2.0.17 too
Created attachment 171327 [details] paludis -i =dev-libs/libsigc++-2.0.18
Created attachment 171329 [details] paludis -I =dev-libs/libsigc++-2.0.18
Created attachment 172346 [details, diff] libsigc++-2.0.18-gcc43.patch
Created attachment 174334 [details] the working ebuild I added epatch to src_unpack().
And yes, patch solves the problem.
2.0.18 is no longer in the tree and 2.2.3 (current stable) looks to compile fine