Using Debugger

1. GNU Debugger (gdb) is a powerful terminal debugger for Unix-like systems. GDB offers tracing and altering how computer programs are working. Below are some commands:
   • run: Used for starting your application under gdb.
   • step: Step-by-step program execution.
   • print $<$expression$>$: Displays the current state of given expression.
   • break $<$function$>$ | $<$line$>$: Inserts a breakpoint at the given line or function.
   • clear $<$function$>$ | $<$line$>$: Removes the breakpoint at the given line or function. If no parameters are passed, all breakpoints will be removed.
   • list: Prints lines from source code.
2. An example gdb execution; http://siber.cankaya.edu.tr/OperatingSystems/cfiles/code1.ccode1.c

   $ gcc  -O0 -g -o code1 code1.c
   $ gdb code1
   GNU gdb (GDB) 7.0-ubuntu
   Copyright (C) 2009 Free Software Foundation, Inc.
   License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
   This is free software: you are free to change and redistribute it.
   There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
   and "show warranty" for details.
   This GDB was configured as "x86_64-linux-gnu".
   For bug reporting instructions, please see:
   <http://www.gnu.org/software/gdb/bugs/>...
   Reading symbols from /home/ceng328/code1...done.
   (gdb) list
   1       #include <stdio.h>
   2
   3       int
   4       main(int argc, char* argv[])
   5       {
   6           printf ("hello world\n");
   7
   8           return 0;
   9       }
   (gdb) run
   Starting program: /home/ceng328/code1
   hello world
   
   Program exited normally.
   (gdb) break 6
   Breakpoint 1 at 0x400533: file code1.c, line 6.
   (gdb) run
   Starting program: /home/ceng328/code1
   
   Breakpoint 1, main (argc=1, argv=0x7fffffffe308) at code1.c:6
   6           printf ("hello world\n");
   (gdb)