When configuring bison-3.0.4-r1, it dies in trying to apply the optional-perl.patch with older versions of patch. Presumably because it is in a git-compatible format that older versions of patch didn't know. Requiring a newer patch fixes this problem properly. Reproducible: Always
I've run ebuild bison-3.0.4-r1 using patch-2.7.{3,4,5} and all of them work correctly for me. Could you provide a log showing the failure, the output of emerge --info, and state which patch utility version you are using?
Closing as invalid: - no patch version provided ...and probably obsolete given that we now have only >=patch-2.7.5 in repository.