Methods for the smart pointer (smarter pointer) custom deletion (deleter) in C + +

The smart pointer contains two kinds of "shared_ptr" and "unique_ptr", because the two kinds of pointers are implemented differently, so the way to pass the deletion is different;

"shared_ptr" of the transfer of the deletion (deleter) way is relatively simple, only to add a specific name of the deletion function in the parameters, you can; Note is a single parameter function;

The "unique_ptr" is a function template (functions template), so you need to pass the type of the deletion in the template type (that is, function pointer), and then add a specific deletion in the parameter;

Defines the type of the function pointer, including three methods (typedef, typedef decltype, using), which can also be passed directly to the Decltype;

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Reference comments, the specific code is as follows:

* * * cppprimer.cpp * * Created on:2013.11.24 * author:caroline//*eclipse CDT, gcc 4.8.1*/  
      
#include <iostream> #include <memory> using namespace std;  
    void Deleter (int* ptr) {delete ptr;  
    ptr = nullptr;  
Std::clog << "shared_ptr Delete the pointer." << Std::endl;  
    int main (void) {//define function type typedef void (*TP) (int*);  
    typedef decltype (deleter) * DP;  
      
    Using up = void (*) (int*);  
    std::shared_ptr<int> SPI (new Int (a), deleter);  
    Std::shared_ptr<int> spi2 (new int, deleter);  
      
    Spi2 = std::make_shared<int> (15);  
    Std::cout << "*spi =" << *spi << Std::endl;  
      
    Std::cout << "*spi2 =" << *spi2 << Std::endl; Unique_ptr is the template function that requires the type of deletion (deleter), which is passed to the specific deletion std::unique_ptr<int, Decltype (Deleter) *> UPI (new int), deleter  
    ); Std::unique_ptr<inT, tp> upi2 (new int (), deleter);  
    Std::unique_ptr<int, dp> upi3 (new int (), deleter);  
      
    Std::unique_ptr<int, up> upi4 (new int (), deleter);  
    Std::cout << "*upi =" << *upi << Std::endl;  
    Std::cout << "*upi2 =" << *upi2 << Std::endl;  
    Std::cout << "*upi3 =" << *upi3 << Std::endl;  
      
    Std::cout << "*upi4 =" << *upi4 << Std::endl;  
      
return 0; }

Output:

shared_ptr deletes the pointer.  
shared_ptr deletes the pointer.  
shared_ptr deletes the pointer.  
shared_ptr deletes the pointer.  
shared_ptr deletes the pointer.  
shared_ptr deletes the pointer.  
*spi =  
*spi2 =  
*upi =  
*upi2 =  
*upi3 =  
35

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