Because while the existing crash reporters do report crashes, there's a heck of a lot more that they COULD do. Here are some key features of KSCrash:
- On-device symbolication in a way that supports re-symbolication offline (necessary for iOS versions where many functions have been redacted).
- Generates full Apple reports, with every field filled in.
- 32-bit and 64-bit mode.
- Handles errors that can only be caught at the mach level, such as stack overflow.
- Tracks the REAL cause of an uncaught C++ exception.
- Handles a crash in the crash handler itself (or in the user crash handler callback).
- Detects zombie (deallocated) object access attempts.
- Recovers lost NSException messages in cases of zombies or memory corruption.
- Introspects objects in registers and on the stack (C strings and Objective-C objects, including ivars).
- Extracts information about objects referenced by an exception (such as "unrecognized selector sent to instance 0xa26d9a0")
- Its pluggable server reporting architecture makes it easy to adapt to any API service.
- Dumps the stack contents.
- Diagnoses crash causes (Crash Doctor).
- Records lots of information beyond what the Apple crash report can, in a JSON format.
- Supports including extra data that the programmer supplies (before and during a crash).
- Mach kernel exceptions
- Fatal signals
- C++ exceptions
- Objective-C exceptions
- Main thread deadlock (experimental)
- Custom crashes (e.g. from scripting languages)
Here are some examples of the reports it can generate.
That's right! Normally if your app terminates due to an uncaught C++ exception, all you get is this:
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x9750ea6a 0x974fa000 + 84586 (__pthread_kill + 10)
1 libsystem_sim_c.dylib 0x04d56578 0x4d0f000 + 292216 (abort + 137)
2 libc++abi.dylib 0x04ed6f78 0x4ed4000 + 12152 (abort_message + 102)
3 libc++abi.dylib 0x04ed4a20 0x4ed4000 + 2592 (_ZL17default_terminatev + 29)
4 libobjc.A.dylib 0x013110d0 0x130b000 + 24784 (_ZL15_objc_terminatev + 109)
5 libc++abi.dylib 0x04ed4a60 0x4ed4000 + 2656 (_ZL19safe_handler_callerPFvvE + 8)
6 libc++abi.dylib 0x04ed4ac8 0x4ed4000 + 2760 (_ZSt9terminatev + 18)
7 libc++abi.dylib 0x04ed5c48 0x4ed4000 + 7240 (__cxa_rethrow + 77)
8 libobjc.A.dylib 0x01310fb8 0x130b000 + 24504 (objc_exception_rethrow + 42)
9 CoreFoundation 0x01f2af98 0x1ef9000 + 204696 (CFRunLoopRunSpecific + 360)
...
No way to track what the exception was or where it was thrown from!
Now with KSCrash, you get the uncaught exception type, description, and where it was thrown from:
Application Specific Information:
*** Terminating app due to uncaught exception 'MyException', reason: 'Something bad happened...'
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 Crash-Tester 0x0000ad80 0x1000 + 40320 (-[Crasher throwUncaughtCPPException] + 0)
1 Crash-Tester 0x0000842e 0x1000 + 29742 (__32-[AppDelegate(UI) crashCommands]_block_invoke343 + 78)
2 Crash-Tester 0x00009523 0x1000 + 34083 (-[CommandEntry executeWithViewController:] + 67)
3 Crash-Tester 0x00009c0a 0x1000 + 35850 (-[CommandTVC tableView:didSelectRowAtIndexPath:] + 154)
4 UIKit 0x0016f285 0xb4000 + 766597 (-[UITableView _selectRowAtIndexPath:animated:scrollPosition:notifyDelegate:] + 1194)
5 UIKit 0x0016f4ed 0xb4000 + 767213 (-[UITableView _userSelectRowAtPendingSelectionIndexPath:] + 201)
6 Foundation 0x00b795b3 0xb6e000 + 46515 (__NSFireDelayedPerform + 380)
7 CoreFoundation 0x01f45376 0x1efa000 + 308086 (__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 22)
8 CoreFoundation 0x01f44e06 0x1efa000 + 306694 (__CFRunLoopDoTimer + 534)
9 CoreFoundation 0x01f2ca82 0x1efa000 + 207490 (__CFRunLoopRun + 1810)
10 CoreFoundation 0x01f2bf44 0x1efa000 + 204612 (CFRunLoopRunSpecific + 276)
...
