App crashes before debugger can connect - ios

Question

I've got an app that crashes even before the debugger can connect.
I placed a break point on the first line of main(). (I added an NSLog statement as very first statement in main() and set the break point there.
The app seems to start. The main screen with some ui elements becomes visible on the screen. Then it disappears.
There is no crash log found on the devices.
Xcode message:
Could not launch "appname"
process launch failed: failed to get the task for process xyz
Debugging is enabled of course.
The same for the profiler Instruments.
Code signing works fine so that the app can be deployed to the devices.
(Same for enterprise distribution. And the app validates for store submission.)
It does work on the simulator though.
The app used to work fine. I was just about to build it for the store. For final tests on iOS 8.1 I upgraded to Xcode 6.1 with SDK 8.1. But the problem did not occur directly after the upgrade. It worked just fine.
Then it crashed when building for release for enterprise distribution.
The AppStore build crashed in the same manner (according to Apple, the app was rejected of course.)
But it ran nicely in debug modes.
Now I was trying whether compiler options for optimization may make all the difference and I was trying to build in release mode with debugging enabled etc and end up with a debug build crashing as well. (No optimization in debug).
So it may well be that the migration to Xcode 6.1 did cause it but the problem may have come effective only after Xcode cleaned and rebuild the project in response to changes to compiler settings for code optimization.
Sorry for the long text. I tried to put everything in that may be of importance.

Answer 1

Reason is most likely some incompatibility of Crackify and iOS 8.1.
Therefore it may be of interest for others, altough my problem along with these symptoms may be very special.
Very early within AppDelegate didFinishLaunchingWithOptions we have had the following statement.
if ([Crackify isCracked] || [self isCertificateUnvalid])
exit(173);
That, as such, is not really well designed. The app is just terminated rather than any error message displayed to the user. Thus, it appears as if the app has crashed. But it has not crashed and therefore no crashlog is provided.
For reasons which I don't yet understand and which may not be related to this error, my debugger did not manage to hook up into the executed app. Once that was overcome (suddenly the debugger worked without any changes made to any of the debugging related settings) the error was found rather quickly.
This is Crackify: https://github.com/itruf/crackify
Within Crackify it was this code sniplet that caused the problem:
static NSString *str2 = #"ResourceRules.plist";
BOOL fileExists3 = [manager fileExistsAtPath:([NSString stringWithFormat:#"%#/%#", bundlePath, str2])];
if (!fileExists3) {
return YES;
}
For reasons that I did not further investigate, the file, that is tested here, apparently does not exist in iOS 8.1 any more.