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<h5 class="subsubsection">23.3.3.16 Accessing blocks from Guile.</h5>

<p><a name="index-blocks-in-guile-2693"></a><a name="index-g_t_003cgdb_003ablock_003e-2694"></a>
In <span class="sc">gdb</span>, symbols are stored in blocks.  A block corresponds
roughly to a scope in the source code.  Blocks are organized
hierarchically, and are represented individually in Guile as an object
of type <code>&lt;gdb:block&gt;</code>.  Blocks rely on debugging information being
available.

   <p>A frame has a block.  Please see <a href="Frames-In-Guile.html#Frames-In-Guile">Frames In Guile</a>, for a more
in-depth discussion of frames.

   <p>The outermost block is known as the <dfn>global block</dfn>.  The global
block typically holds public global variables and functions.

   <p>The block nested just inside the global block is the <dfn>static
block</dfn>.  The static block typically holds file-scoped variables and
functions.

   <p><span class="sc">gdb</span> provides a method to get a block's superblock, but there
is currently no way to examine the sub-blocks of a block, or to
iterate over all the blocks in a symbol table (see <a href="Symbol-Tables-In-Guile.html#Symbol-Tables-In-Guile">Symbol Tables In Guile</a>).

   <p>Here is a short example that should help explain blocks:

<pre class="smallexample">     /* This is in the global block.  */
     int global;
     
     /* This is in the static block.  */
     static int file_scope;
     
     /* 'function' is in the global block, and 'argument' is
        in a block nested inside of 'function'.  */
     int function (int argument)
     {
       /* 'local' is in a block inside 'function'.  It may or may
          not be in the same block as 'argument'.  */
       int local;
     
       {
          /* 'inner' is in a block whose superblock is the one holding
             'local'.  */
          int inner;
     
          /* If this call is expanded by the compiler, you may see
             a nested block here whose function is 'inline_function'
             and whose superblock is the one holding 'inner'.  */
          inline_function ();
       }
     }
</pre>
   <p>The following block-related procedures are provided by the
<code>(gdb)</code> module:

<div class="defun">
&mdash; Scheme Procedure: <b>block?</b><var> object<a name="index-block_003f-2695"></a></var><br>
<blockquote><p>Return <code>#t</code> if <var>object</var> is a <code>&lt;gdb:block&gt;</code> object. 
Otherwise return <code>#f</code>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-valid?</b><var> block<a name="index-block_002dvalid_003f-2696"></a></var><br>
<blockquote><p>Returns <code>#t</code> if <code>&lt;gdb:block&gt;</code> <var>block</var> is valid,
<code>#f</code> if not.  A block object can become invalid if the block it
refers to doesn't exist anymore in the inferior.  All other
<code>&lt;gdb:block&gt;</code> methods will throw an exception if it is invalid at
the time the procedure is called.  The block's validity is also checked
during iteration over symbols of the block. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-start</b><var> block<a name="index-block_002dstart-2697"></a></var><br>
<blockquote><p>Return the start address of <code>&lt;gdb:block&gt;</code> <var>block</var>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-end</b><var> block<a name="index-block_002dend-2698"></a></var><br>
<blockquote><p>Return the end address of <code>&lt;gdb:block&gt;</code> <var>block</var>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-function</b><var> block<a name="index-block_002dfunction-2699"></a></var><br>
<blockquote><p>Return the name of <code>&lt;gdb:block&gt;</code> <var>block</var> represented as a
<code>&lt;gdb:symbol&gt;</code> object. 
If the block is not named, then <code>#f</code> is returned.

        <p>For ordinary function blocks, the superblock is the static block. 
However, you should note that it is possible for a function block to
have a superblock that is not the static block &ndash; for instance this
happens for an inlined function. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-superblock</b><var> block<a name="index-block_002dsuperblock-2700"></a></var><br>
<blockquote><p>Return the block containing <code>&lt;gdb:block&gt;</code> <var>block</var>. 
If the parent block does not exist, then <code>#f</code> is returned. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-global-block</b><var> block<a name="index-block_002dglobal_002dblock-2701"></a></var><br>
<blockquote><p>Return the global block associated with <code>&lt;gdb:block&gt;</code> <var>block</var>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-static-block</b><var> block<a name="index-block_002dstatic_002dblock-2702"></a></var><br>
<blockquote><p>Return the static block associated with <code>&lt;gdb:block&gt;</code> <var>block</var>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-global?</b><var> block<a name="index-block_002dglobal_003f-2703"></a></var><br>
<blockquote><p>Return <code>#t</code> if <code>&lt;gdb:block&gt;</code> <var>block</var> is a global block. 
Otherwise return <code>#f</code>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-static?</b><var> block<a name="index-block_002dstatic_003f-2704"></a></var><br>
<blockquote><p>Return <code>#t</code> if <code>&lt;gdb:block&gt;</code> <var>block</var> is a static block. 
Otherwise return <code>#f</code>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-symbols</b><var><a name="index-block_002dsymbols-2705"></a></var><br>
<blockquote><p>Return a list of all symbols (as &lt;gdb:symbol&gt; objects) in
<code>&lt;gdb:block&gt;</code> <var>block</var>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>make-block-symbols-iterator</b><var> block<a name="index-make_002dblock_002dsymbols_002diterator-2706"></a></var><br>
<blockquote><p>Return an object of type <code>&lt;gdb:iterator&gt;</code> that will iterate
over all symbols of the block. 
Guile programs should not assume that a specific block object will
always contain a given symbol, since changes in <span class="sc">gdb</span> features and
infrastructure may cause symbols move across blocks in a symbol table. 
See <a href="Iterators-In-Guile.html#Iterators-In-Guile">Iterators In Guile</a>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>block-symbols-progress?</b><var><a name="index-block_002dsymbols_002dprogress_003f-2707"></a></var><br>
<blockquote><p>Return #t if the object is a &lt;gdb:block-symbols-progress&gt; object. 
This object would be obtained from the <code>progress</code> element of the
<code>&lt;gdb:iterator&gt;</code> object returned by <code>make-block-symbols-iterator</code>. 
</p></blockquote></div>

<div class="defun">
&mdash; Scheme Procedure: <b>lookup-block</b><var> pc<a name="index-lookup_002dblock-2708"></a></var><br>
<blockquote><p>Return the innermost <code>&lt;gdb:block&gt;</code> containing the given <var>pc</var>
value.  If the block cannot be found for the <var>pc</var> value specified,
the function will return <code>#f</code>. 
</p></blockquote></div>

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