inessential by Brent Simmons

February 2021

Mysterious SwiftUI Crash

A friend just released a new version of their app — and it has a new crash not seen during development.

This new version of the app has a bunch of new SwiftUI code, and this crash is definitely in SwiftUI — but it’s apparently in SwiftUI itself.

Anyone else seen this? Is there something my friend can do to work around this?

Hardware Model: iPhone13,4
Code Type: ARM-64
OS Version: iPhone OS 14.4 (18D52)

Exception Type: SIGTRAP
Exception Codes: TRAP_BRKPT at 0x19d447a18

Crashed Thread: 0

Thread 0 Crashed:
0 libswiftCore.dylib 0x000000019d447a18 _assertionFailure(_:_:file:line:flags:) + 492
1 SwiftUI 0x00000001a011c52c ViewCache.commitPlacedChildren(from:to:) + 3032
2 SwiftUI 0x000000019ffc8eb4 specialized IncrementalChildPlacements.updateValue() + 1384
3 SwiftUI 0x00000001a00e6fbc partial apply for specialized + 24
4 AttributeGraph 0x00000001c2cbba50 AG::Graph::UpdateStack::update() + 492
5 AttributeGraph 0x00000001c2cbbe84 AG::Graph::update_attribute(AG::data::ptr<AG::Node>, bool) + 332
6   AttributeGraph 0x00000001c2cc5088 AG::Subgraph::update(unsigned int) + 884
7 SwiftUI 0x00000001a07d1cdc GraphHost.runTransaction() + 172
8 SwiftUI 0x00000001a07d4e1c GraphHost.runTransaction(_:) + 92
9 SwiftUI 0x00000001a07d37a8 GraphHost.flushTransactions() + 176
10 SwiftUI 0x00000001a07d4db4 closure #1 in closure #1 in GraphHost.asyncTransaction<A>(_:mutation:style:) + 24
11 SwiftUI 0x00000001a02a3168 partial apply for closure #1 in ViewGraphDelegate.updateGraph<A>(body:) + 28
12 SwiftUI 0x00000001a0726e9c closure #1 in ViewRendererHost.updateViewGraph<A>(body:) + 108
13 SwiftUI 0x00000001a071de7c ViewRendererHost.updateViewGraph<A>(body:) + 92
14 SwiftUI 0x00000001a029f6d0 ViewGraphDelegate.updateGraph<A>(body:) + 80 
15 SwiftUI 0x00000001a07d4d84 closure #1 in GraphHost.init(data:) + 124 
16 SwiftUI 0x00000001a07d66f0 closure #1 in GraphHost.asyncTransaction<A>(_:mutation:style:)partial apply + 40
17 SwiftUI 0x00000001a02c2b98 thunk for @escaping @callee_guaranteed () -> () + 28
18 SwiftUI 0x000000019ff91a10 static NSRunLoop.flushObservers() + 148
19 SwiftUI 0x000000019ff91974 closure #1 in closure #1 in static NSRunLoop.addObserver(_:) + 16
20 SwiftUI 0x000000019ff8c4b4 specialized thunk for @callee_guaranteed () -> (@error @owned Error) + 24
21 libswiftObjectiveC.dylib 0x00000001bfcc3f30 autoreleasepool<A>(invoking:) + 64
22 SwiftUI 0x000000019ff91954 closure #1 in static NSRunLoop.addObserver(_:) + 64
23 SwiftUI 0x000000019ff91aac @objc closure #1 in static NSRunLoop.addObserver(_:) + 56
24 CoreFoundation 0x0000000199798358 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 36
25 CoreFoundation 0x00000001997925c4 __CFRunLoopDoObservers + 576
26 CoreFoundation 0x0000000199792b74 __CFRunLoopRun + 1056
27 CoreFoundation 0x000000019979221c CFRunLoopRunSpecific + 600
28 GraphicsServices 0x00000001b135e784 GSEventRunModal + 164
29 UIKitCore 0x000000019c1d2ee8 -[UIApplication _run] + 1072
30 UIKitCore 0x000000019c1d875c UIApplicationMain + 168
31 AppName 0x0000000100ed8444 main (main.m:19)
32 libdyld.dylib 0x00000001994526b0 start + 4

Slow House

“Slow House,” song #3, is more exercise than song. Where most songs have a structure like ABAB or ABACAB or whatever, this one is just A. Not even AAA — just A.

