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168 lines
9.4 KiB
HTML
168 lines
9.4 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>Breakpoints (Debugging with GDB)</title>
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<meta name="description" content="Breakpoints (Debugging with GDB)">
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<meta name="keywords" content="Breakpoints (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="Stopping.html#Stopping" rel="up" title="Stopping">
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<link href="Set-Breaks.html#Set-Breaks" rel="next" title="Set Breaks">
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<link href="Stopping.html#Stopping" rel="prev" title="Stopping">
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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="Breakpoints"></a>
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<div class="header">
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<p>
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Next: <a href="Continuing-and-Stepping.html#Continuing-and-Stepping" accesskey="n" rel="next">Continuing and Stepping</a>, Up: <a href="Stopping.html#Stopping" accesskey="u" rel="up">Stopping</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="Breakpoints_002c-Watchpoints_002c-and-Catchpoints"></a>
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<h3 class="section">5.1 Breakpoints, Watchpoints, and Catchpoints</h3>
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<a name="index-breakpoints"></a>
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<p>A <em>breakpoint</em> makes your program stop whenever a certain point in
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the program is reached. For each breakpoint, you can add conditions to
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control in finer detail whether your program stops. You can set
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breakpoints with the <code>break</code> command and its variants (see <a href="Set-Breaks.html#Set-Breaks">Setting Breakpoints</a>), to specify the place where your program
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should stop by line number, function name or exact address in the
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program.
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</p>
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<p>On some systems, you can set breakpoints in shared libraries before
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the executable is run.
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</p>
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<a name="index-watchpoints"></a>
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<a name="index-data-breakpoints"></a>
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<a name="index-memory-tracing"></a>
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<a name="index-breakpoint-on-memory-address"></a>
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<a name="index-breakpoint-on-variable-modification"></a>
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<p>A <em>watchpoint</em> is a special breakpoint that stops your program
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when the value of an expression changes. The expression may be a value
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of a variable, or it could involve values of one or more variables
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combined by operators, such as ‘<samp>a + b</samp>’. This is sometimes called
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<em>data breakpoints</em>. You must use a different command to set
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watchpoints (see <a href="Set-Watchpoints.html#Set-Watchpoints">Setting Watchpoints</a>), but aside
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from that, you can manage a watchpoint like any other breakpoint: you
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enable, disable, and delete both breakpoints and watchpoints using the
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same commands.
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</p>
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<p>You can arrange to have values from your program displayed automatically
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whenever <small>GDB</small> stops at a breakpoint. See <a href="Auto-Display.html#Auto-Display">Automatic Display</a>.
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</p>
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<a name="index-catchpoints"></a>
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<a name="index-breakpoint-on-events"></a>
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<p>A <em>catchpoint</em> is another special breakpoint that stops your program
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when a certain kind of event occurs, such as the throwing of a C<tt>++</tt>
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exception or the loading of a library. As with watchpoints, you use a
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different command to set a catchpoint (see <a href="Set-Catchpoints.html#Set-Catchpoints">Setting
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Catchpoints</a>), but aside from that, you can manage a catchpoint like any
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other breakpoint. (To stop when your program receives a signal, use the
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<code>handle</code> command; see <a href="Signals.html#Signals">Signals</a>.)
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</p>
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<a name="index-breakpoint-numbers"></a>
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<a name="index-numbers-for-breakpoints"></a>
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<p><small>GDB</small> assigns a number to each breakpoint, watchpoint, or
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catchpoint when you create it; these numbers are successive integers
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starting with one. In many of the commands for controlling various
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features of breakpoints you use the breakpoint number to say which
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breakpoint you want to change. Each breakpoint may be <em>enabled</em> or
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<em>disabled</em>; if disabled, it has no effect on your program until you
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enable it again.
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</p>
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<a name="index-breakpoint-ranges"></a>
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<a name="index-breakpoint-lists"></a>
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<a name="index-ranges-of-breakpoints"></a>
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<a name="index-lists-of-breakpoints"></a>
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<p>Some <small>GDB</small> commands accept a space-separated list of breakpoints
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on which to operate. A list element can be either a single breakpoint number,
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like ‘<samp>5</samp>’, or a range of such numbers, like ‘<samp>5-7</samp>’.
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When a breakpoint list is given to a command, all breakpoints in that list
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are operated on.
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</p>
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<table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top">• <a href="Set-Breaks.html#Set-Breaks" accesskey="1">Set Breaks</a>:</td><td> </td><td align="left" valign="top">Setting breakpoints
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Set-Watchpoints.html#Set-Watchpoints" accesskey="2">Set Watchpoints</a>:</td><td> </td><td align="left" valign="top">Setting watchpoints
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Set-Catchpoints.html#Set-Catchpoints" accesskey="3">Set Catchpoints</a>:</td><td> </td><td align="left" valign="top">Setting catchpoints
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Delete-Breaks.html#Delete-Breaks" accesskey="4">Delete Breaks</a>:</td><td> </td><td align="left" valign="top">Deleting breakpoints
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Disabling.html#Disabling" accesskey="5">Disabling</a>:</td><td> </td><td align="left" valign="top">Disabling breakpoints
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Conditions.html#Conditions" accesskey="6">Conditions</a>:</td><td> </td><td align="left" valign="top">Break conditions
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Break-Commands.html#Break-Commands" accesskey="7">Break Commands</a>:</td><td> </td><td align="left" valign="top">Breakpoint command lists
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Dynamic-Printf.html#Dynamic-Printf" accesskey="8">Dynamic Printf</a>:</td><td> </td><td align="left" valign="top">Dynamic printf
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Save-Breakpoints.html#Save-Breakpoints" accesskey="9">Save Breakpoints</a>:</td><td> </td><td align="left" valign="top">How to save breakpoints in a file
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Static-Probe-Points.html#Static-Probe-Points">Static Probe Points</a>:</td><td> </td><td align="left" valign="top">Listing static probe points
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Error-in-Breakpoints.html#Error-in-Breakpoints">Error in Breakpoints</a>:</td><td> </td><td align="left" valign="top">“Cannot insert breakpoints”
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Breakpoint_002drelated-Warnings.html#Breakpoint_002drelated-Warnings">Breakpoint-related Warnings</a>:</td><td> </td><td align="left" valign="top">“Breakpoint address adjusted...”
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</td></tr>
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</table>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Continuing-and-Stepping.html#Continuing-and-Stepping" accesskey="n" rel="next">Continuing and Stepping</a>, Up: <a href="Stopping.html#Stopping" accesskey="u" rel="up">Stopping</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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