To recap, to write suru I had to: Write a parser in a Parser Expression Grammer to parse taskfiles. Generate a build graph listing the dependency roots and their dependents. Execute the build graph in a multithreaded manner. All in all, writing Suru only took 4 days of work, and only a couple hundred of lines of code. I enjoyed how Rust combines bits of C++ and Haskell into a cohesive language that offers the elegance of Haskell and the versatility of C++....
The second part of building Suru is constructing a build graph. A build graph is almost certainly necessary in the context of multithreading because of the presence of diamond dependencies. Constructing a graph in Rust isn’t too bad, but does require a little big of fandangling. Rc, Arc, Refcell, Mutex, RwLock??? I’ve seen some people get confused between the various constructs Rust has surrounding multithreading, but if you have a context in C++ multithreading it’s not very complicated....
The first part of building suru was creating a parser, which was the part with the most false starts. The syntax I had in mind was relatively poorly defined at the time. Unfortunately, this lead to me a parser only to find out that it wouldn’t inherently work. Nom I literally searched up parsers on lib.rs, and the first result I found was nom. Nom is a combinator parsing library intended for parsing binary formats, but also was serviceable for parsing text....
For a long time, I wanted to make a makefile replacement. Writing a good makefile is surprisingly non-trivial if you want certain features. For example, the internal pattern rules of make fail if you want to do an out of tree build, which is most modern builds. Moreover, making sure that make does not fail when a dependent header file is surprisingly obscure. Even to this day, the best makefile template is very much a matter of debate....
After quite the lengthy tread through GCC and C-land (mind you everything discussed before was written in C), we finally find ourselves back at C++. C++ exception semantics seem simple, but actually hide many surprising edge cases. Functions Like before, let’s discuss the API of the C++ exception handling regime. Note that while you’re not supposed to call these functions directly, these functions are called in compiler generated code anyways, so are a part of the public ABI....
Last time I mentioned libunwind, but now I’m going to go over the implementation of libunwind in GCC. As mentioned before, libunwind used to be a library developed by HP, but it got vendored into GCC as a part of libgcc. libgcc itself is a small library containing, besides libunwind, various intrinsics for floating point and integer math. libunwind One might reasonably ask the question of how one can unwind a stack while using functions that modify the stack?...
Last time I talked about the broad architecture of how exceptions work. Today I’m focusing on how debug information is contained in the eh_frame section. To explain why exception information is held in the format it is today, we need to dive a little into the history of libunwind. Much of what is here comes from linux reference documents, found here. History Libunwind was originally developed by HP back in the days of the unix wars....
As it turns out there’s not really a good in depth explanation of how exceptions work. There are disparate explanations of how separate parts of exceptions in C++ work, but not really the whole picture. So I’m writing this down here as a reference to how everything in C++ exceptions work. Disclaimer My experiences are exclusively in GCC. Broadly, Clang should follow the same Architecture as GCC, but may vary in implementation details....
Quite a while ago, I’ve integrated my exceptions work into a fork of GCC. At that point, I was already modifying GCC to suppress the libunwind symbols, so putting all of my code into GCC was a no brainer. Moreover, it isn’t actually that hard to build GCC. Editing GCC GCC is built via the autoconf build system. Autoconf is a collection of scripts that is somewhat like CMake, but written entirely in shell script and is intended to be portable for any system that runs shell scripts and has a C compiler....
As is tradition, I’ve hosted the blog manually using AWS. Last time I created configured an Apache server manually. However, as I grew more knowledgeable about web development, I realized that this was a woefully out-dated solution. So here’s my retelling of how I created this blog. Hugo To begin with, I began by using Hugo as my static website generator. I’ve had enough experience with it that using it was relatively painless....