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- <title>CommandLine 2.0 Library Manual</title>
- <link rel="stylesheet" href="_static/llvm.css" type="text/css">
-</head>
-<body>
-
-<h1>
- CommandLine 2.0 Library Manual
-</h1>
-
-<ol>
- <li><a href="#introduction">Introduction</a></li>
-
- <li><a href="#quickstart">Quick Start Guide</a>
- <ol>
- <li><a href="#bool">Boolean Arguments</a></li>
- <li><a href="#alias">Argument Aliases</a></li>
- <li><a href="#onealternative">Selecting an alternative from a
- set of possibilities</a></li>
- <li><a href="#namedalternatives">Named alternatives</a></li>
- <li><a href="#list">Parsing a list of options</a></li>
- <li><a href="#bits">Collecting options as a set of flags</a></li>
- <li><a href="#description">Adding freeform text to help output</a></li>
- </ol></li>
-
- <li><a href="#referenceguide">Reference Guide</a>
- <ol>
- <li><a href="#positional">Positional Arguments</a>
- <ul>
- <li><a href="#--">Specifying positional options with hyphens</a></li>
- <li><a href="#getPosition">Determining absolute position with
- getPosition</a></li>
- <li><a href="#cl::ConsumeAfter">The <tt>cl::ConsumeAfter</tt>
- modifier</a></li>
- </ul></li>
-
- <li><a href="#storage">Internal vs External Storage</a></li>
-
- <li><a href="#attributes">Option Attributes</a></li>
-
- <li><a href="#modifiers">Option Modifiers</a>
- <ul>
- <li><a href="#hiding">Hiding an option from <tt>-help</tt>
- output</a></li>
- <li><a href="#numoccurrences">Controlling the number of occurrences
- required and allowed</a></li>
- <li><a href="#valrequired">Controlling whether or not a value must be
- specified</a></li>
- <li><a href="#formatting">Controlling other formatting options</a></li>
- <li><a href="#misc">Miscellaneous option modifiers</a></li>
- <li><a href="#response">Response files</a></li>
- </ul></li>
-
- <li><a href="#toplevel">Top-Level Classes and Functions</a>
- <ul>
- <li><a href="#cl::ParseCommandLineOptions">The
- <tt>cl::ParseCommandLineOptions</tt> function</a></li>
- <li><a href="#cl::ParseEnvironmentOptions">The
- <tt>cl::ParseEnvironmentOptions</tt> function</a></li>
- <li><a href="#cl::SetVersionPrinter">The <tt>cl::SetVersionPrinter</tt>
- function</a></li>
- <li><a href="#cl::opt">The <tt>cl::opt</tt> class</a></li>
- <li><a href="#cl::list">The <tt>cl::list</tt> class</a></li>
- <li><a href="#cl::bits">The <tt>cl::bits</tt> class</a></li>
- <li><a href="#cl::alias">The <tt>cl::alias</tt> class</a></li>
- <li><a href="#cl::extrahelp">The <tt>cl::extrahelp</tt> class</a></li>
- </ul></li>
-
- <li><a href="#builtinparsers">Builtin parsers</a>
- <ul>
- <li><a href="#genericparser">The Generic <tt>parser<t></tt>
- parser</a></li>
- <li><a href="#boolparser">The <tt>parser<bool></tt>
- specialization</a></li>
- <li><a href="#boolOrDefaultparser">The <tt>parser<boolOrDefault></tt>
- specialization</a></li>
- <li><a href="#stringparser">The <tt>parser<string></tt>
- specialization</a></li>
- <li><a href="#intparser">The <tt>parser<int></tt>
- specialization</a></li>
- <li><a href="#doubleparser">The <tt>parser<double></tt> and
- <tt>parser<float></tt> specializations</a></li>
- </ul></li>
- </ol></li>
- <li><a href="#extensionguide">Extension Guide</a>
- <ol>
- <li><a href="#customparser">Writing a custom parser</a></li>
- <li><a href="#explotingexternal">Exploiting external storage</a></li>
- <li><a href="#dynamicopts">Dynamically adding command line
- options</a></li>
- </ol></li>
-</ol>
-
-<div class="doc_author">
- <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></p>
-</div>
-
-<!-- *********************************************************************** -->
-<h2>
- <a name="introduction">Introduction</a>
-</h2>
-<!-- *********************************************************************** -->
-
-<div>
-
-<p>This document describes the CommandLine argument processing library. It will
-show you how to use it, and what it can do. The CommandLine library uses a
-declarative approach to specifying the command line options that your program
-takes. By default, these options declarations implicitly hold the value parsed
-for the option declared (of course this <a href="#storage">can be
-changed</a>).</p>
-
-<p>Although there are a <b>lot</b> of command line argument parsing libraries
-out there in many different languages, none of them fit well with what I needed.
-By looking at the features and problems of other libraries, I designed the
-CommandLine library to have the following features:</p>
-
-<ol>
-<li>Speed: The CommandLine library is very quick and uses little resources. The
-parsing time of the library is directly proportional to the number of arguments
-parsed, not the number of options recognized. Additionally, command line
-argument values are captured transparently into user defined global variables,
-which can be accessed like any other variable (and with the same
-performance).</li>
-
-<li>Type Safe: As a user of CommandLine, you don't have to worry about
-remembering the type of arguments that you want (is it an int? a string? a
-bool? an enum?) and keep casting it around. Not only does this help prevent
-error prone constructs, it also leads to dramatically cleaner source code.</li>
-
-<li>No subclasses required: To use CommandLine, you instantiate variables that
-correspond to the arguments that you would like to capture, you don't subclass a
-parser. This means that you don't have to write <b>any</b> boilerplate
-code.</li>
-
-<li>Globally accessible: Libraries can specify command line arguments that are
-automatically enabled in any tool that links to the library. This is possible
-because the application doesn't have to keep a list of arguments to pass to
-the parser. This also makes supporting <a href="#dynamicopts">dynamically
-loaded options</a> trivial.</li>
-
-<li>Cleaner: CommandLine supports enum and other types directly, meaning that
-there is less error and more security built into the library. You don't have to
-worry about whether your integral command line argument accidentally got
-assigned a value that is not valid for your enum type.</li>
-
-<li>Powerful: The CommandLine library supports many different types of
-arguments, from simple <a href="#boolparser">boolean flags</a> to <a
-href="#cl::opt">scalars arguments</a> (<a href="#stringparser">strings</a>, <a
-href="#intparser">integers</a>, <a href="#genericparser">enums</a>, <a
-href="#doubleparser">doubles</a>), to <a href="#cl::list">lists of
-arguments</a>. This is possible because CommandLine is...</li>
-
-<li>Extensible: It is very simple to add a new argument type to CommandLine.
-Simply specify the parser that you want to use with the command line option when
-you declare it. <a href="#customparser">Custom parsers</a> are no problem.</li>
-
-<li>Labor Saving: The CommandLine library cuts down on the amount of grunt work
-that you, the user, have to do. For example, it automatically provides a
-<tt>-help</tt> option that shows the available command line options for your
-tool. Additionally, it does most of the basic correctness checking for
-you.</li>
-
-<li>Capable: The CommandLine library can handle lots of different forms of
-options often found in real programs. For example, <a
-href="#positional">positional</a> arguments, <tt>ls</tt> style <a
-href="#cl::Grouping">grouping</a> options (to allow processing '<tt>ls
--lad</tt>' naturally), <tt>ld</tt> style <a href="#cl::Prefix">prefix</a>
-options (to parse '<tt>-lmalloc -L/usr/lib</tt>'), and <a
-href="#cl::ConsumeAfter">interpreter style options</a>.</li>
-
-</ol>
-
-<p>This document will hopefully let you jump in and start using CommandLine in
-your utility quickly and painlessly. Additionally it should be a simple
-reference manual to figure out how stuff works. If it is failing in some area
-(or you want an extension to the library), nag the author, <a
-href="mailto:sabre@nondot.org">Chris Lattner</a>.</p>
-
-</div>
-
-<!-- *********************************************************************** -->
-<h2>
- <a name="quickstart">Quick Start Guide</a>
-</h2>
-<!-- *********************************************************************** -->
-
-<div>
-
-<p>This section of the manual runs through a simple CommandLine'ification of a
-basic compiler tool. This is intended to show you how to jump into using the
-CommandLine library in your own program, and show you some of the cool things it
-can do.</p>
-
-<p>To start out, you need to include the CommandLine header file into your
-program:</p>
-
-<div class="doc_code"><pre>
- #include "llvm/Support/CommandLine.h"
-</pre></div>
-
-<p>Additionally, you need to add this as the first line of your main
-program:</p>
-
-<div class="doc_code"><pre>
-int main(int argc, char **argv) {
- <a href="#cl::ParseCommandLineOptions">cl::ParseCommandLineOptions</a>(argc, argv);
- ...
-}
-</pre></div>
-
-<p>... which actually parses the arguments and fills in the variable
-declarations.</p>
-
-<p>Now that you are ready to support command line arguments, we need to tell the
-system which ones we want, and what type of arguments they are. The CommandLine
-library uses a declarative syntax to model command line arguments with the
-global variable declarations that capture the parsed values. This means that
-for every command line option that you would like to support, there should be a
-global variable declaration to capture the result. For example, in a compiler,
-we would like to support the Unix-standard '<tt>-o <filename></tt>' option
-to specify where to put the output. With the CommandLine library, this is
-represented like this:</p>
-
-<a name="value_desc_example"></a>
-<div class="doc_code"><pre>
-<a href="#cl::opt">cl::opt</a><string> OutputFilename("<i>o</i>", <a href="#cl::desc">cl::desc</a>("<i>Specify output filename</i>"), <a href="#cl::value_desc">cl::value_desc</a>("<i>filename</i>"));
-</pre></div>
-
-<p>This declares a global variable "<tt>OutputFilename</tt>" that is used to
-capture the result of the "<tt>o</tt>" argument (first parameter). We specify
-that this is a simple scalar option by using the "<tt><a
-href="#cl::opt">cl::opt</a></tt>" template (as opposed to the <a
-href="#list">"<tt>cl::list</tt> template</a>), and tell the CommandLine library
-that the data type that we are parsing is a string.</p>
-
-<p>The second and third parameters (which are optional) are used to specify what
-to output for the "<tt>-help</tt>" option. In this case, we get a line that
-looks like this:</p>
-
-<div class="doc_code"><pre>
-USAGE: compiler [options]
-
-OPTIONS:
- -help - display available options (-help-hidden for more)
- <b>-o <filename> - Specify output filename</b>
-</pre></div>
-
-<p>Because we specified that the command line option should parse using the
-<tt>string</tt> data type, the variable declared is automatically usable as a
-real string in all contexts that a normal C++ string object may be used. For
-example:</p>
-
-<div class="doc_code"><pre>
- ...
- std::ofstream Output(OutputFilename.c_str());
- if (Output.good()) ...
- ...
-</pre></div>
-
-<p>There are many different options that you can use to customize the command
-line option handling library, but the above example shows the general interface
-to these options. The options can be specified in any order, and are specified
-with helper functions like <a href="#cl::desc"><tt>cl::desc(...)</tt></a>, so
-there are no positional dependencies to remember. The available options are
-discussed in detail in the <a href="#referenceguide">Reference Guide</a>.</p>
-
-<p>Continuing the example, we would like to have our compiler take an input
-filename as well as an output filename, but we do not want the input filename to
-be specified with a hyphen (ie, not <tt>-filename.c</tt>). To support this
-style of argument, the CommandLine library allows for <a
-href="#positional">positional</a> arguments to be specified for the program.
-These positional arguments are filled with command line parameters that are not
-in option form. We use this feature like this:</p>
-
-<div class="doc_code"><pre>
-<a href="#cl::opt">cl::opt</a><string> InputFilename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"), <a href="#cl::init">cl::init</a>("<i>-</i>"));
-</pre></div>
-
-<p>This declaration indicates that the first positional argument should be
-treated as the input filename. Here we use the <tt><a
-href="#cl::init">cl::init</a></tt> option to specify an initial value for the
-command line option, which is used if the option is not specified (if you do not
-specify a <tt><a href="#cl::init">cl::init</a></tt> modifier for an option, then
-the default constructor for the data type is used to initialize the value).
-Command line options default to being optional, so if we would like to require
-that the user always specify an input filename, we would add the <tt><a
-href="#cl::Required">cl::Required</a></tt> flag, and we could eliminate the
-<tt><a href="#cl::init">cl::init</a></tt> modifier, like this:</p>
-
-<div class="doc_code"><pre>
-<a href="#cl::opt">cl::opt</a><string> InputFilename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"), <b><a href="#cl::Required">cl::Required</a></b>);
-</pre></div>
-
-<p>Again, the CommandLine library does not require the options to be specified
-in any particular order, so the above declaration is equivalent to:</p>
-
-<div class="doc_code"><pre>
-<a href="#cl::opt">cl::opt</a><string> InputFilename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::Required">cl::Required</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"));
-</pre></div>
-
-<p>By simply adding the <tt><a href="#cl::Required">cl::Required</a></tt> flag,
-the CommandLine library will automatically issue an error if the argument is not
-specified, which shifts all of the command line option verification code out of
-your application into the library. This is just one example of how using flags
-can alter the default behaviour of the library, on a per-option basis. By
-adding one of the declarations above, the <tt>-help</tt> option synopsis is now
-extended to:</p>
-
-<div class="doc_code"><pre>
-USAGE: compiler [options] <b><input file></b>
-
-OPTIONS:
- -help - display available options (-help-hidden for more)
- -o <filename> - Specify output filename
-</pre></div>
-
-<p>... indicating that an input filename is expected.</p>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="bool">Boolean Arguments</a>
-</h3>
-
-<div>
-
-<p>In addition to input and output filenames, we would like the compiler example
-to support three boolean flags: "<tt>-f</tt>" to force writing binary output to
-a terminal, "<tt>--quiet</tt>" to enable quiet mode, and "<tt>-q</tt>" for
-backwards compatibility with some of our users. We can support these by
-declaring options of boolean type like this:</p>
-
-<div class="doc_code"><pre>
-<a href="#cl::opt">cl::opt</a><bool> Force ("<i>f</i>", <a href="#cl::desc">cl::desc</a>("<i>Enable binary output on terminals</i>"));
-<a href="#cl::opt">cl::opt</a><bool> Quiet ("<i>quiet</i>", <a href="#cl::desc">cl::desc</a>("<i>Don't print informational messages</i>"));
-<a href="#cl::opt">cl::opt</a><bool> Quiet2("<i>q</i>", <a href="#cl::desc">cl::desc</a>("<i>Don't print informational messages</i>"), <a href="#cl::Hidden">cl::Hidden</a>);
-</pre></div>
-
-<p>This does what you would expect: it declares three boolean variables
-("<tt>Force</tt>", "<tt>Quiet</tt>", and "<tt>Quiet2</tt>") to recognize these
-options. Note that the "<tt>-q</tt>" option is specified with the "<a
-href="#cl::Hidden"><tt>cl::Hidden</tt></a>" flag. This modifier prevents it
-from being shown by the standard "<tt>-help</tt>" output (note that it is still
-shown in the "<tt>-help-hidden</tt>" output).</p>
-
-<p>The CommandLine library uses a <a href="#builtinparsers">different parser</a>
-for different data types. For example, in the string case, the argument passed
-to the option is copied literally into the content of the string variable... we
-obviously cannot do that in the boolean case, however, so we must use a smarter
-parser. In the case of the boolean parser, it allows no options (in which case
-it assigns the value of true to the variable), or it allows the values
-"<tt>true</tt>" or "<tt>false</tt>" to be specified, allowing any of the
-following inputs:</p>
-
-<div class="doc_code"><pre>
- compiler -f # No value, 'Force' == true
- compiler -f=true # Value specified, 'Force' == true
- compiler -f=TRUE # Value specified, 'Force' == true
- compiler -f=FALSE # Value specified, 'Force' == false
-</pre></div>
-
-<p>... you get the idea. The <a href="#boolparser">bool parser</a> just turns
-the string values into boolean values, and rejects things like '<tt>compiler
--f=foo</tt>'. Similarly, the <a href="#doubleparser">float</a>, <a
-href="#doubleparser">double</a>, and <a href="#intparser">int</a> parsers work
-like you would expect, using the '<tt>strtol</tt>' and '<tt>strtod</tt>' C
-library calls to parse the string value into the specified data type.</p>
-
-<p>With the declarations above, "<tt>compiler -help</tt>" emits this:</p>
-
-<div class="doc_code"><pre>
-USAGE: compiler [options] <input file>
-
-OPTIONS:
- <b>-f - Enable binary output on terminals</b>
- -o - Override output filename
- <b>-quiet - Don't print informational messages</b>
- -help - display available options (-help-hidden for more)
-</pre></div>
-
-<p>and "<tt>compiler -help-hidden</tt>" prints this:</p>
-
-<div class="doc_code"><pre>
-USAGE: compiler [options] <input file>
-
-OPTIONS:
- -f - Enable binary output on terminals
- -o - Override output filename
- <b>-q - Don't print informational messages</b>
- -quiet - Don't print informational messages
- -help - display available options (-help-hidden for more)
-</pre></div>
-
-<p>This brief example has shown you how to use the '<tt><a
-href="#cl::opt">cl::opt</a></tt>' class to parse simple scalar command line
-arguments. In addition to simple scalar arguments, the CommandLine library also
-provides primitives to support CommandLine option <a href="#alias">aliases</a>,
-and <a href="#list">lists</a> of options.</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="alias">Argument Aliases</a>
-</h3>
-
-<div>
-
-<p>So far, the example works well, except for the fact that we need to check the
-quiet condition like this now:</p>
-
-<div class="doc_code"><pre>
-...
