Re: Crash with ARC enabled on Xcode 6.1
Re: Crash with ARC enabled on Xcode 6.1
- Subject: Re: Crash with ARC enabled on Xcode 6.1
- From: Kevin Meaney <email@hidden>
- Date: Thu, 23 Oct 2014 17:50:06 +0100
Personally I'd try and not call any objective-c code from a C++ static object. If it did look the appropriate solution then I'd make sure I was comfortable with my knowledge of the objective-c runtime and the order in which things are called before main is called.
Kevin
On 23 Oct 2014, at 13:02, Beinan Li <email@hidden> wrote:
> Thank you Kevin!
> I didn't know this before. This might be it because I did at some point change the dictionary creation from the old API-based syntax to literals.
> Maybe I should move back to the API calls. I'll try that today.
>
> Thanks,
> Beinan
>
>
> On Thu, Oct 23, 2014 at 5:18 AM, Kevin Meaney <email@hidden> wrote:
>
> On 23 Oct 2014, at 00:34, Beinan Li <email@hidden> wrote:
>
>> Oh! I did actually.
>>
>> The method I posted belongs to an ObjC object which is wrapped by a C++ object.
>> That C++ object is a singleton (static).
>>
>> How is this going to affect ARC and why it didn't down-right crash a week ago before I upgraded Xcode?
>
> I wouldn't worry about why it worked before. I don't think that helps, and if you have any other cases they should be removed as well.
>
> Array and dictionary literals are not evaluated at compile time but are replaced with the objective-c calls to create the arrays and dictionaries. This is very different to string literals.
>
> From what I understand any code that is executed before main is called is done so before the objective-c runtime is fully setup which means you have no guarantees about what will work. In objective-c++ where you can create static C++ objects that results in objective-c being called it is an easy way to make difficult to track crashes.
>
> I'd like confirmation from an apple engineer that my understanding is correct. My quick perusal of the docs didn't find the info I was after.
>
> Kevin
>
>> Thanks,
>> Beinan
>>
>>
>> On Wed, Oct 22, 2014 at 7:00 PM, Kevin Meaney <email@hidden> wrote:
>> Your not creating a static C++ object anywhere are you? One that creates the dictionary before main gets called by any chance?
>>
>> Kevin
>>
>> Sent from my iPhone
>>
>> > On 22 Oct 2014, at 22:45, Beinan Li <email@hidden> wrote:
>> >
>> > Note, the initial crashing function is merely translating a C++ enum to the
>> > AVFoundation builtin constants.
>> >
>> > Thanks,
>> > Beinan
>> >
>> >
>> >> On Wed, Oct 22, 2014 at 5:45 PM, Beinan Li <email@hidden> wrote:
>> >>
>> >> It is quite unpredictable.
>> >> At first it crashes at a dictionary creation line in a .mm implementation
>> >> like this:
>> >>
>> >> - (NSString*) getAVAudioSessionMode:(myAudioSessionMode)modeKey {
>> >> NSDictionary* modeDict = @{ // Here it crashes
>> >> @(myAudioSessionModeDefault): AVAudioSessionModeDefault,
>> >> @(myAudioSessionModeVoiceChat): AVAudioSessionModeVoiceChat,
>> >> @(myAudioSessionModeGameChat): AVAudioSessionModeGameChat,
>> >> @(myAudioSessionModeVideoRecording): AVAudioSessionModeVideoRecording,
>> >> @(myAudioSessionModeMeasurement): AVAudioSessionModeMeasurement,
>> >> @(myAudioSessionModeMoviePlayback): AVAudioSessionModeMoviePlayback,
>> >> @(myAudioSessionModeVideoChat): AVAudioSessionModeVideoChat
>> >> };
>> >> NSString* mode = [modeDict objectForKey:@
>> >> (mySettings.audioSession.eMode)];
>> >> return mode;
>> >> }
>> >>
>> >> The backtrace gives me:
>> >>
>> >> * thread #1: tid = 0x2403, 0x0013148c MyDemo`-[MyImp
>> >> getAVAudioSessionMode:](self=0x1e839a80, _cmd=0x002d3077,
>> >> modeKey=myAudioSessionModeDefault) + 676 at MyImp.mm:78, queue =
>> >> 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
>> >> * frame #0:
>> >> 0x0013148c MyDemo -[MyImp getAVAudioSessionMode:](self=0x1e839a80,
>> >> _cmd=0x002d3077, modeKey=myAudioSessionModeDefault) + 676 at MyImp.mm:78
>> >>
>> >> Then if I remove this dictionary all together and do it like this:
>> >>
>> >> - (NSString*) getAVAudioSessionMode:(myAudioSessionMode)modeKey {
>> >> return AVAudioSessionModeDefault;
>> >> }
>> >>
>> >> Then I get a crash right in the main.mm:
>> >>
>> >> int retVal = UIApplicationMain(argc, argv, nil, @"MyDemoAppDelegate");
>> >>
>> >> backtrace:
>> >>
>> >> * thread #1: tid = 0x2403, 0x3c4df350
>> >> libsystem_kernel.dylib`__pthread_kill + 8, queue = 'com.apple.main-thread',
>> >> stop reason = signal SIGABRT
>> >> frame #0: 0x3c4df350 libsystem_kernel.dylib`__pthread_kill + 8
>> >> frame #1: 0x3c456122 libsystem_c.dylib`pthread_kill + 58
>> >> frame #2: 0x3c492972 libsystem_c.dylib`abort + 94
>> >> frame #3: 0x3ba30d4e libc++abi.dylib`abort_message + 74
>> >> frame #4: 0x3ba2dff8 libc++abi.dylib`default_terminate() + 24
>> >> frame #5: 0x3bfe1a
>>
>
>
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