How to free a dynamic array of CString?

Question

I have a dynamic array of CString in my class, I used new operator in constructor of my class to create that, so I wrote one line in destructor to free the memory. It doesn't cause any error but it leads to a breakpoint in runtime! Error is : Windows has triggered a breakpoint in Genetic Algorithm.exe.

This may be due to a corruption of the heap, which indicates a bug in Genetic Algorithm.exe or any of the DLLs it has loaded.

This may also be due to the user pressing F12 while Genetic Algorithm.exe has focus.

The output window may have more diagnostic information.

and the code is:

//in constructor
StringFormat = new CString[Info.VariablesCount + 1];
for (int i=0;i<=Info.VariablesCount;i++)
     StringFormat[i] = "%2.3f";`

// in destructor
free(StringFormat);

Notice that StringFormat* is a private member of class, I have some other dynamic arrays in this class too, but I can free them easily with free method, this problem is just with CString dynamic arrays, so what am I missing?

Answer 1

You have used new operator to allocate memory, and attempting to release the memory using free. Both have different heaps, other than some semantics they differ. You allocate using new, release memory using delete. Similarly, you allocate using malloc and release the same using free. You cannot mix them!

Also, as mentioned by others, if you use array-mode new (and not scaler new), you must delete it using array-mode delete and not scalar delete (i.e. delete[], and not delete).

It is very much recommended that you use vector, list, CArray, CStringArray or some other container to have array-of-strings, rather than managing it yourself.

Answer 2

You used new[] to allocate the CString array. You have to use delete[] to free it - Basic C++ memory rules.

In your destructor use: delete[] StringFormat;

Answer 3

Apart from deleting the string using delete[] StringFormat you need to follow the rule of three

• Provide a copy constructor
• provide an assignment overload function

check this.