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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><gdb:block></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"> |
| — 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><gdb:block></code> object. |
| Otherwise return <code>#f</code>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — 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><gdb:block></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><gdb:block></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"> |
| — 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><gdb:block></code> <var>block</var>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — 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><gdb:block></code> <var>block</var>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>block-function</b><var> block<a name="index-block_002dfunction-2699"></a></var><br> |
| <blockquote><p>Return the name of <code><gdb:block></code> <var>block</var> represented as a |
| <code><gdb:symbol></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 – for instance this |
| happens for an inlined function. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>block-superblock</b><var> block<a name="index-block_002dsuperblock-2700"></a></var><br> |
| <blockquote><p>Return the block containing <code><gdb:block></code> <var>block</var>. |
| If the parent block does not exist, then <code>#f</code> is returned. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — 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><gdb:block></code> <var>block</var>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — 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><gdb:block></code> <var>block</var>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — 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><gdb:block></code> <var>block</var> is a global block. |
| Otherwise return <code>#f</code>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — 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><gdb:block></code> <var>block</var> is a static block. |
| Otherwise return <code>#f</code>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — 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 <gdb:symbol> objects) in |
| <code><gdb:block></code> <var>block</var>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — 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><gdb:iterator></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"> |
| — 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 <gdb:block-symbols-progress> object. |
| This object would be obtained from the <code>progress</code> element of the |
| <code><gdb:iterator></code> object returned by <code>make-block-symbols-iterator</code>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>lookup-block</b><var> pc<a name="index-lookup_002dblock-2708"></a></var><br> |
| <blockquote><p>Return the innermost <code><gdb:block></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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