New Xcode Build System and BuildSettingExtractor

Last week at WWDC 2017, Apple announced a new build system for Xcode, with an opt-in preview in Xcode 9. The new system is written in Swift and promises to be a significant advance in a number of areas including performance and dependency management. The new system is built on top of the open source llbuild project and lays the foundation for integrating the Xcode build system with the Swift Package Manager.

You opt in to the new build system per project or workspace. To do so in the Xcode 9 beta, open a project file and then go to File > Project Settings… and in the sheet that appears, choose New Build System (Preview) from the Build System popup menu. Note that the menu item will be File > Workspace Settings… if you are working with a workspace.

Project settings sheet with popup menu to select build system

Opt-in to the new build system for a project in File > Project Settings…
(For a workspace use File > Workspace Settings…)

The big news of a new build system made me curious to see if there were any changes I would need to make to BuildSettingExtractor.

Icon for the app BuildSettingExtractor

BuildSettingExtractor helps you move to xcconfig files.

If you are not familiar with it, BuildSettingExtractor is an open source utility that helps you move to using xcconfig files. It reads the build settings embedded in an Xcode project file and extracts the settings into xcconfig files. It can also extract the Xcode help for each build setting to produce automatically documented configuration files. (Read my prior post Generating Xcode Build Configuration Files with BuildSettingExtractor for more about the benefits of using xcconfig files.)

My investigation led me to look more closely at what was changing and what was staying the same when it came to the new build system and build settings in Xcode 9.

When it comes to build settings, there are two big operations: Defining build settings and using build settings.

As developers, we spend our time on the first part, defining build settings1. In a complex project or workspace, this can be an involved process. Defining build settings includes all of the following:

  • Build settings defined for each target and for the project itself
  • Variable substitution to define derived build settings using ${} or $()
  • Conditional build settings based on build configuration, architecture, and SDK
  • Optionally using xcconfig files to define build settings
  • Understanding the well-defined hierarchy of how build settings are inherited and used

In the end, these intricate and flexible mechanisms for defining build settings resolve into a big dictionary of key-value pairs that is passed to the build system.

The build system is what uses the build settings to help direct how it builds a target. The build system coordinates the various tools required, such as the compiler and linker. It uses a target’s build phases and build settings to generate a build product (e.g. app, extension, framework, library). It understands all of a target’s dependencies and builds them as well. The build system is a complicated beastie with a lot of responsibilities and it is what is being modernized beginning in Xcode 9.

Logo of new Xcode build system

New build system.
Same build settings.

On a number of my projects, I’ve switched from the current build system to the new build system in Xcode 9 to investigate. It appears that everything about defining build settings remains unchanged. Moving between the old and new build systems did not cause any build setting changes or recommended changes. The mechanisms for generating that giant bucket of key-value pairs known as build settings seem to be just the same as before.

This is great news. As developers, we don’t need to learn a new complex system for defining build settings. We get to enjoy the benefits of a new, faster, modern build system with our existing build settings left intact.

As the developer of BuildSettingExtractor, this is also great news—no big changes required. After doing some testing and a tweak here and there, BuildSettingExtractor is now updated to work with the Xcode 9 beta. I invite you to check out BuildSettingExtractor and the new build system in Xcode 9. •

1And debugging them.

iOS Device Summary: September 2016 Updates

I’ve updated my iOS Device Summary with hardware announced at the Apple event on September 7, 2016.

Check out the iOS Device Summary page for more info about the idea behind the summary as well as PDF downloads—including optimized files for printing.

A few notes:

Sometimes fall brings new iOS hardware across all product lines. This year, only new iPhone versions were released.

In terms of legacy hardware support, iOS 10 drops support for devices running the A5 and A5X processor. This includes iPhone 4S , which means that there are no devices with a 3.5-inch screen that support iOS 10.

.Don’t feel badly for devices with the A5 chip—they have had a very good run. The iPhone 4S debuted running iOS 5 and iPad 2 debuted with iOS 4.2.1. Both were supported up through iOS 9.

Time will tell if the next version of iOS drops support for A6 and A6X devices. When support for those devices is dropped, iOS devices will be 64-bit only.

In the meantime, of course, it is important to test on older devices running the oldest version of iOS that you support.

