Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 1 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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| 2 | <html xmlns="http://www.w3.org/1999/xhtml">
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| 3 | <head>
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| 4 | <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
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| 5 | <link href="style.css" rel="stylesheet" type="text/css" />
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| 6 | <title>LLDB Architecture</title>
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| 7 | </head>
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| 8 |
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| 9 | <body>
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| 10 | <div class="www_title">
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| 11 | The <strong>LLDB</strong> Debugger
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| 12 | </div>
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Eric Christopher | b7eb709 | 2010-06-10 05:35:26 +0000 | [diff] [blame] | 13 |
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 14 | <div id="container">
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| 15 | <div id="content">
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Chris Lattner | 3cc7b7f | 2010-06-11 23:07:14 +0000 | [diff] [blame] | 16 |
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| 17 | <!--#include virtual="sidebar.incl"-->
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| 18 |
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 19 | <div id="middle">
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| 20 | <div class="post">
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| 21 | <h1 class ="postheader">Architecture</h1>
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| 22 | <div class="postcontent">
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| 23 |
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| 24 | <p>LLDB is a large and complex codebase. This section will help you become more familiar with
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| 25 | the pieces that make up LLDB and give a general overview of the general architecture.</p>
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| 26 | </div>
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| 27 | <div class="postfooter"></div>
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| 28 | </div>
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| 29 | <div class="post">
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| 30 | <h1 class ="postheader">Code Layout</h1>
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| 31 | <div class="postcontent">
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| 32 |
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| 33 | <p>LLDB has many code groupings that makeup the source base:</p>
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| 34 | <ul>
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| 35 | <li><a href="#api">API</a></li>
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| 36 | <li><a href="#breakpoint">Breakpoint</a></li>
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| 37 | <li><a href="#commands">Commands</a></li>
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| 38 | <li><a href="#core">Core</a></li>
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| 39 | <li><a href="#expression">Expression</a></li>
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| 40 | <li><a href="#host">Host</a></li>
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| 41 | <li><a href="#interpreter">Interpreter</a></li>
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| 42 | <li><a href="#symbol">Symbol</a></li>
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| 43 | <li><a href="#targ">Target</a></li>
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| 44 | <li><a href="#utility">Utility</a></li>
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| 45 | </ul>
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| 46 | </div>
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| 47 | <div class="postfooter"></div>
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| 48 | </div>
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| 49 | <a name="api"></a>
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| 50 | <div class="post">
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| 51 | <h1 class ="postheader">API</h1>
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| 52 | <div class="postcontent">
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| 53 |
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| 54 | <p>The API folder contains the public interface to LLDB.</p>
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| 55 | <p>We are currently vending a C++ API. In order to be able to add
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| 56 | methods to this API and allow people to link to our classes,
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| 57 | we have certain rules that we must follow:</p>
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| 58 | <ul>
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| 59 | <li>Classes can't inherit from any other classes.</li>
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| 60 | <li>Classes can't contain virtual methods.</li>
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| 61 | <li>Classes should be compatible with script bridging utilities like <a href="http://www.swig.org/">swig</a>.</li>
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| 62 | <li>Classes should be lighweight and be backed by a single object pointer, shared pointer or global variable in the lldb_private.</li>
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| 63 | <li>The interface should be as minimal as possible in order to give a complete API.</li>
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| 64 | </ul>
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| 65 | <p>By adhering to these rules we should be able to continue to
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| 66 | vend a C++ API, and make changes to the API as any additional
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| 67 | methods added to these classes will just be a dynamic loader
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| 68 | lookup and they won't affect the class layout (since they
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| 69 | aren't virtual methods, and no members can be added to the
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Benjamin Kramer | 46a8cf3 | 2010-06-10 08:12:17 +0000 | [diff] [blame] | 70 | class).</p>
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 71 | </div>
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| 72 | <div class="postfooter"></div>
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| 73 | </div>
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| 74 | <a name="breakpoint"></a>
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| 75 | <div class="post">
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| 76 | <h1 class ="postheader">Breakpoint</h1>
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| 77 | <div class="postcontent">
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| 78 |
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| 79 | <p>A collection of classes that implement our breakpoint classes.
