Comment by progval

6 years ago

Interesting comment on Reddit: https://www.reddit.com/r/rust/comments/dtqm36/how_swift_achi...

> You can actually already do dynamic linking in Rust, but only with C-based interfaces. The C-like interfaces that gankra talks about are I belive more similar to current Rust than to C, so I think they shouldn't be called C-like. They could support structs, enums, trait objects, lifetimes, slices, etc. "Stable ABI Rust" would be a name that's more fair. Addition of generator based async and generics of course won't work, but not all interfaces actually need those features.

> I think there is definitely potential for a "better dynamic linking" RFC that adds a stable ABI to the language. Of course, the default compilation mode should keep using unstable ABIs, generics, async, etc. But allowing crate writers to opt into a stable ABI would be beneficial for precompiled crates as well as compile times which are still the biggest problem with the Rust compiler for many people.

(a crate is a Rust package)

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progval

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zozbot234  6 years ago

>But allowing crate writers to opt into a stable ABI would be beneficial for precompiled crates as well as compile times

I think there is already a fuzzy convention that could basically be made to enable this. A crate name ending in -sys is expected to provide a C-like interface, and to thus be usable in a dylib context, whereas the same crate name with no suffix or with a -rs one provides a statically-linked, ABI-unstable wrapper to its corresponding -sys. The build system just needs to be made aware that the former kind of crate need not be recompiled when potential ABI-breaks are introduced.

> (a crate is a Rust package)

A crate is a Rust compilation unit. Closer to a .cxx, .o file in C/C++ than what are usually called "packages" there.

  • epage  6 years ago

    -sys are raw wrappers around C code so wouldn't provide much benefit for them to be exposed as dynlibs.

    And crates are the equivelant of python, node, go, etc packages. That they are also a compilation unit is, I believe, an implementation detail. I think they also made it configurable.

    • steveklabnik  6 years ago

      A crate is a compilation unit. A package is defined by a Cargo.toml, and can have one or more crates.

      Most folks use “package” and “crate” interchangeably, even if they’re technically different.

      See the bottom of https://doc.rust-lang.org/book/ch07-00-managing-growing-proj...

      (Additionally, “compilation unit” is a bit weird, given incremental compilation, etc. “the file containing the root module tree that gets passed to rustc” is not as succinct though.)

    • gpm  6 years ago

      We can split one crate into multiple units for better paralleization, but I don't think there is a way to put multiple into a single compilation unit.