Showing entries tagged "fridayqna". Full blog index
Debugging a complex problem is tough, and it can be especially difficult when it's not obvious which chunk of code is responsible. It's common to attempt to produce a reduced test case in order to narrow it down. It's tedious to do this manually, but it's also the sort of thing computers are really good at. C-Reduce is a program which automatically takes programs and pares them down to produce a reduced test case. Let's take a look at how to use it.
Markov chains make for a simple way to generate realistic looking but nonsensical text. Today, I'm going to use that technique to build a text generator based on this blog's contents, an idea suggested/inspired by reader Jordan Pittman.
You might have heard the term type erasure. You might have even used type-erased types in the standard library, such as
AnySequence. But what exactly is type erasure and how do you do it yourself? In this article, I'll explore type erasure, why you'd want it, and how to make it happen, a topic suggested by Lorenzo Boaro.
Apple's newest mobile CPU, the A11, brings a new level of heterogeneous computing to iOS, with both high and low performance cores that are always on. With the release of the iPhone X, I set out to see if I could observe these heterogeneous cores in action.
Back in the dark ages of Swift 1, I wrote an article about locks and thread safety in Swift
. The march of time has made it fairly obsolete, and reader Seth Willits
suggested I update it for the modern age, so here it is!
It's fun to re-imagine traditional techniques with a Swift twist. I've implemented a type-safe layer on top of the venerable
NSUserDefaults, and I'm going to discuss my little library today. Credit/blame for this idea goes to local reader José Vazquez, although he inspired it by accident while talking about something else.
Soon after Swift was initially open sourced, I wrote an article about how weak references are implemented
. Time moves on and things change, and the implementation is different from what it once was. Today I'm going to talk about the current implementation and how it works compared to the old one, a topic suggested by Guillaume Lessard.
Swift's error handling is a unique feature of the language. It looks a lot like exceptions in other languages, but the syntax is not quite the same, and it doesn't quite work the same either. Today I'm going to take a look at how Swift errors work on the inside.
In order to work with C APIs, we sometimes need to convert Swift object references to and from raw pointers. Swift's
struct is the standard API for handling this. Today, I'd like to talk about what it does and how to use it.
In my last article
I discussed the basics of Swift's new
protocol, briefly discussed how to implement your own encoder and decoder, and promised another article about a custom binary coder I've been working on. Today, I'm going to present that binary coder.
One of the interesting additions to Swift 4 is the
Codable protocol and the machinery around it. This is a subject near and dear to my heart, and I want to discuss what it is and how it works today.
We're back! During the week of WWDC, I spoke at CocoaConf Next Door, and one of my talks involved a dissection of
objc_msgSend's ARM64 implementation. I thought that turning it into an article would make for a nice return to blogging for Friday Q&A.
Back in the mists of time, before Friday Q&A was a thing, I posted some articles running performance tests on common operations and discussing the results. The most recent one was from 2008, running on 10.5 and the original iPhone OS, and it's long past time to do an update.
Asserts are really useful for checking assumptions in code to ensure that errors are caught early and often. Today, I'm going to explore the assert calls available in Swift and how they're implemented, a topic suggested by reader Matthew Young.
The big tech news this week is that the FBI is trying to force Apple to unlock a suspect's iPhone. One of the interesting points around this story is that the iPhone in question is an older one, an iPhone 5c. Newer phones have what Apple calls the Secure Enclave, which some say protects against requests of this nature; even if Apple wanted to break into your phone, they couldn't. Which then brings up an interesting question I've seen a lot of people asking: what exactly is the Secure Enclave, and what role does it play here?
classes tend to be straightforward for most people new to the language to understand. They work pretty much like classes in any other language. Whether you've come from Objective-C or Java or Ruby, you've worked with something similar. Swift's
structs are another matter. They look sort of like
classes, but they're value types, and they don't do inheritance, and there's this copy-on-write thing I keep hearing about? Where do they live, anyway, and how do they work? Today, I'm going to take a close look at just how
structs get stored and manipulated in memory.
Cocoa's target/action system for responding to controls is a great system for Objective-C, but is a bit unnatural to use in Swift. Today, I'm going to explore building a wrapper that allows using a Swift function as the action.
In case you have been on Mars, in a cave, with your eyes shut and your fingers in your ears, Swift has been open sourced
. This makes it convenient to explore one of the more interesting features of Swift's implementation: how weak references work.
Subtypes and supertypes are a common part of modern programming. Covariance and contravariance tell us where subtypes are accepted and where supertypes are accepted in place of the original type. This shows up frequently in most of the programming most of us do, but many developers are unaware of the concepts beyond a loose instinctual sense. Today I'm going to discuss it in detail.
Welcome to a very delayed edition of Friday Q&A. One of the biggest complaints I see from people using Swift is the
String API. It's difficult and obtuse, and people often wish it were more like string APIs in other languages. Today, I'm going to explain just why Swift's
String API is designed the way it is (or at least, why I think it is) and why I ultimately think it's the best string API out there in terms of its fundamental design.
Today I'm going to go outside my usual set of topics and talk about a fun side project that might broaden your horizons. Or expose my ignorance. A couple of years ago I set out to build a gear warning system for my glider using an Arduino-type system, and I'm going to talk about how it works and what that code looks like.
Grand Central Dispatch is one of the truly great APIs to come out of Apple in the past few years. In the latest installment of the Let's Build series, I'm going to explore a reimplementation of the most basic features of
dispatch_queue, a topic suggested by Rob Rix.
