基类子对象可以具有零大小。

Base class sub-objects may have zero size.

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不属于位域的两个对象可能拥有相同的地址（如果一个对象是另一个对象的子对象，或者至少有一个是空的基类子对象，并且他们的类型不同）； 否则，他们应该在不同的地址上。

Two objects that are not bit-fields may have the same address if one is a subobject of the other, or if at least one is a base class subobject of zero size and they are of different types;

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当构造、拷贝、赋值或撤销一个派生类对象时，也要构造、拷贝、赋值或撤销那些基类的子对象。

When we construct, copy, assign, or destroy an object of derived type, we also construct, copy, assign, or destroy those base-class subobjects.

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子对象多重继承自多个基类，每个基类都有虚函数，那么子类对象的内存布局是什么样的？

A function that is virtual in a base class is implicitly virtual in its derived classes. When a derived class overrides a virtual, the parameters in the base and derived classes must match exactly.

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子对象多重继承自多个基类，每个基类都有虚函数，那么子类对象的内存布局是什么样的？

A function that is virtual in a base class is implicitly virtual in its derived classes. When a derived class overrides a virtual, the parameters in the base and derived classes must match exactly.

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