How to understand this crash? - objective-c

Question

Crash report:
0 ??? 0x0 + 0
1 TestPrj -[AppListReader addInstalledApps:] (AppListReader.m:186) + 77516
2 TestPrj -[AppListReader getAppsInstalled] (AppListReader.m:161) + 77320
3 TestPrj -[DetectAppsInstalledService activate:] (DetectAppsInstalledService.m:48) + 197612
4 TestPrj -[BusinessManager handleBG] (BusinessManager.m:762) + 116672
5 TestPrj -[BusinessManager activate:] (BusinessManager.m:208) + 106236
6 TestPrj -[AppDelegate launchViewController:] (AppDelegate.m:338) + 32564
7 TestPrj -[AppDelegate application:didFinishLaunchingWithOptions:] (AppDelegate.m:153) + 27396
8 UIKit <redacted> + 316
9 UIKit <redacted> + 1564
10 UIKit <redacted> + 772
11 UIKit <redacted> + 3316
12 UIKit <redacted> + 104
13 UIKit <redacted> + 672
14 GraphicsServices <redacted> + 676
15 GraphicsServices <redacted> + 48
16 CoreFoundation <redacted> + 56
17 CoreFoundation <redacted> + 444
18 CoreFoundation <redacted> + 1620
19 CoreFoundation CFRunLoopRunSpecific + 452
20 UIKit <redacted> + 784
21 UIKit UIApplicationMain + 1156
22 TestPrj main (main.m:21) + 23548
23 libdyld.dylib <redacted> + 4
Line 186 is:
NSMutableArray *allObjetcsArr = [self getInstalled];
This is implementation:
-(NSMutableArray *)getInstalled
{
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:#"ApplicationType",#"Any", [self defaultReturnAttributes] ,#"ReturnAttributes",nil];
MobileInstallationLookup = dlsym(RTLD_DEFAULT, "MobileInstallationLookup");
NSDictionary *apps = (__bridge NSDictionary *)((__bridge void*)MobileInstallationLookup(options));
NSMutableArray *allObjetcsArr = [[NSMutableArray alloc]initWithArray:[apps allValues]];
return allObjetcsArr;
}
Crash is received via BugSense and I am not able to reproduce it. I think it is related to MobileInstallationLookup framework (which is private api) but I am not sure.
It is not clear for me, why
-(NSMutableArray *)getInstalled
Is not present in stack trace, only ??? 0x0 + 0

Answer 1

My money is on these lines:
MobileInstallationLookup = dlsym(RTLD_DEFAULT, "MobileInstallationLookup");
NSDictionary *apps = (__bridge NSDictionary *)((__bridge void*)MobileInstallationLookup(options));
MobileInstallationLookup is obviously a global, but it's not clear why; for example if it's global they why is it being re-assigned in this method and why does the variable start with a capital letter (which is unconventional)?
There is no check to ensure that dlsym() succeeded, and dereferencing a null pointer would cause the crash you are getting.