CODEWITHSUNDEEP
c++stringclasstemplatesmemory
Jason
Jason

Reputation: 1

My Dynamic Array template class is doing weird things

The code

I'm having a problem with it handling strings. Whenever I try a string, I get a lovely little error code:

Unhandled exception at 0x77e815de in arraytest.exe: 0xC0000005: 
Access violation reading location 0xabababab.

It handles int, double, and char just fine. I also tried the exact same test string I was using (the alphabet) as a char* and it did that fine too. It just pukes on strings, for a reason that I cannot quite fathom. I really don't know where to go with it next. Any suggestions?

Upvotes: 0

Views: 302

Answers (1)

Bo Persson
Bo Persson

Reputation: 92311

You have a problem with your reallocation code in push_back

template<class type>
void DynamicArray<type>::push_back(type newValue)
{
        ++_size;   // <=== **

        if (_size > _capacity) // If size larger than capacity
        {
                _capacity *= CAPACITY_MULT; // double capacity
                type* tempArray = new type[_capacity];// Create temporary array with new capacity
                // Copy array values into temporary array

                for (int i = 0; i < _size; i++)    // <=== **
                {
                        tempArray[i] = dynArray[i];
                }
                // Delete dynArray
                delete[] dynArray;
                // Insert new value at end of temporary array
                // Set dynArray to temporary array
                dynArray = tempArray;
        }

        dynArray[_size - 1] = newValue;
}

You start by increasing the size of the current container before checking if there is room for the new element. Then you use the new size when copying the old values to a new array.

This might seem to work for primitive types, but a std::string will try to copy its own internal data (which isn't there) and liklely cause an access violation.

Upvotes: 3

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