Hi, I'd like to point out that bcp namespace aliasing has been broken for quite a while, which impacts package providers of Boost which choose to package it with a versioned namespace. We should try to fix to enable more people to upgrade. The bug has been reported March 2018 on trac https://svn.boost.org/trac10/ticket/13460 Then again by me this week on github https://github.com/boostorg/bcp/issues/4 Things have been made worse since 1.69 because libraries now build with visibility hidden by default, which means that with this bug symbols don't get exported and nothing links. Also I would argue that this set-up should be tested as part of the release validation process. The boost build system is arcane enough that we don't need a pretty standard build configuration to be subtly broken for more than a year. Could we try to address this before 1.71?