- if (!Quiet && !Quiet2) printInformationalMessage(...);
-...
-</pre></div>
-
-<p>... which is a real pain! Instead of defining two values for the same
-condition, we can use the "<tt><a href="#cl::alias">cl::alias</a></tt>" class to make the "<tt>-q</tt>"
-option an <b>alias</b> for the "<tt>-quiet</tt>" option, instead of providing
-a value itself:</p>
-
-<div class="doc_code"><pre>
-<a href="#cl::opt">cl::opt</a><bool> Force ("<i>f</i>", <a href="#cl::desc">cl::desc</a>("<i>Overwrite output files</i>"));
-<a href="#cl::opt">cl::opt</a><bool> Quiet ("<i>quiet</i>", <a href="#cl::desc">cl::desc</a>("<i>Don't print informational messages</i>"));
-<a href="#cl::alias">cl::alias</a> QuietA("<i>q</i>", <a href="#cl::desc">cl::desc</a>("<i>Alias for -quiet</i>"), <a href="#cl::aliasopt">cl::aliasopt</a>(Quiet));
-</pre></div>
-
-<p>The third line (which is the only one we modified from above) defines a
-"<tt>-q</tt>" alias that updates the "<tt>Quiet</tt>" variable (as specified by
-the <tt><a href="#cl::aliasopt">cl::aliasopt</a></tt> modifier) whenever it is
-specified. Because aliases do not hold state, the only thing the program has to
-query is the <tt>Quiet</tt> variable now. Another nice feature of aliases is
-that they automatically hide themselves from the <tt>-help</tt> output
-(although, again, they are still visible in the <tt>-help-hidden
-output</tt>).</p>
-
-<p>Now the application code can simply use:</p>
-
-<div class="doc_code"><pre>
-...
- if (!Quiet) printInformationalMessage(...);
-...
-</pre></div>
-
-<p>... which is much nicer! The "<tt><a href="#cl::alias">cl::alias</a></tt>"
-can be used to specify an alternative name for any variable type, and has many
-uses.</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="onealternative">Selecting an alternative from a set of
- possibilities</a>
-</h3>
-
-<div>
-
-<p>So far we have seen how the CommandLine library handles builtin types like
-<tt>std::string</tt>, <tt>bool</tt> and <tt>int</tt>, but how does it handle
-things it doesn't know about, like enums or '<tt>int*</tt>'s?</p>
-
-<p>The answer is that it uses a table-driven generic parser (unless you specify
-your own parser, as described in the <a href="#extensionguide">Extension
-Guide</a>). This parser maps literal strings to whatever type is required, and
-requires you to tell it what this mapping should be.</p>
-
-<p>Let's say that we would like to add four optimization levels to our
-optimizer, using the standard flags "<tt>-g</tt>", "<tt>-O0</tt>",
-"<tt>-O1</tt>", and "<tt>-O2</tt>". We could easily implement this with boolean
-options like above, but there are several problems with this strategy:</p>
-
-<ol>
-<li>A user could specify more than one of the options at a time, for example,
-"<tt>compiler -O3 -O2</tt>". The CommandLine library would not be able to
-catch this erroneous input for us.</li>
-
-<li>We would have to test 4 different variables to see which ones are set.</li>
-
-<li>This doesn't map to the numeric levels that we want... so we cannot easily
-see if some level >= "<tt>-O1</tt>" is enabled.</li>
-
-</ol>
-
-<p>To cope with these problems, we can use an enum value, and have the
-CommandLine library fill it in with the appropriate level directly, which is
-used like this:</p>
-
-<div class="doc_code"><pre>
-enum OptLevel {
- g, O1, O2, O3
-};
-
-<a href="#cl::opt">cl::opt</a><OptLevel> OptimizationLevel(<a href="#cl::desc">cl::desc</a>("<i>Choose optimization level:</i>"),
- <a href="#cl::values">cl::values</a>(
- clEnumVal(g , "<i>No optimizations, enable debugging</i>"),
- clEnumVal(O1, "<i>Enable trivial optimizations</i>"),
- clEnumVal(O2, "<i>Enable default optimizations</i>"),
- clEnumVal(O3, "<i>Enable expensive optimizations</i>"),
- clEnumValEnd));
-
-...
- if (OptimizationLevel >= O2) doPartialRedundancyElimination(...);
-...
-</pre></div>
-
-<p>This declaration defines a variable "<tt>OptimizationLevel</tt>" of the
-"<tt>OptLevel</tt>" enum type. This variable can be assigned any of the values
-that are listed in the declaration (Note that the declaration list must be
-terminated with the "<tt>clEnumValEnd</tt>" argument!). The CommandLine
-library enforces
-that the user can only specify one of the options, and it ensure that only valid
-enum values can be specified. The "<tt>clEnumVal</tt>" macros ensure that the
-command line arguments matched the enum values. With this option added, our
-help output now is:</p>
-
-<div class="doc_code"><pre>
-USAGE: compiler [options] <input file>
-
-OPTIONS:
- <b>Choose optimization level:
- -g - No optimizations, enable debugging
- -O1 - Enable trivial optimizations
- -O2 - Enable default optimizations
- -O3 - Enable expensive optimizations</b>
- -f - Enable binary output on terminals
- -help - display available options (-help-hidden for more)
- -o <filename> - Specify output filename
- -quiet - Don't print informational messages
-</pre></div>
-
-<p>In this case, it is sort of awkward that flag names correspond directly to
-enum names, because we probably don't want a enum definition named "<tt>g</tt>"
-in our program. Because of this, we can alternatively write this example like
-this:</p>
-
-<div class="doc_code"><pre>
-enum OptLevel {
- Debug, O1, O2, O3
-};
-
-<a href="#cl::opt">cl::opt</a><OptLevel> OptimizationLevel(<a href="#cl::desc">cl::desc</a>("<i>Choose optimization level:</i>"),
- <a href="#cl::values">cl::values</a>(
- clEnumValN(Debug, "g", "<i>No optimizations, enable debugging</i>"),
- clEnumVal(O1 , "<i>Enable trivial optimizations</i>"),
- clEnumVal(O2 , "<i>Enable default optimizations</i>"),
- clEnumVal(O3 , "<i>Enable expensive optimizations</i>"),
- clEnumValEnd));
-
-...
- if (OptimizationLevel == Debug) outputDebugInfo(...);
-...
-</pre></div>
-
-<p>By using the "<tt>clEnumValN</tt>" macro instead of "<tt>clEnumVal</tt>", we
-can directly specify the name that the flag should get. In general a direct
-mapping is nice, but sometimes you can't or don't want to preserve the mapping,
-which is when you would use it.</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="namedalternatives">Named Alternatives</a>
-</h3>
-
-<div>
-
-<p>Another useful argument form is a named alternative style. We shall use this
-style in our compiler to specify different debug levels that can be used.
-Instead of each debug level being its own switch, we want to support the
-following options, of which only one can be specified at a time:
-"<tt>--debug-level=none</tt>", "<tt>--debug-level=quick</tt>",
-"<tt>--debug-level=detailed</tt>". To do this, we use the exact same format as
-our optimization level flags, but we also specify an option name. For this
-case, the code looks like this:</p>
-
-<div class="doc_code"><pre>
-enum DebugLev {
- nodebuginfo, quick, detailed
-};
-
-// Enable Debug Options to be specified on the command line
-<a href="#cl::opt">cl::opt</a><DebugLev> DebugLevel("<i>debug_level</i>", <a href="#cl::desc">cl::desc</a>("<i>Set the debugging level:</i>"),
- <a href="#cl::values">cl::values</a>(
- clEnumValN(nodebuginfo, "none", "<i>disable debug information</i>"),
- clEnumVal(quick, "<i>enable quick debug information</i>"),
- clEnumVal(detailed, "<i>enable detailed debug information</i>"),
- clEnumValEnd));
-</pre></div>
-
-<p>This definition defines an enumerated command line variable of type "<tt>enum
-DebugLev</tt>", which works exactly the same way as before. The difference here
-is just the interface exposed to the user of your program and the help output by
-the "<tt>-help</tt>" option:</p>
-
-<div class="doc_code"><pre>
-USAGE: compiler [options] <input file>
-
-OPTIONS:
- Choose optimization level:
- -g - No optimizations, enable debugging
- -O1 - Enable trivial optimizations
- -O2 - Enable default optimizations
- -O3 - Enable expensive optimizations
- <b>-debug_level - Set the debugging level:
- =none - disable debug information
- =quick - enable quick debug information
- =detailed - enable detailed debug information</b>
- -f - Enable binary output on terminals
- -help - display available options (-help-hidden for more)
- -o <filename> - Specify output filename
- -quiet - Don't print informational messages
-</pre></div>
-
-<p>Again, the only structural difference between the debug level declaration and
-the optimization level declaration is that the debug level declaration includes
-an option name (<tt>"debug_level"</tt>), which automatically changes how the
-library processes the argument. The CommandLine library supports both forms so
-that you can choose the form most appropriate for your application.</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="list">Parsing a list of options</a>
-</h3>
-
-<div>
-
-<p>Now that we have the standard run-of-the-mill argument types out of the way,
-lets get a little wild and crazy. Lets say that we want our optimizer to accept
-a <b>list</b> of optimizations to perform, allowing duplicates. For example, we
-might want to run: "<tt>compiler -dce -constprop -inline -dce -strip</tt>". In
-this case, the order of the arguments and the number of appearances is very
-important. This is what the "<tt><a href="#cl::list">cl::list</a></tt>"
-template is for. First, start by defining an enum of the optimizations that you
-would like to perform:</p>
-
-<div class="doc_code"><pre>
-enum Opts {
- // 'inline' is a C++ keyword, so name it 'inlining'
- dce, constprop, inlining, strip
-};
-</pre></div>
-
-<p>Then define your "<tt><a href="#cl::list">cl::list</a></tt>" variable:</p>
-
-<div class="doc_code"><pre>
-<a href="#cl::list">cl::list</a><Opts> OptimizationList(<a href="#cl::desc">cl::desc</a>("<i>Available Optimizations:</i>"),
- <a href="#cl::values">cl::values</a>(
- clEnumVal(dce , "<i>Dead Code Elimination</i>"),
- clEnumVal(constprop , "<i>Constant Propagation</i>"),
- clEnumValN(inlining, "<i>inline</i>", "<i>Procedure Integration</i>"),
- clEnumVal(strip , "<i>Strip Symbols</i>"),
- clEnumValEnd));
-</pre></div>
-
-<p>This defines a variable that is conceptually of the type
-"<tt>std::vector<enum Opts></tt>". Thus, you can access it with standard
-vector methods:</p>
-
-<div class="doc_code"><pre>
- for (unsigned i = 0; i != OptimizationList.size(); ++i)
- switch (OptimizationList[i])
- ...
-</pre></div>
-
-<p>... to iterate through the list of options specified.</p>
-
-<p>Note that the "<tt><a href="#cl::list">cl::list</a></tt>" template is
-completely general and may be used with any data types or other arguments that
-you can use with the "<tt><a href="#cl::opt">cl::opt</a></tt>" template. One
-especially useful way to use a list is to capture all of the positional
-arguments together if there may be more than one specified. In the case of a
-linker, for example, the linker takes several '<tt>.o</tt>' files, and needs to
-capture them into a list. This is naturally specified as:</p>
-
-<div class="doc_code"><pre>
-...
-<a href="#cl::list">cl::list</a><std::string> InputFilenames(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<Input files>"), <a href="#cl::OneOrMore">cl::OneOrMore</a>);
-...
-</pre></div>
-
-<p>This variable works just like a "<tt>vector<string></tt>" object. As
-such, accessing the list is simple, just like above. In this example, we used
-the <tt><a href="#cl::OneOrMore">cl::OneOrMore</a></tt> modifier to inform the
-CommandLine library that it is an error if the user does not specify any
-<tt>.o</tt> files on our command line. Again, this just reduces the amount of
-checking we have to do.</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="bits">Collecting options as a set of flags</a>
-</h3>
-
-<div>
-
-<p>Instead of collecting sets of options in a list, it is also possible to
-gather information for enum values in a <b>bit vector</b>. The representation used by
-the <a href="#bits"><tt>cl::bits</tt></a> class is an <tt>unsigned</tt>
-integer. An enum value is represented by a 0/1 in the enum's ordinal value bit
-position. 1 indicating that the enum was specified, 0 otherwise. As each
-specified value is parsed, the resulting enum's bit is set in the option's bit
-vector:</p>
-
-<div class="doc_code"><pre>
- <i>bits</i> |= 1 << (unsigned)<i>enum</i>;
-</pre></div>
-
-<p>Options that are specified multiple times are redundant. Any instances after
-the first are discarded.</p>
-
-<p>Reworking the above list example, we could replace <a href="#list">
-<tt>cl::list</tt></a> with <a href="#bits"><tt>cl::bits</tt></a>:</p>
-
-<div class="doc_code"><pre>
-<a href="#cl::bits">cl::bits</a><Opts> OptimizationBits(<a href="#cl::desc">cl::desc</a>("<i>Available Optimizations:</i>"),
- <a href="#cl::values">cl::values</a>(
- clEnumVal(dce , "<i>Dead Code Elimination</i>"),
- clEnumVal(constprop , "<i>Constant Propagation</i>"),
- clEnumValN(inlining, "<i>inline</i>", "<i>Procedure Integration</i>"),
- clEnumVal(strip , "<i>Strip Symbols</i>"),
- clEnumValEnd));
-</pre></div>
-
-<p>To test to see if <tt>constprop</tt> was specified, we can use the
-<tt>cl:bits::isSet</tt> function:</p>
-
-<div class="doc_code"><pre>
- if (OptimizationBits.isSet(constprop)) {
- ...
- }
-</pre></div>
-
-<p>It's also possible to get the raw bit vector using the
-<tt>cl::bits::getBits</tt> function:</p>
-
-<div class="doc_code"><pre>
- unsigned bits = OptimizationBits.getBits();
-</pre></div>
-
-<p>Finally, if external storage is used, then the location specified must be of
-<b>type</b> <tt>unsigned</tt>. In all other ways a <a
-href="#bits"><tt>cl::bits</tt></a> option is equivalent to a <a
-href="#list"> <tt>cl::list</tt></a> option.</p>
-
-</div>
-
-
-<!-- ======================================================================= -->
-<h3>
- <a name="description">Adding freeform text to help output</a>
-</h3>
-
-<div>
-
-<p>As our program grows and becomes more mature, we may decide to put summary
-information about what it does into the help output. The help output is styled
-to look similar to a Unix <tt>man</tt> page, providing concise information about
-a program. Unix <tt>man</tt> pages, however often have a description about what
-the program does. To add this to your CommandLine program, simply pass a third
-argument to the <a
-href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>
-call in main. This additional argument is then printed as the overview
-information for your program, allowing you to include any additional information
-that you want. For example:</p>
-
-<div class="doc_code"><pre>
-int main(int argc, char **argv) {
- <a href="#cl::ParseCommandLineOptions">cl::ParseCommandLineOptions</a>(argc, argv, " CommandLine compiler example\n\n"
- " This program blah blah blah...\n");
- ...
-}
-</pre></div>
-
-<p>would yield the help output:</p>
-
-<div class="doc_code"><pre>
-<b>OVERVIEW: CommandLine compiler example
-
- This program blah blah blah...</b>
-
-USAGE: compiler [options] <input file>
-
-OPTIONS:
- ...
- -help - display available options (-help-hidden for more)
- -o <filename> - Specify output filename
-</pre></div>
-
-</div>
-
-</div>
-
-<!-- *********************************************************************** -->
-<h2>
- <a name="referenceguide">Reference Guide</a>
-</h2>
-<!-- *********************************************************************** -->
-
-<div>
-
-<p>Now that you know the basics of how to use the CommandLine library, this
-section will give you the detailed information you need to tune how command line
-options work, as well as information on more "advanced" command line option
-processing capabilities.</p>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="positional">Positional Arguments</a>
-</h3>
-
-<div>
-
-<p>Positional arguments are those arguments that are not named, and are not
-specified with a hyphen. Positional arguments should be used when an option is
-specified by its position alone. For example, the standard Unix <tt>grep</tt>
-tool takes a regular expression argument, and an optional filename to search
-through (which defaults to standard input if a filename is not specified).
