Answer
sudo apt install build-essential manpages-dev software-properties-common
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt update && sudo apt install gcc-11 g++-11
Then use update-alternatives to set default gcc...
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 90 --slave /usr/bin/g++ g++ /usr/bin/g++-9 --slave /usr/bin/gcov gcov /usr/bin/gcov-9 --slave /usr/bin/gcc-ar gcc-ar /usr/bin/gcc-ar-9 --slave /usr/bin/gcc-ranlib gcc-ranlib /usr/bin/gcc-ranlib-9 --slave /usr/bin/cpp cpp /usr/bin/cpp-9 && \
sudo update-alternatives –install /usr/bin/gcc gcc /usr/bin/gcc-11 110 –slave /usr/bin/g++ g++ /usr/bin/g++-11 –slave /usr/bin/gcov gcov /usr/bin/gcov-11 –slave /usr/bin/gcc-ar gcc-ar /usr/bin/gcc-ar-11 –slave /usr/bin/gcc-ranlib gcc-ranlib /usr/bin/gcc-ranlib-11 –slave /usr/bin/cpp cpp /usr/bin/cpp-11;
To sample check settings to see which gcc is default you can run the following, if they show correct resuslts then the rest are fine...
gcc --version;g++ --version;gcov --version;
To reconfigure to any previous gcc version...
sudo update-alternatives --config gcc
You can do this on any version of ubuntu,... enjoy!
Here are my 6 different gcc's living side by side with the default being gcc-11:
$ sudo update-alternatives --config gcc
There are 6 choices for the alternative gcc (providing /usr/bin/gcc).
Selection Path Priority Status
- 0 /usr/bin/gcc-11 1010 auto mode
1 /usr/bin/gcc-10 1000 manual mode
2 /usr/bin/gcc-11 1010 manual mode
3 /usr/bin/gcc-5 40 manual mode
4 /usr/bin/gcc-7 700 manual mode
5 /usr/bin/gcc-8 800 manual mode
6 /usr/bin/gcc-9 900 manual mode
Press <enter> to keep the current choice[*], or type selection number: