[R-pkg-devel] Is it a wrong assumption that ${R_HOME}/lib always exists?

[Hiroaki Yutani]

Hi,

My package, string2path, using Rust fails on the CRAN check of MKL [1],
with an error that seems irrelevant to MKL. The error says:

>   thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value:
Os { code: 2, kind: NotFound, message: "No such file or directory" }',
/data/gannet/ripley/R/packages/tests-MKL/string2path/src/rust/vendor/libR-sys/build.rs:637
:40

The line 637 of build.rs of libR-sys crate is here [2]:

    r_paths.library.canonicalize().unwrap().display()

Compared to the previous version, which didn't experience such a failure,
.canonicalize() was added, and it seems this is the cause. This method
normalizes the path expression like R's normalizePath(), and it fails
because the path specified didn't exist.

libR-sys assumes the path to R's shared libraries is `${R_HOME}/lib` on
Unix-alike platforms. Is it possible that this path doesn't exist on the
MKL server? Actually, it compiles fine on the other Linux platforms, so I'm
wondering what's different there from the other servers.

Best,
Yutani

[1]: https://cran.r-project.org/web/checks/check_results_string2path.html
[2]: https://github.com/extendr/libR-sys/blob/v0.5.0/build.rs#L637C1-L637C58

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