I wanted to get some practice recording an acoustic guitar — it’s the first GarageBand thing I’ve done where one of the parts was from a mic (a Yeti Blue). (All the previous parts are via MIDI and Apogee Jam.)

I was thinking about “Starman” by David Bowie, and how the verse starts with iim and I chords, which is a little unusual. In “Starman” it’s Gm and F — but I have a great deal of antipathy toward Gm (it can go straight to hell, if you ask me), so I used Am and G as the chords here.

And that’s all I did. No chorus, no other changes. Still, though, I like how it weaves two melodies together, and I like how it all falls apart at the end.

I also like how some of the string-like GarageBand instruments bring kind of a vocal sound — I can almost hear words in there. (But there are none.)

It’s called “Slow House” because it’s slow (as an antidote to the very fast Vampire’s Run) and because the piano is doing kind of a House thing.

Here’s the GarageBand file:

It’s not until I make song #1,000 that I’ll make something people actually want to listen to more than once! I get that. I’m sharing anyway, because I think maybe it’s interesting to watch someone learn. 🐣

Vampire’s Run

My second song, “Vampire’s Run,” just finished last night, is thorny — chromatic, key-modulating, choppy-guitared — where Tie & Suit is aggressively smooth and diatonic.

I have many notes…

The Verse

I started off wanting to do something early-REM-like. The idea — kind of a bullshit idea, but I liked it anyway — was this fast arpeggio on the top three strings of the guitar: B-E-D-B E-D-B-E C-E-Eflat-C E-D-B-E A-E-C#-A E-C#-A-E A-E-B-A E-B-A-E.

REM wouldn’t have done the C-E-Eflat-C part — but the rest would have fit in. Especially that move at the end from an A chord to Asus2.

To fit some chords to this, I came up with E7, a weird C major and minor, Bmsus4, A, Asus2. The idea is that you’d play the chords as normal but with the high E string always open. (A Buck-like move.)

It’s not actually pleasing-sounding — but, again, I liked it and figured I could make something out of it.

The problem: I made the song 170 beats per minute, and I can’t actually play that lick on guitar that fast. (My personal speed limit is pretty slow, actually.) I could play it on keyboard, though, so I did. It’s the very first thing you hear in the song. I cranked up the reverb on the Steinway Grand Piano instrument, and I thought it sounded great. Like a demented Charlie Brown song.

Next up was to add percussion and a bass line. The percussion is pretty much the same thing as in Tie & Suit. The bass followed the chord roots — E C B A — except that, at the end, I threw in this little blues-scale-ish lick: A-Bflat-B-Bflat-A-G-E-G-E. Which was also total bullshit, but it totally worked, so I kept it. The interaction of that with the piano arpeggio thing just sounded really cool to me.

At this point, though, this didn’t sound like REM in the least tiny bit. It sounded like an ’80s goth instrumental. So I leaned into it — added guitar instruments Eighties Goth and Starlit Cavern. Added a bunch of echo-y things like Stutter Stack and Swirling Flutters.

The Name

Last summer I started writing a blog post called “The Vampire’s Run in the Anarchist Jurisdiction” which was about going for a run at night (instead of the day, due to the pandemic) in my neighborhood in Seattle. I wasn’t able to figure out how to write it without sounding like some very fortunate guy who had to adapt in some small way and was pretty fine about it. Wouldn’t add anything to the world, so I didn’t finish it.

But, since that title was just lying around being all goth-y, I snagged the first part of it for this song. And, well, it kinda fits — the song is very fast, and during the chorus it almost sounds like flying.

The Chorus

The song structure here is simple: verse chorus verse chorus verse chorus. But there’s a key change: the verse is in E and the chorus is in C.

This is one of my favorite modulations. The chorus gets a kind of floaty and slightly sinister sound — hence the flying.

The first time I remember encountering this was in Beltane Walk by T. Rex. I remember asking my uncle, a musician, to explain the sorcery behind that song — and when, some years later, I heard that same sorcery in Hungry Like the Wolf I recognized it right away.

(I am, by the way, a glam rock guy at my core. Give me T. Rex and Bowie and all their descendants.)

Anyway — if you hear a little Duran Duran in the C-G-F chorus, you’re not wrong.

The chords aren’t actually C-G-F, though — they’re C-G6-Fmaj7 in order to make the E note prominent all throughout the song. The melody of the chorus is just arpeggios on the piano: E-C-G, E-B-G, E-C-A, with the E repeated. While the piano in the verse is tightly horizontal, the chorus is a bit more vertical.

