79 lines
3.5 KiB
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79 lines
3.5 KiB
HTML
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<title>Global Variables - STABS</title>
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<a name="Global-Variables"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Register-Variables.html#Register-Variables">Register Variables</a>,
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Previous: <a rel="previous" accesskey="p" href="Stack-Variables.html#Stack-Variables">Stack Variables</a>,
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Up: <a rel="up" accesskey="u" href="Variables.html#Variables">Variables</a>
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</div>
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<h3 class="section">4.2 Global Variables</h3>
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<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 -->
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A variable whose scope is not specific to just one source file is
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represented by the ‘<samp><span class="samp">G</span></samp>’ symbol descriptor. These stabs use the
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<code>N_GSYM</code> stab type (C_GSYM for XCOFF). The type information for
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the stab (see <a href="String-Field.html#String-Field">String Field</a>) gives the type of the variable.
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<p>For example, the following source code:
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<pre class="example"> char g_foo = 'c';
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</pre>
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<p class="noindent">yields the following assembly code:
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<pre class="example"> .stabs "g_foo:G2",32,0,0,0 # <span class="roman">32 is N_GSYM</span>
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.global _g_foo
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.data
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_g_foo:
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.byte 99
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</pre>
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<p>The address of the variable represented by the <code>N_GSYM</code> is not
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contained in the <code>N_GSYM</code> stab. The debugger gets this information
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from the external symbol for the global variable. In the example above,
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the <code>.global _g_foo</code> and <code>_g_foo:</code> lines tell the assembler to
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produce an external symbol.
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<p>Some compilers, like GCC, output <code>N_GSYM</code> stabs only once, where
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the variable is defined. Other compilers, like SunOS4 /bin/cc, output a
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<code>N_GSYM</code> stab for each compilation unit which references the
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variable.
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</body></html>
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