This package contains .ph files that are mostly generated by the perl h2ph command by inspecting existing .h files on your system. Due to the nature of these files, they are likely to be incomplete, and many of them may not even load in Perl, and many things that rely on C intrinsics like "sizeof" or macro expansion may be very broken. It is strongly recommended you build this package with: USE="debug sizeof-warning" As this will give better context when things break, and will at least notify you when some constant relies on a missing "sizeof" entry ( and where ). Missing "sizeof" entries and broken constants need a lot of love, so please file bugs at https://github.com/gentoo-perl/perl-headers/issues ( or on gentoo bugzilla ) if you find anything that you know how to fix. However, the logic is kinda broken in a lot of places, and there's not a lot that can be done about it as we're reliant on the vernerable quality of h2ph, and this package is provided mostly as a kindness to people who need it, and were already relying on the equivalent logic that we shipped with perl itself prior to 5.24 ( where it was horribly broken and nobody really noticed )