如果一个枚举不能适用于整体类型，会发生什么？ [英] What happens if an enum cannot fit into an integral type?

问题描述

我发现了有关底层类型的这个问题的枚举，其中答案引用标准C ++ 7.2 / 5为：

枚举的底层类型是一个整数类型，可以代表所有在枚举中定义的枚举值。它是实现定义的，哪个整数类型被用作枚举的基础类型，除了底层类型不应大于int，除非加密器的值不能适用于int或unsigned int。

对于所有合理的情况，这是非常明确的。 但是，如果我使一个枚举太大，甚至不能适应长时间，会发生什么？

（我不知道为什么这会在实践中发生，但也许我感觉到破坏性，并有一个免费的下午）

这个行为是由标准定义的吗？ strong>

解决方案

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

类似的是未定义。

我通过强制类型为 int 而欺骗了一点，但同样适用于您平台上最大的整数类型。 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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