How to change compiler version to build an Rcpp-based package? - r

Question

I'm authoring a package that uses an external .so library and a header file. I notice that it works with g++-4.9 but not g++5.0 or above after I compiled the demo code in pure C++ for testing. My system default is g++ 5.4.0.
I tried adding CXX=g++-4.9 to ./configure and src/Makevars but the compiler still turns out to be system default g++. I don't want to modify global configuration (e.g. in ~/.R/Makevars) because it will influence other package builds.
Is there a local way to specify the compiler version Rcpp uses to compile cpp files when I build this package?

Answer 1

Step 1: Set CXX for all varieties in src/Makevars this comes about because you might be using CXX_STD = CXX11 so CXX11 is used instead of CXX...
CXX=g++-4.9
CXX1X=g++-4.9
CXX11=g++-4.9
CXX14=g++-4.9
Note: This assumes you are only compiling C++ code.
Step 2: Test for gcc 4.9 in configure.ac with:
AC_PREREQ(2.61)
AC_INIT(your_package_name_here, m4_esyscmd_s([awk -e '/^Version:/ {print $2}' DESCRIPTION]))
AC_COPYRIGHT(Copyright (C) 2017 your name?)
## Determine Install Location of R
: ${R_HOME=$(R RHOME)}
if test -z "${R_HOME}"; then
AC_MSG_ERROR([Could not determine R_HOME.])
fi
## Setup RBin
RBIN="${R_HOME}/bin/R"
CXX=`"${RBIN}" CMD config CXX`
CPPFLAGS=`"${RBIN}" CMD config CPPFLAGS`
CXXFLAGS=`"${RBIN}" CMD config CXXFLAGS`
## We are using C++
AC_LANG(C++)
AC_REQUIRE_CPP
## Check the C++ compiler using the CXX value set
AC_PROG_CXX
## If the compiler is g++, then GXX is set so version information can be exaimed
if test "${GXX}" = yes; then
AC_MSG_CHECKING([whether g++ version is sufficient])
gxx_version=$(${CXX} -v 2>&1 | awk '/^.*g.. version/ {print $3}')
case ${gxx_version} in
4.9.*)
AC_MSG_RESULT([(${gxx_version}) yes])
;;
1.*|2.*|3.*|4.0.*|4.1.*|4.2.*|4.3.*|4.4.*|4.5.*|4.6.*|4.7.*|4.8.*|5.*|6.*|7.*)
AC_MSG_RESULT([no])
AC_MSG_WARN([Only g++ version 4.9.* be used to compile this package.])
AC_MSG_ERROR([Please set the default compiler to gcc++-4.9.])
;;
esac
else
AC_MSG_WARN([The package uses an external shared library that only compiles with gcc++-4.9])
AC_MSG_ERROR([Please set the default compiler to gcc++-4.9.])
fi
AC_OUTPUT