How to prevent Third Party DLL's StackOverflow Exception from killing Main Application?

Question

We are creating a PDF Preview using PDFToImage DLL of PQScan.We need to create preview image of the first page of PDF.

Whenever I try to get the image, it throws System.StackOverflowException. Which can't be catched in try-catch block and it causes the crash for the application.

try
{
    using (PQScan.PDFToImage.PDFDocument doc = new PQScan.PDFToImage.PDFDocument())
    {
        doc.LoadPDF(UTFPDFPath);
        doc.DPI = 150;
        var temp = doc.PageCount;
    

        using (Bitmap bmp = doc.ToImage(0)) //System.StackOverflowException here
        {
            bmp.Save(BigPrevName, ImageFormat.Gif);
        }
    }
}
catch (Exception ex)
{
}

- $exception {"Exception of type 'System.StackOverflowException' was thrown."} System.StackOverflowException

Unfortunately, StackOverflowException is a nasty one. Maybe you can isolate it in another process ? — Pac0, Jul 01 '21 at 05:59
Does it occur with a specific/any pdf? Is there any documentation of the library that talks about expecting SOException ? — shahkalpesh, Jul 01 '21 at 06:00
We can't do much with the third-party library. Maybe we can check if there is the latest version available which might have fix some issues at their end. I faced similar issues with other third-party libraries and almost wasted a month figuring out the app pool crash in case of session timeout which then resolved by upgrading to the latest version. — Rajan Patekar, Jul 01 '21 at 06:50
The only way to protect your process is to run the suspicious code in a different process. See duplicates. — Peter Duniho, Jul 01 '21 at 08:10

score 3 · Accepted Answer · answered Jul 01 '21 at 08:05

The short answer here is "no"; a stack-overflow scenario cannot be reliably caught / recovered from.

make sure you're on the most recent version available (it might be fixed!)
see whether the documentation lists this as a known issue with possible workaround
if it is a paid product, ask them to fix it as part of your support
if it is open source, consider fixing it yourself and contributing the fix

If none of these are possible, then the fallback would be to write a second executable that just does this processing (using either IPC or file-based means to get data to/from the second process) - then spawn that second process in the knowledge that if it explodes, only the child process has been burned.

This helped. I created another process, transferred the code in that process. And now only child process gets killed. Original remains active. Thanks for the help. — Arpit Gupta, Jul 01 '21 at 12:45

score -1 · Answer 2 · answered Jul 01 '21 at 07:09

-1

As MSDN says using is not designed to catch exceptions because it is actually convenient way to do 'try-finally'. You should change it for something like this:

Bitmap bmp;
try
{
    bmp = doc.ToImage(0);
    bmp.Save(BigPrevName, ImageFormat.Gif);
}
catch (Exception ex)
{
    //process exception
}
finally
{
    if (bmp != null)
      bmp.Dispose();
}

answered Jul 01 '21 at 07:09

doesntcount

19
4

2

the questions clearly shows a `try`/`catch`; the change in this answer will not help - the problem is that stack overflows *cannot be reliably caught* – Marc Gravell Jul 01 '21 at 07:59
Yeah, I missed the that outside `catch` would get the exception if it was possible. Thanks for pointing! – doesntcount Jul 01 '21 at 08:08

How to prevent Third Party DLL's StackOverflow Exception from killing Main Application?

2 Answers2