[R-pkg-devel] Compiler choice on CRAN (R-windows-oldrel)

I don't have hard info on ABI compatibility between gcc versions, but there have been issues in the past, at least with with gfortran.

Now, many people/schools will have R-3.2.x installed, built with gcc 4.6.y. We cannot retroactively recompile their installation, nor expect them to install a new version built with gcc 4.9.z. This raises a specific question and a generic one:

- specific: Will a package binary of gower built with 4.9 work with R built with 4.6?
- generic: Is is sufficiently likely that a given package if compiled with a different compiler version that CRAN would consider having a mechanism to specify a particular compiler version?

I suspect that the answer to the second question is no.

Whether to condition on R >= 3.3 is a good idea largely depends on two things

- the user base (would they upgrade R anyways?)
- are there other packages that depends on gower? (CRAN keeps only the newest version of a package so requiring a newer R could affect users with less aggressive update policies. This already happened when the pbkrtest package update rendered the car package unloadable.)

You do have a 4th option: conditionalize the _code_ on the R version, then remove old-style code when 3.2.x becomes history.

-pd

Dear listers,


Compilation of my gower pkg fails on R-oldrel-windows. I am pretty sure
that this is because it uses gcc 4.6.3 which has limited support for OpenMP
(the errors are the same as I got on the old travis-ci build environment,
see my related question[1]).

Now, according to the Rtools page[2], since R3.2.2 "Both the gcc 4.6.3
toolchain and a toolchain based on gcc 4.9.3 and mingw-w64 v3 are now
included." Not sure what that says about CRAN, but I'm hoping/guessing it
uses Rtools the same way as we do.

So I guess I have the following options:

- make my package depend on R>=3.3
- Alter my code (as kindly suggested by Ott Toomet in [1])
- Tell CRAN to use the modern compiler.

Obviously, the latter would be easiest. Is this is even possible? For a
local installation I could set an environment variable[3], but how about
doing this at CRAN?

Thanks,
Mark


[1] https://stat.ethz.ch/pipermail/r-package-devel/2016q3/000983.html
[2] https://cran.r-project.org/bin/windows/Rtools/
[3]
https://cran.r-project.org/doc/manuals/r-release/R-admin.html#Customizing-package-compilation

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