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Re: .NET 4.0 : First-chance exception 0x04242420 RRS feed

  • Question

  • Hi, All

    I've thread the previous discussions on the .NET 4.0 : First-chance exception 0x04242420.  At one point it is stated that it "It should be entirely safe to ignore."  It even has a label:  CLRDBG_NOTIFICATION_EXCEPTION_CODE.

    My question is why is it displayed if it's OK to ignore?  The other question is what does it mean and how can I change my code so that it does not occur?

    Thanks 

    - Neil Shore


    Friday, July 13, 2012 5:24 PM

Answers

  • Hi Neil,

    I think I can help shed some light on this issue for you...

    >>1. Documented or undocumented, my primary issue is how to avoid having this exception occur.  It is annoying to have a first chance exception occur when it "can be safely ignored".

    I agree that having a debugger spew first chance exceptions at you is irritating. I didn't catch it above but let me know if you see it more than once per-process? No promises, but I can ask the VS debugger guys if it is possible to get this exception filtered out based on the exact exception code in the future.

    2. I have not been able to find which debug exception to turn off in the "Break When An Exception Occurs" dialog.  Does it exist?

    While there isn't a specific entry for this exception code in Visual Studio's list, you could turn the dialog off for all Win32 exceptions by using Debug->Exceptions... and then unchecking 'Win32 Exceptions' in the Thrown column of check boxes. If you have both managed and native code debugging enabled I expect that also suppresses seeing the exception.

    3. I'd gladly change my code to avoid it if I knew what to change.

    This exception is triggered during the startup path of the .Net 4.0 runtime so your options would be limited to using an earlier version of the runtime, not using managed code at all, or suppressing the dialog in the debugger.

    4. Aside from the above, as an intellectual  exercise, I'd like to know what the exception implies is going on.

    This particular exception doesn't mean an error has occurred, it means the CLR is trying to send the debugger a message. The most likely case is that the exception you see corresponds to the runtime startup event, a message that indicates the CLR is initialized enough that an enlightened debugger can start interacting with it. If VS has managed debugging enabled it will understand that message and signal the debuggee to continue producing these messages in the future. Of course an enlightened debugger won't display them as raw exceptions, it will decode their meaning and instead make updates internally such as 'New App Domain loaded' or 'Reflection Emit just created a new type in memory.' Alternatively if the debugger is not enlightened about managed code it won't recognize anything special about this exception and makes no special response. Without a response CLR assumes the debugger is not enlightened for managed code and shouldn't send any further messages (exceptions).

    HTH,

     -Noah

    • Marked as answer by ShoreLaserMan Monday, August 6, 2012 11:58 AM
    Thursday, August 2, 2012 4:43 AM
    Moderator

All replies

  • Hi Neil,

    Welcome to the MSDN Forum.

    Do you mean this thread: http://social.msdn.microsoft.com/Forums/eu/clr/thread/bca092d4-d2b5-49ef-8bbc-cbce2c67aa89 ?

    >>At one point it is stated that it "It should be entirely safe to ignore."

    I think this is very specific, you cannot treat all this exceptions by ignoring them. If you mean above thread, the explanation is mentioned in Ed Dore's reply. If not, please tell us what is your "previous discussions".

    >> The other question is what does it mean and how can I change my code so that it does not occur?

    What is your code?

    Thank you.

    Best regards,


    Mike Feng
    MSDN Community Support | Feedback to us
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Monday, July 16, 2012 8:21 AM
    Moderator
  • Hi Mike,<o:p></o:p>

    Thanks for your reply.<o:p></o:p>

    Yes, We are referring to the same post.  In the post Ed Dore explains where the exception comes from, its name, and that it is safe to ignore.  However, he does not explain why it occurs.  I ask this question because I did not always see this exception.  It started after one of my iterations of my software.  So, I'm wondering if there is something that my code is now doing that I should change.<o:p></o:p>

