I recently tried to downgrade to gcc 4.7 since a cfd code I was working on didn't compile with the latest gcc version. But after many errors and the code still not compiling I gave up and would like to go back to the latest gcc and g++ compilers however it seems I may have messed something up.
When I do:
sudo update-alternatives --remove-all gcc sudo update-alternatives --remove-all g++ sudo apt-get install gcc-6.2 g++-6.2
or even gcc-5.1 g++-5.1 for that matter, it gives me the following error
Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package gcc-6.2 E: Couldn't find any package by glob 'gcc-6.2' E: Couldn't find any package by regex 'gcc-6.2' E: Unable to locate package g++-6.2 E: Couldn't find any package by glob 'g++-6.2' E: Couldn't find any package by regex 'g++-6.2'
and I also tried doing this before
sudo add-apt-repository ppa:ubuntu-toolchain-r/test sudo apt-get update sudo apt-get install gcc-6.2 g++-6.2
but it doesn't seem to work. Finally when I just do
sudo apt-get install gcc
Reading package lists... Done Building dependency tree Reading state information... Done gcc is already the newest version (4:5.3.1-1ubuntu1).
I know I still need to install and configure alternatives but doing that doesn't work either as follows
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5.3 10 sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-5.3 10 sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30 sudo update-alternatives --set cc /usr/bin/gcc sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30 sudo update-alternatives --set c++ /usr/bin/g++ sudo update-alternatives --config gcc sudo update-alternatives --config g++
Sorry this ended up quite long and please let me know if you need more info. Thanks!
EDIT: I actually got it to work by changing gcc-5.3 to gcc-5 in the above code as that seemed to be what it's called in usr/bin. I will keep it for future reference if anyone faces the same problem.