pkg_config

# File lib/mkmf.rb, line 1791
  def pkg_config(pkg, option=nil)
    if pkgconfig = with_config("#{pkg}-config") and find_executable0(pkgconfig)
      # iff package specific config command is given
    elsif ($PKGCONFIG ||=
           (pkgconfig = with_config("pkg-config", ("pkg-config" unless CROSS_COMPILING))) &&
           find_executable0(pkgconfig) && pkgconfig) and
        xsystem("#{$PKGCONFIG} --exists #{pkg}")
      # default to pkg-config command
      pkgconfig = $PKGCONFIG
      get = proc {|opt|
        opt = xpopen("#{$PKGCONFIG} --#{opt} #{pkg}", err[[:child, :out], &:read)
        Logging.open {puts opt.each_line.map{|s|"=> #{s.inspect}"}}
        opt.strip if $?.success?
      }
    elsif find_executable0(pkgconfig = "#{pkg}-config")
      # default to package specific config command, as a last resort.
    else
      pkgconfig = nil
    end
    if pkgconfig
      get ||= proc {|opt|
        opt = xpopen("#{pkgconfig} --#{opt}", err[[:child, :out], &:read)
        Logging.open {puts opt.each_line.map{|s|"=> #{s.inspect}"}}
        opt.strip if $?.success?
      }
    end
    orig_ldflags = $LDFLAGS
    if get and option
      get[option]
    elsif get and try_ldflags(ldflags = get['libs'])
      if incflags = get['cflags-only-I']
        $INCFLAGS << " " << incflags
        cflags = get['cflags-only-other']
      else
        cflags = get['cflags']
      end
      libs = get['libs-only-l']
      if cflags
        $CFLAGS += " " << cflags
        $CXXFLAGS += " " << cflags
      end
      if libs
        ldflags = (Shellwords.shellwords(ldflags) - Shellwords.shellwords(libs)).quote.join(" ")
      else
        libs, ldflags = Shellwords.shellwords(ldflags).partition {|s| s =~ /-l([^ ]+)/ }.map {|l|l.quote.join(" ")}
      end
      $libs += " " << libs

      $LDFLAGS = [orig_ldflags, ldflags].join(' ')
      Logging::message "package configuration for %s\n", pkg
      Logging::message "cflags: %s\nldflags: %s\nlibs: %s\n\n",
                       cflags, ldflags, libs
      [cflags, ldflags, libs]
    else
      Logging::message "package configuration for %s is not found\n", pkg
      nil
    end
  end