I hope you find this version of the chart helpful. •

Chart depicting iOS devices by screen size, processor and supported OS version


tvOS and watchOS Device Summary: April Edition

After updating the popular iOS Device Summary in March, it seemed the beginning of April would be a good time to introduce summaries for devices running the most recently introduced Apple operating systems: tvOS and watchOS.

I hope you find these as useful as I have. •

Chart depicting tvOS devices by screen size, processor and supported OS version

Chart depicting watchOS devices by screen size, processor and supported OS version

iOS Device Summary: Fall 2015 Updates

I’ve updated my iOS Device Summary with hardware announced at the Apple event on September 9, 2015. This edition drops iOS 5 and A4-based devices to make way for iOS 9 and the A9 and A9X.

(This update has taken a little while—I’ve been busy helping to build a new cloud computer at Upthere.  I’m excited to say that we launched yesterday. I encourage you to learn more and join the beta at

Check out the iOS Device Summary page for more info about the idea behind the summary as well as PDF downloads—including optimized files for printing.

The biggest news this fall is the iPad Pro, which introduces the largest iOS screen size ever, but also two new Apple accessories that may be important to test your app with: the Apple Pencil and the Smart Keyboard. On the other new devices, iPhone and iPad screen resolutions remain the same and get faster processors. From a testing perspective, things that perform well on last year’s models should perform even better on the new hardware.

It is also interesting to note that all of the devices that can run iOS 6 are on the 32-bit side of the processor divide.

I hope you find this version of the chart helpful. •

Chart depicting iOS devices by screen size, processor and supported OS version

iOS Device Summary: A8 iPod Touch Update

I’ve updated my iOS Device Summary with the newly announced iPod touch.

You can check out the iOS Device Summary page for more info about the summary plus PDF downloads—including optimized files for printing.

For developers, the iPod touch has been a useful, relatively inexpensive compact device for testing. The previous model was released almost four years ago and sits at the very low end of devices that support iOS 8 and iOS 9.  The new sixth generation iPod touch is a welcome addition as a more affordable testing device with a recent 64-bit processor.  Like previous generations, the new iPod touch has a 4-inch display, so an iPhone is still needed for on-device testing of larger screen resolutions.

It is interesting to note that every iOS device that Apple currently sells, except the iPhone 5c, has a 64-bit processor.

This also means that if you need to acquire older models for testing iOS 8 and iOS 9, you will need to turn to refurbished or used devices.

I hope you find this version of the chart helpful. •

Chart depicting iOS devices by screen size, processor and supported OS version

iOS Device Summary: iOS 9 Update

I’ve updated my iOS Device Summary with the iOS 9 info Apple has publicly posted.

Check out the iOS Device Summary page for the rationale behind the summary plus PDF downloads—including optimized files for printing.

Some things to note from WWDC announcements and Apple product lineup changes:

All devices that support iOS 8 will also support iOS 9.

Apps are currently required to support both 32-bit and 64-bit processors. With iOS 9, the App Store will also accept apps that are 64-bit only. This allows developers to limit deployment of an app to more recent devices with faster CPUs and GPUs. The device summary now has a line showing where 32-bit ends and 64-bit begins.

Finally, devices for testing:

  • At $199, the 16 GB, 5th generation iPod touch is still the most affordable compact iOS 9 device
  • At $299, the 16 GB, WiFi iPad mini 2 is now the most affordable iOS 9 iPad
  • As of 6/19/15, the original iPad mini is discontinued—try used and refurbished devices for low-end iPad testing.

I hope you find this version of the chart helpful. •

Chart depicting iOS devices by screen size, processor and supported OS version

NSConference 7: A Look Back

Last fall, I received an email that read, “I would like to invite you to be a speaker at NSConference 7”.

In the invitation email, conference organizer Steve ‘Scotty’ Scott (@macdevnet) described his intent for the conference:

“At NSConference I want the speakers to be with the attendees all the time. I want you to be at the sessions, I want you to be at the meals, I want you to be at the events. I want you to mix, eat, drink and chat with as many attendees as possible.”

“What I require most in an NSConference speaker is enthusiasm and a love of being with the OS X and iOS developer community. Right now I am not looking to pick talk topics, as it’s all about people first.”

I accepted the invitation immediately.

All About People First

In his opening remarks, Scotty expressed the same intent in a different fashion. He said that the speakers and topics were, of course, important, but the real heart of NSConf was creating an environment where members of the developer community could interact.

