https://svn.boost.org/trac10/ticket/13105 <p> This ticket is addressed by this pull request: <a class="ext-link" href="https://github.com/boostorg/function/pull/13/files"><span class="icon">​</span>https://github.com/boostorg/function/pull/13/files</a> </p> <p> The missing top level include guard means that even if boost/function.hpp is included in a pre-compiled header, we still pay the heavy boost pp pre-processing cost every time it is also included. </p> <p> This is very problematic with Visual Studio intellisense: It pre-process and parses the translation unit on the fly to provide syntax/semantic highlighting. </p> <p> In our projects, this fix remove a couple of seconds in this process. (boost/function.hpp is included in many headers that result in pre-processing it multiple time per compilation units) </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/13105 Trac 1.4.3