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 Up:&nbsp;<a rel="up" accesskey="u" href="Python-API.html#Python-API">Python API</a>
 <hr>
 </div>

 <h5 class="subsubsection">23.2.2.19 Recordings In Python</h5>

 <p><a name="index-recordings-in-python-2109"></a>
 The following recordings-related functions
 (see <a href="Process-Record-and-Replay.html#Process-Record-and-Replay">Process Record and Replay</a>) are available in the <code>gdb</code>
 module:

 <div class="defun">
 &mdash; Function: <b>gdb.start_recording</b> (<span class="roman">[</span><var>method</var><span class="roman">]</span><var>, </var><span class="roman">[</span><var>format</var><span class="roman">]</span>)<var><a name="index-gdb_002estart_005frecording-2110"></a></var><br>
 <blockquote><p>Start a recording using the given <var>method</var> and <var>format</var>.  If
 no <var>format</var> is given, the default format for the recording method
 is used.  If no <var>method</var> is given, the default method will be used.
 Returns a <code>gdb.Record</code> object on success.  Throw an exception on
 failure.

         <p>The following strings can be passed as <var>method</var>:

           <ul>
 <li><code>"full"</code>
 <li><code>"btrace"</code>: Possible values for <var>format</var>: <code>"pt"</code>,
 <code>"bts"</code> or leave out for default format.
 </ul>
         </p></blockquote></div>

 <div class="defun">
 &mdash; Function: <b>gdb.current_recording</b> ()<var><a name="index-gdb_002ecurrent_005frecording-2111"></a></var><br>
 <blockquote><p>Access a currently running recording.  Return a <code>gdb.Record</code>
 object on success.  Return <code>None</code> if no recording is currently
 active.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Function: <b>gdb.stop_recording</b> ()<var><a name="index-gdb_002estop_005frecording-2112"></a></var><br>
 <blockquote><p>Stop the current recording.  Throw an exception if no recording is
 currently active.  All record objects become invalid after this call.
 </p></blockquote></div>

    <p>A <code>gdb.Record</code> object has the following attributes:

 <div class="defun">
 &mdash; Variable: <b>Record.method</b><var><a name="index-Record_002emethod-2113"></a></var><br>
 <blockquote><p>A string with the current recording method, e.g. <code>full</code> or
 <code>btrace</code>.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>Record.format</b><var><a name="index-Record_002eformat-2114"></a></var><br>
 <blockquote><p>A string with the current recording format, e.g. <code>bt</code>, <code>pts</code> or
 <code>None</code>.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>Record.begin</b><var><a name="index-Record_002ebegin-2115"></a></var><br>
 <blockquote><p>A method specific instruction object representing the first instruction
 in this recording.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>Record.end</b><var><a name="index-Record_002eend-2116"></a></var><br>
 <blockquote><p>A method specific instruction object representing the current
 instruction, that is not actually part of the recording.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>Record.replay_position</b><var><a name="index-Record_002ereplay_005fposition-2117"></a></var><br>
 <blockquote><p>The instruction representing the current replay position.  If there is
 no replay active, this will be <code>None</code>.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>Record.instruction_history</b><var><a name="index-Record_002einstruction_005fhistory-2118"></a></var><br>
 <blockquote><p>A list with all recorded instructions.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>Record.function_call_history</b><var><a name="index-Record_002efunction_005fcall_005fhistory-2119"></a></var><br>
 <blockquote><p>A list with all recorded function call segments.
 </p></blockquote></div>

    <p>A <code>gdb.Record</code> object has the following methods:

 <div class="defun">
 &mdash; Function: <b>Record.goto</b> (<var>instruction</var>)<var><a name="index-Record_002egoto-2120"></a></var><br>
 <blockquote><p>Move the replay position to the given <var>instruction</var>.
 </p></blockquote></div>

    <p>The common <code>gdb.Instruction</code> class that recording method specific
 instruction objects inherit from, has the following attributes:

