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<title>Symbols In Guile (Debugging with GDB)</title>
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<link href="Symbol-Tables-In-Guile.html#Symbol-Tables-In-Guile" rel="next" title="Symbol Tables In Guile">
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<a name="Symbols-In-Guile"></a>
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<div class="header">
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<p>
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Next: <a href="Symbol-Tables-In-Guile.html#Symbol-Tables-In-Guile" accesskey="n" rel="next">Symbol Tables In Guile</a>, Previous: <a href="Blocks-In-Guile.html#Blocks-In-Guile" accesskey="p" rel="prev">Blocks In Guile</a>, Up: <a href="Guile-API.html#Guile-API" accesskey="u" rel="up">Guile API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Guile-representation-of-Symbols_002e"></a>
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<h4 class="subsubsection">23.3.3.17 Guile representation of Symbols.</h4>
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<a name="index-symbols-in-guile"></a>
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<a name="index-_003cgdb_003asymbol_003e"></a>
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<p><small>GDB</small> represents every variable, function and type as an
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entry in a symbol table. See <a href="Symbols.html#Symbols">Examining the Symbol Table</a>.
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Guile represents these symbols in <small>GDB</small> with the
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<code><gdb:symbol></code> object.
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</p>
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<p>The following symbol-related procedures are provided by the
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<code>(gdb)</code> module:
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</p>
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<dl>
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<dt><a name="index-symbol_003f"></a>Scheme Procedure: <strong>symbol?</strong> <em>object</em></dt>
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<dd><p>Return <code>#t</code> if <var>object</var> is an object of type <code><gdb:symbol></code>.
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Otherwise return <code>#f</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dvalid_003f"></a>Scheme Procedure: <strong>symbol-valid?</strong> <em>symbol</em></dt>
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<dd><p>Return <code>#t</code> if the <code><gdb:symbol></code> object is valid,
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<code>#f</code> if not. A <code><gdb:symbol></code> object can become invalid if
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the symbol it refers to does not exist in <small>GDB</small> any longer.
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All other <code><gdb:symbol></code> procedures will throw an exception if it is
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invalid at the time the procedure is called.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dtype"></a>Scheme Procedure: <strong>symbol-type</strong> <em>symbol</em></dt>
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<dd><p>Return the type of <var>symbol</var> or <code>#f</code> if no type is recorded.
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The result is an object of type <code><gdb:type></code>.
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See <a href="Types-In-Guile.html#Types-In-Guile">Types In Guile</a>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dsymtab"></a>Scheme Procedure: <strong>symbol-symtab</strong> <em>symbol</em></dt>
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<dd><p>Return the symbol table in which <var>symbol</var> appears.
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The result is an object of type <code><gdb:symtab></code>.
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See <a href="Symbol-Tables-In-Guile.html#Symbol-Tables-In-Guile">Symbol Tables In Guile</a>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dline"></a>Scheme Procedure: <strong>symbol-line</strong> <em>symbol</em></dt>
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<dd><p>Return the line number in the source code at which <var>symbol</var> was defined.
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This is an integer.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dname"></a>Scheme Procedure: <strong>symbol-name</strong> <em>symbol</em></dt>
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<dd><p>Return the name of <var>symbol</var> as a string.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dlinkage_002dname"></a>Scheme Procedure: <strong>symbol-linkage-name</strong> <em>symbol</em></dt>
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<dd><p>Return the name of <var>symbol</var>, as used by the linker (i.e., may be mangled).
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dprint_002dname"></a>Scheme Procedure: <strong>symbol-print-name</strong> <em>symbol</em></dt>
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<dd><p>Return the name of <var>symbol</var> in a form suitable for output. This is either
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<code>name</code> or <code>linkage_name</code>, depending on whether the user
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asked <small>GDB</small> to display demangled or mangled names.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002daddr_002dclass"></a>Scheme Procedure: <strong>symbol-addr-class</strong> <em>symbol</em></dt>
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<dd><p>Return the address class of the symbol. This classifies how to find the value
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of a symbol. Each address class is a constant defined in the
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<code>(gdb)</code> module and described later in this chapter.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dneeds_002dframe_003f"></a>Scheme Procedure: <strong>symbol-needs-frame?</strong> <em>symbol</em></dt>
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<dd><p>Return <code>#t</code> if evaluating <var>symbol</var>’s value requires a frame
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(see <a href="Frames-In-Guile.html#Frames-In-Guile">Frames In Guile</a>) and <code>#f</code> otherwise. Typically,
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local variables will require a frame, but other symbols will not.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dargument_003f"></a>Scheme Procedure: <strong>symbol-argument?</strong> <em>symbol</em></dt>
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<dd><p>Return <code>#t</code> if <var>symbol</var> is an argument of a function.
