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<title>Symbols In Guile (Debugging with GDB)</title>

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<a name="Symbols-In-Guile"></a>
<div class="header">
<p>
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> &nbsp; [<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>
</div>
<hr>
<a name="Guile-representation-of-Symbols_002e"></a>
<h4 class="subsubsection">23.3.3.17 Guile representation of Symbols.</h4>

<a name="index-symbols-in-guile"></a>
<a name="index-_003cgdb_003asymbol_003e"></a>

<p><small>GDB</small> represents every variable, function and type as an
entry in a symbol table.  See <a href="Symbols.html#Symbols">Examining the Symbol Table</a>.
Guile represents these symbols in <small>GDB</small> with the
<code>&lt;gdb:symbol&gt;</code> object.
</p>
<p>The following symbol-related procedures are provided by the
<code>(gdb)</code> module:
</p>
<dl>
<dt><a name="index-symbol_003f"></a>Scheme Procedure: <strong>symbol?</strong> <em>object</em></dt>
<dd><p>Return <code>#t</code> if <var>object</var> is an object of type <code>&lt;gdb:symbol&gt;</code>.
Otherwise return <code>#f</code>.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dvalid_003f"></a>Scheme Procedure: <strong>symbol-valid?</strong> <em>symbol</em></dt>
<dd><p>Return <code>#t</code> if the <code>&lt;gdb:symbol&gt;</code> object is valid,
<code>#f</code> if not.  A <code>&lt;gdb:symbol&gt;</code> object can become invalid if
the symbol it refers to does not exist in <small>GDB</small> any longer.
All other <code>&lt;gdb:symbol&gt;</code> procedures will throw an exception if it is
invalid at the time the procedure is called.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dtype"></a>Scheme Procedure: <strong>symbol-type</strong> <em>symbol</em></dt>
<dd><p>Return the type of <var>symbol</var> or <code>#f</code> if no type is recorded.
The result is an object of type <code>&lt;gdb:type&gt;</code>.
See <a href="Types-In-Guile.html#Types-In-Guile">Types In Guile</a>.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dsymtab"></a>Scheme Procedure: <strong>symbol-symtab</strong> <em>symbol</em></dt>
<dd><p>Return the symbol table in which <var>symbol</var> appears.
The result is an object of type <code>&lt;gdb:symtab&gt;</code>.
See <a href="Symbol-Tables-In-Guile.html#Symbol-Tables-In-Guile">Symbol Tables In Guile</a>.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dline"></a>Scheme Procedure: <strong>symbol-line</strong> <em>symbol</em></dt>
<dd><p>Return the line number in the source code at which <var>symbol</var> was defined.
This is an integer.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dname"></a>Scheme Procedure: <strong>symbol-name</strong> <em>symbol</em></dt>
<dd><p>Return the name of <var>symbol</var> as a string.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dlinkage_002dname"></a>Scheme Procedure: <strong>symbol-linkage-name</strong> <em>symbol</em></dt>
<dd><p>Return the name of <var>symbol</var>, as used by the linker (i.e., may be mangled).
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dprint_002dname"></a>Scheme Procedure: <strong>symbol-print-name</strong> <em>symbol</em></dt>
<dd><p>Return the name of <var>symbol</var> in a form suitable for output.  This is either
<code>name</code> or <code>linkage_name</code>, depending on whether the user
asked <small>GDB</small> to display demangled or mangled names.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002daddr_002dclass"></a>Scheme Procedure: <strong>symbol-addr-class</strong> <em>symbol</em></dt>
<dd><p>Return the address class of the symbol.  This classifies how to find the value
of a symbol.  Each address class is a constant defined in the
<code>(gdb)</code> module and described later in this chapter.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dneeds_002dframe_003f"></a>Scheme Procedure: <strong>symbol-needs-frame?</strong> <em>symbol</em></dt>
<dd><p>Return <code>#t</code> if evaluating <var>symbol</var>&rsquo;s value requires a frame
(see <a href="Frames-In-Guile.html#Frames-In-Guile">Frames In Guile</a>) and <code>#f</code> otherwise.  Typically,
local variables will require a frame, but other symbols will not.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dargument_003f"></a>Scheme Procedure: <strong>symbol-argument?</strong> <em>symbol</em></dt>
<dd><p>Return <code>#t</code> if <var>symbol</var> is an argument of a function.
Otherwise return <code>#f</code>.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dconstant_003f"></a>Scheme Procedure: <strong>symbol-constant?</strong> <em>symbol</em></dt>
<dd><p>Return <code>#t</code> if <var>symbol</var> is a constant.
Otherwise return <code>#f</code>.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dfunction_003f"></a>Scheme Procedure: <strong>symbol-function?</strong> <em>symbol</em></dt>
<dd><p>Return <code>#t</code> if <var>symbol</var> is a function or a method.
Otherwise return <code>#f</code>.
</p></dd></dl>

