Has anyone else experienced a crash (EXC_BAD_ACCESS) with the following stack trace:
0 Object_isClass
22 UIApplicationMain
23 main
24 start
If I click on UIApplicationMain in the stack trace then I get the following:
UIKitCore`UIApplicationMain:
0x21a6ef8a4 <+0>: stp x24, x23, [sp, #-0x40]!
0x21a6ef8a8 <+4>: stp x22, x21, [sp, #0x10]
0x21a6ef8ac <+8>: stp x20, x19, [sp, #0x20]
0x21a6ef8b0 <+12>: stp x29, x30, [sp, #0x30]
0x21a6ef8b4 <+16>: add x29, sp, #0x30 ; =0x30
0x21a6ef8b8 <+20>: mov x20, x3
0x21a6ef8bc <+24>: mov x21, x1
0x21a6ef8c0 <+28>: mov x22, x0
0x21a6ef8c4 <+32>: mov x0, x2
0x21a6ef8c8 <+36>: bl 0x21ac17b68 ; symbol stub for: -[_UICloudSharingActivity _activitySupportsPromiseURLs]
0x21a6ef8cc <+40>: mov x19, x0
0x21a6ef8d0 <+44>: mov x0, x20
0x21a6ef8d4 <+48>: bl 0x21ac17b68 ; symbol stub for: -[_UICloudSharingActivity _activitySupportsPromiseURLs]
0x21a6ef8d8 <+52>: mov x20, x0
0x21a6ef8dc <+56>: mov w0, #0x168
0x21a6ef8e0 <+60>: movk w0, #0x2b87, lsl #16
0x21a6ef8e4 <+64>: mov w1, #0x32
0x21a6ef8e8 <+68>: mov x2, #0x0
0x21a6ef8ec <+72>: mov x3, #0x0
0x21a6ef8f0 <+76>: mov x4, #0x0
0x21a6ef8f4 <+80>: bl 0x21ac1779c ; symbol stub for: __66-[UICloudSharingController _deleteShareAfterDismissalWithoutSave:]_block_invoke_2
0x21a6ef8f8 <+84>: orr w0, wzr, #0x3
0x21a6ef8fc <+88>: orr w1, wzr, #0x3
0x21a6ef900 <+92>: mov x2, #-0x1
0x21a6ef904 <+96>: orr x4, xzr, #0x8000000000000000
0x21a6ef908 <+100>: mov w3, #0x0
0x21a6ef90c <+104>: bl 0x21ac175c8 ; symbol stub for: -[UIWebView webView:decidePolicyForNewWindowAction:request:newFrameName:decisionListener:]
0x21a6ef910 <+108>: adrp x23, 52595
0x21a6ef914 <+112>: ldr w8, [x23, #0x364]
0x21a6ef918 <+116>: cbz w8, 0x21a6ef9a0 ; <+252>
0x21a6ef91c <+120>: lsr w8, w8, #8
0x21a6ef920 <+124>: cmp w8, #0x201 ; =0x201
0x21a6ef924 <+128>: b.lo 0x21a6ef950 ; <+172>
0x21a6ef928 <+132>: bl 0x21ac17a48 ; symbol stub for: -[_UIShareParticipantDetails detailText]
0x21a6ef92c <+136>: mov x23, x0
0x21a6ef930 <+140>: mov x0, x22
0x21a6ef934 <+144>: mov x1, x21
0x21a6ef938 <+148>: mov x2, x19
0x21a6ef93c <+152>: mov x3, x20
0x21a6ef940 <+156>: bl 0x21a6ef9d0 ; _UIApplicationMainPreparations
0x21a6ef944 <+160>: mov x0, x23
0x21a6ef948 <+164>: bl 0x21ac17a3c ; symbol stub for: -[_UIShareParticipantDetails setParticipantID:]
0x21a6ef94c <+168>: b 0x21a6ef964 ; <+192>
0x21a6ef950 <+172>: mov x0, x22
0x21a6ef954 <+176>: mov x1, x21
0x21a6ef958 <+180>: mov x2, x19
0x21a6ef95c <+184>: mov x3, x20
0x21a6ef960 <+188>: bl 0x21a6ef9d0 ; _UIApplicationMainPreparations
0x21a6ef964 <+192>: adrp x8, 52595
0x21a6ef968 <+196>: ldr x0, [x8, #0x328]
