用c++中的重新解释强制转换扩展嵌套宏

我偶然发现了下面的代码，并发现理解其中的嵌套宏和类型转换非常复杂。

此外，当我试图编译代码时，我遇到了一个错误

需要对以下代码进行解释。

为什么在Motor.h中将BEGIN_STATE_MAP和END_STATE_MAP设置为标签，这对我来说真的很新鲜

提前感谢

Motor.h

// the Motor state machine class
class Motor : public StateMachine
{
public:
    Motor() : StateMachine(ST_MAX_STATES) {}
    // external events taken by this state machine
    void Halt();
    void SetSpeed(MotorData*);
private:
    // state machine state functions
    void ST_Idle();
    void ST_Stop();
    void ST_Start(MotorData*);
    void ST_ChangeSpeed(MotorData*);
    // state map to define state function order
    BEGIN_STATE_MAP
        STATE_MAP_ENTRY(ST_Idle)
        STATE_MAP_ENTRY(ST_Stop)
        STATE_MAP_ENTRY(ST_Start)
        STATE_MAP_ENTRY(ST_ChangeSpeed)
    END_STATE_MAP
    // state enumeration order must match the order of state
    // method entries in the state map
    enum E_States {
        ST_IDLE = 0,
        ST_STOP,
        ST_START,
        ST_CHANGE_SPEED,
        ST_MAX_STATES
    };
};
#endif //MOTOR_H

什么是BEGIN_STATE_MAP和END_STATE_MAP，我发现这个定义真的很新，BEGIN_STATE_MAP和END_STATE_MAP是在下面的头文件中定义的宏。

StateMachine.h

#ifndef STATE_MACHINE_H
#define STATE_MACHINE_H
#include <stdio.h>
#include "EventData.h"
struct StateStruct;
// base class for state machines
class StateMachine
{
public:
    StateMachine(int maxStates);
    virtual ~StateMachine() {}
protected:
    enum { EVENT_IGNORED = 0xFE, CANNOT_HAPPEN };
    unsigned char currentState;
    void ExternalEvent(unsigned char, EventData* = NULL);
    void InternalEvent(unsigned char, EventData* = NULL);
    virtual const StateStruct* GetStateMap() = 0;
private:
    const int _maxStates;
    bool _eventGenerated;
    EventData* _pEventData;
    void StateEngine(void);
};
typedef void (StateMachine::*StateFunc)(EventData *);
struct StateStruct
{
    StateFunc pStateFunc;
};
#define BEGIN_STATE_MAP 
public:
const StateStruct* GetStateMap() {
    static const StateStruct StateMap[] = {
#define STATE_MAP_ENTRY(entry)
    { reinterpret_cast<StateFunc>(entry) },
#define END_STATE_MAP 
    { reinterpret_cast<StateFunc>(NULL) }
    }; 
    return &StateMap[0]; }
#define BEGIN_TRANSITION_MAP 
    static const unsigned char TRANSITIONS[] = {
#define TRANSITION_MAP_ENTRY(entry)
    entry,
#define END_TRANSITION_MAP(data) 
    0 };
    ExternalEvent(TRANSITIONS[currentState], data);
#endif

EventData.h

#ifndef EVENT_DATA_H
#define EVENT_DATA_H
class EventData
{
public:
   virtual ~EventData() {};
};
#endif //EVENT_DATA_H

当我试图编译上面的代码时。以下是遇到的错误

错误

-------------- Build: Debug in StateMachine (compiler: GNU GCC Compiler)---------------
mingw32-g++.exe -Wall -fexceptions -g -pedantic -Wzero-as-null-pointer-constant -std=c++0x -Wextra -Wall  -c C:Usersxprk569StateMachinemain.cpp -o objDebugmain.o
In file included from C:Usersxprk569StateMachinemain.cpp:2:0:
C:Usersxprk569StateMachineMotor.h: In member function 'virtual const StateStruct* Motor::GetStateMap()':
C:Usersxprk569StateMachineStateMachine.h:40:40: error: invalid use of member (did you forget the '&' ?)
     { reinterpret_cast<StateFunc>(entry) },
                                        ^
C:Usersxprk569StateMachineMotor.h:29:9: note: in expansion of macro 'STATE_MAP_ENTRY'
         STATE_MAP_ENTRY(ST_Idle)
         ^
C:Usersxprk569StateMachineStateMachine.h:40:40: error: invalid use of member (did you forget the '&' ?)
     { reinterpret_cast<StateFunc>(entry) },
                                        ^
C:Usersxprk569StateMachineMotor.h:30:9: note: in expansion of macro 'STATE_MAP_ENTRY'
         STATE_MAP_ENTRY(ST_Stop)
         ^
C:Usersxprk569StateMachineStateMachine.h:40:40: error: invalid use of member (did you forget the '&' ?)
     { reinterpret_cast<StateFunc>(entry) },
                                        ^
C:Usersxprk569StateMachineMotor.h:31:9: note: in expansion of macro 'STATE_MAP_ENTRY'
         STATE_MAP_ENTRY(ST_Start)
         ^
C:Usersxprk569StateMachineStateMachine.h:40:40: error: invalid use of member (did you forget the '&' ?)
     { reinterpret_cast<StateFunc>(entry) },
                                        ^
C:Usersxprk569StateMachineMotor.h:32:9: note: in expansion of macro 'STATE_MAP_ENTRY'
         STATE_MAP_ENTRY(ST_ChangeSpeed)
         ^
C:Usersxprk569StateMachineStateMachine.h:43:39: error: invalid cast from type 'int' to type 'StateFunc {aka void (StateMachine::*)(EventData*)}'
     { reinterpret_cast<StateFunc>(NULL) }
                                       ^
C:Usersxprk569StateMachineMotor.h:33:5: note: in expansion of macro 'END_STATE_MAP'
     END_STATE_MAP
     ^
Process terminated with status 1 (0 minute(s), 0 second(s))
5 error(s), 0 warning(s) (0 minute(s), 0 second(s))

有人能解释一下为什么Motor.h中的宏是这样写的吗，为什么它在StateMachine.h中是这样声明的，以及为什么抛出错误？

提前感谢