quote
rust-fsm
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| quote | rust-fsm | |
|---|---|---|
| 3 | 1 | |
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quote
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C++ vs. Rust Build Times
A surprising source of slow compile times can be declarative macros in Rust [0].
I believe the core of the problem is that it has to reparse the code to pattern match for the macro.
One egregious patter is tt-munchers [1] where your macro is implemented recursively, requiring it to reparse the source on each call [2].
In one of my projects, someone decided to wrap a lot of core functions in simple macros (ie nt tt-munchers) to simplify the signatures. Unlike most macros which are used occasionally and have small inputs, this was a lot of input. When I refactored the code, I suspect dropping the macros is the reason CI times were cut in half and a clean `cargo check` went from 3s to 0.5s.
[0]: https://nnethercote.github.io/2022/04/12/how-to-speed-up-the...
[1]: https://veykril.github.io/tlborm/decl-macros/patterns/tt-mun...
[2]: https://github.com/dtolnay/quote/blob/31c3be473d0457e29c4f47...
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Is generating code from JSON a good macro use case?
In the build.rs, call your code generation function (probably in a separate crate added in build-dependencies). This function will read your input files, and use something like quote to generate code.
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Any good resources for learning Rust macros?
Or you can pair them with crates like syn, and quote for quasi-quoting, and then it's easy to make transformations on the AST of Rust input code. A lot of libraries do this for code-generation and hiding away a lot of complexity (example wasm-bindgen).
rust-fsm
What are some alternatives?
cargo-expand - Subcommand to show result of macro expansion
syn - Parser for Rust source code
proc-macro-workshop - Learn to write Rust procedural macros [Rust Latam conference, Montevideo Uruguay, March 2019]
field_names - proc-macro for accessing struct field names at runtime
Bytecode - A Rust proc-macro crate which derives functions to compile and parse back enums and structs to and from a bytecode representation
darling - A Rust proc-macro attribute parser
component-keycloak - Commodore Component for Keycloak
hyper-ts - Type safe middleware architecture for HTTP servers
session-types
hickory - Command line tool for scheduling Python scripts