gcc-4.6.0 made Boost.foreach unusable in 1.46.1 because the rvalue detection no longer works. Now, there is a fix in trunk for it but it has a nasty side effect, namely a warning that is emitted whenever foreach is used with an rvalue and -Wconversion is turned on. Sadly, this warning cannot be ignored by including Boost with -isystem because the code is generated by a macro, obviously. Here is a simple program to reprdouce this: #include <boost/foreach.hpp> #include <iostream> #include <ostream> #include <vector> typedef std::vector< int

int_vector;

int_vector const test() { int_vector ret(2, 2); return ret; } int main() { BOOST_FOREACH( int_vector::const_reference ref, test() ) std::cout << ref << '\n'; } This prints the following warning: test.cpp:21:2: warning: choosing ‘boost::foreach_detail_::rvalue_probe<T>::operator boost::foreach_detail_::rvalue_probe<T>::value_type() [with T = const std::vector<int>, boost::foreach_detail_::rvalue_probe<T>::value_type = const std::vector<int>]’ over ‘boost::foreach_detail_::rvalue_probe<T>::operator T&() const [with T = const std::vector<int>]’ [-Wconversion] test.cpp:21:2: warning: for conversion from ‘boost::foreach_detail_::rvalue_probe<const std::vector<int> >’ to ‘const int_vector’ [-Wconversion] test.cpp:21:2: note: because conversion sequence for the argument is better I would be glad if this could be fixed somehow because -Wconversion is a crucial warning option to me.