How to change the default GCC compiler in Ubuntu

Question

I have installed gcc-3 3 g  -3 3 on ubuntu 11 04 which already has gcc g  -4 4  So in my system both gcc-3 3 and 4 4 are available  I am able to call both compilers as I want  If I just call the command gcc then gcc-4 4 will get called  To call gcc-3 3  I have to use the command gcc-3 3    How can I change the default compiler as gcc-3 3  When I execute the command gcc it should call the gcc-3 3 and not gcc-4 4   In addition  how can I change the variable CXX in a make file to gcc-3 3  I wish to change one common global place in the system instead of changing all make files

User · Answer

In case you want a quicker  but still very clean  way of achieving it for a personal purpose  for instance if you want to build a specific project having some strong requirements concerning the version of the compiler   just follow the following steps    type echo  PATH and look for a personal directory having a very high priority  in my case  I have    local bin   add the symbolic links in this directory    For instance   ln -s  usr bin gcc-WHATEVER    local bin gcc ln -s  usr bin g  -WHATEVER    local bin g     Of course  this will work for a single user  it isn t a system wide solution   but on the other hand I don t like to change too many things in my installation

User · Answer

Now  there is gcc-4 9 available for Ubuntu precise   Create a group of compiler alternatives where the distro compiler has a higher priority   root  VER 4 6   PRIO 60 root  update-alternatives --install  usr bin gcc gcc  usr bin gcc- VER  PRIO --slave  usr bin g   g    usr bin g  - VER root  update-alternatives --install  usr bin cpp cpp-bin  usr bin cpp- VER  PRIO  root  VER 4 9   PRIO 40 root  update-alternatives --install  usr bin gcc gcc  usr bin gcc- VER  PRIO --slave  usr bin g   g    usr bin g  - VER root  update-alternatives --install  usr bin cpp cpp-bin  usr bin cpp- VER  PRIO   NOTE  g   version is changed automatically with a gcc version switch  cpp-bin has to be done separately as there exists a  cpp  master alternative   List available compiler alternatives   root  update-alternatives --list gcc root  update-alternatives --list cpp-bin   To select manually version 4 9 of gcc  g   and cpp  do   root  update-alternatives --config gcc root  update-alternatives --config cpp-bin   Check compiler versions   root  for i in gcc g   cpp   do  i --version   done   Restore distro compiler settings  here  back to v4 6    root  update-alternatives --auto gcc root  update-alternatives --auto cpp-bin

User · Answer

This is the great description and step-by-step instruction how to create and manage master and slave  gcc and g    alternatives   Shortly it s   sudo update-alternatives --install  usr bin gcc gcc  usr bin gcc-4 6 60 --slave  usr bin g   g    usr bin g  -4 6 sudo update-alternatives --install  usr bin gcc gcc  usr bin gcc-4 7 40 --slave  usr bin g   g    usr bin g  -4 7 sudo update-alternatives --config gcc

User · Answer

I found this problem while trying to install a new clang compiler  Turns out that both the Debian and the LLVM maintainers agree that the alternatives system should be used for alternatives  NOT for versioning    The solution they propose is something like this  PATH  usr lib llvm-3 7 bin  PATH where  usr lib llvm-3 7 bin is a directory that got created by the llvm-3 7 package  and which contains all the tools with their non-suffixed names  With that  llvm-config  version 3 7  appears with its plain name in your PATH  No need to muck around with symlinks  nor to call the llvm-config-3 7 that got installed in  usr bin   Also  check for a package named llvm-defaults  or gcc-defaults   which might offer other way to do this  I didn t use it