    My code consists of a managed DLL written in C++ with an interface so that it can be called by unmanaged code.  The managed DLL processes XML data files (which is much easier to do with managed code then with unmanaged code).  The unmanaged code is a software system that is an application integrated with hardware and software algorithms to visually inspect objects.  The unmanged code uses DLLs that interface with:  1) cameras via the cameras manufacturer API, hardware, 2) digital I/O via the manufacturers APIs, and 3) analog I/O via the manufacturers APIs.  The unmanaged code also uses a number of open source libraries to perform mathematical analysis.<o:p></o:p>

    The application is returning Detected memory leaks!  I'm trying to find the cause and wondering if the fact that I'm getting the First-chance exception 0x04242420 is an indication of something.<o:p></o:p>

    Thanks.<o:p></o:p>

    Best Regards,<o:p></o:p>

    - Neil Shore

    Monday, July 16, 2012 2:47 PM
  • Hi Neil,

    About why it is occurred, this is another very specific question. Did you get the stack trace? 

    Here is a blog about what is the first chance exception: http://blogs.msdn.com/b/davidklinems/archive/2005/07/12/438061.aspx 

    I think if we need to know why it occurred, we need to know what is it, so this blog should be helpful, please take a look at it.

    And a dump file should be helpful to you to find the cause: http://blogs.msdn.com/b/kaushal/archive/2012/05/09/using-debugdiag-to-capture-a-dump-on-first-chance-exception.aspx 

    Best regards,


    Mike Feng
    MSDN Community Support | Feedback to us
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Tuesday, July 17, 2012 3:01 AM
    Moderator
  • Hi Neil,

    Do you have any update?

    Is above suggestions helpful?

    Best regards,


    Mike Feng
    MSDN Community Support | Feedback to us
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Monday, July 23, 2012 2:44 AM
    Moderator
  • Why it occus - It is just like any other .NET exception. But, Framework knows about that exception and handles the exception itself. If the Framework doesn't expect any error, it just throws it back to you. Also note that even though framework handles that exception, your output window will still tell you that there was an exception. Since, framework itself handles that exception, it is safe to ignore that error.

    Regarding your memory leak issue, I don't think that first chance exception has anything to do with.

    I hope this helps.


    Please mark this post as answer if it solved your problem. Happy Programming!

    Monday, July 23, 2012 5:51 AM
  • Mike,

    I'm still working on getting a dump file.  Once I do I'll report anything I find.

    Thanks.

    Best Regards,

    Monday, July 23, 2012 3:47 PM
  • Hi Adavesh,

    I'm not sure what you mean by "It is just like any other .NET exception".  Unlike other exceptions I've encountered in my .NET coding career , I don't understand the CLRDBG_NOTIFICATION_EXCEPTION_CODE exception.  All I've been told or have read is that it is OK to ignore it.  If it is OK to ignore, why make it an exception.  If its indicating some activity that has taken place or needs to take place, tell me what the activity is or what causes this kind of exception.  This is what I'm asking.

    Regards,

    - Neil Shore

    Monday, July 23, 2012 3:55 PM
  • Mike,

    I'm still working on getting a dump file.  Once I do I'll report anything I find.

    Thanks.

    Best Regards,

    Hi Shore,

    OK, you are welcome.

    Good luck.

    Best regards,


    Mike Feng
    MSDN Community Support | Feedback to us
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Tuesday, July 24, 2012 1:21 AM
    Moderator
  • "It is just like any other .NET exception" means - Since CLR is a software, exception can occur in CLR too, right? But, Microsoft is aware of that exception and they are handling the exception in CLR itself.

     If it is OK to ignore, why make it an exception.

    Let me answer this question through a sample,

    class Employee{}
    class Department{}
    ..
    ArrayList list = new ArrayList();
    list.Add (new Employee());
    list.Add(new Department());
    
    ..
    
    Employee emp = null;
    foreach(var item in list)
    {
       try
       {
          emp = (Employee)item;
       }
       catch{}
    
       if(emp != null)   
       {
           //Do something
       }
    }

    In the above code, I am interested in Employee objects in ArrayList. Since, there are other type of objects also in ArrayList, I want to ignore them. While traversing through ArrayList, if the type of object is other than Employee, then it throws an exception. But, I know that an exception would be thrown when the object is not an Employee and hence, I am ignoring that exception. (I know that there are ways improve the above without having to throw the exception but I am just using that example for demo purpose).

