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<a name="Cross_002dReferences"></a>
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<a name="Cross_002dReferences-to-Other-Types"></a>
<h3 class="section">5.3 Cross-References to Other Types</h3>

<p>A type can be used before it is defined; one common way to deal with
that situation is just to use a type reference to a type which has not
yet been defined.
</p>
<p>Another way is with the &lsquo;<samp>x</samp>&rsquo; type descriptor, which is followed by
&lsquo;<samp>s</samp>&rsquo; for a structure tag, &lsquo;<samp>u</samp>&rsquo; for a union tag, or &lsquo;<samp>e</samp>&rsquo; for
a enumerator tag, followed by the name of the tag, followed by &lsquo;<samp>:</samp>&rsquo;.
If the name contains &lsquo;<samp>::</samp>&rsquo; between a &lsquo;<samp>&lt;</samp>&rsquo; and &lsquo;<samp>&gt;</samp>&rsquo; pair (for
C<tt>++</tt> templates), such a &lsquo;<samp>::</samp>&rsquo; does not end the name&mdash;only a single
&lsquo;<samp>:</samp>&rsquo; ends the name; see <a href="Nested-Symbols.html#Nested-Symbols">Nested Symbols</a>.
</p>
<p>For example, the following C declarations:
</p>
<div class="example">
<pre class="example">struct foo;
struct foo *bar;
</pre></div>

<p>produce:
</p>
<div class="example">
<pre class="example">.stabs &quot;bar:G16=*17=xsfoo:&quot;,32,0,0,0
</pre></div>

<p>Not all debuggers support the &lsquo;<samp>x</samp>&rsquo; type descriptor, so on some
machines GCC does not use it.  I believe that for the above example it
would just emit a reference to type 17 and never define it, but I
haven&rsquo;t verified that.
</p>
<p>Modula-2 imported types, at least on AIX, use the &lsquo;<samp>i</samp>&rsquo; type
descriptor, which is followed by the name of the module from which the
type is imported, followed by &lsquo;<samp>:</samp>&rsquo;, followed by the name of the
type.  There is then optionally a comma followed by type information for
the type.  This differs from merely naming the type (see <a href="Typedefs.html#Typedefs">Typedefs</a>) in
that it identifies the module; I don&rsquo;t understand whether the name of
the type given here is always just the same as the name we are giving
it, or whether this type descriptor is used with a nameless stab
(see <a href="String-Field.html#String-Field">String Field</a>), or what.  The symbol ends with &lsquo;<samp>;</samp>&rsquo;.
</p>
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