4

I want to build a "IThread" class which can hide the thread creation. Subclass implements the "ThreadMain" method and make it called automatically which seems like this:

class IThread
{
public:
    void BeginThread();
    virtual void ThreadMain(void *) PURE;
};
void IThread::BeginThread()
{
    //Error : cannot convert"std::binder1st<_Fn2>" to "void (__cdecl *)(void *)"
    m_ThreadHandle = _beginthread(
                     std::bind1st( std::mem_fun(&IThread::ThreadMain), this ),
                     m_StackSize, NULL);
    //Error : cannot convert void (__thiscall* )(void *) to void (__cdecl *)(void *)
      m_ThreadHandle = _beginthread(&IThread::ThreadMain, m_StackSize, NULL);
}

I have searched around and cannot figure it out. Is there anybody who did such thing? Or I am going the wrong way? TIA

Nickolas
  • 780
  • 8
  • 27

1 Answers1

4

You can't.

You should use a static function instead (not a static member function, but a free function).

// IThread.h
class IThread
{
public:
    void BeginThread();
    virtual void ThreadMain() = 0;
};

// IThread.cpp
extern "C"
{
    static void __cdecl IThreadBeginThreadHelper(void* userdata)
    {
        IThread* ithread = reinterpret_cast< IThread* >(userdata);
        ithread->ThreadMain();
    }
}
void IThread::BeginThread()
{
    m_ThreadHandle = _beginthread(
                     &IThreadBeginThreadHelper,
                     m_StackSize, reinterpret_cast< void* >(this));
}
Sylvain Defresne
  • 42,429
  • 12
  • 75
  • 85
  • A static member function won't work if you have a conformant compiler. _beginthread probably takes an extern "C" function, and a static member cannot have "C" linkage. (Of course, _beginthread is a Windows specific function, and VC++ doesn't take extern "C" into account, so you probably won't have any problems.) – James Kanze Mar 16 '11 at 14:00
  • I used a static function, not a static member function. They can have "C" linkage. In this situation, the difference between using or not `extern "C"` will probably just be a different name in the symbol table. I'll update my answer though. – Sylvain Defresne Mar 16 '11 at 14:06
  • @James: Pedantically, you are correct. But does it have any practical utility? Is there a compiler where C and C++ linkages are not compatible? – Maxim Egorushkin Mar 16 '11 at 14:21
  • @James Yes it works. Generally I use static member function and the std::bind for callback.I am not familiar with the global static method, and transmit "this" in this way teach me a lot. Thanks. – Nickolas Mar 16 '11 at 14:33