Hello, currently the filesystem library doesn't compile on Tru64 5.1 using gcc-3.4.3 as the compiler. schoepf@area51:~/net/src/boost/boost-HEAD/tools/regression/build> bjam -sTOOLS=gcc ...found 752 targets... ...using 3 temp targets... ...updating 4 targets... ...using <@boost!libs!filesystem!build/libboost_filesystem.a/gcc/release>exception.o... gcc-C++-action ../../../bin/boost/libs/filesystem/build/libboost_filesystem.a/gcc/release/operations_posix_windows.o /net/users/schoepflin/src/boost/boost-HEAD/libs/filesystem/build/../src/operations_posix_windows.cpp:123:39: operator '&&' has no right operand set -e "g++" -c -Wall -ftemplate-depth-255 -DNDEBUG -DNDEBUG -O3 -finline-functions -Wno-inline -I"../../../bin/boost/libs/filesystem/build" -I"/net/users/schoepflin/src/boost/boost-HEAD" -I "/net/users/schoepflin/src/boost/boost-HEAD" -o "../../../bin/boost/libs/filesystem/build/libboost_filesystem.a/gcc/release/operations_posix_windows.o" "/net/users/schoepflin/src/boost/boost-HEAD/libs/filesystem/build/../src/operations_posix_windows.cpp" The code in question is: # if defined(_POSIX_THREAD_SAFE_FUNCTIONS) \ && defined(_SC_THREAD_SAFE_FUNCTIONS) \ && _POSIX_THREAD_SAFE_FUNCTIONS >= 0 if ( ::sysconf( _SC_THREAD_SAFE_FUNCTIONS ) >= 0 ) { return ::readdir_r( dirp, entry, result ); } # endif Seems like _POSIX_THREAD_SAFE_FUNCTIONS but doesn't expand to anything. Markus