[R-pkg-devel] flang doesn't support derived types

[Ivan Krylov]

В Thu, 09 May 2024 15:31:25 +0000
Othman El Hammouchi <othman.el.hammouchi using protonmail.com> пишет:

> Do I understand it correctly that there is no way to specify a
> Fortran standard in the SystemRequirements?

It's possible (and even recommended) to describe the Fortran version
requirement in SystemRequirements [1], but this field is for now mostly
informational. I think I remember efforts to standardise it, but they
are far from complete.

> I had resubmitted my package in the mean time with a configure script
> that aborts the install if the compiler does not support
> polymorphism, but I understand that this is a fruitless avenue for
> CRAN?

Signs point to yes, at least judging by a previous time we had
flang-related problems [2]. On the other hand, there were relatively
easy workarounds that time, and here I'm not seeing anything as simple.

> I should point out my local flang install is version 16, but I cannot
> install 18 on my system since it's in unstable (this again
> underscores the problem of developing under these constraints).

Would you consider containers for this purpose? I was able to reproduce
the problem relatively quickly by starting podman run --rm -it
debian:sid and installing flang-18 in there. (Unlike Docker a few years
ago, podman can be installed straight from the repository, at least on
Debian, and doesn't require adding users to special groups in order to
work. Maybe Docker has also improved.) I don't like containers as a
basis for software distribution, but I can't deny that they are being
great at letting me quickly reproduce problems without installing 10
different GNU/Linux distros.

> What would you advise? And don't you think these Fortran constraints
> should be better documenten.

I'm afraid I don't have any more specific advice besides testing your
workarounds with Debian Sid in a container or a virtual machine or a
chroot. I can try to take a look at more concrete problems. I hope you
will be able to find a relatively painless workaround.

I do wish that flang-new would be a better compiler or at least a
better documented one, but instead of a list of features on their
website, I can only see "Getting Involved [3] for tips on how to get in
touch <...> and to learn more about the current status". There is only
so many projects one can get involved in.

-- 
Best regards,
Ivan

[1]
https://cran.r-project.org/doc/manuals/R-exts.html#Using-modern-Fortran-code

[2]
https://stat.ethz.ch/pipermail/r-package-devel/2023q4/010065.html

[3]
https://flang.llvm.org/docs/GettingInvolved.html