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| 80 | Breakpoints are resolved symbolically and always continue to
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Jason Molenda | 602ce7e | 2010-06-10 08:23:00 +0000 | [diff] [blame] | 81 | resolve themselves as your program runs. Whether settings breakpoints
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 82 | by file and line, by symbol name, by symbol regular expression,
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| 83 | or by address, breakpoints will keep trying to resolve new locations
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| 84 | each time shared libraries are loaded. Breakpoints will of course
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| 85 | unresolve themselves when shared libraries are unloaded. Breakpoints
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| 86 | can also be scoped to be set only in a specific shared library. By
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| 87 | default, breakpoints can be set in any shared library and will continue
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| 88 | to attempt to be resolved with each shared library load.</p>
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| 89 | <p>Breakpoint options can be set on the breakpoint,
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| 90 | or on the individual locations. This allows flexibility when dealing
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Benjamin Kramer | 46a8cf3 | 2010-06-10 08:12:17 +0000 | [diff] [blame] | 91 | with breakpoints and allows us to do what the user wants.</p>
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 92 | </div>
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| 93 | <div class="postfooter"></div>
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| 94 | </div>
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| 95 | <a name="commands"></a>
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| 96 | <div class="post">
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| 97 | <h1 class ="postheader">Commands</h1>
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| 98 | <div class="postcontent">
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| 99 |
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| 100 | <p>The command source files represent objects that implement
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| 101 | the functionality for all textual commands available
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| 102 | in our command line interface.</p>
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| 103 | <p>Every command is backed by a <b>lldb_private::CommandObject</b>
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| 104 | or <b>lldb_private::CommandObjectMultiword</b> object.</p>
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| 105 | <p><b>lldb_private::CommandObjectMultiword</b> are commands that
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| 106 | have subcommands and allow command line commands to be
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Benjamin Kramer | 46a8cf3 | 2010-06-10 08:12:17 +0000 | [diff] [blame] | 107 | logically grouped into a hiearchy.</p>
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 108 | <p><b>lldb_private::CommandObject</b> command line commands
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| 109 | are the objects that implement the functionality of the
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| 110 | command. They can optionally define
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| 111 | options for themselves, as well as group those options into
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| 112 | logical groups that can go together. The help system is
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| 113 | tied into these objects and can extract the syntax and
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| 114 | option groupings to display appropriate help for each
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| 115 | command.</p>
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| 116 | </div>
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| 117 | <div class="postfooter"></div>
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| 118 | </div>
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| 119 | <a name="core"></a>
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| 120 | <div class="post">
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| 121 | <h1 class ="postheader">Core</h1>
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| 122 | <div class="postcontent">
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| 123 |
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| 124 | <p>The Core source files contain basic functionality that
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| 125 | is required in the debugger. A wide variety of classes
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Benjamin Kramer | 46a8cf3 | 2010-06-10 08:12:17 +0000 | [diff] [blame] | 126 | are implemented:</p>
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 127 |
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| 128 | <ul>
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| 129 | <li>Address (section offset addressing)</li>
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| 130 | <li>AddressRange</li>
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| 131 | <li>Architecture specification</li>
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| 132 | <li>Broadcaster / Event / Listener </li>
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| 133 | <li>Communication classes that use Connection objects</li>
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| 134 | <li>Uniqued C strings</li>
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| 135 | <li>Data extraction</li>
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| 136 | <li>File specifications</li>
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| 137 | <li>Mangled names</li>
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| 138 | <li>Regular expressions</li>
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| 139 | <li>Source manager</li>
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| 140 | <li>Streams</li>
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| 141 | <li>Value objects</li>
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| 142 | </ul>
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| 143 | </div>
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| 144 | <div class="postfooter"></div>
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| 145 | </div>
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| 146 | <a name="expression"></a>
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| 147 | <div class="post">
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| 148 | <h1 class ="postheader">Expression</h1>
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| 149 | <div class="postcontent">
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| 150 |
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| 151 | <p>Expression parsing files cover everything from evaluating
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| 152 | DWARF expressions, to evaluating expressions using
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| 153 | Clang.</p>
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| 154 | <p>The DWARF expression parser has been heavily modified to
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| 155 | support type promotion, new opcodes needed for evaluating
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| 156 | expressions with symbolic variable references (expression local variables,
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| 157 | program variables), and other operators required by
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| 158 | typical expressions such as assign, address of, float/double/long
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| 159 | double floating point values, casting, and more. The
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| 160 | DWARF expression parser uses a stack of lldb_private::Value
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| 161 | objects. These objects know how to do the standard C type
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| 162 | promotion, and allow for symbolic references to variables
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| 163 | in the program and in the LLDB process (expression local
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| 164 | and expression global variables).</p>
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| 165 | <p>The expression parser uses a full instance of the Clang
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| 166 | compiler in order to accurately evaluate expressions.
