usr/src/include/struct.h

/*      struct.h        4.1     83/05/03        */

/*
 * access to information relating to the fields of a structure
 */

#define fldoff(str, fld)        ((int)&(((struct str *)0)->fld))
#define fldsiz(str, fld)        (sizeof(((struct str *)0)->fld))
#define strbase(str, ptr, fld)  ((struct str *)((char *)(ptr)-fldoff(str, fld)))