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| <title>Debugging with GDB: Breakpoints In Python</title> |
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| <a name="Breakpoints-In-Python"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="Finish-Breakpoints-in-Python.html#Finish-Breakpoints-in-Python" accesskey="n" rel="next">Finish Breakpoints in Python</a>, Previous: <a href="Line-Tables-In-Python.html#Line-Tables-In-Python" accesskey="p" rel="prev">Line Tables In Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python 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-Python"></a> |
| <h4 class="subsubsection">23.2.2.29 Manipulating breakpoints using Python</h4> |
| |
| <a name="index-breakpoints-in-python"></a> |
| <a name="index-gdb_002eBreakpoint"></a> |
| |
| <p>Python code can manipulate breakpoints via the <code>gdb.Breakpoint</code> |
| class. |
| </p> |
| <dl> |
| <dt><a name="index-Breakpoint_002e_005f_005finit_005f_005f"></a>Function: <strong>Breakpoint.__init__</strong> <em>(spec <span class="roman">[</span>, type <span class="roman">[</span>, wp_class <span class="roman">[</span>,internal <span class="roman">[</span>,temporary<span class="roman">]]]]</span>)</em></dt> |
| <dd><p>Create a new breakpoint according to <var>spec</var>, which is 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. The optional <var>type</var> denotes the breakpoint |
| to create from the types defined later in this chapter. This argument |
| can be either <code>gdb.BP_BREAKPOINT</code> or <code>gdb.BP_WATCHPOINT</code>; it |
| defaults to <code>gdb.BP_BREAKPOINT</code>. The optional <var>internal</var> |
| argument allows the breakpoint to become invisible to the user. The |
| breakpoint will neither be reported when created, 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). The optional |
| <var>temporary</var> argument makes the breakpoint a temporary breakpoint. |
| Temporary breakpoints are deleted after they have been hit. Any |
| further access to the Python breakpoint after it has been hit will |
| result in a runtime error (as that breakpoint has now been |
| automatically deleted). The optional <var>wp_class</var> argument defines |
| the class of watchpoint to create, if <var>type</var> is |
| <code>gdb.BP_WATCHPOINT</code>. If a watchpoint class is not provided, it |
| is assumed to be a <code>gdb.WP_WRITE</code> class. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002estop"></a>Function: <strong>Breakpoint.stop</strong> <em>(self)</em></dt> |
| <dd><p>The <code>gdb.Breakpoint</code> class can be sub-classed and, in |
| particular, you may choose to implement the <code>stop</code> method. |
| If this method is defined in a sub-class of <code>gdb.Breakpoint</code>, |
| it will be called when the inferior reaches any location of a |
| breakpoint which instantiates that sub-class. If the method returns |
| <code>True</code>, the inferior will be stopped at the location of the |
| breakpoint, otherwise the inferior will continue. |
| </p> |
| <p>If there are multiple breakpoints at the same location with a |
| <code>stop</code> method, each one will be called regardless of the |
| return status of the previous. This ensures that all <code>stop</code> |
| methods have a chance to execute at that location. In this scenario |
| if one of the methods returns <code>True</code> but the others return |
| <code>False</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">class MyBreakpoint (gdb.Breakpoint): |
| def stop (self): |
| inf_val = gdb.parse_and_eval("foo") |
| if inf_val == 3: |
| return True |
| return False |
| </pre></div> |
| </dd></dl> |
| |
| <p>The available watchpoint types represented by constants are defined in the |
| <code>gdb</code> module: |
| </p> |
| <dl compact="compact"> |
| <dd><a name="index-WP_005fREAD"></a> |
| </dd> |
| <dt><code>gdb.WP_READ</code> |
| <a name="index-gdb_002eWP_005fREAD"></a> |
| </dt> |
| <dd><p>Read only watchpoint. |
| </p> |
| <a name="index-WP_005fWRITE"></a> |
| </dd> |
| <dt><code>gdb.WP_WRITE</code> |
| <a name="index-gdb_002eWP_005fWRITE"></a> |
| </dt> |
| <dd><p>Write only watchpoint. |
| </p> |
| <a name="index-WP_005fACCESS"></a> |
| </dd> |
| <dt><code>gdb.WP_ACCESS</code> |
| <a name="index-gdb_002eWP_005fACCESS"></a> |
| </dt> |
| <dd><p>Read/Write watchpoint. |
| </p></dd> |
| </dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002eis_005fvalid"></a>Function: <strong>Breakpoint.is_valid</strong> <em>()</em></dt> |
| <dd><p>Return <code>True</code> if this <code>Breakpoint</code> object is valid, |
| <code>False</code> otherwise. A <code>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_002edelete"></a>Function: <strong>Breakpoint.delete</strong> <em>()</em></dt> |
| <dd><p>Permanently deletes the <small>GDB</small> breakpoint. This also |
| invalidates the Python <code>Breakpoint</code> object. Any further access |
| to this object’s attributes or methods will raise an error. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002eenabled"></a>Variable: <strong>Breakpoint.enabled</strong></dt> |
| <dd><p>This attribute is <code>True</code> if the breakpoint is enabled, and |
| <code>False</code> otherwise. This attribute is writable. You can use it to enable |
| or disable the breakpoint. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002esilent"></a>Variable: <strong>Breakpoint.silent</strong></dt> |
| <dd><p>This attribute is <code>True</code> if the breakpoint is silent, and |
| <code>False</code> otherwise. This attribute is writable. |
| </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-Breakpoint_002ethread"></a>Variable: <strong>Breakpoint.thread</strong></dt> |
