13.13

2019-11-14 10:12:20

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供稿：網(wǎng)友

13.9 類里前面帶~的函數(shù)，析構(gòu)函數(shù)用來(lái)銷毀對(duì)象釋放資源，當(dāng)沒(méi)有定義自己的析構(gòu)函數(shù)的時(shí)候編譯器會(huì)自己定義合成析構(gòu)函數(shù)。

13.10 智能指針的計(jì)時(shí)器會(huì)變?yōu)?，然后會(huì)釋放智能指針指向的內(nèi)存，然后銷毀對(duì)象。銷毀對(duì)象，但是指針指向的內(nèi)存不會(huì)被釋放，因?yàn)槭莣eak_ptr

13.11

#include <string>class Hasptr {public: HasPtr(const std::string &s = std::string()) : ps(new std::string(s)), i(0) { } HasPtr(const HasPtr& hp) : ps(new std::string(*hp.ps)), i(hp.i) { } HasPtr& Operator=(const HasPtr& rhs){ if(this=&rhs) return this; delete ps; ps=new string (*rhs.ps); i=rhs.i; return *this; } ~HasPtr(){ delete ps; }PRivate: std::string *ps; int i;};

13.12 3次，離開(kāi)函數(shù)的時(shí)候，accum，item1，item2會(huì)被析構(gòu)。

13.13 @pezy

#include <iostream>#include <vector>#include <initializer_list>struct X { X() { std::cout << "X()" << std::endl; } X(const X&) { std::cout << "X(const X&)" << std::endl; } X& operator=(const X&) { std::cout << "X& operator=(const X&)" << std::endl; return *this; } ~X() { std::cout << "~X()" << std::endl; }};void f(const X &rx, X x){ std::vector<X> vec; vec.reserve(2); vec.push_back(rx); vec.push_back(x);}int main(){ X *px = new X; f(*px, *px); delete px; return 0;}

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