 <div class="defun">
 &mdash; Variable: <b>Instruction.pc</b><var><a name="index-Instruction_002epc-2121"></a></var><br>
 <blockquote><p>An integer representing this instruction's address.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>Instruction.data</b><var><a name="index-Instruction_002edata-2122"></a></var><br>
 <blockquote><p>A buffer with the raw instruction data.  In Python 3, the return value is a
 <code>memoryview</code> object.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>Instruction.decoded</b><var><a name="index-Instruction_002edecoded-2123"></a></var><br>
 <blockquote><p>A human readable string with the disassembled instruction.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>Instruction.size</b><var><a name="index-Instruction_002esize-2124"></a></var><br>
 <blockquote><p>The size of the instruction in bytes.
 </p></blockquote></div>

    <p>Additionally <code>gdb.RecordInstruction</code> has the following attributes:

 <div class="defun">
 &mdash; Variable: <b>RecordInstruction.number</b><var><a name="index-RecordInstruction_002enumber-2125"></a></var><br>
 <blockquote><p>An integer identifying this instruction.  <code>number</code> corresponds to
 the numbers seen in <code>record instruction-history</code>
 (see <a href="Process-Record-and-Replay.html#Process-Record-and-Replay">Process Record and Replay</a>).
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordInstruction.sal</b><var><a name="index-RecordInstruction_002esal-2126"></a></var><br>
 <blockquote><p>A <code>gdb.Symtab_and_line</code> object representing the associated symtab
 and line of this instruction.  May be <code>None</code> if no debug information is
 available.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordInstruction.is_speculative</b><var><a name="index-RecordInstruction_002eis_005fspeculative-2127"></a></var><br>
 <blockquote><p>A boolean indicating whether the instruction was executed speculatively.
 </p></blockquote></div>

    <p>If an error occured during recording or decoding a recording, this error is
 represented by a <code>gdb.RecordGap</code> object in the instruction list.  It has
 the following attributes:

 <div class="defun">
 &mdash; Variable: <b>RecordGap.number</b><var><a name="index-RecordGap_002enumber-2128"></a></var><br>
 <blockquote><p>An integer identifying this gap.  <code>number</code> corresponds to the numbers seen
 in <code>record instruction-history</code> (see <a href="Process-Record-and-Replay.html#Process-Record-and-Replay">Process Record and Replay</a>).
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordGap.error_code</b><var><a name="index-RecordGap_002eerror_005fcode-2129"></a></var><br>
 <blockquote><p>A numerical representation of the reason for the gap.  The value is specific to
 the current recording method.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordGap.error_string</b><var><a name="index-RecordGap_002eerror_005fstring-2130"></a></var><br>
 <blockquote><p>A human readable string with the reason for the gap.
 </p></blockquote></div>

    <p>A <code>gdb.RecordFunctionSegment</code> object has the following attributes:

 <div class="defun">
 &mdash; Variable: <b>RecordFunctionSegment.number</b><var><a name="index-RecordFunctionSegment_002enumber-2131"></a></var><br>
 <blockquote><p>An integer identifying this function segment.  <code>number</code> corresponds to
 the numbers seen in <code>record function-call-history</code>
 (see <a href="Process-Record-and-Replay.html#Process-Record-and-Replay">Process Record and Replay</a>).
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordFunctionSegment.symbol</b><var><a name="index-RecordFunctionSegment_002esymbol-2132"></a></var><br>
 <blockquote><p>A <code>gdb.Symbol</code> object representing the associated symbol.  May be
 <code>None</code> if no debug information is available.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordFunctionSegment.level</b><var><a name="index-RecordFunctionSegment_002elevel-2133"></a></var><br>
 <blockquote><p>An integer representing the function call's stack level.  May be
 <code>None</code> if the function call is a gap.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordFunctionSegment.instructions</b><var><a name="index-RecordFunctionSegment_002einstructions-2134"></a></var><br>
 <blockquote><p>A list of <code>gdb.RecordInstruction</code> or <code>gdb.RecordGap</code> objects
 associated with this function call.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordFunctionSegment.up</b><var><a name="index-RecordFunctionSegment_002eup-2135"></a></var><br>
 <blockquote><p>A <code>gdb.RecordFunctionSegment</code> object representing the caller's
 function segment.  If the call has not been recorded, this will be the
 function segment to which control returns.  If neither the call nor the
 return have been recorded, this will be <code>None</code>.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordFunctionSegment.prev</b><var><a name="index-RecordFunctionSegment_002eprev-2136"></a></var><br>
 <blockquote><p>A <code>gdb.RecordFunctionSegment</code> object representing the previous
 segment of this function call.  May be <code>None</code>.
 </p></blockquote></div>