<dl>
<dt><a name="index-symbol_002dvariable_003f"></a>Scheme Procedure: <strong>symbol-variable?</strong> <em>symbol</em></dt>
<dd><p>Return <code>#t</code> if <var>symbol</var> is a variable.
Otherwise return <code>#f</code>.
</p></dd></dl>

<dl>
<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>
<dd><p>Compute the value of <var>symbol</var>, as a <code>&lt;gdb:value&gt;</code>.  For
functions, this computes the address of the function, cast to the
appropriate type.  If the symbol requires a frame in order to compute
its value, then <var>frame</var> must be given.  If <var>frame</var> is not
given, or if <var>frame</var> is invalid, then an exception is thrown.
</p></dd></dl>

<dl>
<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>
<dd><p>This function searches for a symbol by name.  The search scope can be
restricted to the parameters defined in the optional domain and block
arguments.
</p>
<p><var>name</var> is the name of the symbol.  It must be a string.  The
optional <var>block</var> argument restricts the search to symbols visible
in that <var>block</var>.  The <var>block</var> argument must be a
<code>&lt;gdb:block&gt;</code> object.  If omitted, the block for the current frame
is used.  The optional <var>domain</var> argument restricts
the search to the domain type.  The <var>domain</var> argument must be a
domain constant defined in the <code>(gdb)</code> module and described later
in this chapter.
</p>
<p>The result is a list of two elements.
The first element is a <code>&lt;gdb:symbol&gt;</code> object or <code>#f</code> if the symbol
is not found.
If the symbol is found, the second element is <code>#t</code> if the symbol
is a field of a method&rsquo;s object (e.g., <code>this</code> in C<tt>++</tt>),
otherwise it is <code>#f</code>.
If the symbol is not found, the second element is <code>#f</code>.
</p></dd></dl>

<dl>
<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>
<dd><p>This function searches for a global symbol by name.
The search scope can be restricted by the domain argument.
</p>
<p><var>name</var> is the name of the symbol.  It must be a string.
The optional <var>domain</var> argument restricts the search to the domain type.
The <var>domain</var> argument must be a domain constant defined in the <code>(gdb)</code>
module and described later in this chapter.
</p>
<p>The result is a <code>&lt;gdb:symbol&gt;</code> object or <code>#f</code> if the symbol
is not found.
</p></dd></dl>

<p>The available domain categories in <code>&lt;gdb:symbol&gt;</code> are represented
as constants in the <code>(gdb)</code> module:
</p>
<dl compact="compact">
<dt><code>SYMBOL_UNDEF_DOMAIN</code>
<a name="index-SYMBOL_005fUNDEF_005fDOMAIN-1"></a>
</dt>
<dd><p>This is used when a domain has not been discovered or none of the
following domains apply.  This usually indicates an error either
in the symbol information or in <small>GDB</small>&rsquo;s handling of symbols.
</p>
</dd>
<dt><code>SYMBOL_VAR_DOMAIN</code>
<a name="index-SYMBOL_005fVAR_005fDOMAIN-1"></a>
</dt>
<dd><p>This domain contains variables, function names, typedef names and enum
type values.
</p>
</dd>
<dt><code>SYMBOL_STRUCT_DOMAIN</code>
<a name="index-SYMBOL_005fSTRUCT_005fDOMAIN-1"></a>
</dt>
<dd><p>This domain holds struct, union and enum type names.
</p>
</dd>
<dt><code>SYMBOL_LABEL_DOMAIN</code>
<a name="index-SYMBOL_005fLABEL_005fDOMAIN-1"></a>
</dt>
<dd><p>This domain contains names of labels (for gotos).
</p>
</dd>
<dt><code>SYMBOL_VARIABLES_DOMAIN</code>
<a name="index-SYMBOL_005fVARIABLES_005fDOMAIN"></a>
</dt>
<dd><p>This domain holds a subset of the <code>SYMBOLS_VAR_DOMAIN</code>; it
contains everything minus functions and types.
</p>
</dd>
<dt><code>SYMBOL_FUNCTIONS_DOMAIN</code>
<a name="index-SYMBOL_005fFUNCTIONS_005fDOMAIN"></a>
</dt>
<dd><p>This domain contains all functions.
</p>
</dd>
<dt><code>SYMBOL_TYPES_DOMAIN</code>
<a name="index-SYMBOL_005fTYPES_005fDOMAIN"></a>
</dt>
<dd><p>This domain contains all types.
</p></dd>
</dl>

