I have installed the shiny new Clang at c:\llvm\ with MS Visual Studio 2015 update 3 I have added Clang to my user-config.jam thus using clang ; or in full detail: using clang : # version 4.0.0 : # location Clang compiler .exe location. # from http://llvm.org/releases/download.html dated 9Mar2017 c:\\LLVM\\bin\\clang++.exe : # options <warnings>on <cxxflags>-v ; and tried to invoke it thus I:\modular-boost\libs\hello_boost\example>b2 toolset=clang-4.0.0 -d2 --debug-configuration > clang40_24Mar17.log (.log file attached in case that helps). It starts well but comes to a terminal halt missing cstddef in boost/config/select_stdlib_config.hpp clang version 4.0.0 (tags/RELEASE_400/final) Target: x86_64-pc-windows-msvc Thread model: posix InstalledDir: c:\LLVM\bin "c:\\LLVM\\bin\\clang++.exe" -cc1 -triple x86_64-pc-windows-msvc19.0.24123 -emit-obj -mrelax-all -mincremental-linker-compatible -disable-free -main-file-name hello_boost.cpp -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -momit-leaf-frame-pointer -v -dwarf-column-info -debug-info-kind=limited -dwarf-version=4 -debugger-tuning=gdb -coverage-notes-file "I:\\modular-boost\\libs\\hello_boost\\example\\..\\..\\..\\bin.v2\\libs\\hello_boost\\example\\hello_boost.test\\clang-linux-4.0.0\ \debug\\hello_boost.gcno" -resource-dir "c:\\LLVM\\bin\\..\\lib\\clang\\4.0.0" -D BOOST_ALL_NO_LIB=1 -I "..\\..\\.." -internal-isystem "c:\\LLVM\\bin\\..\\lib\\clang\\4.0.0\\include" -internal-isystem "C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.10586.0\\ucrt" -O0 -Wno-unused-local-typedef -Wno-dll-attribute-on-redeclaration -Wall -fdeprecated-macro -fdebug-compilation-dir "I:\\modular-boost\\libs\\hello_boost\\example" -ferror-limit 19 -fmessage-length 0 -fms-extensions -fms-compatibility -fms-compatibility-version=19.0.24123 -std=c++14 -fdelayed-template-parsing -fno-inline -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -o "..\\..\\..\\bin.v2\\libs\\hello_boost\\example\\hello_boost.test\\clang-linux-4.0.0\\debug\\hello_boost.obj" -x c++ hello_boost.cpp clang -cc1 version 4.0.0 based upon LLVM 4.0.0 default target x86_64-pc-windows-msvc #include "..." search starts here: #include <...> search starts here: ..\..\.. c:\LLVM\bin\..\lib\clang\4.0.0\include C:\Program Files (x86)\Windows Kits\10\Include\10.0.10586.0\ucrt End of search list. In file included from hello_boost.cpp:15: In file included from ..\..\..\boost/config.hpp:44: ..\..\..\boost/config/select_stdlib_config.hpp:18:12: fatal error: 'cstddef' file not found # include <cstddef> I have two versions of cstddef C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\cstddef exists and refers to other files. contains // cstddef standard header #pragma once #ifndef _CSTDDEF_ #define _CSTDDEF_ #include and another at C:\programfiles\mingw-w64\x86_64-6.3.0-win32-seh-rt_v5-rev1\mingw64\lib\gcc\x86_64-w64-mingw32\6.3.0\include\c++; My PATH has (amongst other items) C:\Programfiles\mingw-w64\x86_64-6.3.0-win32-seh-rt_v5-rev1\mingw64\bin; C:\programfiles\mingw-w64\x86_64-6.3.0-win32-seh-rt_v5-rev1\mingw64\lib\gcc\x86_64-w64-mingw32\6.3.0\include; C:\programfiles\mingw-w64\x86_64-6.3.0-win32-seh-rt_v5-rev1\mingw64\lib\gcc\x86_64-w64-mingw32\6.3.0\include\c++; C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include; Is this expected (rather than clang-msvc-14.0)? notice: will use 'clang++' for clang-linux, condition <toolset>clang-linux-4.0.0 Anyone can give a clue as to what I am doing wrong? Thanks Paul --- Paul A. Bristow Prizet Farmhouse Kendal UK LA8 8AB +44 (0) 1539 561830