Access Violation Message on Deleting Dynamically created two dimensional array

Question

I am trying to allocate a two dimensional array dynamically and then after use, delete it. The code looks something like this:

func(char* pszError)
{

    //Initialize

    char ** ptr = new char*[1];

    // Some copying stuff in ptr[0]
    ptr[0] = new char[strlen(psError) + 1];
    strcpy(ptr[0], strlen(pszError) + 1, pszError); 

    delete[] ptr[0];

    delete[] ptr;

    return;

}

This looked harmless to me and shouldnt have given error. However, at the point delete[] ptr; its throwing me access violation.

Can anyone help me. I have done enough head banging on this.

The error is in the "some copying stuff". Possibly writes outside the allocated space. — Bo Persson
– Bo Persson, Commented Jul 5, 2011 at 10:23
Show us the "copying stuff" code part, I think the problem will be there. — twoflower
– twoflower, Commented Jul 5, 2011 at 10:23
This code fragment is correct. What is happening in "Some copying stuff in ptr[0]"? Maybe you are (a) explicitly altering the value of ptr[0] or (b) implicitly changing the value of ptr[0] by accidently reaching out of bounds of ptr[0][]. (those two arrays will most likely "sit" next to each other on the heap). — CygnusX1
– CygnusX1, Commented Jul 5, 2011 at 10:25
ptr[0]=new char[10]; ptr[0] = new char[strlen(psError) + 1]; -> at least memory leak... — Naszta
– Naszta, Commented Jul 5, 2011 at 11:03

James Johnston · Accepted Answer · 2011-07-05 13:47:25Z

The error lies with these lines:

ptr[0] = new char[strlen(psError) + 1];
strcpy(ptr[0], strlen(pszError) + 1, pszError);

Everything else looks correct to me. But the code shouldn't even compile with these errors. Some points to consider:

strcpy does not take 3 parameters. This code shouldn't even compile. This might mean one of the following:
- You have a typo, and meant to use strncpy. If this is the case, then your 2nd and 3rd parameters are backwards which would cause the access violation.
- You have overloaded the strcpy function with your own function that accepts 3 parameters. Please post the code for it if this is the case. It's probably better for you to use strncpy though.
"strlen(psError)" shouldn't compile either (missing a "z"). I assume you meant pszError, but if you have a global variable named psError then the incorrect amount of memory is probably being allocated.
If pszError is a bad pointer or isn't probably null-terminated, then the code would obviously crash.

See http://linux.die.net/man/3/strcpy for proper strcpy & strncpy parameters.

Andy_MSFT · Accepted Answer · 2011-08-01 12:36:34Z

0

thanks for the help! We found the issue was as pointed by some of you, in the allocation. So, we should have checked after allocation if the pointer returned was proper. It never compalined while we did copy/etc. However, when the distructer tried to free the memory, it gave access violation then.

Regards,

Andy

answered Aug 1, 2011 at 12:36

Andy_MSFT

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