Getting Xcode to display unsmoothed text in its editor has been an ongoing battle which finally required me to write an Xcode plugin to impose my will. Several readers asked me to discuss how it works, which is what I'm going to do today.
are an interesting technology used to increase performance and reduce memory usage. As of OS X 10.10,
got the tagged pointer treatment, and today I'm going to take a look at how it works, a topic suggested by Ken Ferry.
One of the persistent topics of discussion in the world of Swift has been the question of when to use
classes and when to use
structs. I thought I'd contribute my own version of things today.
Outside of Swift 2 news
, one of the exciting announcements to come out of WWDC was that clang's Address Sanitizer is now available directly in Xcode 7. Today I'm going to discuss what it is, how it works, and how to use it, a topic suggested by Konstantin Gonikman.
Apple made a lot of interesting announcements at WWDC this year about the release of Swift 2 and the new features in it, in among various other announcements of little interest. In addition to the announcement that Swift will be made open source, which is a huge deal all by itself, Swift 2 contains a lot of great new features which significantly improve the language. Today I'm going to talk about the most important ones, what they are, and why they're useful.
The Objective-C runtime is at the heart of much Mac and iOS code. At the heart of the runtime is the
objc_msgSend function, and the heart of that is the method cache. Today I'm going to explore how Apple manages resizing and deallocating method cache memory in a thread safe manner without impacting performance, using a technique you probably won't find in textbooks discussing thread safety.
With computer security high on everyone's minds these days, tools that help assess and improve the security of our code are extremely useful. Today I'm going to talk about one such tool,
, which has seen a lot of attention lately and produces some interesting results. I'll discuss how it works and how to use it on your own code.
Swift 1.2 is now available as part of Xcode 6.3, and one of the new APIs it includes allows us to build efficient data structures with value semantics, such as Swift's built-in
Array type. Today, I'm going to reimplement the core functionality of
The other day I ran into an interesting problem: how can you write a C preprocessor macro that removes parentheses surrounding its argument, but leaves the argument alone if no parentheses are present? For today's article, I'm going to share my solution.
Continuing the theme of thread safety from the previous article, today I'm going to explore an implementation of Objective-C's
@synchronized facility in the latest edition of Let's Build. I'm going to build it in Swift, although an equivalent Objective-C version would be much the same.
An interesting aspect of Swift is that there's nothing in the language related to threading, and more specifically to mutexes/locks. Even Objective-C has
@synchronized and atomic properties. Fortunately, most of the power is in the platform APIs which are easily used from Swift. Today I'm going to explore the use of those APIs and the transition from Objective-C, a topic suggested by Cameron Pulsford.
is a useful API that's pervasive in Apple's frameworks, and often sees a lot of use within our own code. I previously explored building
in Objective-C. Today, I want to build it in Swift, but not just another reimplementation of the same idea. Instead, I'm going to take the API and make it faster, better, stronger, and take advantage of all the nice stuff Swift has to offer us.
Zombies are a valuable tool for debugging memory management problems. I previously discussed the implementation of zombies
, and today I'm going to go one step further and build them from scratch, a topic suggested by Шпирко Алексей.
It's been a long time since I wrote a Friday Q&A, but I'm back, with a brand-new post about a brand-new topic: Swift. Over the last few posts, Mike's gone into some detail about what Swift's internal structures looked like, but he's only touched very lightly on what the linker sees when it looks at Swift-containing binaries: mangled symbol names.
Continuing the theme from the previous article
, I'm going to continue exploring implementation details of Swift's memory layout. Today, I'm going to look at the memory layout of generics, optionals, and protocol objects.
Welcome back to another exploration of Swift. Today I'm going to dig into some implementation details and explore how Swift lays out objects and classes in memory.
Roughly six hundred million people have asked me to write something about Swift. I'm hoping to write a series of articles about various aspects of it. For today, I want to start things off by exploring a few Swift features that are interesting and unusual from the perspective of Objective-C, and why I think they're going to be good to have.
Reader Paul Kim pointed out an entry on Michael Tsai's blog about making
. While the comment in the
source code is fascinating and informative, it doesn't quite delve into the detail that some would like to see. Since this is one of my favorite hacks, for today's article I'm going to discuss exactly what's going on there and how it all works.
vulnerability made a big splash a couple of months ago, and rightly so. It could be described as a "memory leak", but it's not the standard kind where a program fails to free allocated memory. Instead, it allowed an attacker to dump memory contents from a remote program nearly at will, potentially leaking private keys, passwords, source code, and other data intended to stay secret. This got me thinking about ways to protect sensitive data against similar attacks. The result is MAParanoidAllocator
, and in this article I'll discuss the implementation.
Welcome back to another Friday Q&A. I apologize for the unannounced hiatus in posts. It's not due to anything interesting, just a shortage of time. Friday Q&A will continue, and I will continue to aim for my regular biweekly postings. For today's article, I have a little story about an
autorelease call that didn't do what it was supposed to do.
Network programming is everywhere these days. It's tough to find an iPhone app that doesn't use the network for something. We also spend a lot of our time abstracted away from the details of networking, using high-level APIs like
NSURLConnection. Today I'm going to walk you through the lowest-level API you can find without diving into the kernel, the POSIX sockets API.
In addition to its many other fine attributes, the Clang compiler also provides a clean API that makes it easy to use its facilities as a library in your own code. Today, I'm going to give a basic introduction to this library and how to use it, a topic suggested by reader Jeffrey Macko.
The Let's Build
articles are my favorite on this blog. Sometimes, though, it's more fun to break things than to build them. Today, I'm going to explore some amusing and unusual ways to break Cocoa.
