As I always like to be on the bleeding edge, I recently rebuilt my complete Gentoo system with the new gcc 4.0.0.
The good news is that it's getting better every day, but you still need a lot of fixes, so if you decide to try it, please be prepared that you'll have to play around, apply patches etc.
- To bootstrap your system with gcc 4, you need to add sys-devel/gcc and sys-libs/glibc to your package.unmask and package.keywords, because they are hard-masked in package.mask and have KEYWORDS="-*". I always have ACCEPT_KEYWORDS="~x86" set in make.conf to get the latest testing-packages, this is probably advisable if you want to try out such bleeding edge stuff.
- xorg-x11 fails, but a patch is in the masked xorg-x11-6.8.2-r2 ebuild, so add that to package.unmask, too.
- A number of packages failed to compile that are now fixed in portage, so you don't have to care about (xfsprogs, mod_php-5, probably some more I forgot).
- libsdl needs to be compiled with -O0, see this bug for details.
- Konqueror compiles, but segfaults, a fix/patch is here.
- Mozilla / Firefox don't compile, see here, but I didn't try/need, as Konqueror is my browser of choice.
- A bigger problem was the kernel, as 2.6.11.8 fails to compile and 2.6.12-rc3/rc4 brought a kernel panic while booting. I'm now running 2.6.12-rc3-mm3, it boots and mostly works, but acpi4asus seems to be broken (don't know if this is due to gcc4 or mm-kernel).
- Packages that still fail for me: gstreamer-ffmpeg, fte, tcpdump, dosemu, wine, openoffice-ximian. All upstream devs are informed, so I think patches will appear soon.
So finally, no really important packages are missing, my system works quite stable so far.
Feel free to try out yourself. If packages fail to build, try searching the gentoo-bugzilla and the upstream-webpage for fixes.
If you have patches/fixes for the packages above, feel free to add a link to the comments. If you wrote patches yourself, make sure to send them to the upstream-devs and to the gentoo bugzilla.
