I'm working on a basic libusb Visual C++ application in vs2013, which has a Class that calls libusb_get_device_list(ctx, devices) 3 times; once in the constructor, and twice in two functions for printing devices and device descriptions. Each time I call libusb_free_device_list(devices, 1) to release the devices. In the Destructor, I call
libusb_close(deviceHandle);
libusb_exit(ctx);
Nothing breaks, but the libusb_exit(ctx) spits out the warning: libusb: warning [libusb_exit] some libusb_devices were leaked
If I only call libusb_get_device_list(ctx, devices) once, the warning doesn't show.
Has anyone had the same issue and found a way to resolve it?
NOTE:
Whether I use the same instance of libusb_device** or three unique ones, the problem persists
Update:
This solution does not seem to work every time. For some reason it makes the program throw exceptions sometimes, which I did see the first couple of times I was testing it.
Original Response:
I managed to resolve it myself. It seemed that if I get device list and free it again in constructor. I can still use the freed libusb_device** instance to print the connected devices without creating a new instance or freeing it again.
If anyone one can explain why this is to me, it would still be greatly appreciated as I do not understand why my work around is working and why other setups don't work.
Related
I have a random Runtime Error 216 that appears on application close.
I have debugged as far as I can and the error is thrown in SysUtils.FinalizeUnits.
I have gone over the code and ensure all created objects are freed.
The number on the runtime error, 0040054A, is not present in the mapfile. Do you know what this means?
Can anyone tell me how to find out what is throwing the error?
This is VERY OLD Delphi problem - wrong exception handling in unit initialization/finalization process.
The problem easy to reproduce - just make any program error/exception (division by zero for instance) in initialization block of any unit. The exception will be created correctly. But then, before the exception rise, the unit finalization process destroy the exception object. And thus, when the exception object accessed, the "runtime error 216" occured.
I'd suspect a memory leak (all Runtime Errors 216 I've encountered so far were) and use a profiler (visual inspection is never as good as a tool). Since you're using Delphi XE, you should give AQTime a try (it's included), see also
Delphi - Check if memory is being released "on time"
Kind regards, Frank
Since runtime error 216 is an access violation, this may indicate that you're attempting to use something that you've already freed.
Addresses in the map file are based at 0, but that's not where your EXE file gets loaded into memory. Your EXE gets loaded at its preferred base address, which is usually $400000. Subtract that from the address you have. The address you're looking for in the map file is $0000054a.
There was a similar question, Read:
How to debug a crash that only occurs on application shutdown? (Delphi)
Consider using Memory profiler, this may help identifying live objects after app was terminitated.
I suggest you try the FastMM Full Debug Mode, and either statically link that into your app, or use it as a package (if your app uses packages).
You can use the method I used to fix mine.
I commented out the main program, and added code back until it failed.
Turns out that it did not want me to call couninitialize at all. Did not throw an error at the time, but failed after program termination with a 216. Removing the offending statement fixed it.
Since this was maybe 6 statements before end. statement, I don't imagine it will matter.
This method is easy if you are consistent about using // for comments. I moved IO statements that needed curly brackets to a procedure.
On Microsoft's oficial web site it is mentioned that, this issue can occur if your computer is infected with a SubSeven Trojan virus.
Antivirus software and windows registry cleaner should help.
I have in beta tests that is getting ANRs on a Pixel, and a Pixel 2 XL both running 8.1. From the logs I am getting back it appears that the call to AAssetManager_open is blocked waiting for a mutex to unlock.
From the log there is not discernible threading conflicts. On the one device it is happen on the third asset read as the app is loading. All of which are separate (and clean up) but sequential. The other device the deadlock is later. No threads are touching related code.
I have yet to encounter this issue on another device so I can't even play with it locally to understand further (I don't have either device). From what Android source I could find the mutex locked doesn't have anything complex about its usage.