-Using the CommandLine library, this would be specified as:</p>
-
-<div class="doc_code"><pre>
-<a href="#cl::opt">cl::opt</a><string> Regex (<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><regular expression></i>"), <a href="#cl::Required">cl::Required</a>);
-<a href="#cl::opt">cl::opt</a><string> Filename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"), <a href="#cl::init">cl::init</a>("<i>-</i>"));
-</pre></div>
-
-<p>Given these two option declarations, the <tt>-help</tt> output for our grep
-replacement would look like this:</p>
-
-<div class="doc_code"><pre>
-USAGE: spiffygrep [options] <b><regular expression> <input file></b>
-
-OPTIONS:
- -help - display available options (-help-hidden for more)
-</pre></div>
-
-<p>... and the resultant program could be used just like the standard
-<tt>grep</tt> tool.</p>
-
-<p>Positional arguments are sorted by their order of construction. This means
-that command line options will be ordered according to how they are listed in a
-.cpp file, but will not have an ordering defined if the positional arguments
-are defined in multiple .cpp files. The fix for this problem is simply to
-define all of your positional arguments in one .cpp file.</p>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="--">Specifying positional options with hyphens</a>
-</h4>
-
-<div>
-
-<p>Sometimes you may want to specify a value to your positional argument that
-starts with a hyphen (for example, searching for '<tt>-foo</tt>' in a file). At
-first, you will have trouble doing this, because it will try to find an argument
-named '<tt>-foo</tt>', and will fail (and single quotes will not save you).
-Note that the system <tt>grep</tt> has the same problem:</p>
-
-<div class="doc_code"><pre>
- $ spiffygrep '-foo' test.txt
- Unknown command line argument '-foo'. Try: spiffygrep -help'
-
- $ grep '-foo' test.txt
- grep: illegal option -- f
- grep: illegal option -- o
- grep: illegal option -- o
- Usage: grep -hblcnsviw pattern file . . .
-</pre></div>
-
-<p>The solution for this problem is the same for both your tool and the system
-version: use the '<tt>--</tt>' marker. When the user specifies '<tt>--</tt>' on
-the command line, it is telling the program that all options after the
-'<tt>--</tt>' should be treated as positional arguments, not options. Thus, we
-can use it like this:</p>
-
-<div class="doc_code"><pre>
- $ spiffygrep -- -foo test.txt
- ...output...
-</pre></div>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="getPosition">Determining absolute position with getPosition()</a>
-</h4>
-<div>
- <p>Sometimes an option can affect or modify the meaning of another option. For
- example, consider <tt>gcc</tt>'s <tt>-x LANG</tt> option. This tells
- <tt>gcc</tt> to ignore the suffix of subsequent positional arguments and force
- the file to be interpreted as if it contained source code in language
- <tt>LANG</tt>. In order to handle this properly, you need to know the
- absolute position of each argument, especially those in lists, so their
- interaction(s) can be applied correctly. This is also useful for options like
- <tt>-llibname</tt> which is actually a positional argument that starts with
- a dash.</p>
- <p>So, generally, the problem is that you have two <tt>cl::list</tt> variables
- that interact in some way. To ensure the correct interaction, you can use the
- <tt>cl::list::getPosition(optnum)</tt> method. This method returns the
- absolute position (as found on the command line) of the <tt>optnum</tt>
- item in the <tt>cl::list</tt>.</p>
- <p>The idiom for usage is like this:</p>
-
- <div class="doc_code"><pre>
- static cl::list<std::string> Files(cl::Positional, cl::OneOrMore);
- static cl::list<std::string> Libraries("l", cl::ZeroOrMore);
-
- int main(int argc, char**argv) {
- // ...
- std::vector<std::string>::iterator fileIt = Files.begin();
- std::vector<std::string>::iterator libIt = Libraries.begin();
- unsigned libPos = 0, filePos = 0;
- while ( 1 ) {
- if ( libIt != Libraries.end() )
- libPos = Libraries.getPosition( libIt - Libraries.begin() );
- else
- libPos = 0;
- if ( fileIt != Files.end() )
- filePos = Files.getPosition( fileIt - Files.begin() );
- else
- filePos = 0;
-
- if ( filePos != 0 && (libPos == 0 || filePos < libPos) ) {
- // Source File Is next
- ++fileIt;
- }
- else if ( libPos != 0 && (filePos == 0 || libPos < filePos) ) {
- // Library is next
- ++libIt;
- }
- else
- break; // we're done with the list
- }
- }</pre></div>
-
- <p>Note that, for compatibility reasons, the <tt>cl::opt</tt> also supports an
- <tt>unsigned getPosition()</tt> option that will provide the absolute position
- of that option. You can apply the same approach as above with a
- <tt>cl::opt</tt> and a <tt>cl::list</tt> option as you can with two lists.</p>
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="cl::ConsumeAfter">The <tt>cl::ConsumeAfter</tt> modifier</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::ConsumeAfter</tt> <a href="#formatting">formatting option</a> is
-used to construct programs that use "interpreter style" option processing. With
-this style of option processing, all arguments specified after the last
-positional argument are treated as special interpreter arguments that are not
-interpreted by the command line argument.</p>
-
-<p>As a concrete example, lets say we are developing a replacement for the
-standard Unix Bourne shell (<tt>/bin/sh</tt>). To run <tt>/bin/sh</tt>, first
-you specify options to the shell itself (like <tt>-x</tt> which turns on trace
-output), then you specify the name of the script to run, then you specify
-arguments to the script. These arguments to the script are parsed by the Bourne
-shell command line option processor, but are not interpreted as options to the
-shell itself. Using the CommandLine library, we would specify this as:</p>
-
-<div class="doc_code"><pre>
-<a href="#cl::opt">cl::opt</a><string> Script(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input script></i>"), <a href="#cl::init">cl::init</a>("-"));
-<a href="#cl::list">cl::list</a><string> Argv(<a href="#cl::ConsumeAfter">cl::ConsumeAfter</a>, <a href="#cl::desc">cl::desc</a>("<i><program arguments>...</i>"));
-<a href="#cl::opt">cl::opt</a><bool> Trace("<i>x</i>", <a href="#cl::desc">cl::desc</a>("<i>Enable trace output</i>"));
-</pre></div>
-
-<p>which automatically provides the help output:</p>
-
-<div class="doc_code"><pre>
-USAGE: spiffysh [options] <b><input script> <program arguments>...</b>
-
-OPTIONS:
- -help - display available options (-help-hidden for more)
- <b>-x - Enable trace output</b>
-</pre></div>
-
-<p>At runtime, if we run our new shell replacement as `<tt>spiffysh -x test.sh
--a -x -y bar</tt>', the <tt>Trace</tt> variable will be set to true, the
-<tt>Script</tt> variable will be set to "<tt>test.sh</tt>", and the
-<tt>Argv</tt> list will contain <tt>["-a", "-x", "-y", "bar"]</tt>, because they
-were specified after the last positional argument (which is the script
-name).</p>
-
-<p>There are several limitations to when <tt>cl::ConsumeAfter</tt> options can
-be specified. For example, only one <tt>cl::ConsumeAfter</tt> can be specified
-per program, there must be at least one <a href="#positional">positional
-argument</a> specified, there must not be any <a href="#cl::list">cl::list</a>
-positional arguments, and the <tt>cl::ConsumeAfter</tt> option should be a <a
-href="#cl::list">cl::list</a> option.</p>
-
-</div>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="storage">Internal vs External Storage</a>
-</h3>
-
-<div>
-
-<p>By default, all command line options automatically hold the value that they
-parse from the command line. This is very convenient in the common case,
-especially when combined with the ability to define command line options in the
-files that use them. This is called the internal storage model.</p>
-
-<p>Sometimes, however, it is nice to separate the command line option processing
-code from the storage of the value parsed. For example, lets say that we have a
-'<tt>-debug</tt>' option that we would like to use to enable debug information
-across the entire body of our program. In this case, the boolean value
-controlling the debug code should be globally accessible (in a header file, for
-example) yet the command line option processing code should not be exposed to
-all of these clients (requiring lots of .cpp files to #include
-<tt>CommandLine.h</tt>).</p>
-
-<p>To do this, set up your .h file with your option, like this for example:</p>
-
-<div class="doc_code">
-<pre>
-<i>// DebugFlag.h - Get access to the '-debug' command line option
-//
-
-// DebugFlag - This boolean is set to true if the '-debug' command line option
-// is specified. This should probably not be referenced directly, instead, use
-// the DEBUG macro below.
-//</i>
-extern bool DebugFlag;
-
-<i>// DEBUG macro - This macro should be used by code to emit debug information.
-// In the '-debug' option is specified on the command line, and if this is a
-// debug build, then the code specified as the option to the macro will be
-// executed. Otherwise it will not be.</i>
-<span class="doc_hilite">#ifdef NDEBUG
-#define DEBUG(X)
-#else
-#define DEBUG(X)</span> do { if (DebugFlag) { X; } } while (0)
-<span class="doc_hilite">#endif</span>
-</pre>
-</div>
-
-<p>This allows clients to blissfully use the <tt>DEBUG()</tt> macro, or the
-<tt>DebugFlag</tt> explicitly if they want to. Now we just need to be able to
-set the <tt>DebugFlag</tt> boolean when the option is set. To do this, we pass
-an additional argument to our command line argument processor, and we specify
-where to fill in with the <a href="#cl::location">cl::location</a>
-attribute:</p>
-
-<div class="doc_code">
-<pre>
-bool DebugFlag; <i>// the actual value</i>
-static <a href="#cl::opt">cl::opt</a><bool, true> <i>// The parser</i>
-Debug("<i>debug</i>", <a href="#cl::desc">cl::desc</a>("<i>Enable debug output</i>"), <a href="#cl::Hidden">cl::Hidden</a>, <a href="#cl::location">cl::location</a>(DebugFlag));
-</pre>
-</div>
-
-<p>In the above example, we specify "<tt>true</tt>" as the second argument to
-the <tt><a href="#cl::opt">cl::opt</a></tt> template, indicating that the
-template should not maintain a copy of the value itself. In addition to this,
-we specify the <tt><a href="#cl::location">cl::location</a></tt> attribute, so
-that <tt>DebugFlag</tt> is automatically set.</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="attributes">Option Attributes</a>
-</h3>
-
-<div>
-
-<p>This section describes the basic attributes that you can specify on
-options.</p>
-
-<ul>
-
-<li>The option name attribute (which is required for all options, except <a
-href="#positional">positional options</a>) specifies what the option name is.
-This option is specified in simple double quotes:
-
-<pre>
-<a href="#cl::opt">cl::opt</a><<b>bool</b>> Quiet("<i>quiet</i>");
-</pre>
-
-</li>
-
-<li><a name="cl::desc">The <b><tt>cl::desc</tt></b></a> attribute specifies a
-description for the option to be shown in the <tt>-help</tt> output for the
-program.</li>
-
-<li><a name="cl::value_desc">The <b><tt>cl::value_desc</tt></b></a> attribute
-specifies a string that can be used to fine tune the <tt>-help</tt> output for
-a command line option. Look <a href="#value_desc_example">here</a> for an
-example.</li>
-
-<li><a name="cl::init">The <b><tt>cl::init</tt></b></a> attribute specifies an
-initial value for a <a href="#cl::opt">scalar</a> option. If this attribute is
-not specified then the command line option value defaults to the value created
-by the default constructor for the type. <b>Warning</b>: If you specify both
-<b><tt>cl::init</tt></b> and <b><tt>cl::location</tt></b> for an option,
-you must specify <b><tt>cl::location</tt></b> first, so that when the
-command-line parser sees <b><tt>cl::init</tt></b>, it knows where to put the
-initial value. (You will get an error at runtime if you don't put them in
-the right order.)</li>
-
-<li><a name="cl::location">The <b><tt>cl::location</tt></b></a> attribute where
-to store the value for a parsed command line option if using external storage.
-See the section on <a href="#storage">Internal vs External Storage</a> for more
-information.</li>
-
-<li><a name="cl::aliasopt">The <b><tt>cl::aliasopt</tt></b></a> attribute
-specifies which option a <tt><a href="#cl::alias">cl::alias</a></tt> option is
-an alias for.</li>
-
-<li><a name="cl::values">The <b><tt>cl::values</tt></b></a> attribute specifies
-the string-to-value mapping to be used by the generic parser. It takes a
-<b>clEnumValEnd terminated</b> list of (option, value, description) triplets
-that
-specify the option name, the value mapped to, and the description shown in the
-<tt>-help</tt> for the tool. Because the generic parser is used most
-frequently with enum values, two macros are often useful:
-
-<ol>
-
-<li><a name="clEnumVal">The <b><tt>clEnumVal</tt></b></a> macro is used as a
-nice simple way to specify a triplet for an enum. This macro automatically
-makes the option name be the same as the enum name. The first option to the
-macro is the enum, the second is the description for the command line
-option.</li>
-
-<li><a name="clEnumValN">The <b><tt>clEnumValN</tt></b></a> macro is used to
-specify macro options where the option name doesn't equal the enum name. For
-this macro, the first argument is the enum value, the second is the flag name,
-and the second is the description.</li>
-
-</ol>
-
-You will get a compile time error if you try to use cl::values with a parser
-that does not support it.</li>
-
-<li><a name="cl::multi_val">The <b><tt>cl::multi_val</tt></b></a>
-attribute specifies that this option takes has multiple values
-(example: <tt>-sectalign segname sectname sectvalue</tt>). This
-attribute takes one unsigned argument - the number of values for the
-option. This attribute is valid only on <tt>cl::list</tt> options (and
-will fail with compile error if you try to use it with other option
-types). It is allowed to use all of the usual modifiers on
-multi-valued options (besides <tt>cl::ValueDisallowed</tt>,
-obviously).</li>
-
-</ul>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="modifiers">Option Modifiers</a>
-</h3>
-
-<div>
-
-<p>Option modifiers are the flags and expressions that you pass into the
-constructors for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
-href="#cl::list">cl::list</a></tt>. These modifiers give you the ability to
-tweak how options are parsed and how <tt>-help</tt> output is generated to fit
-your application well.</p>
-
-<p>These options fall into five main categories:</p>
-
-<ol>
-<li><a href="#hiding">Hiding an option from <tt>-help</tt> output</a></li>
-<li><a href="#numoccurrences">Controlling the number of occurrences
- required and allowed</a></li>
-<li><a href="#valrequired">Controlling whether or not a value must be
- specified</a></li>
-<li><a href="#formatting">Controlling other formatting options</a></li>
-<li><a href="#misc">Miscellaneous option modifiers</a></li>
-</ol>
-
-<p>It is not possible to specify two options from the same category (you'll get
-a runtime error) to a single option, except for options in the miscellaneous
-category. The CommandLine library specifies defaults for all of these settings
-that are the most useful in practice and the most common, which mean that you
-usually shouldn't have to worry about these.</p>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="hiding">Hiding an option from <tt>-help</tt> output</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::NotHidden</tt>, <tt>cl::Hidden</tt>, and
-<tt>cl::ReallyHidden</tt> modifiers are used to control whether or not an option
-appears in the <tt>-help</tt> and <tt>-help-hidden</tt> output for the
-compiled program:</p>
-
-<ul>
-
-<li><a name="cl::NotHidden">The <b><tt>cl::NotHidden</tt></b></a> modifier
-(which is the default for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
-href="#cl::list">cl::list</a></tt> options) indicates the option is to appear
-in both help listings.</li>
-
-<li><a name="cl::Hidden">The <b><tt>cl::Hidden</tt></b></a> modifier (which is the
-default for <tt><a href="#cl::alias">cl::alias</a></tt> options) indicates that
-the option should not appear in the <tt>-help</tt> output, but should appear in
-the <tt>-help-hidden</tt> output.</li>
-
-<li><a name="cl::ReallyHidden">The <b><tt>cl::ReallyHidden</tt></b></a> modifier
-indicates that the option should not appear in any help output.</li>
-
-</ul>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="numoccurrences">Controlling the number of occurrences required and
- allowed</a>
-</h4>
-
-<div>
-
-<p>This group of options is used to control how many time an option is allowed
-(or required) to be specified on the command line of your program. Specifying a
-value for this setting allows the CommandLine library to do error checking for
-you.</p>
-
-<p>The allowed values for this option group are:</p>
-
-<ul>
-
-<li><a name="cl::Optional">The <b><tt>cl::Optional</tt></b></a> modifier (which
-is the default for the <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
-href="#cl::alias">cl::alias</a></tt> classes) indicates that your program will
-allow either zero or one occurrence of the option to be specified.</li>
-
-<li><a name="cl::ZeroOrMore">The <b><tt>cl::ZeroOrMore</tt></b></a> modifier
-(which is the default for the <tt><a href="#cl::list">cl::list</a></tt> class)
-indicates that your program will allow the option to be specified zero or more
-times.</li>
-
-<li><a name="cl::Required">The <b><tt>cl::Required</tt></b></a> modifier
-indicates that the specified option must be specified exactly one time.</li>
-
-<li><a name="cl::OneOrMore">The <b><tt>cl::OneOrMore</tt></b></a> modifier
-indicates that the option must be specified at least one time.</li>
-
-<li>The <b><tt>cl::ConsumeAfter</tt></b> modifier is described in the <a
-href="#positional">Positional arguments section</a>.</li>
-
-</ul>
-
-<p>If an option is not specified, then the value of the option is equal to the
-value specified by the <tt><a href="#cl::init">cl::init</a></tt> attribute. If
-the <tt><a href="#cl::init">cl::init</a></tt> attribute is not specified, the
-option value is initialized with the default constructor for the data type.</p>
-
-<p>If an option is specified multiple times for an option of the <tt><a
-href="#cl::opt">cl::opt</a></tt> class, only the last value will be
-retained.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="valrequired">Controlling whether or not a value must be specified</a>
-</h4>
-
-<div>
-
-<p>This group of options is used to control whether or not the option allows a
-value to be present. In the case of the CommandLine library, a value is either
-specified with an equal sign (e.g. '<tt>-index-depth=17</tt>') or as a trailing
-string (e.g. '<tt>-o a.out</tt>').</p>
-
-<p>The allowed values for this option group are:</p>
-
-<ul>
-
-<li><a name="cl::ValueOptional">The <b><tt>cl::ValueOptional</tt></b></a> modifier
-(which is the default for <tt>bool</tt> typed options) specifies that it is
-acceptable to have a value, or not. A boolean argument can be enabled just by
-appearing on the command line, or it can have an explicit '<tt>-foo=true</tt>'.
