Throwing an anonymous exception inside recursive function

Question

After the couple of seconds, the following program outputs

Process is terminated due to StackOverflowException

instead of my message. Why?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Numerics;

namespace maximumVariable
{
    class Program
    {

        public static BigInteger Factorial(int num)
        {
            try
            {
                return (num > 1) ? num*Factorial(num - 1) : (1);
            }
            catch
            {
                throw;
            }
        }


        static void Main(string[] args)
        {
            BigInteger kingKong=0;
            int facParameter=0;
            try
            {

                while (true)
                {
                    kingKong = Factorial(facParameter);
                    facParameter++;
                }

            }
            catch
            {
                Console.WriteLine("The maximum value " + kingKong.ToString()+"has been achieved after "+facParameter.ToString()+" iterations");
            }


        }
    }
}

Side note: What's the point of catching and re-throwing in `Factorial`? (Ignoring the fact that you can't catch StackOverflowException) — Brian Rasmussen, Jul 27 '12 at 20:15
possible duplicate of [C# catch a stack overflow exception](http://stackoverflow.com/questions/1599219/c-sharp-catch-a-stack-overflow-exception) — Brian Rasmussen, Jul 27 '12 at 20:16
@BrianRasmussen This source code should be self-explanatory; I wanted to check the maximum factorial that BigInteger can contain. — 0x6B6F77616C74, Jul 27 '12 at 20:23
The point is that catching an exception only to immediately re-throw it is redundant. If you're not doing anything with the exception, don't catch it. — Brian Rasmussen, Jul 27 '12 at 20:27

score 2 · Accepted Answer · edited May 23 '17 at 11:45

2

You can only catch a StackOverflowException under very specific circumstances. Thus, your custom error message is never displayed.

See here: C# catch a stack overflow exception
See also: http://msdn.microsoft.com/en-us/library/system.stackoverflowexception.aspx

It makes sense; a stack overflow represents a state that is difficult to proceed from (compared to most other exception types).

edited May 23 '17 at 11:45

Community

1
1

answered Jul 27 '12 at 20:13

Tim M.

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score 1 · Answer 2 · edited Jul 27 '12 at 20:17

From MSDN:

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.

So you can no longer catch that exception.

Throwing an anonymous exception inside recursive function

2 Answers2