I don't know if this is considered "wrong," but it is certainly annoying. The three unused variable warnings below were repeated 38 times in my build of Boost 1.59.0 rc2. They were also in rc1 and in 1.58.0.

./boost/system/error_code.hpp: At global scope:
./boost/system/error_code.hpp:221:36: warning: 'boost::system::posix_category' defined but not used [-Wunused-variable]
     static const error_category & posix_category = generic_category();
                                    ^
./boost/system/error_code.hpp:222:36: warning: 'boost::system::errno_ecat' defined but not used [-Wunused-variable]
     static const error_category & errno_ecat     = generic_category();
                                    ^
./boost/system/error_code.hpp:223:36: warning: 'boost::system::native_ecat' defined but not used [-Wunused-variable]
     static const error_category & native_ecat    = system_category();

-------- Forwarded Message --------

Subject:	Re: [Boost-users] 1.59.0 rc2 is now available
Date:	Fri, 7 Aug 2015 21:19:28 -0500
From:	Merrill Cornish <merrill.cornish@earthlink.net>
To:	boost-users@lists.boost.org

Clean compile of 1.59.0.rc2 using Windows 7.1, 64-bit, MinGW 5.1, 
64-bit, built as C++ 2014.

Command line:  \bin\b2.exe --prefix=d:\boost_1_59_0_b2 
--build-type=complete --without-mpi cxxflags="-std=c++14" -a 
toolset=gcc  stage >d:\bin\build.log 2>&1  My project compiles without 
error and all tests run without error.