c - gcc sizeof float _Imaginary

Question

我正在尝试获取 gcc 数据类型的字节存储大小。下面列出了我正在使用的程序。

// limits.c
// show data type storage size in bytes
  #include <stdio.h>
  #include <limits.h>

  int main(int argc, char* args[]) {
        printf("         Type          Bytes\n");
        printf("  ---------------------------\n");
        printf("  char................... %d \n",   sizeof(char));
        printf("  unsigned char.......... %d \n",   sizeof(unsigned char));
        printf("  signed char............ %d \n\n", sizeof(signed char ));

        printf("  int.................... %d \n",   sizeof(int));
        printf("  unsigned int........... %d \n",   sizeof(unsigned int));
        printf("  signed int............. %d \n\n", sizeof(signed int));

        printf("  short.................. %d \n",   sizeof(short ));
        printf("  unsigned short......... %d \n",   sizeof(unsigned short));
        printf("  signed short........... %d \n\n", sizeof(signed short));

        printf("  long................... %d \n",   sizeof(long ));
        printf("  unsigned long.......... %d \n",   sizeof(unsigned long));
        printf("  signed long............ %d \n\n", sizeof(signed long));

        printf("  long................... %d \n",   sizeof(long long));
        printf("  unsigned long.......... %d \n",   sizeof(unsigned long long));
        printf("  signed long............ %d \n\n", sizeof(signed long long));

        printf("  float _Complex......... %d \n",   sizeof(float _Complex));          
        printf("  double _Complex........ %d \n",   sizeof(double _Complex));       
        printf("  long double _Complex... %d \n\n", sizeof(long double _Complex));  

//    printf("  float _Imaginary....... %d \n",   sizeof(float _Imaginary));         
//    printf("  double _Imaginary...... %d \n",   sizeof(double _Imaginary));     
//    printf("  long double _Imaginary. %d \n",   sizeof(long double _Imaginary));

        printf("  Press any key to exit...");
        getchar();
        return 0;
  }

除了我尝试获取_Imaginary数据类型的大小(我已将其注释掉以确保程序正常运行)之外，该代码有效。我正在使用“gcc -std=gnu99 -o %OUT% %SRC%”，这应该强制 C99 合规性。我必须做什么才能让这个 sizeof 起作用？

Answer 1

您收到语法错误，因为 gcc 未实现 _Imaginary:

来自gcc c99 status page :

GCC does not support the Annex G imaginary types, but this support is optional ...

引用自cppreference on _Imaginary_I :

A compiler that defines __STDC_IEC_559_COMPLEX__ is not required to support imaginary numbers. POSIX recommends checking if the macro _Imaginary_I is defined to identify imaginary number support. (since C99) (until C11)

Imaginary numbers are supported if __STDC_IEC_559_COMPLEX__ is defined. (since C11)

原始问题使用C99，但gcc也在C11模式下定义了__STDC_IEC_559_COMPLEX__，即使它不支持_Imaginary，这有点烦人，听起来像是一种违规的标准。