 <div class="defun">
 &mdash; Variable: <b>RecordFunctionSegment.next</b><var><a name="index-RecordFunctionSegment_002enext-2137"></a></var><br>
 <blockquote><p>A <code>gdb.RecordFunctionSegment</code> object representing the next segment of
 this function call.  May be <code>None</code>.
 </p></blockquote></div>

    <p>The following example demonstrates the usage of these objects and
 functions to create a function that will rewind a record to the last
 time a function in a different file was executed.  This would typically
 be used to track the execution of user provided callback functions in a
 library which typically are not visible in a back trace.

 <pre class="smallexample">     def bringback ():
          rec = gdb.current_recording ()
          if not rec:
              return

          insn = rec.instruction_history
          if len (insn) == 0:
              return

          try:
              position = insn.index (rec.replay_position)
          except:
              position = -1
          try:
              filename = insn[position].sal.symtab.fullname ()
          except:
              filename = None

          for i in reversed (insn[:position]):
      	try:
                  current = i.sal.symtab.fullname ()
      	except:
                  current = None

              if filename == current:
                  continue

              rec.goto (i)
              return
 </pre>
    <p>Another possible application is to write a function that counts the
 number of code executions in a given line range.  This line range can
 contain parts of functions or span across several functions and is not
 limited to be contiguous.

 <pre class="smallexample">     def countrange (filename, linerange):
          count = 0

          def filter_only (file_name):
              for call in gdb.current_recording ().function_call_history:
                  try:
                      if file_name in call.symbol.symtab.fullname ():
                          yield call
                  except:
                      pass

          for c in filter_only (filename):
              for i in c.instructions:
                  try:
                      if i.sal.line in linerange:
                          count += 1
                          break;
                  except:
                          pass

          return count
 </pre>
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	Up: <a rel="up" accesskey="u" href="Python-API.html#Python-API">Python API</a>
	<hr>
	</div>

	<h5 class="subsubsection">23.2.2.19 Recordings In Python</h5>

	<p><a name="index-recordings-in-python-2109"></a>
	The following recordings-related functions
	(see <a href="Process-Record-and-Replay.html#Process-Record-and-Replay">Process Record and Replay</a>) are available in the <code>gdb</code>
	module:

	<div class="defun">
	— Function: <b>gdb.start_recording</b> (<span class="roman">[</span><var>method</var><span class="roman">]</span><var>, </var><span class="roman">[</span><var>format</var><span class="roman">]</span>)<var><a name="index-gdb_002estart_005frecording-2110"></a></var><br>
	<blockquote><p>Start a recording using the given <var>method</var> and <var>format</var>. If
	no <var>format</var> is given, the default format for the recording method
	is used. If no <var>method</var> is given, the default method will be used.
	Returns a <code>gdb.Record</code> object on success. Throw an exception on
	failure.

	<p>The following strings can be passed as <var>method</var>:

	<ul>
	<li><code>"full"</code>
	<li><code>"btrace"</code>: Possible values for <var>format</var>: <code>"pt"</code>,
	<code>"bts"</code> or leave out for default format.
	</ul>
	</p></blockquote></div>

	<div class="defun">
	— Function: <b>gdb.current_recording</b> ()<var><a name="index-gdb_002ecurrent_005frecording-2111"></a></var><br>
	<blockquote><p>Access a currently running recording. Return a <code>gdb.Record</code>
	object on success. Return <code>None</code> if no recording is currently
	active.
	</p></blockquote></div>

	<div class="defun">
	— Function: <b>gdb.stop_recording</b> ()<var><a name="index-gdb_002estop_005frecording-2112"></a></var><br>
	<blockquote><p>Stop the current recording. Throw an exception if no recording is
	currently active. All record objects become invalid after this call.
	</p></blockquote></div>

