recvmsg和recvit函数初始化各种数组和结构，将接收的数据从内核发送到进程。

The recvmsg and recvit functions initialize various arrays and structures to send the received data to the process from the kernel.

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动态分配数组时，如果数组元素具有类类型，将使用该类的默认构造函数（ 第2.3.4 节）实现初始化；

When we allocate an array of objects of a class type, then that type's default constructor ( Section 2.3.4, p. 50) is used to initialize each element.

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其中第一个数组是string类型，分配了保存对象的内存空间后，将调用string类型的默认构造函数依次初始化数组中的每个元素。

In the first case, those objects are strings. After allocating memory to hold the objects, the default string constructor is run on each element of the array in turn.

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