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 <a name="Trace-State-Variables"></a>
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 </div>
 <hr>
 <a name="Trace-State-Variables-1"></a>
 <h4 class="subsection">13.1.5 Trace State Variables</h4>
 <a name="index-trace-state-variables"></a>

 <p>A <em>trace state variable</em> is a special type of variable that is
 created and managed by target-side code.  The syntax is the same as
 that for GDB&rsquo;s convenience variables (a string prefixed with &ldquo;$&rdquo;),
 but they are stored on the target.  They must be created explicitly,
 using a <code>tvariable</code> command.  They are always 64-bit signed
 integers.
 </p>
 <p>Trace state variables are remembered by <small>GDB</small>, and downloaded
 to the target along with tracepoint information when the trace
 experiment starts.  There are no intrinsic limits on the number of
 trace state variables, beyond memory limitations of the target.
 </p>
 <a name="index-convenience-variables_002c-and-trace-state-variables"></a>
 <p>Although trace state variables are managed by the target, you can use
 them in print commands and expressions as if they were convenience
 variables; <small>GDB</small> will get the current value from the target
 while the trace experiment is running.  Trace state variables share
 the same namespace as other &ldquo;$&rdquo; variables, which means that you
 cannot have trace state variables with names like <code>$23</code> or
 <code>$pc</code>, nor can you have a trace state variable and a convenience
 variable with the same name.
 </p>
 <dl compact="compact">
 <dt><code>tvariable $<var>name</var> [ = <var>expression</var> ]</code></dt>
 <dd><a name="index-tvariable"></a>
 <p>The <code>tvariable</code> command creates a new trace state variable named
 <code>$<var>name</var></code>, and optionally gives it an initial value of
 <var>expression</var>.  The <var>expression</var> is evaluated when this command is
 entered; the result will be converted to an integer if possible,
 otherwise <small>GDB</small> will report an error. A subsequent
 <code>tvariable</code> command specifying the same name does not create a
 variable, but instead assigns the supplied initial value to the
 existing variable of that name, overwriting any previous initial
 value. The default initial value is 0.
 </p>
 </dd>
 <dt><code>info tvariables</code></dt>
 <dd><a name="index-info-tvariables"></a>
 <p>List all the trace state variables along with their initial values.
 Their current values may also be displayed, if the trace experiment is
 currently running.
 </p>
 </dd>
 <dt><code>delete tvariable <span class="roman">[</span> $<var>name</var> &hellip; <span class="roman">]</span></code></dt>
 <dd><a name="index-delete-tvariable"></a>
 <p>Delete the given trace state variables, or all of them if no arguments
 are specified.
 </p>
 </dd>
 </dl>

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	<a name="Trace-State-Variables"></a>
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	<p>
	Next: <a href="Tracepoint-Actions.html#Tracepoint-Actions" accesskey="n" rel="next">Tracepoint Actions</a>, Previous: <a href="Tracepoint-Conditions.html#Tracepoint-Conditions" accesskey="p" rel="prev">Tracepoint Conditions</a>, Up: <a href="Set-Tracepoints.html#Set-Tracepoints" accesskey="u" rel="up">Set Tracepoints</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="Trace-State-Variables-1"></a>
	<h4 class="subsection">13.1.5 Trace State Variables</h4>
	<a name="index-trace-state-variables"></a>

	<p>A <em>trace state variable</em> is a special type of variable that is
	created and managed by target-side code. The syntax is the same as
	that for GDB’s convenience variables (a string prefixed with “$”),
	but they are stored on the target. They must be created explicitly,
	using a <code>tvariable</code> command. They are always 64-bit signed
	integers.
	</p>
	<p>Trace state variables are remembered by <small>GDB</small>, and downloaded
	to the target along with tracepoint information when the trace
	experiment starts. There are no intrinsic limits on the number of
	trace state variables, beyond memory limitations of the target.
	</p>
	<a name="index-convenience-variables_002c-and-trace-state-variables"></a>
	<p>Although trace state variables are managed by the target, you can use
	them in print commands and expressions as if they were convenience
	variables; <small>GDB</small> will get the current value from the target
	while the trace experiment is running. Trace state variables share
	the same namespace as other “$” variables, which means that you
	cannot have trace state variables with names like <code>$23</code> or
	<code>$pc</code>, nor can you have a trace state variable and a convenience
	variable with the same name.
	</p>
	<dl compact="compact">
	<dt><code>tvariable $<var>name</var> [ = <var>expression</var> ]</code></dt>
	<dd><a name="index-tvariable"></a>
	<p>The <code>tvariable</code> command creates a new trace state variable named
	<code>$<var>name</var></code>, and optionally gives it an initial value of
	<var>expression</var>. The <var>expression</var> is evaluated when this command is
	entered; the result will be converted to an integer if possible,
	otherwise <small>GDB</small> will report an error. A subsequent
	<code>tvariable</code> command specifying the same name does not create a
	variable, but instead assigns the supplied initial value to the
	existing variable of that name, overwriting any previous initial
	value. The default initial value is 0.
	</p>
	</dd>
	<dt><code>info tvariables</code></dt>
	<dd><a name="index-info-tvariables"></a>
	<p>List all the trace state variables along with their initial values.
	Their current values may also be displayed, if the trace experiment is
	currently running.
	</p>
	</dd>
	<dt><code>delete tvariable <span class="roman">[</span> $<var>name</var> … <span class="roman">]</span></code></dt>
	<dd><a name="index-delete-tvariable"></a>
	<p>Delete the given trace state variables, or all of them if no arguments
	are specified.
	</p>
	</dd>
	</dl>

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	Next: <a href="Tracepoint-Actions.html#Tracepoint-Actions" accesskey="n" rel="next">Tracepoint Actions</a>, Previous: <a href="Tracepoint-Conditions.html#Tracepoint-Conditions" accesskey="p" rel="prev">Tracepoint Conditions</a>, Up: <a href="Set-Tracepoints.html#Set-Tracepoints" accesskey="u" rel="up">Set Tracepoints</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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