Geek asks and answers

Is it possible to place std :: array <POD, N> in a union?

I have a union declared this way:

union
{
    int all[4];
    struct
    {
        int a, b, c, d;
    };
};

An array point allsimply simplifies iteration over 4 fields.

To make this even easier, I would like to replace it with std::array<int, 4>. Will this show me nasal demons ?

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1 answer

First, it’s important to note that simply having two objects in a union is never undefined. What undefined is to write to one and read from the other, with one exception:

[C++11: 9.5/1]: [. : , (9.2), , ; . 9.2. -end note] [..]

, -, std::array , , , :

[C++11: 23.3.2.1/2]: - (8.5.1), :

    array<T, N> a = { };

, , N , T.

, , .

: ; .

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