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GDB QUICK REFERENCE
GDB Version 4
Essential Commands gdb
program
[ core
]^
debug
program
[using coredump
core
]
b^ [
file :
] function
set breakpoint at
function
[in
file
]
run
[ arglist
]^
start your program
[with
arglist
]
bt^
backtrace:
display program stack
p^ expr
display the value of an expression
c^
continue running your program
n^
next line, stepping over function calls
s^
next line, stepping into function calls
Starting GDB gdb
start GDB, with no debugging files
gdb
program
begin debugging
program
gdb
program core
debug coredump
core
produced by
program
gdb --help
describe command line options
Stopping GDB quit
exit GDB; also
q^
or^ EOF
(eg
C-d
INTERRUPT
(eg^
C-c
) terminate current command, or send to running process
Getting Help help
list classes of commands
help
class
one-line descriptions for commands in
class
help
command
describe
command
Executing your Program run
arglist
start your program with
arglist
run
start your program with current argumentlist
run
< inf
outf
start your program with input, outputredirected
kill
kill running program
tty
dev
use^
dev as stdin and stdout for next
run
set args
arglist
specify
arglist
for next
run
set args
specify empty argument list
show args
display argument list
show environment
show all environment variables
show env
var
show value of environment variable
var
set env
var string
set environment variable
var
unset env
var
remove
var
from environment
Shell Commands cd^
dir^
change working directory to
dir
pwd
Print working directory
make
call “
make
shell
cmd
execute arbitrary shell command string
[ ]^
surround optional arguments
show one or more arguments
1991, 1992 Free Software Foundation, Inc.
Permissions on back
Breakpoints and Watchpoints break
[ file
:] line
b^ [
file :
] line
set breakpoint at
line
number
[in
file
]
eg:^
break main.c:
break
[ file
:] function
set breakpoint at
function
[in
file
]
break +
offset break -
offset
set break at
offset
lines from current stop
break *
addr
set breakpoint at address
addr
break
set breakpoint at next instruction
break
if^
expr
break conditionally on nonzero
expr
cond
n^ [
expr
]^
new conditional expression on breakpoint
n ;
make unconditional if no
expr
tbreak
temporary break; disable when reached
rbreak
regex
break on all functions matching
regex
watch
expr
set a watchpoint for expression
expr
catch
x^
break at C++ handler for exception
x
info break
show defined breakpoints
info watch
show defined watchpoints
clear
delete breakpoints at next instruction
clear
[ file
:] fun
delete breakpoints at entry to
fun
clear
[ file
:] line
delete breakpoints on source line
delete
[ n
]^
delete breakpoints
[or breakpoint
n ]
disable
[ n
]^
disable breakpoints
[or breakpoint
n ]
enable
[ n
]^
enable breakpoints
[or breakpoint
n ]
enable once
[ n
]^
enable breakpoints
[or breakpoint
n ]; disable
again when reached
enable del
[ n
]^
enable breakpoints
[or breakpoint
n ]; delete
when reached
ignore
n count
ignore breakpoint
n ,^
count
times
commands
n
[silent
]
command-list
execute GDB
command-list
every time
breakpoint
n^ is reached.
[silent
suppresses default display
]
end
end of
command-list
Program Stack backtrace
[ n ]
bt^
[ n ]^
print trace of all frames in stack; or of
n
frames—innermost if
n >
, outermost if
n <
frame
[ n ]
select frame number
n^ or frame at address
n ; if no
n , display current frame
up^
n^
select frame
n^ frames up
down
n^
select frame
n^ frames down
info frame
[ addr
]^
describe selected frame, or frame at
addr
info args
arguments of selected frame
info locals
local variables of selected frame
info reg
[ rn
]
info all-reg
[ rn
register values]
[for reg
rn ]
in selected
frame;
all-reg
includes floating point
info catch
exception handlers active in selected frame
Execution Control continue
[ count
]
c^ [
count
]^
continue running; if
count
specified, ignore
this breakpoint next
count
times
step
[ count
]
s^ [
count
]^
execute until another line reached; repeat^ count
times if specified
stepi
[ count
]
si^
[ count
]^
step by machine instructions rather thansource lines
next
[ count
]
n^ [
count
]^
execute next line, including any functioncalls
nexti
[ count
]
ni^
[ count
]^
next machine instruction rather than sourceline
until
[ location
]^
run until next instruction (or
location
finish
run until selected stack frame returns
return
[ expr
]^
pop selected stack frame without executing^ [setting return value
]
signal
num
resume execution with signal
s^ (none if
jump
line jump *
address
resume execution at specified
line
number or
address
set var=
expr
evaluate
expr
without displaying it; use for
altering program variables
Display print
[/
f^ ] [
expr
]
p^ [
/ f^ ] [
expr
]^
show value of
expr
[or last value
$]
according to format
f :
x^
hexadecimal
d^
signed decimal
u^
unsigned decimal
o^
octal
t^
binary
a^
address, absolute and relative
c^
character
f^
floating point
call
[/
f^ ]^ expr
like
print
but does not display
void
x^ [
/ Nuf
]^ expr
examine memory at address
expr
; optional
format spec follows slash
N^
count of how many units to display
u^
unit size; one of
b^ individual bytes h^ halfwords (two bytes) w^ words (four bytes) g^ giant words (eight bytes)
f^
printing format.
