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134 lines
6.5 KiB
HTML
134 lines
6.5 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Free Software" and "Free Software Needs
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Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
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and with the Back-Cover Texts as in (a) below.
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(a) The FSF's Back-Cover Text is: "You are free to copy and modify
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this GNU Manual. Buying copies from GNU Press supports the FSF in
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developing GNU and promoting software freedom." -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Trace State Variables (Debugging with GDB)</title>
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<meta name="description" content="Trace State Variables (Debugging with GDB)">
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<meta name="keywords" content="Trace State Variables (Debugging with GDB)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Set-Tracepoints.html#Set-Tracepoints" rel="up" title="Set Tracepoints">
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<link href="Tracepoint-Actions.html#Tracepoint-Actions" rel="next" title="Tracepoint Actions">
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<link href="Tracepoint-Conditions.html#Tracepoint-Conditions" rel="prev" title="Tracepoint Conditions">
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<style type="text/css">
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Trace-State-Variables"></a>
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<div class="header">
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<p>
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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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</div>
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<hr>
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<a name="Trace-State-Variables-1"></a>
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<h4 class="subsection">13.1.5 Trace State Variables</h4>
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<a name="index-trace-state-variables"></a>
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<p>A <em>trace state variable</em> is a special type of variable that is
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created and managed by target-side code. The syntax is the same as
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that for GDB’s convenience variables (a string prefixed with “$”),
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but they are stored on the target. They must be created explicitly,
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using a <code>tvariable</code> command. They are always 64-bit signed
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integers.
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</p>
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<p>Trace state variables are remembered by <small>GDB</small>, and downloaded
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to the target along with tracepoint information when the trace
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experiment starts. There are no intrinsic limits on the number of
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trace state variables, beyond memory limitations of the target.
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</p>
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<a name="index-convenience-variables_002c-and-trace-state-variables"></a>
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<p>Although trace state variables are managed by the target, you can use
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them in print commands and expressions as if they were convenience
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variables; <small>GDB</small> will get the current value from the target
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while the trace experiment is running. Trace state variables share
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the same namespace as other “$” variables, which means that you
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cannot have trace state variables with names like <code>$23</code> or
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<code>$pc</code>, nor can you have a trace state variable and a convenience
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variable with the same name.
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</p>
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<dl compact="compact">
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<dt><code>tvariable $<var>name</var> [ = <var>expression</var> ]</code></dt>
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<dd><a name="index-tvariable"></a>
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<p>The <code>tvariable</code> command creates a new trace state variable named
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<code>$<var>name</var></code>, and optionally gives it an initial value of
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<var>expression</var>. The <var>expression</var> is evaluated when this command is
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entered; the result will be converted to an integer if possible,
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otherwise <small>GDB</small> will report an error. A subsequent
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<code>tvariable</code> command specifying the same name does not create a
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variable, but instead assigns the supplied initial value to the
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existing variable of that name, overwriting any previous initial
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value. The default initial value is 0.
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</p>
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</dd>
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<dt><code>info tvariables</code></dt>
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<dd><a name="index-info-tvariables"></a>
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<p>List all the trace state variables along with their initial values.
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Their current values may also be displayed, if the trace experiment is
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currently running.
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</p>
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</dd>
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<dt><code>delete tvariable <span class="roman">[</span> $<var>name</var> … <span class="roman">]</span></code></dt>
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<dd><a name="index-delete-tvariable"></a>
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<p>Delete the given trace state variables, or all of them if no arguments
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are specified.
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</p>
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</dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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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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</div>
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</body>
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</html>
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