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diff --git a/share/doc/annotate/Limitations.html b/share/doc/annotate/Limitations.html new file mode 100644 index 0000000..829e3ad --- /dev/null +++ b/share/doc/annotate/Limitations.html @@ -0,0 +1,141 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1994-2023 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 no +Invariant Sections, with no Front-Cover Texts, and with no Back-Cover +Texts. A copy of the license is included in the section entitled "GNU +Free Documentation License". --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>GDB’s Obsolete Annotations: Limitations</title> + +<meta name="description" content="GDB’s Obsolete Annotations: Limitations"> +<meta name="keywords" content="GDB’s Obsolete Annotations: Limitations"> +<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="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="index.html#Top" rel="up" title="Top"> +<link href="Migrating-to-GDB_002fMI.html#Migrating-to-GDB_002fMI" rel="next" title="Migrating to GDB/MI"> +<link href="Annotations-Overview.html#Annotations-Overview" rel="previous" title="Annotations Overview"> +<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="Limitations"></a> +<div class="header"> +<p> +Next: <a href="Migrating-to-GDB_002fMI.html#Migrating-to-GDB_002fMI" accesskey="n" rel="next">Migrating to GDB/MI</a>, Previous: <a href="Annotations-Overview.html#Annotations-Overview" accesskey="p" rel="previous">Annotations Overview</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> +</div> +<hr> +<a name="Limitations-of-the-Annotation-Interface"></a> +<h2 class="chapter">2 Limitations of the Annotation Interface</h2> + +<p>The level two annotations mechanism is known to have a number of +technical and architectural limitations. As a consequence, in 2001, +with the release of <small>GDB</small> 5.1 and the addition of <small>GDB/MI</small>, +the annotation interface was marked as deprecated. +</p> +<p>This chapter discusses the known problems. +</p> +<a name="Dependant-on-CLI-output"></a> +<h3 class="section">2.1 Dependant on <small>CLI</small> output</h3> + +<p>The annotation interface works by interspersing markups with +<small>GDB</small> normal command-line interpreter output. Unfortunately, this +makes the annotation client dependant on not just the annotations, but +also the <small>CLI</small> output. This is because the client is forced to +assume that specific <small>GDB</small> commands provide specific information. +Any change to <small>GDB</small>’s <small>CLI</small> output modifies or removes that +information and, consequently, likely breaks the client. +</p> +<p>Since the <small>GDB/MI</small> output is independent of the <small>CLI</small>, it does not +have this problem. +</p> +<a name="Scalability"></a> +<h3 class="section">2.2 Scalability</h3> + +<p>The annotation interface relies on value annotations (see <a href="Value-Annotations.html#Value-Annotations">Value Annotations</a>) and the display mechanism as a way of obtaining up-to-date +value information. These mechanisms are not scalable. +</p> +<p>In a graphical environment, where many values can be displayed +simultaneously, a serious performance problem occurs when the client +tries to first extract from <small>GDB</small>, and then re-display, all those +values. The client should instead only request and update the values +that changed. +</p> +<p>The <small>GDB/MI</small> Variable Objects provide just that mechanism. +</p> +<a name="Correctness"></a> +<h3 class="section">2.3 Correctness</h3> + +<p>The annotation interface assumes that a variable’s value can only be +changed when the target is running. This assumption is not correct. A +single assignment to a single variable can result in the entire target, +and all displayed values, needing an update. +</p> +<p>The <small>GDB/MI</small> Variable Objects include a mechanism for efficiently +reporting such changes. +</p> +<a name="Reliability"></a> +<h3 class="section">2.4 Reliability</h3> + +<p>The <small>GDB/MI</small> interface includes a dedicated test directory +(<samp>gdb/gdb.mi</samp>), and any addition or fix to <small>GDB/MI</small> must include +testsuite changes. +</p> +<a name="Maintainability"></a> +<h3 class="section">2.5 Maintainability</h3> + +<p>The annotation mechanism was implemented by interspersing <small>CLI</small> print +statements with various annotations. As a consequence, any <small>CLI</small> +output change can alter the annotation output. +</p> +<p>Since the <small>GDB/MI</small> output is independent of the <small>CLI</small>, and the +<small>GDB/MI</small> is increasingly implemented independent of the <small>CLI</small> +code, its long term maintenance is much easier. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Migrating-to-GDB_002fMI.html#Migrating-to-GDB_002fMI" accesskey="n" rel="next">Migrating to GDB/MI</a>, Previous: <a href="Annotations-Overview.html#Annotations-Overview" accesskey="p" rel="previous">Annotations Overview</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> +</div> + + + +</body> +</html> |