XCode 12 & iOS 14 getting crash and not able to know exact reason

The immediate cause of your crash is this:

Code Block  
Exception Type:  EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000001, 0x000000019a1add00

This strongly suggests that you’ve hit a trap, that is, the code has detected an unrecoverable problem and deliberately crashed.

Consider the backtrace of the crashing thread:

Code Block  
Thread 6 name:  Dispatch queue: ELEReportPDFRenderer
Thread 6 Crashed:
0   libdispatch.dylib       … _dispatch_assert_queue_fail + 112
1   libdispatch.dylib       … _dispatch_assert_queue_fail + 104
2   libdispatch.dylib       … dispatch_assert_queue$V2$VARIANT$armv81 + 144
3   UIKitCore               … -[UIImageView _mainQ_beginLoadingIfApplicable] + 72
…
23  UIKitCore               … -[UINib instantiateWithOwner:options:] + 1064
24  elektra                 … +[UIView(Elektra) instantiateWithNibName:bundle:owner:] + 86793224 (UIView+El…
25  elektra                 … +[UIView(Elektra) instantiateFromNibWithOwner:] + 86790452 (UIView+Elektra.m:…
26  elektra                 … +[ELEMeasurementView measurementViewWithReuseIdentifier:] + 40093136 (ELEMeas…
27  elektra                 … +[ELEMeasurementView measurementViewConfiguredForMeasurement:completionBlock:…
28  elektra                 … -[ELEBasicReportPDFRenderer drawMeasurementGroup:] + 18411720 (ELEBasicReport…
29  elektra                 … -[ELEReportPDFRenderer PDFData] + 45446276 (ELEReportPDFRenderer.m:390)
30  elektra                 … +[ELEReportPDFRenderer PDFDataFromReport:progressBlock:] + 45398428 (ELERepor…
31  elektra                 … __50-[ELEReportContentPreferencesController createPDF]_block_invoke + 4499318…
32  libdispatch.dylib       … _dispatch_call_block_and_release + 24
33  libdispatch.dylib       … _dispatch_client_callout + 16
34  libdispatch.dylib       … _dispatch_lane_serial_drain$VARIANT$armv81 + 568
35  libdispatch.dylib       … _dispatch_lane_invoke$VARIANT$armv81 + 404
36  libdispatch.dylib       … _dispatch_workloop_worker_thread + 692
37  libsystem_pthread.dylib … _pthread_wqthread + 272
38  libsystem_pthread.dylib … start_wqthread + 8

Frame 38 shows that this is a dispatch worker thread. Frames 31 through 24 are your code, which then calls UIKit at frame 23. This is not legal. You are not allowed to call UIKit from a secondary thread; you can only call it from the main thread.

UIKit has detected this problem and trapped.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@apple.com"

Did you ever find a solution to this. I seem to be having something similar.

In one case, I had a message in the log with the statement
BRossTools[2569]: BUG IN CLIENT OF LIBDISPATCH: Assertion failed: Block was expected to run on queue [com.apple.main-thread]

I'm going to try to get things a little more organized and then I can post my code. It seems to occur when I try to capture a key press on the MIDI keyboard

@HighlyExperienced

You need redesign your code to make it main-thread-safety or you can use this snippet for working with UIKit:

void vkm_sync_main(dispatch_block_t block) {
    if (block == nil) return;
    if ([NSThread isMainThread]) {
        block();
    } else {
        dispatch_sync(dispatch_get_main_queue(), block);
    }
}