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  24 <a name="gtype-non-instantiable"></a>Non-instantiable non-classed fundamental types</h2></div></div></div>
  25 <p>
  26           A lot of types are not instantiable by the type system and do not have
  27           a class. Most of these types are fundamental trivial types such as <span class="emphasis"><em>gchar</em></span>,
  28           registered in <code class="function">_g_value_types_init</code> (in <code class="filename">gvaluetypes.c</code>).
  29         </p>
  30 <p>
  31           To register such a type in the type system, you just need to fill the
  32           <a class="link" href="gobject-Type-Information.html#GTypeInfo" title="struct GTypeInfo"><span class="type">GTypeInfo</span></a> structure with zeros since these types are also most of the time
  33           fundamental:
  34           </p>
  35 <pre class="programlisting">
  36   GTypeInfo info = {
  37     0,                                /* class_size */
  38     NULL,                        /* base_init */
  39     NULL,                        /* base_destroy */
  40     NULL,                        /* class_init */
  41     NULL,                        /* class_destroy */
  42     NULL,                        /* class_data */
  43     0,                                /* instance_size */
  44     0,                                /* n_preallocs */
  45     NULL,                        /* instance_init */
  46     NULL,                        /* value_table */
  47   };
  48   static const GTypeValueTable value_table = {
  49     value_init_long0,                /* value_init */
  50     NULL,                        /* value_free */
  51     value_copy_long0,                /* value_copy */
  52     NULL,                        /* value_peek_pointer */
  53     "i",                        /* collect_format */
  54     value_collect_int,        /* collect_value */
  55     "p",                        /* lcopy_format */
  56     value_lcopy_char,                /* lcopy_value */
  57   };
  58   info.value_table = &amp;value_table;
  59   type = g_type_register_fundamental (G_TYPE_CHAR, "gchar", &amp;info, &amp;finfo, 0);
  60           </pre>
  61 <p>
  62         </p>
  63 <p>
  64           Having non-instantiable types might seem a bit useless: what good is a type
  65           if you cannot instantiate an instance of that type ? Most of these types
  66           are used in conjunction with <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>s: a GValue is initialized
  67           with an integer or a string and it is passed around by using the registered
  68           type's value_table. <a class="link" href="gobject-Generic-values.html#GValue" title="GValue"><span class="type">GValue</span></a>s (and by extension these trivial fundamental
  69           types) are most useful when used in conjunction with object properties and signals.
  70         </p>
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