c++ - 初始化结构 union

Question

struct EXMPL
{
  union
  {
    struct
    {
      struct 
      {
        uint8_t AA;
        uint8_t BB;
        uint8_t CC;
        uint8_t DD;
      }Rev;

      struct
      {
        uint8_t XX;
        uint8_t VV;
        uint8_t WW;
        uint8_t FF;
      }IDs;
    };

    struct UNN
    {
      uint32_t A;
      uint32_t B; 
    };
  };
};

当我尝试像这样初始化它时:

EXMPL aStruct = {{ 0x00, 0x00, 0x01, 0x00 }, { 0x00, 0x00, 0x00, 0x00 }};

我收到“太多初始化值”错误。任何帮助将不胜感激，谢谢。

Answer 1

在 C 中，EXMPL aStruct = {{... 需要是 struct EXMPL aStruct = {{...

缺少 2 级 {{ - 添加了

int main(void) {
  struct EXMPL  // level 1
  {
    union  // level 2
    {
      struct // level 3
      {
        struct  // level 4
        {
          uint8_t AA;
          uint8_t BB;
          uint8_t CC;
          uint8_t DD;
        }Rev;

        struct
        {
          uint8_t XX;
          uint8_t VV;
          uint8_t WW;
          uint8_t FF;
        }IDs;
      } ;

      // level 3 
      // but irrelevant to initialization as only 1st union member counts by default
      struct UNN  
      {
        uint32_t A;
        uint32_t B;
      } ;
    };
  };

  struct EXMPL aStruct = {{{{ 0x00, 0x00, 0x01, 0x00 }, { 0x00, 0x00, 0x00, 0x00 }}}};
  ...