Install different version of gcc
gcc 4.8
cd /etc/yum.repos.d
wget http://people.centos.org/tru/devtools-2/devtools-2.repo
yum install devtoolset-2-gcc
yum install devtoolset-2-binutils
yum install devtoolset-2-gcc-gfortran
yum install devtoolset-2-gcc-c++
source /opt/rh/devtoolset-2/enable
gcc 4.9
yum install centos-release-scl-rh centos-release-scl
yum check-update
yum install devtoolset-3-gcc devtoolset-3-gcc-c++
source /opt/rh/devtoolset-3/enable
gcc 5.2
yum install centos-release-scl-rh centos-release-scl
yum check-update
yum install devtoolset-4-gcc devtoolset-4-gcc-c++
source /opt/rh/devtoolset-4/enable
reference
http://mirror.centos.org/centos/6/sclo