Recently I gave a talk at the NYAN Conference called ‘From ‘dotnet run’ to ‘hello world’: In the talk I demonstrate how you can use PerfView to analyse where the .NET Runtime is spending it’s time during start-up: From 'dotnet run' to 'hello world' from Matt Warren This post is a step-by-step guide ...

Background ‘Default Interface Methods’ (DIM) sometimes referred to as ‘Default Implementations in Interfaces’, appeared in C# 8. In case you’ve never heard of the feature, here’s some links to get you started: Default implementations in interfaces (official announcement) Default Interface Methods (C...

Over the last few years, I’ve come across more and more research papers based, in some way, on the ‘Common Language Runtime’ (CLR). So armed with Google Scholar and ably assisted by Semantic Scholar, I put together the list below. Note: I put the papers into the following categories to make them eas...

As the saying goes: “All problems in computer science can be solved by another level of indirection” - David Wheeler and it certainly seems like the ‘.NET Runtime’ Engineers took this advice to heart! ‘Stubs’, as they’re known in the runtime (sometimes ‘Thunks’), provide a level of indirection throu...

Who doesn’t like a nice bit of ‘ASCII Art’? I know I certainly do! To see what Matt’s CLR was all about you can watch the recording of my talk ‘From ‘dotnet run’ to ‘Hello World!’’ (from about ~24:30 in) So armed with a trusty regex /\*(.*?)\*/|//(.*?)\r?\n|"((\\[^\n]|[^"\n])*)"|@("[^"]*")+, I set o...

I’m a massive fan of everything Fabien Sanglard does, I love his blog and I’ve read both his books cover-to-cover (for more info on his books, check out the recent Hansleminutes podcast). Recently he wrote an excellent post where he deciphered a postcard sized raytracer, un-packing the obfuscated co...

What is ‘stack walking’, well as always the ‘Book of the Runtime’ (BotR) helps us, from the relevant page: The CLR makes heavy use of a technique known as stack walking (or stack crawling). This involves iterating the sequence of call frames for a particular thread, from the most recent (the thread’...

It seems like this time of year anyone with a blog is doing some sort of ‘advent calendar’, i.e. 24 posts leading up to Christmas. For instance there’s a F# one which inspired a C# one (C# copying from F#, that never happens 😉) However, that’s a bit of a problem for me, I struggled to write 24 posts...

A little over 4 years ago Microsoft announced that they were open sourcing large parts of the .NET framework and as this slide from New Features in .NET Core and ASP.NET Core 2.1 shows, the community has been contributing in a significant way: Side-note: This post forms part of an on-going series, i...

Recently I was fortunate enough to chat with Chris Bacon who wrote DotNetAnywhere (an alternative .NET Runtime) and I quipped with him: .. you’re probably one of only a select group(*) of people who’ve written a .NET runtime, that’s pretty cool! * if you exclude people who were paid to work on one, ...

I recently came across the excellent ‘Fuzzlyn’ project, created as part of the ‘Language-Based Security’ course at Aarhus University. As per the project description Fuzzlyn is a: … fuzzer which utilizes Roslyn to generate random C# programs And what is a ‘fuzzer’, from the Wikipedia page for ‘fuzzin...

.NET is a managed runtime, which means that it provides high-level features that ‘manage’ your program for you, from Introduction to the Common Language Runtime (CLR) (written in 2007): The runtime has many features, so it is useful to categorize them as follows: Fundamental features – Features that...

I’m constantly surprised at just how popular resources related to ‘.NET Internals’ are, for instance take this tweet and the thread that followed: If you like learning about '.NET Internals' here's a few talks/presentations I've watched that you might also like. First 'Writing High Performance Code ...

I’ve been digging into .NET Internals for a while now, but never really looked closely at how the ‘Just-in-Time’ (JIT) compiler works. In my mind, the interaction between the .NET Runtime and the JIT has always looked like this: Nice and straight-forward, the CLR asks the JIT to compile some ‘Interm...

Whether you want to look at what your code is doing ‘under-the-hood’ or you’re trying to see what the ‘internals’ of the CLR look like, there is a whole range of tools that can help you out. To give ‘credit where credit is due’, this post is based on a tweet, so thanks to everyone who contributed to...

