I just wanted to share the first GCC 4.x compilation able to build Code::Blocks (with minor changes in the source I hope be fixed in SVN soon).
The link is in my signature and some info is shown there to get it working.
I say it's the first 'cause many times I tried (since GCC 4.0.0 came out) compiling GCC and then building a wxWidgets app and it always died with an ICE (Internal Compiler Error).
This version is really strict so you'll surely get lots of warnings when compiling, mainly from wxWidgets apps
It only includes C and C++ languages.
Enjoy it!