-If an option is specified with this mode, it is illegal for the value to be
-provided without the equal sign. Therefore '<tt>-foo true</tt>' is illegal. To
-get this behavior, you must use the <a
-href="#cl::ValueRequired">cl::ValueRequired</a> modifier.</li>
-
-<li><a name="cl::ValueRequired">The <b><tt>cl::ValueRequired</tt></b></a> modifier
-(which is the default for all other types except for <a
-href="#onealternative">unnamed alternatives using the generic parser</a>)
-specifies that a value must be provided. This mode informs the command line
-library that if an option is not provides with an equal sign, that the next
-argument provided must be the value. This allows things like '<tt>-o
-a.out</tt>' to work.</li>
-
-<li><a name="cl::ValueDisallowed">The <b><tt>cl::ValueDisallowed</tt></b></a>
-modifier (which is the default for <a href="#onealternative">unnamed
-alternatives using the generic parser</a>) indicates that it is a runtime error
-for the user to specify a value. This can be provided to disallow users from
-providing options to boolean options (like '<tt>-foo=true</tt>').</li>
-
-</ul>
-
-<p>In general, the default values for this option group work just like you would
-want them to. As mentioned above, you can specify the <a
-href="#cl::ValueDisallowed">cl::ValueDisallowed</a> modifier to a boolean
-argument to restrict your command line parser. These options are mostly useful
-when <a href="#extensionguide">extending the library</a>.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="formatting">Controlling other formatting options</a>
-</h4>
-
-<div>
-
-<p>The formatting option group is used to specify that the command line option
-has special abilities and is otherwise different from other command line
-arguments. As usual, you can only specify one of these arguments at most.</p>
-
-<ul>
-
-<li><a name="cl::NormalFormatting">The <b><tt>cl::NormalFormatting</tt></b></a>
-modifier (which is the default all options) specifies that this option is
-"normal".</li>
-
-<li><a name="cl::Positional">The <b><tt>cl::Positional</tt></b></a> modifier
-specifies that this is a positional argument that does not have a command line
-option associated with it. See the <a href="#positional">Positional
-Arguments</a> section for more information.</li>
-
-<li>The <b><a href="#cl::ConsumeAfter"><tt>cl::ConsumeAfter</tt></a></b> modifier
-specifies that this option is used to capture "interpreter style" arguments. See <a href="#cl::ConsumeAfter">this section for more information</a>.</li>
-
-<li><a name="cl::Prefix">The <b><tt>cl::Prefix</tt></b></a> modifier specifies
-that this option prefixes its value. With 'Prefix' options, the equal sign does
-not separate the value from the option name specified. Instead, the value is
-everything after the prefix, including any equal sign if present. This is useful
-for processing odd arguments like <tt>-lmalloc</tt> and <tt>-L/usr/lib</tt> in a
-linker tool or <tt>-DNAME=value</tt> in a compiler tool. Here, the
-'<tt>l</tt>', '<tt>D</tt>' and '<tt>L</tt>' options are normal string (or list)
-options, that have the <b><tt><a href="#cl::Prefix">cl::Prefix</a></tt></b>
-modifier added to allow the CommandLine library to recognize them. Note that
-<b><tt><a href="#cl::Prefix">cl::Prefix</a></tt></b> options must not have the
-<b><tt><a href="#cl::ValueDisallowed">cl::ValueDisallowed</a></tt></b> modifier
-specified.</li>
-
-<li><a name="cl::Grouping">The <b><tt>cl::Grouping</tt></b></a> modifier is used
-to implement Unix-style tools (like <tt>ls</tt>) that have lots of single letter
-arguments, but only require a single dash. For example, the '<tt>ls -labF</tt>'
-command actually enables four different options, all of which are single
-letters. Note that <b><tt><a href="#cl::Grouping">cl::Grouping</a></tt></b>
-options cannot have values.</li>
-
-</ul>
-
-<p>The CommandLine library does not restrict how you use the <b><tt><a
-href="#cl::Prefix">cl::Prefix</a></tt></b> or <b><tt><a
-href="#cl::Grouping">cl::Grouping</a></tt></b> modifiers, but it is possible to
-specify ambiguous argument settings. Thus, it is possible to have multiple
-letter options that are prefix or grouping options, and they will still work as
-designed.</p>
-
-<p>To do this, the CommandLine library uses a greedy algorithm to parse the
-input option into (potentially multiple) prefix and grouping options. The
-strategy basically looks like this:</p>
-
-<div class="doc_code"><tt>parse(string OrigInput) {</tt>
-
-<ol>
-<li><tt>string input = OrigInput;</tt>
-<li><tt>if (isOption(input)) return getOption(input).parse();</tt> <i>// Normal option</i>
-<li><tt>while (!isOption(input) && !input.empty()) input.pop_back();</tt> <i>// Remove the last letter</i>
-<li><tt>if (input.empty()) return error();</tt> <i>// No matching option</i>
-<li><tt>if (getOption(input).isPrefix())<br>
- return getOption(input).parse(input);</tt>
-<li><tt>while (!input.empty()) { <i>// Must be grouping options</i><br>
- getOption(input).parse();<br>
- OrigInput.erase(OrigInput.begin(), OrigInput.begin()+input.length());<br>
- input = OrigInput;<br>
- while (!isOption(input) && !input.empty()) input.pop_back();<br>
-}</tt>
-<li><tt>if (!OrigInput.empty()) error();</tt></li>
-</ol>
-
-<p><tt>}</tt></p>
-</div>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="misc">Miscellaneous option modifiers</a>
-</h4>
-
-<div>
-
-<p>The miscellaneous option modifiers are the only flags where you can specify
-more than one flag from the set: they are not mutually exclusive. These flags
-specify boolean properties that modify the option.</p>
-
-<ul>
-
-<li><a name="cl::CommaSeparated">The <b><tt>cl::CommaSeparated</tt></b></a> modifier
-indicates that any commas specified for an option's value should be used to
-split the value up into multiple values for the option. For example, these two
-options are equivalent when <tt>cl::CommaSeparated</tt> is specified:
-"<tt>-foo=a -foo=b -foo=c</tt>" and "<tt>-foo=a,b,c</tt>". This option only
-makes sense to be used in a case where the option is allowed to accept one or
-more values (i.e. it is a <a href="#cl::list">cl::list</a> option).</li>
-
-<li><a name="cl::PositionalEatsArgs">The
-<b><tt>cl::PositionalEatsArgs</tt></b></a> modifier (which only applies to
-positional arguments, and only makes sense for lists) indicates that positional
-argument should consume any strings after it (including strings that start with
-a "-") up until another recognized positional argument. For example, if you
-have two "eating" positional arguments, "<tt>pos1</tt>" and "<tt>pos2</tt>", the
-string "<tt>-pos1 -foo -bar baz -pos2 -bork</tt>" would cause the "<tt>-foo -bar
--baz</tt>" strings to be applied to the "<tt>-pos1</tt>" option and the
-"<tt>-bork</tt>" string to be applied to the "<tt>-pos2</tt>" option.</li>
-
-<li><a name="cl::Sink">The <b><tt>cl::Sink</tt></b></a> modifier is
-used to handle unknown options. If there is at least one option with
-<tt>cl::Sink</tt> modifier specified, the parser passes
-unrecognized option strings to it as values instead of signaling an
-error. As with <tt>cl::CommaSeparated</tt>, this modifier
-only makes sense with a <a href="#cl::list">cl::list</a> option.</li>
-
-</ul>
-
-<p>So far, these are the only three miscellaneous option modifiers.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="response">Response files</a>
-</h4>
-
-<div>
-
-<p>Some systems, such as certain variants of Microsoft Windows and
-some older Unices have a relatively low limit on command-line
-length. It is therefore customary to use the so-called 'response
-files' to circumvent this restriction. These files are mentioned on
-the command-line (using the "@file") syntax. The program reads these
-files and inserts the contents into argv, thereby working around the
-command-line length limits. Response files are enabled by an optional
-fourth argument to
-<a href="#cl::ParseEnvironmentOptions"><tt>cl::ParseEnvironmentOptions</tt></a>
-and
-<a href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>.
-</p>
-
-</div>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="toplevel">Top-Level Classes and Functions</a>
-</h3>
-
-<div>
-
-<p>Despite all of the built-in flexibility, the CommandLine option library
-really only consists of one function (<a
-href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>)
-and three main classes: <a href="#cl::opt"><tt>cl::opt</tt></a>, <a
-href="#cl::list"><tt>cl::list</tt></a>, and <a
-href="#cl::alias"><tt>cl::alias</tt></a>. This section describes these three
-classes in detail.</p>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="cl::ParseCommandLineOptions">The <tt>cl::ParseCommandLineOptions</tt>
- function</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::ParseCommandLineOptions</tt> function is designed to be called
-directly from <tt>main</tt>, and is used to fill in the values of all of the
-command line option variables once <tt>argc</tt> and <tt>argv</tt> are
-available.</p>
-
-<p>The <tt>cl::ParseCommandLineOptions</tt> function requires two parameters
-(<tt>argc</tt> and <tt>argv</tt>), but may also take an optional third parameter
-which holds <a href="#description">additional extra text</a> to emit when the
-<tt>-help</tt> option is invoked, and a fourth boolean parameter that enables
-<a href="#response">response files</a>.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="cl::ParseEnvironmentOptions">The <tt>cl::ParseEnvironmentOptions</tt>
- function</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::ParseEnvironmentOptions</tt> function has mostly the same effects
-as <a
-href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>,
-except that it is designed to take values for options from an environment
-variable, for those cases in which reading the command line is not convenient or
-desired. It fills in the values of all the command line option variables just
-like <a
-href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>
-does.</p>
-
-<p>It takes four parameters: the name of the program (since <tt>argv</tt> may
-not be available, it can't just look in <tt>argv[0]</tt>), the name of the
-environment variable to examine, the optional
-<a href="#description">additional extra text</a> to emit when the
-<tt>-help</tt> option is invoked, and the boolean
-switch that controls whether <a href="#response">response files</a>
-should be read.</p>
-
-<p><tt>cl::ParseEnvironmentOptions</tt> will break the environment
-variable's value up into words and then process them using
-<a href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>.
-<b>Note:</b> Currently <tt>cl::ParseEnvironmentOptions</tt> does not support
-quoting, so an environment variable containing <tt>-option "foo bar"</tt> will
-be parsed as three words, <tt>-option</tt>, <tt>"foo</tt>, and <tt>bar"</tt>,
-which is different from what you would get from the shell with the same
-input.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="cl::SetVersionPrinter">The <tt>cl::SetVersionPrinter</tt>
- function</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::SetVersionPrinter</tt> function is designed to be called
-directly from <tt>main</tt> and <i>before</i>
-<tt>cl::ParseCommandLineOptions</tt>. Its use is optional. It simply arranges
-for a function to be called in response to the <tt>--version</tt> option instead
-of having the <tt>CommandLine</tt> library print out the usual version string
-for LLVM. This is useful for programs that are not part of LLVM but wish to use
-the <tt>CommandLine</tt> facilities. Such programs should just define a small
-function that takes no arguments and returns <tt>void</tt> and that prints out
-whatever version information is appropriate for the program. Pass the address
-of that function to <tt>cl::SetVersionPrinter</tt> to arrange for it to be
-called when the <tt>--version</tt> option is given by the user.</p>
-
-</div>
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="cl::opt">The <tt>cl::opt</tt> class</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::opt</tt> class is the class used to represent scalar command line
-options, and is the one used most of the time. It is a templated class which
-can take up to three arguments (all except for the first have default values
-though):</p>
-
-<div class="doc_code"><pre>
-<b>namespace</b> cl {
- <b>template</b> <<b>class</b> DataType, <b>bool</b> ExternalStorage = <b>false</b>,
- <b>class</b> ParserClass = parser<DataType> >
- <b>class</b> opt;
-}
-</pre></div>
-
-<p>The first template argument specifies what underlying data type the command
-line argument is, and is used to select a default parser implementation. The
-second template argument is used to specify whether the option should contain
-the storage for the option (the default) or whether external storage should be
-used to contain the value parsed for the option (see <a href="#storage">Internal
-vs External Storage</a> for more information).</p>
-
-<p>The third template argument specifies which parser to use. The default value
-selects an instantiation of the <tt>parser</tt> class based on the underlying
-data type of the option. In general, this default works well for most
-applications, so this option is only used when using a <a
-href="#customparser">custom parser</a>.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="cl::list">The <tt>cl::list</tt> class</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::list</tt> class is the class used to represent a list of command
-line options. It too is a templated class which can take up to three
-arguments:</p>
-
-<div class="doc_code"><pre>
-<b>namespace</b> cl {
- <b>template</b> <<b>class</b> DataType, <b>class</b> Storage = <b>bool</b>,
- <b>class</b> ParserClass = parser<DataType> >
- <b>class</b> list;
-}
-</pre></div>
-
-<p>This class works the exact same as the <a
-href="#cl::opt"><tt>cl::opt</tt></a> class, except that the second argument is
-the <b>type</b> of the external storage, not a boolean value. For this class,
-the marker type '<tt>bool</tt>' is used to indicate that internal storage should
-be used.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="cl::bits">The <tt>cl::bits</tt> class</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::bits</tt> class is the class used to represent a list of command
-line options in the form of a bit vector. It is also a templated class which
-can take up to three arguments:</p>
-
-<div class="doc_code"><pre>
-<b>namespace</b> cl {
- <b>template</b> <<b>class</b> DataType, <b>class</b> Storage = <b>bool</b>,
- <b>class</b> ParserClass = parser<DataType> >
- <b>class</b> bits;
-}
-</pre></div>
-
-<p>This class works the exact same as the <a
-href="#cl::opt"><tt>cl::lists</tt></a> class, except that the second argument
-must be of <b>type</b> <tt>unsigned</tt> if external storage is used.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="cl::alias">The <tt>cl::alias</tt> class</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::alias</tt> class is a nontemplated class that is used to form
-aliases for other arguments.</p>
-
-<div class="doc_code"><pre>
-<b>namespace</b> cl {
- <b>class</b> alias;
-}
-</pre></div>
-
-<p>The <a href="#cl::aliasopt"><tt>cl::aliasopt</tt></a> attribute should be
-used to specify which option this is an alias for. Alias arguments default to
-being <a href="#cl::Hidden">Hidden</a>, and use the aliased options parser to do
-the conversion from string to data.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<h4>
- <a name="cl::extrahelp">The <tt>cl::extrahelp</tt> class</a>
-</h4>
-
-<div>
-
-<p>The <tt>cl::extrahelp</tt> class is a nontemplated class that allows extra
-help text to be printed out for the <tt>-help</tt> option.</p>
-
-<div class="doc_code"><pre>
-<b>namespace</b> cl {
- <b>struct</b> extrahelp;
-}
-</pre></div>
-
-<p>To use the extrahelp, simply construct one with a <tt>const char*</tt>
-parameter to the constructor. The text passed to the constructor will be printed
-at the bottom of the help message, verbatim. Note that multiple
-<tt>cl::extrahelp</tt> <b>can</b> be used, but this practice is discouraged. If
-your tool needs to print additional help information, put all that help into a
-single <tt>cl::extrahelp</tt> instance.</p>
-<p>For example:</p>
-<div class="doc_code"><pre>
- cl::extrahelp("\nADDITIONAL HELP:\n\n This is the extra help\n");
-</pre></div>
-</div>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="builtinparsers">Builtin parsers</a>
-</h3>
-
-<div>
-
-<p>Parsers control how the string value taken from the command line is
-translated into a typed value, suitable for use in a C++ program. By default,
-the CommandLine library uses an instance of <tt>parser<type></tt> if the
-command line option specifies that it uses values of type '<tt>type</tt>'.
