gdb Quick Reference¶

What is gdb¶

According to GNU, GDB, the GNU Project debugger, allows you to see what is going on "inside" another program while it executes - or what another program was doing at the moment it crashed.

Compiling For gdb¶

gdb needs information that is not ordinarily provided by the compiler. So, if you want to use gdb you need to include the -g switch when compiling. For example:

g++ -c -g Driver.cpp

Starting gdb¶

To start gdb, simply enter the gdb command in a terminal window. It has one parameter, the name of the executable. For example:

gdb Driver

Basic gdb Commands¶

The following commands are listed in alphabetical order:

Command	Purpose
Enter	Re-execute the previous gdb command
break xx	Set a breakpoint at line xx in the current file
break functionname	Set a breakpoint at the start of functionname
break classname::functionname	Set a breakpoint at the start of a method
break filename:xx	Set a breakpoint at line xx in a specified file
continue	Resume running/executing the program
disable xx	Disable breakpoint number xx
enable xx	Enable breakpoint number xx
help	Display a list of gdb commands
help command	Get help on a specific command
info break	List all breakpoints
info source	Show the name of the current source file
info sources	List the name of all source files in use
list	List the next source lines
list xx	List source lines starting at line xx
list xx,yy	List sources lines from xx to yy
list filename:xx	List source lines in the specified file starting at line xx
next	Execute the current statement and then stop
print variable	Print the value of a variable
quit	Quit gdb
run	Run/execute the program starting from the beginning
set variable = value	Assign a new value to a variable
step	Execute the current statement (entering a function if possible)

A Sample Session¶

A small sample session of gdb (with an executable named Driver) might look something like the following [where $ is the shell prompt and (gdb) is the gdb prompt]:

$ gdb Driver
(gdb) break 1
(gdb) run
(gdb) next
(gdb) print i
(gdb) next
(gdb) print i
(gdb) quit

Last modified: 2026-01-26 16:30 by Dylan (3c67503)