In this age of REST and HTTP and massive inefficiency in internet communications, the need for custom network protocols is rare. However, it does happen sometimes, and when it does, I want to make sure it's done right. With that aim, I'm going to discuss some guidelines for designing network protocols, a topic suggested by Mike Shields.
Reader Tomas Bouda asks: what's the deal with the
NSObject protocol? There are two
NSObjects in Cocoa, a class and a protocol. Why both? What purpose do they serve? In today's article, I'll explore the answer to this question.
In the previous article on ARM64
, I mentioned that one advantage of the new architecture is the fact that it has twice as many registers, allowing code load data from RAM less often, which is much slower. Reader Daniel Hooper asks the natural question: just why is
RAM so much slower than registers?
Ever since the iPhone 5S was announced a couple of weeks ago
, the world of tech journalism has been filled
with massive quantities
. Unfortunately, good information takes time, and the world of tech journalism is more about speed than accuracy. Today, as suggested by a variety of readers, I'm going to give the rundown of just what 64-bit ARM in the iPhone 5S means for you, in terms of performance, capabilities, and development.
As I promised last time
, today I'm going to discuss a library I've been working on that makes the task of type-checking property lists much less verbose and painful.
Object serialization is a common requirement for saving files to disk, communicating over a network, or simply persisting settings. Today, I'm going to talk about the basics of using property lists for object serialization, a topic suggested by Nicolas Goles.
Dispatch groups are a handy facility for synchronizing multiple tasks, and an anonymous reader suggested them for the subject of today's Let's Build.
Welcome back, and apologies for going silent without warning. Something resembling normality has resumed, and so I hope to also resume something resembling my normal schedule. In any case, for today's article, local reader Michael Manesh suggested that I talk about how you can use (or abuse) C's type system to obtain stronger typing guarantees by creating
structs containing only a single field.
Some people have a favorite color or a favorite food. It may come as no surprise that I have a favorite compiler bug. Today, I'm going to demonstrate it and pick it apart, a topic suggested by reader Daniel Jalkut.
Networking is playing an ever more important role in application development, and Apple's reachability API is a valuable tool in making network-centric apps play nicely with varying real-world conditions. Today I'm going to give an overview of the reachability API, what it does, and how to use it, a suggestion from reader Manuel Diaz.
I thought I'd mix things up a bit today and give my readers a quiz. The C language is perhaps the most popular computer language in existence, but it's also quite odd, and because of that often poorly understood. I'd like to give you a quiz to see how much you know about some of the odd but useful corners of the language.
Our long effort to rebuild Cocoa piece by piece continues. For today, reader Nate Heagy has suggested building
Asserts are a powerful tool for building quality code, but they're often poorly understood. Today, I want to discuss the various options for writing asserts in Cocoa apps and the best ways to use them, a topic suggested by reader Ed Wynne.
It's time to take a turn to some lighter fare, but to a subject that's near and dear to my heart. The fundamental UI component of a Cocoa app is the NSWindow, and there are many different ways to instantiate and manage them, but there is only one correct way: for each type of window, there should be a separate nib file, and a specialized
NSWindowController subclass. I'll walk through what this means and how to do it, a topic suggested by reader Mike Shields.
Last time on Friday Q&A
, I began the reimplementation of parts of
. In that article, I discussed the basic theory, the architecture calling conventions, and presented the assembly language glue code needed for the implementation. Today, I present the Objective-C part of
It's time for another trip into the nether regions of the soul. Reader Robby Walker suggested an article about
NSInvocation, and I have obliged, implementing it from scratch for your amusement. Today I'll start on a guided tour down the hall of horrors that is
MAInvocation, my reimplementation of the
NSInvocation API. It's a big project, so today I'm going to focus on the basic principles and the assembly language glue code, with the rest of the implementation to follow.
Friday Q&A is driven by the readers, and that's especially true today. Reader Matthew Elton
thought that "Let's Build UITableView" would make a good topic for Friday Q&A, but he decided he'd rather implement it himself and write it up rather than wait for me to do it (good move, Matthew). Without further ado, here is Matthew's article an building
, I showed how to build the basic functionality of
. I left out key-value coding, because the implementation of
is complex enough to need its own article. This is that article.
NSObject class lies at the root of (almost) all classes we build and use as part of Cocoa programming. What does it actually do, though, and how does it do it? Today, I'm going to rebuild
NSObject from scratch, as suggested by friend of the blog and occasional guest author Gwynne Raskind.
This is my first guest Friday Q&A article, dear readers, and I hope it will withstand your scrutiny. Today's topic is on Mach exception handlers, something I've recently spent some time exploring on Mac OS X and iOS for the purpose of crash reporting
While there is surprisingly little documentation available about Mach exception handlers, and they're considered by some to be a mystical source of mystery and power, the fact is that they're actually pretty simple to understand at a high level - something I hope to elucidate here. Unfortunately, they're also partially private API on iOS, despite being used in a number of new crash reporting solutions - something I'll touch on in the conclusion.
The hardware and software that our apps run on is almost frighteningly complicated, and there's no better place to see that than in the contortions that the system goes through when we load data from memory. What exactly happens when we load a byte of memory? Reader and friend of the blog Guy English suggested I dedicate an article to answering that question.