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Otherwise return <code>#f</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dconstant_003f"></a>Scheme Procedure: <strong>symbol-constant?</strong> <em>symbol</em></dt>
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<dd><p>Return <code>#t</code> if <var>symbol</var> is a constant.
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Otherwise return <code>#f</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dfunction_003f"></a>Scheme Procedure: <strong>symbol-function?</strong> <em>symbol</em></dt>
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<dd><p>Return <code>#t</code> if <var>symbol</var> is a function or a method.
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Otherwise return <code>#f</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dvariable_003f"></a>Scheme Procedure: <strong>symbol-variable?</strong> <em>symbol</em></dt>
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<dd><p>Return <code>#t</code> if <var>symbol</var> is a variable.
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Otherwise return <code>#f</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-symbol_002dvalue"></a>Scheme Procedure: <strong>symbol-value</strong> <em>symbol <span class="roman">[</span>#:frame frame<span class="roman">]</span></em></dt>
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<dd><p>Compute the value of <var>symbol</var>, as a <code><gdb:value></code>. For
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functions, this computes the address of the function, cast to the
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appropriate type. If the symbol requires a frame in order to compute
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its value, then <var>frame</var> must be given. If <var>frame</var> is not
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given, or if <var>frame</var> is invalid, then an exception is thrown.
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</p></dd></dl>
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<dl>
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<dt><a name="index-lookup_002dsymbol"></a>Scheme Procedure: <strong>lookup-symbol</strong> <em>name <span class="roman">[</span>#:block block<span class="roman">]</span> <span class="roman">[</span>#:domain domain<span class="roman">]</span></em></dt>
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<dd><p>This function searches for a symbol by name. The search scope can be
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restricted to the parameters defined in the optional domain and block
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arguments.
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</p>
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<p><var>name</var> is the name of the symbol. It must be a string. The
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optional <var>block</var> argument restricts the search to symbols visible
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in that <var>block</var>. The <var>block</var> argument must be a
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<code><gdb:block></code> object. If omitted, the block for the current frame
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is used. The optional <var>domain</var> argument restricts
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the search to the domain type. The <var>domain</var> argument must be a
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domain constant defined in the <code>(gdb)</code> module and described later
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in this chapter.
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</p>
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<p>The result is a list of two elements.
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The first element is a <code><gdb:symbol></code> object or <code>#f</code> if the symbol
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is not found.
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If the symbol is found, the second element is <code>#t</code> if the symbol
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is a field of a method’s object (e.g., <code>this</code> in C<tt>++</tt>),
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otherwise it is <code>#f</code>.
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If the symbol is not found, the second element is <code>#f</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-lookup_002dglobal_002dsymbol"></a>Scheme Procedure: <strong>lookup-global-symbol</strong> <em>name <span class="roman">[</span>#:domain domain<span class="roman">]</span></em></dt>
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<dd><p>This function searches for a global symbol by name.
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The search scope can be restricted by the domain argument.
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</p>
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<p><var>name</var> is the name of the symbol. It must be a string.
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The optional <var>domain</var> argument restricts the search to the domain type.
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The <var>domain</var> argument must be a domain constant defined in the <code>(gdb)</code>
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module and described later in this chapter.
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</p>
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<p>The result is a <code><gdb:symbol></code> object or <code>#f</code> if the symbol
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is not found.
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</p></dd></dl>
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<p>The available domain categories in <code><gdb:symbol></code> are represented
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as constants in the <code>(gdb)</code> module:
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</p>
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<dl compact="compact">
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<dt><code>SYMBOL_UNDEF_DOMAIN</code>
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<a name="index-SYMBOL_005fUNDEF_005fDOMAIN-1"></a>
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</dt>
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<dd><p>This is used when a domain has not been discovered or none of the
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following domains apply. This usually indicates an error either
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in the symbol information or in <small>GDB</small>’s handling of symbols.
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</p>
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</dd>
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<dt><code>SYMBOL_VAR_DOMAIN</code>
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<a name="index-SYMBOL_005fVAR_005fDOMAIN-1"></a>
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</dt>
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<dd><p>This domain contains variables, function names, typedef names and enum
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type values.
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</p>
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</dd>
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<dt><code>SYMBOL_STRUCT_DOMAIN</code>
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<a name="index-SYMBOL_005fSTRUCT_005fDOMAIN-1"></a>
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</dt>
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<dd><p>This domain holds struct, union and enum type names.
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</p>
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</dd>
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<dt><code>SYMBOL_LABEL_DOMAIN</code>
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<a name="index-SYMBOL_005fLABEL_005fDOMAIN-1"></a>
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</dt>
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<dd><p>This domain contains names of labels (for gotos).
