在派生类中调用基类副本构造函数

Question

Just to preface, I did a lot of reading before posting because I know this is probably a very basic question, but I'm still missing something, so sorry in advance if I did...

I have a template derived class based upon another class:

  class BaseBuffer
  {
    public:
    // Constructor
    BaseBuffer() {};
    BaseBuffer(long buf_size);
    BaseBuffer(const BaseBuffer& orig);
....
  template <class T>
  class DataBuffer : public BaseBuffer
  {
....

I am implementing the copy constructor for DataBuffer . I have already written the copy constructor for BaseBuffer as shown above.

Now, as I understand, to call the copy of BaseBuffer as DataBuffer is being copied, I must do

    DataBuffer(const DataBuffer& orig) : BaseBuffer(orig)
    {
      // Initialize an array of memory given the type
      buf_ = new T[size_];
      ....

where BaseBuffer(orig) should, as another SO answer states, "This calls the Base copy constructor on the Base sub-object."

When I DON'T do this, then the expected bad thing happens: all the properties which belong to BaseBuffer do not get copied.

When I DO do this, unexpected bad thing happens: I get an EXC_BAD_ACCESS when the code gets to the point of calling BaseBuffer(orig) .

So this kinda does and doesn't make sense to me. As DataBuffer is inherited from BaseBuffer , it makes sense that I could call the BaseBuffer copy constructor and it would only "look" in the memory locations it knows about, and all the DataBuffer extra stuff "fits" around the base.

But on the other hand, it seems to make sense that strictly speaking, calling BaseBuffer(&<DataBuffer>) doesn't make sense because I have only defined BaseBuffer(&<BaseBuffer>) .

So my question has two parts,

1. Why is this "correct" DataBuffer(const DataBuffer& orig) : BaseBuffer(orig) {...} syntax (and if it's not, sorry)?
2. How do I prevent the EXC_BAD_ACCESS?

Thank you in advance.

Answer 1

Bottom line: I made a mistake.

As everyone stated, the syntax

DataBuffer(const DataBuffer& orig) : BaseBuffer(orig) {...}

is correct, and the error was elsewhere in my code. In my case, I was trying to copy the object before it had been initialized. Sorry for wasting everyone's time.