The GCC/glibc update on the desktop system did eventually finish. At each point it had stopped, I noted what it failed on so I could go back later. Once I fixed the dependency that was causing everything to fail, I could re-emerge those packages that failed first time around.
In case you’re curious, the reason for the failure seems to be that emerge of your system and/or world trees doesn’t seem to handle slotted packages (in Gentoo, packages that can have more than one version installed at once, like the kernel source, GCC and others, are called slotted; each different version installs into a different ‘slot’ and can be managed differently). GTK+ is slotted, and to satisfy dependencies for various packages I had both version 1 and 2 installed in different slots. The emerge world only seemed to pick up one of them (version 1 by the look), so packages dependent on gtk+-2 were failing.
I’ve started doing the GCC/glibc update on a virtual server system I have. Looks like it’s having similar problems, although I think it’s because I’m trying to switch to the new “server” profile from 2006.1 when I had already installed packages from the general profile.
Crossed Wires 