Simple unused #define finder.

unused_define.rb

#!/usr/bin/env ruby
require 'pp'

if ARGV[0]

  # Collect defines.
  defines = {}

  Dir.glob("#{ARGV[0]}/**/*.{c,h}") do |path|
    File.open(path, "r") do |file|
      file.each_line do |line|
        if line =~ /^#define\s*(\S*)\s*.*$/
          defines[$1] = false
        end
      end
    end
  end

  # Find uses.
  Dir.glob("#{ARGV[0]}/**/*.{c,h}") do |path|
    File.open(path, "r") do |file|
      file.each_line do |line|
        unless line =~ /#define/
          defines.each do |k,v|
            defines[k] = v || line.include?(k)
          end
        end
      end
    end
  end

  # Print unused.
  defines.select { |k,v| v == false }.each do |k,v|
    puts k
  end
end