boostorg/signals2 — pull request #8 by foutrelis (2014-11-06 07:56:24+00:00)
Title: Add missing include to signals2/trackable.hpp

boost::weak_ptr started being used in commit a0bf2d1 (Disconnect slots
associated with signals2::trackable immediately) but the matching header
wasn't included.

https://svn.boost.org/trac/boost/ticket/10100#comment:7