I trying to write a a crash report feature that when you launch the app after a crash, it will offer to send the crash report to the server. I can't find how to get the crash log within the app. I saw there is a framework that doing so (PLCrashReporter), however this framework is large and I don't need most of it's features.
Does anyone knows how to simply access the log?
Thanks,
Guy.
I guess I don't have the karma to add a comment to Nimrod Gat's answer, so I have to provide my follow-up here. I'll try to make it worthy of a standalone answer.
It's very, very difficult to write a safe, correct, and reliable crash reporter, especially one that runs directly in-process. The code referenced in Nimrod Gat's answer is not correct and honestly, that blog post should be retracted. Signal handlers must only run async-safe code, and that code isn't async-safe:
http://www.cocoadev.com/index.pl?SignalSafety
Crash handling is even more complicated than normal signal handling, because that you can't expect the process to continue to run successfully after your signal handler returns.
It's tempting to think you can just hack together a simpler solution, and it will work some of the time, but there's a good reason people like Google's engineers have thousands of LoC dedicated to reliable crash reporting:
http://code.google.com/p/google-breakpad/
On iOS, you should just use PLCrashReporter. On other platforms (such as Mac OS X) you should use Google Breakpad. There's no point in re-inventing this wheel unless you're going to do it not only correctly, but better than what already exists.
I had this similar issue and the PLCrashReported seemed too complicated for what I wanted to do.
Note that you can't access the crash report generated by Apple, the PLCrashReport generates it's own reports and store them in the user's cache folder.
Eventually, I used the following example:
http://cocoawithlove.com/2010/05/handling-unhandled-exceptions-and.html
it's very simple and easy to use, just register exception and signal handlers using:
NSSetUncaughtExceptionHandler(&HandleException);
signal(SIGABRT, SignalHandler);
signal(SIGILL, SignalHandler);
signal(SIGSEGV, SignalHandler);
signal(SIGFPE, SignalHandler);
signal(SIGBUS, SignalHandler);
signal(SIGPIPE, SignalHandler);
and get the stack trace using the backtrace method in UncaughtExceptionHandler class.
Maybe a better solution will be to use a fully specialized end-2-end solution/service? Such as http://apphance.com. It is currently in closed beta testing phase, but you can ask for participation and we'll get back to you pretty quickly. The only thing you need to do is to register for an API key and embed a small framework library into your app (or .jar file in android). Then you have remote access not only to crashlogs but also to a debug logs generated by the application - which makes it much more useful. It is for now targeted to be used during testing, but there will soon be a lite version that you will be able to embed into app-store-released application.
Inside the framework we are doing all the magic of plugging-into the apple's framework and getting the crashlog information, decoding stack traces, even handling out-of-memory cases. All the comments by #nupark hold very much true: We spend countless hours on making it works seamlessly - thread-safeness, making sure that we can do the job of saving everything within the time required by Apple's framework before your app get finally killed, getting stack trace from out-of-memory case (that one was really difficult). The same for android - we've done some clever tricks there to make sure it's really working fine.
Disclaimer: I am CTO of Polidea, company which is behind apphance and co-creator of the solution.
There are a bunch of (SAAS) E2E solutions that you may be very happy to know.
Very very simple to integrate into your application
Have Fun...
crashlytics (Free and my preferred)
hockeyapp
bugSense
Crittercism
In our days you may use the built-in crash reports (iOS & Android)
iOS (Itunes connect) - Viewing Crash Reports
Understanding Crash Reports
on iPhone OS
Reading Android Market Crash Reports
Related
Besides logging all NSExceptions in the main method, where else should I be capturing all error messages? E.g. if my app crashes due to accessing an over-released object, how can I get all the available information about the crash and write it to a local file on a device? I know how to do this in XCode but need to get this info from offsite QA testers.
When these memory errors occur, they don't seem to be caught by the main method.
Doing this really well is actually quite challenging. You're in the midst of a crash, which means that the system is in an undefined state. Small errors can lead to complete deadlock (if you crash while the heap is locked for instance, and then you try to allocate more memory). Unless you're looking for the learning experience of building and debugging it, you should reuse an existing framework. The best, IMO, is PLCrashReporter, which has gone through many iterations to get to its current state. It even integrates nicely with QuincyKit for crash report management on your own servers (plus several commercial solutions).
If you do decide to write your own (did I mention you shouldn't?), first study PLCrashReporter to see how they're doing it. If I had one most-important-rule, it would be: do as little as you possibly can during the crash, and then handle any complicated processing during the next launch.
The information in this post will probably help you. Basically, you can set a function in objective-c to be called when an unhanded exception or signal is met
Looks something like this:
NSSetUncaughtExceptionHandler(&HandleException);
signal(SIGABRT, SignalHandler);
signal(SIGILL, SignalHandler);
signal(SIGSEGV, SignalHandler);
signal(SIGFPE, SignalHandler);
signal(SIGBUS, SignalHandler);
signal(SIGPIPE, SignalHandler);
The rest of the post will describe how to set up these methods (HandleException and SignalHandler).
