c++ - 枚举整数值的赋值规则是什么？

Question

假设我这样编码:

enum State{
    State0,                //=0
    State1,                //=1
    State2,                //=2
    State5 = State2+3,     //=5
    State6 = State5+1,     //=6
    StateSize = State6+1   //=7
};

我可以在多大程度上依赖事实(例如 StateSize==7)？

更具体地说，确定它们的值的 C++ 法律/规则是什么？

感觉SO里面可能有这个问题，但是没找到。

Answer 1

引自cppreference.com

If the first enumerator does not have an initializer, the associated value is zero. For any other enumerator whose definition does not have an initializer, the associated value is the value of the previous enumerator plus one.