Any
print
format, or
s^ null-terminated string i^ machine instructions
disassem
[ addr
]^
display memory as machine instructions
Automatic Display display
[/
f^ ]^ expr
show value of
expr
each time program stops
[according to format
f^ ]
display
display all enabled expressions on list
undisplay
n^
remove number(s)
n^ from list of
automatically displayed expressions
disable disp
n^
disable display for expression(s) number
n
enable disp
n^
enable display for expression(s) number
n
info display
numbered list of display expressions
Expressions expr
an expression in C, C++, or Modula-2(including function calls), or:
addr
@ len
an array of
len
elements beginning at
addr
file ::
nm^
a variable or function
nm
defined in
file
type
addr
read memory at
addr
as specified
type
$^
most recent displayed value
$ n^
n th displayed value
$$^
displayed value previous to $
$$ n
n th displayed value back from $
$^
last address examined with
x
$^
value at address $
$ var
convenience variable; assign any value
show values
[ n ]
show last 10 values
[or surrounding $
n ]
show convenience
display all convenience variables
Symbol Table info address
s^
show where symbol
s^ is stored
info func
[ regex
]^
show names, types of defined functions (all,or matching
regex
info var
[ regex
]^
show names, types of global variables (all,or matching
regex
whatis
[ expr
]
ptype
[ expr
]^
show data type of
expr
[or
$]
without
evaluating;
ptype
gives more detail
ptype
type
describe type, struct, union, or enum
GDB Scripts source
script
read, execute GDB commands from file^ script
define
cmd command-list
create new GDB command
cmd
; execute
script defined by
command-list
end
end of
command-list
document
cmd help-text
create online documentation for new GDBcommand
cmd
end
end of
help-text
Signals handle
signal act
specify GDB actions for
signal
print
announce signal
noprint
be silent for signal
stop
halt execution on signal
nostop
do not halt execution
pass
allow your program to handle signal
nopass
do not allow your program to see signal
info signals
show table of signals, GDB action for each
Debugging Targets target
type param
connect to target machine, process, or file
help target
display available targets
attach
param
connect to another process
detach
release target from GDB control
Controlling GDB set
param value
set one of GDB’s internal parameters
show
param
display current setting of parameter
Parameters understood by
set
and
show
complaints
limit
number of messages on unusual symbols
confirm
on/off
enable or disable cautionary queries
editing
on/off
control
readline
command-line editing
height
lpp
number of lines before pause in display
language
lang
Language for GDB expressions (
auto
,^ c^
or
modula-
listsize
n^
number of lines shown by
list
prompt
str
use^
str^ as GDB prompt
radix
base
octal, decimal, or hex number representation
verbose
on/off
control messages when loading symbols
width
cpl
number of characters before line folded
write
on/off
Allow or forbid patching binary, core files(when reopened with
exec
or^
core
history
h
groups with the following options:
h exp
off/on
disable/enable
readline
history expansion
h file
filename
file for recording GDB command history
h size
size
number of commands kept in history list
h save
off/on
control use of external file for commandhistory
print
p
groups with the following options:
p address
on/off
print memory addresses in stacks, values
p array
off/on
compact or attractive format for arrays
p demangl
on/off
source (demangled) or internal form for C++
symbols
p asm-dem
on/off
demangle C++ symbols in machine-
instruction output
p elements
limit
number of array elements to display
p object
on/off
print C++ derived types for objects
p pretty
off/on
struct display:
compact or indented
p union
on/off
display of union members
p vtbl
off/on
display of C++ virtual function tables
show commands
show last 10 commands
show commands
n^
show 10 commands around number
n
show commands +
show next 10 commands
Working Files file
[ file
]^
use^
file^
for both symbols and executable; with no arg, discard both
core
[ file
]^
read
file
as coredump; or discard
exec
[ file
]^
use^
file^
as executable only; or discard
symbol
[ file
]^
use symbol table from
file
; or discard
load
file
dynamically link
file
and add its symbols
add-sym
file addr
read additional symbols from
file
dynamically loaded at
addr
info files
display working files and targets in use
path
dirs
add dirs
to front of path searched for executable and symbol files
show path
display executable and symbol file path
info share
list names of shared libraries currentlyloaded
Source Files dir
names
add directory
names
to front of source path
dir
clear source path
show dir
show current source path
list
show next ten lines of source
list -
show previous ten lines
list
lines
display source centered around
lines
specified as one of:
[ file
:] num
line number
[in named file
]
[ file
:] function
beginning of function
[in named file
]
off^
lines after last printed
off^
lines previous to last printed
line containing
address
list
f , l
from line
f^ to line
l
info line
num
show starting, ending addresses of compiledcode for source line
num
info source
show name of current source file
info sources
list all source files in use
forw
regex
search following source lines for
regex
rev
regex
search preceding source lines for
regex
GDB under GNU Emacs M-x gdb
run GDB under Emacs
C-h m
describe GDB mode
M-s
step one line (
step
M-n
next line (
next
M-i
step one instruction (
stepi
C-c C-f
finish current stack frame (
finish
M-c
continue (
cont
M-u
up^ arg frames (
up)
M-d
down
arg
frames (
down
C-x &
copy number from point, insert at end
C-x SPC
(in source file) set break at point
GDB License show copying
Display GNU General Public License
show warranty
There is NO WARRANTY for GDB.Display full no-warranty statement. Copyright
1991, 1992 Free Software Foundation, Inc.
Roland Pesch ([email protected]),
January 1992—Revision:
The author assumes no responsibility for any errors on this card. This card may be freely distributed under the terms of the GNU General Public License.
Please contribute to development of this card by annotating it.
GDB itself is free software; you are welcome to distribute copies of it under the termsof the GNU General Public License.
There is absolutely no warranty for GDB.
