At present, app-text/texlive-2015 depends on >=dev-tex/cjk-latex-4.8.3-r1. However, it also (indirectly - see e.g. app-text/texlive-core-2015) depends on >=dev-libs/kpathsea-6.2.1. Attempting to emerge dev-tex/cjk-latex-4.8.3-r1 against dev-libs/kpathsea-6.2.1_p20150521-r1 fails at configure time because the configure scripts looks for the header file c-auto.h, no longer present in that version of kpathsea. In light of the above, app-text/texlive-2015 should depend on >=dev-tex/cjk-latex-4.8.4.
makes sense, thanks commit bb64aa9897ee350484991d9e6f241fa330179e63 Author: Alexis Ballier <aballier@gentoo.org> Date: Tue Nov 29 13:22:20 2016 +0100 app-text/texlive: bump cjk-latex dep, bug #599966