CS 2734 Computer Organization II

Laboratory 3 [2/3; 2/5] Introduction to the Debugger

This laboratory explores the use of the debugger with assembly language programs. You will meet in 3.02.04SB for both laboratory 3a (2/3/97) and laboratory 3b (2/3/97). During both sessions, 10 workstations will be reserved for checkoff only. Do not log into these workstations unless you are ready to be checked off or everyone who is ready to be checked off has been checked off. You must log off of these workstations after being checked off so that others can have a chance. In the last 15 minutes of laboratory 3a, Ms. Dykes will give a demonstration of the debugger for those who are having difficulty.

Prior to the laboratory, you should do the following:
- Make a separate directory for laboratory 3 and put all of the code that you develop for this lab in that directory.
- Write a Sparc assembly language function
  int calcfun(int x, int y, int z)
  which computes calcfun(x, y, z) = x*y + z. The source for this file should be in calcfun.m. The parameters should be passed in the registers.
- Write a C main program to call calcfun. The source for this program should be in calcmain.c. This program should take three command line arguments to pass the values of x, y and z. Be sure to check for the correct number of command line arguments and print out a usage message if the call is incorrect. The main program should print out the values of the variables and the return value of calcfun.
- Write a Makefile that will compile these source files, first into separate object files and then into an executable mycalculate. Use the -g compilation option.
- Debug your program. Use the debugger to single step through the program as described in the checkoff procedure. A summary of debugger commands can be found on page 78 of Paul To run a program with command line arguments get into the debugger by typing gdb programname. Once you are in the debugger, you enter the command line arguments on the run statement:
```
     run 3 5 8
```
  executes the program with the command line arguments 3 5 and 8.
- Get a printout of your source files prior to the lab. Be sure to use prtext to print out source. Also get a printout of the .s by compiling calcmain.c with the -c -S option.
For Checkoff:
- Run the program with mycalculate 2 3 5 and show that you get the correct answer.
- Recompile your program using gcc rather than cc. (Change your Makefile.)
- Enter the debugger by typing:
  gdb mycalculate
- Set a breakpoint at the start of calcfun.
- Start running the program (r).
- When you reach the breakpoint, set the display to show each instruction as it is executing.
  (Use display/i $pc)
- Single set through the function without stepping through .mul.
  (Use ni)
- Show the values of all relevant registers before and after .mul
  (Use p)
- After return from the program allow the program to run continuously to completion.
- Enter the debugger again and this time single step through the C source. Prior to the call, change the value of x in the debugger.
- Run the program continuously to completion.
- Hand in your source.