c++ - 如何在复制控制函数中处理 C++ 数组成员？

Question

这是我想了很久的事情。举个例子:

struct matrix
{
    float data[16];
};

我知道默认构造函数和析构函数在这个特定示例中做了什么(什么都不知道)，但是复制构造函数和复制赋值运算符呢？

struct matrix
{
    float data[16];

    // automatically generated copy constructor
    matrix(const matrix& that) : // What happens here?
    {
        // (or here?)
    }

    // automatically generated copy assignment operator
    matrix& operator=(const matrix& that)
    {
        // What happens here?

        return *this;
    }
};

它是否涉及 std::copy 或 std::uninitialized_copy 或 memcpy 或 memmove 或什么？

Answer 1

这是标准在 12.8(复制类对象)中所说的。复制构造:

Each subobject is copied in the manner appropriate to its type:

• if the subobject is of class type, the copy constructor for the class is used;
• if the subobject is an array, each element is copied, in the manner appropriate to the element type;
• if the subobject is of scalar type, the built-in assignment operator is used.

复制作业:

Each subobject is assigned in the manner appropriate to its type:

• if the subobject is of class type, the copy assignment operator for the class is used (as if by explicit qualification; that is, ignoring any possible virtual overriding functions in more derived classes);
• if the subobject is an array, each element is assigned, in the manner appropriate to the element type;
• if the subobject is of scalar type, the built-in assignment operator is used.