Objective-C is a powerful and extremely useful language, but it's also a bit dangerous. For today's article, my colleague Chris Denter suggested that I talk about pitfalls in Objective-C and Cocoa, inspired by Cay S. Horstmann's article on C++ pitfalls
This is something of a followup to my last article, dyld: Dynamic Linking On OS X
, in which I explored how the dynamic linker
does its job. This week, I'm going to recreate the function of both the compiler and the static
linker, building a Mach-O binary completely from scratch with only the help of the assembler.
objc_msgSend function underlies everything we do in Objective-C. Gwynne Raskind, reader and occasional Friday Q&A guest contributor, suggested that I talk about how
objc_msgSend works on the inside. What better way to understand how something works than to build it from scratch? Let's build
In the course of a recent job interview, I had an opportunity to study some of the internals of
dyld, the OS X dynamic linker. I found this particular corner of the system interesting, and I see a lot of people having trouble with linking issues, so I decided to do an article about the basics of dynamic linking. Some of the deeper logic is new to me, so sorry in advance for any inaccuracies.
It's been a bit since I did an article, but I'm back again, with a somewhat off-the-cuff treatment of a very twisted set of code I use to pretend that C has exceptions. I delve into little-known extensions of C, Linux compatibility, and worst of all,
goto, so be warned!
on Friday Q&A, I discussed a hypothetical implementation of the
class. Starting on Mac OS X 10.7 and iOS 5,
uses a new runtime facility called tagged pointers to increase speed and reduce memory usage, the inner workings of which I want to examine today.
NSNumber is a deceptively simple class with some interesting implementation details. In today's edition of Friday Q&A, I'll explore how to build a class that works like
NSNumber, a topic suggested by Jay Tamboli.
Welcome back! After a brief hiatus for WWDC, it's time for another wacky adventure. Today's topic is the new object literals syntax being introduced into Objective-C, which was suggested by reader Frank McAuley.
, I discussed the basics of PLWeakCompatibility in terms of the motivation, the basic hooks used to get the compiler to call our code when handling
variables, and calling through to the original implementations where available. Today, I'm going to discuss the implementation of the zeroing weak reference facility that gets used when the runtime doesn't supply its own
A few weeks ago, I introduced
. This is a small library that can be dropped into an app to enable use of the
qualifier on OSes that don't support it. ARC is officially supported on Mac OS X 10.6 and iOS 4, but
is only available on 10.7 and iOS 5.
adds support for
on those older OSes when using ARC. Today I'm going to discuss how
works on the inside.
Here I am, yet again! This week, I'm continuing where my last article left off, regarding PLCrashReporter and unwinding stack frames on x86_64. In particular, I go into how I got at and used all the various data I discussed in last week's article
, and why some of the existing solutions in the wild weren't suited for our use.
I'm back once again for Friday Q&A. Today I'm going to talk about some work I recently did on PLCrashReporter
, adding support for unwinding stack frames on x86_64. PLCrashReporter was originally targeted solely at iOS, where both ARM and x86-32 (the simulator) make crash reporting relatively straight-forward; we can simply walk the stack via the preserved frame pointer. On x86-64, matters are different, leading to the need to implement support for alternative methods for stack unwinding. This work was sponsored by HockeyApp
, to support their upcoming release
of Mac OS X sandbox-compatible crash reporting. I'll talk about DWARF debugging information, the compact unwind encoding, and stack scanners. I assume at least some knowledge of x86_64 architecture, for simplicity's sake.
I'm back from my hiatus and ready with a fresh journey into the netherworld of Apple's platforms. Today's subject comes from several readers who suggested that I discuss the subtleties of dealing with memory management and nibs, and particularly the differences between the Mac and iOS.
Last time on Friday Q&A
, we discussed how to implement
. Today, I'll repeat the same exercise with
and build an implementation of it from scratch.
Collection classes are ubiquitous in Cocoa apps, but also fairly opaque. Today, at the suggestion of Matthew Elton, I'm going to take a look at how
NSMutableArray works behind the scenes by building a replacement for it from scratch.
Last time on Friday Q&A
, I started talking about implementing a ring buffer using virtual memory tricks to mirror memory. The first article concentrated on those virtual memory tricks. Today, I'm going to fill out the second half of the puzzle and show how to implement the ring buffer on top of the mirrored memory allocator we developed. If you haven't read the previous article
yet, I strongly recommend you so so, otherwise the memory mirroring is likely to be confusing.
Playing with virtual memory is always fun, and one place where it can be put to good use is in building a ring buffer. A ring buffer is a way to implement a FIFO queue of data, and using virtual memory tricks to mirror multiple copies of the same data can make the implementation simpler and better by virtually concatenating noncontiguous data. Readers Jose Vazquez and Dylan Lukes suggested that I explore the building of such a construct. Today I will talk about how to implement the virtual memory tricks, and then in part II I will show how to implement the ring buffer on top of them.
It's once again time to dive into bizarre programming arcana. In today's article, I want to look at the details of fork-safe code, why the restrictions are present, and why you might care, a topic suggested by Ben Mitchell.
Hi again, readers of NSBlog! This is my first guest post of 2012, and also my first one writing the introduction myself. I plan to do posts every two weeks, alternating with Mike's to bring back the once-a-week format. This week, at my own suggestion, I'm doing a historical piece on the original programming environment for Macs: The Mac Toolbox. Time for a trip down memory lane!
We've spent the last few weeks talking about disassembling executables and how to read the result. Today, I want to wrap up that discussion with a look at a powerful third-party disassembly tool called Hopper.
Gwynne finishes off her series on analyzing assembly code with a look at ARM assembly, for all of your iOS needs. Gwynne will be contributing the occasional article in the future as well as a guest author, without my introductions. Watch the Author field at the top of the post to see who's writing what. Without further ado, let's take a look at ARM.
