sci-electronics/pcb had recently released version 4.0.0 with "quite a lot of bugs (..) fixed and new features added" (a quote from release notes), but the version in tree is still 20140316. Please bump.
I tried simply using the existing pcb-20140316-r1 ebuild and hacking in the 4.0.0 version into it and it seems to be able to at least build and run on amd64. I have not fully tested this program yet, however; this will be a little while until I can see if I can replicate the issue I've been seeing in pcb-20140316-r1...
As of 2017-09-23, pcb-4.0.2 is available. Aggregated changelog is available[0]. 0: http://pcb.geda-project.org/news.html
pcb-4.0.2 in tree. Thanks for reporting. > sci-electronics/pcb: Version bump (Bug #610694)