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This is related to the my previous question; Vector & Stack Overflow

But will hopefully explain the new situation (and my new question). So Yesterday i thought i had a break-through in this stack overflow exception, i thought i had solved it. Though at that time i was very tired and had quite a lot of code commented out.

This morning, re-working on my game, i started by getting everything back running. To my despair only about half an hour ago to come to the say bloody error message i thought i had overcome yesterday :/.

Alas im back at square one, but going onto the answer to my previous question, i'm looking again at trying to find the root cause which i believe is the enemies Animations. Below is my header files for the enemies & animation classes:

Anim - http://pastebin.com/uKQB1RVq

Enemies - http://pastebin.com/pktA1vXi

As you can see in my enemies class there isn't really anything note worth to talk about, that i feel would be causing this exception, apart from the Animations. (The only other thing is my Timer's class, which is just a few ints and bools, again nothing that i can consider to be memory extensive.)

So my question is this;

  1. How can i be 100% positive about this? Is there a way in my IDE (Visual C++ 2010) to see how much stack memory is being used?
  2. Leading on from q. 1, what would be a solution to this issue, for example, even though im not 100% sure the animations are the actually cause of the exception, commenting the animations out and say create a vector of animations compiles fine without issue. Would that be the way to go?

*I have testing scenario set up, i know that using the plain old 4 Animation calls if i reduce the array of Vector2's & RectArray's to 15 instead of the 20 (Just to say that these are simple structs, containing ints for the plain old x & y, and then for x, y, width & height) the game compiles up fine(Which is most likely the main reason i'm leaning towards the Animation class being the issue), if i could measure how much stack memory that it is using and then compare that with what creating a vector array of animations uses, then i should hopefully by able to make a good call on whether or not this is more importantly the real issue or if it is infact something else.

Edit: So further looking into my overflow, i'm looking into the dis-assembly information for my game. The stack overflow specific points to a specific address where the overflow happens; 0xC0000005.

Searching for that address i see that i come to this view; enter image description here

I don't really know what to make of what is held in those addresses, all i get is a very large number when i hover over it. All i can say is that there is a lot of these "???" but i suppose those could mean anything.

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  • Can't you watch at the call stack at the moment where the "exception" occurs? Commented Jul 24, 2012 at 8:01
  • The issue is that the exception doesn't specifically occur in a given file. In the stack window all i get is; i.imgur.com/lbKQM.png and out of those only 1 actually gives me any sort of code; i.imgur.com/fCail.png. I personally don't know what that file is, its titled "crtexe.c". Commented Jul 24, 2012 at 8:37
  • Actually just looked that file is part of the debugging process, which only get's flagged up because something *my stack overflow is stopping it. Commented Jul 24, 2012 at 8:44
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    The 0xC0000005 is not an address, it is the exception code for an access violation. The memory window displays ??? if there is no valid memory page at that location. Commented Jul 24, 2012 at 9:22
  • There's a good chance that something has overwritten a return address, a function pointer, or a vtable pointer somewhere; I've seen this "stack overflow" happen exactly for that reason. If you just jump to a random location, anything can happen. Sadly, that "anything" rarely involves cake. Tracking down the reason is usually tedious and far from easy if that is the cause, though. Possibly one of your objects doesn't live for quite as long as you think, and the cause can be far away from what you see in the debugger. Commented Jul 24, 2012 at 9:29

1 Answer 1

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As mentioned in answers to your previous post, there are essentially three ways to get a Stack Overflow error.

  1. Infinite recursion. This is quite easy to nail down - just check all your recursive functions, if they work correctly and will always terminate in some circumstances.

  2. Allocating huge variables on stack. That's actually connected to the first problem - the recursion stack overflow occurs, because there is no space on the stack for local variables of another recursive call. It's also easy to nail down - you would have to use many (or few, but big) statically alocated arrays (of size known at compile time) or structures to cause the problem.

  3. Bufer overrun. That's the worst nightmare to track down, because the actual problem can occur long after its cause.

I would suggest trying to nail down the problem in the following ways.

  • Comment out as much code as you can, while the problem still occurs. If you're lucky, you will comment out the place, which actually causes the problem. Otherwise you will have a lot less code to analyse.
  • Use WinDbg (available in the platform SDK) to get the detailed call stack at the moment of crash. You may add the following entry to the system registry to force the operating system to collect partial or full process memory dump to a file, such that you may try to perform post-mortem analysis:

Windows Registry Editor Version 5.00



[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Windows Error Reporting\LocalDumps\YourAppName.exe]
"DumpFolder"=hex(2):63,00,3a,00,5c,00,44,00,75,00,6d,00,70,00,73,00,00,00
"DumpType"=dword:00000002
"DumpCount"=dword:0000000F

This change makes full dump to a c:\dumps folder each time application crashes.

Windows Registry Editor Version 5.00



[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Windows Error Reporting\LocalDumps\YourAppName.exe]
"DumpFolder"=hex(2):63,00,3a,00,5c,00,44,00,75,00,6d,00,70,00,73,00,00,00
"DumpType"=dword:00000001
"DumpCount"=dword:000000FF

This change makes small dump (~40 Mb) to a c:\dumps folder each time application crashes.

  • Use the Application Verifier tool to track down potential buffer overruns, which may damage the return address stored on the stack.

  • Add guards to some vital fields of your structures and classes, ie:

const char * sentry1 = "0123456789";
void * vitalField;
const char * sentry2 = "0123456789";

Use them especially on the beginnings and ends of your classes, structures and methods. Use the debug mode to ensure, that optimizer won't optimize them out (as unused).

After the crash, collect the memory dump and try to check, if all of your guards stand unchanged (that may be difficult, but not impossible).

  • Finally, you may do a very detailed code review to make sure, that no buffer overruns occur.

Edit:

You can make WinDbg dump testing a little more automatic in the following way:

  • Set the following environment variable:

_NT_SYMBOL_PATH=symsrv*symsrv.dll*c:\symbols*http://msdl.microsoft.com/download/symbols

It will be used by WinDbg, Visual Studio and Process Explorer

  • Create the following file in the WinDbg directory:

commands.txt 

.sympath+.
.reload
kb

  • Add the following entry to your registry (check, whether your system is 32- or 64-bit and make changes, if necessary):

Windows Registry Editor Version 5.00



[HKEY_CLASSES_ROOT.dmp]
@="Debugger.Dump"



[HKEY_CLASSES_ROOT\Debugger.Dump]



[HKEY_CLASSES_ROOT\Debugger.Dump\Shell]



[HKEY_CLASSES_ROOT\Debugger.Dump\Shell\Debug_Without_Remote]
@="WinDbg This Dump"



[HKEY_CLASSES_ROOT\Debugger.Dump\Shell\Debug_Without_Remote\Command]
@="\"C:\Program Files\Debugging Tools for Windows (x64)\windbg\" -z \"%1\" -QY -c \"$<C:\Program Files\Debugging Tools for Windows (x64)\commands.txt\""

Good luck :)

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