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tesla1060
tesla1060

Reputation: 2765

c++ enum class must give all member a value or no value to ensure uniqueness?

enum class Status: char {
    test1 = '1',
    test2 = '10',
    test3
};

int main() {
    Status test1 = Status::test1;
    Status test2 = Status::test2;
    Status test3 = Status::test3;
    if (test1==test3) {
        cout << "Enum same"<< endl;
    }
    if (static_cast<char>(test1) == static_cast<char>(test3)) {
        cout << "value same" << endl;
    }
}

This snippet actually outputs,

Enum same
value same

That means if I mixed enum class member with set and unset, the compiler does not try to avoid giving the same value as other member? Apart from give a value to each member, any other way to ensure each member in enum class has different value?

Upvotes: 0

Views: 70

Answers (1)

Alan Birtles
Alan Birtles

Reputation: 36379

Due to the use of a multi character constant your code is probably (based on the observed behaviour, there is no guarantee that this will always be the case) equivalent to:

enum class Status: char {
    test1 = '1',
    test2 = '0',
    test3
};

As the value of test3 is not specified the compiler simply sets it to 1 more than the previous value, in this case it'll use '1'. There is no guarantee that enum elements with unspecified values will have a unique value.

See the documentation for more details.

Upvotes: 1

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