dev-libs/sexp-0.8.3 breaks stable(!) dev-util/librnp-0.17.0-r1. Works with dev-libs/sexp-0.8.5. this is because 0.8.3 can not build shared libs.
Fixed with commits: 8c78dad436d473f1e379b91f430816df6a5b17d3, 857d72c5e138e85b1e757efa64905aae3ef8c8a8 and 297956943c373a8d15ce41ac5f850c90c8835e73 Thx Joonas!