cargo-asm hangs in projects with at least one dependency

[MarceColl]

Hi!

I was just testing your tool and I am having some problems with all projects that have dependencies.
On several projects cargo-asm just hangs and nothing happens.

I tried running it with --debug-mode and the output is the following in every single project:

[DEBUG][cargo_asm][/home/<USER>/.cargo/registry/src/github.com-1ecc6299db9ec823/cargo-asm-0.1.16/src/main.rs:75]: Options: RwLock { data: Asm(AsmOptions { path: None, TRIPLE: None, no_color: false, asm_style: Intel, build_type: Release, features: [], rust: true, comments: false, directives: false, json: false, debug_mode: true, manifest_path: None, debug_info: false, lib: false, no_default_features: false }) }
[DEBUG][cargo_asm::build][/home/mcoll/.cargo/registry/src/github.com-1ecc6299db9ec823/cargo-asm-0.1.16/src/build.rs:29]: Building project...
[DEBUG][cargo_asm::build][/home/mcoll/.cargo/registry/src/github.com-1ecc6299db9ec823/cargo-asm-0.1.16/src/build.rs:37]: RUSTFLAGS=
[DEBUG][cargo_asm::build][/home/mcoll/.cargo/registry/src/github.com-1ecc6299db9ec823/cargo-asm-0.1.16/src/build.rs:106]: starting cargo build... "cargo" "build" "--color=always" "--release" "--verbose"

It seems that happens as soon as I add a dependency to a new project.

Steps to reproduce:

1. Create a new project with cargo new --bin test_asm
2. Run cargo-asm --debug-mode, it runs fine
3. Add a dependency (e.g. rand = "0.6.1" to Cargo.toml)
4. Run cargo-asm --debug-mode, it hangs

Alternatively I've created a repo with the minimum example that hangs for me (essentially the result of doing the above): https://github.com/MarceColl/debug_cargo_asm

Environment

Rust toolchain:
nightly-x86_64-unknown-linux-gnu (default)
rustc 1.32.0-nightly (14997d56a 2018-12-05)
cargo-asm 0.1.16

OS
Linux 4.17.19-1-MANJARO #1 SMP PREEMPT Fri Aug 24 17:46:14 UTC 2018 x86_64 GNU/Linux
Up-to-date as of the above date

If you need any more information I'll be happy to provide it.

[MarceColl]

Update: It looks that it's just that cargo is building at that point but there is no output from it, so when I add the dependency it stays in that line until it has recompiled everything. This is a bit of a slow machine so it was taking a long time building the rand crate and its dependencies.

[gnzlbg]

It looks that it's just that cargo is building at that point but there is no output from it, so when I add the dependency it stays in that line until it has recompiled everything.

Yes, so cargo asm needs to dump the assembly for all your dependencies while building, that can take a while the first time it builds everything.

I don't know what to do about this. AFAIK there is nothing we can do to speed things up here, beyond making rustc faster.

[MarceColl]

Hmmm... I don't think there is that much to do. It was just confusing to me.
Maybe just adding a "This may take a while if it's the first time you run it" when running cargo asm? Honestly not sure if other people were confused the first time, maybe it was just me.

[gnzlbg]

I was confused too, as in, I sometimes do not know if the project is still building, or if something went wrong. Maybe I could spin up a thread that writes:

...project has been building for 30 seconds...
...project has been building for 60 seconds...

similarly to how cargo test does it if a test runs for too long.

[MarceColl]

Yeah, that seems like a good and fairly easy way to reduce confusion with long builds