Installing gcc on MAC OS

Download MacPorts. There are available images for Lion and Snow Leopard.

The you should want to update your MacPorts using the commands:

sudo port selfupdate
sudo port upgrade outdated

NOTE: FOR GRAPHLAB, PLEASE USE gcc45 and not gcc46 as in the below
example.

Then you can install gcc using

sudo port install gcc46      #change this to gcc45 for graphlab

You can view other versions of gcc using the command

port search gcc

After installation you can view installed file by

port contents gcc46        #change this to gcc45 for graphlab

Now if you have several gcc versions installed you may want to choose the right version to use.
This is done using the command:

sudo port select gcc mp-gcc46

Now I got some error:
Selecting 'mp-gcc46' for 'gcc' failed: could not create a new link for "/opt/local/bin/gcj'. It seems it is a known issue discussed here.
I applied a quick and dirty fix (Since I don't need gcc Java:)

sudo touch /opt/local/bin/gcj-mp-4.6

And then I get:
Selecting 'mp-gcc46' for 'gcc' succeeded. 'mp-gcc46' is now active.