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  1. #include <stdio.h>
  2. #include <string.h>
  3.  
  4. struct my_type_t {
  5.     int x;
  6.     int y;
  7.     int z;
  8. };
  9.  
  10. struct my_array_t {
  11.     struct my_type_t test;
  12.     int otherstuff;
  13. };
  14.  
  15. #define GET_STRUCT_OFFSET(st, m) ((size_t) ( (char *)&((st *)(0))->m - (char *)0 ))
  16. #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
  17.  
  18. void somefunction(struct my_array_t *arrayofstructs, size_t offset, int value) {
  19.     int i;
  20.     for (i = 0; i < 5; i++) {
  21.         //Unfortunatly can't do straight assignment not an lvalue
  22.         //if you just want to use the member as a rvalue and not assign can do so normally
  23.         memcpy((((void *)&arrayofstructs[i].test) + offset), &value, sizeof(value));
  24.     }
  25. }
  26. int main(void) {
  27.     struct my_array_t arrayofstructs[5];
  28.     somefunction(arrayofstructs, GET_STRUCT_OFFSET(struct my_type_t, x), 1);
  29.     somefunction(arrayofstructs, GET_STRUCT_OFFSET(struct my_type_t, y), 2);
  30.     somefunction(arrayofstructs, GET_STRUCT_OFFSET(struct my_type_t, z), 3);
  31.  
  32.     int i;
  33.     for(i = 0; i<5; i++) {
  34.         printf("Struct %d: X = %d, Y = %d, Z = %d\n",i,arrayofstructs[i].test.x \
  35.                                                       ,arrayofstructs[i].test.y \ 
  36.                                                       ,arrayofstructs[i].test.z);
  37.     }
  38.  
  39.     return 0;
  40. }
  41.  
  42.  
Success #stdin #stdout 0s 1832KB
comments (?)
stdin 
Standard input is empty
stdout 
Struct 0: X = 1, Y = 2, Z = 3
Struct 1: X = 1, Y = 2, Z = 3
Struct 2: X = 1, Y = 2, Z = 3
Struct 3: X = 1, Y = 2, Z = 3
Struct 4: X = 1, Y = 2, Z = 3
https://ideone.com/zwvTY1
language:
C (gcc 8.3)
created:
12 years ago
visibility:
public

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