Execution Commands
| GDB | LLDB |
|---|---|
| Launch a process with no arguments | |
(gdb) run (gdb) r | (lldb) process launch (lldb) run (lldb) r |
Launch a process with arguments <args> | |
(gdb) run <args> (gdb) r | (lldb) process launch -- <args> (lldb) r <args> |
Launch process a.out with arguments 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 ... |
| Launch a process with arguments in a new terminal window (OS X only) | |
| — | (lldb) process launch --tty -- <args> (lldb) pro la -t -- <args> |
Launch a process with arguments in an existing Terminal window, /dev/ttys006 (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 |
| Set environment variables for process and launch process in one command | |
(lldb) process launch -v DEBUG=1 | |
| Attach to the 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 the 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 the 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 |
| 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 (Note: This will break on any C functions named main.) | (lldb) breakpoint set --method main (lldb) br s -M main |
Set a breakpoint at an Objective-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 (Note: This will break on any C or C++ functions named count.) | (lldb) breakpoint set --selector count (lldb) br s -S count |
| Set a breakpoint by a regular expression on a function name | |
(gdb) rbreak regular-expression | (lldb) breakpoint set --regex regular-expression (lldb) br s -r regular-expression |
| Set a breakpoint by a regular expression on a source file’s 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 |
| 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 to | |
(gdb) watch -location g_char_ptr | (lldb) watchpoint set expression -- my_ptr (lldb) wa s e -- my_ptr Note: 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 (--). |
| 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.outmodify + 21 at main.cpp:16, stop reason = watchpoint 1 frame #0: 0x0000000100000ef5 a.outmodify + 21 at main.cpp:16 frame #1: 0x0000000100000eac a.outmain + 108 at main.cpp:25 frame #2: 0x00007fff8ac9c7e1 libdyld.dylibstart + 1 (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 the local variable bar | |
(gdb) p bar | (lldb) frame variable bar (lldb) fr v bar (lldb) p bar |
Show the contents of the 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 the 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 | |
| — | (lldb) target variable (lldb) ta v |
Display the variables 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 the variables 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 the 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 |
|---|---|
| Evaluate 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 use the print alias: (lldb) print (int) printf ("Print nine: %d.", 4 + 5) |
| Create and assign a value to a convenience variable | |
(gdb) set $foo = 5 (gdb) set variable $foo = 5 Or use the print command: (gdb) print foo= 5 To specify the type ofthe variable: (gdb) set $foo = (unsigned int)` 5 | LLDB evaluates a variable declaration expression as you would write it in C: (lldb) expr unsigned int $foo = 5 |
Print the Objective-C description of an object | |
(gdb) po [SomeClass returnAnObject] | (lldb) expr -O -- [SomeClass returnAnObject] Or use 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 Note: Only for C++ objects. | (lldb) expr -d run-target -- [SomeClass returnAnObject] (lldb) expr -d run-target -- someCPPObjectPtrOrReference Or set dynamic type printing as default: (lldb) settings set target.prefer-dynamic run-target |
| Call a function to stop at a breakpoint in the function | |
(gdb) set unwindonsignal 0 (gdb) p function_with_a_breakpoint() | (lldb) expr -u 0 -- function_with_a_breakpoint() |
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 $rax = 123 | (lldb) register write rax 123 |
| Skip 8 bytes ahead of the current program counter (instruction pointer) | |
(gdb) jump *$pc+8 | (lldb) register write pc $pc+8`` The LLDB command uses backticks to evaluate an expression and insert the scalar result. |
| Show the general-purpose registers for the current thread formatted as signed decimal | |
| — | (lldb) register read --format i (lldb) re r -f i LLDB now supports the GDB shorthand format syntax, but no space is permitted after the command: (lldb) register read/d Note: 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 | (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 no space is permitted after the command: (lldb) register read/t rax (lldb) p/t $rax |
Read memory from address 0xbffff3c0 and show four 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 no space is permitted 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 that any command can inline a scalar expression result (as long as the target is stopped) using back ticks () 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 to a file starting at 0x1000 and ending at 0x2000 | |
(gdb) dump memory /tmp/mem.bin 0x1000 0x2000 | (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 | (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 | |
| — | (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 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. |
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 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 | (lldb) script print "Here is some text" |
| Remap source file pathnames for the debug session | |
(gdb) set pathname-substitutions /buildbot/path /my/path | (lldb) settings set target.source-map /buildbot/path /my/path Note: 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 the local file path instead of the build system file path. |
| Supply a catchall directory to search for source files in | |
(gdb) directory /my/path | (No equivalent command.) |
