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<a name="Macro-define-and-undefine"></a>
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<a name="Representation-of-_0023define-and-_0023undef"></a>
<h2 class="chapter">6 Representation of #define and #undef</h2>

<p>This section describes the stabs support for macro define and undefine
information, supported on some systems.  (e.g., with <samp>-g3</samp>
<samp>-gstabs</samp> when using GCC).
</p>
<p>A <code>#define <var>macro-name</var> <var>macro-body</var></code> is represented with
an <code>N_MAC_DEFINE</code> stab with a string field of
<code><var>macro-name</var> <var>macro-body</var></code>.
<a name="index-N_005fMAC_005fDEFINE"></a>
</p>
<p>An <code>#undef <var>macro-name</var></code> is represented with an
<code>N_MAC_UNDEF</code> stabs with a string field of simply
<code><var>macro-name</var></code>.
<a name="index-N_005fMAC_005fUNDEF"></a>
</p>
<p>For both <code>N_MAC_DEFINE</code> and <code>N_MAC_UNDEF</code>, the desc field is
the line number within the file where the corresponding <code>#define</code>
or <code>#undef</code> occurred.
</p>
<p>For example, the following C code:
</p>
<div class="example">
<pre class="example">    #define NONE	42
    #define TWO(a, b)	(a + (a) + 2 * b)
    #define ONE(c)	(c + 19)

    main(int argc, char *argv[])
    {
      func(NONE, TWO(10, 11));
      func(NONE, ONE(23));

    #undef ONE
    #define ONE(c)	(c + 23)

      func(NONE, ONE(-23));

      return (0);
    }

    int global;

    func(int arg1, int arg2)
    {
      global = arg1 + arg2;
    }
</pre></div>

<p>produces the following stabs (as well as many others):
</p>
<div class="example">
<pre class="example">    .stabs	&quot;NONE 42&quot;,54,0,1,0
    .stabs	&quot;TWO(a,b) (a + (a) + 2 * b)&quot;,54,0,2,0
    .stabs	&quot;ONE(c) (c + 19)&quot;,54,0,3,0
    .stabs	&quot;ONE&quot;,58,0,10,0
    .stabs	&quot;ONE(c) (c + 23)&quot;,54,0,11,0
</pre></div>

<p>NOTE: In the above example, <code>54</code> is <code>N_MAC_DEFINE</code> and
<code>58</code> is <code>N_MAC_UNDEF</code>.
</p>


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