在模板父类中调用子类函数的问题

下面这小段代码，可以编译执行，问题在注释里写的很清楚

#include "stdafx.h"
#include
using namespace std;

struct ISystemEventListener
{
public:
virtual void OnSystemEventAnyThread() {}
};

class INetMsgEvent
{
public:
virtual void OnNetMessage(void* pMsgHeader, void* pMsgData, void* pHandler) = 0;
};

template
class CNetMsgEventHandler:public INetMsgEvent
{
public:
typedef void (TNetEventHandler::*PEventHandler)(void* pMsgHeader, void* pMsgData);

inline TNetEventHandler* This()
{
    return dynamic_cast<TNetEventHandler*>(this);
}

template<typename TargetType, typename SourceType>
TargetType UnionCastType(SourceType src)
{
    union
    {
        TargetType TargetValue;
        SourceType SourceValue;
    }Convert;
    Convert.SourceValue =  src;
    return Convert.TargetValue;
}

virtual void OnNetMessage(void* pMsgHeader, void* pMsgData, void* pHandler)
{
    if (pMsgHeader && pMsgData && pHandler)
    {           
        PEventHandler pFunction = UnionCastType<PEventHandler>(pHandler);

        TNetEventHandler* pSystem = This();

        (pSystem->*pFunction)(pMsgHeader,pMsgData);     //如果继承了ISystemEventListener，那么这一句的汇编就多出好几句，导致ecx寄存器出错


        // 上面那一句，正确的时候，是下面这样的
        /*__asm
        {
        push        ecx
        push        edx
        mov         ecx,dword ptr [pMsgData] 
        push        ecx  
        mov         edx,dword ptr [pMsgHeader] 
        push        edx  

        mov         ecx,dword ptr [pSystem] 
        call        dword ptr [pFunction] 
        pop         edx
        pop         ecx
        }*/
    }
}

};

class A:public CNetMsgEventHandler,public ISystemEventListener //不继承ISystemEventListener的话，上面就是对的，继承了，就是错的
{
public:
int ia;
void func1(void* pMsgHeader, void* pMsgData);
};

void A::func1(void* pMsgHeader, void* pMsgData)
{
cout<<"A::func1"<<(int)pMsgHeader<<(int)pMsgData<<endl;
}

int _tmain(int argc, _TCHAR* argv[])
{
A a;

a.OnNetMessage((void*)333,(void*)333,(void*)333);

return 0;

}

父类想调用子类不是继承吧，是多态吧