Question

I’ve noticed some strange behavior in iOS 5: NSSetUncaughtExceptionHandler() doesn’t seem to do anything anymore.

I have the following code:

static NSString* documentsDirectory()
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
    return basePath;
}

static void handleException(NSException *exception)
{
    // Write something to the documents dir
    NSString* path = [documentsDirectory() stringByAppendingPathComponent:@"crashlog.txt"];
    NSString* str = @"Handled exception";
    NSError* err;
    if(![str writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:&err])
    {
        NSLog(@"Failed to write to file");
    }
    NSLog(@"Handled exception");
}


@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    NSSetUncaughtExceptionHandler(&handleException);
    [NSException raise:@"Test" format:@"Testing"];

    ...
}

The above code works on any device or simulator running 4.x or earlier. However, when I run it on the 5.0 simulator, the exception handler doesn’t get called (doesn’t write the file to the documents dir, doesn’t log, and doesn’t trigger if I set a breakpoint inside the handler).

Unfortunately, I don’t have a 5.0 device available for testing, so I’m hoping someone could confirm that it’s broken on 5.0 so I can file a bug report (or correct me, if there’s a problem with my code).

Answer 1

Use iOS 6.0 SDK, build and run it on simulator 5.0! It works!

//////Code:

static NSString* documentsDirectory()
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
    return basePath;
}

static void handleException(NSException *exception)
{
    // Write something to the documents dir
    NSString* path = [documentsDirectory() stringByAppendingPathComponent:@"crashlog.txt"];
    NSString* str = @"Handled exception";
    NSError* err;
    if(![str writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:&err])
    {
        NSLog(@"Failed to write to file");
    }
    NSLog(@"Handled exception");
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    NSSetUncaughtExceptionHandler(&handleException);
    [NSException raise:@"Test" format:@"Testing"];

    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    // Override point for customization after application launch.
    self.viewController = [[[NSSetUncaughtExceptionHandlerTestViewController alloc] initWithNibName:@"NSSetUncaughtExceptionHandlerTestViewController" bundle:nil] autorelease];
    self.window.rootViewController = self.viewController;
    [self.window makeKeyAndVisible];
    return YES;
}

//////Terminal log:

2012-10-09 20:06:24.726 NSSetUncaughtExceptionHandlerTest[7815:c07] Handled exception
2012-10-09 20:06:24.727 NSSetUncaughtExceptionHandlerTest[7815:c07] *** Terminating app due to uncaught exception 'Test', reason: 'Testing'
*** First throw call stack:
(0x14a4052 0xea4d0a 0x144ca78 0x144c9e9 0x29d7 0x129d6 0x138a6 0x22743 0x231f8 0x16aa9 0x138efa9 0x14781c5 0x13dd022 0x13db90a 0x13dadb4 0x13daccb 0x132a7 0x14a9b 0x28b2 0x27e5)
terminate called throwing an exception(lldb)