As part of a large upgrade, expat was upgraded from 1.5.2 to 2.0.1.
Following this, all futher builds failed. Bug #128069 http://bugs.gentoo.org/show_bug.cgi?id=128069 documents this problem and describes the resolution as using revdep-rebuild.
However, on running "revdep-rebuild -X", the first ebuild failed, still looking for libexpat.so.0 (the original problem).
My machine is an AMD64 machine (I don't know if this is related).
I was able to get things running again by creating a link libexpat.so.0 (pointing to libexpat.so) and now all I have "revdep-rebuild --library=/usr/lib64/libexpat.so.0" successfully running.
But why did "revdep-rebuild -X" not work?
Steps to Reproduce:
1. Build a system with expat-1.5.2, Gnome 2.16
2. emerge -uD world (this fails)
3. revdep-rebuild -X to try to fix failed builds
Builds scheduled by revdep-rebuild failed due to lack of libexpat.so.0
Should have found an order to successfully rebuild the necessary packages.
Any revdep-rebuild bug requires all /root/.revdep-rebuild* files attached, as well as the console output and emerge --info. If you are using portage-184.108.40.206, you should either downgrade to 220.127.116.11 or upgrade to 18.104.22.168.
I deleted the files before submitting the bug report, so let's close it.