[R-pkg-devel] Convention or standards for using header library (e.g. Eigen)

[Stephen Wade]

Doesnt seem like the system package is worth it. Should the convention
simply be to bundle the headers in the package then? What about package
size - is there some limit to the size of included libraries/headers to
consider for CRAN?

On Sat, 24 June 2023, 15:08 Simon Urbanek, <simon.urbanek using r-project.org>
wrote:

> Stephen,
>
> If you want to give the system version a shot, I would simply look for
> pkg-config, add the supplied CPPFLAGS to the package R flags if present and
> then test (regardless of pkg-config) with AC_CHECK_HEADER (see standard
> R-exts autoconf rules for packages). If that fails then use your included
> copy by adding the corresponding -I flag pointing to your supplied copy.
> You should not download anything as there is no expectation that the user
> has any internet access as the time of the installation so if you want to
> provide a fall-back, it should be in the sources of your package. That
> said, there is nothing wrong with ignoring the system version especially in
> this header-only case since you can then rely on the correct version which
> you tested - you can still allow the user to provide an option to override
> that behavior if desired.
>
> Cheers,
> Simon
>
>
>
> > On Jun 23, 2023, at 10:08 PM, Stephen Wade <stephematician using gmail.com>
> wrote:
> >
> > I recently submitted a package to CRAN which downloaded Eigen via
> Makevars
> > and Makevars.win. My Makevars.ucrt was empty as I noted that Eigen3 is
> > installed by default (however, this doesn't ensure that a version of
> Eigen
> > compatible/tested with the package is available).
> >
> > The source is currently on github:
> > https://github.com/stephematician/literanger
> >
> > Here is the Makevars
> >
> > $ more src/Makevars
> > # downloads eigen3 to extlibs/ and sets include location
> > PKG_CPPFLAGS = -I../src -I../extlibs/
> > .PHONY: all clean extlibs
> > all: extlibs $(SHLIB)
> > extlibs:
> >         "${R_HOME}/bin${R_ARCH_BIN}/Rscript" "../tools/extlibs.R"
> > clean:
> >         rm -f $(SHLIB) $(OBJECTS)
> >
> > The details of `extlibs.R` are fairly mundane, it downloads a release
> from
> > gitlab and unzips it to `extlibs`.
> >
> > CRAN gave me this feedback:
> >
> >> Why do you download eigen here rather than using the system version of
> >> Eigen if available?
> >>
> >> We asked you to do that for Windows as you did in Makevars.ucrt. For
> >> Unix-like OS you should only fall back (if at all) to some download if
> >> the system Eigen is unavailable.
> >
> > The problem is I'm not sure what a minimum standard to 'searching' for a
> > system version of Eigen looks like. I also note that packages like
> > RcppEigen simply bundle the Eigen headers within the package (and its
> > repository) which will certainly ignore any system headers.
> >
> > I would like a solution that would keep CRAN happy, i.e. i need to meet
> > some standard for searching for the compiler flags, checking the version
> of
> > the system headers, and then falling through to download release if the
> > system headers fail.
> >
> > 1.  For each platform (Unix, Windows, OS-X) what tool(s) should be
> invoked
> > to check for compiler flags for a header-only library like Eigen? e.g.
> > pkg-config, pkgconf? others?
> > 2.  What is a reasonable approach for the possible package names for
> Eigen
> > (e.g. typically libeigen3-dev on Debian, and eigen3 on arch, homebrew,
> > others)? Is this enough?
> > 3.  If pkg-config/pkgconf (or others) are unavailable, what is a
> reasonable
> > standard for checking if the library can be built with some reasonable
> > guess for the compiler flags (probably empty) - I assume I would need to
> > try to compile a test program (within Makevars)?
> > 4.  Following on from 3... would a package need to check (again via a
> test
> > program) that the _system_ headers have the correct version (e.g. some
> > static assert on EIGEN_WORLD_VERSION), and if that fails _then_ download
> > the release from gitlab?
> >
> > Any and all advice would be appreciated.
> >
> > Kind regards,
> > -Stephen Wade
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-package-devel using r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-package-devel
> >
>
>

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