If you turn on trace printing:
[KSCrash sharedInstance].printTraceToStdout = YES;It will print a proper stack trace to stdout whenever your app throws an uncaught C++ exception! Otherwise the debugger will only lead you to where the exception was rethrown.
You can now report your own custom crashes and stack traces (think scripting languages):
- (void) reportUserException:(NSString*) name
reason:(NSString*) reason
lineOfCode:(NSString*) lineOfCode
stackTrace:(NSArray*) stackTrace
terminateProgram:(BOOL) terminateProgram;See KSCrash.h for details.
The following features should be considered "unstable" and are disabled by default:
- Deadlock detection
As of Jan 29th, 2013, I've modified the KSCrash main API to use properties rather than init method parameters for configuration. With all the new options, things were starting to get a bit unwieldly. This should mark the last major API change.
Note: The preferred method for initializing KSCrash is now via the installation objects rather than using filters directly. See "How to Use KSCrash" for details.
- Select the KSCrash scheme.
- Choose iOS Device.
- Select Archive from the Products menu.
When it has finished building, it will show you the framework in Finder. You can use it like you would any other framework.
-
Add the framework to your project (or add the KSCrash project as a dependency)
-
Add the following system frameworks & libraries to your project:
- libc++.dylib
- libz.dylib
- MessageUI.framework (iOS only)
- SystemConfiguration.framework
-
Add the flag "-ObjC" to Other Linker Flags in your Build Settings
-
Add the following to your [application: didFinishLaunchingWithOptions:] method in your app delegate:
#import <KSCrash/KSCrash.h>
// Include to use the standard reporter.
#import <KSCrash/KSCrashInstallationStandard.h>
// Include to use Quincy or Hockey.
#import <KSCrash/KSCrashInstallationQuincyHockey.h>
// Include to use the email reporter.
#import <KSCrash/KSCrashInstallationEmail.h>
// Include to use Victory.
#import <KSCrash/KSCrashInstallationVictory.h>
- (BOOL)application:(UIApplication*) application didFinishLaunchingWithOptions:(NSDictionary*) launchOptions
{
KSCrashInstallationStandard* installation = [KSCrashInstallationStandard sharedInstance];
installation.url = [NSURL URLWithString:@"http://put.your.url.here"];
// OR:
KSCrashInstallationQuincy* installation = [KSCrashInstallationQuincy sharedInstance];
installation.url = [NSURL URLWithString:@"http://put.your.url.here"];
// OR:
KSCrashInstallationHockey* installation = [KSCrashInstallationHockey sharedInstance];
installation.appIdentifier = @"PUT_YOUR_HOCKEY_APP_ID_HERE";
// OR:
KSCrashInstallationEmail* installation = [KSCrashInstallationEmail sharedInstance];
installation.recipients = @[@"some@email.address"];
// Optional (Email): Send Apple-style reports instead of JSON
[installation setReportStyle:KSCrashEmailReportStyleApple useDefaultFilenameFormat:YES];
// Optional: Add an alert confirmation (recommended for email installation)
[installation addConditionalAlertWithTitle:@"Crash Detected"
message:@"The app crashed last time it was launched. Send a crash report?"
yesAnswer:@"Sure!"
noAnswer:@"No thanks"];
// OR:
KSCrashInstallationVictory* installation = [KSCrashInstallationVictory sharedInstance];
installation.url = [NSURL URLWithString:@"https://put.your.url.here/api/v1/crash/<application key>"];
[installation install];
…
}This will install the crash sentry system (which intercepts crashes and stores reports to disk). Note that there are other properties you can and probably will want to set for the various installations.
