Ubuntu16.04 安装 gcc 4.8

check the gcc version use command 

gcc --version

the first step:

sudo apt-get install gcc-4.8

then:

ls /usr/bin/gcc*

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 100

sudo update-alternatives --config gcc

check the gcc version again:

gcc --version

done

install g++ in the same way as gcc

note that:

gcc is for C, and g++ is for C++

reference:

https://www.linuxidc.com/Linux/2017-03/142299.htm