cargo run -v should show setting of LD_LIBRARY_PATH

[joshtriplett]

I spoke with someone recently who had some trouble figuring out how to run Cargo-built binaries directly, until they realized that cargo run sets LD_LIBRARY_PATH, which is not documented. When running cargo run -v, cargo shows the binaries it runs, but not the setting of LD_LIBRARY_PATH. Please include that in the emitted command line invocations (e.g. LD_LIBRARY_PATH=... target/release/...) when using -v, to make it more obvious what cargo run does.

[ehuss]

LD_LIBRARY_PATH behavior is now documented at https://doc.rust-lang.org/cargo/reference/environment-variables.html#dynamic-library-paths.

cargo run -vv will show all environment variables, including LD_LIBRARY_PATH.

I think it would be good to leave this open for a more programmatic way to get the appropriate paths (some kind of JSON output or something).

[sfackler]

cargo run -vv only appears to print full command lines for calls to rustc, but the actual run command is still just Running 'target/debug/foo'. Did this regress?

[ehuss]

Oh, I don't think it ever showed the env vars for the actual running of the executable. I think I was just meaning that the calls to rustc will show it. They are slightly different (between running the exe and building it), so it would probably be good to display it somehow.

[Kobzol]

This makes it difficult to debug Rust binaries that use native dependencies and that require LD_LIBRARY_PATH to be set. Without cargo run, the libraries are not found, and I don't know to which directory in target should I point the environment variable. And trying to debug cargo run with gdb doesn't seem to work for me, the program is constantly being stopped on some SIGUSR1 signal (it can be ignored, but still).

It would be nice if cargo run -vv actually emitted the environment flags. I'd like to try to implement it, if you consider it to be useful (and maybe suggest some mentoring tips :) ).

[weihanglo]

I believe that is feasible to be done.

Basically, search for "Running" string and check if it is really config.extra_verbose(), then set ProcessBuilder::display_env_vars() for the command builder around.

Guess not only cargo run -vv needs that, cargo test -vv could have the same mechanism as well.

---

@rustbot label +E-easy +S-accepted +Command-test +A-console-output

[epage]

I know this might sound weird but would that be too noisy even for -vv? I'd want to see what it looked like first before committing to it.

[weihanglo]

Something like below. Note that we already display all environments set for rustc invocation with -vv.

   Compiling verbose-run v0.1.0 (/projects/verbose-run)
     Running `CARGO=/projects/cargo/target/debug/cargo CARGO_BIN_NAME=verbose-run CARGO_CRATE_NAME=verbose-run CARGO_MANIFEST_DIR=/projects/verbose-run CARGO_PKG_AUTHORS='' CARGO_PKG_DESCRIPTION='' CARGO_PKG_HOMEPAGE='' CARGO_PKG_LICENSE='' CARGO_PKG_LICENSE_FILE='' CARGO_PKG_NAME=verbose-run CARGO_PKG_README='' CARGO_PKG_REPOSITORY='' CARGO_PKG_RUST_VERSION='' CARGO_PKG_VERSION=0.1.0 CARGO_PKG_VERSION_MAJOR=0 CARGO_PKG_VERSION_MINOR=1 CARGO_PKG_VERSION_PATCH=0 CARGO_PKG_VERSION_PRE='' CARGO_PRIMARY_PACKAGE=1 DYLD_FALLBACK_LIBRARY_PATH='/projects/verbose-run/target/debug/deps:/Users/whlo/.rustup/toolchains/beta-aarch64-apple-darwin/lib:/Users/whlo/lib:/usr/local/lib:/usr/lib' rustc --crate-name verbose-run --edition=2021 src/main.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=172 --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked -C metadata=99446b492124a920 -C extra-filename=-99446b492124a920 --out-dir /projects/verbose-run/target/debug/deps -C incremental=/projects/verbose-run/target/debug/incremental -L dependency=/projects/verbose-run/target/debug/deps`
    Finished dev [unoptimized + debuginfo] target(s) in 0.46s
     Running `CARGO=/projects/cargo/target/debug/cargo CARGO_MANIFEST_DIR=/projects/verbose-run CARGO_PKG_AUTHORS='' CARGO_PKG_DESCRIPTION='' CARGO_PKG_HOMEPAGE='' CARGO_PKG_LICENSE='' CARGO_PKG_LICENSE_FILE='' CARGO_PKG_NAME=verbose-run CARGO_PKG_README='' CARGO_PKG_REPOSITORY='' CARGO_PKG_RUST_VERSION='' CARGO_PKG_VERSION=0.1.0 CARGO_PKG_VERSION_MAJOR=0 CARGO_PKG_VERSION_MINOR=1 CARGO_PKG_VERSION_PATCH=0 CARGO_PKG_VERSION_PRE='' DYLD_FALLBACK_LIBRARY_PATH='/projects/verbose-run/target/debug/deps:/projects/verbose-run/target/debug:/Users/whlo/.rustup/toolchains/beta-aarch64-apple-darwin/lib/rustlib/aarch64-apple-darwin/lib:/Users/whlo/lib:/usr/local/lib:/usr/lib' target/debug/verbose-run`
Hello, world!

(Okay GitHub doesn't wrap lines 😕)

[epage]

I guess if we are already doing it for rustc, then doing it in this one case isn't too bad. We delineate sections and this is for one of many invocations.

[weihanglo]

FWIW, #12498 not only supports printing environment variables for cargo run -vv but also cargo test and cargo bench