The LLDB Debugger

GDB to LLDB Command Map

Below is a table of GDB commands with the LLDB counterparts. The built in GDB-compatibility aliases in LLDB are also listed. The full lldb command names are often long, but any unique short form can be used. Instead of "breakpoint set", "br se" is also acceptable.

Execution Commands

GDB LLDB
Launch a process no arguments.
(gdb) run
(gdb) r
(lldb) process launch
(lldb) run
(lldb) r
Launch a process with arguments <args>.
(gdb) run <args>
(gdb) r <args>
(lldb) process launch -- <args>
(lldb) 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
...
% lldb -- a.out 1 2 3
(lldb) run
...
(lldb) run
...
Or:
(gdb) set args 1 2 3
(gdb) run
...
(gdb) run
...
(lldb) settings set target.run-args 1 2 3
(lldb) run
...
(lldb) run
...
Launch a process with arguments in new terminal window (Mac OS X only).
(lldb) process launch --tty -- <args>
(lldb) pro la -t -- <args>
Launch a process with arguments in existing terminal /dev/ttys006 (Mac OS X only).
(lldb) process launch --tty=/dev/ttys006 -- <args>
(lldb) pro la -t/dev/ttys006 -- <args>
Set environment variables for process before launching.
(gdb) set env DEBUG 1
(lldb) settings set target.env-vars DEBUG=1
(lldb) set se target.env-vars DEBUG=1
(lldb) env DEBUG=1
Unset environment variables for process before launching.
(gdb) unset env DEBUG
(lldb) settings remove target.env-vars DEBUG
(lldb) set rem target.env-vars DEBUG
Show the arguments that will be or were passed to the program when run.
(gdb) show args
Argument list to give program being debugged when it is started is "1 2 3".
(lldb) settings show target.run-args
target.run-args (array of strings) =
[0]: "1"
[1]: "2"
[2]: "3"
Set environment variables for process and launch process in one command.
(lldb) process launch -v DEBUG=1
Attach to a process with process ID 123.
(gdb) attach 123 (lldb) process attach --pid 123
(lldb) attach -p 123
Attach to a process named "a.out".
(gdb) attach a.out (lldb) process attach --name a.out
(lldb) pro at -n a.out
Wait for a process named "a.out" to launch and attach.
(gdb) attach -waitfor a.out (lldb) process attach --name a.out --waitfor
(lldb) pro at -n a.out -w
Attach to a remote gdb protocol server running on system "eorgadd", port 8000.
(gdb) target remote eorgadd:8000 (lldb) gdb-remote eorgadd:8000
Attach to a remote gdb protocol server running on the local system, port 8000.
(gdb) target remote localhost:8000 (lldb) gdb-remote 8000
Attach to a Darwin kernel in kdp mode on system "eorgadd".
(gdb) kdp-reattach eorgadd (lldb) kdp-remote eorgadd
Do a source level single step in the currently selected thread.
(gdb) step
(gdb) s
(lldb) thread step-in
(lldb) step
(lldb) s
Do a source level single step over in the currently selected thread.
(gdb) next
(gdb) n
(lldb) thread step-over
(lldb) next
(lldb) n
Do an instruction level single step in the currently selected thread.
(gdb) stepi
(gdb) si
(lldb) thread step-inst
(lldb) si
Do an instruction level single step over in the currently selected thread.
(gdb) nexti
(gdb) ni
(lldb) thread step-inst-over
(lldb) ni
Step out of the currently selected frame.
(gdb) finish
(lldb) thread step-out
(lldb) finish
Return immediately from the currently selected frame, with an optional return value.
(gdb) return <RETURN EXPRESSION>
(lldb) thread return <RETURN EXPRESSION>
Backtrace and disassemble every time you stop.
(lldb) target stop-hook add
Enter your stop hook command(s). Type 'DONE' to end.
> bt
> disassemble --pc
> DONE
Stop hook #1 added.