Leicester Athena

Leicester Athena
Photo by NotFromUtrecht via Wikimedia Commons

The format at NSConf was unlike other conferences I have attended. Each segment began with a 30-minute talk followed by two 10 or 15-minute blitz-talks, followed by a 30-minute break. This approach packed three topics plus plenty of time to talk with fellow attendees into a 90-minute block.

The venue was the Leicester Athena, a gorgeous 1930s art deco theater re-styled to host events. The seating was at round tables, giving folks a chance to talk with one another. There was a massive stage with great lighting and sound (and yes, a full bar on stage too). It is truly a beautiful venue, well-suited to Scotty’s goals for the event.

The days were filled with speakers giving talks, conversations with attendees and lots of coffee and tea. In the evenings, good food and more conversation. The first night was the banquet, each table set with a candelabra, with wine and a meal served at your table. The second night was the party, with a buffet meal and mingling.

It was after folks had a chance to be fed at the party that we launched into our Breakpoint Jam.

Breakpoint Jam: NSConf Edition

The idea behind a Breakpoint Jam is that the band is made up of whoever happens to be in town for a conference. Folks practice up some James Dempsey and the Breakpoints songs on their own before arriving, we do a quick rehearsal the day of the show, and then we perform.

I find the most stress-inducing shows are when all the musicians are new to the Breakpoint Jam — this was one of those performances.

It takes a leap of faith to get on a plane in San Francisco and fly over 5,000 miles to England, knowing you will be performing for a theater full of people with musicians you have never performed with, rehearsed with, or in some cases even met before.

Kevin Cupp on guitar, James Dempsey on vocals, Jonathan Fox on drums and S ‘Scotty’ Scott on bass at the Breakpoint Jam during NSConference 7

Kevin Cupp, James Dempsey, Jonathan Fox and Steve ‘Scotty’ Scott kick off the NSConf 7 Breakpoint Jam
Photo by Cathy Shive

That leap of faith was rewarded by musicians that pulled it all together amazingly well in the rehearsal time allotted.

Guitarist and iOS developer Kevin Cupp (@kevincupp) did perhaps the best walk-on guitar part in Breakpoint Jam history, having learned every nuance from the rehearsal tracks I had sent.

Longtime NeXT and Apple indie developer John Fox (@djembe) added a full drum kit to a Breakpoint Jam for the first time, skillfully playing the varying musical styles from the driving beat of Goto Fail to the Hawaiian breeze-inspired Liki Song.

Rounding out the core trio of Conditional Breakpoints for the evening was NSConf’s own Scotty on bass. (It is no coincidence that Scotty was positioned closest to the on-stage bar.)

For The Liki Song, backup singers arrived in the form of Laura Savino (@savinola) and Ruotger Deecke (@roddi) making their Breakpoint Jam debut, and Uli Kusterer (@uliwitness) whose bass voice is perfect for the ‘object alloc’ chant beneath the choruses.

And, on the ever-important slide-advance keyboard, the incomparable Daniel Steinberg (@dimsumthinking).

Kevin Cupp playing guitar, James Dempsey singing and playing ukulele, Jonathan Fox playing drums, Laura Savino, Ruotger Deecke and Uli Kusterer singing, Steve ‘Scotty’ Scott playing bass.

Left to Right: Kevin Cupp, James Dempsey, Jonathan Fox, Laura Savino, Ruotger Deecke, Uli Kusterer, Steve ‘Scotty’ Scott.
Image by Marius Ciocanel

It was tremendous fun to play on that big stage, in that beautiful theater, complete with lighting effects (and a fog machine, I think). The show was only possible because of all of those who joined in the jam—a big thank you to them for lending their talents to the show. And of course, a giant thank you to everyone the audience, it was a privilege to play for you all.

The Future: A Look Back

Scotty had stated that this year’s NSConference would be the last. When I looked at the schedule, I saw that Scotty had chosen my session The Future: A Look Back to be the last talk of the last day of the last NSConf.

The talk took a look back to the Apple/NeXT merger and the history of some of the technologies that we use today. After the talk, some old-timers told me that they enjoyed the walk down memory lane, while some more recent arrivals to iOS and OS X development commented they appreciated hearing some backstory on the technologies they are using today.

