees unreferenced objects and kills the scripts that run on them ? I know that nobody really cares about memory management on the PC but still, it would be nice for me to stop the scripts once a minigame has stopped.

Thanks
  Olivier

Code: Text

1. #include "scripts\base.inc"
2.  
3. // here comes the stuff which initializes the scene
4. actor.SkipTo(400, 400);
5. actor.Direction = DI_DOWN;
6. actor.Active = true;
7.  
8. // minigame globals
9. global TestGame;
10.  
11. ////////////////////////////////////////////////////////////////////////////////
12. // scene state
13. global Statetestcrash;
14.  
15. // default values
16. if(Statetestcrash==null)
17. {
18.   Statetestcrash.Visited = false;
19.  
20.   TestGame = new Object("scenes\Room\scr\testcrash.script");
21. }
22.  
23. ////////////////////////////////////////////////////////////////////////////////
24. // run game
25. while (TestGame.GameState != "end")
26. {
27.         TestGame.Update();
28.         Sleep(50);
29. }

Code: Text

1. #include "scripts\base.inc"
2.  
3. Initialize();
4.  
5. method Initialize()
6. {
7.         this.DropObjects = new Array();
8.         this. frames = 0;
9. }
10.  
11.  
12. method Update()
13. {
14.         this.frames = this.frames + 1;
15.        
16.         var drop_array = this.DropObjects;
17.  
18.         // create objects at frames 2 and 4
19.         if (2 == this.frames)
20.         {
21.                 Game.LOG("creating toto1");
22.                 var toto1 = new Object("scenes\Room\scr\bogus.script");
23.                 drop_array.Push(toto1);
24.         }
25.         else if (4 == this.frames)
26.         {
27.                 Game.LOG("creating toto2");
28.                 var toto2 = new Object("scenes\Room\scr\bogus.script");
29.                 drop_array.Push(toto2);
30.         }
31.  
32.         var j;
33.         var cur_drop;
34.         for  (j = 0 ; j < drop_array.Length ; j = j+1 )
35.         {
36.                 cur_drop = drop_array[j];
37.                 // In real life we would do something with cur_drop
38.                 // but to make the runtime crash we simply need to reference it.
39.         }
40.  
41.         // print the content of drop_array
42.         Game.LOG("frame num " + this.frames);
43.         Game.LOG("Size and content of drop_array:");
44.         Game.LOG(drop_array.Length);
45.         var i;
46.         for  (i = 0 ; i < drop_array.Length ; i = i+1 )
47.                 Game.LOG(drop_array[i]);
48. }

Code: Text

1. #include "scripts\base.inc"
2.  
3. // object position
4. this.PosX = 0;
5. this.PosY = 0;
6.  

Instructions: just create an default project with a scene called 'Room' and save the files into data\scenes\Room.




Oops, almost forgot the log file:

Code: [Select]

17:58: frame num 1
17:58: Size and content of drop_array:
17:58: 0
17:58: creating toto1
17:58: frame num 2
17:58: Size and content of drop_array:
17:58: 1
17:58: [object]
17:58: frame num 3
17:58: Size and content of drop_array:
17:58: 1
17:58: [object]
17:58: creating toto2
17:58: frame num 4
17:58: Size and content of drop_array:
17:58: 2
and the crash log file

Code: [Select]

---------------------------------------------------------
---------- WME crash report: 10-04-2006, 17:58 ----------
---------------------------------------------------------
wme.exe caused a EXCEPTION_ACCESS_VIOLATION in module wme.exe at 001B:00431CE2
EAX=00000000  EBX=00AE2BF8  ECX=00D6CFB8  EDX=FFFFFFFF  ESI=00D6B5B8
EDI=00579BFC  EBP=00D6CAB0  ESP=0012F598  EIP=00431CE2  FLG=00010246
CS=001B   DS=0023  SS=0023  ES=0023   FS=003B  GS=0000
Stack trace:
001B:00431CE2 (0x00020002 0x010E01F5 0x00D67FF8 0x00AE01B8) wme.exe



[Mnemonic]

How does object deallocation work in WME ? I couldn't find any documentation about it, is there some kind of garbage management that frees unreferenced objects and kills the scripts that run on them ?

WME does reference counting on the dynamically created script objects. And, yes, there was a bug, which was causing the objects to be released prematurely under certain conditions (you managed to meet...).

I (hopefully) fixed the bug now. Please check this fixed wme.exe (1.6beta2).

[adonf]

Thanks for the answer and the fix !

By the way, I managed to work around the bug by using a local variable inside the "for" block instead of a variable that is local to the whole function. Hmm, I guess this doesn't make any sense, so here's an example:

Code: Text

1.         var j;
2.         var cur_drop;
3.         for  (j = 0 ; j < drop_array.Length ; j = j+1 )
4.         {
5.                 cur_drop = drop_array[j];
6.                 // do something here
7.         }
8.  

Code: Text

1.         var j;
2.         for  (j = 0 ; j < drop_array.Length ; j = j+1 )
3.         {
4.                 var cur_drop = drop_array[j];
5.                 // do something here
6.         }
7.  

... maybe this will be of some help...

[metamorphium]

just from the sight of it, the double declaration of cur_drop looks like a bug to me though.

[adonf]

oops, bad cut and paste. i just edited the code