Contents
run
set args test1 test2
show args
next
step
finish - takes you out of the function call, if you are already inside one
return - returns to the caller of the current frame in the stack. This means that you can return from a function without actually completing the function code execution.
continue
quit
kill - stops debugging but does not quit the debugger
break function_name
break file.c:n
info break
disa/enable *m* - disable/enable break
del *m*
!!!!! condition bp_number [expression]
condition 2 - deletes condition
!!!!! watch expression - The debugger stops the program when the value of expression changes.
!!!!! rwatch expression - The debugger stops the program whenever the program reads the value of any object involved in the evaluation of expression.
!!!!! awatch expression - The debugger stops the program whenever the program reads or modifies the value of any object involved in the evaluation of expression.
info locals - print all local variables
list n - lists lines in the source code file
list n, m
print expr
p 2*circularArea($2) - $i - refer to previous output
!!! p main::radius - access variable in other stack frame
ptype var - prints structure or union
display expr - (disp)
undisplay
info display
enable/disable display
show path
pwd
print var1
set var1=22
print var1
show environment - displays environment variables
set/unset env
frame - shows the current frame of execution for the program
info frame
info locals
info reg
info all-reg - including math registers
backtrace
up - takes you one level up in the stack
down
info files
info share
Compile with options gcc -gdwarf-4 -g3 sample.c -o sample
info macro ADD
macro expand ADD(x)
C-x C-a - enter or leave the TUI mode
C-x 2 - change layout (1 or 2 windows)
C-x o - change active window
C-x s - switch TUI SingleKey mode
C-L - refresh
info win (i win) - current window info
focus winname - (fs) - set focus to "SRC", "CMD", "ASM", or "REG" or by position "next" or "prev"
layout type - set layout "src", "asm", "split", or "reg"
tui reg type - set the register window layout "general", "float", "system", or "next"
winheight val - (wh) - set the window height (either an absolute value, or a relative value prefaced with "+" or "-")
C-p - previous command in history
C-n - next command in history
C-f - move cursor forward
C-b - move cursor backward
M-f - move cursor forward word
M-b - move cursor backward word
C-a - move to the start of the line
C-e - move to the end of the line
C-d - delete the character underneath the cursor
C-_ or C-x C-u - undo the last editing command
C-l - clear the screen
C-k - kill to the end of the line
M-d - kill to the end of the current word
M-<DEL> - kill from the cursor the start of the current word
C-w - kill from the cursor to the previous whitespace
C-y - yank the most recently killed text back
M-y - rotate the kill-ring, and yank the new top. You can only do this if the prior command is C-y or M-y
set disassembly-flavor flavor - set the look-and-feel of the disassembly. On Intel machines, valid flavors are intel and att
set disassemble-next-line on
(gdb) break *label+offset
(gdb) break *_start
(gdb) break *_start+1(gdb) x/d 0x100001018
0x100001018 <natural_generator.b>: -1
(gdb) x/d &b
0x100001018 <natural_generator.b>: -1(gdb) x/20x $rsp-20
0x7fffffffe800: 0x00000000 0x00000000 0x00000000 0x00000000
0x7fffffffe810: 0x00000000 0x00000000 0x00000000 0x00000000
0x7fffffffe820: 0x439d1463 0x00000000 0x00000000 0x00000000
0x7fffffffe830: 0x004000c2 0x00000000 0x0000000a 0x00000000
0x7fffffffe840: 0x00000001 0x00000000 0xffffeb0f 0x00007fff(gdb) x/10i $rip
=> 0x40011f <area+27>: pop %rbp
0x400120 <area+28>: retq
0x400121: jg 0x400123
0x400123: add %al,(%rcx)- d - decimal
- x - hexadecimal
- t - binary. The letter `t' stands for "two"
- u - unsigned
- o - octal
- f - floating point
- i - instruction
- c - character
- s - string
- a - address. You can use this format used to discover where (in what function) an unknown address is located:
(gdb) p/a 0x54320
$1 = 0x54320 <_initialize_vx+396>
(gdb) p/a &h
$2 = 0x7ffff7dd7820 <h>
# same as
(gdb) info symbol 0x54320
(gdb) info symbol &h
h in section .bss of /lib/x86_64-linux-gnu/libc.so.6
(gdb) p (int)$rax
$3 = -1- b - byte
- h - halfword (2 bytes)
- w - word (4 bytes)
- g - giant (8 bytes)
- l for a 32-bit long word value
- w for a 16-bit word value
- b for an 8-bit byte value
x/nfu addr- n, the repeat count
- f, the display format is one of the formats used by print (‘x’, ‘d’, ‘u’, ‘o’, ‘t’, ‘a’, ‘c’, ‘f’, ‘s’), and in addition ‘i’ (for machine instructions). The default is ‘x’ (hexadecimal) initially. The default changes each time you use either x or print.
- u, the unit size
(gdb) x/42cb &output
0x80490ac <output>:84 ‘T’ 104 ‘h’ 101 ‘e’ 32 ‘ ‘ 112 ‘p’ 114 ‘r’ 111 ‘o’99 ‘c’info locals - print all local variables
p *data@10 - print array
n
<enter> - repeat last command
call PyObject_Print(0x7ffff7f64ea0, stderr, 1)
info threads
thread 2
(gdb) target record-full
(gdb) next
(gdb) reverse-nexthttps://sourceware.org/gdb/current/onlinedocs/gdb/Reverse-Execution.html
http://stackoverflow.com/questions/1206872/go-to-previous-line-in-gdb
-cd Specify the working directory
-d Specify a directory to search for source files
-nx Do not execute commands from .gdbinit file
./configure --with-python --prefix=/home/user/opt/gdb make make install