I have been building the Boost libraries with g++ for many years. Someone recommended trying Clang, so I downloaded 1.52.0 and built it first with g++ 4.5.1 on Fedora 14. Then I started a build with clang 3.3, and it is taking forever. I have not made any measurements, but it must be at least an order of magnitude slower than g++. The math library seems to take the longest, but maybe there are other slow-building libraries yet to come. Am I doing something wrong, or should I expect the clang build to be very slow? In myuser-config I have this: using clang : 3.3 : /directory_where_we_installed_clang/bin/clang :<compileflags>"-fPIC"<linkflags>"-fPIC" ; The command line is this: bin/bjam --user-config=myuser-config threading=multi instruction-set=core2 address-model=64 variant=release link=static,shared --stagedir=stageF14C clean The clang version is: clang version 3.3 (trunk 169541) (llvm/trunk 169537) The OS is Linux Fedora 14. -- Dick Hadsell 203-992-6320 Fax: 203-992-6001 Reply-to: hadsell@blueskystudios.com Blue Sky Studios http://www.blueskystudios.com 1 American Lane, Greenwich, CT 06831-2560