Today I have the pleasure to present the followup to last week's guest post. Gwynne Raskind
returns to complete her in-depth analysis of the assembly code generated by a small sample program.
As a small change of pace, today's post is written by guest author Gwynne Raskind
. My last post touched a bit on disassembling object files, and Gwynne wanted to dive deeply into just how to read the output in detail. Without further ado, I present her wonderful in-depth look at reading
Being able to see all stages of your work can be immensely helpful when debugging a problem. Although you can get a lot done only looking at the source code and the app's behavior, some problems benefit immensely from being able to inspect the preprocessed source code, the assembly output from the compiler, or the final binary. It can also be handy to inspect other people's binaries. Today, I want to talk about various tools you can use to inspect binaries, both your own and other people's, a topic suggested by Carlton Gibson.
Last time, I talked about my crazy hack that misuses the Objective-C message forwarding machinery to do block proxying
. This allows writing code that interposes in front of an arbitrary block to intercept its arguments, manipulate its return value, etc. Today, I want to present an exanmple of using this hack which almost verges on the practical. Specifically, I'm going to discuss how to use it to build a generalized block memoization facility.
Here at Friday Q&A, I pride myself on occasionally taking my readers to places where normal people dare not tread. Today is one of those days. This is not a reader suggested topic, but today I want to talk about a fun hack I came up with that allows proxying block invocations in much the way that one can proxy Objective-C messages.
Happy iPhone Day to all! For those of you stuck waiting in line or waiting for the delivery guy, never fear, for I have the solution to your pain. For today's topic, Jon Shier suggested that I talk about the new features in Grand Central Dispatch in Lion and iOS 5.
Since the moment Apple announced it, readers have asked me to write about Automatic Reference Counting, or ARC. Today is the day. I'll talk about Apple's new memory management system, how it works, and how to get the most out of it.
Last time, I discussed how to build
NSAutoreleasePool and how it works internally. Today, I'm going to carry that theme forward by building an implementation of Cocoa reference counting with
release, a topic suggested by David Dunham.
It's that time again: time for more programming craziness. Dallas Brown suggested that I talk about how
NSAutoreleasePool works behind the scenes. I decided that the best way to do that would be to simply reimplement it, and that is what I'll discuss today.
The inevitable rotation of the Earth means that it's once again time for another Friday Q&A. For today's edition, Jose Vazquez suggested that I discuss namespaced constants and functions in C.
You're happily writing code one day, click Build, and suddenly the dreaded warning appears:
warning: no '-fooMessage' method found (Messages without a matching method signature will be assumed to return 'id' and accept '...' as arguments.) You double-check your code and your method name is correct, so you shrug and move on. A few hours later, your program starts misbehaving strangely. What's going on? Today, I'll explore the mysterious world of Objective-C method signature mismatches, a topic suggested by an anonymous reader.
It is once again that Fridayest of all days, and time for another Friday Q&A. For today's fountain of technical goodness, reader Jay Tamboli has suggested that I discuss how to write unit tests.
Notifications in Cocoa are extremely useful and are pervasive in Cocoa programming. Unfortunately, a lot of Cocoa programmers see the notification system as something of a black box: a notification is posted, Stuff Happens, and somehow the observer gets notified. Fortunately, the Stuff that Happens is actually pretty simple, and to explore it, I'm going to reimplement an
NSNotificationCenter workalike from scratch to illustrate how it all works, a topic suggested by Dylan Copeland.
It has been said that programming is simply the art of debugging an empty file. While this is a bit of a narrow minded view of things, the fact is that debugging is hugely important to any serious programming. There are a lot of different ways to debug programs, ranging from writing logs to blinking a light to simply inspecting the contents of memory on a crashed system. However, the debugger is one of the most powerful tools for debugging, as you might expect, since it allows deep inspection and modification of a running program without having to anticipate your debugging needs in advance. Although
lldb, the new debugger from the LLVM project, is quickly gaining functionality, the gold standard for debugging Cocoa apps is still
gdb. Today I'm going to discuss how to use
gdb and various tips and tricks for getting the most out of it, a topic suggested by Luis de la Rosa.
Blocks are perhaps the most significant new language feature introduced by Apple in years, and I've written a lot about them before. The new C++ standard, C++0x, introduces lambdas, a similar feature. Today, I want to discuss the two features and how they are alike and how they differ, a topic suggested by David Dunham.
It's Friday again, that Fridayest of days, and this week that means it's time for another Friday Q&A. Samuel Goodwin suggested discussing how
NSZombie works, and that's the topic I will discuss today.
It's a week late, but it's finally time for the latest edition of Friday Q&A. About a year ago, I wrote about converting blocks into function pointers
by building code at runtime. This was an interesting exercise, but ultimately impractical due to various limitations. In the meantime, I wrote MABlockClosure
, a more robust and usable way of doing the same thing, but I never posted about it. Landon Fuller suggest I discuss how it works, and so that is what I will talk about today.
Greetings, salutations, and welcome to another edition of Friday Q&A, the Fridayest source of information on the internet. This week, friend of the blog Jose Vazquez had the idea of discussing miscellaneous compile-time tips and tricks in C/Objective-C, like useful preprocessor techniques and compile-time asserts.
