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https://github.com/facebook/chisel

Chisel is a collection of LLDB commands to assist debugging iOS apps.
https://github.com/facebook/chisel

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Chisel is a collection of LLDB commands to assist debugging iOS apps.

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# Chisel

`Chisel` is a collection of `LLDB` commands to assist in the debugging of iOS apps.



[[Installation](#installation) • [Commands](#commands) • [Custom Commands](#custom-commands) • [Development Workflow](#development-workflow) [Contributing](#contributing) • [License](#license)]



For a comprehensive overview of LLDB, and how Chisel complements it, read Ari Grant's [Dancing in the Debugger — A Waltz with LLDB](http://www.objc.io/issue-19/lldb-debugging.html) in issue 19 of [objc.io](http://www.objc.io/).



## Installation



```shell

brew update

brew install chisel

```



if `.lldbinit` file doesn't exist you can create it & open it by tapping on the terminal



 ```shell

 touch .lldbinit

 open .lldbinit

```



Then add the following line to your `~/.lldbinit` file.



```Python

# ~/.lldbinit

...

command script import /usr/local/opt/chisel/libexec/fbchisellldb.py

```



* Note that if you are installing on an M1 Mac, the path above should be `/opt/homebrew/opt/chisel/libexec/fbchisellldb.py` instead.



Alternatively, download chisel and add the following line to your _~/.lldbinit_ file.



```Python

# ~/.lldbinit

...

command script import /path/to/fbchisellldb.py



```



The commands will be available the next time `Xcode` starts.



## Commands

There are many commands; here's a few:

*(Compatibility with iOS/Mac indicated at right)*



|Command          |Description     |iOS    |OS X   |

|-----------------|----------------|-------|-------|

|pviews           |Print the recursive view description for the key window.|Yes|Yes|

|pvc              |Print the recursive view controller description for the key window.|Yes|No|

|visualize        |Open a `UIImage`, `CGImageRef`, `UIView`, `CALayer`, `NSData` (of an image), `UIColor`, `CIColor`, `CIImage`, `CGColorRef` or `CVPixelBuffer` in Preview.app on your Mac.|Yes|No|

|fv               |Find a view in the hierarchy whose class name matches the provided regex.|Yes|No|

|fvc              |Find a view controller in the hierarchy whose class name matches the provided regex.|Yes|No|

|show/hide        |Show or hide the given view or layer. You don't even have to continue the process to see the changes!|Yes|Yes|

|mask/unmask      |Overlay a view or layer with a transparent rectangle to visualize where it is.|Yes|No|

|border/unborder  |Add a border to a view or layer to visualize where it is.|Yes|Yes|

|caflush          |Flush the render server (equivalent to a "repaint" if no animations are in-flight).|Yes|Yes|

|bmessage         |Set a symbolic breakpoint on the method of a class or the method of an instance without worrying which class in the hierarchy actually implements the method.|Yes|Yes|

|wivar            |Set a watchpoint on an instance variable of an object.|Yes|Yes|

|presponder       |Print the responder chain starting from the given object.|Yes|Yes|

|...              |... and many more!|



To see the list of **all** of the commands execute the help command in `LLDB` or go to the [Wiki](https://github.com/facebook/chisel/wiki).



```Python

(lldb) help

The following is a list of built-in, permanent debugger commands:

...



The following is a list of your current user-defined commands:

...

```



The bottom list contains all the commands sourced from `Chisel`.



You can also inspect a specific command by passing its name as an argument to the help command (as with all other `LLDB` commands).



```

(lldb) help border

Draws a border around . Color and width can be optionally provided.



Arguments:

  ; Type: UIView*; The view to border.



Options:

  --color/-c ; Type: string; A color name such as 'red', 'green', 'magenta', etc.

  --width/-w ; Type: CGFloat; Desired width of border.



Syntax: border [--color=color] [--width=width] 

```



All of the commands provided by `Chisel` come with verbose help. Be sure to read it when in doubt!



## Custom Commands

You can add local, custom commands. Here's a contrived example.



```python

#!/usr/bin/python

# Example file with custom commands, located at /magical/commands/example.py



import lldb

import fbchisellldbbase as fb



def lldbcommands():

  return [ PrintKeyWindowLevel() ]



class PrintKeyWindowLevel(fb.FBCommand):

  def name(self):

    return 'pkeywinlevel'



  def description(self):

    return 'An incredibly contrived command that prints the window level of the key window.'



  def run(self, arguments, options):

    # It's a good habit to explicitly cast the type of all return

    # values and arguments. LLDB can't always find them on its own.

    lldb.debugger.HandleCommand('p (CGFloat)[(id)[(id)[UIApplication sharedApplication] keyWindow] windowLevel]')

```



Then all that's left is to source the commands in lldbinit. `Chisel` has a python function just for this, _loadCommandsInDirectory_ in the _fbobjclldb.py_ module.



```Python

# ~/.lldbinit

...

command script import /path/to/fbobjclldb.py

script fbobjclldb.loadCommandsInDirectory('/magical/commands/')



```



There's also builtin support to make it super easy to specify the arguments and options that a command takes. See the _border_ and _pinvocation_ commands for example use.



## Development Workflow

Developing commands, whether for local use or contributing to `Chisel` directly, both follow the same workflow. Create a command as described in the [Custom Commands](#custom-commands) section and then



1. Start `LLDB`

2. Reach a breakpoint (or simply pause execution via the pause button in `Xcode`'s debug bar or `process interrupt` if attached directly)

3. Execute `command source ~/.lldbinit` in LLDB to source the commands

4. Run the command you are working on

5. Modify the command

6. Optionally run `script reload(modulename)`

7. Repeat steps 3-6 until the command becomes a source of happiness



## Contributing

Please contribute any generic commands that you make. If it helps you then it will likely help many others! :D See `CONTRIBUTING.md` to learn how to contribute.



## License

`Chisel` is MIT-licensed. See `LICENSE`.