Specifying jobs = 0 in .cargo/config hangs cargo forever without output

[orlp]

If you specify jobs = 0 in .cargo/config, your cargo build invocations will hang forever without output. Note that if you try to invoke cargo build -j 0 it will warn you:

$ cargo build -j 0
error: jobs must be at least 1

Steps

1. Place a .cargo/config in any valid location with the following content:

    [build]
    jobs = 0
   

2. Run cargo build.

3. You will never reach step 3.

Possible Solution(s)

Check for jobs being 0 when reading the config file.

Notes

Output of cargo version: latest master commit, 0b2059e.

[henrifrancois]

Does the issue still persist? If so I would like to give it a try

[Eh2406]

I believe it is still an issue. And nobody's working on it that I know of. Have at it.

…

On Wed, Jun 9, 2021, 10:22 PM Henri E. Francois ***@***.***> wrote: Does the issue still persist? If so I would like to give it a try — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub <#9219 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA4JUQD35TQDXWT27HMTFITTSAOXHANCNFSM4YMX2ZQQ> .

[henrifrancois]

@rustbot claim

[henrifrancois]

Hey, @Eh2406 could you help me out with this? I have something I think should work, but I am not sure why it isn't making a difference at all.

In build_context.rs I have:

impl BuildConfig {
    /// Parses all config files to learn about build configuration. Currently
    /// configured options are:
    ///
    /// * `build.jobs`
    /// * `build.target`
    /// * `target.$target.ar`
    /// * `target.$target.linker`
    /// * `target.$target.libfoo.metadata`
    pub fn new(
        config: &Config,
        jobs: Option<u32>,
        requested_targets: &[String],
        mode: CompileMode,
    ) -> CargoResult<BuildConfig> {
        let cfg = config.build_config()?;
        let requested_kinds = CompileKind::from_requested_targets(config, requested_targets)?;
        if jobs == Some(0) {
            anyhow::bail!("jobs must be at least 1")
        }
        if jobs.is_some() && config.jobserver_from_env().is_some() {
            config.shell().warn(
                "a `-j` argument was passed to Cargo but Cargo is \
                 also configured with an external jobserver in \
                 its environment, ignoring the `-j` parameter",
            )?;
        }
        let jobs = match jobs.or(cfg.jobs) {
            None => ::num_cpus::get() as u32,
            Some(j) if j != 0 => (::num_cpus::get() as u32).max(j),
            Some(_) => anyhow::bail!("jobs may not be 0"),
        }; //.unwrap_or(::num_cpus::get() as u32);

which I assumed would be enough to handle the case where the jobs argument has a value of 0. Any pointers?

[Eh2406]

That is what I would have expected to work. And when I am careful to run the Cargo I just build and not the cargo from rustup, it worked for me!

[henrifrancois]

Oop, nevermind. I think I got it working.