| <dd><p>If the breakpoint is thread-specific, this attribute holds the thread |
| id. If the breakpoint is not thread-specific, this attribute is |
| <code>None</code>. This attribute is writable. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002etask"></a>Variable: <strong>Breakpoint.task</strong></dt> |
| <dd><p>If the breakpoint is Ada task-specific, this attribute holds the Ada task |
| id. If the breakpoint is not task-specific (or the underlying |
| language is not Ada), this attribute is <code>None</code>. This attribute |
| is writable. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002eignore_005fcount"></a>Variable: <strong>Breakpoint.ignore_count</strong></dt> |
| <dd><p>This attribute holds the ignore count for the breakpoint, an integer. |
| This attribute is writable. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002enumber"></a>Variable: <strong>Breakpoint.number</strong></dt> |
| <dd><p>This attribute holds the breakpoint’s number — the identifier used by |
| the user to manipulate the breakpoint. This attribute is not writable. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002etype"></a>Variable: <strong>Breakpoint.type</strong></dt> |
| <dd><p>This attribute holds the breakpoint’s type — the identifier used to |
| determine the actual breakpoint type or use-case. This attribute is not |
| writable. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002evisible"></a>Variable: <strong>Breakpoint.visible</strong></dt> |
| <dd><p>This attribute tells whether the breakpoint is visible to the user |
| when set, or when the ‘<samp>info breakpoints</samp>’ command is run. This |
| attribute is not writable. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002etemporary"></a>Variable: <strong>Breakpoint.temporary</strong></dt> |
| <dd><p>This attribute indicates whether the breakpoint was created as a |
| temporary breakpoint. Temporary breakpoints are automatically deleted |
| after that breakpoint has been hit. Access to this attribute, and all |
| other attributes and functions other than the <code>is_valid</code> |
| function, will result in an error after the breakpoint has been hit |
| (as it has been automatically deleted). This attribute is not |
| writable. |
| </p></dd></dl> |
| |
| <p>The available types are represented by constants defined in the <code>gdb</code> |
| module: |
| </p> |
| <dl compact="compact"> |
| <dd><a name="index-BP_005fBREAKPOINT"></a> |
| </dd> |
| <dt><code>gdb.BP_BREAKPOINT</code> |
| <a name="index-gdb_002eBP_005fBREAKPOINT"></a> |
| </dt> |
| <dd><p>Normal code breakpoint. |
| </p> |
| <a name="index-BP_005fWATCHPOINT"></a> |
| </dd> |
| <dt><code>gdb.BP_WATCHPOINT</code> |
| <a name="index-gdb_002eBP_005fWATCHPOINT"></a> |
| </dt> |
| <dd><p>Watchpoint breakpoint. |
| </p> |
| <a name="index-BP_005fHARDWARE_005fWATCHPOINT"></a> |
| </dd> |
| <dt><code>gdb.BP_HARDWARE_WATCHPOINT</code> |
| <a name="index-gdb_002eBP_005fHARDWARE_005fWATCHPOINT"></a> |
| </dt> |
| <dd><p>Hardware assisted watchpoint. |
| </p> |
| <a name="index-BP_005fREAD_005fWATCHPOINT"></a> |
| </dd> |
| <dt><code>gdb.BP_READ_WATCHPOINT</code> |
| <a name="index-gdb_002eBP_005fREAD_005fWATCHPOINT"></a> |
| </dt> |
| <dd><p>Hardware assisted read watchpoint. |
| </p> |
| <a name="index-BP_005fACCESS_005fWATCHPOINT"></a> |
| </dd> |
| <dt><code>gdb.BP_ACCESS_WATCHPOINT</code> |
| <a name="index-gdb_002eBP_005fACCESS_005fWATCHPOINT"></a> |
| </dt> |
| <dd><p>Hardware assisted access watchpoint. |
| </p></dd> |
| </dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002ehit_005fcount"></a>Variable: <strong>Breakpoint.hit_count</strong></dt> |
| <dd><p>This attribute holds the hit count for the breakpoint, an integer. |
| This attribute is writable, but currently it can only be set to zero. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002elocation"></a>Variable: <strong>Breakpoint.location</strong></dt> |
| <dd><p>This attribute holds 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) the attribute’s value is <code>None</code>. This |
| attribute is not writable. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002eexpression"></a>Variable: <strong>Breakpoint.expression</strong></dt> |
| <dd><p>This attribute holds a 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) the attribute’s value |
| is <code>None</code>. This attribute is not writable. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002econdition"></a>Variable: <strong>Breakpoint.condition</strong></dt> |
| <dd><p>This attribute holds the condition of the breakpoint, as specified by |
| the user. It is a string. If there is no condition, this attribute’s |
| value is <code>None</code>. This attribute is writable. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-Breakpoint_002ecommands"></a>Variable: <strong>Breakpoint.commands</strong></dt> |
| <dd><p>This attribute holds the commands attached to the breakpoint. If |
| there are commands, this attribute’s value is a string holding all the |
| commands, separated by newlines. If there are no commands, this |
| attribute is <code>None</code>. This attribute is not writable. |
| </p></dd></dl> |
| |
| <hr> |
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| Next: <a href="Finish-Breakpoints-in-Python.html#Finish-Breakpoints-in-Python" accesskey="n" rel="next">Finish Breakpoints in Python</a>, Previous: <a href="Line-Tables-In-Python.html#Line-Tables-In-Python" accesskey="p" rel="prev">Line Tables In Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python 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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