CS 2005 Techniques of Programming WPI, B Term 1996
Craig E. Wills Lab 4
Assigned: Wednesday, November 20, 1996

Introduction

The purpose of this lab is to review and understand how a debugger can be used in debugging a program. The debugger you will use is gdb.

Lab Procedure

Here is an outline of what you are to do for this lab:

• You should copy all files you need for this lab by issueing the command:

  > cp /cs/cs2005/pub/labs/lab4/* .

  You will now have a Makefile in your directory (will overwrite if one previously existed) and files beginning with lab4_.

• Type make to create lab4_rr.

• Run lab4_rr. Aargh!! The program crashes horribly! Here is where gdb comes into it

  Important:In order to use the debugger on a program it should be compiled with the `` -g'' option which saves symbol table information about the program at compilation time. The Makefile is set up to do so.

• Type gdb lab4_rr

• At the gdb prompt type run. This command will run lab4_rr. Note what happens. Pay special attention to any messages at the end.

  Here are a number of gdb commands we think you'll find useful in your quest

    h               help
    l               give a partial listing of the code
    p variable_name print the value of the variable
    b function-name set a break point at the beginning of the function
                    for a C++ member function try "b 'Stack::Push<TAB>"
    s               step to the next line
    c               continue running till the next break point
    bt              backtrace  (also called "where")
    q               quit

• At the minimum you should learn to use bt (or where) to find the line number if your program crashes. We also recommend a combination of setting breakpoints, stepping through the program and printing variable names. You do not need to limit yourself to these commands; help gives you a large variety of commands you can experiment with. Try as many as possible. You never know when it will be useful.

• Once you have fixed the error(s)(be sure to check that the program is working as expected), create a script file showing the correct program running.

Turnin

Turnin the script file using the command

/cs/cs2005/pub/bin/turnin lab4 lab4.script