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item18: smart pointer
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4.SmartPointers/item18.md
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# CHAPTER 4 Smart Pointers
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诗人和歌曲作家喜欢爱。有时候喜欢计数。很少情况下两者兼有。受伊丽莎白·巴雷特·勃朗宁（Elizabeth Barrett Browning）对爱和数的不同看法的启发（“我怎么爱你？”让我数一数。”）和保罗·西蒙（Paul Simon）（“离开你的爱人必须有50种方法。”），我们可以试着枚举一些为什么原始指针很难被爱的原因：
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1. 它的声明不能指示所指到底是单个对象还是数组
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2. 它的声明没有告诉你用完后是否应该销毁它，即指针是否拥有所指之物
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3. 如果你决定你应该销毁对象所指，没人告诉你该用delete还是其他析构机制（比如将指针传给专门的销毁函数）
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4. 如果你发现该用delete。 原因1说了不知道是delete单个对象还是delete数组。如果用错了结果是未定义的
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5. 假设你确定了指针所指，知道销毁机制，也很难确定你在所有执行路径上都执行了销毁操作（包括异常产生后的路径）。少一条路径就会产生资源泄漏，销毁多次还会导致未定义行为
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6. 一般来说没有办法告诉你指针是否变成了悬空指针（dangling pointers），即内存中不再存在指针所指之物。悬空指针会在对象销毁后仍然指向它们。
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原始指针是强大的工具，当然，另一方面几十年的经验证明，只要注意力稍有疏忽，这个强大的工具就会攻击它的主人。
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智能指针是解决这些问题的一种办法。智能指针包裹原始指针，它们的行为看起来像被包裹的原始指针，但避免了原始指针的很多陷阱。你应该更倾向于只能指针而不是原始指针。几乎原始指针能做的所有事情智能指针都能做，而且出错的机会更少。
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## Item 18:对于独占资源使用std::unique_ptr
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条款十八:对于独占资源使用std::unique_ptr
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README.md
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README.md
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# 《Effective Modern C++ 》翻译
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[](#backers)
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[](#sponsors)
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@ -11,27 +11,27 @@
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# 目录
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1. 类型推导
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1. [Item 1:理解模板类型推导](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/1.DeducingTypes/item1.md) __已修订__
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2. [Item 2:理解auto类型推导](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/1.DeducingTypes/item2.md)
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3. [Item 3:理解decltype](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/1.DeducingTypes/item3.md)
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3. [Item 4:学会查看类型推导结果](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/1.DeducingTypes/item4.md)
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1. [Item 1:理解模板类型推导](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/1.DeducingTypes/item1.md) __已修订__
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2. [Item 2:理解auto类型推导](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/1.DeducingTypes/item2.md)
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3. [Item 3:理解decltype](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/1.DeducingTypes/item3.md)
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3. [Item 4:学会查看类型推导结果](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/1.DeducingTypes/item4.md)
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2. auto
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1. [Item 5:优先考虑auto而非显式类型声明](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/2.auto/item5.md)
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2. [Item 6:auto推导若非己愿，使用显式类型初始化惯用法](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/2.auto/item6.md)
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1. [Item 5:优先考虑auto而非显式类型声明](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/2.auto/item5.md)
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2. [Item 6:auto推导若非己愿，使用显式类型初始化惯用法](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/2.auto/item6.md)
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3. 移步现代C++
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1. [Item 7:区别使用()和{}创建对象](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item7.md)
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2. [Item 8:优先考虑nullptr而非0和NULL](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item8.md)
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3. [Item 9:优先考虑别名声明而非typedefs](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item9.md)
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4. [Item 10:优先考虑限域枚举而非未限域枚举](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item10.md) __已修订__
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5. [Item 11:优先考虑使用deleted函数而非使用未定义的私有声明](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item11.md)
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6. [Item 12:使用override声明重载函数](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item12.md)
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7. [Item 13:优先考虑const_iterator而非iterator](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item13.md)
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8. [Item 14:如果函数不抛出异常请使用noexcept](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item14.md)
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9. [Item 15:尽可能的使用constexpr](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item15.md)
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10. [Item 16:让const成员函数线程安全](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item16.md) __由 @windski贡献__
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11. [Item 17:理解特殊成员函数函数的生成](https://github.com/racaljk/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item17.md) __更新中__
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1. [Item 7:区别使用()和{}创建对象](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item7.md)
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2. [Item 8:优先考虑nullptr而非0和NULL](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item8.md)
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3. [Item 9:优先考虑别名声明而非typedefs](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item9.md)
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4. [Item 10:优先考虑限域枚举而非未限域枚举](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item10.md) __已修订__
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5. [Item 11:优先考虑使用deleted函数而非使用未定义的私有声明](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item11.md)
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6. [Item 12:使用override声明重载函数](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item12.md)
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7. [Item 13:优先考虑const_iterator而非iterator](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item13.md)
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8. [Item 14:如果函数不抛出异常请使用noexcept](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item14.md)
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9. [Item 15:尽可能的使用constexpr](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item15.md)
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10. [Item 16:让const成员函数线程安全](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item16.md) __由 @windski贡献__
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11. [Item 17:理解特殊成员函数函数的生成](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/3.MovingToModernCpp/item17.md)
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4. 智能指针
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1. Item 18:对于占有性资源使用std::unique_ptr
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1. [Item 18:对于独占资源使用std::unique_ptr](https://github.com/kelthuzadx/EffectiveModernCppChinese/blob/master/4.SmartPointers/item18.md) __更新中__
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2. Item 19:对于共享性资源使用std::shared_ptr
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3. Item 20:对于类似于std::shared_ptr的指针使用std::weak_ptr可能造成悬置
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4. Item 21:优先考虑使用std::make_unique和std::make_shared而非new
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@ -64,7 +64,7 @@
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## 贡献者
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感谢所有参与翻译/勘误/建议的贡献者们~
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<a href="https://github.com/racaljk/EffectiveModernCppChinese/graphs/contributors"><img src="https://opencollective.com/EffectiveModernCppChinese/contributors.svg?width=890&button=false" /></a>
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<a href="https://github.com/kelthuzadx/EffectiveModernCppChinese/graphs/contributors"><img src="https://opencollective.com/EffectiveModernCppChinese/contributors.svg?width=890&button=false" /></a>
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## 赞助翻译
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