in a nutshell, here are some examples for how to install and configure

• for python3 to get python3.9: dnf install -y python39 && alternatives --set python3 $(command -v python3.9)
• for gcc to get gcc-12: dnf install gcc-toolset-12 && source scl_source enable gcc-toolset-12
• for java to get java-17: dnf install java-17 && bin_java_filename=$(rpm -qa|grep java-17|xargs rpm -ql|grep "bin\/java$"|head -1) && alternatives --set java ${bin_java_filename}
• tested on rocky8, rocky9

which repo has the newer software versions?

• the old method using "SCL" was deprecated
• the new method is to use a repo called "appstream"
• here is a post written by the distro maintainers explaining the change https://developers.redhat.com/blog/2018/11/15/rhel8-introducing-appstreams
• the repo is enabled by default

how to: install newer software versions?

• for python3: dnf install python39
• for gcc: dnf install gcc-toolset-12

how to: change the system default?

• for python3: alternatives --set python3 $(command -v python3.9)
• for gcc:
  • edit your user .bashrc or .bash_profile or create a new file under /etc/profile.d/ with the following: source scl_source enable gcc-toolset-12
  • i thought scl_source would go away in el8, el9 but apparently not
  • for more info on scl_source go to this link https://unix.stackexchange.com/a/195219/5510 or Permanently enable RHEL scl

p.s. what is the difference between alternatives and update-alternatives?

• the original tool is called update-alternatives and is from Debian linux distro
• in EnterpriseLinux, Redhat rewrote the tool and called it alternatives and when you install alternatives the package also installs a symlink with name update-alternatives on your env var PATH to help you find the tool
• the two are similar but not the same because their source code is different

gcc-12 is not available in ubuntu 20.04, so we need to compile it from source code, here are the steps which I borrowed from this video:

• Step 1: clone gcc source code and checkout gcc-12 branch

$ git clone https://gcc.gnu.org/git/gcc.git gcc-source
$ cd gcc-source/
$ git branch -a
$ git checkout remotes/origin/releases/gcc-12

• Step 2: make another build dir

Note this is important as running ./configure from within the source directory is not supported as documented here.

$ mkdir ../gcc-12-build
$ cd ../gcc-12-build/
$ ./../gcc-source/configure --prefix=$HOME/install/gcc-12 --enable-languages=c,c++

• Step 3: installing GCC prequisites and run configure again

The missing libraries will be shown in above ./confgiure output, search and install them one by one.

$ apt-cache search MPFR
$ sudo apt-get install libmpfrc++-dev
$ apt-cache search MPC | grep dev
$ sudo apt-get install libmpc-dev
$ apt-cache search GMP | grep dev
$ sudo apt-get install libgmp-dev
$ sudo apt-get install gcc-multilib
$ ./../gcc-source/configure --prefix=$HOME/install/gcc-12 --enable-languages=c,c++

An alternative is to run the download_prerequisites script.

$ cd ../
$ cd gcc-source/
$ ./contrib/download_prerequisites
$ ./../gcc-source/configure --prefix=$HOME/install/gcc-12 --enable-languages=c,c++

• Step 4: compile gcc-12

$ make -j16

Still flex is missing:

$ sudo apt-get install flex
$ ./../gcc-source/configure --prefix=$HOME/install/gcc-12 --enable-languages=c,c++
$ make -j16
$ make install

Another way is to use Ubuntu 22.04 where gcc-12 is available. In Ubuntu 22.04, gcc-12 can be installed with apt:

$ sudo apt install gcc-12