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| <a name="Events-In-Python"></a> |
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| |
| <h5 class="subsubsection">23.2.2.17 Events In Python</h5> |
| |
| <p><a name="index-inferior-events-in-Python-2071"></a> |
| <span class="sc">gdb</span> provides a general event facility so that Python code can be |
| notified of various state changes, particularly changes that occur in |
| the inferior. |
| |
| <p>An <dfn>event</dfn> is just an object that describes some state change. The |
| type of the object and its attributes will vary depending on the details |
| of the change. All the existing events are described below. |
| |
| <p>In order to be notified of an event, you must register an event handler |
| with an <dfn>event registry</dfn>. An event registry is an object in the |
| <code>gdb.events</code> module which dispatches particular events. A registry |
| provides methods to register and unregister event handlers: |
| |
| <div class="defun"> |
| — Function: <b>EventRegistry.connect</b> (<var>object</var>)<var><a name="index-EventRegistry_002econnect-2072"></a></var><br> |
| <blockquote><p>Add the given callable <var>object</var> to the registry. This object will be |
| called when an event corresponding to this registry occurs. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Function: <b>EventRegistry.disconnect</b> (<var>object</var>)<var><a name="index-EventRegistry_002edisconnect-2073"></a></var><br> |
| <blockquote><p>Remove the given <var>object</var> from the registry. Once removed, the object |
| will no longer receive notifications of events. |
| </p></blockquote></div> |
| |
| <p>Here is an example: |
| |
| <pre class="smallexample"> def exit_handler (event): |
| print "event type: exit" |
| print "exit code: %d" % (event.exit_code) |
| |
| gdb.events.exited.connect (exit_handler) |
| </pre> |
| <p>In the above example we connect our handler <code>exit_handler</code> to the |
| registry <code>events.exited</code>. Once connected, <code>exit_handler</code> gets |
| called when the inferior exits. The argument <dfn>event</dfn> in this example is |
| of type <code>gdb.ExitedEvent</code>. As you can see in the example the |
| <code>ExitedEvent</code> object has an attribute which indicates the exit code of |
| the inferior. |
| |
| <p>The following is a listing of the event registries that are available and |
| details of the events they emit: |
| |
| <dl> |
| <dt><code>events.cont</code><dd>Emits <code>gdb.ThreadEvent</code>. |
| |
| <p>Some events can be thread specific when <span class="sc">gdb</span> is running in non-stop |
| mode. When represented in Python, these events all extend |
| <code>gdb.ThreadEvent</code>. Note, this event is not emitted directly; instead, |
| events which are emitted by this or other modules might extend this event. |
| Examples of these events are <code>gdb.BreakpointEvent</code> and |
| <code>gdb.ContinueEvent</code>. |
| |
| <div class="defun"> |
| — Variable: <b>ThreadEvent.inferior_thread</b><var><a name="index-ThreadEvent_002einferior_005fthread-2074"></a></var><br> |
| <blockquote> <p>In non-stop mode this attribute will be set to the specific thread which was |
| involved in the emitted event. Otherwise, it will be set to <code>None</code>. |
| </p></blockquote></div> |
| |
| <p>Emits <code>gdb.ContinueEvent</code> which extends <code>gdb.ThreadEvent</code>. |
| |
| <p>This event indicates that the inferior has been continued after a stop. For |
| inherited attribute refer to <code>gdb.ThreadEvent</code> above. |
| |
| <br><dt><code>events.exited</code><dd>Emits <code>events.ExitedEvent</code> which indicates that the inferior has exited. |
| <code>events.ExitedEvent</code> has two attributes: |
| |
| <div class="defun"> |
| — Variable: <b>ExitedEvent.exit_code</b><var><a name="index-ExitedEvent_002eexit_005fcode-2075"></a></var><br> |
| <blockquote> <p>An integer representing the exit code, if available, which the inferior |
| has returned. (The exit code could be unavailable if, for example, |
| <span class="sc">gdb</span> detaches from the inferior.) If the exit code is unavailable, |
| the attribute does not exist. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Variable: <b>ExitedEvent.inferior</b><var><a name="index-ExitedEvent_002einferior-2076"></a></var><br> |
| <blockquote> <p>A reference to the inferior which triggered the <code>exited</code> event. |
| </p></blockquote></div> |
| |
| <br><dt><code>events.stop</code><dd>Emits <code>gdb.StopEvent</code> which extends <code>gdb.ThreadEvent</code>. |
| |