Breakpoint Commands

GDB LLDB
Set a breakpoint at all functions named main.
(gdb) break main (lldb) breakpoint set --name main
(lldb) br s -n main
(lldb) b main
Set a breakpoint in file test.c at line 12.
(gdb) break test.c:12 (lldb) breakpoint set --file test.c --line 12
(lldb) br s -f test.c -l 12
(lldb) b 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).
(lldb) breakpoint set --method main
(lldb) br s -M main
Set a breakpoint at and object C function: -[NSString stringWithFormat:].
(gdb) break -[NSString stringWithFormat:]
(lldb) breakpoint set --name "-[NSString stringWithFormat:]"
(lldb) b -[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 named count).
(lldb) breakpoint set --selector count
(lldb) br s -S count
Set a breakpoint by regular expression on function name.
(gdb) rbreak regular-expression
(lldb) breakpoint set --func-regex regular-expression
(lldb) br s -r regular-expression
Ensure that breakpoints by file and line work for #included .c/.cpp/.m files.
(gdb) b foo.c:12
(lldb) settings set target.inline-breakpoint-strategy always
(lldb) br s -f foo.c -l 12
Set a breakpoint by regular expression on source file contents.
(gdb) shell grep -e -n pattern source-file
(gdb) break source-file:CopyLineNumbers
(lldb) breakpoint set --source-pattern regular-expression --file SourceFile
(lldb) br s -p regular-expression -f file
Set a conditional breakpoint
(gdb) break foo if strcmp(y,"hello") == 0
(lldb) breakpoint set --name foo --condition '(int)strcmp(y,"hello") == 0'
(lldb) br s -n foo -c '(int)strcmp(y,"hello") == 0'
List all breakpoints.
(gdb) info break
(lldb) breakpoint list
(lldb) br l
Delete a breakpoint.
(gdb) delete 1
(lldb) breakpoint delete 1
(lldb) br del 1

Watchpoint Commands

GDB LLDB
Set a watchpoint on a variable when it is written to.
(gdb) watch global_var (lldb) watchpoint set variable global_var
(lldb) wa s v 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 (lldb) watchpoint set expression -- my_ptr
(lldb) wa s e -- my_ptr
Set a condition on a watchpoint.
(lldb) watch set var 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
(lldb) watchpoint list
(lldb) watch l
Delete a watchpoint.
(gdb) delete 1
(lldb) watchpoint delete 1
(lldb) watch del 1

Examining Variables

GDB LLDB
Show the arguments and local variables for the current frame.
(gdb) info args
and
(gdb) info locals
(lldb) frame variable
(lldb) fr v
Show the local variables for the current frame.
(gdb) info locals
(lldb) frame variable --no-args
(lldb) fr v -a
Show the contents of local variable "bar".
(gdb) p bar
(lldb) frame variable bar
(lldb) fr v bar
(lldb) p bar
Show the contents of local variable "bar" formatted as hex.
(gdb) p/x bar
(lldb) frame variable --format x bar
(lldb) fr v -f x bar
Show the contents of global variable "baz".
(gdb) p baz
(lldb) target variable baz
(lldb) ta v baz
Show the global/static variables defined in the current source file.
n/a
(lldb) target variable
(lldb) ta v
Display a the variable "argc" and "argv" every time you stop.
(gdb) display argc
(gdb) display argv
(lldb) target stop-hook add --one-liner "frame variable argc argv"
(lldb) ta st a -o "fr v argc argv"
(lldb) display argc
(lldb) 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.
(lldb) target stop-hook add --classname MyClass --one-liner "frame variable *this"
(lldb) ta st a -c MyClass -o "fr v *this"

Evaluating expressions

GDB LLDB
Evaluating a generalized expression in the current frame.
(gdb) print (int) printf ("Print nine: %d.", 4 + 5)
or if you don't want to see void returns:
(gdb) call (int) printf ("Print nine: %d.", 4 + 5)
(lldb) expr (int) printf ("Print nine: %d.", 4 + 5)
or using the print alias:
(lldb) print (int) printf ("Print nine: %d.", 4 + 5)
Creating and assigning a value to a convenience variable.
(gdb) set $foo = 5
(gdb) set variable $foo = 5
or using the print command
(gdb) print $foo = 5
or using the call command
(gdb) call $foo = 5
and if you want to specify the type of the variable: (gdb) set $foo = (unsigned int) 5
In lldb you evaluate a variable declaration expression as you would write it in C:
(lldb) expr unsigned int $foo = 5
Printing the ObjC "description" of an object.
(gdb) po [SomeClass returnAnObject]
(lldb) expr -o -- [SomeClass returnAnObject]
or using the po alias:
(lldb) po [SomeClass returnAnObject]
Print the dynamic type of the result of an expression.
(gdb) set print object 1
(gdb) p someCPPObjectPtrOrReference
only works for C++ objects.
(lldb) expr -d 1 -- [SomeClass returnAnObject]
(lldb) expr -d 1 -- someCPPObjectPtrOrReference
or set dynamic type printing to be the default: (lldb) settings set target.prefer-dynamic run-target
Calling a function so you can stop at a breakpoint in the function.
(gdb) set unwindonsignal 0
(gdb) p function_with_a_breakpoint()
(lldb) expr -i 0 -- function_with_a_breakpoint()
Calling a function that crashes, and stopping when the function crashes.
(gdb) set unwindonsignal 0
(gdb) p function_which_crashes()
(lldb) expr -u 0 -- function_which_crashes()

