Notes: Thursday Halloween 2002

Schedule

• Now: Problem Set 5: Part 2
• Tuesday, 12 November: Problem Set 6
• Thursday, 14 November: Exam 2 Out
• Tuesday, 19 November: Exam 2 Due

Null Pointer Dereferences
What can happen if a C program dereferences a null pointer?

How can we detect and avoid null pointer dereferences?

Memory Management in C

What happens if a program does not release the memory it allocates?

How can programmers document assumptions about memory management?

Malloc and Free

/*@only@*/ /*@null@*/ void * malloc(size_t bytes);
void free(/*@only@*/ void * ptr);

Species Constructor

/*@only@*/ Species Species_new (/*@only@*/ char *name,
                                /*@only@*/ char *genome) {
  Species s = (Species) malloc (sizeof (*s));
  if (s == NULL) {
    fprintf (stderr, "Out of memory in Species_new.\n");
    exit(EXIT_FAILURE);
  }

  s->name = name;
  s->genome = genome;
  return s;
}

University of Virginia Department of Computer Science CS 201J: Engineering Software

Sponsored by the National Science Foundation

cs201j-staff@cs.virginia.edu