couchbase-lite-ios: Crash on [CBLDatabase(Internal) notifyChanges:]

I experiencing that [CBLDatabase(Internal) notifyChanges:] sometimes crashes. I cannot consistently reproduce the issue, but it seems occurs when I put a heavy workload on the manager (performing many writes and reads simultaneously). Again, I cannot force this crash…

The two relevant threads running at the time of the crash has the following stack traces:

Crashed: com.myapp.manager.queue
0  libobjc.A.dylib                0x184dbc150 objc_msgSend + 16
1  CoreFoundation                 0x18622c820 <redacted> + 76
2  CoreFoundation                 0x18622c790 <redacted> + 640
3  myApp                          0x1005b264c -[CBLDatabase(Internal) notifyChanges:] (CBLDatabase+Internal.m:486)
4  myApp                          0x10057c404 catchInBlock (CBLDatabase.m:143)
5  libdispatch.dylib              0x1851fe9e0 _dispatch_call_block_and_release + 24
6  libdispatch.dylib              0x1851fe9a0 _dispatch_client_callout + 16
7  libdispatch.dylib              0x18520b604 _dispatch_continuation_pop + 448
8  libdispatch.dylib              0x18520b338 _dispatch_async_redirect_invoke + 608
9  libdispatch.dylib              0x18520ea50 _dispatch_root_queue_drain + 540
10 libdispatch.dylib              0x18520e7d0 _dispatch_worker_thread3 + 124
11 libsystem_pthread.dylib        0x185407100 _pthread_wqthread + 1096
12 libsystem_pthread.dylib        0x185406cac start_wqthread + 4

CouchbaseLite
0  libsystem_platform.dylib       0x185401658 OSAtomicDequeue + 24
1  libsystem_malloc.dylib         0x185387b54 _nano_malloc_check_clear + 156
2  libsystem_malloc.dylib         0x185386c38 nano_malloc + 44
3  libsystem_malloc.dylib         0x185375664 malloc_zone_malloc + 172
4  CoreFoundation                 0x18621d044 _CFRuntimeCreateInstance + 336
5  CoreFoundation                 0x186232bf8 CFStringCreateMutable + 68
6  Foundation                     0x186e3611c <redacted> + 36
7  libswiftCore.dylib             0x101e39390 swift_stdlib_NSStringHashValue + 52
8  libswiftCore.dylib             0x101d7e17c _TTSfq4s___TFSSg9hashValueSi + 192
9  libswiftCore.dylib             0x101d3f07c _TTWSSs8HashablesFS_g9hashValueSi + 48
10 libswiftCore.dylib             0x101cb4214 _TFCs26_SwiftDeferredNSDictionary20bridgingObjectForKeyfPs9AnyObject_GSqPS0___ + 264
11 libswiftCore.dylib             0x101cb40f0 _TFCs26_SwiftDeferredNSDictionary9objectForfPs9AnyObject_GSqPS0___ + 36
12 libswiftCore.dylib             0x101cb4c78 _TToFCs30_HashableTypedNativeSetStorage12getObjectForfPs9AnyObject_GSqPS0____merged + 52
13 myApp                          0x1005b5350 -[NSDictionary(CBJSONEncoder) cbjson_encodeTo:canonical:] (CBJSONEncoder.m:249)
14 myApp                          0x1005b536c -[NSDictionary(CBJSONEncoder) cbjson_encodeTo:canonical:] (CBJSONEncoder.m:249)
15 myApp                          0x1005b5620 -[NSDictionary(CBJSONEncoder) cbjson_encodeTo:canonical:keyFilter:error:] (CBJSONEncoder.m:287)
16 myApp                          0x1005b4a78 -[CBJSONEncoder encode:] (CBJSONEncoder.m:96)
17 myApp                          0x100538acc +[CBL_Revision asCanonicalJSON:error:] (CBL_Revision.m:251)
18 myApp                          0x1005ec794 __103-[CBL_SQLiteStorage addDocID:prevRevID:properties:deleting:allowConflict:validationBlock:status:error:]_block_invoke (CBL_SQLiteStorage.m:1774)
19 myApp                          0x1005e6544 -[CBL_SQLiteStorage inTransaction:] (CBL_SQLiteStorage.m:665)
20 myApp                          0x1005e6690 -[CBL_SQLiteStorage inOuterTransaction:] (CBL_SQLiteStorage.m:693)
21 myApp                          0x1005ec10c -[CBL_SQLiteStorage addDocID:prevRevID:properties:deleting:allowConflict:validationBlock:status:error:] (CBL_SQLiteStorage.m:1670)
22 myApp                          0x1005ae990 -[CBLDatabase(Insertion) putDocID:properties:prevRevisionID:allowConflict:source:status:error:] (CBLDatabase+Insertion.m:142)
23 myApp                          0x100571bd8 -[CBLDocument putProperties:prevRevID:allowConflict:error:] (CBLDocument.m:324)
24 myApp                          0x100576774 -[CBLUnsavedRevision save:] (CBLRevision.m:380)
25 myApp                          0x100571d84 -[CBLDocument update:error:] (CBLDocument.m:353)
26 myApp                          0x1001f4b40 static Database.(update(for : String, serializedObject : [String : AnyObject], completionClosure : () -> ()?) -> ()).(closure #1) (Database.swift:189)
27 myApp                          0x1001f60dc partial apply for static Database.(update(for : String, serializedObject : [String : AnyObject], completionClosure : () -> ()?) -> ()).(closure #1) (Database.swift)
28 myApp                          0x1001f3c3c thunk (Database.swift)
29 myApp                          0x10053a270 __35-[CBL_Server tellDatabaseNamed:to:]_block_invoke (CBL_Server.m:80)
30 Foundation                     0x186e3a4cc <redacted> + 340
31 CoreFoundation                 0x1862f542c <redacted> + 24
32 CoreFoundation                 0x1862f4d9c <redacted> + 540
33 CoreFoundation                 0x1862f29a8 <redacted> + 744
34 CoreFoundation                 0x186222da4 CFRunLoopRunSpecific + 424
35 Foundation                     0x186d3cd74 <redacted> + 304
36 myApp                          0x10053acbc -[CBL_RunLoopServer runServerThread] (CBL_Server.m:193)
37 Foundation                     0x186e3a2d8 <redacted> + 996
38 libsystem_pthread.dylib        0x18540968c <redacted> + 240
39 libsystem_pthread.dylib        0x18540959c _pthread_start + 282
40 libsystem_pthread.dylib        0x185406cb4 thread_start + 4

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• Version: 1.4.0
• Client OS: iOS 10.3.1
• Server: N/A