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

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 at debian.org 
<mailto:edd at debian.org>> wrote:


    Hi Jens,

    On 11 September 2020 at 21:00, Dr. Jens Oehlschl?gel 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 Oehlschl?gel
    |
    |
    | 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 at r-project.org
    <mailto:R-package-devel at r-project.org> mailing list
    | https://stat.ethz.ch/mailman/listinfo/r-package-devel

    -- 
    https://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org
    <mailto:edd at debian.org>