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diff --git a/share/doc/gdb/Context-management.html b/share/doc/gdb/Context-management.html new file mode 100644 index 0000000..ef30727 --- /dev/null +++ b/share/doc/gdb/Context-management.html @@ -0,0 +1,155 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Free Software" and "Free Software Needs +Free Documentation", with the Front-Cover Texts being "A GNU Manual," +and with the Back-Cover Texts as in (a) below. + +(a) The FSF's Back-Cover Text is: "You are free to copy and modify +this GNU Manual. Buying copies from GNU Press supports the FSF in +developing GNU and promoting software freedom." --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Debugging with GDB: Context management</title> + +<meta name="description" content="Debugging with GDB: Context management"> +<meta name="keywords" content="Debugging with GDB: Context management"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="GDB_002fMI-General-Design.html#GDB_002fMI-General-Design" rel="up" title="GDB/MI General Design"> +<link href="Asynchronous-and-non_002dstop-modes.html#Asynchronous-and-non_002dstop-modes" rel="next" title="Asynchronous and non-stop modes"> +<link href="GDB_002fMI-General-Design.html#GDB_002fMI-General-Design" rel="previous" title="GDB/MI General Design"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Context-management"></a> +<div class="header"> +<p> +Next: <a href="Asynchronous-and-non_002dstop-modes.html#Asynchronous-and-non_002dstop-modes" accesskey="n" rel="next">Asynchronous and non-stop modes</a>, Up: <a href="GDB_002fMI-General-Design.html#GDB_002fMI-General-Design" accesskey="u" rel="up">GDB/MI General Design</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="Context-management-1"></a> +<h4 class="subsection">27.1.1 Context management</h4> + +<a name="Threads-and-Frames"></a> +<h4 class="subsubsection">27.1.1.1 Threads and Frames</h4> + +<p>In most cases when <small>GDB</small> accesses the target, this access is +done in context of a specific thread and frame (see <a href="Frames.html#Frames">Frames</a>). +Often, even when accessing global data, the target requires that a thread +be specified. The CLI interface maintains the selected thread and frame, +and supplies them to target on each command. This is convenient, +because a command line user would not want to specify that information +explicitly on each command, and because user interacts with +<small>GDB</small> via a single terminal, so no confusion is possible as +to what thread and frame are the current ones. +</p> +<p>In the case of MI, the concept of selected thread and frame is less +useful. First, a frontend can easily remember this information +itself. Second, a graphical frontend can have more than one window, +each one used for debugging a different thread, and the frontend might +want to access additional threads for internal purposes. This +increases the risk that by relying on implicitly selected thread, the +frontend may be operating on a wrong one. Therefore, each MI command +should explicitly specify which thread and frame to operate on. To +make it possible, each MI command accepts the ‘<samp>--thread</samp>’ and +‘<samp>--frame</samp>’ options, the value to each is <small>GDB</small> global +identifier for thread and frame to operate on. +</p> +<p>Usually, each top-level window in a frontend allows the user to select +a thread and a frame, and remembers the user selection for further +operations. However, in some cases <small>GDB</small> may suggest that the +current thread or frame be changed. For example, when stopping on a +breakpoint it is reasonable to switch to the thread where breakpoint is +hit. For another example, if the user issues the CLI ‘<samp>thread</samp>’ or +‘<samp>frame</samp>’ commands via the frontend, it is desirable to change the +frontend’s selection to the one specified by user. <small>GDB</small> +communicates the suggestion to change current thread and frame using the +‘<samp>=thread-selected</samp>’ notification. +</p> +<p>Note that historically, MI shares the selected thread with CLI, so +frontends used the <code>-thread-select</code> to execute commands in the +right context. However, getting this to work right is cumbersome. The +simplest way is for frontend to emit <code>-thread-select</code> command +before every command. This doubles the number of commands that need +to be sent. The alternative approach is to suppress <code>-thread-select</code> +if the selected thread in <small>GDB</small> is supposed to be identical to the +thread the frontend wants to operate on. However, getting this +optimization right can be tricky. In particular, if the frontend +sends several commands to <small>GDB</small>, and one of the commands changes the +selected thread, then the behaviour of subsequent commands will +change. So, a frontend should either wait for response from such +problematic commands, or explicitly add <code>-thread-select</code> for +all subsequent commands. No frontend is known to do this exactly +right, so it is suggested to just always pass the ‘<samp>--thread</samp>’ and +‘<samp>--frame</samp>’ options. +</p> +<a name="Language"></a> +<h4 class="subsubsection">27.1.1.2 Language</h4> + +<p>The execution of several commands depends on which language is selected. +By default, the current language (see <a href="Show.html#show-language">show language</a>) is used. +But for commands known to be language-sensitive, it is recommended +to use the ‘<samp>--language</samp>’ option. This option takes one argument, +which is the name of the language to use while executing the command. +For instance: +</p> +<div class="smallexample"> +<pre class="smallexample">-data-evaluate-expression --language c "sizeof (void*)" +^done,value="4" +(gdb) +</pre></div> + +<p>The valid language names are the same names accepted by the +‘<samp>set language</samp>’ command (see <a href="Manually.html#Manually">Manually</a>), excluding ‘<samp>auto</samp>’, +‘<samp>local</samp>’ or ‘<samp>unknown</samp>’. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Asynchronous-and-non_002dstop-modes.html#Asynchronous-and-non_002dstop-modes" accesskey="n" rel="next">Asynchronous and non-stop modes</a>, Up: <a href="GDB_002fMI-General-Design.html#GDB_002fMI-General-Design" accesskey="u" rel="up">GDB/MI General Design</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> + + + +</body> +</html> |