-Because of this, custom option processing is specified with specializations of
-the '<tt>parser</tt>' class.</p>
-
-<p>The CommandLine library provides the following builtin parser
-specializations, which are sufficient for most applications. It can, however,
-also be extended to work with new data types and new ways of interpreting the
-same data. See the <a href="#customparser">Writing a Custom Parser</a> for more
-details on this type of library extension.</p>
-
-<ul>
-
-<li><a name="genericparser">The <b>generic <tt>parser<t></tt> parser</b></a>
-can be used to map strings values to any data type, through the use of the <a
-href="#cl::values">cl::values</a> property, which specifies the mapping
-information. The most common use of this parser is for parsing enum values,
-which allows you to use the CommandLine library for all of the error checking to
-make sure that only valid enum values are specified (as opposed to accepting
-arbitrary strings). Despite this, however, the generic parser class can be used
-for any data type.</li>
-
-<li><a name="boolparser">The <b><tt>parser<bool></tt> specialization</b></a>
-is used to convert boolean strings to a boolean value. Currently accepted
-strings are "<tt>true</tt>", "<tt>TRUE</tt>", "<tt>True</tt>", "<tt>1</tt>",
-"<tt>false</tt>", "<tt>FALSE</tt>", "<tt>False</tt>", and "<tt>0</tt>".</li>
-
-<li><a name="boolOrDefaultparser">The <b><tt>parser<boolOrDefault></tt>
- specialization</b></a> is used for cases where the value is boolean,
-but we also need to know whether the option was specified at all. boolOrDefault
-is an enum with 3 values, BOU_UNSET, BOU_TRUE and BOU_FALSE. This parser accepts
-the same strings as <b><tt>parser<bool></tt></b>.</li>
-
-<li><a name="stringparser">The <b><tt>parser<string></tt>
-specialization</b></a> simply stores the parsed string into the string value
-specified. No conversion or modification of the data is performed.</li>
-
-<li><a name="intparser">The <b><tt>parser<int></tt> specialization</b></a>
-uses the C <tt>strtol</tt> function to parse the string input. As such, it will
-accept a decimal number (with an optional '+' or '-' prefix) which must start
-with a non-zero digit. It accepts octal numbers, which are identified with a
-'<tt>0</tt>' prefix digit, and hexadecimal numbers with a prefix of
-'<tt>0x</tt>' or '<tt>0X</tt>'.</li>
-
-<li><a name="doubleparser">The <b><tt>parser<double></tt></b></a> and
-<b><tt>parser<float></tt> specializations</b> use the standard C
-<tt>strtod</tt> function to convert floating point strings into floating point
-values. As such, a broad range of string formats is supported, including
-exponential notation (ex: <tt>1.7e15</tt>) and properly supports locales.
-</li>
-
-</ul>
-
-</div>
-
-</div>
-
-<!-- *********************************************************************** -->
-<h2>
- <a name="extensionguide">Extension Guide</a>
-</h2>
-<!-- *********************************************************************** -->
-
-<div>
-
-<p>Although the CommandLine library has a lot of functionality built into it
-already (as discussed previously), one of its true strengths lie in its
-extensibility. This section discusses how the CommandLine library works under
-the covers and illustrates how to do some simple, common, extensions.</p>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="customparser">Writing a custom parser</a>
-</h3>
-
-<div>
-
-<p>One of the simplest and most common extensions is the use of a custom parser.
-As <a href="#builtinparsers">discussed previously</a>, parsers are the portion
-of the CommandLine library that turns string input from the user into a
-particular parsed data type, validating the input in the process.</p>
-
-<p>There are two ways to use a new parser:</p>
-
-<ol>
-
-<li>
-
-<p>Specialize the <a href="#genericparser"><tt>cl::parser</tt></a> template for
-your custom data type.<p>
-
-<p>This approach has the advantage that users of your custom data type will
-automatically use your custom parser whenever they define an option with a value
-type of your data type. The disadvantage of this approach is that it doesn't
-work if your fundamental data type is something that is already supported.</p>
-
-</li>
-
-<li>
-
-<p>Write an independent class, using it explicitly from options that need
-it.</p>
-
-<p>This approach works well in situations where you would line to parse an
-option using special syntax for a not-very-special data-type. The drawback of
-this approach is that users of your parser have to be aware that they are using
-your parser instead of the builtin ones.</p>
-
-</li>
-
-</ol>
-
-<p>To guide the discussion, we will discuss a custom parser that accepts file
-sizes, specified with an optional unit after the numeric size. For example, we
-would like to parse "102kb", "41M", "1G" into the appropriate integer value. In
-this case, the underlying data type we want to parse into is
-'<tt>unsigned</tt>'. We choose approach #2 above because we don't want to make
-this the default for all <tt>unsigned</tt> options.</p>
-
-<p>To start out, we declare our new <tt>FileSizeParser</tt> class:</p>
-
-<div class="doc_code"><pre>
-<b>struct</b> FileSizeParser : <b>public</b> cl::basic_parser<<b>unsigned</b>> {
- <i>// parse - Return true on error.</i>
- <b>bool</b> parse(cl::Option &O, <b>const char</b> *ArgName, <b>const</b> std::string &ArgValue,
- <b>unsigned</b> &Val);
-};
-</pre></div>
-
-<p>Our new class inherits from the <tt>cl::basic_parser</tt> template class to
-fill in the default, boiler plate code for us. We give it the data type that
-we parse into, the last argument to the <tt>parse</tt> method, so that clients of
-our custom parser know what object type to pass in to the parse method. (Here we
-declare that we parse into '<tt>unsigned</tt>' variables.)</p>
-
-<p>For most purposes, the only method that must be implemented in a custom
-parser is the <tt>parse</tt> method. The <tt>parse</tt> method is called
-whenever the option is invoked, passing in the option itself, the option name,
-the string to parse, and a reference to a return value. If the string to parse
-is not well-formed, the parser should output an error message and return true.
-Otherwise it should return false and set '<tt>Val</tt>' to the parsed value. In
-our example, we implement <tt>parse</tt> as:</p>
-
-<div class="doc_code"><pre>
-<b>bool</b> FileSizeParser::parse(cl::Option &O, <b>const char</b> *ArgName,
- <b>const</b> std::string &Arg, <b>unsigned</b> &Val) {
- <b>const char</b> *ArgStart = Arg.c_str();
- <b>char</b> *End;
-
- <i>// Parse integer part, leaving 'End' pointing to the first non-integer char</i>
- Val = (unsigned)strtol(ArgStart, &End, 0);
-
- <b>while</b> (1) {
- <b>switch</b> (*End++) {
- <b>case</b> 0: <b>return</b> false; <i>// No error</i>
- <b>case</b> 'i': <i>// Ignore the 'i' in KiB if people use that</i>
- <b>case</b> 'b': <b>case</b> 'B': <i>// Ignore B suffix</i>
- <b>break</b>;
-
- <b>case</b> 'g': <b>case</b> 'G': Val *= 1024*1024*1024; <b>break</b>;
- <b>case</b> 'm': <b>case</b> 'M': Val *= 1024*1024; <b>break</b>;
- <b>case</b> 'k': <b>case</b> 'K': Val *= 1024; <b>break</b>;
-
- default:
- <i>// Print an error message if unrecognized character!</i>
- <b>return</b> O.error("'" + Arg + "' value invalid for file size argument!");
- }
- }
-}
-</pre></div>
-
-<p>This function implements a very simple parser for the kinds of strings we are
-interested in. Although it has some holes (it allows "<tt>123KKK</tt>" for
-example), it is good enough for this example. Note that we use the option
-itself to print out the error message (the <tt>error</tt> method always returns
-true) in order to get a nice error message (shown below). Now that we have our
-parser class, we can use it like this:</p>
-
-<div class="doc_code"><pre>
-<b>static</b> <a href="#cl::opt">cl::opt</a><<b>unsigned</b>, <b>false</b>, FileSizeParser>
-MFS(<i>"max-file-size"</i>, <a href="#cl::desc">cl::desc</a>(<i>"Maximum file size to accept"</i>),
- <a href="#cl::value_desc">cl::value_desc</a>("<i>size</i>"));
-</pre></div>
-
-<p>Which adds this to the output of our program:</p>
-
-<div class="doc_code"><pre>
-OPTIONS:
- -help - display available options (-help-hidden for more)
- ...
- <b>-max-file-size=<size> - Maximum file size to accept</b>
-</pre></div>
-
-<p>And we can test that our parse works correctly now (the test program just
-prints out the max-file-size argument value):</p>
-
-<div class="doc_code"><pre>
-$ ./test
-MFS: 0
-$ ./test -max-file-size=123MB
-MFS: 128974848
-$ ./test -max-file-size=3G
-MFS: 3221225472
-$ ./test -max-file-size=dog
--max-file-size option: 'dog' value invalid for file size argument!
-</pre></div>
-
-<p>It looks like it works. The error message that we get is nice and helpful,
-and we seem to accept reasonable file sizes. This wraps up the "custom parser"
-tutorial.</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="explotingexternal">Exploiting external storage</a>
-</h3>
-
-<div>
- <p>Several of the LLVM libraries define static <tt>cl::opt</tt> instances that
- will automatically be included in any program that links with that library.
- This is a feature. However, sometimes it is necessary to know the value of the
- command line option outside of the library. In these cases the library does or
- should provide an external storage location that is accessible to users of the
- library. Examples of this include the <tt>llvm::DebugFlag</tt> exported by the
- <tt>lib/Support/Debug.cpp</tt> file and the <tt>llvm::TimePassesIsEnabled</tt>
- flag exported by the <tt>lib/VMCore/PassManager.cpp</tt> file.</p>
-
-<p>TODO: complete this section</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="dynamicopts">Dynamically adding command line options</a>
-</h3>
-
-<div>
-
-<p>TODO: fill in this section</p>
-
-</div>
-
-</div>
-
-<!-- *********************************************************************** -->
-
-<hr>
-<address>
- <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
- src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
- <a href="http://validator.w3.org/check/referer"><img
- src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
-
- <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
- <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
- Last modified: $Date$
-</address>
-
-</body>
-</html>
--- /dev/null
+.. _commandline:
+
+==============================
+CommandLine 2.0 Library Manual
+==============================
+
+Introduction
+============
+
+This document describes the CommandLine argument processing library. It will
+show you how to use it, and what it can do. The CommandLine library uses a
+declarative approach to specifying the command line options that your program
+takes. By default, these options declarations implicitly hold the value parsed
+for the option declared (of course this `can be changed`_).
+
+Although there are a **lot** of command line argument parsing libraries out
+there in many different languages, none of them fit well with what I needed. By
+looking at the features and problems of other libraries, I designed the
+CommandLine library to have the following features:
+
+#. Speed: The CommandLine library is very quick and uses little resources. The
+ parsing time of the library is directly proportional to the number of
+ arguments parsed, not the number of options recognized. Additionally,
+ command line argument values are captured transparently into user defined
+ global variables, which can be accessed like any other variable (and with the
+ same performance).
+
+#. Type Safe: As a user of CommandLine, you don't have to worry about
+ remembering the type of arguments that you want (is it an int? a string? a
+ bool? an enum?) and keep casting it around. Not only does this help prevent
+ error prone constructs, it also leads to dramatically cleaner source code.
+
+#. No subclasses required: To use CommandLine, you instantiate variables that
+ correspond to the arguments that you would like to capture, you don't
+ subclass a parser. This means that you don't have to write **any**
+ boilerplate code.
+
+#. Globally accessible: Libraries can specify command line arguments that are
+ automatically enabled in any tool that links to the library. This is
+ possible because the application doesn't have to keep a list of arguments to
+ pass to the parser. This also makes supporting `dynamically loaded options`_
+ trivial.
+
+#. Cleaner: CommandLine supports enum and other types directly, meaning that
+ there is less error and more security built into the library. You don't have
+ to worry about whether your integral command line argument accidentally got
+ assigned a value that is not valid for your enum type.
+
+#. Powerful: The CommandLine library supports many different types of arguments,
+ from simple `boolean flags`_ to `scalars arguments`_ (`strings`_,
+ `integers`_, `enums`_, `doubles`_), to `lists of arguments`_. This is
+ possible because CommandLine is...
+
+#. Extensible: It is very simple to add a new argument type to CommandLine.
+ Simply specify the parser that you want to use with the command line option
+ when you declare it. `Custom parsers`_ are no problem.
+
+#. Labor Saving: The CommandLine library cuts down on the amount of grunt work
+ that you, the user, have to do. For example, it automatically provides a
+ ``-help`` option that shows the available command line options for your tool.
+ Additionally, it does most of the basic correctness checking for you.
+
+#. Capable: The CommandLine library can handle lots of different forms of
+ options often found in real programs. For example, `positional`_ arguments,
+ ``ls`` style `grouping`_ options (to allow processing '``ls -lad``'
+ naturally), ``ld`` style `prefix`_ options (to parse '``-lmalloc
+ -L/usr/lib``'), and interpreter style options.
+
+This document will hopefully let you jump in and start using CommandLine in your
+utility quickly and painlessly. Additionally it should be a simple reference
+manual to figure out how stuff works. If it is failing in some area (or you
+want an extension to the library), nag the author, `Chris
+Lattner <mailto:sabre@nondot.org>`_.
+
+Quick Start Guide
+=================
+
+This section of the manual runs through a simple CommandLine'ification of a
+basic compiler tool. This is intended to show you how to jump into using the
+CommandLine library in your own program, and show you some of the cool things it
+can do.
+
+To start out, you need to include the CommandLine header file into your program:
+
+.. code-block:: c++
+
+ #include "llvm/Support/CommandLine.h"
+
+Additionally, you need to add this as the first line of your main program:
+
+.. code-block:: c++
+
+ int main(int argc, char **argv) {
+ cl::ParseCommandLineOptions(argc, argv);
+ ...
+ }
+
+... which actually parses the arguments and fills in the variable declarations.
+
+Now that you are ready to support command line arguments, we need to tell the
+system which ones we want, and what type of arguments they are. The CommandLine
+library uses a declarative syntax to model command line arguments with the
+global variable declarations that capture the parsed values. This means that
+for every command line option that you would like to support, there should be a
+global variable declaration to capture the result. For example, in a compiler,
+we would like to support the Unix-standard '``-o <filename>``' option to specify
+where to put the output. With the CommandLine library, this is represented like
+this:
+
+.. _scalars arguments:
+.. _here:
+
+.. code-block:: c++
+
+ cl::opt<string> OutputFilename("o", cl::desc("Specify output filename"), cl::value_desc("filename"));
+
+This declares a global variable "``OutputFilename``" that is used to capture the
+result of the "``o``" argument (first parameter). We specify that this is a
+simple scalar option by using the "``cl::opt``" template (as opposed to the
+"``cl::list``" template), and tell the CommandLine library that the data
+type that we are parsing is a string.
+
+The second and third parameters (which are optional) are used to specify what to
+output for the "``-help``" option. In this case, we get a line that looks like
+this:
+
+::
+
+ USAGE: compiler [options]
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+
+Because we specified that the command line option should parse using the
+``string`` data type, the variable declared is automatically usable as a real
+string in all contexts that a normal C++ string object may be used. For
+example:
+
+.. code-block:: c++
+
+ ...
+ std::ofstream Output(OutputFilename.c_str());
+ if (Output.good()) ...
+ ...
+
+There are many different options that you can use to customize the command line
+option handling library, but the above example shows the general interface to
+these options. The options can be specified in any order, and are specified
+with helper functions like `cl::desc(...)`_, so there are no positional
+dependencies to remember. The available options are discussed in detail in the
+`Reference Guide`_.
