Class Data Corruption

[Tim Barnes 0]

Hi, I have been experiencing corruption of private 'class' data.

I am using win2k, SourceBoost 6.70, with a 16F887 target.

 

It would appear that a "variable char array" or (pointer array using alloc)

delared as private class data, becomes over written.

 

I have included code to show the problem below. The commented out

sections are the alternative "pointer method" which produce the same symtoms.

 

The problem can be seen using the built-in debugger, although any 'watched' internal class

variables show 'error' but the 'CharBuff' variable in main shows the corrupt extracted data.

 

Any answers or "work-arounds" would be appreciated.

Regards... Tim

 

#include <system.h>


class Test
{
public:
void Test();

char mf_GetChar(int Index);  


private:


char m_Buff[3];	// Standard Method 

//	char* m_pBuff;	// Pointer Method 

};

void Test::Test(void)
{
// Standard Method 
m_Buff[0] = 'A';
m_Buff[1] = 'B';
m_Buff[2] = 'C';


/************ Pointer Method ************
m_pBuff = (char*) alloc(3);

if(m_pBuff != NULL)
{	
	m_pBuff[0] = 'A';
	m_pBuff[1] = 'B';
	m_pBuff[2] = 'C';
}
*/	

}


char Test::mf_GetChar(int Index)
{
return m_Buff[Index];	// Standard Method
//	return m_pBuff[Index];	// Pointer Method 
}




void main()
{
class Test T;
int Count = 0;

char CharBuff;

while(1)
{
	if(Count < 3)
	{
		CharBuff = T.mf_GetChar(Count);
		Count++;
	}
	else
	{
		Count = 0;
	}	

}
}

[Pavel 0]

Thanks for reporting. This bug is now fixed and the fix will be available in the next release. Problem happens inside the constructor where array element are being initialized. A workaround is to initialize array elements outside of the constructor after class object declaration.

 

Regards,

Pavel

[Tim Barnes 0]

Hi Pavel,

 

Thanks for your quick reply.

I tried your advice but the problem still remains!!

 

I did wonder if we were working on the same "Build version",

and so download the program this morning, and yes it was a different version!!

 

I would like to make a suggestion that a Build number be added to the download page.

I realise this will increase site traffic, but there must also be people just downloading

every day, just "in case" there is a new build available!

 

 

Back to the problem:

 

I have added 2 C++ programs again to show the bug. (Both "without" Constructors)

 

One prog returns corrupt data, the other enters an infinite loop.

 

I also have to say that I am now relying on the built-in debugger

for my information, and not a "real world" application.

 

Best regards

Tim

 

#include <system.h>
#include <stdio.h>
#include <stdlib.h>


class Test1
{
public:
void Initialize(void);
char mf_GetChar(int Index);  
private:
char* m_pBuff;	
};


void Test1::Initialize(void)
{
m_pBuff = (char*) alloc(4);

if(m_pBuff != NULL)
{	
	m_pBuff[0] = 'A';
	m_pBuff[1] = 'B';
	m_pBuff[2] = 'C'; //****** This line puts the debugger in to an infinite loop !!
	m_pBuff[4] = 'D';

}
}


char Test1::mf_GetChar(int Index)
{
return m_pBuff[Index];	
}





void main()
{
class Test1 T;

T.Initialize();

int Count = 0;

char CharBuff;

while(1)
{
	if(Count < 3)
	{
		CharBuff = T.mf_GetChar(Count);
		Count++;
	}
	else
	{
		Count = 0;
	}	

}
}

 

 

#include <system.h>
#include <stdio.h>
#include <stdlib.h>


class Test2
{
public:
void Initialize(void);
char mf_GetChar(int Index);  
private:
char m_Buff[3];	
};



void Test2::Initialize(void)
{
m_Buff[0] = 'A';
m_Buff[1] = 'B'; // *** This variable is returned corrupt
m_Buff[2] = 'C';
}


char Test2::mf_GetChar(int Index)
{
return m_Buff[Index];	
}




void main(void)
{
class Test2 T;

T.Initialize();

int Count = 0;

char CharBuff;

while(1)
{
	if(Count < 3)
	{
		CharBuff = T.mf_GetChar(Count);
		Count++;
	}
	else
	{
		Count = 0;
	}	

}
}

[Pavel 0]

...I did wonder if we were working on the same "Build version",

and so download the program this morning, and yes it was a different version!!

 

I would like to make a suggestion that a Build number be added to the download page.

I realise this will increase site traffic, but there must also be people just downloading

every day, just "in case" there is a new build available!

 

There is no need in build number as it does not change between versions and we releaseeach version only once.

 

 

Back to the problem:

 

I have added 2 C++ programs again to show the bug. (Both "without" Constructors)

 

One prog returns corrupt data, the other enters an infinite loop...

 

The workaround I ment was to initialize array outside of this class code like:

 

class Test T;
T.m_Buff[0] = 'A';
T.m_Buff[1] = 'B';
T.m_Buff[2] = 'C';

 

Regards,

Pavel

[Tim Barnes 0]

Hi Pavel,

 

I tried that and yes I can see the data in memory, and access it

outside the class, but the class members themselves, can't access it!

 

In fact the class members are accessing a completely

different section of memory, and will cause corruption

if used to try and change values of the variables.

 

***********

 

My mistake about build versions, I saw different modified

dates and assumed they were different. Obviously just a

feature of windows file system.

 

***************

 

Although I am a paid licence holder, If I were to pay for the

support option, would this allow me access to later build versions

such as a version with this class bug fixed??

 

Best Regards

Tim

[Pavel 0]

Although I am a paid licence holder, If I were to pay for the

support option, would this allow me access to later build versions

such as a version with this class bug fixed??

 

Not now. This is an interesting idea which we haven't thought about. Maybe we should adopt it.

 

Currently we supply beta builds to a small number of our customers (usually these are several very active compiler users) before public release. This time things are a bit different because in the coming release we plan to release BooctC++ commercially and it will use it's own protection mechanism (while now it uses same protection as BoostC). Because of these protection complications we probably will not release a beta to anybody this time.

 

Regards,

Pavel