Subject: [Announcement] gdb
        Date: Wed, 21 Feb 2001 15:50:03 -0500
        From: Igor Markov <imarkov@umich.edu>
Organization: U. of Michigan, EECS
  Newsgroups: umich.eecs.class.380


   If your program crashes with a "Bus Error" message or 
   a "Segmentation Fault" message (or says anything about
   SIGSEGV or SIGBUS), you may want to run it through a
   debugger.

   Note that crashes due to memory corruption, which are among possible
   reasons for segmentation faults and bus errors can be non-deterministic.
   They may depend on whether you compiled your program with -g or -O3,
   whether you are running it inside gdb or standalone, etc.  In any case,
   if there is an error message in one of those cases, there is probably
   an error in  your code. If there is no error message, you can't say for
   sure that everything is allright -- some bugs may be silent forever.

    Below I will cover gdb (the GNU debugger), which is not
   graphic, and thus can be used through telnet/ssh.
    If you want a graphic debugger, you can use ddd, which is
   a front end to gdb (it basically translates mouseclicks
   into gdb commands). Both are installed on CAEN machines.

    Unlike MicroSoft VC++ or CodeWarrior, gdb and ddd are free
   (gdb comes with most Linux distributions, ddd with some).
   If you are only interested in ddd, then just fire it up
   (with the same arrangements as gnuplot) and click on help.
   Otherwise, read on.
 

  To debug a program in gdb/ddd, make sure you compile your code
  with -g and w/o -O3. Produce an executable (OliverMaze) and type

gdb OliverMaze

   this will load OliverMaze and print a banner.
   When you see a gdb prompt, type

run -Stack

   (imagine that you are launching OliverMaze and giving it
    parameters, except that "run" stands for "OliverMaze"),
   or 

run -Queue
    depending on what you need.

   If there are any serious problems, there will be a message to
   that effect and it is likely to contain a filename and line number.
   you can then use the list command

list 300
    will show line 300 and several lines next to it in the current file
    (gdb loads the right after in most cases). You can specify the filename
    too, type

help list

    for more details.
    You can type   help   for general help and learn more commands.
    
quit 
    does the obvious

print variableName
    ditto

   A gdb tutorial can be found at   
   http://www.info.ucl.ac.be/etudiants/outils/cornell/gdb/
   I added it to the list of additional refs

   gdb has several graphic front ends:  xxgdb (so-so), ddd(excellent), etc.