+
+Continuing the example, we would like to have our compiler take an input
+filename as well as an output filename, but we do not want the input filename to
+be specified with a hyphen (ie, not ``-filename.c``). To support this style of
+argument, the CommandLine library allows for `positional`_ arguments to be
+specified for the program. These positional arguments are filled with command
+line parameters that are not in option form. We use this feature like this:
+
+.. code-block:: c++
+
+
+ cl::opt<string> InputFilename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
+
+This declaration indicates that the first positional argument should be treated
+as the input filename. Here we use the `cl::init`_ option to specify an initial
+value for the command line option, which is used if the option is not specified
+(if you do not specify a `cl::init`_ modifier for an option, then the default
+constructor for the data type is used to initialize the value). Command line
+options default to being optional, so if we would like to require that the user
+always specify an input filename, we would add the `cl::Required`_ flag, and we
+could eliminate the `cl::init`_ modifier, like this:
+
+.. code-block:: c++
+
+ cl::opt<string> InputFilename(cl::Positional, cl::desc("<input file>"), cl::Required);
+
+Again, the CommandLine library does not require the options to be specified in
+any particular order, so the above declaration is equivalent to:
+
+.. code-block:: c++
+
+ cl::opt<string> InputFilename(cl::Positional, cl::Required, cl::desc("<input file>"));
+
+By simply adding the `cl::Required`_ flag, the CommandLine library will
+automatically issue an error if the argument is not specified, which shifts all
+of the command line option verification code out of your application into the
+library. This is just one example of how using flags can alter the default
+behaviour of the library, on a per-option basis. By adding one of the
+declarations above, the ``-help`` option synopsis is now extended to:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+
+... indicating that an input filename is expected.
+
+Boolean Arguments
+-----------------
+
+In addition to input and output filenames, we would like the compiler example to
+support three boolean flags: "``-f``" to force writing binary output to a
+terminal, "``--quiet``" to enable quiet mode, and "``-q``" for backwards
+compatibility with some of our users. We can support these by declaring options
+of boolean type like this:
+
+.. code-block:: c++
+
+ cl::opt<bool> Force ("f", cl::desc("Enable binary output on terminals"));
+ cl::opt<bool> Quiet ("quiet", cl::desc("Don't print informational messages"));
+ cl::opt<bool> Quiet2("q", cl::desc("Don't print informational messages"), cl::Hidden);
+
+This does what you would expect: it declares three boolean variables
+("``Force``", "``Quiet``", and "``Quiet2``") to recognize these options. Note
+that the "``-q``" option is specified with the "`cl::Hidden`_" flag. This
+modifier prevents it from being shown by the standard "``-help``" output (note
+that it is still shown in the "``-help-hidden``" output).
+
+The CommandLine library uses a `different parser`_ for different data types.
+For example, in the string case, the argument passed to the option is copied
+literally into the content of the string variable... we obviously cannot do that
+in the boolean case, however, so we must use a smarter parser. In the case of
+the boolean parser, it allows no options (in which case it assigns the value of
+true to the variable), or it allows the values "``true``" or "``false``" to be
+specified, allowing any of the following inputs:
+
+::
+
+ compiler -f # No value, 'Force' == true
+ compiler -f=true # Value specified, 'Force' == true
+ compiler -f=TRUE # Value specified, 'Force' == true
+ compiler -f=FALSE # Value specified, 'Force' == false
+
+... you get the idea. The `bool parser`_ just turns the string values into
+boolean values, and rejects things like '``compiler -f=foo``'. Similarly, the
+`float`_, `double`_, and `int`_ parsers work like you would expect, using the
+'``strtol``' and '``strtod``' C library calls to parse the string value into the
+specified data type.
+
+With the declarations above, "``compiler -help``" emits this:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ -f - Enable binary output on terminals
+ -o - Override output filename
+ -quiet - Don't print informational messages
+ -help - display available options (-help-hidden for more)
+
+and "``compiler -help-hidden``" prints this:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ -f - Enable binary output on terminals
+ -o - Override output filename
+ -q - Don't print informational messages
+ -quiet - Don't print informational messages
+ -help - display available options (-help-hidden for more)
+
+This brief example has shown you how to use the '`cl::opt`_' class to parse
+simple scalar command line arguments. In addition to simple scalar arguments,
+the CommandLine library also provides primitives to support CommandLine option
+`aliases`_, and `lists`_ of options.
+
+.. _aliases:
+
+Argument Aliases
+----------------
+
+So far, the example works well, except for the fact that we need to check the
+quiet condition like this now:
+
+.. code-block:: c++
+
+ ...
+ if (!Quiet && !Quiet2) printInformationalMessage(...);
+ ...
+
+... which is a real pain! Instead of defining two values for the same
+condition, we can use the "`cl::alias`_" class to make the "``-q``" option an
+**alias** for the "``-quiet``" option, instead of providing a value itself:
+
+.. code-block:: c++
+
+ cl::opt<bool> Force ("f", cl::desc("Overwrite output files"));
+ cl::opt<bool> Quiet ("quiet", cl::desc("Don't print informational messages"));
+ cl::alias QuietA("q", cl::desc("Alias for -quiet"), cl::aliasopt(Quiet));
+
+The third line (which is the only one we modified from above) defines a "``-q``"
+alias that updates the "``Quiet``" variable (as specified by the `cl::aliasopt`_
+modifier) whenever it is specified. Because aliases do not hold state, the only
+thing the program has to query is the ``Quiet`` variable now. Another nice
+feature of aliases is that they automatically hide themselves from the ``-help``
+output (although, again, they are still visible in the ``-help-hidden output``).
+
+Now the application code can simply use:
+
+.. code-block:: c++
+
+ ...
+ if (!Quiet) printInformationalMessage(...);
+ ...
+
+... which is much nicer! The "`cl::alias`_" can be used to specify an
+alternative name for any variable type, and has many uses.
+
+.. _unnamed alternatives using the generic parser:
+
+Selecting an alternative from a set of possibilities
+----------------------------------------------------
+
+So far we have seen how the CommandLine library handles builtin types like
+``std::string``, ``bool`` and ``int``, but how does it handle things it doesn't
+know about, like enums or '``int*``'s?
+
+The answer is that it uses a table-driven generic parser (unless you specify
+your own parser, as described in the `Extension Guide`_). This parser maps
+literal strings to whatever type is required, and requires you to tell it what
+this mapping should be.
+
+Let's say that we would like to add four optimization levels to our optimizer,
+using the standard flags "``-g``", "``-O0``", "``-O1``", and "``-O2``". We
+could easily implement this with boolean options like above, but there are
+several problems with this strategy:
+
+#. A user could specify more than one of the options at a time, for example,
+ "``compiler -O3 -O2``". The CommandLine library would not be able to catch
+ this erroneous input for us.
+
+#. We would have to test 4 different variables to see which ones are set.
+
+#. This doesn't map to the numeric levels that we want... so we cannot easily
+ see if some level >= "``-O1``" is enabled.
+
+To cope with these problems, we can use an enum value, and have the CommandLine
+library fill it in with the appropriate level directly, which is used like this:
+
+.. code-block:: c++
+
+ enum OptLevel {
+ g, O1, O2, O3
+ };
+
+ cl::opt<OptLevel> OptimizationLevel(cl::desc("Choose optimization level:"),
+ cl::values(
+ clEnumVal(g , "No optimizations, enable debugging"),
+ clEnumVal(O1, "Enable trivial optimizations"),
+ clEnumVal(O2, "Enable default optimizations"),
+ clEnumVal(O3, "Enable expensive optimizations"),
+ clEnumValEnd));
+
+ ...
+ if (OptimizationLevel >= O2) doPartialRedundancyElimination(...);
+ ...
+
+This declaration defines a variable "``OptimizationLevel``" of the
+"``OptLevel``" enum type. This variable can be assigned any of the values that
+are listed in the declaration (Note that the declaration list must be terminated
+with the "``clEnumValEnd``" argument!). The CommandLine library enforces that
+the user can only specify one of the options, and it ensure that only valid enum
+values can be specified. The "``clEnumVal``" macros ensure that the command
+line arguments matched the enum values. With this option added, our help output
+now is:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ Choose optimization level:
+ -g - No optimizations, enable debugging
+ -O1 - Enable trivial optimizations
+ -O2 - Enable default optimizations
+ -O3 - Enable expensive optimizations
+ -f - Enable binary output on terminals
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+ -quiet - Don't print informational messages
+
+In this case, it is sort of awkward that flag names correspond directly to enum
+names, because we probably don't want a enum definition named "``g``" in our
+program. Because of this, we can alternatively write this example like this:
+
+.. code-block:: c++
+
+ enum OptLevel {
+ Debug, O1, O2, O3
+ };
+
+ cl::opt<OptLevel> OptimizationLevel(cl::desc("Choose optimization level:"),
+ cl::values(
+ clEnumValN(Debug, "g", "No optimizations, enable debugging"),
+ clEnumVal(O1 , "Enable trivial optimizations"),
+ clEnumVal(O2 , "Enable default optimizations"),
+ clEnumVal(O3 , "Enable expensive optimizations"),
+ clEnumValEnd));
+
+ ...
+ if (OptimizationLevel == Debug) outputDebugInfo(...);
+ ...
+
+By using the "``clEnumValN``" macro instead of "``clEnumVal``", we can directly
+specify the name that the flag should get. In general a direct mapping is nice,
+but sometimes you can't or don't want to preserve the mapping, which is when you
+would use it.
+
+Named Alternatives
+------------------
+
+Another useful argument form is a named alternative style. We shall use this
+style in our compiler to specify different debug levels that can be used.
+Instead of each debug level being its own switch, we want to support the
+following options, of which only one can be specified at a time:
+"``--debug-level=none``", "``--debug-level=quick``",
+"``--debug-level=detailed``". To do this, we use the exact same format as our
+optimization level flags, but we also specify an option name. For this case,
+the code looks like this:
+
+.. code-block:: c++
+
+ enum DebugLev {
+ nodebuginfo, quick, detailed
+ };
+
+ // Enable Debug Options to be specified on the command line
+ cl::opt<DebugLev> DebugLevel("debug_level", cl::desc("Set the debugging level:"),
+ cl::values(
+ clEnumValN(nodebuginfo, "none", "disable debug information"),
+ clEnumVal(quick, "enable quick debug information"),
+ clEnumVal(detailed, "enable detailed debug information"),
+ clEnumValEnd));
+
+This definition defines an enumerated command line variable of type "``enum
+DebugLev``", which works exactly the same way as before. The difference here is
+just the interface exposed to the user of your program and the help output by
+the "``-help``" option:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ Choose optimization level:
+ -g - No optimizations, enable debugging
+ -O1 - Enable trivial optimizations
+ -O2 - Enable default optimizations
+ -O3 - Enable expensive optimizations
+ -debug_level - Set the debugging level:
+ =none - disable debug information
+ =quick - enable quick debug information
+ =detailed - enable detailed debug information
+ -f - Enable binary output on terminals
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+ -quiet - Don't print informational messages
+
+Again, the only structural difference between the debug level declaration and
+the optimization level declaration is that the debug level declaration includes
+an option name (``"debug_level"``), which automatically changes how the library
+processes the argument. The CommandLine library supports both forms so that you
+can choose the form most appropriate for your application.
+
+.. _lists:
+
+Parsing a list of options
+-------------------------
+
+Now that we have the standard run-of-the-mill argument types out of the way,
+lets get a little wild and crazy. Lets say that we want our optimizer to accept
+a **list** of optimizations to perform, allowing duplicates. For example, we
+might want to run: "``compiler -dce -constprop -inline -dce -strip``". In this
+case, the order of the arguments and the number of appearances is very
+important. This is what the "``cl::list``" template is for. First, start by
+defining an enum of the optimizations that you would like to perform:
+
+.. code-block:: c++
+
+ enum Opts {
+ // 'inline' is a C++ keyword, so name it 'inlining'
+ dce, constprop, inlining, strip
+ };
+
+Then define your "``cl::list``" variable:
+
+.. code-block:: c++
+
+ cl::list<Opts> OptimizationList(cl::desc("Available Optimizations:"),
+ cl::values(
+ clEnumVal(dce , "Dead Code Elimination"),
+ clEnumVal(constprop , "Constant Propagation"),
+ clEnumValN(inlining, "inline", "Procedure Integration"),
+ clEnumVal(strip , "Strip Symbols"),
+ clEnumValEnd));
+
+This defines a variable that is conceptually of the type
+"``std::vector<enum Opts>``". Thus, you can access it with standard vector
+methods:
+
+.. code-block:: c++
+
+ for (unsigned i = 0; i != OptimizationList.size(); ++i)
+ switch (OptimizationList[i])
+ ...
+
+... to iterate through the list of options specified.
+
+Note that the "``cl::list``" template is completely general and may be used with
+any data types or other arguments that you can use with the "``cl::opt``"
+template. One especially useful way to use a list is to capture all of the
+positional arguments together if there may be more than one specified. In the
+case of a linker, for example, the linker takes several '``.o``' files, and
+needs to capture them into a list. This is naturally specified as:
+
+.. code-block:: c++
+
+ ...
+ cl::list<std::string> InputFilenames(cl::Positional, cl::desc("<Input files>"), cl::OneOrMore);
+ ...
+
+This variable works just like a "``vector<string>``" object. As such, accessing
+the list is simple, just like above. In this example, we used the
+`cl::OneOrMore`_ modifier to inform the CommandLine library that it is an error
+if the user does not specify any ``.o`` files on our command line. Again, this
+just reduces the amount of checking we have to do.
+
+Collecting options as a set of flags
+------------------------------------
+
+Instead of collecting sets of options in a list, it is also possible to gather
+information for enum values in a **bit vector**. The representation used by the
+`cl::bits`_ class is an ``unsigned`` integer. An enum value is represented by a
+0/1 in the enum's ordinal value bit position. 1 indicating that the enum was
+specified, 0 otherwise. As each specified value is parsed, the resulting enum's
+bit is set in the option's bit vector:
+
+.. code-block:: c++
+
+ bits |= 1 << (unsigned)enum;
+
+Options that are specified multiple times are redundant. Any instances after
+the first are discarded.
+
+Reworking the above list example, we could replace `cl::list`_ with `cl::bits`_:
+
+.. code-block:: c++
+
+ cl::bits<Opts> OptimizationBits(cl::desc("Available Optimizations:"),
+ cl::values(
+ clEnumVal(dce , "Dead Code Elimination"),
+ clEnumVal(constprop , "Constant Propagation"),
+ clEnumValN(inlining, "inline", "Procedure Integration"),
+ clEnumVal(strip , "Strip Symbols"),
+ clEnumValEnd));
+
+To test to see if ``constprop`` was specified, we can use the ``cl:bits::isSet``
+function:
+
+.. code-block:: c++
+
+ if (OptimizationBits.isSet(constprop)) {
+ ...
+ }
+
+It's also possible to get the raw bit vector using the ``cl::bits::getBits``
+function:
+
+.. code-block:: c++
+
+ unsigned bits = OptimizationBits.getBits();
+
+Finally, if external storage is used, then the location specified must be of
+**type** ``unsigned``. In all other ways a `cl::bits`_ option is equivalent to a
+`cl::list`_ option.
+
+.. _additional extra text:
+
+Adding freeform text to help output
+-----------------------------------
+
+As our program grows and becomes more mature, we may decide to put summary
+information about what it does into the help output. The help output is styled
+to look similar to a Unix ``man`` page, providing concise information about a
+program. Unix ``man`` pages, however often have a description about what the
+program does. To add this to your CommandLine program, simply pass a third
+argument to the `cl::ParseCommandLineOptions`_ call in main. This additional
+argument is then printed as the overview information for your program, allowing
+you to include any additional information that you want. For example:
+
+.. code-block:: c++
+
+ int main(int argc, char **argv) {
+ cl::ParseCommandLineOptions(argc, argv, " CommandLine compiler example\n\n"
+ " This program blah blah blah...\n");
+ ...
+ }
+
+would yield the help output:
+
+::
+
+ **OVERVIEW: CommandLine compiler example
+
+ This program blah blah blah...**
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ ...
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+
+.. _Reference Guide:
+
+Reference Guide
+===============
+
+Now that you know the basics of how to use the CommandLine library, this section
+will give you the detailed information you need to tune how command line options
+work, as well as information on more "advanced" command line option processing
+capabilities.
+
+.. _positional:
+.. _positional argument:
+.. _Positional Arguments:
+.. _Positional arguments section:
+.. _positional options:
+
+Positional Arguments
+--------------------
+
+Positional arguments are those arguments that are not named, and are not
+specified with a hyphen. Positional arguments should be used when an option is
+specified by its position alone. For example, the standard Unix ``grep`` tool
+takes a regular expression argument, and an optional filename to search through
+(which defaults to standard input if a filename is not specified). Using the
+CommandLine library, this would be specified as:
+
+.. code-block:: c++
+
+ cl::opt<string> Regex (cl::Positional, cl::desc("<regular expression>"), cl::Required);
+ cl::opt<string> Filename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
+
+Given these two option declarations, the ``-help`` output for our grep
+replacement would look like this:
+
+::
+
+ USAGE: spiffygrep [options] <regular expression> <input file>
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+
+... and the resultant program could be used just like the standard ``grep``
+tool.