The calls are happening on the main thread (hence the ANRs), so I can patch the issue by moving them off there. Ideally, though, I want to fix (or at least understand the cause of) the underlying problem of why the deadlock is happening on these devices in the first place.
So, what I am wondering is if there are any known ways to create a deadlock with AAssetManager_open?
On a side note, the closet I have found is a single article that mentions in passing people getting ANRs on AAssetManager_open in the Oreo pre-release builds but I can't find anything else on that.
Edit: I know have a crash on a different 8.1 device (OnePlus5), so it appears to not be specific to Pixel but 8.1 in general.
I also moved what AssetManager reads were on the main thread just incase and as expected the issue still exists (just don't get an ANR).
Edit #2: It is specific to 8.1 with AdMob mediation.
The reason of deadlock can be invalid pointer to AAssetManager. Please make sure, that pointer which you get from AAssetManager_fromJava is still valid (was not destroyed by GC).
link to AAssetManager_fromJava description
Opening an asset may be a blocking operation. Some assets are stored uncompressed, and AAssetManager_open() can return handle to work with the 'file' in-place. Other assets must be uncompressed to a local cache before they can be used. Some of these files will already be unzipped to your disk, and AAssetManager_open() will return almost instantaneously. Others must be unzipped, and this will compete for CPU with other threads, producing ANR if you are unlucky.
The bottom line, do your best to open assets not from the UI thread.
I have been asked to debug, and improve, a complex multithreaded app, written by someone I don't have access to, that uses concurrent queues (both GCD and NSOperationQueue). I don't have access to a plan of the multithreaded architecture, that's to say a high-level design document of what is supposed to happen when. I need to create such a plan in order to understand how the app works and what it's doing.
When running the code and debugging, I can see in Xcode's Debug Navigator the various threads that are running. Is there a way of identifying where in the source-code a particular thread was spawned? And is there a way of determining to which NSOperationQueue an NSOperation belongs?
For example, I can see in the Debug Navigator (or by using LLDB's "thread backtrace" command) a thread's stacktrace, but the 'earliest' user code I can view is the overridden (NSOperation*) start method - stepping back earlier in the stack than that just shows the assembly instructions for the framework that invokes that method (e.g. __block_global_6, _dispatch_call_block_and_release and so on).
I've investigated and sought various debugging methods but without success. The nearest I got was the idea of method swizzling, but I don't think that's going to work for, say, queued NSOperation threads. Forgive my vagueness please: I'm aware that having looked as hard as I have, I'm probably asking the wrong question, and probably therefore haven't formed the question quite clearly in my own mind, but I'm asking the community for help!
Thanks
The best I can think of is to put breakpoints on dispatch_async, -[NSOperation init], -[NSOperationQueue addOperation:] and so on. You could configure those breakpoints to log their stacktrace, possibly some other info (like the block's address for dispatch_async, or the address of the queue and operation for addOperation:), and then continue running. You could then look though the logs when you're curious where a particular block came from and see what was invoked and from where. (It would still take some detective work.)
You could also accomplish something similar with dtrace if the breakpoints method is too slow.
Usually an access violation terminates the program and I cannot catch a Win32 exception using try and catch. Is there a way I can keep my program running, even in case of an access violation? Preferably I would like to handle the exception and show to the user an access violation occurred.
EDIT: I want my program to be really robust, even against programming errors. The thing I really want to avoid is a program termination even at the cost of some corrupted state.
In Windows, this is called Structured Exception Handling (SEH). For details, see here:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms680657%28v=vs.85%29.aspx
In effect, you can register to get a callback when an exception happens. You can't do this to every exception for obvious reasons.
Using SEH, you can detect a lot of exceptions, access violations included, but not all (e.g. double stack fault). Even with the exceptions that are detectable, there is no way to ensure 100% stability after the exception. However, it may be enough to inform the user, log the error, send a message back to the server, and gracefully exit.
I will start by saying that your question contains a contradiction:
EDIT: I want my program to be really robust, ... The thing I really want to avoid is a program termination even at the cost of some corrupted state.
