Question

11

Downloaded g++ 4.8 from the PPA but can't set it as default?

rated 0 times [ 11] [ 0] / answers: 1 / hits: 24592 / 2 Years ago, mon, july 25, 2022, 7:23:13

I have downloaded g++ 4.8 on Ubuntu 12.10 by doing:

sudo add-apt-repository ppa:ubuntu-toolchain-r/test

sudo apt-get update

sudo apt-get install g++-4.8

but when I do:

sudo update-alternatives --config g++

to switch g++ versions it says:

update-alternatives: error: no alternatives for g++.

However if I do:

g++ --version

it says:

g++ (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3

Copyright (C) 2011 Free Software Foundation, Inc.

This is free software; see the source for copying conditions.  There is NO

warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

How do I set my g++ 4.8 installation to be the default g++?

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issfullus

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answered 2 Years ago iriousutur · Accepted Answer

First of all, you must discover where are your 4.8 binaries of all the tools:

$ which gcc-4.8

/usr/bin/gcc-4.8

$ which g++-4.8

/usr/bin/g++-4.8

$ ls /usr/bin/*-4.8

/usr/bin/cpp-4.8         /usr/bin/x86_64-linux-gnu-cpp-4.8

/usr/bin/g++-4.8         /usr/bin/x86_64-linux-gnu-g++-4.8

/usr/bin/gcc-4.8         /usr/bin/x86_64-linux-gnu-gcc-4.8

/usr/bin/gcc-ar-4.8      /usr/bin/x86_64-linux-gnu-gcc-ar-4.8

/usr/bin/gcc-nm-4.8      /usr/bin/x86_64-linux-gnu-gcc-nm-4.8

/usr/bin/gcc-ranlib-4.8  /usr/bin/x86_64-linux-gnu-gcc-ranlib-4.8

/usr/bin/gcov-4.8

So, we have all our binaries, now lets see if some symlinks are available for such binaries:

$ cd /usr/bin

$ ls -l gcc* cpp g++

lrwxrwxrwx 1 root root      7 sep 18 14:02 cpp -> cpp-4.7

lrwxrwxrwx 1 root root      7 abr 22  2013 g++ -> g++-4.7

lrwxrwxrwx 1 root root      7 sep 18 14:02 gcc -> gcc-4.7

As we can see, only cpp, g++ and gcc has symbolic links. We have two options here.

Symlinking

We replace the symlinks with ours, removing the actuals first:

sudo rm /usr/bin/cpp /usr/bin/gcc /usr/bin/g++

Then creating ours

sudo ln -s /usr/bin/cpp-4.8 /usr/bin/cpp

sudo ln -s /usr/bin/gcc-4.8 /usr/bin/gcc

sudo ln -s /usr/bin/g++-4.8 /usr/bin/g++

To revert it back use the same commands but with 4.7 or 4.6 instead

sudo rm /usr/bin/cpp /usr/bin/gcc /usr/bin/g++

sudo ln -s /usr/bin/cpp-4.7 /usr/bin/cpp

sudo ln -s /usr/bin/gcc-4.7 /usr/bin/gcc

sudo ln -s /usr/bin/g++-4.7 /usr/bin/g++