Looks like some kind of sandbox issue with the OS X operating system (which is 
running the Simulator).  The issue is not actually in the iOS code.  On my 
workstation running the Simulator, the access function is returning -50 (access 
denied) for your MIDI file URL — but only for the *first* time it tries to 
access it.  All subsequent attempts succeed for me.

The -50 error status is getting lost so you only see -1 — this is a separate 
issue that should be fixed in a subsequent OS release.

-DS

> On Sep 15, 2016, at 2:49 PM, Sven Thoennissen <[email protected]> wrote:
> 
> Hi Douglas, Derek,
> 
> I have filed bug report #28327056 that describes the issue, with a small 
> sample project including a MIDI file attached.
> 
> I have noticed that result code -1 happens 1-2 out of 10 times when calling 
> MusicSequenceFileLoad() in the background dispatch queue.
> On the main queue the function always returns 0.
> 
> Btw if you add a breakpoint "All Exceptions" Xcode will break there.
> 
> For me it happens even with iOS 9 (where it did work for Derek though).
> 
> Sven
> 
>> 
>> Can you zip up the MIDI file and attach it to a reply here?
>> 
>> In addition, if you would please file a radar (and attach the MIDI file 
>> there as well) and include the ID of that radar in your reply here, it would 
>> really help move this issue along.
>> 
>> Thanks!!
>> 
>> -DS
>> 
>>> On Sep 11, 2016, at 7:25 AM, down to this <[email protected]> wrote:
>>> 
>>> I've encountered a crash when invoking the AudioToolbox / MusicPlayer API 
>>> method "MusicSequenceFileLoad()" to load the contents of a MIDI file (from 
>>> the given URL) into a music sequence on an iOS10 device and would greatly 
>>> appreciate some assistance from the community. 
>>> 
>>> Observations I've been able to make thus far:
>>> 
>>> * The first time the VC is displayed which uses this MIDI file all 
>>> processing runs without any issues. It's only the second time that the VC 
>>> is loaded where the app crashes. (Which makes me believe that this may be 
>>> related to memory management.) The issue can be recreated consistently. 
>>> 
>>> * This code has been working without issue in production on iOS7, 8, and 9 
>>> for 2+ years and also runs without issue on the iOS 10 Simulator but 
>>> crashes silently on a iOS 10 device (iPad Pro). Device is running iOS 
>>> 10.0.1. 
>>> 
>>> * No crash report is created on the device when this issue is encountered. 
>>> No exception information or call stack is available when debugging within 
>>> Xcode. 
>>> 
>>> * Checking the OSStatus result code from calling this function simply 
>>> returns a value of -1 and does not indicate the reason for the failure. 
>>> 
>>> * Profiling for memory management issues (allocations, leaks, zombies), has 
>>> not shown any information related to the crash. 
>>> 
>>> * Turning on the Zombie Objects option did not reveal any Zombie Objects. 
>>> 
>>> * Analyzing the application did not reveal any areas where memory was not 
>>> being released. 
> 
> 
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