4.3BSD - /usr/include/struct.h

   1: /*	struct.h	4.1	83/05/03	*/
   2: 
   3: /*
   4:  * access to information relating to the fields of a structure
   5:  */
   6: 
   7: #define fldoff(str, fld)    ((int)&(((struct str *)0)->fld))
   8: #define fldsiz(str, fld)    (sizeof(((struct str *)0)->fld))
   9: #define strbase(str, ptr, fld)  ((struct str *)((char *)(ptr)-fldoff(str, fld)))

Defined macros

Usage of this include