id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
11517	unused.hpp does not compile with g++ (<= 4.6) and -std=gnu++0x	Ben Goodrich <goodrich.ben@…>	Joel de Guzman	"To reproduce, try to execute
{{{
g++-4.6 -std=gnu++0x -I. -o /tmp/unused.gch boost/fusion/support/unused.hpp
}}}
I obtain
{{{
boost/fusion/support/unused.hpp: In member function ‘const boost::fusion::unused_type& boost::fusion::unused_type::operator=(const boost::fusion::unused_type&) const’:
boost/fusion/support/unused.hpp:57:9: error: ‘this’ is not a potential constant expression
boost/fusion/support/unused.hpp: At global scope:
boost/fusion/support/unused.hpp:67:39: error: both ‘const’ and ‘constexpr’ cannot be used here
}}}

Such code later became acceptable to g++ but they did not backport the fix beyond 4.7.x ( [https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54086] ). I am able to work around this problem by adding some lines like
{{{
#if defined(__GXX_EXPERIMENTAL_CXX0X__) && __GNUC__  == 4 && __GNUC_MINOR__ <= 6
}}}
in the attached file but you probably want a better fix."	Bugs	closed	Boost 1.59.0	fusion	Boost 1.58.0	Problem	fixed