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| 167 | Hooks have been put into Clang so that the compiler knows
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Chris Lattner | ba6d3bb | 2010-06-11 22:52:46 +0000 | [diff] [blame] | 168 | to ask about identifiers it doesn't know about. Once
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 169 | expressions have be compiled into an AST, we can then
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| 170 | traverse this AST and either generate a DWARF expression
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| 171 | that contains simple opcodes that can be quickly re-evaluated
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| 172 | each time an expression needs to be evaluated, or JIT'ed
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Benjamin Kramer | 46a8cf3 | 2010-06-10 08:12:17 +0000 | [diff] [blame] | 173 | up into code that can be run on the process being debugged.</p>
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 174 | </div>
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| 175 | <div class="postfooter"></div>
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| 176 | </div>
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| 177 | <a name="host"></a>
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| 178 | <div class="post">
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| 179 | <h1 class ="postheader">Host</h1>
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| 180 | <div class="postcontent">
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| 181 |
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| 182 | <p>LLDB tries to abstract itself from the host upon which
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| 183 | it is currently running by providing a host abstraction
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Chris Lattner | ba6d3bb | 2010-06-11 22:52:46 +0000 | [diff] [blame] | 184 | layer. This layer involves everything from spawning, detaching,
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| 185 | joining and killing native in-process threads, to getting
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 186 | current information about the current host.</p>
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Benjamin Kramer | 46a8cf3 | 2010-06-10 08:12:17 +0000 | [diff] [blame] | 187 | <p>Host functionality includes abstraction layers for:</p>
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 188 | <ul>
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| 189 | <li>Mutexes</li>
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| 190 | <li>Conditions</li>
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| 191 | <li>Timing functions</li>
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| 192 | <li>Thread functions</li>
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| 193 | <li>Host target triple</li>
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| 194 | <li>Host child process notifications</li>
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| 195 | <li>Host specific types</li>
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| 196 | </ul>
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| 197 | </div>
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| 198 | <div class="postfooter"></div>
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| 199 | </div>
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| 200 | <a name="interpreter"></a>
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| 201 | <div class="post">
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| 202 | <h1 class ="postheader">Interpreter</h1>
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| 203 | <div class="postcontent">
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| 204 |
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| 205 | <p>The interpreter classes are the classes responsible for
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| 206 | being the base classes needed for each command object,
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| 207 | and is responsible for tracking and running command line
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Benjamin Kramer | 46a8cf3 | 2010-06-10 08:12:17 +0000 | [diff] [blame] | 208 | commands.</p>
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 209 | </div>
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| 210 | <div class="postfooter"></div>
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| 211 | </div>
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| 212 | <a name="symbol"></a>
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| 213 | <div class="post">
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| 214 | <h1 class ="postheader">Symbol</h1>
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| 215 | <div class="postcontent">
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| 216 | <p>Symbol classes involve everything needed in order to parse
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| 217 | object files and debug symbols. All the needed classes
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| 218 | for compilation units (code and debug info for a source file),
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| 219 | functions, lexical blocks within functions, inlined
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| 220 | functions, types, declaration locations, and variables
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| 221 | are in this section.</p>
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| 222 | </div>
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| 223 | <div class="postfooter"></div>
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| 224 | </div>
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| 225 | <a name="targ"></a>
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| 226 | <div class="post">
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| 227 | <h1 class ="postheader">Target</h1>
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| 228 | <div class="postcontent">
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| 229 |
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| 230 | <p>Classes that are related to a debug target include:</p>
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| 231 | <ul>
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| 232 | <li>Target</li>
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| 233 | <li>Process</li>
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| 234 | <li>Thread</li>
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| 235 | <li>Stack frames</li>
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| 236 | <li>Stack frame registers</li>
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| 237 | <li>ABI for function calling in process being debugged</li>
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| 238 | <li>Execution context batons</li>
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| 239 | </ul>
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| 240 | </div>
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| 241 | <div class="postfooter"></div>
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| 242 | </div>
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| 243 | <a name="utility"></a>
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| 244 | <div class="post">
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| 245 | <h1 class ="postheader">Utility</h1>
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| 246 | <div class="postcontent">
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| 247 |
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Christopher Friesen | 236d842 | 2010-06-12 03:34:21 +0000 | [diff] [blame] | 248 | <p>Utility files should be as stand alone as possible and
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| 249 | available for LLDB, plug-ins or related
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Eric Christopher | b7eb709 | 2010-06-10 05:35:26 +0000 | [diff] [blame] | 250 | applications to use.</p>
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Greg Clayton | 854bb53 | 2010-06-10 02:48:57 +0000 | [diff] [blame] | 251 | <p>Files found in the Utility section include:</p>
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| 252 | <ul>
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| 253 | <li>Pseudo-terminal support</li>
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| 254 | <li>Register numbering for specific architectures.</li>
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| 255 | <li>String data extractors</li>
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| 256 | </ul>
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| 257 | </div>
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| 258 | <div class="postfooter"></div>
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| 259 | </div>
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| 260 | </div>
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| 261 | </div>
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| 262 | </div>
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| 263 | </body>
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Eric Christopher | b7eb709 | 2010-06-10 05:35:26 +0000 | [diff] [blame] | 264 | </html>
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