GCC errors on Gentoo

I was trying to update my computer the other day and was getting an error about not being able to update because my version of gcc was too old.

I looked to portage and emerge showed I had merged gcc 3.7.3 but still the error persisted... a quick bit of googling showed you can set the system gcc using the command

Basically, you list the versions available with the -l switch, then set your chosen version like this:
#gcc-config -l
#gcc-config 4
Then I think you should emerge a lot of your programs again, however all I did was run an update:
#emerge -uaqDvN world