arocc VS nomicon

Possible reference as it requires to use the compiler as part of language abi: https://github.com/Vexu/arocc/issues/178 Not sure, where a better thread with explanations of the flaws is.

Zig calls clang to compile C code. This doesn't add a new dependency since Zig already depends on LLVM. In the future when Zig doesn't depend as much on LLVM, there might be a reason to use a C compiler written in Zig (e.g. https://github.com/Vexu/arocc)

Bit field rules are underspecified or plain wrongly implemented, because in their edge cases clang and GCC differ in semantics. See https://github.com/Vexu/arocc/issues/178 This should be further restricted with static asserts as compiler semantics even changed with versions and doing this manually/doing code review is error prone.

You might want to contribute or look into https://github.com/Vexu/arocc, which is planned to be eventually an alternative frontend. Is arocc able to handle your use cases?

> Does this mean that y'all are open to the self-hosted compiler supporting CPU architectures unlikely to ever have LLVM support?

Yes! We won't block 1.0 on the quality of the less mainstream targets, but that's what the tier system is for - to ship a compiler that has varying levels of quality for various targets, while communicating clearly to users what kind of experience they can expect for each one.

SuperH patches are absolutely welcome.

> how is zig cc anticipated to work with a self-hosted Zig? Will there be a dependency on clang [...]?

The main distribution of Zig will be LLVM/Clang-enabled. However it is already possible to build a version of Zig that does not have these features enabled. In such case, compiling C, C++, and Objective-C code will result in an error.

However, the arocc project[1] is emerging, which, depending on a combination of how much funding ZSF gets and how much enthusiasm the unpaid contributors working in their spare time have, is looking like a promising C frontend that would be available even without LLVM/Clang. It is C only, however, with no intention of compiling C++ or Objective-C.

> would zig cc support the planned C backend?

As it is currently implemented: no. Zig invokes clang to turn C source code into object files.

However, with the arocc frontend above, this would be converting the C source code into ZIR (or perhaps AIR), which could then be lowered with any of the backends, including the (partially complete) C backend. In such case, the C output would look drastically different than the input. It would look more like an IR than natural C code that a human would write.

[1]: https://github.com/Vexu/arocc

Implementing only the language part takes like 10k LOC.

> 9. Without a C compiler, we're stuck with, wedded to, and beholden to libclang.

> I wouldn't be surprised that the eventual cost of adapting ourselves to

> libclang will exceed the cost of doing our own C compiler.

This is a really insightful point. I had to learn this the hard way :)

We might follow your lead on this, as we have done with so many other great ideas implemented in D.

Ironically, Vexu started from the other side as you, with the preprocessor mostly done, but the backend left to-do: https://github.com/Vexu/arocc

One thing that might make libclang worth the cost, however, is its ability to compile C++ code as well. On Zig's end of things, all we have to do is provide libcxx, libcxxabi, libunwind, compiler-rt, and linking, and then libclang is really pulling a lot of weight by compiling C++ code into object files. Sadly this ability is just too useful in practice to ignore. For example, LLVM itself is C++ so if Zig wants to be able to bootstrap itself, it needs this capability.

Still, I think your maneuver here is the best long-term approach to tackle this problem, and I imagine as time goes on we'll start to migrate towards D's solution here. Maybe someday the Zig distribution that does not have LLVM extensions enabled will be the more popular one!

I'll be watching the evolution of this new feature in D with great interest!

it’s even written by the same person that wrote the Nomicon (the guide to the dark arts of unsafe)

If you want to dive deeper you can always have other options but now there are concrete cases, if you want to do low level thing https://doc.rust-lang.org/nomicon/ while if you want multi thread/concurrency stuff https://marabos.nl/atomics/ . There are many many books so you will have to point yourself to what you want

Nonononono. SeqCst is the most error prone memory order: https://github.com/rust-lang/nomicon/issues/166

Hope this helps. For more details, see the Rustonomicon. I referenced the subtyping chapter here extensively.

Nice video! Glad I could help out. This stuff is hard, and I'm still learning a lot about it myself even years later. The Rustonomicon is a great read if you haven't already.

Have you got a moment to read through the good book , after reading through this perhaps try the Rustonomicon.

That is not what UB means. Undefined Behaviour is behaviour that the compiler is allowed to assume will never happen, and which can consequently cause miscompilations due to optimisation passes gone wrong if it does in fact occur in the source code.

It's true that Rust does not have a written specification that clearly delineates what is and isn't UB in a single place. But:

1. UB is impossible in safe code (modulo bugs in unsafe code)

2. There are resources such as the Rustinomicon (https://doc.rust-lang.org/nomicon/) that provide a detailed guide on what is and isn't allowed in unsafe code.

In practice, it's much easier to avoid UB in Rust than it is in C++.

However, this is a wide topic out of scope for a Reddit comment, so maybe just read the Rustonomicon. It explains everything about data handling in Rust.

The ownership model & borrow checker makes rust a bit of an awkward language in which to write complex data structures like trees and graphs. It can be done - since you can always use raw pointers & unsafe code when you absolutely need to to treat rust like C. But the language fights you, and the community can get a bit moralistic about this sort of thing. The rust nomicon is a fantastic resource for learning the limits of the borrow checker, and where and how to use unsafe code correctly. You will need unsafe less than you think you will, but sometimes you will have no choice.