Question

I got confused in C++ class definition. Can someone help me out?

I have the original template class defined as such:

template <typename T> 
struct SYNCHED_DATA{
    SYNCHED_DATA(int r)
    {
        var_R = r;
    }

    void set(T* pV)
    {
        var_T = *pV;
    }

    //...

private:
    //Copy constructor and assignments are NOT available!
    SYNCHED_DATA(const SYNCHED_DATA& s)
    {
    }
    SYNCHED_DATA& operator = (const SYNCHED_DATA& s)
    {
    }

    T var_T;
    int var_R;
};

and then I use it from another class:

struct THREADS_REPORT{
    THREADS_REPORT()     //error C2512: 'SYNCHED_DATA<T>' : no appropriate default constructor available
    {
    }

    void getReport(THREADS_REPORT_DATA* pOutReport)
    {
        //Retrieve report array
        sthrd.get(pOutReport);
    }
    void setReport(THREADS_REPORT_DATA* pReport)
    {
        //Set report array
        sthrd.set(pReport);
    }

private:
    SYNCHED_DATA<THREADS_REPORT_DATA> sthrd;

    //Copy constructor and assignments are NOT available!
    THREADS_REPORT(const THREADS_REPORT& s)   //error C2512: 'SYNCHED_DATA<T>' : no appropriate default constructor available
    {
    }
    THREADS_REPORT& operator = (const THREADS_REPORT& s)
    {
    }
};

But I get “error C2512” error at least in two spots in the second class (marked in the code above.) How do I need to change the second class to make it compile?

Answer 1

You should try initializing THREADS_REPORT::sthrd in the THREADS_REPORT constructor via the member initializer list:

 THREADS_REPORT(int i) : sthrd(i)
 {
 }

or provide a default constructor for SYNCHED_DATA:

SYNCHED_DATA() {}