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| <title>Debugging with GDB: Breakpoints In Guile</title> |
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| <a name="Breakpoints-In-Guile"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="Lazy-Strings-In-Guile.html#Lazy-Strings-In-Guile" accesskey="n" rel="next">Lazy Strings In Guile</a>, Previous: <a href="Symbol-Tables-In-Guile.html#Symbol-Tables-In-Guile" accesskey="p" rel="prev">Symbol Tables 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> |
| </div> |
| <hr> |
| <a name="Manipulating-breakpoints-using-Guile"></a> |
| <h4 class="subsubsection">23.3.3.19 Manipulating breakpoints using Guile</h4> |
| |
| <a name="index-breakpoints-in-guile"></a> |
| <a name="index-_003cgdb_003abreakpoint_003e"></a> |
| |
| <p>Breakpoints in Guile are represented by objects of type |
| <code><gdb:breakpoint></code>. New breakpoints can be created with the |
| <code>make-breakpoint</code> Guile function, and then added to <small>GDB</small> with the |
| <code>register-breakpoint!</code> Guile function. |
| This two-step approach is taken to separate out the side-effect of adding |
| the breakpoint to <small>GDB</small> from <code>make-breakpoint</code>. |
| </p> |
| <p>Support is also provided to view and manipulate breakpoints created |
| outside of Guile. |
| </p> |
| <p>The following breakpoint-related procedures are provided by the |
| <code>(gdb)</code> module: |
| </p> |
| <dl> |
| <dt><a name="index-make_002dbreakpoint"></a>Scheme Procedure: <strong>make-breakpoint</strong> <em>location <span class="roman">[</span>#:type type<span class="roman">]</span> <span class="roman">[</span>#:wp-class wp-class<span class="roman">]</span> <span class="roman">[</span>#:internal internal<span class="roman">]</span></em></dt> |
| <dd><p>Create a new breakpoint at <var>location</var>, a string naming the |
| location of the breakpoint, or an expression that defines a watchpoint. |
| The contents can be any location recognized by the <code>break</code> command, |
| or in the case of a watchpoint, by the <code>watch</code> command. |
| </p> |
| <p>The breakpoint is initially marked as ‘<samp>invalid</samp>’. |
| The breakpoint is not usable until it has been registered with <small>GDB</small> |
| with <code>register-breakpoint!</code>, at which point it becomes ‘<samp>valid</samp>’. |
| The result is the <code><gdb:breakpoint></code> object representing the breakpoint. |
| </p> |
| <p>The optional <var>type</var> denotes the breakpoint to create. |
| This argument can be either <code>BP_BREAKPOINT</code> or <code>BP_WATCHPOINT</code>, |
| and defaults to <code>BP_BREAKPOINT</code>. |
| </p> |
| <p>The optional <var>wp-class</var> argument defines the class of watchpoint to |
| create, if <var>type</var> is <code>BP_WATCHPOINT</code>. If a watchpoint class is |
| not provided, it is assumed to be a <code>WP_WRITE</code> class. |
| </p> |
| <p>The optional <var>internal</var> argument allows the breakpoint to become |
| invisible to the user. The breakpoint will neither be reported when |
| registered, nor will it be listed in the output from <code>info breakpoints</code> |
| (but will be listed with the <code>maint info breakpoints</code> command). |
| If an internal flag is not provided, the breakpoint is visible |
| (non-internal). |
| </p> |
| <p>When a watchpoint is created, <small>GDB</small> will try to create a |
| hardware assisted watchpoint. If successful, the type of the watchpoint |
| is changed from <code>BP_WATCHPOINT</code> to <code>BP_HARDWARE_WATCHPOINT</code> |
| for <code>WP_WRITE</code>, <code>BP_READ_WATCHPOINT</code> for <code>WP_READ</code>, |
| and <code>BP_ACCESS_WATCHPOINT</code> for <code>WP_ACCESS</code>. |
| If not successful, the type of the watchpoint is left as <code>WP_WATCHPOINT</code>. |
| </p> |
| <p>The available types are represented by constants defined in the <code>gdb</code> |
| module: |
| </p> |
| <dl compact="compact"> |
| <dt><code>BP_BREAKPOINT</code> |
