c - c语言中枚举字段有默认值吗

Question

我正在某处阅读c代码，我发现了这个结构

typedef enum
{
  SPIIP_0,
  SPIIP_1,
  NUMBER_OF_SPIIP,
  ERROR_SPIIP
}SPIIP_ID_E;

在我的代码的其他地方我发现了语句:if(IP>NUMBER_OF_SPIIP) 但 NUMBER_OF_SPIIP 值未在任何地方声明

我的问题是:deos 枚举类型为其元素定义值

Answer 1

是的，确实如此。根据 C11 标准，第 §6.7.2.2 章，枚举说明符，第 3 段(强调我的)

The identifiers in an enumerator list are declared as constants that have type int and may appear wherever such are permitted.¹²⁷⁾ An enumerator with = defines its enumeration constant as the value of the constant expression. If the first enumerator has no =, the value of its enumeration constant is 0. Each subsequent enumerator with no = defines its enumeration constant as the value of the constant expression obtained by adding 1 to the value of the previous enumeration constant. (The use of enumerators with = may produce enumeration constants with values that duplicate other values in the same enumeration.) The enumerators of an enumeration are also known as its members.

因此，在您的情况下，NUMBER_OF_SPIIP 的值为 2。