Thomas Porschberg <thomas.porschberg <at> osp-dd.de> writes: The rules for finding the right library to link are too primitive. E.g. if you install BOOST for Cygwin you get only libboost_filesystem-gcc-mt-s-1_33_1.a and libboost_filesystem-gcc-mt-s.a which are identical. I use now the following procedure to find the right library name: if test "$ax_cv_boost_filesystem" = "yes"; then AC_DEFINE(HAVE_BOOST_FILESYSTEM,,[define if the Boost::FILESYSTEM library is available]) for ax_lib in boost_filesystem boost_filesystem-$CC boost_filesystem-$CC-mt boost_filesystem-$CC-mt-s ; do AC_CHECK_LIB($ax_lib, main, [BOOST_FILESYSTEM_LIB="-l$ax_lib" AC_SUBST(BOOST_FILESYSTEM_LIB) link_filesystem="yes" break], [link_filesystem="no"]) done if test "x$link_filesystem" = "xno"; then AC_MSG_NOTICE(Could not link against $ax_lib !) fi fi