如果枚举不能适合整数类型，会发生什么？ [英] What happens if an enum cannot fit into an integral type?

问题描述

我遇到了关于底层类型的此问题的枚举，其中答案标准C ++ 7.2 / 5如下：

枚举的基础类型是一个整数类型，在枚举中定义的枚举值。它是实现定义的，哪个整数类型用作枚举的基本类型，除非底层类型不能大于int，除非枚举器的值不能适合int或unsigned int。

这在所有合理情况下都很清楚。 但是，如果我将枚举设置得如此可笑，甚至不能适应长时间，会发生什么？

）

这个行为是否由标准定义？

strong>

解决方案

的行为

  enum foo：int 
 {
 bar = INT_MAX，
 oops 
}; 
  

且类似未定义。

我通过将类型强制为 int 来欺骗了一下，但这同样适用于您平台上可用的最大整数类型。 p>

I came across this question about the underlying types of enums, where an answers quotes Standard C++ 7.2/5 as:

The underlying type of an enumeration is an integral type that can represent all the enumerator values defined in the enumeration. It is implementation-defined which integral type is used as the underlying type for an enumeration except that the underlying type shall not be larger than int unless the value of an enu- merator cannot fit in an int or unsigned int.

This is pretty clear for all reasonable cases. But what happens if I make an enum so ridiculously large that it can't even fit in a long long?

(I don't know why this would ever happen in practice, but maybe I'm feeling destructive and have a free afternoon)

Is this behavior defined by the standard?

解决方案

The behaviour of

enum foo : int
{
    bar = INT_MAX,
    oops
};

and similar is undefined.

I've cheated a little here by forcing the type to an int, but the same applies to the largest integral type available on your platform.

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