source: trunk/essentials/sys-devel/automake-1.4/m4/sanity.m4

#
# Check to make sure that the build environment is sane.
#

AC_DEFUN([AM_SANITY_CHECK],
[AC_MSG_CHECKING([whether build environment is sane])
# Just in case
sleep 1
echo timestamp > conftestfile
# Do `set' in a subshell so we don't clobber the current shell's
# arguments.  Must try -L first in case configure is actually a
# symlink; some systems play weird games with the mod time of symlinks
# (eg FreeBSD returns the mod time of the symlink's containing
# directory).
if (
   set X `ls -Lt $srcdir/configure conftestfile 2> /dev/null`
   if test "[$]*" = "X"; then
      # -L didn't work.
      set X `ls -t $srcdir/configure conftestfile`
   fi
   if test "[$]*" != "X $srcdir/configure conftestfile" \
      && test "[$]*" != "X conftestfile $srcdir/configure"; then

      # If neither matched, then we have a broken ls.  This can happen
      # if, for instance, CONFIG_SHELL is bash and it inherits a
      # broken ls alias from the environment.  This has actually
      # happened.  Such a system could not be considered "sane".
      AC_MSG_ERROR([ls -t appears to fail.  Make sure there is not a broken
alias in your environment])
   fi

   test "[$]2" = conftestfile
   )
then
   # Ok.
   :
else
   AC_MSG_ERROR([newly created file is older than distributed files!
Check your system clock])
fi
rm -f conftest*
AC_MSG_RESULT(yes)])