Crash in text to speech using AVSpeechSynthesizer - avspeechsynthesizer

Question

I have a text to speech feature in my news app, which my users use to read aloud news articles. I have used AVSpeechSynthesizer to this end. I have been seeing quite a lot of crashes in my live app, showing on Crashlytics. I have been able to reproduce this crash neither in a test setup while running the app through XCode, nor while using the live app on my iPhone. I am attaching the Crashlytics stack trace here:
#16
Crashed: AXSpeech
EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x000041a1b76ca3c1
Crashed: AXSpeech
0 libsystem_pthread.dylib 0x1860ff764 pthread_mutex_lock$VARIANT$mp + 354
1 CoreFoundation 0x18639793c CFRunLoopSourceSignal + 68
2 Foundation 0x186de00c4 performQueueDequeue + 464
3 Foundation 0x186ecf218 __NSThreadPerformPerform + 136
4 CoreFoundation 0x18647b77c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24
5 CoreFoundation 0x18647b6fc __CFRunLoopDoSource0 + 88
6 CoreFoundation 0x18647afd8 __CFRunLoopDoSources0 + 288
7 CoreFoundation 0x186478b5c __CFRunLoopRun + 1048
8 CoreFoundation 0x186398c58 CFRunLoopRunSpecific + 436
9 Foundation 0x186dcd594 -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 304
10 libAXSpeechManager.dylib 0x195ccf854 -[AXSpeechThread main] + 284
11 Foundation 0x186ecf0f4 __NSThread__start__ + 996
12 libsystem_pthread.dylib 0x1860fc2b4 _pthread_body + 308
13 libsystem_pthread.dylib 0x1860fc180 _pthread_body + 310
14 libsystem_pthread.dylib 0x1860fab74 thread_start + 4
Its clear that the AXSpeech thread has crashed. Can someone please help me with this as I have been pulling my hair to no avail, and the dropping percentage of crash free users has been bothering me.

Answer 1

My app has the same issue with AVSpeechSynthesizer. Crashlytics shows that it happens when the app tries to init AVSpeechSynthesizer in the main thread. The crash happens in other thread with same stack trace as yours. Here is the stack trace of the main thread. It seems that the problem may be related to the shared audio session. Hope this will help you somehow.
com.apple.coreaudio.ASClientManager
0 libsystem_kernel.dylib 0x185693568 mach_msg_trap + 8
1 libsystem_kernel.dylib 0x1856933e0 mach_msg + 72
2 AudioToolbox 0x18982847c ASClient_AudioSessionCreateForPID + 168
3 AudioToolbox 0x189670fdc AudioSessionClient::AudioSessionClient(__CFRunLoop*, __CFString const*, void (*)(void*, unsigned int), void*, AudioSessionType, unsigned int) + 456
4 AudioToolbox 0x1897c36f4 AudioSessionClientManager::CreatePrimaryClient_Priv(__CFRunLoop*, __CFString const*, void (*)(void*, unsigned int), void*) + 568
5 AudioToolbox 0x1896721e8 invocation function for block in AudioSessionClientManager::CreatePrimaryClient(__CFRunLoop*, __CFString const*, void (*)(void*, unsigned int), void*) + 40
6 libdispatch.dylib 0x18551ea14 _dispatch_client_callout + 16
7 libdispatch.dylib 0x185527618 _dispatch_queue_barrier_sync_invoke_and_complete + 56
8 AudioToolbox 0x189671ef8 AudioSessionClientManager::CreatePrimaryClient(__CFRunLoop*, __CFString const*, void (*)(void*, unsigned int), void*) + 164
9 AudioToolbox 0x189671c50 AudioSessionClient::InitializeAudioSessionClient(__CFRunLoop*, __CFString const*, void (*)(void*, unsigned int), void*, AudioSessionType, unsigned int) + 92
10 AudioToolbox 0x189804c58 AudioSessionCreateSession_Priv + 600
11 AVFAudio 0x18b3d024c -[AVAudioSession initWithSessionType:] + 472
12 AVFAudio 0x18b3d1848 __32+[AVAudioSession sharedInstance]_block_invoke + 72
13 libdispatch.dylib 0x18551ea14 _dispatch_client_callout + 16
14 libdispatch.dylib 0x185522240 dispatch_once_f$VARIANT$mp + 60
15 AVFAudio 0x18b3d17fc +[AVAudioSession sharedInstance] + 112
16 AXSpeechImplementation 0x1a4c1f748 -[AVSpeechSynthesizer(Implementation) init]
17 Visuals2Go 0x1007ea430 -[SpeakManager init] (SpeakManager.m:47)

Answer 2

Looks like crash is due to dangling pointer, Use a shared speech session. This worked for me.
class mySpeechSynthesizerSession {
static let shared = mySpeechSynthesizerSession()
var speechSynthesizer: AVSpeechSynthesizer?
private init() {
speechSynthesizer = AVSpeechSynthesizer()
}
}