Advanced Apple Debugging

By Derek Selander

Derek Selander

Copyright 2018 Razeware LLC.

All rights reserved. No part of this book or corresponding materials (such as text, images, or source code) may be reproduced or distributed by any means without prior written permission of the copyright owner.

This book and all corresponding materials (such as source code) are provided on an as is basis, without warranty of any kind, express of implied, including but not limited to the warranties of merchantability, fitness for a particular purpose, and noninfringement. In no event shall the authors or copyright holders be liable for any claim, damages or other liability, whether in action or contract, tort or otherwise, arising from, out of or in connection with the software or the use of other dealing in the software.

All trademarks and registered trademarks appearing in this book are the property of their own respective owners.

"I would like to thank my wife, Brittany, for all her love and support while I silently wept in the fetal position trying to get this book out the door."

Derek Selander

Derek Selander is the author of this book. His interest with debugging grew when he started exploring how to make (the now somewhat obsolete) Xcode plugins and iOS tweaks on his jailbroken phone, both of which required exploring and augmenting programs with no source available. In his free time, he enjoys pickup soccer, guitar, and playing with his two doggies, Jake & Squid.

Chris Belanger is the editor of this book. Chris is the Editor-in-Chief for raywenderlich.com. He was a developer for nearly 20 years in various fields from e-health to aerial surveillance to industrial controls. If there are words to wrangle or a paragraph to ponder, hes on the case. When he kicks back, you can usually find Chris with guitar in hand, looking for the nearest beach. Twitter: @crispytwit.

Matt Galloway is a software engineer with a passion for excellence. He stumbled into iOS programming when it first was a thing, and has never looked back. When not coding, he likes to brew his own beer.

Darren Ferguson is the final pass editor of this book. He is a Software Developer, with a passion for mobile development, for a leading systems integration provider based out of Northern Virginia in the D.C. metro area. When he's not coding, you can find him enjoying life with his wife and daughter trying to travel as much as possible.

Vicki Wenderlich is the designer and artist of the cover of this book. She is Rays wife and business partner. She is a digital artist who creates illustrations, game art and a lot of other art or design work for the tutorials and books on raywenderlich.com. When shes not making art, she loves hiking, a good glass of wine and attempting to create the perfect cheese plate.

Debugging has a rather bad reputation. I mean, if the developer had a complete understanding of the program, there wouldnt be any bugs and they wouldnt be debugging in the first place, right?

Dont think like that.

There are always going to be bugs in your software or any software, for that matter. No amount of test coverage imposed by your product manager is going to fix that. In fact, viewing debugging as just a process of fixing something thats broken is actually a poisonous way of thinking that will mentally hinder your analytical abilities.

Instead, you should view debugging as simply a process to better understand a program. Its a subtle difference, but if you truly believe it, any previous drudgery of debugging simply disappears.

The same negative connotation can also be applied to reverse engineering software. Images of masked hackers stealing bank accounts and credit cards may come to mind, but for this book, reverse engineering really is just debugging without source code which in turn helps you gain a better understanding of a program or system.

There's nothing wrong with reverse engineering in itself. In fact if debugging was a game, then reverse engineering is simply debugging on the difficult setting which is quite a fun setting if youve been playing the game for a while. :]

In this book, you'll come to realize debugging is an enjoyable process to help you better understand software. Not only will you learn to find bugs faster, but youll also learn how other developers have solved problems similar to yours. You'll also learn how to create custom, powerful debugging scripts that will help you quickly find answers to any item that piques your interest, whether its in your code or someone elses.

To follow along with the tutorials in this book, youll need the following:

• A Mac running Mojave (10.14) or later. Earlier versions might work, but they're untested.

• Xcode 10.0 or later. Packaged with Xcode is the latest and greatest version of LLDB, the debugger youll use extensively throughout this book. At the time of this writing, the version of LLDB packaged with Xcode is lldb-1000.11.37.1.

• Python 2.7. LLDB uses Python 2.7 to run its Python scripts. Fortunately, Python 2.7 automatically ships with macOS, as well as with Xcode. You can verify you have the correct version installed by typing python --version in Terminal.

• A 64 bit iOS device running iOS 12 or later, and a paid membership to the iOS development program[optional]. For most chapters in the book, you can run any iOS programs in the Simulator. However, youll get more out of this book by using a 64-bit iOS device to test out certain ideas or suggestions littered throughout the book.

Once you have these items in place, youll be able to follow along with almost every chapter in this book. For certain sections, you'll need to disable the Rootless security feature in order to use some of the tools (i.e. DTrace). This is discussed in Chapter 1.

The art of debugging code should really be studied by every developer. However, there will be some of you that will get more out of this book. This book is written for:

• Developers who want to become better at debugging with LLDB