| <a name="index-BP_005fBREAKPOINT-1"></a> |
| </dt> |
| <dd><p>Normal code breakpoint. |
| </p> |
| </dd> |
| <dt><code>BP_WATCHPOINT</code> |
| <a name="index-BP_005fWATCHPOINT-1"></a> |
| </dt> |
| <dd><p>Watchpoint breakpoint. |
| </p> |
| </dd> |
| <dt><code>BP_HARDWARE_WATCHPOINT</code> |
| <a name="index-BP_005fHARDWARE_005fWATCHPOINT-1"></a> |
| </dt> |
| <dd><p>Hardware assisted watchpoint. |
| This value cannot be specified when creating the breakpoint. |
| </p> |
| </dd> |
| <dt><code>BP_READ_WATCHPOINT</code> |
| <a name="index-BP_005fREAD_005fWATCHPOINT-1"></a> |
| </dt> |
| <dd><p>Hardware assisted read watchpoint. |
| This value cannot be specified when creating the breakpoint. |
| </p> |
| </dd> |
| <dt><code>BP_ACCESS_WATCHPOINT</code> |
| <a name="index-BP_005fACCESS_005fWATCHPOINT-1"></a> |
| </dt> |
| <dd><p>Hardware assisted access watchpoint. |
| This value cannot be specified when creating the breakpoint. |
| </p></dd> |
| </dl> |
| |
| <p>The available watchpoint types represented by constants are defined in the |
| <code>(gdb)</code> module: |
| </p> |
| <dl compact="compact"> |
| <dt><code>WP_READ</code> |
| <a name="index-WP_005fREAD-1"></a> |
| </dt> |
| <dd><p>Read only watchpoint. |
| </p> |
| </dd> |
| <dt><code>WP_WRITE</code> |
| <a name="index-WP_005fWRITE-1"></a> |
| </dt> |
| <dd><p>Write only watchpoint. |
| </p> |
| </dd> |
| <dt><code>WP_ACCESS</code> |
| <a name="index-WP_005fACCESS-1"></a> |
| </dt> |
| <dd><p>Read/Write watchpoint. |
| </p></dd> |
| </dl> |
| |
| </dd></dl> |
| |
| <dl> |
| <dt><a name="index-register_002dbreakpoint_0021"></a>Scheme Procedure: <strong>register-breakpoint!</strong> <em>breakpoint</em></dt> |
| <dd><p>Add <var>breakpoint</var>, a <code><gdb:breakpoint></code> object, to <small>GDB</small>’s |
| list of breakpoints. The breakpoint must have been created with |
| <code>make-breakpoint</code>. One cannot register breakpoints that have been |
| created outside of Guile. Once a breakpoint is registered it becomes |
| ‘<samp>valid</samp>’. |
| It is an error to register an already registered breakpoint. |
| The result is unspecified. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-delete_002dbreakpoint_0021"></a>Scheme Procedure: <strong>delete-breakpoint!</strong> <em>breakpoint</em></dt> |
| <dd><p>Remove <var>breakpoint</var> from <small>GDB</small>’s list of breakpoints. |
| This also invalidates the Guile <var>breakpoint</var> object. |
| Any further attempt to access the object will throw an exception. |
| </p> |
| <p>If <var>breakpoint</var> was created from Guile with <code>make-breakpoint</code> |
| it may be re-registered with <small>GDB</small>, in which case the breakpoint |
| becomes valid again. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoints-1"></a>Scheme Procedure: <strong>breakpoints</strong></dt> |
| <dd><p>Return a list of all breakpoints. |
| Each element of the list is a <code><gdb:breakpoint></code> object. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_003f"></a>Scheme Procedure: <strong>breakpoint?</strong> <em>object</em></dt> |
| <dd><p>Return <code>#t</code> if <var>object</var> is a <code><gdb:breakpoint></code> object, |
| and <code>#f</code> otherwise. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dvalid_003f"></a>Scheme Procedure: <strong>breakpoint-valid?</strong> <em>breakpoint</em></dt> |
| <dd><p>Return <code>#t</code> if <var>breakpoint</var> is valid, <code>#f</code> otherwise. |
| Breakpoints created with <code>make-breakpoint</code> are marked as invalid |
| until they are registered with <small>GDB</small> with <code>register-breakpoint!</code>. |
| A <code><gdb:breakpoint></code> object can become invalid |
| if the user deletes the breakpoint. In this case, the object still |
| exists, but the underlying breakpoint does not. In the cases of |
| watchpoint scope, the watchpoint remains valid even if execution of the |
| inferior leaves the scope of that watchpoint. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dnumber"></a>Scheme Procedure: <strong>breakpoint-number</strong> <em>breakpoint</em></dt> |
