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Objective-C Internals
Rust API Bindings

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Rust API Bindings: CFStringGetBytes Is Hard, Part 2
Rust API Bindings: CFStringGetBytes Is Hard, Part 1
Rust API Bindings: Core Foundation Memory Management and Mutability

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January 2024

Rust API Bindings: CFStringGetBytes Is Hard, Part 2

Using Rust’s features, we can provide API bindings to CFStringGetBytes that prevent unsupported argument combinations at the call site to fix the problems identified in the previous post.

December 2023

Rust API Bindings: CFStringGetBytes Is Hard, Part 1

Designing a "correct by default" interface for CFStringGetBytes is surprisingly complex, as many of its behaviors are encoding-dependent.
Rust API Bindings: Core Foundation Memory Management and Mutability

The design patterns used by Core Foundation for memory management and mutability fit surprisingly well in idiomatic Rust. This post shares an overview of how I reached this conclusion the hard way.
Rust API Bindings: Core Foundation Signed/Unsigned Conversion

Handling CFIndex/usize (signed/unsigned) conversion is important in crafting idiomatic Rust API bindings. I looked at how Apple handled this conversion between Core Foundation and Foundation, and between Foundation and Swift to help inform the direction for my Core Foundation crate.

October 2023

Objective-C Internals: Release

Although release is "just" the logical inverse of retain, its implementation is much more complex, primarily due to the ARM synchronization model. This post explores the unique aspects of the release implementation (relative to retain), focusing on the memory ordering requirements on ARM.

July 2023

Objective-C Internals: Retain

Objective-C memory is managed through a reference counting scheme, which has evolved from a relatively simple API into a sophisticated, highly-optimized implementation while maintaining source and ABI compatibility.

June 2023

Home Lab: The Accidental System

I didn’t set out to build a home lab, but one emerged anyway. This post shares the choices I made to solve one-off problems and how those choices accumulated into a surprisingly large collection of hardware and services.
Objective-C Internals: Associated References

A comparison of Apple’s Associated References implementation and one I wrote for historical context, with additional notes about use with tagged pointer objects and what the assign association policy actually does.

May 2023

Site Refresh

The site has undergone extensive updates, receiving a new layout, theme, and art, along with a few usability improvements. With this time-consuming investment complete, I’ll again have bandwidth to regularly post new technical content.

March 2023

Objective-C Internals: Tagged Pointer Objects

Tagged pointer objects (a private runtime feature) optimize performance by storing an object’s data in its pointer value, eliminating the object’s heap allocation. This post looks at the implementation of NSNumber to highlight the use of and implications of this optimization.
Objective-C Internals: Non-Fragile Instance Variables

Objective-C instance variables may impact ABI stability. In Objective-C 2, Apple introduced a "non-fragile" layout to preserve ABI stability across some types of changes to a class’s instance variables.

February 2023

Objective-C Internals: Unrealized Classes (and Toll-Free Bridging)

Objective-C unrealized classes may refer to future classes or class stubs. Future classes (a private runtime feature) facilitate toll-free bridging with CoreFoundation. And, class stubs are emitted by the Swift compiler to support interoperability between the stable Swift ABI and Objective-C.

January 2023

Objective-C Internals: The Many Uses of isa

The Objective-C runtime optimizes performance by packing additional information into an object’s isa pointer. This post compares the different packing mechanisms and discusses the various field values stored in the pointer value.
Objective-C Internals: Class Graph Implementation

A brief look at the Objective-C runtime source code, focusing on the definition of object and class types, highlighting how inheritance is implemented, special cases for the root class, and quirks related to metaclass lookup.
Objective-C Internals: Class Architecture

Objective-C has an unique class architecture where classes are objects. Its elegant design enables dynamic method dispatch for all object types through the use of a compiler generated metaclass.

February 2022

Size Matters: An Exploration of Virtual Memory on iOS

An out-of-memory crash while debugging an iOS app led to investigating the iOS virtual memory system and finding the virtual address space size varies across iOS devices. Fixing the debugging workflow required use of the Extended Virtual Addressing entitlement to enable the full 64-bit address space.

Copyright © 2022–2024 Brian T. Kelley.