<p>The available address class categories in <code>&lt;gdb:symbol&gt;</code> are represented
as constants in the <code>gdb</code> module:
</p>
<dl compact="compact">
<dt><code>SYMBOL_LOC_UNDEF</code>
<a name="index-SYMBOL_005fLOC_005fUNDEF-1"></a>
</dt>
<dd><p>If this is returned by address class, it indicates an error either in
the symbol information or in <small>GDB</small>&rsquo;s handling of symbols.
</p>
</dd>
<dt><code>SYMBOL_LOC_CONST</code>
<a name="index-SYMBOL_005fLOC_005fCONST-1"></a>
</dt>
<dd><p>Value is constant int.
</p>
</dd>
<dt><code>SYMBOL_LOC_STATIC</code>
<a name="index-SYMBOL_005fLOC_005fSTATIC-1"></a>
</dt>
<dd><p>Value is at a fixed address.
</p>
</dd>
<dt><code>SYMBOL_LOC_REGISTER</code>
<a name="index-SYMBOL_005fLOC_005fREGISTER-1"></a>
</dt>
<dd><p>Value is in a register.
</p>
</dd>
<dt><code>SYMBOL_LOC_ARG</code>
<a name="index-SYMBOL_005fLOC_005fARG-1"></a>
</dt>
<dd><p>Value is an argument.  This value is at the offset stored within the
symbol inside the frame&rsquo;s argument list.
</p>
</dd>
<dt><code>SYMBOL_LOC_REF_ARG</code>
<a name="index-SYMBOL_005fLOC_005fREF_005fARG-1"></a>
</dt>
<dd><p>Value address is stored in the frame&rsquo;s argument list.  Just like
<code>LOC_ARG</code> except that the value&rsquo;s address is stored at the
offset, not the value itself.
</p>
</dd>
<dt><code>SYMBOL_LOC_REGPARM_ADDR</code>
<a name="index-SYMBOL_005fLOC_005fREGPARM_005fADDR-1"></a>
</dt>
<dd><p>Value is a specified register.  Just like <code>LOC_REGISTER</code> except
the register holds the address of the argument instead of the argument
itself.
</p>
</dd>
<dt><code>SYMBOL_LOC_LOCAL</code>
<a name="index-SYMBOL_005fLOC_005fLOCAL-1"></a>
</dt>
<dd><p>Value is a local variable.
</p>
</dd>
<dt><code>SYMBOL_LOC_TYPEDEF</code>
<a name="index-SYMBOL_005fLOC_005fTYPEDEF-1"></a>
</dt>
<dd><p>Value not used.  Symbols in the domain <code>SYMBOL_STRUCT_DOMAIN</code> all
have this class.
</p>
</dd>
<dt><code>SYMBOL_LOC_BLOCK</code>
<a name="index-SYMBOL_005fLOC_005fBLOCK-1"></a>
</dt>
<dd><p>Value is a block.
</p>
</dd>
<dt><code>SYMBOL_LOC_CONST_BYTES</code>
<a name="index-SYMBOL_005fLOC_005fCONST_005fBYTES-1"></a>
</dt>
<dd><p>Value is a byte-sequence.
</p>
</dd>
<dt><code>SYMBOL_LOC_UNRESOLVED</code>
<a name="index-SYMBOL_005fLOC_005fUNRESOLVED-1"></a>
</dt>
<dd><p>Value is at a fixed address, but the address of the variable has to be
determined from the minimal symbol table whenever the variable is
referenced.
</p>
</dd>
<dt><code>SYMBOL_LOC_OPTIMIZED_OUT</code>
<a name="index-SYMBOL_005fLOC_005fOPTIMIZED_005fOUT-1"></a>
</dt>
<dd><p>The value does not actually exist in the program.
</p>
</dd>
<dt><code>SYMBOL_LOC_COMPUTED</code>
<a name="index-SYMBOL_005fLOC_005fCOMPUTED-2"></a>
</dt>
<dd><p>The value&rsquo;s address is a computed location.
</p></dd>
</dl>

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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> &nbsp; [<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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