(There’s a little fun part right as we lead into the chorus — it sounds like that split-second when a vampire leaves ground and is a little shakily airborne. You settle in in a moment. In the first chorus we have B-F#; in the second it’s D-A-B-F#, which makes it sound like Pachelbel’s Canon; and in the third it’s A-E-B-F# — a little “Hey Joe” action.)

String and other instruments are doing a C-B-A thing during the chorus — which is cool because, as you’ll remember, that also appears in the verse. Those exact same notes, which sound somewhat discordant in the verse, sound sweet in the chorus.

The End

The song comes alive in the last third while it’s repeating the chorus before ending. I was recording the piano part for that last chorus, and I was feeling a little down that this entire song was just all these arpeggios. I started improvising — and I worked up some bits to add some more melody and passion to the song. Went all pentatonic on this shit — plus the minor third for some bluesiness. Banging on the E flat a bit.

This part comes as a surprise in the song, I think, and it was just as much a surprise to me, but it’s my favorite part. Part of me thinks you shouldn’t add so much new stuff at the end, but then I remember how “Every Little Thing She Does Is Magic” has this alternate melody at the end. And I think of how The Adversary by Crime and The City Solution — a favorite of mine from a favorite soundtrack — invents a whole new song, with a different time signature even, around the 3-minute mark.

“Vampire’s Run” ends on a simple repeated phrase which I thought sounded romantic: E D-C D C-A. Vampires love that romantic stuff.

And it ends ends on a lone E note from the piano — which sounds like a question.

If you want, you can download the GarageBand file:

Computer Music

When I was a teenager I spent hundreds of hours making music on my computer. This isn’t a surprising thing to hear someone say — except that this was almost 40 years ago, and the computer wasn’t a Mac but an Apple ][ Plus.

I had an ALF II music synthesizer card with some car speakers hooked up to it. The ALF software and hardware supported nine voices, and you entered music into a staff using the computer paddles. (This page has a screenshot showing what that was like.)

Though it was a very slow way to work, and limited to beeps and bloops with varying properties, it was a miracle to me as a teenager. I took so much pleasure in layering the instruments to get something way beyond what I could perform on guitar or piano.

I stopped before turning 17. I don’t remember exactly why. Probably just spending more time writing words than music.

Tie & Suit

No recordings of the dozen or so songs I made exist. I remember fragments of some of them, and it’s fine that they don’t exist.

The one exception is the very last song I made, called “Tie & Suit.” I remember all of it: the chords, melody, arrangement, everything.

I had not, until “Tie & Suit,” written something with a traditional verse-chorus structure. Everything before that was more adventurous — to put it kindly — with odd chord progressions, lots of key changes, and weird structures. (I was convinced of my musical genius.)

I was frustrated that none of the songs I’d written were particularly memorable or even likable. I couldn’t play them on piano for someone else to enjoy. So I decided to write something simple and traditional.

I had a hobbling case of I-hate-top-forty when I was a teenager, and so I had to be sarcastic about this song: I called it “Tie & Suit” because I thought I was selling out creatively. (OMG the narcissism of me as a 16-year-old!)

Here’s the thing, though: writing a very simple melody with just five chords (I, IIm, IV, V, VIm) and a traditional structure worked! I don’t remember any of the earlier songs, but I remember this one perfectly well.

There’s a lesson in there, though I was too young to learn it.


I’ve been promising myself for years that I would allow myself to start making music again — only this time on a Mac with GarageBand. And so I did, just a few weeks ago. (This is my first time using GarageBand other than recording a couple tracks for James Dempsey last summer.)

I started where I left off, with “Tie & Suit.” Here’s a version where I tried to recreate what it sounded like on my Apple ][ Plus 37 years ago. It still ends up sounding more sophisticated than the original — it’s hard to make GarageBand sound like an early ’80s ALF II. I did my best (short of getting obsessed with it).

Also: it sucks. I know the song sucks. It doesn’t matter! I was 16 when I wrote it, and now I’m learning GarageBand and having fun.

The next thing I did was to try and make a modern version that’s still true to the original. “Tie & Suit 2021” also sucks — but it was so much fun to make!

I am now completely addicted to GarageBand. The pleasure of layering instruments together, picking their parts, and letting it play is every bit as intense as it was when I was 16 on that primitive gear. It’s hard to say that about most things! But this is just fucking wonderful.