IIS6 StackOverFlow

Sometimes you need to run code with extensive use of stack due to recursive algorithms. But recursion (if very deep) can be very harmful for stack. I encountered such situation, in a particular use of iTextSharp. In my case, IIS 6 (w3wp.exe) crashed with an unknow exception that seemed to be thrown from kernel32.

I spent many hours trying to understand where the problem was. Using WinDbg and AdPlus I understood that the problem came from Net managed code, and after dumping the stack, it was clear which was the method(s).

First: it's not a library bug. If I reduce the work-load (number of input pdf files) it works perfectly. Second: the same piece of code, with the same input pdf files, runs perfectly from a command-line application. So, the problem is related to the IIS "environment".

Solution: increase the stack! Ok, but how ? Simple: running the code inside a thread with a bigger stack!
On IIS6 the "default" threads are created with 256 KB of stack. I haven't found a way to change it. But, from your asp.net code you can create and run a new thread with a bigger stack.

Example code (direct run):

protected void Button1_Click(object sender, EventArgs e)
{
this.Run();
}

private void Run()
{
//... code with or calling library with high use of stack
}


Passing trought a "working" thread (with 1 MB of stack):

protected void Button1_Click(object sender, EventArgs e)
{
this.RunAsSeparatedThread();
}

private void RunAsSeparatedThread()
{
Thread t = new Thread(Run, 1 * 1024 * 1024);
t.IsBackground = true;
t.Start();
t.Join();
}

private void Run()
{
//... code with or calling library with high use of stack
}