    Now, if you run the above code, though you are handling the exception, it will show you a 'first chance exception' message in output window. But you know that it is a known exception which is ignored.

    So, similar thing hanppens in CLR also. CLR expects an error, which is handled by CLR iteslf and for that perticular exception it has given a error number CLRDBG_NOTIFICATION_EXCEPTION_CODE = 0x04242420.

    I hope it makes sense.


    Please mark this post as answer if it solved your problem. Happy Programming!

    Tuesday, July 24, 2012 5:11 AM
  • Hi Adavesh,

    Thanks you for your explanation.  It makes sense and I believe I understand your explanation.  However, It still begs the question.  That is , in your example the reason for the exception is known, you designed the software that way.  As a matter of fact one might want to add code to the catch so that if an exception that is not expected (an exception not related to the type cast of item to employee) is thrown, it is reported out.  My software did not cause the  CLRDBG_NOTIFICATION_EXCEPTION_CODE initially.  It now does cause the exception.  I don't have a way of going back to the source before the exception was caused.  So, if I knew the reason, i.e., what the root cause of the exception is then I might be able to better understand my code.

    Regards

    - Neil Shore


    Wednesday, July 25, 2012 12:32 PM
  • Hi Neil,

    >>So, if I knew the reason, i.e., what the root cause of the exception is then I might be able to better understand my code.

    When an application is being debugged, the debugger gets notified whenever an exception is encountered  At this point, the application is suspended and the debugger decides how to handle the exception. The first pass through this mechanism is called a "first chance" exception. Depending on the debugger's configuration, it will either resume the application and pass the exception on or it will leave the application suspended and enter debug mode. If the application handles the exception, it continues to run normally.

    To find the exception lines, you need to check every try-catch block, your application throw an exception, but it didn't suspended, this means your application has handled it. So I think there should be something similar to Adavesh's example code.

    Best regards,


    Mike Feng
    MSDN Community Support | Feedback to us
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Friday, July 27, 2012 9:29 AM
    Moderator
  • Hi Mike and Adavesh,

    Maybe I'm not making my question clear or I just don't get it.  I know about "first chance" exceptions and how the debugger handles them.  I know about try - catch blocks.

    When there is an exception thrown, there is a cause.  I.e., for example CArchiveExceptionCFileException, or CUserException.  These are exception classes that have known reasons, and underlying reasons, for the exception being thrown. E.g. a CFileException can be thrown for a File not found, or attempt to write to a read only file.

    So what I'm trying to ask is what is (or are) the reason(s) for the  CLRDBG_NOTIFICATION_EXCEPTION_CODE.  Is it an exception thrown just to let you know that CLR has recognized its being debugged?  Is it and exception to let the debugger know that CLR code is being run in a mixed CLR - native application?

    Does this make my question more clear?

    Best Regards,

    - Neil Shore

    Friday, July 27, 2012 11:17 AM
  • Hi Neil,

    As you said, when we got the details exceptions, we can try to figure out what the reason is. 

    In addition, where do you got the label CLRDBG_NOTIFICATION_EXCEPTION_CODE?

    Best regards,


    Mike Feng
    MSDN Community Support | Feedback to us
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Monday, July 30, 2012 2:20 AM
    Moderator
  • Hi Mike,

    Check out the thread:   http://social.msdn.microsoft.com/Forums/eu/clr/thread/bca092d4-d2b5-49ef-8bbc-cbce2c67aa89.

    Also if you search MSDN for 0x04242420‎  you get about 25 hits.  Its this number that lead me to CLRDBG_NOTIFICATION_EXCEPTION_CODE.

    Best Regards,

    - Neil Shore

    Tuesday, July 31, 2012 1:13 PM
  • Hi Neil,

    According to Ed, you are looking for something which is undocumented, so I am not sure you can get positive responses.