Happy April Fool's Day to all my readers, and welcome to one web site which won't irritate you all day with bizarre practical jokes. Instead, I bring you another edition of Friday Q&A. In this edition, I will discuss various ways of handling signals in Mac programs, a topic suggested by friend of the blog Landon Fuller
It's time for another crazy edition of Friday Q&A. Today, Paul Kim
has suggested that I give a tour of OSAtomic, OS X's built-in low-level functions for lockless thread-safe operations. Given the announcement Wednesday of the dual-core iPad 2, this was a particularly prescient suggestion on his part.
We're back to our regular schedule at last. For today's edition, I'm taking a break from the usual reader-driven format to discuss a topic of my own choosing: compound literals in C99.
Welcome to the first Friday Q&A of the new year. For the first post of
0x7DB, I decided to write about practical floating point, a topic suggested by Phil Holland.
The year is almost over, but there's time for one last Friday Q&A before 2011 comes around. For today's post, fellow Amoeba Dan Wineman suggested that I discuss tricks for writing macros in C.
Merry holidays, happy winter, and a joyous Friday Q&A to you all. Camille Troillard suggested that I discuss how to create custom object memory allocators in Objective-C, and today I'm going to walk through how to accomplish this and why you might want to.
It's once again time for a brand new edition of Friday Q&A. This week, I'm going to talk about accessors, and how to properly deal with memory management and thread safety when creating them, a topic suggested by Daniel Jalkut
Friday Q&A is back! I had some very important slacking to take care of for the past couple of months, but now I'm ready to resume business as usual. For this return to Friday Q&A, I'm going to talk about how to create Objective-C classes at runtime, a topic suggested by Kevin Avila. This topic is meaty enough that this will be a two-parter; today's post will talk about the basics of how to create classes at runtime, and then the next one will discuss uses for such classes and how to take advantage of them.
Welcome back to another word-laden edition of Friday Q&A. About a year ago, I wrote a post on defensive programming
. That post covered defensive programming in a general sense, and Scott Gould has requested that I write one specific to various standard Cocoa practices, which is what I will be talking about today.
Welcome back to another frightening edition of Friday Q&A. This time around, friend and local OS X coder Jose Vazquez
has suggested that I discuss how to implement
in Objective-C classes.
It's time for another friendly edition of Friday Q&A. For my last Friday Q&A, I talked about
MAZeroingWeakRef and how it's implemented for pure Objective-C objects. For this one, I'm going to discuss the crazy hacks I implemented to make it work with toll-free bridged CoreFoundation objects as well.
It's that time of the biweek again. For this week's Friday Q&A, Mike Shields has suggested that I talk about weak references in Objective-C, and specifically zeroing weak references. I've gone a bit further and actually implemented a class that provides zeroing weak references in Objective-C using manual memory management.
Welcome back to another Friday Q&A. This week I'm departing from my usual user-driven format to present a class I've written for what I'm calling "background timers", and discuss potential uses for it.
Welcome back to a late edition of Friday Q&A. WWDC pushed the schedule back one week, but it's finally time for another one. This week, I'm going to discuss the implementation of equality and hashing in Cocoa, a topic suggested by Steven Degutis.
Welcome back to another edition of Friday Q&A. For this week's post, I'm going to talk about three somewhat obscure collections classes that were introduced to Cocoa in 10.5:
NSMapTable, a topic suggested by Phil Holland.
Welcome back to another Friday Q&A. This week, Quentin Carnicelli (who is heavily involved in generating my paychecks) has suggested that I talk about things that every Apple programmer should know. In other words, common Cocoa design and implementation decisions that I'd prefer Apple not to make.
Happy iPad 3G day to everyone. Whether you're waiting in line, waiting for the delivery guy, or just pining at home like I am, you can fill your idle moments with another edition of Friday Q&A. This week, Filip van der Meeren has suggested that I discuss retain cycles and how to deal with them.
Welcome to another chilling edition of Friday Q&A. While I hope to be soaring over the scenic Shenandoah Valley on this fine Friday, I have taken the precaution of preparing my post in advance, so that you may see it even while I am incommunicado. Such is the magic of the modern world. This week, Michael Crawford has suggested that I give in example of implementing a custom control in Cocoa.
Last week I discussed the various options available in Objective-C for enumerating over a collection
This week I'm going to finish up the discussion of enumeration with a guide on how to implement Fast Enumeration in your own program.
Welcome back to another edition of Friday Q&A. Preston Sumner has suggested that I talk about different ways of enumerating over collections in Cocoa, and how to implement Fast Enumeration. This will be a two part series: this week I will look at the different enumeration techniques and their pros and cons, and then next week I will take you through implementing Fast Enumeration on a custom object.
I'm back in action at last, so it's time for another Friday Q&A. This week, both someone named "charles" and Brian Olsen have suggested that I talk about OpenCL, so I'm going to go through the basics of what OpenCL is and how to do some simple computation with it.
Welcome back to another thrilling edition of Friday Q&A. This week I want to extend my discussion from last week
about futures, and talk about compound futures, an extension to the basic futures system that I developed previously.
Welcome back to another shiny edition of Friday Q&A. Guy English
suggested taking a look at implementing futures in Objective-C using blocks, and for this week's post I'm going to talk about the futures implementation that I built.
It's another Friday and another Friday Q&A. For this week's post, Joshua Pokotilow has suggested that I talk about character encodings, so I want to give a basic tour of just what a character encoding is, how it works, and useful details about common encodings.
Welcome to another edition of Friday Q&A, where deep technical talk and complete insanity combine! This week, I'm going to take a quick break from my usual reader-driven format and talk about a little toy I built earlier in the week, an adapter between blocks
and more traditional function-pointer-based callback systems.
