How to use multiple instances of gcc?

I have both gcc 4.7.3 and 4.8.1 installed

But on running gcc --version I get

gcc (Ubuntu/Linaro 4.7.3-1ubuntu1) 4.7.3
Copyright (C) 2012 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.

I am an Ubuntu newbie and I don't know much about updating symbolic-links...

I searched the Internet, and found out about update-alternatives but was reluctant to use it...

Please can someone help me in choosing 4.8 over 4.7 & also tell me is it bad to have 2 versions of same gcc?

Solution 1:

You need to let update-alternatives to know that you have 2 C/C++ compilers, create a record for each one, and then configure which one you want to use. This is done with the following:

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.7 60 --slave /usr/bin/g++ g++ /usr/bin/g++-4.7
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 40 --slave /usr/bin/g++ g++ /usr/bin/g++-4.8
sudo update-alternatives --config gcc

From this point forward, the only thing required when switching compilers is this command:

sudo update-alternatives --config gcc

Source: http://charette.no-ip.com:81/programming/2011-12-24_GCCv47/.