Help
| Option | Description |
|---|---|
help | List gdb command topics. |
help topic-classes | List gdb command within class. |
help command | Command description. eg help show to list the show commands |
apropos search-word | Search for commands and command topics containing search-word. |
info args i args | List program command line arguments |
info breakpoints | List breakpoints |
info break | List breakpoint numbers. |
info break breakpoint-number | List info about specific breakpoint. |
info watchpoints | List breakpoints |
info registers | List registers in use |
info threads | List threads in use |
info set | List set-able option |
Break and Watch
| Option | Description |
|---|---|
break funtion-name break line-number break ClassName::functionName | Suspend program at specified function of line number. |
break +offset break -offset | Set a breakpoint specified number of lines forward or back from the position at which execution stopped. |
break filename:function | Don’t specify path, just the file name and function name. |
break filename:line-number | Don’t specify path, just the file name and line number.break Directory/Path/filename.cpp:62 |
break *address | Suspend processing at an instruction address. Used when you do not have source. |
break line-number⠀if condition | Where condition is an expression. i.e. x > 5 Suspend when boolean expression is true. |
break line⠀thread thread-number | Break in thread at specified line number. Use info threads to display thread numbers. |
tbreak | Temporary break. Break once only. Break is then removed. See “break” above for options. |
watch condition | Suspend processing when condition is met. i.e. x > 5 |
clear clear function clear line-number | Delete breakpoints as identified by command option. Delete all breakpoints in function Delete breakpoints at a given line |
delete d | Delete all breakpoints, watchpoints, or catchpoints. |
delete breakpoint-number delete range | Delete the breakpoints, watchpoints, or catchpoints of the breakpoint ranges specified as arguments. |
disable breakpoint-number-or-range enable breakpoint-number-or-range | Does not delete breakpoints. Just enables/disables them. Show breakpoints: info break i.e. disable 2-9 |
enable breakpoint-number once | Enables once |
continue c | Continue executing until next break point/watchpoint. |
continue number | Continue but ignore current breakpoint number times. Useful for breakpoints within a loop. |
finish | Continue to end of function. |
Line Execution
| Option | Description |
|---|---|
step s step number-of-steps-to-perform | Step to next line of code. Will step into a function. |
next n next number | Execute next line of code. Will not enter functions. |
until until line-number | Continue processing until you reach a specified line number. Also: function name, address, filename:function or filename:line-number. |
info signals info handle handle SIGNAL-NAME option | Perform the following option when signal received: nostop, stop, print, noprint, pass/noignore or nopass/ignore |
where | Shows current line number and which function you are in. |
Stack
| Option | Description |
|---|---|
backtrace bt bt inner-function-nesting-depth bt -outer-function-nesting-depth | Show trace of where you are currently. Which functions you are in. Prints stack backtrace. |
backtrace full | Print values of local variables. |
frame frame number f number | Show current stack frame (function where you are stopped) Select frame number. (can also user up/down to navigate frames) |
up down up number down number | Move up a single frame (element in the call stack) Move down a single frame Move up/down the specified number of frames in the stack. |
info frame | List address, language, address of arguments/local variables and which registers were saved in frame. |
info args info locals info catch | Info arguments of selected frame, local variables and exception handlers. |
Source Code
| Option | Description |
|---|---|
list l list line-number list function list - list start#,end# list filename:function | List source code. |
set listsize count show listsize | Number of lines listed when list command given. |
directory directory-name dir directory-name show directories | Add specified directory to front of source code path. |
directory | Clear sourcepath when nothing specified. |
Machine Language
| Option | Description |
|---|---|
info line info line number | Displays the start and end position in object code for the current line in source. Display position in object code for a specified line in source. |
disassemble 0xstart 0xend | Displays machine code for positions in object code specified (can use start and end hex memory values given by the info line command. |
stepi si nexti ni | step/next assembly/processor instruction. |
x 0xaddress x/nfu 0xaddress | Examine the contents of memory. Examine the contents of memory and specify formatting.
x/4dw var |
Examine Variables
| Option | Description |
|---|---|
print variable-name p variable-name p file-name::variable-name p 'file-name'::variable-name | Print value stored in variable. |
p *array-variable@length | Print first # values of array specified by length. Good for pointers to dynamically allocated memory. |
p/x variable | Print as integer variable in hex. |
p/d variable | Print variable as a signed integer. |
p/u variable | Print variable as a un-signed integer. |
p/o variable | Print variable as a octal. |
p/t variable x/b address x/b &variable | Print as integer value in binary. (1 byte/8bits) |
p/c variable | Print integer as character. |
p/f variable | Print variable as floating point number. |
p/a variable | Print as a hex address. |
x/w address x/4b &variable | Print binary representation of 4 bytes (1 32 bit word) of memory pointed to by address. |
ptype variable ptype data-type | Prints type definition of the variable or declared variable type. Helpful for viewing class or struct definitions while debugging. |
GDB Modes
| Option | Description |
|---|---|
set gdb-option value | Set a GDB option |
set logging on set logging off show logging set logging file log-file | Turn on/off logging. Default name of file is gdb.txt |
set print array on set print array off show print array | Default is off. Convient readable format for arrays turned on/off. |
set print array-indexes on set print array-indexes off show print array-indexes | Default off. Print index of array elements. |
set print pretty on set print pretty off show print pretty | Format printing of C structures. |
set print union on set print union off show print union | Default is on. Print C unions. |
set print demangle on set print demangle off show print demangle | Default on. Controls printing of C++ names. |
Start and Stop
| Option | Description |
|---|---|
run r run command-line-arguments run <infile> outfile | Start program execution from the beginning of the program. The command break main will get you started. Also allows basic I/O redirection. |
continue c | Continue execution to next break point. |
kill | Stop program execution. |
quit q | Exit GDB debugger. |
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Programming Languages - Communicate instructions between humans and computers