extern int printf (const char *,...);struct s { struct s *n; } *p;struct s ss;#define MAX     10struct s sss[MAX];int count = 0;void sub( struct s *p, struct s **pp );int look( struct s *p, struct s **pp );main(){    struct s *pp;    struct s *next;    int i;    p = &ss;    next = p;    for ( i = 0; i < MAX; i++ ) {        next->n = &sss[i];        next = next->n;    }    next->n = 0;    sub( p, &pp );    if (count != MAX+2)      abort ();    exit( 0 );}void sub( struct s *p, struct s **pp ){   for ( ; look( p, pp ); ) {        if ( p )            p = p->n;        else            break;   }}int look( struct s *p, struct s **pp ){    for ( ; p; p = p->n )        ;    *pp = p;    count++;    return( 1 );}