+
+Positional arguments are sorted by their order of construction. This means that
+command line options will be ordered according to how they are listed in a .cpp
+file, but will not have an ordering defined if the positional arguments are
+defined in multiple .cpp files. The fix for this problem is simply to define
+all of your positional arguments in one .cpp file.
+
+Specifying positional options with hyphens
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Sometimes you may want to specify a value to your positional argument that
+starts with a hyphen (for example, searching for '``-foo``' in a file). At
+first, you will have trouble doing this, because it will try to find an argument
+named '``-foo``', and will fail (and single quotes will not save you). Note
+that the system ``grep`` has the same problem:
+
+::
+
+ $ spiffygrep '-foo' test.txt
+ Unknown command line argument '-foo'. Try: spiffygrep -help'
+
+ $ grep '-foo' test.txt
+ grep: illegal option -- f
+ grep: illegal option -- o
+ grep: illegal option -- o
+ Usage: grep -hblcnsviw pattern file . . .
+
+The solution for this problem is the same for both your tool and the system
+version: use the '``--``' marker. When the user specifies '``--``' on the
+command line, it is telling the program that all options after the '``--``'
+should be treated as positional arguments, not options. Thus, we can use it
+like this:
+
+::
+
+ $ spiffygrep -- -foo test.txt
+ ...output...
+
+Determining absolute position with getPosition()
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Sometimes an option can affect or modify the meaning of another option. For
+example, consider ``gcc``'s ``-x LANG`` option. This tells ``gcc`` to ignore the
+suffix of subsequent positional arguments and force the file to be interpreted
+as if it contained source code in language ``LANG``. In order to handle this
+properly, you need to know the absolute position of each argument, especially
+those in lists, so their interaction(s) can be applied correctly. This is also
+useful for options like ``-llibname`` which is actually a positional argument
+that starts with a dash.
+
+So, generally, the problem is that you have two ``cl::list`` variables that
+interact in some way. To ensure the correct interaction, you can use the
+``cl::list::getPosition(optnum)`` method. This method returns the absolute
+position (as found on the command line) of the ``optnum`` item in the
+``cl::list``.
+
+The idiom for usage is like this:
+
+.. code-block:: c++
+
+ static cl::list<std::string> Files(cl::Positional, cl::OneOrMore);
+ static cl::list<std::string> Libraries("l", cl::ZeroOrMore);
+
+ int main(int argc, char**argv) {
+ // ...
+ std::vector<std::string>::iterator fileIt = Files.begin();
+ std::vector<std::string>::iterator libIt = Libraries.begin();
+ unsigned libPos = 0, filePos = 0;
+ while ( 1 ) {
+ if ( libIt != Libraries.end() )
+ libPos = Libraries.getPosition( libIt - Libraries.begin() );
+ else
+ libPos = 0;
+ if ( fileIt != Files.end() )
+ filePos = Files.getPosition( fileIt - Files.begin() );
+ else
+ filePos = 0;
+
+ if ( filePos != 0 && (libPos == 0 || filePos < libPos) ) {
+ // Source File Is next
+ ++fileIt;
+ }
+ else if ( libPos != 0 && (filePos == 0 || libPos < filePos) ) {
+ // Library is next
+ ++libIt;
+ }
+ else
+ break; // we're done with the list
+ }
+ }
+
+Note that, for compatibility reasons, the ``cl::opt`` also supports an
+``unsigned getPosition()`` option that will provide the absolute position of
+that option. You can apply the same approach as above with a ``cl::opt`` and a
+``cl::list`` option as you can with two lists.
+
+.. _interpreter style options:
+.. _cl::ConsumeAfter:
+.. _this section for more information:
+
+The ``cl::ConsumeAfter`` modifier
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::ConsumeAfter`` `formatting option`_ is used to construct programs that
+use "interpreter style" option processing. With this style of option
+processing, all arguments specified after the last positional argument are
+treated as special interpreter arguments that are not interpreted by the command
+line argument.
+
+As a concrete example, lets say we are developing a replacement for the standard
+Unix Bourne shell (``/bin/sh``). To run ``/bin/sh``, first you specify options
+to the shell itself (like ``-x`` which turns on trace output), then you specify
+the name of the script to run, then you specify arguments to the script. These
+arguments to the script are parsed by the Bourne shell command line option
+processor, but are not interpreted as options to the shell itself. Using the
+CommandLine library, we would specify this as:
+
+.. code-block:: c++
+
+ cl::opt<string> Script(cl::Positional, cl::desc("<input script>"), cl::init("-"));
+ cl::list<string> Argv(cl::ConsumeAfter, cl::desc("<program arguments>..."));
+ cl::opt<bool> Trace("x", cl::desc("Enable trace output"));
+
+which automatically provides the help output:
+
+::
+
+ USAGE: spiffysh [options] <input script> <program arguments>...
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+ -x - Enable trace output
+
+At runtime, if we run our new shell replacement as ```spiffysh -x test.sh -a -x
+-y bar``', the ``Trace`` variable will be set to true, the ``Script`` variable
+will be set to "``test.sh``", and the ``Argv`` list will contain ``["-a", "-x",
+"-y", "bar"]``, because they were specified after the last positional argument
+(which is the script name).
+
+There are several limitations to when ``cl::ConsumeAfter`` options can be
+specified. For example, only one ``cl::ConsumeAfter`` can be specified per
+program, there must be at least one `positional argument`_ specified, there must
+not be any `cl::list`_ positional arguments, and the ``cl::ConsumeAfter`` option
+should be a `cl::list`_ option.
+
+.. _can be changed:
+.. _Internal vs External Storage:
+
+Internal vs External Storage
+----------------------------
+
+By default, all command line options automatically hold the value that they
+parse from the command line. This is very convenient in the common case,
+especially when combined with the ability to define command line options in the
+files that use them. This is called the internal storage model.
+
+Sometimes, however, it is nice to separate the command line option processing
+code from the storage of the value parsed. For example, lets say that we have a
+'``-debug``' option that we would like to use to enable debug information across
+the entire body of our program. In this case, the boolean value controlling the
+debug code should be globally accessible (in a header file, for example) yet the
+command line option processing code should not be exposed to all of these
+clients (requiring lots of .cpp files to ``#include CommandLine.h``).
+
+To do this, set up your .h file with your option, like this for example:
+
+.. code-block:: c++
+
+ // DebugFlag.h - Get access to the '-debug' command line option
+ //
+
+ // DebugFlag - This boolean is set to true if the '-debug' command line option
+ // is specified. This should probably not be referenced directly, instead, use
+ // the DEBUG macro below.
+ //
+ extern bool DebugFlag;
+
+ // DEBUG macro - This macro should be used by code to emit debug information.
+ // In the '-debug' option is specified on the command line, and if this is a
+ // debug build, then the code specified as the option to the macro will be
+ // executed. Otherwise it will not be.
+ #ifdef NDEBUG
+ #define DEBUG(X)
+ #else
+ #define DEBUG(X) do { if (DebugFlag) { X; } } while (0)
+ #endif
+
+This allows clients to blissfully use the ``DEBUG()`` macro, or the
+``DebugFlag`` explicitly if they want to. Now we just need to be able to set
+the ``DebugFlag`` boolean when the option is set. To do this, we pass an
+additional argument to our command line argument processor, and we specify where
+to fill in with the `cl::location`_ attribute:
+
+.. code-block:: c++
+
+ bool DebugFlag; // the actual value
+ static cl::opt<bool, true> // The parser
+ Debug("debug", cl::desc("Enable debug output"), cl::Hidden, cl::location(DebugFlag));
+
+In the above example, we specify "``true``" as the second argument to the
+`cl::opt`_ template, indicating that the template should not maintain a copy of
+the value itself. In addition to this, we specify the `cl::location`_
+attribute, so that ``DebugFlag`` is automatically set.
+
+Option Attributes
+-----------------
+
+This section describes the basic attributes that you can specify on options.
+
+* The option name attribute (which is required for all options, except
+ `positional options`_) specifies what the option name is. This option is
+ specified in simple double quotes:
+
+ .. code-block:: c++
+
+ cl::opt<**bool**> Quiet("quiet");
+
+.. _cl::desc(...):
+
+* The **cl::desc** attribute specifies a description for the option to be
+ shown in the ``-help`` output for the program.
+
+.. _cl::value_desc:
+
+* The **cl::value_desc** attribute specifies a string that can be used to
+ fine tune the ``-help`` output for a command line option. Look `here`_ for an
+ example.
+
+.. _cl::init:
+
+* The **cl::init** attribute specifies an initial value for a `scalar`_
+ option. If this attribute is not specified then the command line option value
+ defaults to the value created by the default constructor for the
+ type.
+
+ .. warning::
+
+ If you specify both **cl::init** and **cl::location** for an option, you
+ must specify **cl::location** first, so that when the command-line parser
+ sees **cl::init**, it knows where to put the initial value. (You will get an
+ error at runtime if you don't put them in the right order.)
+
+.. _cl::location:
+
+* The **cl::location** attribute where to store the value for a parsed command
+ line option if using external storage. See the section on `Internal vs
+ External Storage`_ for more information.
+
+.. _cl::aliasopt:
+
+* The **cl::aliasopt** attribute specifies which option a `cl::alias`_ option is
+ an alias for.
+
+.. _cl::values:
+
+* The **cl::values** attribute specifies the string-to-value mapping to be used
+ by the generic parser. It takes a **clEnumValEnd terminated** list of
+ (option, value, description) triplets that specify the option name, the value
+ mapped to, and the description shown in the ``-help`` for the tool. Because
+ the generic parser is used most frequently with enum values, two macros are
+ often useful:
+
+ #. The **clEnumVal** macro is used as a nice simple way to specify a triplet
+ for an enum. This macro automatically makes the option name be the same as
+ the enum name. The first option to the macro is the enum, the second is
+ the description for the command line option.
+
+ #. The **clEnumValN** macro is used to specify macro options where the option
+ name doesn't equal the enum name. For this macro, the first argument is
+ the enum value, the second is the flag name, and the second is the
+ description.
+
+ You will get a compile time error if you try to use cl::values with a parser
+ that does not support it.
+
+.. _cl::multi_val:
+
+* The **cl::multi_val** attribute specifies that this option takes has multiple
+ values (example: ``-sectalign segname sectname sectvalue``). This attribute
+ takes one unsigned argument - the number of values for the option. This
+ attribute is valid only on ``cl::list`` options (and will fail with compile
+ error if you try to use it with other option types). It is allowed to use all
+ of the usual modifiers on multi-valued options (besides
+ ``cl::ValueDisallowed``, obviously).
+
+Option Modifiers
+----------------
+
+Option modifiers are the flags and expressions that you pass into the
+constructors for `cl::opt`_ and `cl::list`_. These modifiers give you the
+ability to tweak how options are parsed and how ``-help`` output is generated to
+fit your application well.
+
+These options fall into five main categories:
+
+#. Hiding an option from ``-help`` output
+
+#. Controlling the number of occurrences required and allowed
+
+#. Controlling whether or not a value must be specified
+
+#. Controlling other formatting options
+
+#. Miscellaneous option modifiers
+
+It is not possible to specify two options from the same category (you'll get a
+runtime error) to a single option, except for options in the miscellaneous
+category. The CommandLine library specifies defaults for all of these settings
+that are the most useful in practice and the most common, which mean that you
+usually shouldn't have to worry about these.
+
+Hiding an option from ``-help`` output
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::NotHidden``, ``cl::Hidden``, and ``cl::ReallyHidden`` modifiers are
+used to control whether or not an option appears in the ``-help`` and
+``-help-hidden`` output for the compiled program:
+
+.. _cl::NotHidden:
+
+* The **cl::NotHidden** modifier (which is the default for `cl::opt`_ and
+ `cl::list`_ options) indicates the option is to appear in both help
+ listings.
+
+.. _cl::Hidden:
+
+* The **cl::Hidden** modifier (which is the default for `cl::alias`_ options)
+ indicates that the option should not appear in the ``-help`` output, but
+ should appear in the ``-help-hidden`` output.
+
+.. _cl::ReallyHidden:
+
+* The **cl::ReallyHidden** modifier indicates that the option should not appear
+ in any help output.
+
+Controlling the number of occurrences required and allowed
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This group of options is used to control how many time an option is allowed (or
+required) to be specified on the command line of your program. Specifying a
+value for this setting allows the CommandLine library to do error checking for
+you.
+
+The allowed values for this option group are:
+
+.. _cl::Optional:
+
+* The **cl::Optional** modifier (which is the default for the `cl::opt`_ and
+ `cl::alias`_ classes) indicates that your program will allow either zero or
+ one occurrence of the option to be specified.
+
+.. _cl::ZeroOrMore:
+
+* The **cl::ZeroOrMore** modifier (which is the default for the `cl::list`_
+ class) indicates that your program will allow the option to be specified zero
+ or more times.
+
+.. _cl::Required:
+
+* The **cl::Required** modifier indicates that the specified option must be
+ specified exactly one time.
+
+.. _cl::OneOrMore:
+
+* The **cl::OneOrMore** modifier indicates that the option must be specified at
+ least one time.
+
+* The **cl::ConsumeAfter** modifier is described in the `Positional arguments
+ section`_.
+
+If an option is not specified, then the value of the option is equal to the
+value specified by the `cl::init`_ attribute. If the ``cl::init`` attribute is
+not specified, the option value is initialized with the default constructor for
+the data type.
+
+If an option is specified multiple times for an option of the `cl::opt`_ class,
+only the last value will be retained.
+
+Controlling whether or not a value must be specified
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This group of options is used to control whether or not the option allows a
+value to be present. In the case of the CommandLine library, a value is either
+specified with an equal sign (e.g. '``-index-depth=17``') or as a trailing
+string (e.g. '``-o a.out``').
+
+The allowed values for this option group are:
+
+.. _cl::ValueOptional:
+
+* The **cl::ValueOptional** modifier (which is the default for ``bool`` typed
+ options) specifies that it is acceptable to have a value, or not. A boolean
+ argument can be enabled just by appearing on the command line, or it can have
+ an explicit '``-foo=true``'. If an option is specified with this mode, it is
+ illegal for the value to be provided without the equal sign. Therefore
+ '``-foo true``' is illegal. To get this behavior, you must use
+ the `cl::ValueRequired`_ modifier.
+
+.. _cl::ValueRequired:
+
+* The **cl::ValueRequired** modifier (which is the default for all other types
+ except for `unnamed alternatives using the generic parser`_) specifies that a
+ value must be provided. This mode informs the command line library that if an
+ option is not provides with an equal sign, that the next argument provided
+ must be the value. This allows things like '``-o a.out``' to work.
+
+.. _cl::ValueDisallowed:
+
+* The **cl::ValueDisallowed** modifier (which is the default for `unnamed
+ alternatives using the generic parser`_) indicates that it is a runtime error
+ for the user to specify a value. This can be provided to disallow users from
+ providing options to boolean options (like '``-foo=true``').
+
+In general, the default values for this option group work just like you would
+want them to. As mentioned above, you can specify the `cl::ValueDisallowed`_
+modifier to a boolean argument to restrict your command line parser. These
+options are mostly useful when `extending the library`_.
+
+.. _formatting option:
+
+Controlling other formatting options
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The formatting option group is used to specify that the command line option has
+special abilities and is otherwise different from other command line arguments.
+As usual, you can only specify one of these arguments at most.
+
+.. _cl::NormalFormatting:
+
+* The **cl::NormalFormatting** modifier (which is the default all options)
+ specifies that this option is "normal".
+
+.. _cl::Positional:
+
+* The **cl::Positional** modifier specifies that this is a positional argument
+ that does not have a command line option associated with it. See the
+ `Positional Arguments`_ section for more information.
+
+* The **cl::ConsumeAfter** modifier specifies that this option is used to
+ capture "interpreter style" arguments. See `this section for more
+ information`_.
+
+.. _prefix:
+.. _cl::Prefix:
+
+* The **cl::Prefix** modifier specifies that this option prefixes its value.
+ With 'Prefix' options, the equal sign does not separate the value from the
+ option name specified. Instead, the value is everything after the prefix,
+ including any equal sign if present. This is useful for processing odd
+ arguments like ``-lmalloc`` and ``-L/usr/lib`` in a linker tool or
+ ``-DNAME=value`` in a compiler tool. Here, the '``l``', '``D``' and '``L``'
+ options are normal string (or list) options, that have the **cl::Prefix**
+ modifier added to allow the CommandLine library to recognize them. Note that
+ **cl::Prefix** options must not have the **cl::ValueDisallowed** modifier
+ specified.