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</p>
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</dd>
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<dt><code>SYMBOL_VARIABLES_DOMAIN</code>
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<a name="index-SYMBOL_005fVARIABLES_005fDOMAIN"></a>
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</dt>
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<dd><p>This domain holds a subset of the <code>SYMBOLS_VAR_DOMAIN</code>; it
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contains everything minus functions and types.
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</p>
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</dd>
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<dt><code>SYMBOL_FUNCTIONS_DOMAIN</code>
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<a name="index-SYMBOL_005fFUNCTIONS_005fDOMAIN"></a>
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</dt>
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<dd><p>This domain contains all functions.
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</p>
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</dd>
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<dt><code>SYMBOL_TYPES_DOMAIN</code>
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<a name="index-SYMBOL_005fTYPES_005fDOMAIN"></a>
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</dt>
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<dd><p>This domain contains all types.
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</p></dd>
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</dl>
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<p>The available address class categories in <code><gdb:symbol></code> are represented
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as constants in the <code>gdb</code> module:
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</p>
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<dl compact="compact">
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<dt><code>SYMBOL_LOC_UNDEF</code>
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<a name="index-SYMBOL_005fLOC_005fUNDEF-1"></a>
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</dt>
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<dd><p>If this is returned by address class, it indicates an error either in
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the symbol information or in <small>GDB</small>’s handling of symbols.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_CONST</code>
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<a name="index-SYMBOL_005fLOC_005fCONST-1"></a>
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</dt>
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<dd><p>Value is constant int.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_STATIC</code>
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<a name="index-SYMBOL_005fLOC_005fSTATIC-1"></a>
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</dt>
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<dd><p>Value is at a fixed address.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_REGISTER</code>
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<a name="index-SYMBOL_005fLOC_005fREGISTER-1"></a>
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</dt>
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<dd><p>Value is in a register.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_ARG</code>
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<a name="index-SYMBOL_005fLOC_005fARG-1"></a>
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</dt>
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<dd><p>Value is an argument. This value is at the offset stored within the
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symbol inside the frame’s argument list.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_REF_ARG</code>
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<a name="index-SYMBOL_005fLOC_005fREF_005fARG-1"></a>
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</dt>
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<dd><p>Value address is stored in the frame’s argument list. Just like
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<code>LOC_ARG</code> except that the value’s address is stored at the
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offset, not the value itself.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_REGPARM_ADDR</code>
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<a name="index-SYMBOL_005fLOC_005fREGPARM_005fADDR-1"></a>
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</dt>
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<dd><p>Value is a specified register. Just like <code>LOC_REGISTER</code> except
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the register holds the address of the argument instead of the argument
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itself.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_LOCAL</code>
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<a name="index-SYMBOL_005fLOC_005fLOCAL-1"></a>
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</dt>
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<dd><p>Value is a local variable.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_TYPEDEF</code>
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<a name="index-SYMBOL_005fLOC_005fTYPEDEF-1"></a>
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</dt>
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<dd><p>Value not used. Symbols in the domain <code>SYMBOL_STRUCT_DOMAIN</code> all
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have this class.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_BLOCK</code>
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<a name="index-SYMBOL_005fLOC_005fBLOCK-1"></a>
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</dt>
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<dd><p>Value is a block.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_CONST_BYTES</code>
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<a name="index-SYMBOL_005fLOC_005fCONST_005fBYTES-1"></a>
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</dt>
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<dd><p>Value is a byte-sequence.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_UNRESOLVED</code>
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<a name="index-SYMBOL_005fLOC_005fUNRESOLVED-1"></a>
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</dt>
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<dd><p>Value is at a fixed address, but the address of the variable has to be
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determined from the minimal symbol table whenever the variable is
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referenced.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_OPTIMIZED_OUT</code>
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<a name="index-SYMBOL_005fLOC_005fOPTIMIZED_005fOUT-1"></a>
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</dt>
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<dd><p>The value does not actually exist in the program.
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</p>
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</dd>
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<dt><code>SYMBOL_LOC_COMPUTED</code>
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<a name="index-SYMBOL_005fLOC_005fCOMPUTED-2"></a>
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</dt>
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<dd><p>The value’s address is a computed location.
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</p></dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Symbol-Tables-In-Guile.html#Symbol-Tables-In-Guile" accesskey="n" rel="next">Symbol Tables In Guile</a>, Previous: <a href="Blocks-In-Guile.html#Blocks-In-Guile" accesskey="p" rel="prev">Blocks In Guile</a>, Up: <a href="Guile-API.html#Guile-API" accesskey="u" rel="up">Guile API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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