The Earth has moved 6.9 degrees around the Sun since my last post, which means it's time for another edition of Friday Q&A. This 6.9-degree segment, Guy English has suggested that I talk about the use of continuation passing style to simplify error returns in Objective-C code.
It's that time of the week again. For this week's Friday Q&A Mike Shields has suggested that I talk about method replacement and method swizzling in Objective-C.
It's been a week, and once again, it's time for a Friday Q&A. For this week's edition, I'm going to talk about how toll-free bridging works, a topic suggested by Jonathan Mitchell.
Welcome to another Friday Q&A. I survived my travel and am (just barely) ready to write another exciting edition. This week's topic comes from Gwynne
, who asked why Objective-C only uses heap objects, and no stack objects.
It's that time of the week again. No, it's not just time to go get drunk, but time for Friday Q&A! This week's topic, suggested by Christopher Lloyd of Cocotron
(a really neat open source project that lets you write Objective-C/Cocoa code for non-Mac platforms like Windows), is
, a little-known, poorly-understood, but handy Foundation class.
It's the first Friday of the new year, and that means it's time for the first Friday Q&A of 2010. This week, I'm taking Dave DeLong's suggestion of talking about
It's hard to believe that it's been a full year (minus a day) since my first Friday Q&A
. It's become more successful than I thought possible, and many kind and obviously deluded people have said great things about it to me. Since I'm feeling lazy this week, I thought I'd pull up some highlights from the past year rather than write anything new.
It's time for another wintry edition of Friday Q&A. From the comfort of your toasty-warm homes, you can read about building an HTTP server using Grand Central Dispatch, a topic suggested by Steven Degutis.
It's Friday again and time for another Friday Q&A. This week I'm going to discuss a framework for creating generators in Objective-C. I'm indulging myself a bit with this, because nobody suggested it, but nothing in my suggestion bank inspired me this time around, so I decided to go with something of my own.
I'm afraid that I ran out of time this week and wasn't able to put together a real Friday Q&A. However, as a preview of what I'll be talking about next week, check out the MAGenerator
project in my public subversion repository.
It's Friday again, and that means another Friday Q&A. This week, Guy English proposed talking about a blocks-based object system, and that is what I will do. The system I've developed is a rudimentary system for doing object-oriented programming in pure C (plus blocks), and I'll discuss how it works and how to use it.
It's that time of the week again. This week I'm going to discuss defensive programming, a topic suggested by Ed Wynne.
It's time for another Friday Q&A. I hope everyone who had a chance to go to C4 had a good time and is back home safe and sound. This week I'm going to discuss singletons, both how to make them and when to use them, as suggested by Jon Trainer.
Welcome back to another Friday Q&A. I'm off to C4 today (hope to see you there!) but I've prepared this in advance so everyone stuck at home (or worse, work) can at least have something interesting to read. Over the past four weeks I've introduced Grand Central Dispatch and discussed the various facilities it provides. In Part I
I talked about the basics of GCD and how to use dispatch queues. In Part II
I discussed how to use GCD to extract more performance from multi-core machines. In Part III
I discussed GCD's event dispatching mechanism, and in Part IV
I took care of various odds and ends that I hadn't covered before. This week I'm going to examine a practical application of using GCD to speed up the production of thumbnails for a large quantity of images, a topic suggested by Willie Abrams.
It's that time of the week again. Over the past three weeks I've introduced you to the major pieces Grand Central Dispatch, an exciting new API for parallel processing and event handling in Snow Leopard. The first week
I covered basic concepts and dispatch queues. The second week
I discussed how to use dispatch queues for parallel processing on multi-core computers. The third week
I covered GCD's event handling system. This week I'm going to cover various odds and ends which I didn't get to before: dispatch queue suspension and targeting, semaphores, and one-time initialization.
Welcome back to another Friday Q&A. This week I continue the discussion of Grand Central Dispatch from the past two weeks. In the last two weeks I mainly focused on dispatch queues. This week I'm going to examine dispatch sources, how they work, and how to use them.
Welcome back to Friday Q&A. Last week I discussed the basics of Grand Central Dispatch, an exciting new technology in Snow Leopard. This week I'm going to dive deeper into GCD and look at how you can use GCD to take advantage of multi-core processors to speed up computation. This post assumes that you've read last week's edition
, so be sure to do that if you haven't already.
Welcome back to Friday Q&A. This week's edition lines up with Apple's release of Snow Leopard, so I'm going to take this opportunity to open up the discussion on previously NDA'd technologies and talk about some of the cool stuff now available in Snow Leopard. For this week I'm going to start what I plan to be an ongoing series on Grand Central Dispatch, a topic suggested by Chris Liscio
Welcome to another Friday Q&A, where all references are strong and all values are above average. This week I'm going to talk about how to write macros and functions that take variable arguments in C, as suggested by Damien Sorresso.
Welcome back to another edition of Friday Q&A. I'm back from my break and ready to bring you more programming goodies. This week I want to take Landon Fuller's suggestion to write a followup to my original Friday Q&A on blocks
now that the design is finalized and code available for them.
Greetings and welcome back to Friday Q&A. This week I'm going to discuss some tips and tricks for using
printf-style format strings in C, as suggested by Kevin Avila.
Here at last is the conclusion to Friday Q&A's three-part series on C type specifiers. The first week
. Last week
I discussed the basics of
and why it's not very useful. This week I'm going to finish up by discussing the use of
in a multithreaded context.