| <dd><p>Return the breakpoint’s number — the identifier used by |
| the user to manipulate the breakpoint. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dtype"></a>Scheme Procedure: <strong>breakpoint-type</strong> <em>breakpoint</em></dt> |
| <dd><p>Return the breakpoint’s type — the identifier used to |
| determine the actual breakpoint type or use-case. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dvisible_003f"></a>Scheme Procedure: <strong>breakpoint-visible?</strong> <em>breakpoint</em></dt> |
| <dd><p>Return <code>#t</code> if the breakpoint is visible to the user |
| when hit, or when the ‘<samp>info breakpoints</samp>’ command is run. |
| Otherwise return <code>#f</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dlocation"></a>Scheme Procedure: <strong>breakpoint-location</strong> <em>breakpoint</em></dt> |
| <dd><p>Return the location of the breakpoint, as specified by |
| the user. It is a string. If the breakpoint does not have a location |
| (that is, it is a watchpoint) return <code>#f</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dexpression"></a>Scheme Procedure: <strong>breakpoint-expression</strong> <em>breakpoint</em></dt> |
| <dd><p>Return the breakpoint expression, as specified by the user. It is a string. |
| If the breakpoint does not have an expression (the breakpoint is not a |
| watchpoint) return <code>#f</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002denabled_003f"></a>Scheme Procedure: <strong>breakpoint-enabled?</strong> <em>breakpoint</em></dt> |
| <dd><p>Return <code>#t</code> if the breakpoint is enabled, and <code>#f</code> otherwise. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dbreakpoint_002denabled_0021"></a>Scheme Procedure: <strong>set-breakpoint-enabled!</strong> <em>breakpoint flag</em></dt> |
| <dd><p>Set the enabled state of <var>breakpoint</var> to <var>flag</var>. |
| If flag is <code>#f</code> it is disabled, otherwise it is enabled. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dsilent_003f"></a>Scheme Procedure: <strong>breakpoint-silent?</strong> <em>breakpoint</em></dt> |
| <dd><p>Return <code>#t</code> if the breakpoint is silent, and <code>#f</code> otherwise. |
| </p> |
| <p>Note that a breakpoint can also be silent if it has commands and the |
| first command is <code>silent</code>. This is not reported by the |
| <code>silent</code> attribute. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dbreakpoint_002dsilent_0021"></a>Scheme Procedure: <strong>set-breakpoint-silent!</strong> <em>breakpoint flag</em></dt> |
| <dd><p>Set the silent state of <var>breakpoint</var> to <var>flag</var>. |
| If flag is <code>#f</code> the breakpoint is made silent, |
| otherwise it is made non-silent (or noisy). |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dignore_002dcount"></a>Scheme Procedure: <strong>breakpoint-ignore-count</strong> <em>breakpoint</em></dt> |
| <dd><p>Return the ignore count for <var>breakpoint</var>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dbreakpoint_002dignore_002dcount_0021"></a>Scheme Procedure: <strong>set-breakpoint-ignore-count!</strong> <em>breakpoint count</em></dt> |
| <dd><p>Set the ignore count for <var>breakpoint</var> to <var>count</var>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dhit_002dcount"></a>Scheme Procedure: <strong>breakpoint-hit-count</strong> <em>breakpoint</em></dt> |
| <dd><p>Return hit count of <var>breakpoint</var>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dbreakpoint_002dhit_002dcount_0021"></a>Scheme Procedure: <strong>set-breakpoint-hit-count!</strong> <em>breakpoint count</em></dt> |
| <dd><p>Set the hit count of <var>breakpoint</var> to <var>count</var>. |
| At present, <var>count</var> must be zero. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dthread"></a>Scheme Procedure: <strong>breakpoint-thread</strong> <em>breakpoint</em></dt> |
| <dd><p>Return the thread-id for thread-specific breakpoint <var>breakpoint</var>. |
