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<h3 class="section">4.2 Global Variables</h3>

<p><a name="index-N_005fGSYM-27"></a><a name="index-C_005fGSYM-28"></a><!-- FIXME: verify for sure that it really is C_GSYM on XCOFF -->
A variable whose scope is not specific to just one source file is
represented by the &lsquo;<samp><span class="samp">G</span></samp>&rsquo; symbol descriptor.  These stabs use the
<code>N_GSYM</code> stab type (C_GSYM for XCOFF).  The type information for
the stab (see <a href="String-Field.html#String-Field">String Field</a>) gives the type of the variable.

   <p>For example, the following source code:

<pre class="example">     char g_foo = 'c';
</pre>
   <p class="noindent">yields the following assembly code:

<pre class="example">     .stabs "g_foo:G2",32,0,0,0     # <span class="roman">32 is N_GSYM</span>
          .global _g_foo
          .data
     _g_foo:
          .byte 99
</pre>
   <p>The address of the variable represented by the <code>N_GSYM</code> is not
contained in the <code>N_GSYM</code> stab.  The debugger gets this information
from the external symbol for the global variable.  In the example above,
the <code>.global _g_foo</code> and <code>_g_foo:</code> lines tell the assembler to
produce an external symbol.

   <p>Some compilers, like GCC, output <code>N_GSYM</code> stabs only once, where
the variable is defined.  Other compilers, like SunOS4 /bin/cc, output a
<code>N_GSYM</code> stab for each compilation unit which references the
variable.

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