A program that keeps on limpin' in case of corrupted state isn't robust, it's a liability.
Second, an opinion of sorts. Regarding:
EDIT: I want my program to be really robust, even against programming errors. ...
When, by programming errors you mean all bugs, then this is impossible.
If by programming errors you mean: "programmer misused some API and I want error messages instead of a crash, then write all code with double checks built in: For example, always check all pointers for NULL before usage, even if "they cannot be NULL if the programmer didn't make a mistake", etc. (Oh, you might also consider not using C++ ;-)
But IMHO, some amount of program-crashing-no-matter-what bugs will have to be accepted in any C++ application. (Unless it's trivial or you test the hell out of it for military or medical use (even then ...).)
Others already mentioned SEH -- it's a "simple" matter of __try / __catch.
Maybe instead of trying to catch bugs inside the program, you could try to become friends with Windows Error Reporting (WER) -- I never pulled this, but as far as I understand, you can completely customize it via the OutOfProcessException... callback functions.
Edit : If you're seeing this same problem (and you're accustomed to NOT seeing this under VS2010) please comment below so I know it's not just me - but be sure to check Han's answer to make sure none of those scenarios appear...
I've been updating my app to run with .NET 4.5 in VS2012 RTM and noticing something that I don't quite understand and that is unexpectedly green highlighted statements (instead of yellow).
Now I'm well aware of what this is supposed to mean, and the IDE is even showing me a little explanation tooltip.
This is the next statement to execute when this thread returns from
the current function
However there's absolutely nothing asynchronous or thread based about this code. In this simple example I'm sure you'll agree that string.ToUpper() won't be off in another thread. I can step through the code no issue.
There's nothing else going on and I am on the main thread as you can see here.
I am using async and await and MVVM-Light (the above method is the result of a RelayCommand) but I still get this behavior even when the code path is directly off an event handler such as PreviewKeyDown.
If I create a new app I cannot duplicate this - the coloring is yellow as expected - even when using await.
Anybody got any idea? It's starting to drive me crazy!!
It is green when the current instruction pointer is not exactly at the start of the statement. Some common causes:
Common in threaded code, setting a breakpoint in one thread and switching context to another. The other thread will have been interrupted by the debugger at an entirely random location. Often in code that you don't have source code or debugging info for, like String.ToUpper(), the debugger can only show the "closest" source code
Using Debugger + Break All to break into the debugger. Same idea as above, the instruction pointer will be at a random address
Getting an exception in code you don't have debugging info for. The editor shows the last entry in the Call Stack that it does have source code for. You need the call stack window to see where the actual exception was raised. Or the Exception Assistant, its reason for being
Debugging optimized code. The jitter optimizer scrambles the code pretty heavily, making it likely that the debugger can't show the current location accurately
Having out-dated debugging info or editing the code while debugging
Debugging code generated by the x64 jitter, happens when the project's Target Platform setting is AnyCPU. The x64 jitter has a number of chronic bugs that are not getting fixed, generating incorrect debugging info is one of them. Problems that were not addressed until it was completely rewritten, done by the RyuJIT project and first available in .NET version 4.6. Targeting x86 in your EXE project is the workaround.
I understand that this is old post yet I would like to answer the question with my experience.
I have encountered same issue recently in one of my WCF application. After debugging and closely looking service logs and I find out that my code was giving this error because service was hitting max allowed limit for code execution and once the service hit max allowed time limit it was trying to offload the current debugging session.
ERROR IN GREEN STATEMENT: this is the next statement to execute when thread return
So avoiding this issue you can try to look any potential code(Code/Service Timeout or any other code block) which is trying to offload your currently executing code context and try to fix it, furthermore original explanation given by #Hans is still very much relevant for trouble shooting this issue.
Actually, I am also facing this issue. This is because I missed some layout component in landscape mode, So check all the Id's and components and Run, you will not get this error.