Debugger - LLDB vs GDB

GDB

Launch a process no arguments.

(gdb) run

(gdb) r

Launch a process with arguments ​​<args>​​.

(gdb) run <args>

(gdb) r <args>

Launch a process for with arguments ​​a.out 1 2 3​​ without having to supply the args every time.

% gdb --args a.out 1 2 3

(gdb) run

...

(gdb) run

...

Launch a process with arguments in new terminal window (Mac OS X only).

Launch a process with arguments in existing terminal /dev/ttys006 (Mac OS X only).

Attach to a process with process ID 123.

(gdb) attach 123

Attach to a process named "a.out".

(gdb) attach a.out

Wait for a process named "a.out" to launch and attach.

(gdb) attach -waitfor a.out

Do a source level single step in the currently selected thread.

(gdb) step

(gdb) s

Do a source level single step over in the currently selected thread.

(gdb) next

(gdb) n

Do an instruction level single step in the currently selected thread.

(gdb) stepi

(gdb) si

Do an instruction level single step over in the currently selected thread.

(gdb) nexti

(gdb) ni

Step out of the currently selected frame.

(gdb) finish

Backtrace and disassemble every time you stop.

GDB

Set a breakpoint at all functions named main.

(gdb) break main

Set a breakpoint in file test.c at line 12.

(gdb) break test.c:12

Set a breakpoint at all C++ methods whose basename is main.

(gdb) break main

(Hope that there are no C funtions named main).

Set a breakpoint at and object C function: -[NSString stringWithFormat:].

(gdb) break -[NSString stringWithFormat:]

Set a breakpoint at all Objective C methods whose selector is count.

(gdb) break count

(Hope that there are no C or C++ funtions namedcount).

List all breakpoints.

(gdb) info break

Delete a breakpoint.

GDB

Set a watchpoint on a variable when it is written to.

(gdb) watch global_var

Set a watchpoint on a memory location when it is written into. The size of the region to watch for defaults to the pointer size if no '-x byte_size' is specified. This command takes raw input, evaluated as an expression returning an unsigned integer pointing to the start of the region, after the '--' option terminator.

(gdb) watch -location g_char_ptr

Set a condition on a watchpoint.

(lldb) watch set var -w write global

(lldb) watchpoint modify -c '(global==5)'

(lldb) c

...

(lldb) bt

* thread #1: tid = 0x1c03, 0x0000000100000ef5 a.out`modify + 21 at main.cpp:16, stop reason = watchpoint 1

frame #0: 0x0000000100000ef5 a.out`modify + 21 at main.cpp:16

frame #1: 0x0000000100000eac a.out`main + 108 at main.cpp:25

frame #2: 0x00007fff8ac9c7e1 libdyld.dylib`start + 1

(lldb) frame var global

(int32_t) global = 5

List all watchpoints.

(gdb) info break

Delete a watchpoint.

GDB

Show the arguments and local variables for the current frame.

(gdb) info args

and

(gdb) info locals

Show the local variables for the current frame.

(gdb) info locals

Show the contents of local variable "bar".

(gdb) p bar

Show the contents of local variable "bar" formatted as hex.

(gdb) p/x bar

Show the contents of global variable "baz".

(gdb) p baz

Show the global/static variables defined in the current source file.

n/a

Display a the variable "argc" and "argv" every time you stop.

(gdb) display argc

(gdb) display argv

Display a the variable "argc" and "argv" only when you stop in the function named main.

(lldb) target stop-hook add --name main --one-liner "frame variable argc argv"

(lldb) ta st a -n main -o "fr v argc argv"

Display the variable "*this" only when you stop in c class named MyClass.

GDB

Show the stack backtrace for the current thread.

(gdb) bt

Show the stack backtraces for all threads.

(gdb) thread apply all bt

Select a different stack frame by index for the current thread.

(gdb) frame 12

List information about the currently selected frame in the current thread.

Select the stack frame that called the current stack frame.

(gdb) up

Select the stack frame that is called by the current stack frame.

(gdb) down

Select a different stack frame using a relative offset.

(gdb) up 2

(gdb) down 3

Show the general purpose registers for the current thread.

(gdb) info registers

Show the general purpose registers for the current thread formatted as signed decimal. LLDB tries to use the same format characters as printf(3) when possible. Type "help format" to see the full list of format specifiers.

Show all registers in all register sets for the current thread.

(gdb) info all-registers

Show the values for the registers named "rax", "rsp" and "rbp" in the current thread.

(gdb) info all-registers rax rsp rbp

Show the values for the register named "rax" in the current thread formatted as binary.

(gdb) p/t $rax

Read memory from address 0xbffff3c0 and show 4 hex uint32_t values.

(gdb) x/4xw 0xbffff3c0

Read memory starting at the expression "argv[0]".

(gdb) x argv[0]

Read 512 bytes of memory from address 0xbffff3c0 and save results to a local file as text.

(gdb) set logging on

(gdb) set logging file /tmp/mem.txt

(gdb) x/512bx 0xbffff3c0

(gdb) set logging off

Save binary memory data starting at 0x1000 and ending at 0x2000 to a file.

(lldb) memory read --outfile /tmp/mem.bin --binary 0x1000 0x1200

(lldb) me r -o /tmp/mem.bin -b 0x1000 0x1200

Disassemble the current function for the current frame.

(gdb) disassemble

Disassemble any functions named main.

(gdb) disassemble main

Disassemble an address range.

(gdb) disassemble 0x1eb8 0x1ec3

Disassemble 20 instructions from a given address.

(gdb) x/20i 0x1eb8

Show mixed source and disassembly for the current function for the current frame.

n/a

Disassemble the current function for the current frame and show the opcode bytes.

n/a

Disassemble the current source line for the current frame.