c++ - 如何将 void (__thiscall MyClass::* )(void *) 转换为 void (__cdecl *)(void *) 指针

Question

我想构建一个可以隐藏线程创建的“IThread”类。子类实现“ThreadMain”方法并使其自动调用，如下所示:

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);
}

找了半天也没弄明白。有没有人做过这样的事？还是我走错路了？时间差

Answer 1

你不能。

您应该改用静态函数(不是静态成员函数，而是自由函数)。

// 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));
}