Centos 7.6 gcc (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5)

yum install -y wget lftp gcc gcc-c++ make openssl-devel pcre-devel pcre

yum install -y http://mirror.centos.org/centos/7/extras/x86_64/Packages/centos-release-scl-rh-2-3.el7.centos.noarch.rpm

sudo yum install -y http://mirror.centos.org/centos/7/extras/x86_64/Packages/centos-release-scl-2-3.el7.centos.noarch.rpm

yum provides gcc

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 * centos-sclo-rh: mirrors.bupt.edu.cn
devtoolset-7-gcc-7.1.1-2.1.el7.x86_64 : GCC version 7
Repo        : centos-sclo-rh
Matched from:
Provides    : gcc = 7.1.1-2.1.el7

gcc-4.8.5-44.el7.x86_64 : Various compilers (C, C++, Objective-C, Java, ...)
Repo        : base

devtoolset-7-gcc-7.1.1-2.1.el7.x86_64 : GCC version 7
Repo        : @centos-sclo-rh
Matched from:
Provides    : gcc = 7.1.1-2.1.el7

gcc-4.8.5-44.el7.x86_64 : Various compilers (C, C++, Objective-C, Java, ...)
Repo        : @base

yum install devtoolset-7-gcc-c++ -y

source /opt/rh/devtoolset-7/enable
gcc --version
g++ --version
mv /usr/bin/gcc /usr/bin/gcc-4.8.5
ln -s /opt/rh/devtoolset-7/root/bin/gcc /usr/bin/gcc
gcc --version

 gcc --version
gcc (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5)
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

 g++ --version
g++ (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5)
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.