James Dempsey Presenting ‘The Future: A Look Back’ at NSConf 7

The Future: A Look Back at NSConf 7
Photo by Raphael Sebbe

Scotty had also announced that, although this was the final NSConf, he hoped to do another event in the future that took the best of NSConf, but proceeded in a different way — different enough that calling it ‘NSConf’ would be misnomer.

With that in mind, I closed my talk as follows:

“As we wind down to the last session of the last NSConf, I’d remind you that in this developer world of ours, nothing is ever truly gone. Specific implementations come and go, particular instances are created and released, but the underlying themes stick around. That’s true whether we are talking about technologies, or the community of people that use them to create magnificent things.”

Almost Like Being There

Being at NSConf was a fantastic experience — I learned a lot and had the chance to meet and get to know people I would likely not have met otherwise.

I’m very grateful to Scotty for inviting me and to the entire conference team for doing a fantastic job and for treating the attendees and speakers very well. NSConf had an easy-going feel, but everything hit its mark. It takes a great team to make it look that easy.

The next best thing to being there would be watching the amazing talks. And as of last week they are available to everyone on the NSConf 7 channel on Vimeo. I encourage you to check out all the talks, including my talk The Future: A Look Back, which I’ve included below. •

NSConference 7 was held March 16-18, 2015 in Leicester, UK.

Learning More About Xcode Build Settings with BuildSettingExtractor

Last week I posted about BuildSettingExtractor, a utility that makes it easy to pull the build settings out of an Xcode project file and into xcconfig build configuration files. (The post also mentions some xcconfig file benefits with links to ‘how to’ information. Read the earlier post here.)

I also wanted BuildSettingExtractor to be useful for anyone who wants to learn more about the build settings in their projects. To that end, the latest version, available on github, generates build setting descriptions gleaned from the installed version of Xcode.

For example:

// Framework Search Paths
// This is a list of paths to folders containing frameworks to be
// searched by the compiler for both included or imported header
// files when compiling C, Objective-C, C++, or Objective-C++, and by
// the linker for frameworks used by the product. Paths are delimited
// by whitespace, so any paths with spaces in them need to be
// properly quoted. [-F]


// Info.plist File
// This is the project-relative path to the plist file that contains
// the Info.plist information used by bundles.

INFOPLIST_FILE = BuildSettingExtractorTests/BuildSettingExtractorTests-Info.plist

Inline Build Setting Info

To learn more about build settings, Apple provides the Build Setting Reference (Apple developer documentation links are notoriously fragile, just search for the document) as well as Quick Help in Xcode when a build setting is selected. (In Xcode choose View > Utilities > Show Quick Help Inspector (Cmd-Opt-2))

In addition to these ways of learning more, BuildSettingExtractor gleans the build setting info from Xcode and puts it inline in the generated xcconfig files. This has a few benefits:

  • Read about each build setting without selecting setting one by one in Xcode
  • Read about only the build settings currently set in your project and targets
  • Information about build settings is available wherever you are looking at the xcconfig file: github, text editors, diff tools, etc.

What if I don’t want this lovely but verbose feature?

If you want BuildSettingExtractor to generate pithy xcconfig files without the build setting info, Choose BuildSettingExtractor > Preferences… (Command-,) for the new preferences sheet and turn it off.

BuildSettingExtractor Preferences Sheet

Happy Building! (and a call for help)

I hope you find BuildSettingExtractor useful, either as a learning tool, or to get rolling with xcconfig files. If you do find it useful, please spread the word about it:

As for the call for help, if you would like to help out with a basic app icon for BuildSettingExtractor, the utility can emerge from the primordial world of the generic app icon. Contact me if you are interested. •

Generating Xcode Build Configuration Files with BuildSettingExtractor (xcodeproj → xcconfig)

The most recent NSScreencast covered using build configuration files to specify build settings in Xcode. (Episode #154)

Using build configuration files—or xcconfig files as they are known—has some definite benefits.  However, as seen in the screencast, the initial process of copying the current build settings out of an Xcode project into xcconfig files is tedious and potentially error-prone.

Screenshot of Build Setting Extractor 1.0

Nuthin’ fancy. Drop an xcodeproj file on it—it spits out xcconfig files.

To aid in that initial extraction process, I wrote a utility app called BuildSettingExtractor.  It is available on github at

The app is a simple droplet utility: drop an xcodeproj file on it, choose a destination folder, BuildSettingExtractor will extract the build settings from the project and generate xcconfig files.

