问题描述
c++ 中结构成员和类成员的默认值是什么，这些规则有何不同(例如，在类/结构/原语/等之间)?是否存在有关默认值的规则不同的情况?
What is the default values for members of a struct and members of a class in c++, and how do these rules differ (e.g. between classes/structs/primitives/etc) ? Are there circumstances where the rules about the default values differs ?
推荐答案
在 C++ 中，结构和类在这方面没有区别.它们都被称为类类型.
There are no differences between structs and classes in this regard in C++. They all are called just class types.
类类型的成员在一般情况下没有默认值.为了让一个类成员获得一个确定性的值，它必须被初始化，这可以通过
Members of class types have no default values in general case. In order to for a class member to get a deterministic value it has to be initialized, which can be done by
- 成员自身的默认构造函数
- 封闭类的构造函数初始化列表
- 为封闭类的对象显式指定初始化器(包括值初始化和使用聚合初始化器的初始化).
此外，所有具有静态存储持续时间的对象在程序启动时都被零初始化.
Additionally, all objects with static storage duration are zero-initialized at the program startup.
除了上述情况，类成员再次没有默认值，并且最初会包含不可预测的垃圾值.
Aside from the above cases, class members, once again, have no default values and will initially contain unpredictable garbage values.
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