To install newer versions of GCC on RHEL, you should install the relevant GCC toolset. Toolsets are available for each major GCC release stream; they are all co-installable and don’t replace the system GCC.

Currently the best option is GCC toolset 15 which is supported until November 2029.

On a system with access to RHEL repositories (online or through Satellite for example), install the toolset with

sudo yum install gcc-toolset-15

or

sudo dnf install gcc-toolset-15

To compile C++17 code, you’d use

scl enable gcc-toolset-15 g++ …

(GCC 15 defaults to C++17 with GNU extensions).

For offline installation see How to use yum to get all RPMs required, for offline use?

CentOS 8 already comes with GCC 8.

On CentOS 7, you can install GCC 8 from Developer Toolset. First you need to enable the Software Collections repository:

yum install centos-release-scl

Then you can install GCC 8 and its C++ compiler:

yum install devtoolset-8-gcc devtoolset-8-gcc-c++

To switch to a shell which defaults gcc and g++ to this GCC version, use:

scl enable devtoolset-8 -- bash

You need to wrap all commands under the scl call, so that the process environment changes performed by this command affect all subshells. For example, you could use the scl command to invoke a shell script that performs the required actions.

I feel foolish because I figured it out right after posting, but I figured I'd share because it isn't intuitive and hopefully this will save someone some time.

The package you want to install is not gcc. You want to install gcc-toolset-9. You will notice after installation that you will still get 8.x if you do a gcc --version. gcc-toolset-9 installs to /opt. The idea is to give you a separate development environment. See this documentation. After installation you can run the updated gcc with /opt/rh/gcc-toolset-9/<username>/bin/gcc.

As @Stephen Kitt pointed out, you can actually get a shell with the updated toolset by running scl enable gcc-toolset-9 bash. Running this command will open a new bash session with the environment variables appropriately updated.

You can also run gcc v.9 directly with scl enable gcc-toolset-9 gcc <your_gcc_args>. See this documentation for details.

yum install centos-release-scl-rh
yum install devtoolset-3-gcc devtoolset-3-gcc-c++
update-alternatives --install /usr/bin/gcc-4.9 gcc-4.9 /opt/rh/devtoolset-3/root/usr/bin/gcc 10
update-alternatives --install /usr/bin/g++-4.9 g++-4.9 /opt/rh/devtoolset-3/root/usr/bin/g++ 10

Since the package is either not available, or using a different name, the first step is to find which is the case. Use

yum list available |grep gcc
yum list available |grep devtoolset

to find whether you have misspelled the package name, or if gcc is available under a different name. Check using yum info for the package. Its description should show the relevant version information.

According to Red Hat's article What gcc versions are available in Red Hat Enterprise Linux?, gcc 4.8 is available for Red Hat Enterprise 7. If you need gcc 4.8 for RHEL 6, you may have to compile it yourself.

Further reading:

• Installing GCC 4.8.2 on Red Hat Enterprise linux 6.5
• How to Install gcc 4.7.x/4.8.x on CentOS
• install latest gcc on rhel 6 x86_64

Now devtools-8 is available and it's possible to use it by following commands:

yum install centos-release-scl
yum install devtoolset-8-gcc devtoolset-8-gcc-c++
scl enable devtoolset-8 -- bash

It's explained in a little more detail in this answer on StackOverflow: How to install GCC/G++ 8 on CentOS. And of course, if you need GFortran, you can install it in the same way - the package is devtoolset-8-gcc-gfortran.

The easiest method by far is to make use of a binary build that's provided through a YUM repository. One such option would be to use the hop5.in repository. Specifically this page: gcc - Various compilers (C, C++, Objective-C, Java, ...). They're providing 4.8.2 which should work with CentOS 6.3 or 6.4. You might want to do an update prior:

$ sudo yum update

The other option would be to make use of the Developer Toolset, specifically the bundled version provided by Scientific Linux.

• http://linux.web.cern.ch/linux/devtoolset/

Following the installation instructions you'll basically do the following 2 steps:

$ sudo wget -O /etc/yum.repos.d/slc6-devtoolset.repo \
    http://linuxsoft.cern.ch/cern/devtoolset/slc6-devtoolset.repo
$ wget -O /etc/yum.repos.d/slc5-devtoolset.repo \
    http://linuxsoft.cern.ch/cern/devtoolset/slc5-devtoolset.repo

$ sudo yum install devtoolset-2

Update #1

The hop5.in YUM repository appears to have been removed, so the only recourse is to make use of the devtoolset method highlighted above.

Additional examples for installing via devtoolset are highlighted in this GitHub Gist: Installing gcc 4.8 and Linuxbrew on CentOS 6.

devtoolset is called gcc-toolset in RHEL8.

The following commands worked for me:

microdnf install -y gcc-toolset-12
scl enable gcc-toolset-12 bash
gcc --version
# gcc (GCC) 12.1.1 20220628 (Red Hat 12.1.1-3)