Gentoo's Bugzilla –
Attachment 388970 Details for
Bug 528768=net-libs/libhubbub-0.3.0 - In file included from src/treebuilder/treebuilder.c:8: /usr/include/features.h:148:3: error: #warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE" [-Werror=cpp]