Random Buffer over run - Bug?? - GameCreators Forum

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AlexI

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Location: UK

Posted: 3rd May 2009 01:55 Edited at: 3rd May 2009 02:24

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Try running the following code:

+ Code Snippet

// Includes
#include "DarkGDK.h"
#include <windows.h>
#include "commctrl.h"
using namespace std;

// GDK BEGIN ------------------------------------------------------
void DarkGDK ( void )
{

     // Work Area
     dbSetDir("C:\Documents and Settings\Alex\My Documents\Visual Studio 2008\Projects\FPWorldEditor");
        
    // Setup Buttons
    TBBUTTON tbButtons[4];
    tbButtons[3].iBitmap = 3;

    // and now everything is ready to return back to Windows
    return;
}

It causes it a buffer overflow error, any idea why? Is it a bug?

Thanks,
Alex

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Bran flakes91093

16

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Location: Crazy Land

Posted: 3rd May 2009 03:26

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I copied your exact code, ran it and also got an unhandled exception.

I fixed it by changing:

+ Code Snippet

dbSetDir("C:\Documents and Settings\Alex\My Documents\Visual Studio 2008\Projects\FPWorldEditor");

to

+ Code Snippet

dbSetDir("C:\\Documents and Settings\\Alex\\My Documents\\Visual Studio 2008\\Projects\\FPWorldEditor");

#ifdef _DEBUG
FixBugs(All);
#endif

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AlexI

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Location: UK

Posted: 3rd May 2009 03:36 Edited at: 3rd May 2009 03:38

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The code below still causes a buffer overrun with suggested changes

+ Code Snippet

// Includes
#include "DarkGDK.h"
#include <windows.h>
#include "commctrl.h"

void DarkGDK ( void ) {

	// Work Area
	dbSetDir("C:\\Documents and Settings\\Alex\\My Documents\\Visual Studio 2008\\Projects\\FPWorldEditor");

		
	// Setup Buttons
	TBBUTTON tbButtonst[4];
	tbButtonst[1].iBitmap = 3;

	return;
}

Its not an unhandled exception its a buffer over run.

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AlexI

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Location: UK

Posted: 3rd May 2009 03:47 Edited at: 3rd May 2009 03:52

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What is weird is that when you comment this out:

TBBUTTON tbButtonst[4];
tbButtonst[1].iBitmap = 3;

You no longer get the buffer overun.

The changes you said above didn't work because the file didn't exist.

I still think this is a bug, the first example should work.

Fails:

+ Code Snippet

// Includes
#include "DarkGDK.h"
#include <windows.h>
#include "commctrl.h"

void DarkGDK ( void ) {

	// Work Area
	dbSetDir("C:\Temp");
		
	// Setup Buttons
	TBBUTTON tbButtonst[4];
	tbButtonst[1].iBitmap = 3;

	return;
}

Works:

+ Code Snippet

// Includes
#include "DarkGDK.h"
#include <windows.h>
#include "commctrl.h"

void DarkGDK ( void ) {

	// Work Area
	dbSetDir("C:\Temp");
		
	// Setup Buttons
	//TBBUTTON tbButtonst[4];
	//tbButtonst[1].iBitmap = 3;

	return;
}

Works:

+ Code Snippet

// Includes
#include "DarkGDK.h"
#include <windows.h>
#include "commctrl.h"

void DarkGDK ( void ) {

	// Work Area
	dbSetDir("C:\\Temp");
		
	// Setup Buttons
	TBBUTTON tbButtonst[4];
	tbButtonst[1].iBitmap = 3;

	return;
}

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dark coder

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Posted: 3rd May 2009 06:36

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Quote: "I still think this is a bug, the first example should work."

Why should it? You used a backslash which means an escape character will be invoked; But \T isn't a valid one so it should give you a warning(assuming you have the required warning level set). Also, the point at which it crashes should become obvious once you begin to debug your program. Plus, you should have written safety code to prevent such issues as bad paths from causing errors when loading bitmaps(or whatever your button object does to cause the error).

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Michael P

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Location: London (UK)

Posted: 3rd May 2009 11:00 Edited at: 3rd May 2009 11:02

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This is not a bug, but I think there should be more error reporting in DGDK to explain what is going on. You are trying to set to an invalid directory which causes the problem. The reason that the buffer overrun doesn't occur if you don't setup the buffers is probably as follows:

1. dbSetDir writes to memory that it shouldn't do. The debugger has not yet realised this.
2. Setting up the buttons writes to this memory, and the debugger realises the error at 1 has occurred.

In C++ any letter after a \ is an escape character, which is just a special char e.g. '\n' is one character. The real backslash character is '\\' which is one backslash.

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AlexI

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Posted: 3rd May 2009 13:06

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Ok thanks for clearing that up.

Also if you specify not existent directory you also get a buffer over run.

+ Code Snippet

// Includes
#include "DarkGDK.h"
#include <windows.h>
#include "commctrl.h"

void DarkGDK ( void ) {

	// Work Area
	dbSetDir("C:\\I_DO_NOT_EXIST");
		
	// Setup Buttons
	TBBUTTON tbButtonst[4];
	tbButtonst[1].iBitmap = 3;

	return;
}

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AlexI

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Location: UK

Posted: 3rd May 2009 13:37 Edited at: 3rd May 2009 13:38

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DB Load Object also causes a buffer over run with an existent model:

+ Code Snippet

// Includes
#include "DarkGDK.h"
#include <windows.h>
#include "commctrl.h"

void DarkGDK ( void ) {

	dbLoadObject("test.X",198);

	// Setup Buttons
	TBBUTTON tbButtons[4];
	tbButtons[0].iBitmap = 0;


	// and now everything is ready to return back to Windows
	return;
}

Why is this?

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Michael P

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Location: London (UK)

Posted: 3rd May 2009 14:17

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Either the object is corrupted in some way, or the object file does not exist.

Try the following:

+ Code Snippet

// Includes
#include <DarkGDK.h>
#include <windows.h>
#include <commctrl.h>

void DarkGDK ( void )
{
	char * File = "test.x";
	if(dbFileExist(File))
	{
		dbLoadObject(File,198);
	}
	else
	{
		dbPrint("File does not exist");
		dbWaitKey();
	}

    // Setup Buttons
    TBBUTTON tbButtons[4];
    tbButtons[0].iBitmap = 0;


    // and now everything is ready to return back to Windows
    return;
}

Basically if you do anything unexpected with DGDK some sort of internal corruption will occur but no DGDK error messages will be displayed. This is pretty incompetent in my opinion, but that's the way it is

.

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AlexI

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Posted: 3rd May 2009 14:34 Edited at: 3rd May 2009 14:38

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Thanks, I agree

For my game I made a kind of wrapper for the DarkGDK functions which gives me more debug info and handles most errors, but now I have started on another project which does not use this, so I never had these kind of messages before.

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Dark GDK / Random Buffer over run - Bug??

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