| <p>Indicates that the inferior has stopped. All events emitted by this registry |
| extend StopEvent. As a child of <code>gdb.ThreadEvent</code>, <code>gdb.StopEvent</code> |
| will indicate the stopped thread when <span class="sc">gdb</span> is running in non-stop |
| mode. Refer to <code>gdb.ThreadEvent</code> above for more details. |
| |
| <p>Emits <code>gdb.SignalEvent</code> which extends <code>gdb.StopEvent</code>. |
| |
| <p>This event indicates that the inferior or one of its threads has received as |
| signal. <code>gdb.SignalEvent</code> has the following attributes: |
| |
| <div class="defun"> |
| — Variable: <b>SignalEvent.stop_signal</b><var><a name="index-SignalEvent_002estop_005fsignal-2077"></a></var><br> |
| <blockquote> <p>A string representing the signal received by the inferior. A list of possible |
| signal values can be obtained by running the command <code>info signals</code> in |
| the <span class="sc">gdb</span> command prompt. |
| </p></blockquote></div> |
| |
| <p>Also emits <code>gdb.BreakpointEvent</code> which extends <code>gdb.StopEvent</code>. |
| |
| <p><code>gdb.BreakpointEvent</code> event indicates that one or more breakpoints have |
| been hit, and has the following attributes: |
| |
| <div class="defun"> |
| — Variable: <b>BreakpointEvent.breakpoints</b><var><a name="index-BreakpointEvent_002ebreakpoints-2078"></a></var><br> |
| <blockquote> <p>A sequence containing references to all the breakpoints (type |
| <code>gdb.Breakpoint</code>) that were hit. |
| See <a href="Breakpoints-In-Python.html#Breakpoints-In-Python">Breakpoints In Python</a>, for details of the <code>gdb.Breakpoint</code> object. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Variable: <b>BreakpointEvent.breakpoint</b><var><a name="index-BreakpointEvent_002ebreakpoint-2079"></a></var><br> |
| <blockquote> <p>A reference to the first breakpoint that was hit. |
| This function is maintained for backward compatibility and is now deprecated |
| in favor of the <code>gdb.BreakpointEvent.breakpoints</code> attribute. |
| </p></blockquote></div> |
| |
| <br><dt><code>events.new_objfile</code><dd>Emits <code>gdb.NewObjFileEvent</code> which indicates that a new object file has |
| been loaded by <span class="sc">gdb</span>. <code>gdb.NewObjFileEvent</code> has one attribute: |
| |
| <div class="defun"> |
| — Variable: <b>NewObjFileEvent.new_objfile</b><var><a name="index-NewObjFileEvent_002enew_005fobjfile-2080"></a></var><br> |
| <blockquote> <p>A reference to the object file (<code>gdb.Objfile</code>) which has been loaded. |
| See <a href="Objfiles-In-Python.html#Objfiles-In-Python">Objfiles In Python</a>, for details of the <code>gdb.Objfile</code> object. |
| </p></blockquote></div> |
| |
| <br><dt><code>events.clear_objfiles</code><dd>Emits <code>gdb.ClearObjFilesEvent</code> which indicates that the list of object |
| files for a program space has been reset. |
| <code>gdb.ClearObjFilesEvent</code> has one attribute: |
| |
| <div class="defun"> |
| — Variable: <b>ClearObjFilesEvent.progspace</b><var><a name="index-ClearObjFilesEvent_002eprogspace-2081"></a></var><br> |
| <blockquote> <p>A reference to the program space (<code>gdb.Progspace</code>) whose objfile list has |
| been cleared. See <a href="Progspaces-In-Python.html#Progspaces-In-Python">Progspaces In Python</a>. |
| </p></blockquote></div> |
| |
| <br><dt><code>events.inferior_call</code><dd>Emits events just before and after a function in the inferior is |
| called by <span class="sc">gdb</span>. Before an inferior call, this emits an event |
| of type <code>gdb.InferiorCallPreEvent</code>, and after an inferior call, |
| this emits an event of type <code>gdb.InferiorCallPostEvent</code>. |
| |
| |
| <a name="index-gdb_002eInferiorCallPreEvent-2082"></a> |
| <dl><dt><code>gdb.InferiorCallPreEvent</code><dd>Indicates that a function in the inferior is about to be called. |
| |
| <div class="defun"> |
| — Variable: <b>InferiorCallPreEvent.ptid</b><var><a name="index-InferiorCallPreEvent_002eptid-2083"></a></var><br> |
| <blockquote> <p>The thread in which the call will be run. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Variable: <b>InferiorCallPreEvent.address</b><var><a name="index-InferiorCallPreEvent_002eaddress-2084"></a></var><br> |
| <blockquote> <p>The location of the function to be called. |
| </p></blockquote></div> |
| |
| <p><a name="index-gdb_002eInferiorCallPostEvent-2085"></a><br><dt><code>gdb.InferiorCallPostEvent</code><dd>Indicates that a function in the inferior has just been called. |
| |
| <div class="defun"> |