Welcome to another edition of Friday Q&A. Last week
I began to talk about type qualifiers in C, and discussed the meaning and use of the
qualifiers. This week I will continue with a discussion of the third qualifier,
Welcome back to another warm and fuzzy edition of Friday Q&A. This week I'm going to discuss the use of type qualifiers in C, a subject suggested by Nate Vander Wilt.
Welcome back to another Friday Q&A. Now that WWDC is behind us, I'm back on track to bring you more juicy highly-technical goodness. Maybe I can even get back to doing one a week.... This week I'm going to take André Pang's suggestion of discussing process memory statistics (the stuff you see in Activity Monitor or
top) in Mac OS X.
Welcome back to another late Friday Q&A. My apologies to all of my readers for missing last week's edition. Some family events beyond the scope of this blog prevented me from writing one. And I should probably point out right now that WWDC is almost certainly going to prevent me from writing one next week. This week, however, I do have a post, and I'm going to be talking about Valgrind as suggested by Landon Fuller.
Welcome back to another cromulent Friday Q&A. After taking a few weeks off I intend to resume the regular schedule. We'll see how far that intention takes me, but I'm hopeful. This week I'm going to take Daniel Jalkut's suggestion to discuss class loading and initialization in Objective-C.
It's Friday again, and that means another Friday Q&A. As promised, this week's edition will pick up where last week's left off. Last week
I discussed the basics of generating code at runtime using LLVM. This week I'm going to build on that base and show how to use LLVM to perform fast forwarding in Objective-C.
Welcome back to another heart-pounding edition of Friday Q&A. Phil Holland and Ed Wynne both suggested that I do something with LLVM, and so I'm going to discuss how to generate and call code at runtime using LLVM. This week I'm going to talk about the basics needed to get up and running with code generation, and then next week in Part 2 I'm going to show how you can use this technique to build a fast Objective-C trampoline object.
Welcome to another Friday Q&A, where all the women are strong, all the men are good-looking, and all the programmers are above average. This week, Phil Holland has suggested that I dissect an interesting piece of code from one of my screensavers, so we're going to take a look at ChemicalBurn
's multithreaded routing code.
Welcome back to another exciting Friday Q&A. This week I'm going to continue the series on the Objective-C runtime. Yuji Tachikawa suggested talking about how
@dynamic properties work in CoreData and I'm going to take that and expand it to talk about message forwarding in general.
Welcome back to another Friday Q&A. This week I'd like to take Joshua Pennington's idea and elaborate on a particular facet last week's topic of the Objective-C runtime, namely messaging. How does messaging work, and what exactly does it do? Read on!
Welcome back to another Friday Q&A, on another Friday the 13th. This week I'm going to take Oliver Mooney's suggestion and talk about the Objective-C runtime, how it works, and what it can do for you.
Welcome back to another exciting Friday Q&A. This week's topic, suggested by Ed Wynne, will be an overview of the Clang Static Analyzer and an example of how to use it.
Welcome back to Friday Q&A, a bit early this week since I won't be around to post it at the usual time. This week I'm going to cheat a little bit and use a topic that I "suggested" myself. I'll be talking about what I like to call "holistic optimization", which is essentially how to look at optimization within the context of your entire project, rather than bit-swizzling, loop unrolling, and other micro-optimizations.
Welcome back to another Friday Q&A. This week I'm going to take Erik's (no last name given) suggestion from my interprocess communication post
and expand a bit on Distributed Objects, what makes it so cool, and the problems that it has.
Welcome back to Friday Q&A, which this week is also Friday the Thirteenth! Be especially careful, as this is the first of two consecutive Friday the Thirteenths. For this first Friday the Thirteenth I'm going to talk about parallel software design using an "operations" approach (think NSOperation), as suggested by Nikita Zhuk way back when I first started this whole thing.
Welcome back to Friday Q&A.; This week I'm taking Jeff Johnson's idea to discuss optimization and profiling tools.
Welcome back to another exciting Friday Q&A.; This week I'll be taking Jonathan Mitchell's suggestion to talk about code injection, the various ways to do it, why you'd want to, and why you wouldn't want to.
Welcome to the first Friday Q&A; of the new Presidential administration. Unlike Mr. Obama, I'm afraid of change and so this week's edition will be just like all the other ones. This week I'll be taking Jonathan Mitchell's suggestion to talk about how Key-Value Observing (KVO) is actually implemented at the runtime level.
Happy Friday to everyone, and welcome back to another Friday Q&A. This week I'll be taking Eren Halici's suggestion to discuss the various ways to do interprocess communication on OS X.
Greetings one and all. I caught my mistaken writing of "2008" in this blog post title almost instantly instead of only noticing after I'd already posted it like I did last week, so the year must be coming along. Welcome to the second Friday Q&A of 2009 (and only the fourth in all human history!) where I'll be taking Ed Wynne's suggestion and talking about the various meanings and implications of thread safety as they apply to Mac OS X system frameworks.
It's a new year, and that means a new Friday Q&A! This week I'm going to take Steven Degutis's suggestion and discuss the ups and downs of using private APIs.
Welcome to another Friday Q&A. This week I thought I would take fellow amoeboid Jeff Johnson's suggestion and talk about blocks in Objective-C.
Great response last week. This week I'm going to merge Sam McDonald's question about how I got into doing multithreaded programming and Phil Holland's idea of talking about the different sorts of parallelism available.
at 2008-12-13 05:00
In an effort to liven up the blog a bit, I thought I would start soliciting topics from the readership. Given the large number of comments on certain past posts and the couple hundred unique hits to my RSS feed URL every day, I'm hoping that this might just work out.