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problem in delete in Debug mode

Hi experts,

I have a code, which generates an "invalid memory access" exception when I close my application. That is, I am getting exception when the destructor of my class is called.

In constructor, I am allocating (new) NO_OF_BUFFS amount of memory chunks. And in desctuctor, I am deleting these. I am not able to understand why I am getting exception everytime I delete.

**The exception occurs only in Debug mode, not it Release mode.**

I have also attached the code snippet for your reference:

Class Declaration:
----------------------
typedef unsigned char UINT8;
UINT8*      m_ppCBuffer[NO_OF_BUFFS];

Constructor:
----------------------
for(int i = 0; i < NO_OF_BUFFS;  i++)
{
      m_ppCBuffer[i] = new UINT8[BUFF_SIZE];
      if(!m_ppCBuffer[i])
      {
            MessageBox(NULL, TEXT("Not able to allocate enough memory"), NULL, NULL);
            break;
      }
      m_acBufferStatus[i] = READY_FOR_WRITE;
}

Desctructor:
----------------------
for(int i = 0;
i < NO_OF_BUFFS;
i++)
{
      if(m_ppCBuffer[i])
      {
            delete [] (m_ppCBuffer[i]);
            //delete (m_ppCBuffer[i]);
            m_ppCBuffer[i] = NULL;
      }
}

My doubt is, should I allocate memory for m_ppCBuffer also?

Thanks in advance,
Vikram_B.
0
Vikram_B
Asked:
Vikram_B
  • 4
1 Solution
 
rajeev_devinCommented:
>> In constructor, I am allocating (new) NO_OF_BUFFS amount of memory chunks. And in desctuctor, I am deleting
>> these. I am not able to understand why I am getting exception everytime I delete.
Somewhere in your code you are you are crossing the allocated size BUFF_SIZE.
0
 
rajeev_devinCommented:
In general, when you deallocate an allocated memory,
and if any crash comes it indicates that you are crossing the boundary of allocated space.
Please check the other part of your code.

I hope it helps.
0
 
Vikram_BAuthor Commented:

> Somewhere in your code you are you are crossing the allocated size BUFF_SIZE

But, I am getting that error only when deleting (in the destructor).
0
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rajeev_devinCommented:
I think you didn't get my point.
Check this code.

class testClass
{
      char* m_str;

public:
      testClass() {
            m_str = new char[1]; // Allocating
      }

      ~testClass() {
            delete [] m_str; // Deallocating. Will crash here.
      }

      void crossBoundary() {
            m_str[1] = 10; // Here I am crossing boundary.
      }
};

int main()
{
      testClass t;
      t.crossBoundary();
      return (0);
}
0
 
rajeev_devinCommented:
You can clearly see from the above code.
>> m_str = new char[1]; // Allocating
Allocated 1 char space here.

>> m_str[1] = 10;
Assigning value in the 2nd char which I didn't allocate.

Hope that helps.
0
 
SJT2003ACommented:
Simply remove the following line in your destructor.
Once after you delete the memory allocation, you can not assign a value though it is a NULL.

  m_ppCBuffer[i] = NULL;  // remove this line completely

Good luck :)
0

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