1/N One of my favorite optimizations in the upcoming .NET 7 Native AOT is static data preinitialization. This program prints a circle to the screen. Would you believe me if I said there is no code to compute the circle bytes in the NativeAOT'd executable file of this program?👇🧵 2/N Main difference between Native AOT and the other forms of AOT in .NET is that Native AOT doesn't just pregenerate code - it generates all data structures necessary to run the code, including structures that describe layout of types in memory necessary to do things like run GC

1/N I thought it might be interesting to look at how generics are compiled to native code in .NET. A thread. 2/N When generic code is stored in IL on disk (as produced by e.g. the C#/VB/F# compiler), single generic method has a single method body. This method body is only runnable on the abstract CPU that the .NET compilers target. To run it on real hardware, it has to be translated.

1/n It has always bugged me that I can't run my 64-bit C# games on MS-DOS. Today I fixed that. A thread. 2/n Windows EXE files consist of two parts: a DOS program that prints "This program cannot be run in DOS mode", followed by a header that Windows understands.

1/7 Did you ever need to run a piece of C# code on Windows 3.11? Me neither, but I did it anyway. A thread. 2/7 The key ingredient it setting your expectations low. This is the program I got running:

1/5 How about a 2,121 byte version of the C# game? Still 100% self-contained. Here's what I did:

https://twitter.com/MStrehovsky/status/1213034748848807937

2/5 Implement enough x86 Windows support in CoreRT so that we can build the game for it (previous attempt was x64; but the x86 CPU instruction set is more compact): github.com/dotnet/corert/…

1/15 When compiling .NET ahead of time, the hardest question to answer is what code to compile. 2/15 For many non-.NET languages it's enough to compile the closure of Main(): start with Main() and compile all methods called from there transitively.

1/5 "Ugly side of default interface methods" time. Interface with two methods, one with a default implementation. What will the following program print? 2/5 If you guessed 21, you're right, but don't pop the champagne yet. Let's change "class Adder" to "struct Adder" - what will it print now?

1/5 A little know C#/.NET fact is that one can end up in a situation where `this is null` evaluates to true. One just needs a bit of reflection. 2/5 There's good reasons why it's little known. For one, it's kind of useless. The other reason is that doing that starts breaking invariants. For example, C# assumes `this` is always non-null. Call to `this.AndAgain()` should throw, but it won't.