15 posts tagged with "c#"

A few years ago I worked on reproducing the Kaleidoscope tutorial using LLVMSharp, a library that exposes C# bindings for LLVM. I updated multiple times the project to support the latest versions of llvm and the LLVMSharp bindings. In the last week I was busy moving to llvm 18 and I encountered a few difficulties.

First, the newest version of LLVMSharp available on nuget is 16.0.0, however the corresponding repo is updated to support version 18.0.0 of llvm. Luckily for me, there is a nighly nuget feed where a release candidate of LLVMSharp supporting version 18.0.0 is available. Please note that at the time of writing the latest llvm version is 19, LLVMSharp is updated inconsistently and it has been since the beginning for what I could see.

Now, once I decided to go with llvm 18 and found the right source for the package, the next big issue was the removal of the PassManagerBuilder.h starting from version 17.0.0 as detailed in the release notes. There is a documentation on how to use the new pass manager here using C++ but LLVMSharp is exposing the C api of llvm. There is a point were C apis are mentioned in the new docs

The C API also supports most of this, see llvm-c/Transforms/PassBuilder.h.

Given that:

1. I'm not an expert on llvm
2. I'm not an expert on C nor C++

It wasn't obvious to me how to use the new pass manager. I did quite some research on internet and on github trying to find samples and how-tos, with little luck tbh.

One source that I think is good quality but overall too complex for me was the source code for the C3 language, they are using the C api of llvm and indeed using the new PassBuilder. However while the compiler is written in C using the C apis of llvm, the bit about the pass manager has a C++ wrapper. So I'm out of luck on this.

Finally, I found a working approach in the place were I should have looked first (but didn't!), the llvm project itself. They have unit tests for the new PassManager, with that it was easy to get something working.

The approach that I'm following now with llvm 18 is not exactly the same as the one with llvm 16, because before I had a function pass manager and I was applying the passes on each single function, now I'm applying the passes to the whole module. I don't know what's the status now (at version 19.0.x of llvm) and I don't know if it was already possible to keep the old approach but I wasn't able to do it. For my scopes, it is enough what I have now.

The passes need to be passed as a comma separated string to the LLVMRunPasses function, here the list of the current available passes. The code using llvm 16 was having both analysis passes and transform passes for no other reason that I was mimicking what was done in the original Kaleidoscope tutorial.

The LLVMRunPasses didn't accept the only analysis pass I had basic-aa but accepted all the transforms. This is somehow understandable as the pass manager comes from llvm-c/Transforms/PassBuilder.h. I guess for analysis passes there is another infrastructure.

Now my kaleidoscope repo is updated and functional, still able to run the mandelbrot example.

I updated my TreeSitter.Bindings packages to support additional languages. I wanted to check how solid the bindings were and if I could implement a more complex sample with the respect to the json one I started with.

The tree-sitter documentation provides a multilanguage sample which involves three languages:

• embedded template
• ruby
• html

I want to leverage my visitor pattern source generator to implement a simple minimal api.

I aim to:

• Have a request and a request handler for my endpoint. I will not use mediatr or any similar library and I will not use any real storage, only some in memory data structure to showcase the visitor pattern approach.
• The request handler Handle method returns an interface, every subtype represents a different type of result, a success, and one type for each error (provided) emitted by the handled.
• For each subtype we want to be able to return a possibly different http response.

In a previous experiment I made I used the LLVMSharp library and I was quite curious on how the bindings are made. In the readme is it stated they are generated using che ClangSharp library, this one auto-generate hitself from the headers of Clang C header.

This functionality is exposed through a dotnet tool: ClangSharpPInvokeGenerator. So I wanted to try and hack my way into parsing the tree-sitter headers and use the generated code to run a very small sample using C#, in particular I was aiming for the one that's in the getting started section of the docs

I am a big fan of the visitor pattern, I think it is a very good approach for adding behaviors to a group of classes without modifying all of them.

For example if we are building a compiler we may have an abstract syntax tree that represents the code that the compiler is compiling. Two different visitors can be, for example:

• a type checker
• a code emitter

In this post we will see how to use EF6 (not EF Core) in a .NET Core application with SQLite. Why we would like to do this? Maybe we are migrating a project from the full framework to .NET Core but we are not ready to migrate also EF6 to EF Core. I will not show how to work with migrations.

First of all, we need to install two packages in our project:

• System.Data.SQLite.EF6
• System.Data.SQLite

In a previous post I talked about ROP in C#, now I want to explore how to use it in a ASP.NET Core web api project. If you haven't I suggest to take a look at my previous posts since I won't go into the details of union types and my custom Result<T> type:

1. A tagged union example
2. Railway oriented programming with C#

LLVM Kaleidoscope .NET​

If you're reading and learning about compilers in these days you will at some point find something about LLVM. I did and I tried to implement the Kaleidoscope tutorial from the official documentation using C#. I won't write a full blown tutorial and in the end I didn't actually follow the official tutorial as it was pretty hard for me to read C++ code.

Workflows​

As a software developer I work, most of the times, on LOB applications that support some kind of process or workflow for a specific company. That means that there are some entities, such as customers, orders or support tickets, and that they evolve during the lifecycle of the application. For example we could have a CRM with a lead entity that evolves into a customer or we could track the state of a ticket: open -> analysis -> work -> deploy.

polynomials-pratt-algorithm​

Using a Pratt parser I aim to parse expressions like this x^2+y^2-1, x=1, y=1 and xy, x=2, y=3. Parsing mathematical expressions it's not hard but it already contains some interesting behaviour such as associativity between operators x+y*z is equal to x+(y*z) and not (x+y)*z. For no particular reason I decided to put the variable assignments after the polynomial. The expression x^2+y^2-1, x=1, y=1 is to be interpreted as you would with this pseudo code