…explore a very small section of what DTrace is capable of doing by tracing Objective-C code in already compiled applications. Using DTrace to observe iOS frameworks (like UIKit) can give you an incredible insight into how the authors designed their code…

…will be able to interpret that value and display meaningful information to you. For example lldb can interpret: a C int, Objective-C NSObject or a Swift struct, a variable in source code, a register’s value, etc. If you do a quick help po in the lldb console…

…method, but doesn’t know what to call it. In this chapter, you’ll build an LLDB script that will resymbolicate stripped Objective-C functions in a stack trace…

…stop at the start of a function call in order to inspect or modify the parameters without having to actually dive into the assembly. Objective-C and Registers As you learned in the previous section, registers use a specific calling convention. You can take that same knowledge and apply…

…when evaluating JIT code (i.e. Objective-C, Swift, C, etc. code that’s executed through your Python script), you’ve used a small set of APIs to evaluate the code. It’s time to talk about a new class in the lldb Python module, SBValue, and how it can simplify…

Whether you’re using Swift, Objective-C, C++, C, or an entirely different language in your technology stack, you’ll need to learn how to create breakpoints. It’s easy to click on the side panel in Xcode to create a breakpoint using the GUI, but the LLDB console…

…reverse engineering or stumbling upon someone else’s work on GitHub). The starter project directory includes Private.m and Private.h, which contain an Objective-C class called PrivateObjcClass, an NSString constant called SomeStringConstant and a C function called SomeCode. In Terminal, navigate to where you’ve saved the demo code…

…address again: (lldb) process launch -e /dev/ttys027 -- The launch argument e specifies the location of stderr. Common logging functionality, such as Objective-C’s NSLog or Swift’s print function, outputs to stderr — yes, not stdout! You’ll print your own logging to stderr later. Notes will launch after…

…they need to be visually displayed (if it’s an on-screen component, it must inherit from UIView, which inherits from NSObject, meaning Objective-C) DTrace is agnostic to whatever Swift code inherits from whatever class as it’s all the same to DTrace. You can still profile Objective-C…

…input which contains special characters like a dash; otherwise, OptionParser will incorrectly assume that’s an option being passed in. This is important because Objective-C has dashes in instance methods, so you don’t want the dash to be incorrectly interpreted as an option! Using the newly created generateOptionParser…

Look up code for the symbol named mmap. Breakpoints (lldb) b viewDidLoad Creates a breakpoint on all methods named viewDidLoad for both Swift and Objective-C. (lldb) b setAlpha: Creates a breakpoint on either the setAlpha: Objective-C method or the setter of the Objective-C alpha property. (lldb…

UIViewController(CategoryName) methodName]. Search for all UIViewController category methods: (lldb) image lookup -rn '\[UIViewController\(' Searching for the presence of the parenthesis immediately following the Objective-C class name returns category methods for that particular class. Not only does this print out both public and undocumented APIs, but it also gives…

…your LLDB Python scripts using the Python pdb module, which is used for debugging Python scripts. In addition, you can execute your own “normal” Objective-C, Objective-C++, C, Swift, or even other languages code within SBDebugger’s, or SBCommandReturnObject’s, HandleCommand method. In fact, there’s alternative ways…

…code within your own application. To do this, you’re going to call on the help of two awesome functions: dlopen and dlsym. The Objective-C Runtime vs. Swift & C Objective-C, thanks to its powerful runtime, is a truly dynamic language. Even when compiled and running, not even…

…expression -f x -l objc -- This command, cpx, is a convenience command you can use to print out something in hexadecimal format, using the Objective-C context. This will be useful when printing out register contents. Remember, registers aren’t available in the Swift context, so you need…

…visible, depending what the previous state was. Note that isHidden doesn’t know the return type, so you need to cast it to an Objective-C BOOL. The final command, [CATransaction flush], flushes the CATransaction queue. Manipulating the UI in the debugger normally means the screen will not reflect…

Then just choose a number greater than that. Numerous other sections contain UTF-8 strings for different purposes. For example, the __TEXT.__objc_methname section contains Objective-C method names that are referenced directly by your application. The __TEXT.__swift4_reflstr section contains references to Swift’s reflected items. A candidate for Swift runtime…

…just created a new command called cpo. The cpo command will do a normal po (print object), but it’ll use the Objective-C context instead. This is an ideal command to use when you’re in a Swift context, but want to use Objective-C to print…

…allocated Swift/Objective-C object when you don’t know how a property is getting set, i.e. via direct ivar access, Swift inout parameter initialization, Objective-C property setter method, Swift property setter method, hardcoded offset access, or other methods. Monitoring when a hardcoded string is being utilized, such…

…breakpoint it will break twice. Build and run the program. We want the break in the Swift context, so if you broke in the Objective-C context, type c or click the resume button. As expected, the debugger will pause the program on the viewWillAppear(_:) method of MainViewController. Next, take…