st2.c. puzzle book

st2.c

#include "defs.h"

struct S1 {
        char *s;
        int i;
        struct S1 *s1p;
};

void main(){
        static struct S1 a[] = {
                { "abcd", 1, a+1 },
                { "efgh", 2, a+2 },
                { "ijkl", 3, a }
        };
        struct S1 *p = a;                                               //Structures 2.1
        int i;

        PRINT3(s, a[0].s, p->s, a[2].s1p->s);   //Structures 2.2

        for( i=0; i<2; i++ ) {
                PR(d, --a[i].i);
                PR(c, ++a[i].s[3]);                                     //Structures 2.3
                NL;
        }

        PRINT3(s, ++(p->s), a[(++p)->i].s, a[--(p->s1p->i)].s);
         //Structures 2.4
}

bash

$ gcc st2.c
$ ./a.out
a[0].s = abcd   p->s = abcd     a[2].s1p->s = abcd
Segmentation fault (core dumped)
``

```c:st2a.c
#include "defs.h"

struct S1 {
        char *s;
        int i;
        struct S1 *s1p;
};

void main(){
        static struct S1 a[] = {
                { "abcd", 1, a+1 },
                { "efgh", 2, a+2 },
                { "ijkl", 3, a }
        };
        struct S1 *p = a;                                               //Structures 2.1
        int i;

        PR(s, a[0].s);
        PR(s, p->s);
        PR(s,   a[2].s1p->s);

        PRINT3(s, a[0].s, p->s, a[2].s1p->s);   //Structures 2.2

        for( i=0; i<2; i++ ) {
                PR(d, --a[i].i);
                PR(c, ++a[i].s[3]);                                     //Structures 2.3
                NL;
        }
        PR(s, ++(p->s));
        PR(s,  a[(++p)->i].s);
        PR(s, a[--(p->s1p->i)].s);




        PRINT3(s, ++(p->s), a[(++p)->i].s, a[--(p->s1p->i)].s);
                                                                                        //Structures 2.4
}

$ gcc st2.c
inst19@teachB:~$ ./a.out
a[0].s = abcd   p->s = abcd     a[2].s1p->s = abcd      a[0].s = abcd   p->s = abcd     a[2].s1p->s = abcd
Segmentation fault (core dumped)