Question

Below is some logging output from a .NET application.

Error in MainFunction.
Message: Exception of type 'System.OutOfMemoryException' was thrown.
InnerException: 
StackTrace:    at System.Text.StringBuilder.ToString()
   at System.Diagnostics.StackTrace.ToString(TraceFormat traceFormat)
   at System.Environment.GetStackTrace(Exception e, Boolean needFileInfo)
   at System.Exception.GetStackTrace(Boolean needFileInfo)
   at System.Exception.ToString(Boolean needFileLineInfo)
   at System.Exception.ToString()
   [the rest of the trace is removed]

Which corresponds to the following line of application code. The following is in a catch block, and returns the string to the method that actually throws:

private void MainFunction()
{
   ...

   try
   {
      string doc = CreateXMLDocument(); // <- Out of Memory throws here
   }
   catch (Exception ex)
   {
      CoreLogging("Error in MainFunction.", ex);
   }
}

private string CreateXMLDocument()
{
   try
   {
      //Some basic and well constrained XML document creation:
      ...
   }
   catch (Exception ex)
   {
      return "Exception message: " + ex.ToString();  // <- This is the last line of the trace
   }
}

What should I make of this? Clearly Exception.Message should be used instead of Exception.ToString(), but I’d still like to understand this. Does

• at System.Text.StringBuilder.ToString()
• at System.Diagnostics.StackTrace.ToString(TraceFormat traceFormat)

mean that the stack trace of the exception in CreateXMLDocument was so mammoth caused OutOfMemory? I’m curious to see how that would occur as there’s definitely no circular calls in CreateXMLDocument, which is the only thing I can think of that could cause an enormous stack trace.

Has anyone else encountered a similar situation?

Answer 1

I little bit of guessing:

1) CLR rises a OutOfMemoryException. 2) You catch this exception and call .ToString on it
3) ToString() tries to allocate memory to the stack trace but… there is no memory and another OutOfMemoryException is rised.

In the comments you said that the XML documents have a few hundreds of kbytes, this could be a/the problem if your server run on 32bits, because of the fragmentation of the LOH.