I work on an average (~ 20k lines of code, Objective-C mixed with C++), and I am figthing to hunt down an EXC_BAD_ACCESS error.
I have tried all the common techniques (like enabling NSZombie, guard edges,etc.) So far, I have ruled out the possibility to access a released object, and the double-free error.
It seems that something writes on a memory space where it shouldn't. But, as many memory errors, it's not happening all the time, and it's not crashing always in the same place.
(Sometimes I receive the "object was modified after being freed" message).
Sometimes, the overwritten memory belongs to the allocator, and it crashes on malloc, or on free().
And, of course, some changes in the app may influence the bug's behaviour - if I try to comment out parts of the code, the error appears less often, so it's more difficult to find it.
Finally, I have been looking into using valgrind, but it seems that all those who used it worked on the simulator. but my code must run on the actual device (some code is ARM-specific)
Are there any general tips on how to debug such errors?
Note: The app involves video processing, so the amount of memory used is fairly large.
There are some special tools available on the XCode. You could try to use them in order to analyse your code.
http://developer.apple.com/library/mac/#featuredarticles/StaticAnalysis/index.html
It will produce some warning in case of invalid objects usage so it could help you to find a problem.
If you feel that the C++ code is causing the issue you could copy the C++ out of your iPhone project and create a Mac project. With this you could set up various stress tests. And, you should be able to use valgrind as well.
I'm doing a small app which has TCP/IP server. I am familiar with BSD sockets and POSIX threads, but I selected CFSocket API. I wanted to do it in non-blocking/async/(very run-loop) scenario. I read a couple of tutorials and than started coding. Everything goes fine. Code for accepting connection works fine. I got 'kCFSocketAcceptCallBack' event. Things are not so good when I start to receive a data. I got BAD_EXC_ACCESS.
Code: http://www.nopaste.pl/18ka
It's my first 'hello world' app. I doesn't know very well X-Code, but it looks like "crash" occurs in internal 'select' function. My guess is CFSocket runs another thread which does 'select' all the time. Can anybody help ?
Whole project here: http://www.speedyshare.com/file/qbXjX/Playground.zip
If you run the app with no debugger, then the iOS will create a crash log which will detail the state of the stack.
You can retrieve the crash logs from the device with Xcode in the "Organizer" window.
EXC_BAD_ACCESS signals typically occur due to bad pointers.
I'm working with an Objective-C wrapper around SQLite that I didn't write, and documentation is sparse...
It's not FMDB. The people writing this wrapper weren't aware of FMDB when writing this code.
It seems that the code is suffering from a bug where database connections are being accessed from multiple threads -- which according to the SQLite documentation won't work if the if SQLite is compiled with SQLITE_THREADSAFE 2.
I have tested the libsqlite3.dylib provided as part of the iPhone SDK and seen that it is compiled in this manner, using the sqlite_threadsafe() routine.
Using the provided sqlite library, the code regularly hits SQLITE_BUSY and SQLITE_LOCKED return codes when performing routines.
To combat this, I added some code to wait a couple of milliseconds and try again, with a maximum retry count of 50. The code didn't contain any retry logic prior to this.
Now when a sqlite call returns SQLITE_BUSY or SQLITE_LOCKED, the retry loop is invoked and the retry returns SQLITE_MISUSE. Not good.
Grasping at straws, I replaced the provided sqlite library with a version compiled by myself setting SQLITE_THREADSAFE to 1 - which according to the documentation means sqlite is safe to be used in a multithreaded environment, effectively serialising all of the operations. It incurs a performance hit, that which I haven't measured, but it ridded the app of the SQLITE_MISUSE happening and seemed to not need the retry logic as it never hit a busy or locked state.
What I would rather do is fix the problem of accessing a single db connection from multiple threads, but I can't for the life of me find where it's occurring.
So if anyone has any tips on locating multithreaded bugs I would be extremely appreciative.
Thanks in advance.
I haven't tested this to see if it works, but you could try wrapping access to the db connection in a function and then using Instruments to log accesses to that function which, IIRC, should let you get a thread ID and a stack trace. That should give you a bit of a handle on where it's coming from. Alternatively you could just set a breakpoint on it but that might take a bit longer.
I'm trying to make a general error handler for an iPhone app that brings the user to a recovery screen whenever any general error is thrown in the application without putting a try/catch block around every single method in the application.
Using NSSetUncaughtExceptionHandler doesn't work because the application terminates after the handler is run.
Is there any way to change this behavior, or use any other handler that will catch exceptions in general and not cause the application to exit afterward?
And please, no non-answers about whether it's a good or bad idea.
The original poster has probably solved his problem by now. However, for anyone who comes across this in the future...
Matt Gallagher wrote an excellent post on catching unhandled exceptions and signals a few months after this question was posted. I find it to be much more informative than the answer referenced above by Scott.
In particular, Matt's post describes how to attempt a recovery (if appropriate) that allows your app to keep running, and even displays a UIAlertView with error information if you want (hint: it involves creating a new run loop).
This was answered here. You can read more about the responder chain and catching the exceptions here. The write up from 1 is really good and explains how to deal with what you are doing.