User · Answer

Between 4 8 and 6 with all --slaves   update-alternatives --install  usr bin gcc gcc  usr bin gcc-4 8                       10                       --slave    usr bin cc cc  usr bin gcc-4 8                       --slave    usr bin c   c    usr bin g  -4 8                       --slave    usr bin g   g    usr bin g  -4 8                       --slave    usr bin gcov gcov  usr bin gcov-4 8                       --slave    usr bin gcov-dump gcov-dump  usr bin gcov-dump-4 8                       --slave    usr bin gcov-tool gcov-tool  usr bin gcov-tool-4 8                       --slave    usr bin gcc-ar gcc-ar  usr bin gcc-ar-4 8                       --slave    usr bin gcc-nm gcc-nm  usr bin gcc-nm-4 8                       --slave    usr bin gcc-ranlib gcc-ranlib  usr bin gcc-ranlib-4 8   and  update-alternatives --install  usr bin gcc gcc  usr bin gcc-6                       15                       --slave    usr bin cc cc  usr bin gcc-6                       --slave    usr bin c   c    usr bin g  -6                       --slave    usr bin g   g    usr bin g  -6                       --slave    usr bin gcov gcov  usr bin gcov-6                       --slave    usr bin gcov-dump gcov-dump  usr bin gcov-dump-6                       --slave    usr bin gcov-tool gcov-tool  usr bin gcov-tool-6                       --slave    usr bin gcc-ar gcc-ar  usr bin gcc-ar-6                       --slave    usr bin gcc-nm gcc-nm  usr bin gcc-nm-6                       --slave    usr bin gcc-ranlib gcc-ranlib  usr bin gcc-ranlib-6   Change between them with update-alternatives --config gcc

User · Answer

As  Tommy suggested  you should use update-alternatives  It assigns values to every software of a family  so that it defines the order in which the applications will be called     It is used to maintain different versions of the same software on a system  In your case  you will be able to use several declinations of gcc  and one will be favoured   To figure out the current priorities of gcc  type in the command pointed out by  tripleee s comment   update-alternatives --query gcc   Now  note the priority attributed to gcc-4 4 because you ll need to give a higher one to gcc-3 3  To set your alternatives  you should have something like this  assuming your gcc installation is located at  usr bin gcc-3 3  and gcc-4 4 s priority is less than 50    update-alternatives --install  usr bin gcc gcc  usr bin gcc-3 3 50   --edit--  Finally  you can also use the interactive interface of update-alternatives to easily switch between versions  Type update-alternatives --config gcc to be asked to choose the gcc version you want to use among those installed   --edit 2 --  Now  to fix the CXX environment variable systemwide  you need to put the line indicated by  DipSwitch s in your  bashrc file  this will apply the change only for your user  which is safer in my opinion    echo  export CXX  usr bin gcc-3 3   gt  gt     bashrc

User · Answer

Here s a complete example of jHackTheRipper s answer for the TL DR crowd   -  In this case  I wanted to run g  -4 5 on an Ubuntu system that defaults to 4 6  As root   apt-get install g  -4 5 update-alternatives --install  usr bin g   g    usr bin g  -4 6 100 update-alternatives --install  usr bin g   g    usr bin g  -4 5 50 update-alternatives --install  usr bin gcc gcc  usr bin gcc-4 6 100 update-alternatives --install  usr bin gcc gcc  usr bin gcc-4 5 50 update-alternatives --install  usr bin cpp cpp-bin  usr bin cpp-4 6 100 update-alternatives --install  usr bin cpp cpp-bin  usr bin cpp-4 5 50 update-alternatives --set g    usr bin g  -4 5 update-alternatives --set gcc  usr bin gcc-4 5 update-alternatives --set cpp-bin  usr bin cpp-4 5   Here  4 6 is still the default  aka  auto mode    but I explicitly switch to 4 5 temporarily  manual mode   To go back to 4 6   update-alternatives --auto g   update-alternatives --auto gcc update-alternatives --auto cpp-bin    Note the use of cpp-bin instead of just cpp  Ubuntu already has a cpp alternative with a master link of  lib cpp  Renaming that link would remove the  lib cpp link  which could break scripts

User · Answer

I used just the lines below and it worked  I just wanted to compile VirtualBox and VMWare WorkStation using kernel 4 8 10 on Ubuntu 14 04  Initially  most things were not working for example graphics and networking  I was lucky that VMWare workstation requested for gcc 6 2 0  I couldn t start my Genymotion Android emulators because virtualbox was down  Will post results later if necessary   VER 4 6   PRIO 60 sudo update-alternatives --install  usr bin gcc gcc  usr bin gcc- VER  PRIO --slave  usr bin g   g    usr bin g  - VER VER 6   PRIO 50 sudo update-alternatives --install  usr bin gcc gcc  usr bin gcc- VER  PRIO --slave  usr bin g   g    usr bin g  - VER VER 4 8   PRIO 40 sudo update-alternatives --install  usr bin gcc gcc  usr bin gcc- VER  PRIO --slave  usr bin g   g    usr bin g  - VER

[linux] How to change the default GCC compiler in Ubuntu?

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