For installing the system compilers gcc, g++, the install command is # yum install gcc-c++ → Provides version 4.8.5 : /usr/bin/{ gcc, g++ }.

Other options: 1. gcc53-c++-5.3.0-1.el6.x86_64.rpm → https://drive.google.com/file/d/0B7S255p3kFXNRm9FVnZYUnhyZzg/view?usp=sharing&resourcekey=0-1N6zQa6Sbl_WycG1O9I7JA : Download and install : # cd Downloads/ && yum install ./gcc53-c++-5.3.0-1.el6.x86_64.rpm ..... Provides /usr/bin/{gcc53, g++53}.

2. The devtoolset´s : https://www.softwarecollections.org/en/scls/rhscl/devtoolset-6/ → # yum-config-manager --enable rhel-server-rhscl-7-rpms

Install gcc, g++ version 4.9.2 : # yum install devtoolset-3-gcc-c++

Note : You can have as many gcc/g++ versions as you want, installed at the same time. ( The system compilers are a must.)

3. gcc49-c++-4.9.3-1.el6.x86_64.rpm https://drive.google.com/file/d/1Pwq1ua80dGM72i7rpDNAIIdfcR1WK-hG/view?usp=sharing → Provides /usr/bin/{gcc49, g++49}.

4. gcc63-c++-6.3.0-1.el7.x86_64.rpm https://drive.google.com/file/d/1t4WrgvpEP-6_NN3qMJhz9MS3CJhHrHKc/view?usp=sharing → Provides /usr/bin/{gcc63, g++63}.

5. gcc45-c++-4.5.4-1.el7.x86_64.rpm https://drive.google.com/file/d/15aRg-BPhuyaEyZA9Jy-iAyC21_pwN7nD/view?usp=sharing → Provides /usr/bin/{gcc45, g++45, gfortran45}

6. gcc42-c++-4.2.4-1.el6.x86_64.rpm https://drive.google.com/file/d/1eYWk6Nd63xeqqAUoJldNWRuwEGO6cAyv/view?usp=sharing → Provides /usr/bin/{gcc42, g++42}

7. gcc73-c++-7.3.0-1.el7.x86_64.rpm https://drive.google.com/file/d/1PgwCP5tu8D0EJbJVTqJd7Vg8dJ4l4noi/view?usp=sharing → Provides /usr/bin/{gcc73, g++73}

8. gcc48-c++-4.8.5-1.el6.x86_64.rpm https://drive.google.com/file/d/1w6fW6oSflDDYZt_cOpGj3QMEmzUC8Q9L/view?usp=sharing → Provides /usr/bin/{gcc48, g++48, gfortran48}

9. gcc84-c++-8.4.0-1.el7.x86_64.rpm https://drive.google.com/file/d/1xgFtsiDi2uiB1B0AcOaSpxVizzET-pJf/view?usp=sharing → Provides /usr/bin/{gcc84, g++84, gfortran84}

One can surely build the gcc on CentOS oneself(though ew!).

Generally follow the below steps:

sudo yum -y update
sudo yum -y install bzip2 wget gcc gcc-c++ gmp-devel mpfr-devel libmpc-devel make
gcc --version
wget http://mirrors-usa.go-parts.com/gcc/releases/gcc-8.2.0/gcc-8.2.0.tar.gz
tar zxf gcc-8.2.0.tar.gz
mkdir gcc-8.2.0-build
cd gcc-8.2.0-build
../gcc-8.2.0/configure --enable-languages=c,c++ --disable-multilib
make -j 2
sudo make install
gcc --version

At this point, many can not see 8.2, i.e.

gcc version 4.8.5 (GCC)

Just overwrite the old gcc with which just built, i.e.

# which gcc
/usr/local/bin/gcc
# cp gcc/xgcc /usr/local/bin/gcc
# gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/aarch64-unknown-linux-gnu/7.2.0/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: ../gcc-7.2.0/configure --enable-languages=c,c++ --disable-multilib
Thread model: posix
gcc version 7.2.0 (GCC)

In order to avoid library error, one may need update libstdc as well,

cp ./aarch64-unknown-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6 /usr/local/lib64/libstdc++.so.6
cp ./stage1-aarch64-unknown-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6 /usr/lib64/libstdc++.so.6

One may also update libc.so as well, i.e. 2.18

curl -O http://ftp.gnu.org/gnu/glibc/glibc-2.18.tar.gz
tar zxf glibc-2.18.tar.gz
cd glibc-2.18/
mkdir build
cd build/
../configure --prefix=/usr
make -j2
make install
ln -sf /usr/glibc-2.18/glibc-2.18.so /lib64/libc.so.6

Finally, type /lib64/libc.so.6 to confirm

Mostly, ln would fail, since old relations, and LD is suggested, i.e.

LD_LIBRARY_PATH=/usr/glibc-2.18/lib
export LD_LIBRARY_PATH