<sect1 id="porting-configure">

	<title>Configure script and feature auto-activation</title>

      <sect2 id="configure-control">

	<title>Control your port</title>

	<para>When using a configure script, keep control on what feature is activated 

      or not. Avoid using auto-detection of libraries that would silently activate

      something you wouldn't be aware of. Say, explicitly disable options when you

      do not want them activated (do not just activate them when you want them).</para>

      </sect2>

      <sect2 id="configure-example">

	<title>Example</title>

      <para>Silently-activated features can bring you in trouble, let's give an example :</para>

      <itemizedlist>

        <listitem>

          <para>I have libxxx installed on my system (not used by any program)</para>

        </listitem>

        <listitem>

          <para>I don't want the application yyy to be built with xxx support so I disable the xxx option in the port's 'make config' or by defining the WITHOUT_XXX option</para>

        </listitem>

        <listitem>

          <para>Unfortunately, the port manages the option by *only* adding a --with-xxx (or --enable-xxx) option to <makevar>CONFIGURE_ARGS</makevar> when <makevar>WITH_XXX</makevar> is defined (so nothing happens here)</para>

        </listitem>

        <listitem>

          <para>The configure script is run and detects the library. It silently activates the option since our machine *can* run the xxx option</para>

        </listitem>

        <listitem>

          <para>The application is built with the xxx option</para>

        </listitem>

      </itemizedlist>

      </sect2>

      <sect2 id="configure-bad">

	<title>The bad things</title>

      <para>Why is it so bad ?</para>

      <itemizedlist>

        <listitem>

          <para>I have a feature I didn't want (that I have explicitly disabled)</para>

        </listitem>

        <listitem>

          <para>I can uninstall libxxx and break my application yyy, since no dependency is recorded in the database</para>

        </listitem>

      </itemizedlist>

      </sect2>

      <sect2 id="configure-solution">

	<title>A solution</title>

      <para>So, what can I do ?</para>

      <para>When possible, add (force) the corresponding --disable- or --without- option

      for *each* --enable- or --with one you are using in the port's Makefile (if 

      supported by the configure script). This will ensure that each dependency is

      recorded and that the port installs *exactly* the features users want.</para>

      </sect2>

      </sect1>