Examining Thread State

GDB LLDB
Show the stack backtrace for the current thread.
(gdb) bt
(lldb) thread backtrace
(lldb) bt
Show the stack backtraces for all threads.
(gdb) thread apply all bt (lldb) thread backtrace all
(lldb) bt all
Backtrace the first five frames of the current thread.
(gdb) bt 5 (lldb) thread backtrace -c 5
(lldb) bt 5 (lldb-169 and later)
(lldb) bt -c 5 (lldb-168 and earlier)
Select a different stack frame by index for the current thread.
(gdb) frame 12 (lldb) frame select 12
(lldb) fr s 12
(lldb) f 12
List information about the currently selected frame in the current thread.
(lldb) frame info
Select the stack frame that called the current stack frame.
(gdb) up (lldb) up
(lldb) frame select --relative=1
Select the stack frame that is called by the current stack frame.
(gdb) down (lldb) down
(lldb) frame select --relative=-1
(lldb) fr s -r-1
Select a different stack frame using a relative offset.
(gdb) up 2
(gdb) down 3
(lldb) frame select --relative 2
(lldb) fr s -r2

(lldb) frame select --relative -3
(lldb) fr s -r-3
Show the general purpose registers for the current thread.
(gdb) info registers
(lldb) register read
Write a new decimal value '123' to the current thread register 'rax'.
(gdb) p $rax = 123
(lldb) register write rax 123
Skip 8 bytes ahead of the current program counter (instruction pointer). Note that we use backticks to evaluate an expression and insert the scalar result in LLDB.
(gdb) jump *$pc+8
(lldb) register write pc `$pc+8`
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.
(lldb) register read --format i
(lldb) re r -f i

LLDB now supports the GDB shorthand format syntax but there can't be space after the command:
(lldb) register read/d
Show all registers in all register sets for the current thread.
(gdb) info all-registers
(lldb) register read --all
(lldb) re r -a
Show the values for the registers named "rax", "rsp" and "rbp" in the current thread.
(gdb) info all-registers rax rsp rbp
(lldb) register read rax rsp rbp
Show the values for the register named "rax" in the current thread formatted as binary.
(gdb) p/t $rax
(lldb) register read --format binary rax
(lldb) re r -f b rax

LLDB now supports the GDB shorthand format syntax but there can't be space after the command:
(lldb) register read/t rax
(lldb) p/t $rax
Read memory from address 0xbffff3c0 and show 4 hex uint32_t values.
(gdb) x/4xw 0xbffff3c0
(lldb) memory read --size 4 --format x --count 4 0xbffff3c0
(lldb) me r -s4 -fx -c4 0xbffff3c0
(lldb) x -s4 -fx -c4 0xbffff3c0

