C / C ++-通过作为结构一部分的值数组进行复制

Question

consider the following C++ struct:

typedef struct Person {
    std::string name;
    std::string children[MAX_NUM_CHILDREN];
} Person;

The question is, what happens in the following scenario:

void do_something(const Person& p) {
    Person person_copy = p;
}

The question is whether the children array of p , which is actually a member of type std::string* , is going to be copied as a pointer, or is every string in the children array going to be copied by value using the copy constructor?

Answer 1

[...] the children array of p , which is actually a member of type std::string* [...]

children is an array of MAX_NUM_CHILDREN strings, not a pointer. All of its elements will be copied over to person_copy.children by Person 's copy constructor.

Answer 2

I don't think there the array will decay in this example so the content will be copied.

T[] and T* are different but T[] can decay to T* (you can look for the array decaying rules).

Your Person struct should be declared like that:

struct Person {
    std::string name;
    std::string children[MAX_NUM_CHILDREN];
};

That's shorter and that's the C++ way.

BTW, the copy constructor will be called because this is an assignment initialisation but it's better use the Person p(p2); (or Person p{p2} with C++11 compatible compiler) initialisation form.