| Return #f if <var>breakpoint</var> is not thread-specific. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dbreakpoint_002dthread_0021"></a>Scheme Procedure: <strong>set-breakpoint-thread!</strong> <em>breakpoint thread-id|#f</em></dt> |
| <dd><p>Set the thread-id for <var>breakpoint</var> to <var>thread-id</var>. |
| If set to <code>#f</code>, the breakpoint is no longer thread-specific. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dtask"></a>Scheme Procedure: <strong>breakpoint-task</strong> <em>breakpoint</em></dt> |
| <dd><p>If the breakpoint is Ada task-specific, return the Ada task id. |
| If the breakpoint is not task-specific (or the underlying |
| language is not Ada), return <code>#f</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dbreakpoint_002dtask_0021"></a>Scheme Procedure: <strong>set-breakpoint-task!</strong> <em>breakpoint task</em></dt> |
| <dd><p>Set the Ada task of <var>breakpoint</var> to <var>task</var>. |
| If set to <code>#f</code>, the breakpoint is no longer task-specific. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dcondition"></a>Scheme Procedure: <strong>breakpoint-condition</strong> <em>breakpoint</em></dt> |
| <dd><p>Return the condition of <var>breakpoint</var>, as specified by the user. |
| It is a string. If there is no condition, return <code>#f</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dbreakpoint_002dcondition_0021"></a>Scheme Procedure: <strong>set-breakpoint-condition!</strong> <em>breakpoint condition</em></dt> |
| <dd><p>Set the condition of <var>breakpoint</var> to <var>condition</var>, |
| which must be a string. If set to <code>#f</code> then the breakpoint |
| becomes unconditional. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dstop"></a>Scheme Procedure: <strong>breakpoint-stop</strong> <em>breakpoint</em></dt> |
| <dd><p>Return the stop predicate of <var>breakpoint</var>. |
| See <code>set-breakpoint-stop!</code> below in this section. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002dbreakpoint_002dstop_0021"></a>Scheme Procedure: <strong>set-breakpoint-stop!</strong> <em>breakpoint procedure|#f</em></dt> |
| <dd><p>Set the stop predicate of <var>breakpoint</var>. The predicate |
| <var>procedure</var> takes one argument: the <gdb:breakpoint> object. |
| If this predicate is set to a procedure then it is invoked whenever |
| the inferior reaches this breakpoint. If it returns <code>#t</code>, |
| or any non-<code>#f</code> value, then the inferior is stopped, |
| otherwise the inferior will continue. |
| </p> |
| <p>If there are multiple breakpoints at the same location with a |
| <code>stop</code> predicate, each one will be called regardless of the |
| return status of the previous. This ensures that all <code>stop</code> |
| predicates have a chance to execute at that location. In this scenario |
| if one of the methods returns <code>#t</code> but the others return |
| <code>#f</code>, the inferior will still be stopped. |
| </p> |
| <p>You should not alter the execution state of the inferior (i.e., step, |
| next, etc.), alter the current frame context (i.e., change the current |
| active frame), or alter, add or delete any breakpoint. As a general |
| rule, you should not alter any data within <small>GDB</small> or the inferior |
| at this time. |
| </p> |
| <p>Example <code>stop</code> implementation: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(define (my-stop? bkpt) |
| (let ((int-val (parse-and-eval "foo"))) |
| (value=? int-val 3))) |
| (define bkpt (make-breakpoint "main.c:42")) |
| (register-breakpoint! bkpt) |
| (set-breakpoint-stop! bkpt my-stop?) |
| </pre></div> |
| </dd></dl> |
| |
| <dl> |
| <dt><a name="index-breakpoint_002dcommands"></a>Scheme Procedure: <strong>breakpoint-commands</strong> <em>breakpoint</em></dt> |
| <dd><p>Return the commands attached to <var>breakpoint</var> as a string, |
| or <code>#f</code> if there are none. |
| </p></dd></dl> |
| |
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