Hi Im getting this error when compiling several tool sets on the same command line. Best, Vicente ./b2 toolset=clang-3.2xl,darwin-4.8.1x -l 300 -j6 modularized layout build Building the Boost C++ Libraries. Performing configuration checks - symlinks supported : yes - hardlinks supported : yes - 32-bit : no - 64-bit : yes - arm : no - mips1 : no - power : no - sparc : no - x86 : yes - has_icu builds : no warning: Graph library does not contain MPI-based parallel components. note: to enable them, add "using mpi ;" to your user-config.jam - zlib : yes - iconv (libc) : no - iconv (separate) : yes - icu : no - icu (lib64) : no - compiler-supports-ssse3 : yes - lockfree boost::atomic_flag : yes - compiler-supports-avx2 : yes - gcc visibility : yes - long double support : yes warning: skipping optional Message Passing Interface (MPI) library. note: to enable MPI support, add "using mpi ;" to user-config.jam. note: to suppress this message, pass "--without-mpi" to bjam. note: otherwise, you can safely ignore this message. - zlib : yes - 32-bit : no - 64-bit : yes - arm : no - mips1 : no - power : no - sparc : no - x86 : yes - has_icu builds : no - zlib : yes - iconv (libc) : no - iconv (separate) : yes - icu : no - icu (lib64) : no - compiler-supports-ssse3 : no - compiler-supports-avx2 : no - lockfree boost::atomic_flag : yes - gcc visibility : yes - long double support : yes - zlib : yes /Users/viboes/github/modular-boost/tools/build/v2/build/virtual-target.jam:1099: in virtual-target.register-actual-name from module virtual-target error: Duplicate name of actual target: <pstage/lib>libboost_atomic.dylib error: previous virtual target { clang-darwin%clang-darwin.link.dll-libboost_atomic.dylib.SHARED_LIB { clang-darwin%clang-darwin.compile.c++-lockpool.o.OBJ { lockpool.cpp.CPP } } } error: created from libs/atomic/build/boost_atomic error: another virtual target { darwin%darwin.link.dll-libboost_atomic.dylib.SHARED_LIB { darwin%darwin.compile.c++-lockpool.o.OBJ { lockpool.cpp.CPP } } } error: created from libs/atomic/build/boost_atomic error: added properties: <toolset-darwin:version>4.8.1x <toolset>darwin error: removed properties: <toolset-clang:platform>darwin <toolset-clang:version>3.2xl <toolset>clang /Users/viboes/github/modular-boost/tools/build/v2/build/virtual-target.jam:484: in actualize-no-scanner from module object(file-target)@16688 /Users/viboes/github/modular-boost/tools/build/v2/build/virtual-target.jam:134: in class@virtual-target.actualize from module object(file-target)@16688 /Users/viboes/github/modular-boost/tools/build/v2/build-system.jam:720: in load from module build-system /Users/viboes/github/modular-boost/tools/build/v2/kernel/modules.jam:289: in import from module modules /Users/viboes/github/modular-boost/tools/build/v2/kernel/bootstrap.jam:139: in boost-build from module /Users/viboes/github/modular-boost/boost-build.jam:17: in module scope from module