gdb_part1

This is the GNU debugger. Usage:

    gdb [options] [executable-file [core-file or process-id]]

Options:

--[no]async    p;    Enable (disable) asynchronous version of CLI
-b BAUDRATE        Set serial port baud rate used for remote debugging.
--batch    &nbbsp;       Exit after processing options.
--cd=DIR    &nnbsp;      Change current directory to DIR.
--command=FILE   &nnbsp; Execute GDB commands from FILE.
--core=COREFILE    Analyze the core dump COREFILE.
--pid=PID    &      Attach to running process PID.
--dbx     p;         DBX compatibility mode.
--directory=DIR    Search for source files in DIR.
--objectdir=DIR    Search for object files in DIR.
--epoch    &nbbsp;       Output information used by epoch emacs-GDB interface.
--exec=EXECFILE    Use EXECFILE as the executable.
--fullname    ;     Output information used by emacs-GDB interface.
--help    &nbssp;        Print this message.
--interpreter=INTERP
                     Select a specific interpreter / user interface
--mapped    &nnbsp;      Use mapped symbol files if supported on this system.
--nw     ;          Do not use a window interface.
--nx     ;          Do not read .gdbinit file.
--quiet    &nbbsp;       Do not print version number on startup.
--readnow    &      Fully read symbol files on first access.
--se=FILE    &      Use FILE as symbol file and executable file.
--symbols=SYMFILE Read symbols from SYMFILE.
--tty=TTY    &      Use TTY for input/output by the program being debugged.
--tui     p;         Use a terminal user interface.
--version    &      Print version information and then exit.
-w     &nnbsp;           Use a window interface.
--write    &nbbsp;       Set writing into executable and core files.
--xdb     p;         XDB compatibility mode.

For more information, type "help" from within GDB, or consult the
GDB manual (available as on-line info or a printed manual).
Report bugs to "[email protected]".

<ntc63> gdb -q
(gdb) file strlen
Reading symbols from strlen...done.
>> we are having debugging symbols to process the operation
(gdb) li 1,20
1       #include <stdio.h>
2       #include <stdlib.h>
3       main()
4       {
5               char *p;
6               fflush(stdout);
7               p=(char *)malloc(100*sizeof(char));
8               printf("\nEnter a string for test\n");
9               gets(p);
10              printf("%s\n",p);
11              free(p);
12      }

>> Source lines of input files. list (li) will show all lines 1,20 (if it is not there too it will try to show upto the limit)

(gdb) b main
Breakpoint 1 at 0x4000920:1: file strlen.c, line 6.

>> break point at main function. It will give the informations of break points

(gdb) info b
Num Type           Disp Enb Address    What
1   breakpoint     keep y   0x04000921 in main at strlen.c:6

>> To know all break point informations then use info breakpoint (info b)

(gdb) r
Starting program: /muthu/gdbtest/strlen

Breakpoint 1, main () at strlen.c:6
6               fflush(stdout);

>> Startup of program debugging as run (r). If you have command line argument(s) then specify here as r <arg1> <arg2> ..<argn>

(gdb) disp p
1: p = 0x1 <Error reading address 0x1: Invalid argument>

>> If you want to keep track of some variables informations every stage then specify the variable with display <variable> >> name. To make it undisplay in next step then undisplay <variable>. It will be very effective to know the status at every stage

(gdb) s
7               p=(char *)malloc(100*sizeof(char));
1: p = 0x1 <Error reading address 0x1: Invalid argument>

>> To go to next debugging instruction use step(s) or next(n) If you want to move to step more than 1 then use
>> step <count> (s 10) to move to the 10 the instruction for now

(gdb) s
8               printf("\nEnter a string for test\n");
1: p = 0x40002420 ""
(gdb) s

Enter a string for test
9               gets(p);
1: p = 0x40002420 ""
(gdb)
hai gdb
10              printf("%s\n",p);
1: p = 0x40002420 "hai gdb"
(gdb) s
hai gdb
11              free(p);
1: p = 0x40002420 "hai gdb"
(gdb)
12      }
1: p = 0x40002420 "hai gdb"

>> If you are going to use particular prev command on next time then just press <ENTER> it will do it. !!!
>> To know about gdb command history then try # apropos history

(gdb)
0x20000000679abcc0:0 in main_opd_entry+0x50 () from /usr/lib/hpux32/dld.so
(gdb)
Single stepping until exit from function main_opd_entry,
which has no line number information.
0x20000000679abc50:0 in enter_main_opd+0x40 () from /usr/lib/hpux32/dld.so
(gdb)
Single stepping until exit from function enter_main_opd,
which has no line number information.
0x20000000679b11d0:0 in dld_main_startup+0xf50 () from /usr/lib/hpux32/dld.so
(gdb)
Single stepping until exit from function dld_main_startup,
which has no line number information.
warning: Cannot insert breakpoint 0: in /usr/lib/hpux32/dld.so
warning: dld.so is a shared library and will never be loaded
warning: as private, so breakpoint 0 has been ignored.
warning: Temporarily disabling shared library breakpoints:
0

Program exited normally.
>> It will give you execution status of a program from gdb
(gdb)