| — Variable: <b>InferiorCallPostEvent.ptid</b><var><a name="index-InferiorCallPostEvent_002eptid-2086"></a></var><br> |
| <blockquote> <p>The thread in which the call was run. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Variable: <b>InferiorCallPostEvent.address</b><var><a name="index-InferiorCallPostEvent_002eaddress-2087"></a></var><br> |
| <blockquote> <p>The location of the function that was called. |
| </p></blockquote></div> |
| </dl> |
| |
| <br><dt><code>events.memory_changed</code><dd>Emits <code>gdb.MemoryChangedEvent</code> which indicates that the memory of the |
| inferior has been modified by the <span class="sc">gdb</span> user, for instance via a |
| command like <code>set *addr = value</code><!-- /@w -->. The event has the following |
| attributes: |
| |
| <div class="defun"> |
| — Variable: <b>MemoryChangedEvent.address</b><var><a name="index-MemoryChangedEvent_002eaddress-2088"></a></var><br> |
| <blockquote> <p>The start address of the changed region. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Variable: <b>MemoryChangedEvent.length</b><var><a name="index-MemoryChangedEvent_002elength-2089"></a></var><br> |
| <blockquote> <p>Length in bytes of the changed region. |
| </p></blockquote></div> |
| |
| <br><dt><code>events.register_changed</code><dd>Emits <code>gdb.RegisterChangedEvent</code> which indicates that a register in the |
| inferior has been modified by the <span class="sc">gdb</span> user. |
| |
| <div class="defun"> |
| — Variable: <b>RegisterChangedEvent.frame</b><var><a name="index-RegisterChangedEvent_002eframe-2090"></a></var><br> |
| <blockquote> <p>A gdb.Frame object representing the frame in which the register was modified. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Variable: <b>RegisterChangedEvent.regnum</b><var><a name="index-RegisterChangedEvent_002eregnum-2091"></a></var><br> |
| <blockquote> <p>Denotes which register was modified. |
| </p></blockquote></div> |
| |
| <br><dt><code>events.breakpoint_created</code><dd>This is emitted when a new breakpoint has been created. The argument |
| that is passed is the new <code>gdb.Breakpoint</code> object. |
| |
| <br><dt><code>events.breakpoint_modified</code><dd>This is emitted when a breakpoint has been modified in some way. The |
| argument that is passed is the new <code>gdb.Breakpoint</code> object. |
| |
| <br><dt><code>events.breakpoint_deleted</code><dd>This is emitted when a breakpoint has been deleted. The argument that |
| is passed is the <code>gdb.Breakpoint</code> object. When this event is |
| emitted, the <code>gdb.Breakpoint</code> object will already be in its |
| invalid state; that is, the <code>is_valid</code> method will return |
| <code>False</code>. |
| |
| <br><dt><code>events.before_prompt</code><dd>This event carries no payload. It is emitted each time <span class="sc">gdb</span> |
| presents a prompt to the user. |
| |
| <br><dt><code>events.new_inferior</code><dd>This is emitted when a new inferior is created. Note that the |
| inferior is not necessarily running; in fact, it may not even have an |
| associated executable. |
| |
| <p>The event is of type <code>gdb.NewInferiorEvent</code>. This has a single |
| attribute: |
| |
| <div class="defun"> |
| — Variable: <b>NewInferiorEvent.inferior</b><var><a name="index-NewInferiorEvent_002einferior-2092"></a></var><br> |
| <blockquote> <p>The new inferior, a <code>gdb.Inferior</code> object. |
| </p></blockquote></div> |
| |
| <br><dt><code>events.inferior_deleted</code><dd>This is emitted when an inferior has been deleted. Note that this is |
| not the same as process exit; it is notified when the inferior itself |
| is removed, say via <code>remove-inferiors</code>. |
| |
| <p>The event is of type <code>gdb.InferiorDeletedEvent</code>. This has a single |
| attribute: |
| |
| <div class="defun"> |
| — Variable: <b>NewInferiorEvent.inferior</b><var><a name="index-NewInferiorEvent_002einferior-2093"></a></var><br> |
| <blockquote> <p>The inferior that is being removed, a <code>gdb.Inferior</code> object. |
| </p></blockquote></div> |
| |
| <br><dt><code>events.new_thread</code><dd>This is emitted when <span class="sc">gdb</span> notices a new thread. The event is of |
| type <code>gdb.NewThreadEvent</code>, which extends <code>gdb.ThreadEvent</code>. |
| This has a single attribute: |
| |
| <div class="defun"> |
| — Variable: <b>NewThreadEvent.inferior_thread</b><var><a name="index-NewThreadEvent_002einferior_005fthread-2094"></a></var><br> |
| <blockquote> <p>The new thread. |
| </p></blockquote></div> |
| |
| </dl> |
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