OS X 10.5 Macbook Pro (Intel Dual Core x86) Boost builds and installs fine (except for Unicode Regex) and recognizes the toolset is Darwin. $./configure -n Building Boost.Jam with toolset darwin... tools/jam/src/bin.macosxx86/bjam -n Detecting Python version... 2.5 -n Detecting Python root... /Library/Frameworks/Python.framework/Versions/2.5 -n Unicode/ICU support for Boost.Regex?... not found. Backing up existing Boost.Build configuration in user-config.jam.4 Generating Boost.Build configuration in user-config.jam... Generating Makefile... and make and install proceeded fine. So I tried the examples on the "Getting Started Page" First one works fine. Second one (using the regex libraries does not): "ld: warning in /usr/local/lib/libboost_regex-mt-d.a, file is not of required architecture Undefined symbols: "boost::match_results<__gnu_cxx::__normal_iterator<char const*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<boost::sub_match<__gnu_cxx::__normal_iterator<char const*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >

::maybe_assign(boost::match_results<__gnu_cxx::__normal_iterator<char const*, std::basic_string<char, std::char_traits<char>, std::allocator<char>

...

, std::allocator<boost::sub_match<__gnu_cxx::__normal_iterator<char const*, std::basic_string<char, std::char_traits<char>, std::allocator<char>

...

...

...

const&)", referenced from: boost::re_detail::perl_matcher<__gnu_cxx::__normal_iterator<char const*, std::basic_string<cha"

So how can this be? The build was for Darwin and yet its the wrong architecture?!?!?! I don't understand the error messages frankly.