Crash Reporter for iPhone Applications (Part 1)

I’m getting ready to send my iPhone Application to the first beta testers and so I started thinking about crash reports.

On the Mac you have two options to get the crash report of your application. The first one is to check on startup if there is a new crash report file in ~/Library/Logs/CrashReporter for your application and simply send it. (Example: HDCrashReporter , UKCrashReporter)

The other option is to use NSExceptionHandler, which let you report the problem as it happens. (Example: A simple debugging tool for Cocoa)

On the iPhone you can’t access the crash report file form your application because it’s running in a sandbox (rdar://problem/6296554). iTunes synchronizes the crash reports of all applications, so although a user could in theory send it to you, this seems rather complicated to me (Locations of Crash Logs).

So what about NSExceptionHandler? Well, there isn’t a NSExceptionHandler in the iPhone SDK. But wait, there is a NSUncaughtExceptionHandler!

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1. void MyUncaughtExceptionHandler(NSException *exception) {
2.     NSArray *callStackArray = [exception callStackReturnAddresses];
3.     int frameCount = [callStackArray count];
4.     void *backtraceFrames[frameCount];
5.    
6.     for (int i=0; i<frameCount; i++) {
7.         backtraceFrames[i] = (void *)[[callStackArray objectAtIndex:i] unsignedIntegerValue];
8.     }
9.    
10.     // report the exception
11. }
12.  
13. @implementation AppDelegate
14.  
15. - (void)applicationDidFinishLaunching:(UIApplication *)application {
16.     NSSetUncaughtExceptionHandler(&MyUncaughtExceptionHandler);
17. }
18.  
19. @end

Now you can get the backtrace in MyUncaughtExceptionHandler with backtrace_symbols(3). (Example)
You still have to symbolicate the crash reports.

As a big fan of Fogbugz, I also wanted to use BugzScout. It’s just a HTTP POST, but here is the code:

1. void bugzScout(NSString *description, NSString *extra) {
2.         NSMutableString *post = [NSMutableString string];
3.         [post appendString:@"ScoutUserName="];
4.         [post appendString:urlEncodeValue(@"Your BugzScout User")];
5.        
6.         [post appendString:@"&ScoutProject="];
7.         [post appendString:urlEncodeValue(@"Your Project")];
8.        
9.         [post appendString:@"&ScoutArea="];
10.         [post appendString:urlEncodeValue(@"Your Area")];
11.        
12.         [post appendString:@"&Description="];
13.         [post appendString:urlEncodeValue(description)];
14.        
15.         [post appendString:@"&Extra="];
16.         [post appendString:urlEncodeValue(extra)];
17.        
18.         [post appendString:@"&ScoutDefaultMessage=&FriendlyResponse=0&ForceNewBug=0"];
19.        
20.         //NSLog(post);
21.        
22.         NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
23.         NSString *postLength = [NSString stringWithFormat:@"%d", [postData length]];
24.        
25.         NSURL *webServiceURL = [NSURL URLWithString:@"https://yourcompany.fogbugz.com/ScoutSubmit.asp"];
26.         NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:webServiceURL];
27.        
28.         [req setHTTPMethod:@"POST"];
29.         [req addValue:@"application/x-www-form-urlencoded" forHTTPHeaderField: @"Content-Type"];
30.         [req addValue:postLength forHTTPHeaderField: @"Content-Length"];
31.         [req setHTTPBody:postData];
32.        
33.         [NSURLConnection sendSynchronousRequest:req returningResponse:nil error:nil];   
34. }
35.  
36. NSString *urlEncodeValue(NSString *str) {
37.         CFStringRef urlString = CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
38.                 (CFStringRef)str, NULL, CFSTR(";/?:@&=+$,"), kCFStringEncodingUTF8);
39.         return [(NSString *)urlString autorelease];
40. }

Crash Reporter for iPhone Applications (Part 1)
Crash Reporter for iPhone Applications (Part 2)