Red Hat Software Collections "Software Collections give you the power to build, install, and use multiple versions of software on the same system, without affecting system-wide installed packages"
For instance, RHEL6 comes with gcc 4.4.7, but also provides 4.9 and 5.2 via Software Collections (SCL)
And there are other related RPMs (fortran, c++, etc.). To see what is available run the command
yum list devtoolset-4\*
The yum repo for SCL is SLAC RHEL6 Server Software Collections (slac-rhel-x86_64-server-6-rhscl-1). These are installed on public login hosts, if you do not have sudo on a host where it is needed, please send an email to unix-admin@slac.stanford.edu
The RPM names for the versions of gcc are:
devtoolset-3-gcc-4.9.2-6.2.el6.x86_64
devtoolset-4-gcc-5.2.1-2.2.el6.x86_64
To use the newer versions after the RPMs are installed:
user@host $ scl enable devtoolset-4 bash
bash-4.1$ gcc --version
gcc (GCC) 5.2.1 20150902 (Red Hat 5.2.1-2)
bash-4.1$ exit
user@host $ scl enable devtoolset-3 bash
bash-4.1$ gcc --version
gcc (GCC) 4.9.2 20150212 (Red Hat 4.9.2-6)
bash-4.1$ exit