I am using a fingerprint capture device in my c# application, this device has c# wrapper class for a c++ SDK dll.
Sometimes i get a c++ exception message (see image) and then the application close, the problem is that I can't catch this exception and can't keep application running after this exception.
The Question is: How Can I Catch This Exception in C#?
How Can I Catch This Exception in C#?
You cannot. An unmanaged C++ exception cannot be caught by managed code. You need to catch unmanaged exceptions in unmanaged code. You cannot let unmanaged exceptions propagate outside the unmanaged module.
However, the error dialog suggests that you have a more serious problem. One that cannot be dealt with simply by catching an exception. You will need to work out why your program is terminating the runtime in this catastrophic way, and stop that happening. That error dialog suggests that your program is calling abort(), which is terminal.
In other words you need to prevent this error from happening in the first place, rather than attempting to recover from it. This is not an error that you can hope to recover from.
Related
Currently, there is no way (at least I did not find a way) to catch fatal exceptions (such as Stack Overflow, Segfault, ..) with try-catch block.
I already started issue at .net core repository so for more details you can read there (https://github.com/dotnet/core/issues/4228)
What I'm trying to do is to make the application not crash when there is any segfault/stack overflow/any fatal exception in loaded unmanaged code. what happens now is that .NET CLR kills my application if any fatal error occurs.
Example:
In c# managed code loaded external c++ dll via kernel LoadLibrary function.
Assume the dll is intentionally created for robustness testing therefore when a specific function is called it triggers segfault (e.g. trying to get data from outside of array bounds).
When this error happens this gets caught by .net CLR and immediately kills the calling managed c# code(application).
What I would like is just report that this happens instead of dying silently.
I did some research and found out there is the reasoning behind that which is described in the issue above.
I'm trying to write some code to wrap a c++ library that throws unmanaged exceptions.
Just for testing purposes, is it possible to generate an unmanaged exception from c# code without having to create a fake c++ library standin?
The C# Programming Guide states that "In C# you cannot throw non-CLS exceptions". This means you can only throw exceptions deriving from the Exception class, i.e. managed exceptions. You'll have to create a c++ library standin.
Incidentally, the same page also explains how to catch such exceptions. However, this only applies when the c++ code in question is actually throwing an exception - if it's an access violation this will be a Corrupted State Exception which cannot be caught, see here for more.
I am trying to resolve a AccessViolationException that is created when returning from native to managed code. Visual studio 2015 / .Net 4.0. I went into the Exception Settings and selected to Break when thrown for AccessViolationException. However that does not appear to occur. I read that there are new behaviors for this exception here.
https://msdn.microsoft.com/en-us/library/system.accessviolationexception(v=vs.110).aspx
Would that prevent the debugger from breaking on the throw?
More details, and maybe you are right the VS simply cannot give me more. The native code returns a struct to the managed code. The struct is defined in managed so that the marshaling can occur. I can step through the native code and the method completes. The debugger ends up on the managed method which was pinvoked. I was hoping the debugger would stop at a point that would allow me to identify the offending memory component
I've got a weird symptom in an application, where try/catches inside the handler for UnhandledExceptions don't work: (that is a breakpoint inside the catch does not get hit, even if the breakpoint inside the try does).
Obviously searching for 'exception unhandled inside UnhandledException' is not working very well for me.
I've tried doing a mini proof-of-concept, and unfortunately that one works.
So while I'm trying to track down the root of the problem, if anyone here has any ideas where to look I'd be greatful.
(We recently changed from XP to Windows7, and .Net 4.5 from 4.0 - I'm pretty certain that previously this worked).
EDIT: Looks like it's provoked by a call down to a (managed) C++ library which is throwing a System.AccessViolationException. Strangely, if I replace the call with a throw new AccessViolationException, it does do what I want...
You wrote, "We recently changed ... .Net 4.5 from 4.0 - I'm pretty certain that previously this worked." but the following seems worth adding, because pretty sure really means not certain :-)
I read somewhere that AccessViolationException cannot occur in managed code, but may be trapped by the runtime for unmanaged code. Maybe the C++ library calls into unmanaged code?
In .NET 4+ the process will terminate after AccessViolationException. Your exception handler will be ignored. This is among a group of exception types considered unrecoverable: Corrupted State Exceptions. In .NET 4+ you will need to customise the app config to override this behaviour.
Be sure that you try to catch System.AccessViolationException and not native Access Violation error.
When you do throw new AccessViolationException it throws System.AccAccessViolationException.
If library that you calls is native it can throw native Access Violation error, but .NET catch block normally can catch only managed exceptions.
try this:
i think we can't handle Unhandeled exception and have to exit application in finally.
http://msdn.microsoft.com/en-us/library/system.appdomain.unhandledexception.aspx
I'm trying to use code similar to clrdump to create mini dumps in my managed process.
This managed process invokes C++/CLI code which invokes some native C++ static lib code, wherein SEH exceptions may be thrown (e.g. the occasional access violation).
C# WinForms
->
C++/CLI DLL
->
Static C++ Lib
->
ACCESS VIOLATION
Our policy is to produce mini dumps for all SEH exceptions (caught & uncaught) and then translate them to C++ exceptions to be handled by application code. This works for purely native processes just fine; but when the application is a C# application - not so much.
The only way I see to produce dumps from SEH exceptions in a C# process is to not catch them - and then, as unhandled exceptions, use the Application.ThreadException handler to create a mini dump. The alternative is to let the CLR translate the SEH exception into a .Net exception and catch it (e.g. System.AccessViolationException) - but that would mean no dump is created, and information is lost (stack trace information in Exception isn't as rich as the mini dump).
So how can I handle SEH exceptions by both creating a minidump and translating the exception into a .Net exception so that my application may try to recover?
Edit
By "not catching exceptions" I also mean catching and then rethrowing, which does preserve the rich exception information.
Right now I'm considering never supressing System.Exception or anything deriving from System.SystemException. This means AccessViolation (and friends) always cause the program to end and produce a dump, and all other exceptions thrown need to derive from some sub-type (ApplicationException?).
I found that with Vectored Exception Handling I can get a first-chance notification of any SEH exception and use this occasion to produce a mini dump.