[R-pkg-devel] Rcpp with clang++ -stdlib=libc++ ?

[Kevin Ushey]

My understanding is that many Linux OSes package the clang compiler, the
libc++ standard library, and the headers used by the libc++ standard
library separately. To install those headers, you likely need (e.g. on
Ubuntu):

    sudo apt install libc++-dev libc++abi-dev

to be able to build and compile programs against libc++.

This also comes with the caveat that mixing programs built against
different standard library implementations is in general a bad idea, so you
may see issues if you mix libraries compiled with libstdc++ and libc++ in
the same R session. (This can come up with R packages that link to other
libraries installed on the system, which will typically be built with and
linked against the "default" system compiler + standard library
implementations.) I'm not sure if this will be an issue in practice with
what you're doing, but it's worth being aware of.

Best,
Kevin

On Sat, Sep 12, 2020 at 5:50 AM Dirk Eddelbuettel <edd using debian.org> wrote:

>
> Hi Jens,
>
> On 11 September 2020 at 21:00, Dr. Jens Oehlschlägel wrote:
> | I can compile a package under clang++ with -stdlib=libstdc++, but with
> -stdlib=libc++ I get
> |
> | "
> | In file included from
> /home/jo/R/x86_64-pc-linux-gnu-library/4.0/Rcpp/include/Rcpp/r/headers.h:67:
> |
> /home/jo/R/x86_64-pc-linux-gnu-library/4.0/Rcpp/include/Rcpp/platform/compiler.h:100:10:
> fatal error: 'cmath' file not found
> | #include <cmath>
> |          ^~~~~~~
> | 1 error generated.
> | "
> |
> | Is there any howto for using Rcpp with -stdlib=libc++ ?
>
> That has zero to do with Rcpp.  You are lacking a C++ library header when
> switching the C++ standard library along with clang. Nothing that Rcpp
> ships,
> or governs, or selects.
>
> I am forgetting the fine details here (and someone may hopefully fill in
> fuller details) but in short, "that is just the way it is".  I think we
> simply pivot back to the g++ standard C++ library even when using clang++.
>
> Cheers from Chicago,  Dirk
>
> | Greetings from Munich
> |
> | Jens Oehlschlägel
> |
> |
> | P.S.
> |
> | Package Makevars
> | CXX_STD = CXX17
> | PKG_CXXFLAGS=-O3 -march=native -pthread
> | PKG_LIBS=-latomic -pthread
> |
> | ~.R/Makevars
> | CXX17 = clang++ -stdlib=libc++
> | CXX17FLAGS = -fstack-protector-strong -D_FORTIFY_SOURCE=2 -g $(LTO)
> | CXX17STD = -std=c++17
> |
> | > packageVersion("Rcpp")
> | [1] ‘1.0.5’
> |
> | > version
> |                _
> | platform       x86_64-pc-linux-gnu
> | arch           x86_64
> | os             linux-gnu
> | system         x86_64, linux-gnu
> | status
> | major          4
> | minor          0.2
> | year           2020
> | month          06
> | day            22
> | svn rev        78730
> | language       R
> | version.string R version 4.0.2 (2020-06-22)
> | nickname       Taking Off Again
> |
> | ______________________________________________
> | R-package-devel using r-project.org mailing list
> | https://stat.ethz.ch/mailman/listinfo/r-package-devel
>
> --
> https://dirk.eddelbuettel.com | @eddelbuettel | edd using debian.org
>
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>

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