c++ - 这是(枚举 : char {}) a gcc bug?

Question

在 gcc-4.5 下打印 0，在 gcc-4.6 下打印 1。

#include <iostream>

enum VenueId: char {}; 
int
main (int argc, char ** argv)
{
  VenueId v = (VenueId)'P';
  std::cout << (v=='P') << std::endl;
  return 0;
}

Answer 1

根据标准，VenuedId 具有 char 类型作为基础类型，因此 v 应包含 char 'P'，v == 'P' 应该产生 true。

§ 7.2 枚举声明

Each enumeration defines a type that is different from all other types. Each enumeration also has an underlying type. The underlying type can be explicitly specified using enum-base; if not explicitly specified, the underlying type of a scoped enumeration type is int. In these cases, the underlying type is said to be fixed. Following the closing brace of an num-specifier, each enumerator has the type of its enumeration.