	<p>A <code>gdb.Record</code> object has the following attributes:

	<div class="defun">
	— Variable: <b>Record.method</b><var><a name="index-Record_002emethod-2113"></a></var><br>
	<blockquote><p>A string with the current recording method, e.g. <code>full</code> or
	<code>btrace</code>.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>Record.format</b><var><a name="index-Record_002eformat-2114"></a></var><br>
	<blockquote><p>A string with the current recording format, e.g. <code>bt</code>, <code>pts</code> or
	<code>None</code>.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>Record.begin</b><var><a name="index-Record_002ebegin-2115"></a></var><br>
	<blockquote><p>A method specific instruction object representing the first instruction
	in this recording.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>Record.end</b><var><a name="index-Record_002eend-2116"></a></var><br>
	<blockquote><p>A method specific instruction object representing the current
	instruction, that is not actually part of the recording.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>Record.replay_position</b><var><a name="index-Record_002ereplay_005fposition-2117"></a></var><br>
	<blockquote><p>The instruction representing the current replay position. If there is
	no replay active, this will be <code>None</code>.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>Record.instruction_history</b><var><a name="index-Record_002einstruction_005fhistory-2118"></a></var><br>
	<blockquote><p>A list with all recorded instructions.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>Record.function_call_history</b><var><a name="index-Record_002efunction_005fcall_005fhistory-2119"></a></var><br>
	<blockquote><p>A list with all recorded function call segments.
	</p></blockquote></div>

	<p>A <code>gdb.Record</code> object has the following methods:

	<div class="defun">
	— Function: <b>Record.goto</b> (<var>instruction</var>)<var><a name="index-Record_002egoto-2120"></a></var><br>
	<blockquote><p>Move the replay position to the given <var>instruction</var>.
	</p></blockquote></div>

	<p>The common <code>gdb.Instruction</code> class that recording method specific
	instruction objects inherit from, has the following attributes:

	<div class="defun">
	— Variable: <b>Instruction.pc</b><var><a name="index-Instruction_002epc-2121"></a></var><br>
	<blockquote><p>An integer representing this instruction's address.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>Instruction.data</b><var><a name="index-Instruction_002edata-2122"></a></var><br>
	<blockquote><p>A buffer with the raw instruction data. In Python 3, the return value is a
	<code>memoryview</code> object.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>Instruction.decoded</b><var><a name="index-Instruction_002edecoded-2123"></a></var><br>
	<blockquote><p>A human readable string with the disassembled instruction.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>Instruction.size</b><var><a name="index-Instruction_002esize-2124"></a></var><br>
	<blockquote><p>The size of the instruction in bytes.
	</p></blockquote></div>

	<p>Additionally <code>gdb.RecordInstruction</code> has the following attributes:

	<div class="defun">
	— Variable: <b>RecordInstruction.number</b><var><a name="index-RecordInstruction_002enumber-2125"></a></var><br>
	<blockquote><p>An integer identifying this instruction. <code>number</code> corresponds to
	the numbers seen in <code>record instruction-history</code>
	(see <a href="Process-Record-and-Replay.html#Process-Record-and-Replay">Process Record and Replay</a>).
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordInstruction.sal</b><var><a name="index-RecordInstruction_002esal-2126"></a></var><br>
	<blockquote><p>A <code>gdb.Symtab_and_line</code> object representing the associated symtab
	and line of this instruction. May be <code>None</code> if no debug information is
	available.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordInstruction.is_speculative</b><var><a name="index-RecordInstruction_002eis_005fspeculative-2127"></a></var><br>
	<blockquote><p>A boolean indicating whether the instruction was executed speculatively.
	</p></blockquote></div>

	<p>If an error occured during recording or decoding a recording, this error is
	represented by a <code>gdb.RecordGap</code> object in the instruction list. It has
	the following attributes:

	<div class="defun">
	— Variable: <b>RecordGap.number</b><var><a name="index-RecordGap_002enumber-2128"></a></var><br>
	<blockquote><p>An integer identifying this gap. <code>number</code> corresponds to the numbers seen
	in <code>record instruction-history</code> (see <a href="Process-Record-and-Replay.html#Process-Record-and-Replay">Process Record and Replay</a>).
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordGap.error_code</b><var><a name="index-RecordGap_002eerror_005fcode-2129"></a></var><br>
	<blockquote><p>A numerical representation of the reason for the gap. The value is specific to
	the current recording method.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordGap.error_string</b><var><a name="index-RecordGap_002eerror_005fstring-2130"></a></var><br>
	<blockquote><p>A human readable string with the reason for the gap.
	</p></blockquote></div>

	<p>A <code>gdb.RecordFunctionSegment</code> object has the following attributes:

	<div class="defun">
	— Variable: <b>RecordFunctionSegment.number</b><var><a name="index-RecordFunctionSegment_002enumber-2131"></a></var><br>
	<blockquote><p>An integer identifying this function segment. <code>number</code> corresponds to
	the numbers seen in <code>record function-call-history</code>
	(see <a href="Process-Record-and-Replay.html#Process-Record-and-Replay">Process Record and Replay</a>).
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordFunctionSegment.symbol</b><var><a name="index-RecordFunctionSegment_002esymbol-2132"></a></var><br>
	<blockquote><p>A <code>gdb.Symbol</code> object representing the associated symbol. May be
	<code>None</code> if no debug information is available.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordFunctionSegment.level</b><var><a name="index-RecordFunctionSegment_002elevel-2133"></a></var><br>
	<blockquote><p>An integer representing the function call's stack level. May be
	<code>None</code> if the function call is a gap.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordFunctionSegment.instructions</b><var><a name="index-RecordFunctionSegment_002einstructions-2134"></a></var><br>
	<blockquote><p>A list of <code>gdb.RecordInstruction</code> or <code>gdb.RecordGap</code> objects
	associated with this function call.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordFunctionSegment.up</b><var><a name="index-RecordFunctionSegment_002eup-2135"></a></var><br>
	<blockquote><p>A <code>gdb.RecordFunctionSegment</code> object representing the caller's
	function segment. If the call has not been recorded, this will be the
	function segment to which control returns. If neither the call nor the
	return have been recorded, this will be <code>None</code>.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordFunctionSegment.prev</b><var><a name="index-RecordFunctionSegment_002eprev-2136"></a></var><br>
	<blockquote><p>A <code>gdb.RecordFunctionSegment</code> object representing the previous
	segment of this function call. May be <code>None</code>.
	</p></blockquote></div>

	<div class="defun">
	— Variable: <b>RecordFunctionSegment.next</b><var><a name="index-RecordFunctionSegment_002enext-2137"></a></var><br>
	<blockquote><p>A <code>gdb.RecordFunctionSegment</code> object representing the next segment of
	this function call. May be <code>None</code>.
	</p></blockquote></div>

	<p>The following example demonstrates the usage of these objects and
	functions to create a function that will rewind a record to the last
	time a function in a different file was executed. This would typically
	be used to track the execution of user provided callback functions in a
	library which typically are not visible in a back trace.

	<pre class="smallexample"> def bringback ():
	rec = gdb.current_recording ()
	if not rec:
	return

	insn = rec.instruction_history
	if len (insn) == 0:
	return

	try:
	position = insn.index (rec.replay_position)
	except:
	position = -1
	try:
	filename = insn[position].sal.symtab.fullname ()
	except:
	filename = None

	for i in reversed (insn[:position]):
	try:
	current = i.sal.symtab.fullname ()
	except:
	current = None

	if filename == current:
	continue

	rec.goto (i)
	return
	</pre>
	<p>Another possible application is to write a function that counts the
	number of code executions in a given line range. This line range can
	contain parts of functions or span across several functions and is not
	limited to be contiguous.

	<pre class="smallexample"> def countrange (filename, linerange):
	count = 0

	def filter_only (file_name):
	for call in gdb.current_recording ().function_call_history:
	try:
	if file_name in call.symbol.symtab.fullname ():
	yield call
	except:
	pass

	for c in filter_only (filename):
	for i in c.instructions:
	try:
	if i.sal.line in linerange:
	count += 1
	break;
	except:
	pass

	return count
	</pre>
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