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  1. #include <stdio.h>
  2. #include <limits.h>
  3.  
  4. #if CHAR_BIT != 8
  5. #error "unsupported char size"
  6. #endif
  7.  
  8. typedef enum { ONE, TWO, THREE } my_enum;
  9.  
  10. typedef struct
  11. {
  12.    unsigned long var1 : 8;
  13.    unsigned long var2 : 24;
  14.    my_enum       var3 : 2;
  15.    my_enum       var4 : 2;
  16. } my_struct;
  17.  
  18. int main(void)
  19. {
  20.    int idx;
  21.    int bitIdx;
  22.    my_struct my_struct_var;
  23.  
  24.    memset (&my_struct_var,
  25.            0,
  26.            sizeof(my_struct_var));
  27.  
  28.    printf("sizeof(my_struct)     = %lu\n", sizeof(my_struct));
  29.    printf("sizeof(my_struct_var) = %lu\n", sizeof(my_struct_var));
  30.  
  31.    my_struct_var.var1 = 0x81;     /* 1000 0001                     */
  32.    my_struct_var.var2 = 0x800001; /* 1000 0000 0000 0000 0000 0001 */
  33.    my_struct_var.var3 = 0b10;     /* 10                            */
  34.    my_struct_var.var4 = 0b11;     /* 11                            */
  35.  
  36.    for (idx = 0; idx < sizeof(my_struct_var); ++idx)
  37.    {
  38.       char * curByte = &my_struct_var;
  39.       curByte += idx;
  40.       printf("\nByte %d:  ", idx);
  41.       for (bitIdx = 0; bitIdx < CHAR_BIT; ++bitIdx)
  42.       {
  43.          printf("%c ", ((*curByte & (1 << ((CHAR_BIT - 1) - bitIdx))) >> ((CHAR_BIT - 1) - bitIdx)) + '0');
  44.       }
  45.    }
  46.  
  47.    return 0;
  48. }
Success #stdin #stdout 0s 10320KB
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stdin
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Standard input is empty
stdout
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sizeof(my_struct)     = 8
sizeof(my_struct_var) = 8

Byte 0:  1 0 0 0 0 0 0 1 
Byte 1:  0 0 0 0 0 0 0 1 
Byte 2:  0 0 0 0 0 0 0 0 
Byte 3:  1 0 0 0 0 0 0 0 
Byte 4:  0 0 0 0 1 1 1 0 
Byte 5:  0 0 0 0 0 0 0 0 
Byte 6:  0 0 0 0 0 0 0 0 
Byte 7:  0 0 0 0 0 0 0 0
https://ideone.com/OxkAVi
language:
C (gcc 8.3)
created:
8 years ago
visibility:
public

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