Firstly, what exactly is CoreRT? From its GitHub repo: .. a .NET Core runtime optimized for AOT (ahead of time compilation) scenarios, with the accompanying .NET native compiler toolchain The rest of this post will look at what that actually means. Contents Existing .NET ‘AOT’ Implementations High-L...

It turns out that the .NET Runtime has a technical standard (or specification), known by its full name ECMA-335 - Common Language Infrastructure (CLI) (not to be confused with ECMA-334 which is the ‘C# Language Specification’). The latest update is the 6th edition from June 2012. The specification o...

I recently appeared on Herding Code and Stackify ‘Developer Things’ podcasts and in both cases, the first question asked was ‘how do you figure out the internals of the .NET runtime’? This post is an attempt to articulate that process, in the hope that it might be useful to others. Here are my sugge...

Discuss this post on HackerNews and /r/programming Before we dive into the technical details, let’s start with a quick history lesson, courtesy of Don Syme who worked on adding generics to .NET and then went on to design and implement F#, which is a pretty impressive set of achievements!! Background...

It all started with a tweet, which seemed to resonate with people: If you like reading my posts on .NET internals, you'll like all these other blogs. So I've put them together in a thread for you!!— Matt Warren (@matthewwarren) January 12, 2018 The aim was to list blogs that specifically cover .NET ...

I’ve now been blogging consistently for over 2 years (~2 times per/month) and I decided it was time for my first ‘retrospective’ post. Warning this post contains a large amount of humble brags, if you’ve come here to read about ‘.NET internals’ you’d better check back in a few weeks, when normal ser...

A little over 3 years ago Microsoft announced that they were open sourcing large parts of the .NET framework and as Scott Hanselman said in his Connect 2016 keynote, the community has been contributing in a significant way: This post forms part of an on-going series, if you want to see how things ha...

The .NET runtime (CLR) has predominantly used a just-in-time (JIT) compiler to convert your executable into machine code (leaving aside ahead-of-time (AOT) scenarios for the time being), as the official Microsoft docs say: At execution time, a just-in-time (JIT) compiler translates the MSIL into nat...

If you grew up in the UK and went to school during the 1980’s or 1990’s there’s a good chance that this picture brings back fond memories: (image courtesy of Classic Acorn) I’d imagine that for a large amount of computer programmers (currently in their 30’s) the BBC Micro was their first experience ...

Recently I was fortunate enough to be invited to the CORESTART 2.0 conference to give a talk on Microsoft & Open Source a ‘Brave New World’. It was a great conference, well organised by Tomáš Herceg and the teams from .NET College and Riganti and I had a great time. I encourage you to attend next ye...

Generics in C# are certainly very useful and I find it amazing that we almost didn’t get them: What would the cost of inaction have been? What would the cost of failure have been? No generics in C# 2.0? No LINQ in C# 3.0? No TPL in C# 4.0? No Async in C# 5.0? No F#? Ultimately, an erasure model of g...

Recently I was listening to the excellent DotNetRocks podcast and they had Steven Sanderson (of Knockout.js fame) talking about ‘WebAssembly and Blazor’. In case you haven’t heard about it, Blazor is an attempt to bring .NET to the browser, using the magic of WebAssembly. If you want more info, Scot...

Just over a year ago Google made all the open source code on GitHub available for querying within BigQuery and as if that wasn’t enough you can run a terabyte of queries each month for free! So in this post I am going to be looking at all the C# source code on GitHub and what we can find out from it...

It’s a fundamental part of .NET and can often happen without you knowing, but how does it actually work? What is the .NET Runtime doing to make boxing possible? Note: this post won’t be discussing how to detect boxing, how it can affect performance or how to remove it (speak to Ben Adams about that!...

Have you ever wondered where and why the .NET Runtime (CLR) allocates memory? I don’t mean the ‘managed’ memory that your code allocates, e.g. via new MyClass(..) and the Garbage Collector (GC) then cleans up. I mean the memory that the CLR itself allocates, all the internal data structures that it ...