With the latest snapshot builds of clang, thin LTO is supported on Windows. This thin LTO gives very interesting (speed) results. I would therefore like to start to build boost with clang and no longer with msvc. I have msvc 15.4 installed (the latest incarnation). I made a project-config.jam: =============start=============== import option ; using clang : 6.0 : clang++.exe : <cxxflags>-fmacro-backtrace-limit=0 <cxxflags>-Wno-invalid-token-paste <compileflags>-fmsc-version=1911 <linkflags>-fuse-ld=lld <linkflags>-flto=thin ; option.set keep-going : false ; ==============end=============== I call: bjam -a -d+2 cxxflags="-O0" "-sZLIB_SOURCE=%HOME%\zlib-1.2.8" "-sBZIP2_SOURCE=%HOME%\bzip2-1.0.6" variant=debug instruction-set=haswell threading=multi link=static runtime-link=static --prefix=%PREFIX% --build-dir=c:\boost-build address-model=64 architecture=x86 toolset=msvc --without-python --without-mpi --disable-filesystem2 install This does not work. What is the proper way to compile boost on windows using clang++.exe or clang-cl.exe for use with VS2017. degski -- "*Ihre sogenannte Religion wirkt bloß wie ein Opiat reizend, betäubend, Schmerzen aus Schwäche stillend.*" - Novalis 1798