0x21a6ef96c <+200>: adrp x8, 1577
0x21a6ef970 <+204>: add x1, x8, #0xad5 ; =0xad5
0x21a6ef974 <+208>: bl 0x21ac17b2c ; symbol stub for: CloudDocsLibrary
0x21a6ef978 <+212>: mov x0, x20 <--- Exception bad access code 1
0x21a6ef97c <+216>: bl 0x21ac17b5c ; symbol stub for: -[_UICloudSharingActivity _documentSharingControllerDidDismiss:]
0x21a6ef980 <+220>: mov x0, x19
0x21a6ef984 <+224>: bl 0x21ac17b5c ; symbol stub for: -[_UICloudSharingActivity _documentSharingControllerDidDismiss:]
0x21a6ef988 <+228>: mov w0, #0x0
0x21a6ef98c <+232>: ldp x29, x30, [sp, #0x30]
0x21a6ef990 <+236>: ldp x20, x19, [sp, #0x20]
0x21a6ef994 <+240>: ldp x22, x21, [sp, #0x10]
0x21a6ef998 <+244>: ldp x24, x23, [sp], #0x40
0x21a6ef99c <+248>: ret
0x21a6ef9a0 <+252>: adrp x8, 52593
0x21a6ef9a4 <+256>: ldr x8, [x8, #0xf40]
0x21a6ef9a8 <+260>: cmn x8, #0x1 ; =0x1
0x21a6ef9ac <+264>: b.ne 0x21a6ef9b8 ; <+276>
0x21a6ef9b0 <+268>: ldr w8, [x23, #0x364]
0x21a6ef9b4 <+272>: b 0x21a6ef91c ; <+120>
0x21a6ef9b8 <+276>: adrp x0, 52593
0x21a6ef9bc <+280>: add x0, x0, #0xf40 ; =0xf40
0x21a6ef9c0 <+284>: adrp x1, 41868
0x21a6ef9c4 <+288>: add x1, x1, #0x640 ; =0x640
0x21a6ef9c8 <+292>: bl 0x21ac17490 ; symbol stub for: -[UIWebView _webView:commitPreview:]
0x21a6ef9cc <+296>: b 0x21a6ef9b0 ; <+268>
Looks like it's crashed trying to do some CloudKit stuff? Which is odd because we don't have any CloudKit things setup...
I've only ever seen this crashing locally with this (when running through Xcode), not in our CI. We recently added some CoreData usage, could that be related in some way?
It seems like the CloudKit stuff might be a red herring and really this is a KVO crash as when I run the 'bt' command in the console I get the backtrace including the following warning: KVO_IS_RETAINING_ALL_OBSERVERS_OF_THIS_OBJECT_IF_IT_CRASHES_AN_OBSERVER_WAS_OVERRELEASED_OR_SMASHED
I've been seeing this issue while trying to track down a KVO crash so that makes some sense... shame there's not more info in the stack!
I still don't really know why this crash was happening but I've managed to get rid of it by changing some of the KVO setup.
To track down the problematic KVO I commented out various bits of KVO code and ran a custom test suite which would always crash within 30 minutes or so. That lead me to some block-based KVO of AVPlayerItem's status property being the culprit.
I remembered seeing a quote from someone very wise along the lines of
"Block-based KVO, it just works (until it doesn't)" - Anon
So I switched the block-based KVO to the old callback style and the crash seems to have disappeared.
sigh