入侵SmartPointer的实现

Question

下面是我的SmartPointer实现。它是侵扰性的和微小的。我该如何改进呢？

例如，constexpr、nonexcept、try-catch-throw等。

smartpointer.h

/* 
* file name : smartpointer.h
*/
#ifndef __SMARTPOINTER_H__
#define __SMARTPOINTER_H__

#define COMPARE(_op_)                                           \
bool operator _op_ (const SmartPointer& o) const {              \
    return mPointer _op_ o.mPointer;                            \
}                                                               \
bool operator _op_ (const T* o) const {                         \
    return mPointer _op_ o;                                     \
} 

template <typename T> 
class SmartPointer {
public:
    SmartPointer():mPointer(NULL) {std::cout <<"Create null smart pointer."<< std::endl;}   
    SmartPointer(T *p):mPointer(p) {
        std::cout <<"Create smart pointer at "<<static_cast<const void*>(p)<<std::endl;
        if (mPointer) mPointer->incRefCount();
    }     
    ~SmartPointer(){
        std::cout << "Release smart pointer at "<<static_cast<const void*>(mPointer)<<std::endl;
        if (mPointer && mPointer->decRefCount()==0) delete mPointer;
    }
    SmartPointer(const SmartPointer &other):mPointer(other.mPointer) {
        std::cout <<"Copy smart pointer at "<<static_cast<const void*>(other.mPointer)<<std::endl;
       if(mPointer) mPointer->incRefCount();
    }             
   SmartPointer &operator = (const SmartPointer &other) {
       T *temp(other.mPointer);
       if (temp) temp->incRefCount();
       if (mPointer && mPointer->decRefCount()==0) delete mPointer;
       mPointer = temp;  
       return *this;
   } 

    T&  operator* () const {return *mPointer;}
    T* operator-> () const {return mPointer;}


    COMPARE(==);
    COMPARE(!=);
private:
    T *mPointer;
};

class RefBase   
{   
    public:   
        RefBase() : mCount(0){ }   
        void incRefCount(){   
            mCount++;   
        }   
        int decRefCount(){   
            return --mCount;
        }      
        int getRefCount() const {   
            return mCount;   
        }  

        virtual ~RefBase(){};
    private:   
        int mCount;   
};   
#endif // __SMARTPOINTER_H__

sptestcase4.cpp (测试用例)

/* 
* file name : sptestcase4.cpp
*/

#include <iostream>
#include "smartpointer.h"

class SomeClass: public RefBase{
public:
    SomeClass(){std::cout << "SomeClass default constructor !"<<std::endl;}
    ~SomeClass(){std::cout << "SomeClass deconstructor !"<<std::endl;}
    void func(){std::cout << "SomeClass func()" <<std::endl;}
};

class OtherClass: public RefBase{
public:
    OtherClass(){std::cout << "OtherClass default constructor !"<<std::endl;}
    ~OtherClass(){std::cout << "OtherClass deconstructor !"<<std::endl;}
    void foo(){std::cout << "OtherClass foo()" <<std::endl;}
};


void testcase4_1(void)
{
    std::cout << "=======testcase4_1=========" <<std::endl;
    SmartPointer<SomeClass> spsomeclass = new SomeClass();
    (*spsomeclass).func();
    spsomeclass->func();
    std::cout << "==========================" <<std::endl;
}

void testcase4_2(void)
{
    std::cout << "=======testcase4_2=========" <<std::endl;
    SomeClass *psomeclass = new SomeClass();
    SmartPointer<SomeClass> spsomeclass = psomeclass;

    SmartPointer<OtherClass> spotherclass = new OtherClass();
    SmartPointer<OtherClass> spotherclass2 = spotherclass;

    if (spsomeclass == NULL) std::cout<< "spsomeclass is NULL pointer" << std::endl;
    if (spotherclass != NULL) std::cout<< "spotherclass is not NULL pointer" << std::endl;
    if (spsomeclass == psomeclass)  
       std::cout<< "spsomeclass and psomeclass are same pointer" << std::endl;
    if (spsomeclass != psomeclass)  
       std::cout<< "spsomeclass and psomeclass are not same pointer" << std::endl;
//     if (spsomeclass != spotherclass) // ERROR !
//        std::cout<< "spsomeclass and spotherclass are not same pointer" << std::endl;
//     if (spsomeclass == spotherclass) // ERROR !
//        std::cout<< "spsomeclass and spotherclass are same pointer" << std::endl;
    if (spotherclass == spotherclass2) std::cout<< "spotherclass and spotherclass2 are same pointer" << std::endl;
    if (spotherclass != spotherclass2) std::cout<< "spotherclass and spotherclass2 are not same pointer" << std::endl;    
    std::cout << "==========================" <<std::endl;

}

int main(void)
{
    testcase4_1();
    testcase4_2();
    return 0;
}

Answer 1

通过使用以下划线开头的标识符，您将调用未定义的行为。只要去掉下划线。

在头文件的末尾，您应该取消对比较宏的定义。或者至少考虑完全删除宏。

&的位置不一致。

您的头文件必须自己编译，即使它是在<iostream>之前包含的。