1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- Copyright (C) 1988-2021 Free Software Foundation, Inc. 4 5Permission is granted to copy, distribute and/or modify this document 6under the terms of the GNU Free Documentation License, Version 1.3 or 7any later version published by the Free Software Foundation; with the 8Invariant Sections being "Free Software" and "Free Software Needs 9Free Documentation", with the Front-Cover Texts being "A GNU Manual," 10and with the Back-Cover Texts as in (a) below. 11 12(a) The FSF's Back-Cover Text is: "You are free to copy and modify 13this GNU Manual. 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The syntax is the same as 76that for GDB’s convenience variables (a string prefixed with “$”), 77but they are stored on the target. They must be created explicitly, 78using a <code>tvariable</code> command. They are always 64-bit signed 79integers. 80</p> 81<p>Trace state variables are remembered by <small>GDB</small>, and downloaded 82to the target along with tracepoint information when the trace 83experiment starts. There are no intrinsic limits on the number of 84trace state variables, beyond memory limitations of the target. 85</p> 86<a name="index-convenience-variables_002c-and-trace-state-variables"></a> 87<p>Although trace state variables are managed by the target, you can use 88them in print commands and expressions as if they were convenience 89variables; <small>GDB</small> will get the current value from the target 90while the trace experiment is running. Trace state variables share 91the same namespace as other “$” variables, which means that you 92cannot have trace state variables with names like <code>$23</code> or 93<code>$pc</code>, nor can you have a trace state variable and a convenience 94variable with the same name. 95</p> 96<dl compact="compact"> 97<dt><code>tvariable $<var>name</var> [ = <var>expression</var> ]</code></dt> 98<dd><a name="index-tvariable"></a> 99<p>The <code>tvariable</code> command creates a new trace state variable named 100<code>$<var>name</var></code>, and optionally gives it an initial value of 101<var>expression</var>. The <var>expression</var> is evaluated when this command is 102entered; the result will be converted to an integer if possible, 103otherwise <small>GDB</small> will report an error. A subsequent 104<code>tvariable</code> command specifying the same name does not create a 105variable, but instead assigns the supplied initial value to the 106existing variable of that name, overwriting any previous initial 107value. The default initial value is 0. 108</p> 109</dd> 110<dt><code>info tvariables</code></dt> 111<dd><a name="index-info-tvariables"></a> 112<p>List all the trace state variables along with their initial values. 113Their current values may also be displayed, if the trace experiment is 114currently running. 115</p> 116</dd> 117<dt><code>delete tvariable <span class="roman">[</span> $<var>name</var> … <span class="roman">]</span></code></dt> 118<dd><a name="index-delete-tvariable"></a> 119<p>Delete the given trace state variables, or all of them if no arguments 120are specified. 121</p> 122</dd> 123</dl> 124 125<hr> 126<div class="header"> 127<p> 128Next: <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="previous">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> 129</div> 130 131 132 133</body> 134</html> 135