CSC161 2010F, Class 28: More Debugging with DDD

Overview:
* Sam does exercise 1, more or less
* Lab.

Admin:
* Are there general questions on Assignment 5?
* Reading for Friday: K&R 4.11.
* The reading on Make is now due Monday after break.

Questions on assignment 5?

* How do I write part of my Makefile?
  * Step one: Identify important components
    array_utils.h, array_utils.c, utest_swap.c
  * Step two: Write dependencies that say "To make the application, we
    need the .o file"
utest_swap: array_utils.o utest_swap.o
        $(CFLAGS) -o utest_swap array_utils.o utest_swap.o
    Also okay to write
        cc -o utest_swap array_utils.o utest_swap.o
    Also okay to write
utest_swap: array_utils.c utest_swap.c array_utils.h
        $(CFLAGS) -o utest_swap array_utils.o utest_swap.o
   * Step three: Write dependencies that say "The .o files depend on the
     .h file"
array_utils.o: array_utils.c array_utils.h
utest_swap.o: utest_swap.c array_utils.h
* I didn't get that.  What should the Makefile end up looking like?

utest_swap: array_utils.o utest_swap.o
        $(CFLAGS) -o utest_swap array_utils.o utest_swap.o
array_utils.o: array_utils.c array_utils.h
utest_swap.o: utest_swap.c array_utils.h

* Testing of swap.  How do I test it, given that it doesn't return a value.
  int a[] = { 0, 1, 2, 3 };
  swap (a, 1, 2);
  if (a[1] != 2)
    {
      ++errors;
      printf ("Error: After swap (a,1,2), we have %d at a[1]\n", a[1]);
    }
  if (a[2] != 1)
    {
      ++errors;
      printf ("Error: After swap (a,1,2), we have %d at a[2]\n", a[1]);
    }
  * Of course, you really should write  helper to make all of this more
    concise.
* What do you mean by "systematic testing"
  * Think back to our testing of binary search
  * We want a large group of tests that broadly explore the testing space
  * We want to rely on the computer to build as much of tests as we can
    (no one wants to write 100 tests by hand)
* How many tests is enough?
  * Probably between 100 and 10000.
* Will you help me figure out this error message?
  * During lab
* Do we need to include array_util.h in both array_util.c and 
  utest_whatever.c?
  * Yes!
* In both?
  * Yes
* Why?
  * Because I said so
* Weren't you told not to say "Because I said so"?
  * Yes, but when I asked why, they said ...