Once you're ready to send any outstanding crash reports, call the following:
[installation sendAllReportsWithCompletion:^(NSArray *filteredReports, BOOL completed, NSError *error)
{
// Stuff to do when report sending is complete
}];If possible, you should read the following header files to fully understand what features KSCrash has, and how to use them:
- KSCrash.h
- KSCrashAdvanced.h
- KSCrashInstallation.h
- KSCrashInstallation(SPECIFIC TYPE).h
- Architecture.md
On-device symbolication requires basic symbols to be present in the final build. To enable this, go to your app's build settings and set Strip Style to Debugging Symbols. Doing so increases your final binary size by about 5%, but you get on-device symbolication.
KSCrash has advanced functionality that can be very useful when examining crash reports in the wild. Some involve minor trade-offs, so most of them are disabled by default.
You can store custom user data to the next crash report by setting the userInfo property in KSCrash.h.
KSCrash has the ability to detect zombie instances (dangling pointers to deallocated objects). It does this by recording the address and class of any object that gets deallocated. It stores these values in a cache, keyed off the deallocated object's address. This means that the smaller you set the cache size, the greater the chance that a hash collision occurs and you lose information about a previously deallocated object.
With zombie tracking enabled, KSCrash will also detect a lost NSException and print its contents. Certain kinds of memory corruption or stack corruption crashes can cause the exception to deallocate early, further twarting efforts to debug your app, so this feature can be quite handy at times.
Each cache entry takes up 8 bytes on a 32-bit architecture, and 16 bytes on a 64-bit architecture. The recommended minimum is 16384, which translates to 128k of RAM used for zombie tracking on a 32-bit machine. Generally, the more objects you tend to have in your app, the larger you'll want to make the cache.
Trade off: Zombie tracking at the cost of adding very slight overhead to object deallocation, and having some memory reserved.
WARNING WARNING WARNING WARNING WARNING WARNING WARNING
This feature is UNSTABLE! It can false-positive and crash your app!
If your main thread deadlocks, your user interface will become unresponsive, and the user will have to manually shut down the app (for which there will be no crash report). With deadlock detection enabled, a watchdog timer is set up. If anything holds the main thread for longer than the watchdog timer duration, KSCrash will shut down the app and give you a stack trace showing what the main thread was doing at the time.
This is wonderful, but you must be careful: App initialization generally occurs on the main thread. If your initialization code takes longer than the watchdog timer, your app will be forcibly shut down during start up! If you enable this feature, you MUST ensure that NONE of your normally running code holds the main thread for longer than the watchdog value! At the same time, you'll want to set the timer to a low enough value that the user doesn't become impatient and shut down the app manually before the watchdog triggers!
Trade off: Deadlock detection, but you must be a lot more careful about what runs on the main thread!
When an app crashes, there are usually objects and strings in memory that are being referenced by the stack, registers, or even exception messages. When enabled, KSCrash will introspect these memory regions and store their contents in the crash report.
You can also specify a list of classes that should not be introspected by setting the doNotIntrospectClasses property in KSCrash.
If you want to do some extra processing after a crash occurs (perhaps to add more contextual data to the report), you can do so.
However, you must ensure that you only use async-safe code, and above all else never call Objective-C code from that method! There are many cases where you can get away with doing so anyway, but there are certain classes of crashes where handler code that disregards this warning will cause the crash handler to crash! Note that if this happens, KSCrash will detect it and write a full report anyway, though your custom handler code may not fully run.
Trade off: Custom crash handling code, but you must be careful what you put in it!
This takes whatever KSCrash would have printed to the console, and writes it to a file instead. I mostly use this for debugging KSCrash itself, but it could be useful for other purposes, so I've exposed an API for it.
The workspace includes some example apps, which demonstrate common KSCrash usage. Please look at the top of AppDelegate.m in each app for a description of what it does.
Copyright (c) 2012 Karl Stenerud
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in the documentation of any redistributions of the template files themselves (but not in projects built using the templates).
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