Code Generation in Rust vs C++26 (brevzin.github.io)

submitted 2 months ago by snaggen@programming.dev to c/rust@programming.dev

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This is a blog post that really is about C++, but with a look at how Rust does things. So, this is an interesting C++/Rust comparison for once.

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[-] BB_C@programming.dev 1 points 2 months ago

In Rust, you provide a string — that is injected to be invoked internally. In C++, we’d just provide a callable.

This is because Rust’s attribute grammar can’t support a callable here.

I don't do C++ as a life choice, and thus not 100% sure what the author means here. But I have the feeling that he is wrong, on multiple levels even 😉

[-] TehPers@beehaw.org 2 points 2 months ago* (last edited 2 months ago)

Correct - Rust's attribute grammar allows any parseable sequence of tokens enclosed in #[attr ...] basically. Serde specifically requires things to be in strings, but this is not a requirement of modern Rust or modern versions of syn (if you're comfortable writing your own parser for the meta).

The author is not a Rust expert though, so I'm not surprised to see this assumption. It doesn't take away from the article though.

Edit: for fun, syn has an example parsing an attribute in an attribute

[-] BB_C@programming.dev 2 points 2 months ago* (last edited 2 months ago)

Not only that. We don't just "inject" raw strings with the syn/quote duality. Stringified or not, the token tree will be parse-checked into the expected syn type before being used in generated code.

So the distinction is both wrong and irrelevant. This is what I meant by wrong on multiple levels/layers 😉

this post was submitted on 01 Oct 2024

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