Building ROOT

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In the pCT project we need to use a version of ROOT which is compiled with c++17 in order to build packages with ROOT dependencies with c++17 standard. .

ROOT implements a custom adaptor to std::string_view if not compiled with c++17 and this conflicts with the real one if a packages uses c++17 standard and ROOT libraries/includes.

sudo yum install git cmake gcc-c++ gcc binutils \
libX11-devel libXpm-devel libXft-devel libXext-devel \
gcc-gfortran openssl-devel pcre-devel \
mesa-libGL-devel mesa-libGLU-devel glew-devel ftgl-devel mysql-devel \
fftw-devel cfitsio-devel graphviz-devel \
avahi-compat-libdns_sd-devel libldap-dev python-devel \
libxml2-devel gsl-static gsl-devel \
libAfterImage libAfterImage-devel

sudo python3 -m pip install numpy

# clone the repository and select version
git clone http://github.com/root-project/root.git
cd root
git checkout v6-20-00-rc1

# choose a build directory
mkdir build_root; cd build_root

scl enable devtoolset-8 bash

# configure: choose install target, on the lab machine we need to disable asimage for some reason
# the important flag is the C++ standard
cmake3 -DCMAKE_INSTALL_PREFIX=/opt/root -DCMAKE_CXX_STANDARD=17 -DPYTHON_EXECUTABLE=/usr/bin/python3 ../

#build and install
sudo cmake3 --build . --target install -- -j4

Remember to add root details to your environment, e.g. /etc/bashrc: (LD_LIBRARY_PATH and PYTHONPATH must BOTH be set for pyroot to work)

export ROOTSYS=/opt/root
source $ROOTSYS/bin/thisroot.sh

export LD_LIBRARY_PATH=/opt/root/lib:$LD_LIBRARY_PATH

export PYTHONPATH=/opt/root/lib:$PYTHONPATH