c - Generate an array with offset of structure fields -

i interested in generating array offset of structure fields.

struct b {   int pig[100];   bool donkey[100]; }  struct {    int ant[100];    bool cat[38];    struct b dog[78]; }  main () {    int offset[100+38+78] /* ant offsets + cat offsets + dog offsets */    /* how fill these offset array fill in offsets of ant, cat, dog */ }  output should like: offset[0] = 0; offset[1] = 4; ...... ...... offset[99]= 4*99; ....... offset[100+38+78-1] = ? ; 

i know c doesn't support reflection , can make use of x_macros extent, structures complex. kickstart basic simple structure had posted in question.

you can convert addresses of array elements char * , subtract address of structure.

struct a; (int = 0; < 100; i++) {     offset[i] = (char*)&a.ant[i] - (char*)&a; } (int = 0; < 38; i++) {     offset[100 + i] = (char*)&a.cat[i] - (char*)&a; } (int = 0; < 78; i++) {     offset[100 + 38 + i] = (char*)&a.dog[i] - (char*)&a;