C# catch a stack overflow exception

Question

I have a recursive call to a method that throws a stack overflow exception. The first call is surrounded by a try catch block but the exception is not caught.

Does

Answer 1

As several users have already said, you can't catch the exception. However, if you're struggling to find out where it's happening, you may want to configure visual studio to break when it's thrown.

To do that, you need to open Exception Settings from the 'Debug' menu. In older versions of Visual Studio, this is at 'Debug' - 'Exceptions'; in newer versions, it's at 'Debug' - 'Windows' - 'Exception Settings'.

Once you have the settings open, expand 'Common Language Runtime Exceptions', expand 'System', scroll down and check 'System.StackOverflowException'. Then you can look at the call stack and look for the repeating pattern of calls. That should give you an idea of where to look to fix the code that's causing the stack overflow.

Answer 2

Starting with 2.0 a StackOverflow Exception can only be caught in the following circumstances.

1. The CLR is being run in a hosted environment^* where the host specifically allows for StackOverflow exceptions to be handled
2. The stackoverflow exception is thrown by user code and not due to an actual stack overflow situation (Reference)

_{^*"hosted environment" as in "my code hosts CLR and I configure CLR's options" and not "my code runs on shared hosting"}

Answer 3

The right way is to fix the overflow, but....

You can give yourself a bigger stack:-

using System.Threading;
Thread T = new Thread(threadDelegate, stackSizeInBytes);
T.Start();

You can use System.Diagnostics.StackTrace FrameCount property to count the frames you've used and throw your own exception when a frame limit is reached.

Or, you can calculate the size of the stack remaining and throw your own exception when it falls below a threshold:-

class Program
{
    static int n;
    static int topOfStack;
    const int stackSize = 1000000; // Default?

    // The func is 76 bytes, but we need space to unwind the exception.
    const int spaceRequired = 18*1024; 

    unsafe static void Main(string[] args)
    {
        int var;
        topOfStack = (int)&var;

        n=0;
        recurse();
    }

    unsafe static void recurse()
    {
        int remaining;
        remaining = stackSize - (topOfStack - (int)&remaining);
        if (remaining < spaceRequired)
            throw new Exception("Cheese");
        n++;
        recurse();
    }
}

Just catch the Cheese. ;)

Answer 4

Yes from CLR 2.0 stack overflow is considered a non-recoverable situation. So the runtime still shut down the process.

For details please see the documentation http://msdn.microsoft.com/en-us/library/system.stackoverflowexception.aspx

Answer 5

You can't. The CLR won't let you. A stack overflow is a fatal error and can't be recovered from.

Answer 6

From the MSDN page on StackOverflowExceptions:

In prior versions of the .NET Framework, your application could catch a StackOverflowException object (for example, to recover from unbounded recursion). However, that practice is currently discouraged because significant additional code is required to reliably catch a stack overflow exception and continue program execution.

Starting with the .NET Framework version 2.0, a StackOverflowException object cannot be caught by a try-catch block and the corresponding process is terminated by default. Consequently, users are advised to write their code to detect and prevent a stack overflow. For example, if your application depends on recursion, use a counter or a state condition to terminate the recursive loop. Note that an application that hosts the common language runtime (CLR) can specify that the CLR unload the application domain where the stack overflow exception occurs and let the corresponding process continue. For more information, see ICLRPolicyManager Interface and Hosting the Common Language Runtime.