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55 points anqurvanillapy | 2 comments | | HN request time: 0.627s | source

Hi I'm Anqur, a senior software engineer with different backgrounds where development in C was often an important part of my work. E.g.

1) Game: A Chinese/Vietnam game with C/C++ for making server/client, Lua for scripting [1]. 2) Embedded systems: Switch/router with network stack all written in C [2]. 3) (Networked) file system: Ceph FS client, which is a kernel module. [3]

(I left some unnecessary details in links, but are true projects I used to work on.)

Recently, there's a hot topic about Rust and C in kernel and a message [4] just draws my attention, where it talks about the "Rust" experiment in kernel development:

> I'd like to understand what the goal of this Rust "experiment" is: If we want to fix existing issues with memory safety we need to do that for existing code and find ways to retrofit it.

So for many years, I keep thinking about having a new C dialect for retrofitting the problems, but of C itself.

Sometimes big systems and software (e.g. OS, browsers, databases) could be made entirely in different languages like C++, Rust, D, Zig, etc. But typically, like I slightly mentioned above, making a good filesystem client requires one to write kernel modules (i.e. to provide a VFS implementation. I do know FUSE, but I believe it's better if one could use VFS directly), it's not always feasible to switch languages.

And I still love C, for its unique "bare-bone" experience:

1) Just talk to the platform, almost all the platforms speak C. Nothing like Rust's PAL (platform-agnostic layer) is needed. 2) Just talk to other languages, C is the lingua franca (except Go needs no libc by default). Not to mention if I want WebAssembly to talk to Rust, `extern "C"` is need in Rust code. 3) Just a libc, widely available, write my own data structures carefully. Since usually one is writing some critical components of a bigger system in C, it's just okay there are not many choices of existing libraries to use. 4) I don't need an over-generalized generics functionality, use of generics is quite limited.

So unlike a few `unsafe` in a safe Rust, I want something like a few "safe" in an ambient "unsafe" C dialect. But I'm not saying "unsafe" is good or bad, I'm saying that "don't talk about unsafe vs safe", it's C itself, you wouldn't say anything is "safe" or "unsafe" in C.

Actually I'm also an expert on implementing advanced type systems, some of my works include:

1) A row-polymorphic JavaScript dialect [5]. 2) A tiny theorem prover with Lean 4 syntax in less than 1K LOC [6]. 3) A Rust dialect with reuse analysis [7].

Language features like generics, compile-time eval, trait/typeclass, bidirectional typechecking are trivial for me, I successfully implemented them above.

For the retrofitted C, these features initially come to my mind:

1) Code generation directly to C, no LLVM IR, no machine code. 2) Module, like C++20 module, to eliminate use of headers. 3) Compile-time eval, type-level computation, like `malloc(int)` is actually a thing. 4) Tactics-like metaprogramming to generate definitions, acting like type-safe macros. 5) Quantitative types [8] to track the use of resources (pointers, FDs). The typechecker tells the user how to insert `free` in all possible positions, don't do anything like RAII. 6) Limited lifetime checking, but some people tells me lifetime is not needed in such a language.

Any further insights? Shall I kickstart such project? Please I need your ideas very much.

[1]: https://vi.wikipedia.org/wiki/V%C3%B5_L%C3%A2m_Truy%E1%BB%81...

[2]: https://e.huawei.com/en/products/optical-access/ma5800

[3]: https://docs.ceph.com/en/reef/cephfs/

[4]: https://lore.kernel.org/rust-for-linux/Z7SwcnUzjZYfuJ4-@infr...

[5]: https://github.com/rowscript/rowscript

[6]: https://github.com/anqurvanillapy/TinyLean

[7]: https://github.com/SchrodingerZhu/reussir-lang

[8]: https://bentnib.org/quantitative-type-theory.html

1. AlotOfReading ◴[] No.43174839[source]
The problem with "safe pockets in ambient unsafety" is that C and C++ intentionally disallow this model. It doesn't matter what you do to enforce safety within the safe block, the definition of Undefined Behavior means that code elsewhere in your program can violate any guarantees you attempt to enforce. The only ways around this are with a language that doesn't transpile to C and doesn't have undefined behavior like Rust, or a compiler that will translate C safely like zig attempts to do. Note that zig still falls short here with unchecked illegal behavior and rustc has struggled with assumptions about C's undefined behavior propagating into LLVM's backend.
replies(1): >>43175020 #
2. jjnoakes ◴[] No.43175020[source]
Safe pockets in ambient unsafety does have benefits though. For example, some code has a higher likelihood of containing undefined behavior (code that manipulates pointers and offsets directly, parsing code, code that deals with complex lifetimes and interconnected graphs, etc), so converting just that code to safe code would have a high ROI.

And once you get to the point where a large chunk of code is in safe pockets, any bugs that smell of undefined behavior only require you to look at the code outside of the safe pockets, which hopefully decreases over time.

There are also studies that show that newly written code tends to have more undefined behavior due to its age, so writing new code in safe pockets has a lot of benefit there too.