The problem with the C preprocessor is that it's sat in a "sour spot" where it's often possible to use it for a task but only by bending it so far that the result is pretty ugly and not very comprehensible. If the preprocessor were less powerful it would be obvious you needed to use a different tool; if it were more powerful it wouldn't result in ugly messes; but it's sat in the sour spot in the middle.

(Make is another tool which suffers from 'sour spot' syndrome IMHO.)