Update GCC on Ubuntu

I am on a project that needs GCC 10.x or later.

At this time I have GCC 9.4.0 on Ubuntu 20.04.1. I tried to update the compiler, but it does not work.

Can anybody give me an advice for the update?

I read on the gcc website that version 9.4 is more up-to-date than some 10.x versions. How is Gcc structured?

among other things I tried:

sudo apt-get install gcc-10.2 g++-10.2

but after all my gcc version is still 9.4

gcc (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0

1 Answer

This is a common pattern in linux. When there are multiple versions of the same program installed, though the executables are all present in the /usr/bin/ directory, only one of them is "visible" as that program. For example, if you install gcc-9 and gcc-10, both executables are present as /usr/bin/gcc-9 and /usr/bin/gcc-10 but only one of them is visible as gcc. This happens by symlinking a preferred version to the same directory as /usr/bin/gcc. In ubuntu 20.04, the preferred version is gcc-9 and so, gcc-9 is symlinked as gcc.

You can check this by running the following command.

$ which gcc | xargs file

The output will be

/usr/bin/gcc: symbolic link to gcc-9

There are a few things you can do to use gcc-10 as your c compiler.

1. Directly call the gcc-10 executable. Instead of using gcc <code.c>, call gcc-10 <code.c>.
2. You can manually symlink gcc-10 as the preferred gcc. Assuming you did not modify the system paths, the following command can be used.

# ln -s /usr/bin/gcc-10 /usr/local/bin/gcc

This works because, by default, the executables in /usr/local/bin/ take precedence over /usr/bin/.

3. If you are using bash, you can create an alias for gcc as gcc-10. Add the following line to your .bashrc.

alias gcc="gcc-10"

Remember to relaunch bash or source ~/.bashrc.

4. Using update-alternatives (Thanks to @ted-lyngmo for pointing it out). Debian based distributions supply a separate program, that can make symlinking easier / more functional. Read more using man update-alternatives. To use gcc-10 as the preferred gcc, use the following command.

# update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 60

The above command says, /usr/bin/gcc is the link needed and the name is gcc, the target executable is /usr/bin/gcc-10 and it has a priority of 60.

This links gcc to /etc/alternatives/gcc, which itself is a symlink to /usr/bin/gcc-10. If a higher priority program is added to update-alternatives, /etc/alternatives/gcc points to the higher priority program.

If you don't have any specific reason, I would also recommend to upgrade to a newer ubuntu version, so that the default gcc is a newer one.

I read on the gcc website that version 9.4 is more up-to-date than some 10.x versions.

With newer gcc versions, new features are added. Support for newer c/c++ standards are also added. Eg. You can read the changes for gcc-10 here. But people still need gcc-9 because some programs only build with gcc-9. So, GNU maintains gcc-9 (and much older versions) for a long time. Bugs are fixed, and newer releases are made. This can happen after the release of a newer gcc version. So, it is very much possible that a version of gcc-9 is newer than a version of gcc-10.