Blogs

I just broken my .htaccess file for about an hour and this resulting in /blog/ 301 redirecting to / which wasn’t intended… Fixed now.

I’ve been using the MiniDumpWriteDump() API from DbgHelp.dll for 20 years or so. It has proven to be a useful diagnostic tool, and I use it in all manner of places, including many where others may simply use an assert(). It’s a heavy-weight debugging tool, but it has proved useful over the years; rather than just throwing an exception because things that shouldn’t happen have happened, I often also generate a dump file so that I can get far more data than you could ever log or report in another way.

Back in 2004 I wrote this, I wonder why I used to make some people unhappy… I’m starting to believe that, at 37, I must now be old and cranky because to be quite honest with you; if you’re not writing code in such a way that you define concepts and abstractions in such a way that the actual main line business logic code that you write is clear and easy to understand then you’re just not doing it right.

The only difference between a client and a server is the way in which the connection is established. For a client, you create a socket and call “connect” on it. For a server, we have a socket that is “listening” for connections, “accepts” new incoming connections and returns a socket that is then indistinguishable from a client connection. In the past, I’ve created bad abstractions at this point. A socket connection and a listening socket are both represented by the operating system API as the same type, and the only differences are the calls that you make on the type.

Now that I have a reasonably easy to use event-driven socket class I can start to use it. The first thing to build is a simple client. This will connect to a server and expect that server to echo anything that is sent to it. The client will send data and read it back and compare it with what it sent. A simple, single-threaded, client Last time, I put together a tcp_socket object that made it easier to work with the \Device\Afd interface that I’ve been playing with.

I’ve been investigating the ‘sparsely documented’ \Device\Afd interface that lies below the Winsock2 layer. Today I use a test-driven method for building some code to make using this API a little easier. Using the API In my previous posts on the \Device\Afd interface I focused on exploring and understanding the API itself. Since it’s ‘sparsely documented’ I used unit tests to explore and record my findings. This has left me with some code that is easy to come back to and pick up, which is lucky since it’s been quite a while since I last had some time to tinker with it.

Back in 2009 I started playing around with embedded assembly language on simple hardware with the intention of building a robot spider. This was hosted on a separate website, L’Hexapod.com It was a lot of fun but once my children came along the project took up too much time for me to focus on it. Back in 2010 I thought that the birth of my first son, Scott, would be just a small blip in my journey into robotics but, looking back, it seems to have been the end of that chapter.

I had an internet outage this morning. This shouldn’t have been much of a problem for me as all of the code that I needed to be working on is on my local git server and all of the dependencies are local. Or so I thought. The client has a c# shim layer that builds as part of the C++ server build. They rely on NuGet to grab some components from somewhere for some reason.

When your machine has multiple NUMA nodes it’s often useful to restrict a process to using just one for performance reasons. It’s sometimes hard to fully utilize multiple NUMA nodes and, if you get it wrong, it can cost in performance as the nodes need to keep their caches consistent and potentially access memory over a slower link than the memory that is closer to the node, these things can be relatively expensive.

I’ve always found testing multi-threaded code in C++ a humbling experience. It’s just so easy to make stupid mistakes and for those mistakes to lurk in code until the circumstances are just right for them to show themselves. This weekend a unit test that has run thousands of times for many years started to fail. The reason for the failure was a fairly obvious race condition in the test code. This issue had lain dormant and only been exposed by running the tests on my new development machine.