I've been abusing compressed_pair to build a compressed_tuple. I'm pretty sure this bug can be fixed using intermediate types on the hierarchy. struct Empty1{}; struct Empty2{}; int i=sizeof( boost::compressed_pair >); //boom int j=sizeof( boost::compressed_pair); //ok int k=sizeof( boost::compressed_pair); //ok int h=sizeof( boost::compressed_pair >); //ok cc1plus: warnings being treated as errors In file included from ..../boost/boost_1_50_0/include/boost/compressed_pair.hpp:21, from /home/w461845/src/edgamm/src/lib/libLogger/include/libLogger/LogChain.hpp:4, from OLogTest.cpp:1: ..../boost/boost_1_50_0/include/boost/detail/compressed_pair.hpp: In instantiation of "boost::details::compressed_pair_imp, 3>": ..../boost/boost_1_50_0/include/boost/detail/compressed_pair.hpp:348: instantiated from "boost::compressed_pair >" OLogTest.cpp:112: instantiated from here ..../boost/boost_1_50_0/include/boost/detail/compressed_pair.hpp:73: error: direct base "Empty1" inaccessible in "boost::details::compressed_pair_imp, 3>" due to ambiguity g++ (GCC) 4.4.7 20120313 (Red Hat 4.4.7-4) Chris Hite This email is confidential and subject to important disclaimers and conditions including on offers for the purchase or sale of securities, accuracy and completeness of information, viruses, confidentiality, legal privilege, and legal entity disclaimers, available at http://www.jpmorgan.com/pages/disclosures/email.