Anyone have a pointer about a crash Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000010

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Created May ’21

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I've recently re-implemented one of my applications in Swift and am getting crash reports from users where when they transition to a NavigationView, the second of the Navigation links causes an exception, as far as I can tell, before any of my code in that class is executed.

All of the crash logs are consistent...

Code Block Thread 0 name:
Thread 0 Crashed:
0   libswiftCore.dylib            	0x00000001a35d0a88 bool swift::HeapObjectSideTableEntry::decrementStrong<(swift::PerformDeinit)1>(unsigned int) + 24 (atomic:1003)
1   LAX Time & Score              	0x0000000102bd1378 specialized PenaltyTimesView.init(gameState:) + 156 (PenaltyTimesView.swift:0)
2   LAX Time & Score              	0x0000000102bcbf80 closure #1 in closure #1 in ConfigurationView.body.getter + 836 (ConfigurationView.swift:0)
3   SwiftUI                       	0x00000001a628b958 List<>.init(content:) + 96 (List.swift:594)
4   LAX Time & Score              	0x0000000102bcbb80 closure #1 in ConfigurationView.body.getter + 240 (ConfigurationView.swift:20)
5   SwiftUI                       	0x00000001a5f90d38 NavigationView.init(content:) + 28 (NavigationView.swift:97)
6   LAX Time & Score              	0x0000000102bcc844 body.get + 116 (ConfigurationView.swift:19)

Looking at the disassembly, this (PenaltyTimesView.init(gameState:) + 156) is at a point where malloc is being called, which makes lots of sense with the reference counting being done with HeapObjectSideTableEntry in the Swift code.

I'm not trying to do anything particularly clever here, just initializing the View with an ObservedObject (gameState)

Code Block struct PenaltyTimesView: View {
    @ObservedObject var gameState: GameState
    @State private var selectedPenaltyLength : String
    @State private var selectedPenaltyIndex : Int
    @State private var separatePenaltyClock : Bool
    init(gameState : GameState) {
        self.gameState = gameState
        selectedPenaltyLength = ""
        selectedPenaltyIndex = 0
        separatePenaltyClock = gameState.separatePenaltyClock
        selectedPenaltyLength = formatSeconds(gameState.penaltyLengths![0])
    }...

The outer view is also relatively simple:

Code Block struct ConfigurationView: View {
    @ObservedObject var gameState: GameState
    init(gameState: GameState) {
        self.gameState = gameState
        UINavigationBar.appearance().backgroundColor = UIColor(white: 0.8, alpha: 0.25)
    }
    var body: some View {
        NavigationView {
            List {
                NavigationLink(
                    destination: PeriodLengthView(gameState: gameState),
                    label: {
                        Text("Period Lengths")
                    })
                NavigationLink(
                    destination: PenaltyTimesView(gameState: gameState),
                    label: {
                        Text("Penalty Times")
                    })
                NavigationLink(
                   destination: BackgroundView(gameState: gameState),
                    label: {
                        Text("Background")
                    })...

If somehow gameState were bad, I would have assumed that the first NavigationLink would fail, not the second.

I've been unable to reproduce this with the devices I have at hand, so any insights or suggestions would really be appreciated.

Answered by workingdogintokyo in 675977022

just an observation, I would avoid the "!" in:

Code Block     selectedPenaltyLength = formatSeconds(gameState.penaltyLengths![0])

and use:

Code Block     init(gameState : GameState) {
        self.gameState = gameState
        selectedPenaltyLength = ""
        selectedPenaltyIndex = 0
        separatePenaltyClock = false
        if let penalties = gameState.penaltyLengths, penalties.count > 0 {
            selectedPenaltyLength = formatSeconds(penalties[0])
        }
    }

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Answer 1

workingdogintokyo OP

May ’21

Accepted Answer

just an observation, I would avoid the "!" in:

Code Block     selectedPenaltyLength = formatSeconds(gameState.penaltyLengths![0])

and use:

Code Block     init(gameState : GameState) {
        self.gameState = gameState
        selectedPenaltyLength = ""
        selectedPenaltyIndex = 0
        separatePenaltyClock = false
        if let penalties = gameState.penaltyLengths, penalties.count > 0 {
            selectedPenaltyLength = formatSeconds(penalties[0])
        }
    }

0

Answer 2

shawnlavin OP

May ’21

Thank you, that is probably a better construct, but as far as I can see, the problem happens before this code is executed.

0

Answer 3

shawnlavin OP

May ’21

Looking at the disassembly, the code for the initialization of the PenaltyTimesView were significantly different than those for the other views, I suspect some issues here with timing of operations (as the optionals should always be populated before this code is called)

Removed the optional from the penalty lengths (that was an artifact of a previous implementation strategy) and moved the initialization of the State variables to the .onAppear() and this significantly re-arranged the code in disassembly for the impacted class, avoiding what I think may have been a race condition...

Compiled, tested and re-submitted the app, users who were reporting the problem now report proper behavior.

Thank you [https://developer.apple.com/forums/profile/workingdogintokyo] for you input.

0