LLDB now supports the GDB shorthand format syntax but there can't be space after the command:
(lldb) memory read/4xw 0xbffff3c0
(lldb) x/4xw 0xbffff3c0
(lldb) memory read --gdb-format 4xw 0xbffff3c0
Read memory starting at the expression "argv[0]".
(gdb) x argv[0]
(lldb) memory read `argv[0]`
NOTE: any command can inline a scalar expression result (as long as the target is stopped) using backticks around any expression:
(lldb) memory read --size `sizeof(int)` `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
(lldb) memory read --outfile /tmp/mem.txt --count 512 0xbffff3c0
(lldb) me r -o/tmp/mem.txt -c512 0xbffff3c0
(lldb) x/512bx -o/tmp/mem.txt 0xbffff3c0
Save binary memory data starting at 0x1000 and ending at 0x2000 to a file.
(gdb) dump memory /tmp/mem.bin 0x1000 0x2000 (lldb) memory read --outfile /tmp/mem.bin --binary 0x1000 0x2000
(lldb) me r -o /tmp/mem.bin -b 0x1000 0x2000
Get information about a specific heap allocation (available on Mac OS X only).
(gdb) info malloc 0x10010d680 (lldb) command script import lldb.macosx.heap
(lldb) process launch --environment MallocStackLogging=1 -- [ARGS]
(lldb) malloc_info --stack-history 0x10010d680
Get information about a specific heap allocation and cast the result to any dynamic type that can be deduced (available on Mac OS X only)
(lldb) command script import lldb.macosx.heap
(lldb) malloc_info --type 0x10010d680
Find all heap blocks that contain a pointer specified by an expression EXPR (available on Mac OS X only).
(lldb) command script import lldb.macosx.heap
(lldb) ptr_refs EXPR
Find all heap blocks that contain a C string anywhere in the block (available on Mac OS X only).
(lldb) command script import lldb.macosx.heap
(lldb) cstr_refs CSTRING
Disassemble the current function for the current frame.
(gdb) disassemble (lldb) disassemble --frame
(lldb) di -f
Disassemble any functions named main.
(gdb) disassemble main (lldb) disassemble --name main
(lldb) di -n main
Disassemble an address range.
(gdb) disassemble 0x1eb8 0x1ec3 (lldb) disassemble --start-address 0x1eb8 --end-address 0x1ec3
(lldb) di -s 0x1eb8 -e 0x1ec3
Disassemble 20 instructions from a given address.
(gdb) x/20i 0x1eb8 (lldb) disassemble --start-address 0x1eb8 --count 20
(lldb) di -s 0x1eb8 -c 20
Show mixed source and disassembly for the current function for the current frame.
n/a (lldb) disassemble --frame --mixed
(lldb) di -f -m
Disassemble the current function for the current frame and show the opcode bytes.
n/a (lldb) disassemble --frame --bytes
(lldb) di -f -b
Disassemble the current source line for the current frame.
n/a (lldb) disassemble --line
(lldb) di -l

Executable and Shared Library Query Commands

GDB LLDB
List the main executable and all dependent shared libraries.
(gdb) info shared
(lldb) image list
Look up information for a raw address in the executable or any shared libraries.
(gdb) info symbol 0x1ec4
(lldb) image lookup --address 0x1ec4
(lldb) im loo -a 0x1ec4
Look up functions matching a regular expression in a binary.
(gdb) info function <FUNC_REGEX>
This one finds debug symbols:
(lldb) image lookup -r -n <FUNC_REGEX>

This one finds non-debug symbols:
(lldb) image lookup -r -s <FUNC_REGEX>

Provide a list of binaries as arguments to limit the search.
Find full souce line information.
(gdb) info line 0x1ec4
This one is a bit messy at present. Do:

(lldb) image lookup -v --address 0x1ec4

and look for the LineEntry line, which will have the full source path and line range information.
Look up information for an address in a.out only.
(lldb) image lookup --address 0x1ec4 a.out
(lldb) im loo -a 0x1ec4 a.out
Look up information for for a type Point by name.
(gdb) ptype Point
(lldb) image lookup --type Point
(lldb) im loo -t Point
Dump all sections from the main executable and any shared libraries.
(gdb) maintenance info sections
(lldb) image dump sections
Dump all sections in the a.out module.
(lldb) image dump sections a.out
Dump all symbols from the main executable and any shared libraries.
(lldb) image dump symtab
Dump all symbols in a.out and liba.so.
(lldb) image dump symtab a.out liba.so

Miscellaneous

GDB LLDB
Echo text to the screen.
(gdb) echo Here is some text\n
(lldb) script print "Here is some text"
Remap source file pathnames for the debug session. If your source files are no longer located in the same location as when the program was built --- maybe the program was built on a different computer --- you need to tell the debugger how to find the sources at their local file path instead of the build system's file path.
(gdb) set pathname-substitutions /buildbot/path /my/path
(lldb) settings set target.source-map /buildbot/path /my/path
Supply a catchall directory to search for source files in.
(gdb) directory /my/path
(No equivalent command - use the source-map instead.)