Cargo seems to exit prematurely when "cargo run" receives SIGINT

[Svedrin]

If I write code that ignores SIGINT, and then send that code an interrupt by hitting ^c, cargo forwards the signal to the target process but exits prematurely:

[13:22]mz1030@mz1030-nb111:~/tmp/threadtests# cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
     Running `target/debug/threadtests`
^C
[13:22]mz1030@mz1030-nb111:~/tmp/threadtests# Thread exiting!

If I run the target directly, ^c is correctly ignored without me being dropped back to the shell:

[13:23]mz1030@mz1030-nb111:~/tmp/threadtests# ./target/debug/threadtests 
^C^C^C^C^C^CThread exiting!
[13:23]mz1030@mz1030-nb111:~/tmp/threadtests# 

I noticed because I had written an application that takes a second or two to clean up when it receives SIGINT. My Cargo version (installed through rustup) is:

[13:25]mz1030@mz1030-nb111:~/tmp/threadtests# cargo --version
cargo 0.20.0 (a60d185c8 2017-07-13)
[13:25]mz1030@mz1030-nb111:~/tmp/threadtests# rustc --version
rustc 1.19.0 (0ade33941 2017-07-17)

[BurntSushi]

See also:

• Ctrl+C on cargo run #3281
• Ctrl+C on cargo run rustup#806
• [cargo run] Should proxy signals to child process #2343
• cargo run should wait for child termination in case of SIGINT/SIGTERM #2525
• SIGINT can't terminate subprocess on OS X #3460

[alexcrichton]

Thanks for the report! This is, however, how signals work on Unix. When you hit ctrl-c the shell sends SIGINT to the process group. In the case of Cargo nothing's listening for SIGINT so everything is torn down in a nondeterministic fashion.

[Svedrin]

@alexcrichton shouldn't cargo then make the subprocess its own process group before exec()ing the target, so that cargo "just does the right thing"? From a user perspective, this behavior feels very wrong.

[alexcrichton]

The cargo subprocess and all of its children are already in the same process group, so what you're seeing is actually "the right thing" in terms of intention.

The best solution here is handling rust-lang/rustup#806

[Svedrin]

@alexcrichton what does rustup have to do with it? 😕

[alexcrichton]

@Svedrin did you install Rust through rustup? If so when you execute cargo you're actually executing rustup first, then Cargo.