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<h5 class="subsubsection">23.2.2.31 Finish Breakpoints</h5>

<p><a name="index-python-finish-breakpoints-2422"></a><a name="index-gdb_002eFinishBreakpoint-2423"></a>
A finish breakpoint is a temporary breakpoint set at the return address of
a frame, based on the <code>finish</code> command.  <code>gdb.FinishBreakpoint</code>
extends <code>gdb.Breakpoint</code>.  The underlying breakpoint will be disabled
and deleted when the execution will run out of the breakpoint scope (i.e. 
<code>Breakpoint.stop</code> or <code>FinishBreakpoint.out_of_scope</code> triggered). 
Finish breakpoints are thread specific and must be create with the right
thread selected.

<div class="defun">
&mdash; Function: <b>FinishBreakpoint.__init__</b> (<span class="roman">[</span><var>frame</var><span class="roman">]</span> <span class="roman">[</span><var>, internal</var><span class="roman">]</span>)<var><a name="index-FinishBreakpoint_002e_005f_005finit_005f_005f-2424"></a></var><br>
<blockquote><p>Create a finish breakpoint at the return address of the <code>gdb.Frame</code>
object <var>frame</var>.  If <var>frame</var> is not provided, this defaults to the
newest frame.  The optional <var>internal</var> argument allows the breakpoint to
become invisible to the user.  See <a href="Breakpoints-In-Python.html#Breakpoints-In-Python">Breakpoints In Python</a>, for further
details about this argument. 
</p></blockquote></div>

<div class="defun">
&mdash; Function: <b>FinishBreakpoint.out_of_scope</b> (<var>self</var>)<var><a name="index-FinishBreakpoint_002eout_005fof_005fscope-2425"></a></var><br>
<blockquote><p>In some circumstances (e.g. <code>longjmp</code>, C<tt>++</tt> exceptions, <span class="sc">gdb</span>
<code>return</code> command, <small class="dots">...</small>), a function may not properly terminate, and
thus never hit the finish breakpoint.  When <span class="sc">gdb</span> notices such a
situation, the <code>out_of_scope</code> callback will be triggered.

        <p>You may want to sub-class <code>gdb.FinishBreakpoint</code> and override this
method:

     <pre class="smallexample">          class MyFinishBreakpoint (gdb.FinishBreakpoint)
              def stop (self):
                  print "normal finish"
                  return True
          
              def out_of_scope ():
                  print "abnormal finish"
</pre>
        </blockquote></div>

<div class="defun">
&mdash; Variable: <b>FinishBreakpoint.return_value</b><var><a name="index-FinishBreakpoint_002ereturn_005fvalue-2426"></a></var><br>
<blockquote><p>When <span class="sc">gdb</span> is stopped at a finish breakpoint and the frame
used to build the <code>gdb.FinishBreakpoint</code> object had debug symbols, this
attribute will contain a <code>gdb.Value</code> object corresponding to the return
value of the function.  The value will be <code>None</code> if the function return
type is <code>void</code> or if the return value was not computable.  This attribute
is not writable. 
</p></blockquote></div>

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