Tip: Fix GCC upgrade problems on Gentoo

Here's a typical problem on gcc upgrades:

configure:error: installation or configuration problem: C complier cannot create executables.

To solve the problem perform the following:

1. become superuser
2. gcc-config -l
   
3. gcc-config 1
4. source /etc/profile

Step 2 lists the available gcc versions. On step 3 select one from the list by number or typing the full name (in my case I only had one available).

Problem fixed. Happy emerging ;)