1.92.8 Crash report

[ftolsson]

Just updated to 1.92.8 and got a crash while writing — it might be caused by my plugin, but if so it's a crash I've never experienced in previous builds so there's probably something that has changed in the app regardless...

The (I suppose) most telling info is this:

Application Specific Information:
*** Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection <__NSArrayM: 0x600001fdd380> was mutated while being enumerated.'
terminating with uncaught exception of type NSException
abort() called

But I'll send you the entire crashlog as a pm on discord if you want it. Here's hoping it was a one-off (or a seldom-off, at least).

[lmparppei]

Could you copy-paste the whole crash report or at least the callback stack?

[ftolsson]

Me and terminology... 😊

Here's hoping this is what you're asking for:

Exception Type:        EXC_CRASH (SIGABRT)
Exception Codes:       0x0000000000000000, 0x0000000000000000
Exception Note:        EXC_CORPSE_NOTIFY

Application Specific Information:
*** Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection <__NSArrayM: 0x600001fdd380> was mutated while being enumerated.'
terminating with uncaught exception of type NSException
abort() called

Application Specific Backtrace 1:
0   CoreFoundation                      0x00007fff2065b1db __exceptionPreprocess + 242
1   libobjc.A.dylib                     0x00007fff20394d92 objc_exception_throw + 48
2   CoreFoundation                      0x00007fff206d72f3 __NSFastEnumerationMutationHandler + 151
3   CoreFoundation                      0x00007fff205a8517 -[NSArray indexOfObject:] + 222
4   Beat                                0x0000000101d3bfd3 Beat + 614355
5   Beat                                0x0000000101d4cc32 Beat + 683058
6   CoreFoundation                      0x00007fff205c46fc __invoking___ + 140
7   CoreFoundation                      0x00007fff205c459d -[NSInvocation invoke] + 305
8   JavaScriptCore                      0x00007fff368f1f7f _ZN3JSC24ObjCCallbackFunctionImpl4callEP9JSContextP13OpaqueJSValuemPKPKS3_PS6_ + 431
9   JavaScriptCore                      0x00007fff368f1957 _ZN3JSCL34objCCallbackFunctionCallAsFunctionEPK15OpaqueJSContextP13OpaqueJSValueS4_mPKPKS3_PS6_ + 231
10  JavaScriptCore                      0x00007fff368f48d0 _ZN3JSC19APICallbackFunction8callImplINS_20ObjCCallbackFunctionEEExPNS_14JSGlobalObjectEPNS_9CallFrameE + 576
11  JavaScriptCore                      0x00007fff368811a4 llint_entry + 116597
12  JavaScriptCore                      0x00007fff3687f0a8 llint_entry + 108153
13  JavaScriptCore                      0x00007fff36864836 vmEntryToJavaScript + 216
14  JavaScriptCore                      0x00007fff36ed9796 _ZN3JSC11Interpreter11executeCallEPNS_14JSGlobalObjectEPNS_8JSObjectERKNS_8CallDataENS_7JSValueERKNS_7ArgListE + 518
15  JavaScriptCore                      0x00007fff371146e4 _ZN3JSC12profiledCallEPNS_14JSGlobalObjectENS_15ProfilingReasonENS_7JSValueERKNS_8CallDataES3_RKNS_7ArgListE + 164
16  JavaScriptCore                      0x00007fff3652fb37 JSObjectCallAsFunction + 807
17  JavaScriptCore                      0x00007fff36632460 -[JSValue callWithArguments:] + 432
18  Beat                                0x0000000101d47cc9 Beat + 662729
19  libdispatch.dylib                   0x00007fff2033e623 _dispatch_call_block_and_release + 12
20  libdispatch.dylib                   0x00007fff2033f806 _dispatch_client_callout + 8
21  libdispatch.dylib                   0x00007fff20341e37 _dispatch_queue_override_invoke + 775
22  libdispatch.dylib                   0x00007fff2034e818 _dispatch_root_queue_drain + 326
23  libdispatch.dylib                   0x00007fff2034ef70 _dispatch_worker_thread2 + 92
24  libsystem_pthread.dylib             0x00007fff204e6417 _pthread_wqthread + 244
25  libsystem_pthread.dylib             0x00007fff204e542f start_wqthread + 15

[lmparppei]

The crash happens in ContinuousFountainParser after requesting for lines in a scene, because the .lines array was mutated while in a for loop. linesForScene was called in JS, so the crash itself was caused by your plugin, but the bug is probably mine. The method should make a copy of lines array if not in main thread.

[lmparppei]

NO! Actually, the mutation took place when trying to ask for the index of scene heading. I've already taken some steps to avoid this, but seemingly not enough.

[ftolsson]

I see -- me asking for that index, or you?

I was writing mid-scene, so theoretically a. it could be me, but b. it shouldn't be me because I should be debouncing stuff while writing. But who knows, once the code is large enough I guess lots of things are happening all the time... Main question though: Did you recently change something? Because most importantly c. this is a crash I've never seen before.

[lmparppei]

I changed some stuff in the Outline View, but that shouldn't cause this, because it relies on the same outline stuff. I'm pretty sure this was a rare one-off, where your JS code tried to ask for lines in a scene in the background, and at the same nanosecond, you managed to press a key.

I put an extra thread check into the method, so let's hope that fixes the problem. I'll post a beta tomorrow.

[ftolsson]

and at the same nanosecond, you managed to press a key.

Storytelling is all about timing!

[ftolsson]

Also: thanks! 👍

[lmparppei]

This should be fixed with the use of .safeLines. Let's open it up again if something happens.