How to read this iOS stacktrace? - ios

Question

I usually develop in higher level languages like Javascript and Python , so I am not that experienced when it comes to reading lower level stack traces. I am building an iOS app with React Native and my app sometimes unexpectedly crashes. Reading the crash log this is what I get:
Incident Identifier: B03D5F95-EFD1-4FEB-AE18-C8EFEF273E53
CrashReporter Key: 6049c1cc93a2e0163265631aa6cc2fd30a1af6e7
Hardware Model: iPhone7,2
Process: MyApp [24268]
Path: /private/var/containers/Bundle/Application/99B2B9A1-D266-4222-A083-84C4CFFCE182/MyApp.app/MyApp
Identifier: org.mycompany.MyApp
Version: 1 (1.0)
Code Type: ARM-64 (Native)
Role: Non UI
Parent Process: launchd [1]
Coalition: org.mycompany.MyApp [3119]
Date/Time: 2019-03-04 14:20:18.4924 +0800
Launch Time: 2019-03-04 14:09:15.2536 +0800
OS Version: iPhone OS 11.0.3 (15A432)
Baseband Version: 6.17.00
Report Version: 104
Exception Type: EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Termination Reason: Namespace <0xF>, Code 0x8badf00d
Triggered by Thread: 0
Filtered syslog:
None found
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x0000000180a60bc4 mach_msg_trap + 8
1 libsystem_kernel.dylib 0x0000000180a60a3c mach_msg + 72
2 BackBoardServices 0x00000001835d0de0 _BKSHIDGetCurrentDisplayBrightness + 112
3 BackBoardServices 0x00000001835de9cc BKSDisplayBrightnessGetCurrent + 32
4 FrontBoardServices 0x00000001835fffc0 -[FBSUIApplicationSystemService currentBacklightLevel] + 12
5 UIKit 0x000000018a8a3d44 -[UIDevice _backlightLevel] + 44
6 UIKit 0x000000018a8aced4 -[UIScreen _postBrightnessDidChangeNotificationIfAppropriate] + 168
7 CoreFoundation 0x0000000180efa12c __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 20
8 CoreFoundation 0x0000000180efa090 ___CFXRegistrationPost_block_invoke + 64
9 CoreFoundation 0x0000000180f1016c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 20
10 CoreFoundation 0x0000000180f0fa3c __CFRunLoopDoBlocks + 288
11 CoreFoundation 0x0000000180f0dca4 __CFRunLoopRun + 2436
12 CoreFoundation 0x0000000180e2e2d8 CFRunLoopRunSpecific + 436
13 GraphicsServices 0x0000000182cbff84 GSEventRunModal + 100
14 UIKit 0x000000018a3db880 UIApplicationMain + 208
15 MyApp 0x00000001005833d4 main + 29652 (main.m:14)
16 libdyld.dylib 0x000000018095256c start + 4
How/where do I begin reading thsi crash log? I believe it has something to do with mach_msg_trap but I haven't been able to find anything about it. For some context, my app is an app which tracks the users Geolocation with background geolocation tracking. I am unable to figure out what causes the crash.

Answer 1

See TN2141: Understanding and Analyzing Application Crash Reports, which says:
The exception code 0x8badf00d indicates that an application has been terminated by iOS because a watchdog timeout occurred. The application took too long to launch, terminate, or respond to system events. ... Whatever operation is on Thread 0 needs to be moved to a background thread, or processed differently, so that it does not block the main thread.
Are you doing anything that could be blocking the main thread for any prolonged period of time?

Answer 2

Have you add Privacy - Location in info.plist?
Something like that.
<key>NSLocationAlwaysUsageDescription</key>
<string>Why you need track location?</string>
<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>Why you need track location?</string>
<key>NSLocationWhenInUseUsageDescription</key>
<string>Why you need track location?</string>
And I see you work with background geolocation tracking. Have you turn on Background Modes in Capabilities?
If not just add Privacy turn on Background Modes and try again.