Question 1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

main(int argc, char **argv)
{
  char *s, *u, *v;

  s = argv[1];
  v = strchr(s, 'G');
  u = strdup(s);
  
  if (v == NULL) exit(0);

  *v = 'g';
  v += 5;
  *v = 'i';

  printf("0x%x 0x%x\n", s, u);

  printf("argc: %d\n", argc);
  printf("argv[1]: 0x%x %s\n", argv[1], argv[1]);
  printf("s: 0x%x %s\n", s, s);
  printf("u: 0x%x %s\n", u, u);
  printf("v: 0x%x %s\n", v, v);
  printf("strstr: 0x%x %s\n", strstr(u, "ge"), strstr(u, "ge"));
}

Part 1: Suppose we compile this into an executable called pex, and run it from the shell as below. I give the first line of output. What are the remaining lines of output? Put question marks where you don't know the answer, but answer everything that you can.

UNIX> pex Curious-George Prince-George Eddie-George
0xbfffedd8 0x3000f0

Part 2: You'll note that the above program does no error checking. Give two examples of running it from the command line where the output will be non-deterministic (e.g. a Bus error, Segmentation violation, or some kind of random output) and state why these examples are problemmatic. Note, you don't need to specify what the output is, just why the examples are problemmatic.

Question 2

List *new_list() - Create and return a new empty list. This will consist solely of the header struct whose front and rear pointers will be NULL. int list_empty(List *l) - Is a list empty? Node *list_front(List *l) - return a pointer to the first node on the list, or NULL if the list is empty. void list_prepend(List *l, Jval v) - allocate a new node with value v and put it on the front of the list. void list_append(List *l, Jval v) - allocate a new node with value v and put it on the end of the list. void list_insert_after(List *l, Node *n, Jval v) - allocate a new node with value v and put it after node n. int list_size(List *l) - Return the number of nodes on the list. void free_list(List *l) - free up the header structure and the nodes.

Implement the three procedures: new_list(), list_prepend(). and free_list().

Question 3

Question 4

#include <stdio.h>
#include <stdlib.h>
#include "fields.h"
#include "stack.h"
#include "queue.h"
#include "dllist.h"

main()
{
  IS is;
  Queue q;
  Stack s;
  Dllist l;
  int i;
  Jval j;

  is = new_inputstruct(NULL);

  while (get_line(is) > 0) {
    q = new_queue();
    s = new_stack();
    l = new_dllist();
    for (i = 0; i < strlen(is->fields[0]); i++) {
      queue_enqueue(q, new_jval_c(is->fields[0][i]));
      stack_push(s, new_jval_c(is->fields[0][i]));
      dll_append(l, new_jval_c(is->fields[0][i]));
      dll_prepend(l, new_jval_c(is->fields[0][i]));
    }
    while (!queue_empty(q)) {
      j = queue_dequeue(q); printf("%c", j.c);
      j = stack_pop(s); printf("%c", j.c);
      printf("%c", l->flink->val.c); dll_delete_node(l->flink);
      printf("%c", l->flink->val.c); dll_delete_node(l->flink);
      printf(" ");
    }
    printf("\n");
    free_queue(q);
    free_stack(s);
    free_dllist(l);
  }
}

What will the output of this program be when the following file is given as standard input:

1 2 3
Fred Luther Dontonio
Eddie Prince Curious

Frank Lloyd Wright
22

Prototypes

typedef union {
    int i;
    double d;
    void *v;
    char *s;
    char c;
    ...
  } Jval;  

Jval new_jval_i(int);
Jval new_jval_d(double);
Jval new_jval_v(/* void */);
Jval new_jval_s(char *);
Jval new_jval_c(char);

#define MAXLEN 1001
#define MAXFIELDS 1000

typedef struct inputstruct {
  char *name;
  int line;
  char text1[MAXLEN];
  int NF;
  char *fields[MAXFIELDS];
  ...
} *IS;

IS new_inputstruct(char *name);
int get_line(IS);
void jettison_inputstruct(IS);