    Best regards,


    Mike Feng
    MSDN Community Support | Feedback to us
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Wednesday, August 1, 2012 3:43 AM
    Moderator
  • Hi Mike,

    Your response implies that I should stop pursuing this issue.  I'll make four points and then we can end this thread.

    1. Documented or undocumented, my primary issue is how to avoid having this exception occur.  It is annoying to have a first chance exception occur when it "can be safely ignored".

    2. I have not been able to find which debug exception to turn off in the "Break When An Exception Occurs" dialog.  Does it exist?

    3. I'd gladly change my code to avoid it if I knew what to change.

    4. Aside from the above, as an intellectual  exercise, I'd like to know what the exception implies is going on.

    Best Regards,

    - Neil Shore

    Wednesday, August 1, 2012 12:09 PM
  • Hi Neil,

    About the second: http://msdn.microsoft.com/en-us/library/d14azbfh.aspx 

    The debugger can break execution of your application immediately when an exception occurs, giving you a chance to debug the exception before a handler is invoked.

    If you are debugging with How to: Step Into Just My Code enabled, the behavior is slightly different. With Just My Code enabled, the debugger ignores first-chance common language runtime (CLR) exceptions that are thrown outside of My Code and do not pass through My Code. If the exception is completely unhandled, however, the debugger always breaks.

    Best regards,


    Mike Feng
    MSDN Community Support | Feedback to us
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Thursday, August 2, 2012 3:21 AM
    Moderator
  • Hi Neil,

    I think I can help shed some light on this issue for you...

    >>1. Documented or undocumented, my primary issue is how to avoid having this exception occur.  It is annoying to have a first chance exception occur when it "can be safely ignored".

    I agree that having a debugger spew first chance exceptions at you is irritating. I didn't catch it above but let me know if you see it more than once per-process? No promises, but I can ask the VS debugger guys if it is possible to get this exception filtered out based on the exact exception code in the future.

    2. I have not been able to find which debug exception to turn off in the "Break When An Exception Occurs" dialog.  Does it exist?

    While there isn't a specific entry for this exception code in Visual Studio's list, you could turn the dialog off for all Win32 exceptions by using Debug->Exceptions... and then unchecking 'Win32 Exceptions' in the Thrown column of check boxes. If you have both managed and native code debugging enabled I expect that also suppresses seeing the exception.

    3. I'd gladly change my code to avoid it if I knew what to change.

    This exception is triggered during the startup path of the .Net 4.0 runtime so your options would be limited to using an earlier version of the runtime, not using managed code at all, or suppressing the dialog in the debugger.

    4. Aside from the above, as an intellectual  exercise, I'd like to know what the exception implies is going on.

    This particular exception doesn't mean an error has occurred, it means the CLR is trying to send the debugger a message. The most likely case is that the exception you see corresponds to the runtime startup event, a message that indicates the CLR is initialized enough that an enlightened debugger can start interacting with it. If VS has managed debugging enabled it will understand that message and signal the debuggee to continue producing these messages in the future. Of course an enlightened debugger won't display them as raw exceptions, it will decode their meaning and instead make updates internally such as 'New App Domain loaded' or 'Reflection Emit just created a new type in memory.' Alternatively if the debugger is not enlightened about managed code it won't recognize anything special about this exception and makes no special response. Without a response CLR assumes the debugger is not enlightened for managed code and shouldn't send any further messages (exceptions).

    HTH,

     -Noah

    • Marked as answer by ShoreLaserMan Monday, August 6, 2012 11:58 AM
    Thursday, August 2, 2012 4:43 AM
    Moderator
  • Hi Noah,

    Thank you for your answer!  It was very helpful!

    I didn't catch it above but let me know if you see it more than once per-process? 

    No, It only occurs once, when starting a debug session.

    This exception is triggered during the startup path of the .Net 4.0

    It is relieving to know that this is a .Net 4.0 issue.  I was wondering why my code which used to run with no first chance exception now has one.  The code I'm working with has been around for a while and has migrated from pre-.NET (i.e. only native as there was not other) to .Net 4.0.

    Thanks again for your answer.

    - Neil Shore

    Monday, August 6, 2012 12:07 PM