build.rustflags config ignored, while inlines RUSTFLAGS works

[Nabellaleen]

Problem

When I call with inlined env values, everything works fine :

LD_LIBRARY_PATH='/path/to/dynamic/lib' RUSTFLAGS='-L /path/to/dynamic/lib -L locallibdir -ldynamiclib -lstaticlib' cargo run

But when I migrate to Cargo.toml, it fails :

// Cargo.toml
...
[build]
rustflags = "-L /path/to/dynamic/lib -L locallibdir -ldynamiclib -lstaticlib"
...

$ LD_LIBRARY_PATH='/opt/santesocial/fsv/1.40.13/lib' cargo run
// Error
...
  = note: some `extern` functions couldn't be found; some native libraries may need to be installed or have their path specified
...

Looks like these issues, somehow

• the .cargo/config.toml rustflags did not passed to the compiler #12794
• Cargo doesn't pass RUSTFLAGS "-L native=/path" to linker commands with -lffi #4452

Steps

No response

Possible Solution(s)

No response

Notes

I've check for other config which could override my Cargo.toml, but didn't find anything :

$  env | grep RUSTFLAGS
// Nothing
$ cargo +nightly -Z unstable-options config get --show-origin
# The following environment variables may affect the loaded values.
# CARGO_HOME=/home/user/.cargo
$ ls -la /home/user/.cargo
total 184
drwxr-xr-x. 1 user user    174  6 juil. 01:07 .
drwx------. 1 user user   1190  6 juil. 00:29 ..
drwxr-xr-x. 1 user user    324  3 juil. 19:15 bin
-rw-r--r--. 1 user user   1404  3 juil. 19:15 .crates2.json
-rw-r--r--. 1 user user    309  3 juil. 19:15 .crates.toml
-rw-r--r--. 1 user user    300 29 juin  23:13 env
-rw-r--r--. 1 user user 172032  6 juil. 01:07 .global-cache
-rw-r--r--. 1 user user      0 24 juin  21:25 .package-cache
-rw-r--r--. 1 user user      0 24 juin  21:25 .package-cache-mutate
drwxr-xr-x. 1 user user     50 24 juin  21:29 registry

And here are the logs of a build :

$ LD_LIBRARY_PATH='/path/to/dynamic/lib' cargo build -vv &> build.log

build.log

Version

cargo 1.79.0 (ffa9cf99a 2024-06-03)
release: 1.79.0
commit-hash: ffa9cf99a594e59032757403d4c780b46dc2c43a
commit-date: 2024-06-03
host: x86_64-unknown-linux-gnu
libgit2: 1.7.2 (sys:0.18.3 vendored)
libcurl: 8.6.0-DEV (sys:0.4.72+curl-8.6.0 vendored ssl:OpenSSL/1.1.1w)
ssl: OpenSSL 1.1.1w  11 Sep 2023
os: Fedora 39.0.0 [64-bit]

[weihanglo]

In the log file:

warning: unused manifest key: build

[build] is a table for the Cargo configuration, which is usually a file at <package-root>/.cargo/config.toml. Could you check that?

[Nabellaleen]

Nothing like that :/

$ find / -type f -name "config.toml" 2>/dev/null
/home/user/Projects/Utils/mage/site/config.toml
/home/user/Projects/Utils/mage/site/themes/learn/exampleSite/config.toml
/home/user/go/pkg/mod/github.com/magefile/mage@v1.15.0/site/config.toml
/home/user/go/pkg/mod/github.com/magefile/mage@v1.15.0/site/themes/learn/exampleSite/config.toml
/home/user/go/pkg/mod/github.com/!three!dots!labs/watermill@v1.3.5/docs/config.toml
/home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/create-tauri-app-4.0.1/.cargo/config.toml
/home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/console-0.15.8/.cargo/config.toml
/home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tiny-skia-0.11.4/.cargo/config.toml
/home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/dialoguer-0.11.0/.cargo/config.toml
/home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bytemuck-1.16.1/.cargo/config.toml
/home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/cfg-expr-0.15.8/.cargo/config.toml
/home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wry-0.40.1/.cargo/config.toml
/home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wry-0.41.0/.cargo/config.toml
/etc/containerd/config.toml

And indeed, this warning is interesting : it appears only when I add the [build] table with the rustflags entry in my Cargo.toml

[Nabellaleen]

Doh ... I get it.

Indeed, it's a confusion from me (and many others, it seems ^^) that this cargo config NEED to be in a .cargo/config.toml file and not in the Cargo.toml (even if its name let suppose it ... XD)

Why is there a separate file config.toml and this is not in the Manifest ?

[weihanglo]

See below issues for relevant discussions:

• Tracking Issue: Support project-specific config in manifest #12738
• https://internals.rust-lang.org/t/proposal-move-some-cargo-config-settings-to-cargo-toml/13336