A set of files is generated for each target in the project and for the project itself.  Each set of files includes one xcconfig file per build configuration and one xcconfig file of shared settings. For example, a typical Xcode project will generate nine xcconfig files: three sets of files for the app target, test target, and project with three files for Debug, Release and Shared in each set.

I hope you find BuildSettingExtractor useful. Even if you are just curious about project build settings, this is an easy way to inspect a project’s build settings without fear of accidentally changing them.

A little more about xcconfig files

By default, Xcode stores all build configuration settings in the project file itself. However, you can tell Xcode to base a build configuration’s settings on a build configuration file instead.

A build configuration file is a text file of key-value pairs. An xcconfig file can also contain comments and include other xcconfig files.

// Project-Debug.xcconfig

#include "Project-Shared.xcconfig” // Include other xcconfig files

// An xcconfig file is a text file of key-value pairs.
// Use comments to record why you are using certain build values.
// The /*comment*/ and #comment styles are not valid in an xcconfig file.


There are some benefits to using xcconfig files:

  • Build settings are not in project file—this removes one source of project file merge conflicts
  • Build settings can be documented using comments
  • An xcconfig file of shared settings can be included in each build configuration

There are also potential drawbacks to using xcconfig files.  One potential pitfall is that the build settings for a configuration are based on the xcconfig file—but settings set in Xcode override the xcconfig file settings. This can leave you with unexpected build behavior because an errant build setting set in Xcode is overriding the xcconfig file setting.

This issue is compounded by the fact that when new Xcode versions update project settings, the settings are added to the project, not to an xcconfig file.  So when using xcconfig files, some vigilance is required to keep an eye out for build settings being added to the project.  These stray build settings should be moved from the project to the appropriate xcconfig file.

What Next?

BuildSettingExtractor generates xcconfig files from a project—it does not set your project up to use them.  Here are few resources that walk through that process:

I was inspired to release BuildSettingExtractor by Episode #154 of NSScreencast. The episode is a step by step demo walking through the process.

By the way, if you aren’t familiar with NSScreencast, I recommend taking a look. Ben Scheirman (@subdigital) presents weekly bite-sized screencasts covering a wide range of development topics. Some screencasts are free and some, like Episode #154, require a subscription. (Ben also plays guitar with James Dempsey and the Breakpoints, but that has yet to be the subject of a screencast.)

The blog post Using xcconfig Files For Your Xcode Project by Jont Olof Lyttkens (@jontolof) explains how to set up a project to use xcconfig files in Xcode 6.

Finally, Building the Build System by Rob Napier (@cocoaphony) is an older post, written for an older version of Xcode, but the overall concepts and explanation of the benefits are still relevant.

In each of these walkthroughs, instead making a bunch of xcconfig files by hand and then copying and pasting from the project into the correct file, you would use BuildSettingExtractor instead. •

iOS Device Summary: iPad Air 2 and iPad mini 3 Update

It’s been a busy few weeks with Apple announcements and Backtrace, our new album of iOS and Mac development songs, hitting the Billboard charts. I’ve updated my iOS Device Summary to include the recently announced iPads.

Check out the iOS Device Summary page for the rationale behind the summary as well as PDF downloads—including optimized files for printing.

The new iOS devices introduced this fall presented some challenges for the summary chart:

The iPad mini 2 and iPad mini 3 have identical processors and screens. The devices appear on the chart as a single entry, split to reflect the different supported OS versions.

We have not seen a revised iPod touch in two years. With the traditional Apple fall events behind us, it is unlikely we will see a significant update until next fall at the earliest. Since the iPod touch line ends at the A5 chip and the multiple-model iPhones start at the A6 chip, these have been combined into a single row.

Finally, the new A8X chip pushes the number of columns to the limit, so I’ve dropped the ARM chip and the iPhone 3GS and 3rd Generation iPod touch from the chart.

Since the chart is starting to have trouble cleanly representing devices on a single page, I am looking at more dynamic ways of presenting this information in the future.

Until then, I hope you find this version of the summary chart helpful. •

Chart depicting iOS devices by screen size, processor and supported OS version
Check out the iOS Device Summary page to learn more and download printable PDFs of the summary.
And check out Backtrace, the only album of iOS and Mac development tunes ever on the Billboard charts.