While trying to use SpriteKit in an iOS 8 keyboard extension, I have run into numerous crashes that only occur when using a physical device and not attached to the debugger.
If the debugger is connected to device, or if running in the SIM, everything is lovely.
When the debugger isn't attached, I believe the lifecycle of the extension is slightly different, and there are times in which the keyboard extension is backgrounded, causing crashes in OpenGL.
The crash we are hitting is described in an apple tech note. It is in the function gpus_ReturnNotPermittedKillClient , and Apple states that it occurs because you can't run OpenGL in the background, and suggests using App Delegate callbacks to pause your OpenGL activity.
Since this is a keyboard extension, there is no app delegate. Instead we tried registering for app delegate lifecycle notifications: no luck - they don't fire. So we tried using viewcontroller lifecycle callbacks, and it still doesn't fix the issue.
When this crash happens, we are the active keyboard, and are just doing a lot of stuff around SpriteKit/SKView and UIImage manipulation, there is no obvious reason why we would be backgrounded, but yet this crash occurs. The same crash does seem to occur if we we truly do get backgrounded.
Ultimately, I'm trying to figure out how to know that we are being backgrounded, and that we need to pause OpenGL.
Here is the full stack:
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000001
Triggered by Thread: 0
Thread 0 name: Dispatch queue: com.apple.spritekit.renderQueue
Thread 0 Crashed:
0 libGPUSupportMercury.dylib 0x000000018e89a18c gpus_ReturnNotPermittedKillClient + 12
1 libGPUSupportMercury.dylib 0x000000018e89b124 gpusSubmitDataBuffers + 160
2 GLEngine 0x0000000189a10260 gliPresentViewES_Exec + 192
3 GLEngine 0x0000000189a10164 gliPresentViewES + 80
4 OpenGLES 0x0000000189a1fc7c -[EAGLContext presentRenderbuffer:] + 68
5 SpriteKit 0x000000018a51c4a4 -[SKView _renderContent] + 1028
6 libdispatch.dylib 0x0000000196c8d368 _dispatch_client_callout + 12
7 libdispatch.dylib 0x0000000196c966e4 _dispatch_barrier_sync_f_invoke + 72
8 SpriteKit 0x000000018a51c060 -[SKView renderContent] + 88
9 SpriteKit 0x000000018a519034 __29-[SKView setUpRenderCallback]_block_invoke + 60
10 SpriteKit 0x000000018a545fd4 -[SKDisplayLink _callbackForNextFrame:] + 268
11 QuartzCore 0x000000018a04d27c CA::Display::DisplayLinkItem::dispatch() + 28
12 QuartzCore 0x000000018a04d114 CA::Display::DisplayLink::dispatch_items(unsigned long long, unsigned long long, unsigned long long) + 320
13 IOKit 0x00000001870458cc IODispatchCalloutFromCFMessage + 372
14 CoreFoundation 0x0000000185e995e0 __CFMachPortPerform + 176
15 CoreFoundation 0x0000000185eae1fc __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
16 CoreFoundation 0x0000000185eae15c __CFRunLoopDoSource1 + 432
17 CoreFoundation 0x0000000185eac0dc __CFRunLoopRun + 1636
18 CoreFoundation 0x0000000185dd90a0 CFRunLoopRunSpecific + 392
19 GraphicsServices 0x000000018ef7b5a0 GSEventRunModal + 164
20 UIKit 0x000000018a70e3bc UIApplicationMain + 1484
21 libxpc.dylib 0x0000000196e9c268 _xpc_objc_main + 764
22 libxpc.dylib 0x0000000196e9df50 xpc_main + 196
23 Foundation 0x0000000186eafc7c -[NSXPCListener resume] + 180
24 PlugInKit 0x0000000190e8a90c -[PKService run] + 596
25 PlugInKit 0x0000000190e8a544 +[PKService main] + 60
26 PlugInKit 0x0000000190e8a934 +[PKService _defaultRun:arguments:] + 20
27 libextension.dylib 0x0000000195eacd88 NSExtensionMain + 64
28 libdyld.dylib 0x0000000196cb6a04 start + 0