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<a name="PROVIDE-1"></a>
<h4 class="subsection">3.5.3 PROVIDE</h4>
<a name="index-PROVIDE"></a>
<p>In some cases, it is desirable for a linker script to define a symbol
only if it is referenced and is not defined by any object included in
the link.  For example, traditional linkers defined the symbol
&lsquo;<samp>etext</samp>&rsquo;.  However, ANSI C requires that the user be able to use
&lsquo;<samp>etext</samp>&rsquo; as a function name without encountering an error.  The
<code>PROVIDE</code> keyword may be used to define a symbol, such as
&lsquo;<samp>etext</samp>&rsquo;, only if it is referenced but not defined.  The syntax is
<code>PROVIDE(<var>symbol</var> = <var>expression</var>)</code>.
</p>
<p>Here is an example of using <code>PROVIDE</code> to define &lsquo;<samp>etext</samp>&rsquo;:
</p><div class="smallexample">
<pre class="smallexample">SECTIONS
{
  .text :
    {
      *(.text)
      _etext = .;
      PROVIDE(etext = .);
    }
}
</pre></div>

<p>In this example, if the program defines &lsquo;<samp>_etext</samp>&rsquo; (with a leading
underscore), the linker will give a multiple definition error.  If, on
the other hand, the program defines &lsquo;<samp>etext</samp>&rsquo; (with no leading
underscore), the linker will silently use the definition in the program.
If the program references &lsquo;<samp>etext</samp>&rsquo; but does not define it, the
linker will use the definition in the linker script.
</p>
<p>Note - the <code>PROVIDE</code> directive considers a common symbol to be
defined, even though such a symbol could be combined with the symbol
that the <code>PROVIDE</code> would create.  This is particularly important
when considering constructor and destructor list symbols such as
&lsquo;<samp>__CTOR_LIST__</samp>&rsquo; as these are often defined as common symbols.
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