I just updated dev-libs/expat-2.0.0 with emerge -D world yesterday. I couldn't finish the update and some programs didn't work. They couldn't find libexpat.so.0.
I restored a backup and updated manually dev-libs/expat-2.0.0, It doesn't include libexpat.so.0 removed with previous version.
*** This bug has been marked as a duplicate of 128069 ***