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Comment by winstonewert | Hacker News Reader

Many rust crates actually do package code written in other languages. There are plenty of useful C/C++/Fortran libraries that nobody has rewritten into Rust but for which wrappers have been created that call into C. It works in Rust because the build.rs lets libraries do whatever they want during the build process, including invoking compilers for other languages.

Various factors still make the Rust and Python story different (Python uses more mixed-language packages, the Rust demographic is more technically advanced, etc). But a big one is that in Rust, the FFI is defined in Rust. Recompiling just the Rust code gives you an updated FFI compatible with your version of Rust. In Python, the FFI is typically defined in C, so recompiling the python won't get you a compatible FFI. If Python did all FFI through something like ctypes, it would be much more smooth.

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> It works in Rust because the build.rs lets libraries do whatever they want during the build process, including invoking compilers for other languages.

It's still its own mess. You'll find plenty of people having problems with openssl, for instance.

I have the pleasure of maintaining a reasonably popular -sys crate, and getting it working on Windows is an absolute nightmare, especially considering the competing toolchains & ABIs (msvc and gnu) and millions of ways the C dependency can be installed (it’s a big one, and users may choose a specific version, so we don’t bundle it), with no pkg-config telling you where to look.

No idea how build.rs being able to run any Rust code is an advantage, it’s not like setup.py can’t run any Python code and shell out. In fact, bespoke code capable of spitting out inscrutable errors during `setup.py install` is the old way that newer tooling tries to avoid. Rust evangelism is puzzling.

Wait a second, I need to understand this better.

If you cargo build, can that run a dependencies' build including trying to compile C and stuff?

Yes, see https://doc.rust-lang.org/cargo/reference/build-scripts.html.

I believe build.rs can do pretty much anything: https://doc.rust-lang.org/cargo/reference/build-scripts.html

That's both scary and sad :-(

Why? If you are using a crate, its code will be running in your application. Its not really any more of a concern if it can run code while building.

Yeah, but with binary packages you can add another lay of defense in depth, signed packages, signature checking, etc. It's not just about the original authors themselves, it can also be about attacks on the public repositories, for example.

When I referred to build.rs - I merely meant that the build script made it possible to build code written in other languages - not that it solved all the problems. It very much doesn't solve all the problems involved.

Though you get partially saved by the "FFI is defined in Rust" part, with many of the hard to compile crates offering optional prebuilt binaries for the part that's not rust.

> It works in Rust because the build.rs lets libraries do whatever they want during the build process, including invoking compilers for other languages.

And also there's a helper library (the "gcc" crate) which does all the work of figuring out how to call the C or C++ compiler for the target platform, so that build.rs can be very small for simple cases. You don't have to do all the work yourself.

Don't you mean the `cc` crate? `gcc` is its terribly-outdated predecessor.

It's the same crate, it just changed its name at some point in its history. I still refer to it through its former name by force of habit.

I know it's the same crate, but they changed its name. `gcc` is the predecessor of `cc` in terms of name. If you depend on `gcc` instead of `cc`, you won't have any of the new improvements.

gcc is not terribly outdated overall, this is FUD. specific information, please

The `gcc` crate was last published to in 2018. Use `cc`.

https://docs.rs/crate/gcc/latest/builds

That sounds like cffi https://cffi.readthedocs.io/en/latest/

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