Cargo does not handle +toolchain directives.

[guest271314]

Problem

The documentation https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#script says:

script
Tracking Issue: #12207
Cargo can directly run .rs files as:

$ cargo +nightly -Zscript file.rs

where file.rs can be as simple as:

fn main() {}

Steps

I just fetched the rust-nightly-x86_64-unknown-linux-gnu.tar.xz archive, extracted the cargo folder to the same directory where I have rustc and rust-std-x86_64-unknown-linux-gnu folders extracted from the same archive.

I have this for testing

script.rs

use std::env;
// https://stackoverflow.com/a/75981598
fn main() {
  let args: Vec<String> = env::args().collect();
  if args.len() > 1 {
      println!("Hello {}!", &args[1]);
  } else {
      println!("Hello world!");
  }
}

This is result

$ cargo/bin/cargo +nightly -Zscript ~/bin/script.rs
error: no such command: `+nightly`

	Cargo does not handle `+toolchain` directives.
	Did you mean to invoke `cargo` through `rustup` instead?

Possible Solution(s)

No idea. This is only my second time trying to use Rust.

Notes

It's basically impossible to download the entire Rust toolchain on a temporary file system running a live Linux session.

So I fetched the Nightly archive, immediately got rid of the 600+ MB documentation folder, and everything else except rustc and rust-std-x86_64-unknown-linux-gnu folders.

I'll re-fetch the nightly archive and extract cargo folder.
Eventually I got this to run, using -L to I guess link to rustlib/x86_64-unknown-linux-gnu/lib

#!/bin/sh
//bin/bash -ec '[ "$0" -nt "${0%.*}" ] && /home/user/bin/rustc/bin/rustc -L /home/user/bin/rust-std-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib "$0" -o "${0%.*}"; "${0%.*}" "$@"' "$0" "$@"; exit $?

use std::env;
// https://stackoverflow.com/a/75981598
fn main() {
  let args: Vec<String> = env::args().collect();
  if args.len() > 1 {
      println!("Hello {}!", &args[1]);
  } else {
      println!("Hello world!");
  }
}

What I'm really working on doing is using Rust .rs file as a Native Messaging host script.

I converted a working C version to Rust using https://c2rust.com/.

Now I have to figure out how to link to libc in the resulting file https://gist.github.com/rust-play/92af6fefec0ea8bcc76a5b18be40005e

//https://stackoverflow.com/q/41322300
//https://c2rust.com/
//https://github.com/rust-lang/rust/issues/1772
#![allow(dead_code, mutable_transmutes, non_camel_case_types, non_snake_case, non_upper_case_globals, unused_assignments, unused_mut)]
#![register_tool(c2rust)]
#![feature(register_tool)]
extern "C" {
    static mut stdin: *mut _IO_FILE;
    static mut stdout: *mut _IO_FILE;
    fn fflush(__stream: *mut FILE) -> libc::c_int;
// ...

Just to see what would happen if I was trying to compile the C to Rust code

./rust.sh "test"
error[E0433]: failed to resolve: use of undeclared crate or module `libc`
  --> ./rust.sh:10:39

// ...

118 |         free(message as *mut libc::c_void);
    |                              ^^^^ use of undeclared crate or module `libc`

error: aborting due to 58 previous errors

For more information about this error, try `rustc --explain E0433`.

This is my second time trying to use Rust to build something. My first time using Rust as a script. Thanks.

Version

cargo 1.82.0-nightly (fa6465836 2024-08-02)
release: 1.82.0-nightly
commit-hash: fa646583675d7c140482bd906145c71b7fb4fc2b
commit-date: 2024-08-02
host: x86_64-unknown-linux-gnu
libgit2: 1.8.1 (sys:0.19.0 vendored)
libcurl: 8.9.0-DEV (sys:0.4.74+curl-8.9.0 vendored ssl:OpenSSL/3.3.1)
ssl: OpenSSL 3.3.1 4 Jun 2024
os: Ubuntu 22.4.0 (jammy) [64-bit]

[weihanglo]

This is expected, and as I said, you need to run cargo -Zscript without +nightly. See https://doc.rust-lang.org/nightly/cargo/commands/cargo.html#common-options.

If Cargo has been installed with rustup, and the first argument to cargo begins with +, it will be interpreted as a rustup toolchain name (such as +stable or +nightly). See the rustup documentation for more information about how toolchain overrides work.

[guest271314]

$ cargo/bin/cargo -Zscript ~/bin/script.rs
warning: `package.edition` is unspecified, defaulting to `2021`
error: could not execute process `rustc -vV` (never executed)

Caused by:
  Permission denied (os error 13)

[guest271314]

It looks like cargo depends on rustc. However I have not installed rustc. I just have the rustc, cargo, and rust-std-x86_64-unknown-linux-gnu folders in a local directory. No rustup.

[weihanglo]

Yes. You have to install the rust toolchain correctly via rustup or some other installation method listed here: https://rust-lang.github.io/rustup/installation/index.html. Standalone installation method can be found here: https://forge.rust-lang.org/infra/other-installation-methods.html.

The toolchain installation is out of scope of Cargo and I have limited time to support such kind of tickets. https://users.rust-lang.org/ is one place for user support.

Close since this is not a bug in Cargo. Thank you.