Starting up the GDB tool

GDB is a popular standard debugger in the GNU operating system.  In this lab
we first review the basic commands and options of gdb, which is the
executable file of GDB.

To compile a program with debugger symbols, use the -g flag when you
compile.  For programs with a Makefile, it can also be included.

Once compilation with -g is done, you may use the executable to debug the
program.  The command to run gdb is


gdb EXECUTABLE_NAME


Here you may run the executable using by entering run or r.  If you need to
add command line arguments, you may add them when you run the executable.
For example: run ARG_1 ARG_2 ...

Breakpoints & Printing Info

If your program has a segmentation fault, memory error, or some other
program-terminating problems, gdb will halt and let you know that you have
hit an error.  It is useful to stop the execution of your program at an
arbitrary point.  This can be accomplished by setting breakpoints.  To set a
breakpoint, use the break command.  The break requires a line number to be
specified, and if there are multiple source files, you must specify that
too.  For example:


break LINE_NUMBER


break sourcefile.cpp:LINE_NUMBER


Once you hit a breakpoint, you may use the print and backtrace commands.
When the program stops, they can be used as described below:

print VARIABLE_NAME will print the value of a given variable name.  This can
be used to see what value is incorrect and is usually a good point to start
looking for bugs.

backtrace or bt will print the stack trace; this will show you the functions
that have been called up to the point of the crash.

To proceed with the program execution, there are several commonly used
commands:

continue or c to run the program until it encounters the next breakpoint or
the end of execution.

step or s to step through the program line by line.

next or n to step through the program, but skip over function calls (i.e.
treat the function call as one line of code rather than stepping through
each subsequent line of the function call)

To delete a breakpoint: delete BREAKPOINT_NUMBER

To list all breakpoints: info breakpoints

To quit gdb: quit