Manage Unhandled Exception and Crashes in a Mac Cocoa App

Question

I am implementing a Mac App and I want to handle following events:

• Unhandled Exception
• Program Crash (memory error dcc)

If I detect them, I can send details to me to analyze and fix bugs using one of the Crash Handlers that I found. Alas I am unable to figure out how to intercept crashes and exceptions.

1. First question: Have I to differentiate Exceptions from Crashes ? Or detecting Exception is enough?
2. How can I catch Exceptions and/or crashes redirecting them to my handler ?

PS I tried following in my MyApp class

NSSetUncaughtExceptionHandler(&uncaughtExceptionHandler);
signal(SIGABRT, SignalHandler);
signal(SIGILL, SignalHandler);
signal(SIGSEGV, SignalHandler);
signal(SIGFPE, SignalHandler);
signal(SIGBUS, SignalHandler);
signal(SIGPIPE, SignalHandler);

but it doesn't work. Every time it crashes, it goes to debugger without classing SignalHandler or uncaughtExceptionHandler

Answer 1

I have found the best way is to create a simple Exception handling delegate class as this allows exceptions in IBAction methods to be caught.

main.mm:

@interface ExceptionDelegate : NSObject
@end
static ExceptionDelegate *exceptionDelegate = nil; 


int main(int argc, char **argv)
{
    int retval = 1;

    @autoreleasepool
    {
        //
        // Set exception handler delegate
        //
        exceptionDelegate = [[ExceptionDelegate alloc] init];
        NSExceptionHandler *exceptionHandler = [NSExceptionHandler defaultExceptionHandler];
        exceptionHandler.exceptionHandlingMask = NSLogAndHandleEveryExceptionMask;
        exceptionHandler.delegate = exceptionDelegate;

        //
        // Set signal handler
        //
        int signals[] =
        {
            SIGQUIT, SIGILL, SIGTRAP, SIGABRT, SIGEMT, SIGFPE, SIGBUS, SIGSEGV,
            SIGSYS, SIGPIPE, SIGALRM, SIGXCPU, SIGXFSZ
        };
        const unsigned numSignals = sizeof(signals) / sizeof(signals[0]);
        struct sigaction sa;
        sa.sa_sigaction = signalHandler;
        sa.sa_flags = SA_SIGINFO;
        sigemptyset(&sa.sa_mask);
        for (unsigned i = 0; i < numSignals; i++)
            sigaction(signals[i], &sa, NULL);

        ....
    }

    ....

    return retval;    
}


static void signalHandler(int sig, siginfo_t *info, void *context)
{
    logerr(@"Caught signal %d", sig);
    exit(102);
}

@implementation ExceptionDelegate

- (BOOL)exceptionHandler:(NSExceptionHandler *)exceptionHandler
      shouldLogException:(NSException *)exception
                    mask:(unsigned int)mask
{
    logerr(@"An unhandled exception occurred: %@", [exception reason]);
   return YES;
}

- (BOOL)exceptionHandler:(NSExceptionHandler *)exceptionHandler
   shouldHandleException:(NSException *)exception
                    mask:(unsigned int)mask
{
    exit(101);

    // not reached
    return NO;
}

@end

You'll need to add the ExceptionHandling.framework to your project.