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116 lines
5.9 KiB
HTML
116 lines
5.9 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>The Ctrl-C Message (Debugging with GDB)</title>
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<meta name="description" content="The Ctrl-C Message (Debugging with GDB)">
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<meta name="keywords" content="The Ctrl-C Message (Debugging with GDB)">
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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="File_002dI_002fO-Remote-Protocol-Extension.html#File_002dI_002fO-Remote-Protocol-Extension" rel="up" title="File-I/O Remote Protocol Extension">
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<link href="Console-I_002fO.html#Console-I_002fO" rel="next" title="Console I/O">
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<link href="The-F-Reply-Packet.html#The-F-Reply-Packet" rel="prev" title="The F Reply Packet">
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</style>
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</head>
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<body lang="en">
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<a name="The-Ctrl_002dC-Message"></a>
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<div class="header">
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<p>
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Next: <a href="Console-I_002fO.html#Console-I_002fO" accesskey="n" rel="next">Console I/O</a>, Previous: <a href="The-F-Reply-Packet.html#The-F-Reply-Packet" accesskey="p" rel="prev">The F Reply Packet</a>, Up: <a href="File_002dI_002fO-Remote-Protocol-Extension.html#File_002dI_002fO-Remote-Protocol-Extension" accesskey="u" rel="up">File-I/O Remote Protocol Extension</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="The-Ctrl_002dC-Message-1"></a>
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<h4 class="subsection">E.13.5 The ‘<samp>Ctrl-C</samp>’ Message</h4>
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<a name="index-ctrl_002dc-message_002c-in-file_002di_002fo-protocol"></a>
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<p>If the ‘<samp>Ctrl-C</samp>’ flag is set in the <small>GDB</small>
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reply packet (see <a href="The-F-Reply-Packet.html#The-F-Reply-Packet">The F Reply Packet</a>),
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the target should behave as if it had
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gotten a break message. The meaning for the target is “system call
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interrupted by <code>SIGINT</code>”. Consequentially, the target should actually stop
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(as with a break message) and return to <small>GDB</small> with a <code>T02</code>
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packet.
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</p>
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<p>It’s important for the target to know in which
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state the system call was interrupted. There are two possible cases:
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</p>
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<ul>
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<li> The system call hasn’t been performed on the host yet.
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</li><li> The system call on the host has been finished.
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</li></ul>
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<p>These two states can be distinguished by the target by the value of the
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returned <code>errno</code>. If it’s the protocol representation of <code>EINTR</code>, the system
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call hasn’t been performed. This is equivalent to the <code>EINTR</code> handling
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on POSIX systems. In any other case, the target may presume that the
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system call has been finished — successfully or not — and should behave
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as if the break message arrived right after the system call.
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</p>
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<p><small>GDB</small> must behave reliably. If the system call has not been called
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yet, <small>GDB</small> may send the <code>F</code> reply immediately, setting <code>EINTR</code> as
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<code>errno</code> in the packet. If the system call on the host has been finished
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before the user requests a break, the full action must be finished by
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<small>GDB</small>. This requires sending <code>M</code> or <code>X</code> packets as necessary.
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The <code>F</code> packet may only be sent when either nothing has happened
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or the full action has been completed.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Console-I_002fO.html#Console-I_002fO" accesskey="n" rel="next">Console I/O</a>, Previous: <a href="The-F-Reply-Packet.html#The-F-Reply-Packet" accesskey="p" rel="prev">The F Reply Packet</a>, Up: <a href="File_002dI_002fO-Remote-Protocol-Extension.html#File_002dI_002fO-Remote-Protocol-Extension" accesskey="u" rel="up">File-I/O Remote Protocol Extension</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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