LLDB Commands

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Execution Commands

Launch a process with no arguments

(lldb) process launch
(lldb) run
(lldb) r

Launch a process with arguments <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

% lldb -- a.out 1 2 3
(lldb) run
...
(lldb) run
...

or:

(lldb) settings set target.run-args 1 2 3
(lldb) run
...
(lldb) run
...

Launch a process with arguments in new terminal window (macOS only)

(lldb) process launch --tty -- <args>
(lldb) pro la -t -- <args>

Launch a process with arguments in existing terminal /dev/ttys006 (macOS only)

(lldb) process launch --tty=/dev/ttys006 -- <args>
(lldb) pro la -t/dev/ttys006 -- <args>

Set environment variables for process before launching

(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

(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

(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

(lldb) process attach --pid 123  
(lldb) attach -p 123

Attach to a process named 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

(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.

(lldb) gdb-remote eorgadd:8000

Attach to a remote gdb protocol server running on the local system, port 8000

(lldb) gdb-remote 8000

Attach to a Darwin kernel in kdp mode on system eorgadd

(lldb) kdp-remote eorgadd

Do a source level single step in the currently selected thread

(lldb) thread step-in
(lldb) step
(lldb) s

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

(lldb) thread step-over
(lldb) next
(lldb) n

Do an instruction level single step in the currently selected thread

(lldb) thread step-inst
(lldb) si

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

(lldb) thread step-inst-over
(lldb) ni

Step out of the currently selected frame

(lldb) thread step-out
(lldb) finish

Return immediately from the currently selected frame, with an optional return value

(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

Set a breakpoint at all functions named main

(lldb) breakpoint set --name main
(lldb) br s -n main
(lldb) b main

Set a breakpoint in file test.c at line 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

(lldb) breakpoint set --method main
(lldb) br s -M main

Set a breakpoint at an Objective-C method: -[NSString stringWithFormat:]

(lldb) breakpoint set --name "-[NSString stringWithFormat:]"
(lldb) b -[NSString stringWithFormat:]

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

(lldb) breakpoint set --selector count
(lldb) br s -S count

Set a breakpoint by regular expression on function name

(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 or .m files

(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

(lldb) breakpoint set --source-pattern regular-expression --file SourceFile
(lldb) br s -p regular-expression -f file

Set a conditional breakpoint

(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

(lldb) breakpoint list
(lldb) br l

Delete a breakpoint

(lldb) breakpoint delete 1
(lldb) br del 1

Watchpoint Commands

Set a watchpoint on a variable when it is written to

(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

(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

(lldb) watchpoint list
(lldb) watch l

Delete a watchpoint

(lldb) watchpoint delete 1
(lldb) watch del 1

Examining Variables

Show the arguments and local variables for the current frame

(lldb) frame variable
(lldb) fr v

Show the local variables for the current frame

(lldb) frame variable --no-args
(lldb) fr v -a

Show the contents of local variable bar

(lldb) frame variable bar
(lldb) fr v bar
(lldb) p bar

Show the contents of local variable bar formatted as hex

(lldb) frame variable --format x bar
(lldb) fr v -f x bar

Show the contents of global variable baz

(lldb) target variable baz
(lldb) ta v baz

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

(lldb) target variable
(lldb) ta v

Display a the variable argc and argv every time you stop

(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

Evaluating a generalized expression in the current frame

(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

In lldb you evaluate a variable declaration expression as you would write it in C:

(lldb) expr unsigned int $foo = 5

Printing the Objective-C description of an object

(lldb) expr -o -- [SomeClass returnAnObject]

or using the po alias:

(lldb) po [SomeClass returnAnObject]

Print the dynamic type of the result of an expression

(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

(lldb) expr -i 0 -- function_with_a_breakpoint()

Calling a function that crashes, and stopping when the function crashes

(lldb) expr -u 0 -- function_which_crashes()

Examining Thread State

Show the stack backtrace for the current thread

(lldb) thread backtrace
(lldb) bt

Show the stack backtraces for all threads

(lldb) thread backtrace all
(lldb) bt all

Backtrace the first five frames of the current thread

(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

(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

(lldb) up
(lldb) frame select --relative=1

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

(lldb) down
(lldb) frame select --relative=-1
(lldb) fr s -r-1

Select a different stack frame using a relative offset

(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

(lldb) register read

Write a new decimal value 123 to the current thread register rax

(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

(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 a space after the command:

(lldb) register read/d

Show all registers in all register sets for the current thread

(lldb) register read --all
(lldb) re r -a

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

(lldb) register read rax rsp rbp

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

(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 a 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

(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 a 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]

(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

(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

(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 macOS only)

(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 macOS 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 macOS 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 macOS only)

(lldb) command script import lldb.macosx.heap
(lldb) cstr_refs CSTRING

Disassemble the current function for the current frame

(lldb) disassemble --frame
(lldb) di -f

Disassemble any functions named main

(lldb) disassemble --name main
(lldb) di -n main

Disassemble an address range

(lldb) disassemble --start-address 0x1eb8 --end-address 0x1ec3
(lldb) di -s 0x1eb8 -e 0x1ec3

Disassemble 20 instructions from a given address

(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

(lldb) disassemble --frame --mixed
(lldb) di -f -m

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

(lldb) disassemble --frame --bytes
(lldb) di -f -b

Disassemble the current source line for the current frame

(lldb) disassemble --line
(lldb) di -l

Executable & Shared Library Query Commands

List the main executable and all dependent shared libraries

(lldb) image list

Look up information for a raw address in the executable or any shared libraries

(lldb) image lookup --address 0x1ec4
(lldb) im loo -a 0x1ec4

Look up functions matching a regular expression in a binary

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 source line information

This one is a bit messy at present:

(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

(lldb) image lookup --type Point
(lldb) im loo -t Point

Dump all sections from the main executable and any shared libraries

(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

Echo text to the screen

(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

(lldb) settings set target.source-map /buildbot/path /my/path

Notes