ftp://ftp.cse.buffalo.edu/mirror/BSD/FreeBSD/development/FreeBSD-CVS/src/contrib/libstdc++/config/os/  direct

[DIR]aix/  direct  800+ twin directories
[DIR]bsd/  direct  680+ twin directories
[DIR]generic/  direct  1000+ twin directories
[DIR]djgpp/  direct  610+ twin directories
[DIR]mingw32/  direct  430+ twin directories
[DIR]gnu-linux/  direct  106 twin directories
[DIR]hpux/  direct  750+ twin directories
[DIR]irix/  direct  420+ twin directories
[DIR]newlib/  direct  470+ twin directories
[DIR]solaris/  direct  1000+ twin directories
[DIR]uclibc/  direct  450+ twin directories
[DIR]vxworks/  direct  95 twin directories
[DIR]tpf/  direct  87 twin directories
[DIR]osf/  direct  62 twin directories
[DIR]qnx/  direct  440+ twin directories
[DIR]windiss/  direct  102 twin directories