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<a name="Label-Attributes"></a>
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<a name="Label-Attributes-1"></a>
<h3 class="section">6.36 Label Attributes</h3>
<a name="index-Label-Attributes"></a>

<p>GCC allows attributes to be set on C labels.  See <a href="Attribute-Syntax.html#Attribute-Syntax">Attribute Syntax</a>, for 
details of the exact syntax for using attributes.  Other attributes are 
available for functions (see <a href="Function-Attributes.html#Function-Attributes">Function Attributes</a>), variables 
(see <a href="Variable-Attributes.html#Variable-Attributes">Variable Attributes</a>), enumerators (see <a href="Enumerator-Attributes.html#Enumerator-Attributes">Enumerator Attributes</a>),
statements (see <a href="Statement-Attributes.html#Statement-Attributes">Statement Attributes</a>), and for types
(see <a href="Type-Attributes.html#Type-Attributes">Type Attributes</a>).
</p>
<p>This example uses the <code>cold</code> label attribute to indicate the 
<code>ErrorHandling</code> branch is unlikely to be taken and that the
<code>ErrorHandling</code> label is unused:
</p>
<div class="smallexample">
<pre class="smallexample">

   asm goto (&quot;some asm&quot; : : : : NoError);

/* This branch (the fall-through from the asm) is less commonly used */
ErrorHandling: 
   __attribute__((cold, unused)); /* Semi-colon is required here */
   printf(&quot;error\n&quot;);
   return 0;

NoError:
   printf(&quot;no error\n&quot;);
   return 1;
</pre></div>

<dl compact="compact">
<dt><code>unused</code></dt>
<dd><a name="index-unused-label-attribute"></a>
<p>This feature is intended for program-generated code that may contain 
unused labels, but which is compiled with <samp>-Wall</samp>.  It is
not normally appropriate to use in it human-written code, though it
could be useful in cases where the code that jumps to the label is
contained within an <code>#ifdef</code> conditional.
</p>
</dd>
<dt><code>hot</code></dt>
<dd><a name="index-hot-label-attribute"></a>
<p>The <code>hot</code> attribute on a label is used to inform the compiler that
the path following the label is more likely than paths that are not so
annotated.  This attribute is used in cases where <code>__builtin_expect</code>
cannot be used, for instance with computed goto or <code>asm goto</code>.
</p>
</dd>
<dt><code>cold</code></dt>
<dd><a name="index-cold-label-attribute"></a>
<p>The <code>cold</code> attribute on labels is used to inform the compiler that
the path following the label is unlikely to be executed.  This attribute
is used in cases where <code>__builtin_expect</code> cannot be used, for instance
with computed goto or <code>asm goto</code>.
</p>
</dd>
</dl>

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