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Yet Another Command Line Experiments.

Handling the GNU Compiler Collection with debian alternatives

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The story so far: I have several versions of gcc and g++ on my debian distro and during some external project compilation I went to version-related compilation issues. OK, gcc should be managed by the alternatives debian stuff…

Just after a $ sudo update-alternative --config gcc[tab][tab], I discovered that gcc, g++, gcov, etc. are NOT managed the alternatives way… OK, there are some alternatives defined for c++, cc and cpp, but these alternatives are symbolic links to… symbolic links:

foo@bar:/etc/alternatives$ ls -al c++ cc cpp
lrwxrwxrwx 1 root root 12  2 avril  2011 c++ -> /usr/bin/g++
lrwxrwxrwx 1 root root 12  2 avril  2011 cc -> /usr/bin/gcc
lrwxrwxrwx 1 root root 12  1 août  23:41 cpp -> /usr/bin/cpp
foo@bar:/etc/alternatives$ ls -al /usr/bin/g++ /usr/bin/gcc /usr/bin/cpp
lrwxrwxrwx 1 root root 7  1 août  23:32 /usr/bin/cpp -> cpp-4.6
lrwxrwxrwx 1 root root 7  9 juil. 19:39 /usr/bin/g++ -> g++-4.6
lrwxrwxrwx 1 root root 7  9 juil. 19:39 /usr/bin/gcc -> gcc-4.6

It’s really really strange since c++ and cc are generic but not cpp. Here is my proposal to have a better management for cpp, gcc, g++ and gcov, assuming that you have 4.4 and 4.6 versions on your system:

foo@bar:/etc/alternatives$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.6 10
foo@bar:/etc/alternatives$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.4 1
foo@bar:/etc/alternatives$ sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.6 10
foo@bar:/etc/alternatives$ sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.4 1
foo@bar:/etc/alternatives$ sudo update-alternatives --install /usr/bin/gcov gcov /usr/bin/gcov-4.6 10
foo@bar:/etc/alternatives$ sudo update-alternatives --install /usr/bin/gcov gcov /usr/bin/gcov-4.4 1
foo@bar:/etc/alternatives$ sudo rm /usr/bin/cpp
foo@bar:/etc/alternatives$ sudo update-alternatives --install /usr/bin/cpp cpp /usr/bin/cpp-4.6 10
foo@bar:/etc/alternatives$ sudo update-alternatives --install /usr/bin/cpp cpp /usr/bin/cpp-4.4 1

Obviously, you should adapt the previous commands to your system (i.e. which versions are present).

Now, when you need gcc-4.4 for a specific compilation and if $ export CC=/usr/bin/gcc-4.4 is not sufficient, you just have to do $ sudo update-alternative --config gcc and manually select gcc-4.4… to reset to gcc-4.6 if you nominally need it.

That’s it!

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