+
+.. _grouping:
+.. _cl::Grouping:
+
+* The **cl::Grouping** modifier is used to implement Unix-style tools (like
+ ``ls``) that have lots of single letter arguments, but only require a single
+ dash. For example, the '``ls -labF``' command actually enables four different
+ options, all of which are single letters. Note that **cl::Grouping** options
+ cannot have values.
+
+The CommandLine library does not restrict how you use the **cl::Prefix** or
+**cl::Grouping** modifiers, but it is possible to specify ambiguous argument
+settings. Thus, it is possible to have multiple letter options that are prefix
+or grouping options, and they will still work as designed.
+
+To do this, the CommandLine library uses a greedy algorithm to parse the input
+option into (potentially multiple) prefix and grouping options. The strategy
+basically looks like this:
+
+::
+
+ parse(string OrigInput) {
+
+ 1. string input = OrigInput;
+ 2. if (isOption(input)) return getOption(input).parse(); // Normal option
+ 3. while (!isOption(input) && !input.empty()) input.pop_back(); // Remove the last letter
+ 4. if (input.empty()) return error(); // No matching option
+ 5. if (getOption(input).isPrefix())
+ return getOption(input).parse(input);
+ 6. while (!input.empty()) { // Must be grouping options
+ getOption(input).parse();
+ OrigInput.erase(OrigInput.begin(), OrigInput.begin()+input.length());
+ input = OrigInput;
+ while (!isOption(input) && !input.empty()) input.pop_back();
+ }
+ 7. if (!OrigInput.empty()) error();
+
+ }
+
+Miscellaneous option modifiers
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The miscellaneous option modifiers are the only flags where you can specify more
+than one flag from the set: they are not mutually exclusive. These flags
+specify boolean properties that modify the option.
+
+.. _cl::CommaSeparated:
+
+* The **cl::CommaSeparated** modifier indicates that any commas specified for an
+ option's value should be used to split the value up into multiple values for
+ the option. For example, these two options are equivalent when
+ ``cl::CommaSeparated`` is specified: "``-foo=a -foo=b -foo=c``" and
+ "``-foo=a,b,c``". This option only makes sense to be used in a case where the
+ option is allowed to accept one or more values (i.e. it is a `cl::list`_
+ option).
+
+.. _cl::PositionalEatsArgs:
+
+* The **cl::PositionalEatsArgs** modifier (which only applies to positional
+ arguments, and only makes sense for lists) indicates that positional argument
+ should consume any strings after it (including strings that start with a "-")
+ up until another recognized positional argument. For example, if you have two
+ "eating" positional arguments, "``pos1``" and "``pos2``", the string "``-pos1
+ -foo -bar baz -pos2 -bork``" would cause the "``-foo -bar -baz``" strings to
+ be applied to the "``-pos1``" option and the "``-bork``" string to be applied
+ to the "``-pos2``" option.
+
+.. _cl::Sink:
+
+* The **cl::Sink** modifier is used to handle unknown options. If there is at
+ least one option with ``cl::Sink`` modifier specified, the parser passes
+ unrecognized option strings to it as values instead of signaling an error. As
+ with ``cl::CommaSeparated``, this modifier only makes sense with a `cl::list`_
+ option.
+
+So far, these are the only three miscellaneous option modifiers.
+
+.. _response files:
+
+Response files
+^^^^^^^^^^^^^^
+
+Some systems, such as certain variants of Microsoft Windows and some older
+Unices have a relatively low limit on command-line length. It is therefore
+customary to use the so-called 'response files' to circumvent this
+restriction. These files are mentioned on the command-line (using the "@file")
+syntax. The program reads these files and inserts the contents into argv,
+thereby working around the command-line length limits. Response files are
+enabled by an optional fourth argument to `cl::ParseEnvironmentOptions`_ and
+`cl::ParseCommandLineOptions`_.
+
+Top-Level Classes and Functions
+-------------------------------
+
+Despite all of the built-in flexibility, the CommandLine option library really
+only consists of one function `cl::ParseCommandLineOptions`_) and three main
+classes: `cl::opt`_, `cl::list`_, and `cl::alias`_. This section describes
+these three classes in detail.
+
+.. _cl::ParseCommandLineOptions:
+
+The ``cl::ParseCommandLineOptions`` function
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::ParseCommandLineOptions`` function is designed to be called directly
+from ``main``, and is used to fill in the values of all of the command line
+option variables once ``argc`` and ``argv`` are available.
+
+The ``cl::ParseCommandLineOptions`` function requires two parameters (``argc``
+and ``argv``), but may also take an optional third parameter which holds
+`additional extra text`_ to emit when the ``-help`` option is invoked, and a
+fourth boolean parameter that enables `response files`_.
+
+.. _cl::ParseEnvironmentOptions:
+
+The ``cl::ParseEnvironmentOptions`` function
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::ParseEnvironmentOptions`` function has mostly the same effects as
+`cl::ParseCommandLineOptions`_, except that it is designed to take values for
+options from an environment variable, for those cases in which reading the
+command line is not convenient or desired. It fills in the values of all the
+command line option variables just like `cl::ParseCommandLineOptions`_ does.
+
+It takes four parameters: the name of the program (since ``argv`` may not be
+available, it can't just look in ``argv[0]``), the name of the environment
+variable to examine, the optional `additional extra text`_ to emit when the
+``-help`` option is invoked, and the boolean switch that controls whether
+`response files`_ should be read.
+
+``cl::ParseEnvironmentOptions`` will break the environment variable's value up
+into words and then process them using `cl::ParseCommandLineOptions`_.
+**Note:** Currently ``cl::ParseEnvironmentOptions`` does not support quoting, so
+an environment variable containing ``-option "foo bar"`` will be parsed as three
+words, ``-option``, ``"foo``, and ``bar"``, which is different from what you
+would get from the shell with the same input.
+
+The ``cl::SetVersionPrinter`` function
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::SetVersionPrinter`` function is designed to be called directly from
+``main`` and *before* ``cl::ParseCommandLineOptions``. Its use is optional. It
+simply arranges for a function to be called in response to the ``--version``
+option instead of having the ``CommandLine`` library print out the usual version
+string for LLVM. This is useful for programs that are not part of LLVM but wish
+to use the ``CommandLine`` facilities. Such programs should just define a small
+function that takes no arguments and returns ``void`` and that prints out
+whatever version information is appropriate for the program. Pass the address of
+that function to ``cl::SetVersionPrinter`` to arrange for it to be called when
+the ``--version`` option is given by the user.
+
+.. _cl::opt:
+.. _scalar:
+
+The ``cl::opt`` class
+^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::opt`` class is the class used to represent scalar command line
+options, and is the one used most of the time. It is a templated class which
+can take up to three arguments (all except for the first have default values
+though):
+
+.. code-block:: c++
+
+ namespace cl {
+ template <class DataType, bool ExternalStorage = false,
+ class ParserClass = parser<DataType> >
+ class opt;
+ }
+
+The first template argument specifies what underlying data type the command line
+argument is, and is used to select a default parser implementation. The second
+template argument is used to specify whether the option should contain the
+storage for the option (the default) or whether external storage should be used
+to contain the value parsed for the option (see `Internal vs External Storage`_
+for more information).
+
+The third template argument specifies which parser to use. The default value
+selects an instantiation of the ``parser`` class based on the underlying data
+type of the option. In general, this default works well for most applications,
+so this option is only used when using a `custom parser`_.
+
+.. _lists of arguments:
+.. _cl::list:
+
+The ``cl::list`` class
+^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::list`` class is the class used to represent a list of command line
+options. It too is a templated class which can take up to three arguments:
+
+.. code-block:: c++
+
+ namespace cl {
+ template <class DataType, class Storage = bool,
+ class ParserClass = parser<DataType> >
+ class list;
+ }
+
+This class works the exact same as the `cl::opt`_ class, except that the second
+argument is the **type** of the external storage, not a boolean value. For this
+class, the marker type '``bool``' is used to indicate that internal storage
+should be used.
+
+.. _cl::bits:
+
+The ``cl::bits`` class
+^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::bits`` class is the class used to represent a list of command line
+options in the form of a bit vector. It is also a templated class which can
+take up to three arguments:
+
+.. code-block:: c++
+
+ namespace cl {
+ template <class DataType, class Storage = bool,
+ class ParserClass = parser<DataType> >
+ class bits;
+ }
+
+This class works the exact same as the `cl::list`_ class, except that the second
+argument must be of **type** ``unsigned`` if external storage is used.
+
+.. _cl::alias:
+
+The ``cl::alias`` class
+^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::alias`` class is a nontemplated class that is used to form aliases for
+other arguments.
+
+.. code-block:: c++
+
+ namespace cl {
+ class alias;
+ }
+
+The `cl::aliasopt`_ attribute should be used to specify which option this is an
+alias for. Alias arguments default to being `cl::Hidden`_, and use the aliased
+options parser to do the conversion from string to data.
+
+.. _cl::extrahelp:
+
+The ``cl::extrahelp`` class
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::extrahelp`` class is a nontemplated class that allows extra help text
+to be printed out for the ``-help`` option.
+
+.. code-block:: c++
+
+ namespace cl {
+ struct extrahelp;
+ }
+
+To use the extrahelp, simply construct one with a ``const char*`` parameter to
+the constructor. The text passed to the constructor will be printed at the
+bottom of the help message, verbatim. Note that multiple ``cl::extrahelp``
+**can** be used, but this practice is discouraged. If your tool needs to print
+additional help information, put all that help into a single ``cl::extrahelp``
+instance.
+
+For example:
+
+.. code-block:: c++
+
+ cl::extrahelp("\nADDITIONAL HELP:\n\n This is the extra help\n");
+
+.. _different parser:
+.. _discussed previously:
+
+Builtin parsers
+---------------
+
+Parsers control how the string value taken from the command line is translated
+into a typed value, suitable for use in a C++ program. By default, the
+CommandLine library uses an instance of ``parser<type>`` if the command line
+option specifies that it uses values of type '``type``'. Because of this,
+custom option processing is specified with specializations of the '``parser``'
+class.
+
+The CommandLine library provides the following builtin parser specializations,
+which are sufficient for most applications. It can, however, also be extended to
+work with new data types and new ways of interpreting the same data. See the
+`Writing a Custom Parser`_ for more details on this type of library extension.
+
+.. _enums:
+.. _cl::parser:
+
+* The generic ``parser<t>`` parser can be used to map strings values to any data
+ type, through the use of the `cl::values`_ property, which specifies the
+ mapping information. The most common use of this parser is for parsing enum
+ values, which allows you to use the CommandLine library for all of the error
+ checking to make sure that only valid enum values are specified (as opposed to
+ accepting arbitrary strings). Despite this, however, the generic parser class
+ can be used for any data type.
+
+.. _boolean flags:
+.. _bool parser:
+
+* The **parser<bool> specialization** is used to convert boolean strings to a
+ boolean value. Currently accepted strings are "``true``", "``TRUE``",
+ "``True``", "``1``", "``false``", "``FALSE``", "``False``", and "``0``".
+
+* The **parser<boolOrDefault> specialization** is used for cases where the value
+ is boolean, but we also need to know whether the option was specified at all.
+ boolOrDefault is an enum with 3 values, BOU_UNSET, BOU_TRUE and BOU_FALSE.
+ This parser accepts the same strings as **``parser<bool>``**.
+
+.. _strings:
+
+* The **parser<string> specialization** simply stores the parsed string into the
+ string value specified. No conversion or modification of the data is
+ performed.
+
+.. _integers:
+.. _int:
+
+* The **parser<int> specialization** uses the C ``strtol`` function to parse the
+ string input. As such, it will accept a decimal number (with an optional '+'
+ or '-' prefix) which must start with a non-zero digit. It accepts octal
+ numbers, which are identified with a '``0``' prefix digit, and hexadecimal
+ numbers with a prefix of '``0x``' or '``0X``'.
+
+.. _doubles:
+.. _float:
+.. _double:
+
+* The **parser<double>** and **parser<float> specializations** use the standard
+ C ``strtod`` function to convert floating point strings into floating point
+ values. As such, a broad range of string formats is supported, including
+ exponential notation (ex: ``1.7e15``) and properly supports locales.
+
+.. _Extension Guide:
+.. _extending the library:
+
+Extension Guide
+===============
+
+Although the CommandLine library has a lot of functionality built into it
+already (as discussed previously), one of its true strengths lie in its
+extensibility. This section discusses how the CommandLine library works under
+the covers and illustrates how to do some simple, common, extensions.
+
+.. _Custom parsers:
+.. _custom parser:
+.. _Writing a Custom Parser:
+
+Writing a custom parser
+-----------------------
+
+One of the simplest and most common extensions is the use of a custom parser.
+As `discussed previously`_, parsers are the portion of the CommandLine library
+that turns string input from the user into a particular parsed data type,
+validating the input in the process.
+
+There are two ways to use a new parser:
+
+#. Specialize the `cl::parser`_ template for your custom data type.
+
+ This approach has the advantage that users of your custom data type will
+ automatically use your custom parser whenever they define an option with a
+ value type of your data type. The disadvantage of this approach is that it
+ doesn't work if your fundamental data type is something that is already
+ supported.
+
+#. Write an independent class, using it explicitly from options that need it.
+
+ This approach works well in situations where you would line to parse an
+ option using special syntax for a not-very-special data-type. The drawback
+ of this approach is that users of your parser have to be aware that they are
+ using your parser instead of the builtin ones.
+
+To guide the discussion, we will discuss a custom parser that accepts file
+sizes, specified with an optional unit after the numeric size. For example, we
+would like to parse "102kb", "41M", "1G" into the appropriate integer value. In
+this case, the underlying data type we want to parse into is '``unsigned``'. We
+choose approach #2 above because we don't want to make this the default for all
+``unsigned`` options.
+
+To start out, we declare our new ``FileSizeParser`` class:
+
+.. code-block:: c++
+
+ struct FileSizeParser : public cl::basic_parser<unsigned> {
+ // parse - Return true on error.
+ bool parse(cl::Option &O, const char *ArgName, const std::string &ArgValue,
+ unsigned &Val);
+ };
+
+Our new class inherits from the ``cl::basic_parser`` template class to fill in
+the default, boiler plate code for us. We give it the data type that we parse
+into, the last argument to the ``parse`` method, so that clients of our custom
+parser know what object type to pass in to the parse method. (Here we declare
+that we parse into '``unsigned``' variables.)
+
+For most purposes, the only method that must be implemented in a custom parser
+is the ``parse`` method. The ``parse`` method is called whenever the option is
+invoked, passing in the option itself, the option name, the string to parse, and
+a reference to a return value. If the string to parse is not well-formed, the
+parser should output an error message and return true. Otherwise it should
+return false and set '``Val``' to the parsed value. In our example, we
+implement ``parse`` as:
+
+.. code-block:: c++
+
+ bool FileSizeParser::parse(cl::Option &O, const char *ArgName,
+ const std::string &Arg, unsigned &Val) {
+ const char *ArgStart = Arg.c_str();
+ char *End;
+
+ // Parse integer part, leaving 'End' pointing to the first non-integer char
+ Val = (unsigned)strtol(ArgStart, &End, 0);
+
+ while (1) {
+ switch (*End++) {
+ case 0: return false; // No error
+ case 'i': // Ignore the 'i' in KiB if people use that
+ case 'b': case 'B': // Ignore B suffix
+ break;
+
+ case 'g': case 'G': Val *= 1024*1024*1024; break;
+ case 'm': case 'M': Val *= 1024*1024; break;
+ case 'k': case 'K': Val *= 1024; break;
+
+ default:
+ // Print an error message if unrecognized character!
+ return O.error("'" + Arg + "' value invalid for file size argument!");
+ }
+ }
+ }
+
+This function implements a very simple parser for the kinds of strings we are
+interested in. Although it has some holes (it allows "``123KKK``" for example),
+it is good enough for this example. Note that we use the option itself to print
+out the error message (the ``error`` method always returns true) in order to get
+a nice error message (shown below). Now that we have our parser class, we can
+use it like this:
+
+.. code-block:: c++
+
+ static cl::opt<unsigned, false, FileSizeParser>
+ MFS("max-file-size", cl::desc("Maximum file size to accept"),
+ cl::value_desc("size"));
+
+Which adds this to the output of our program:
+
+::
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+ ...
+ -max-file-size=<size> - Maximum file size to accept
+
+And we can test that our parse works correctly now (the test program just prints
+out the max-file-size argument value):
+
+::
+
+ $ ./test
+ MFS: 0
+ $ ./test -max-file-size=123MB
+ MFS: 128974848
+ $ ./test -max-file-size=3G
+ MFS: 3221225472
+ $ ./test -max-file-size=dog
+ -max-file-size option: 'dog' value invalid for file size argument!
+
+It looks like it works. The error message that we get is nice and helpful, and
+we seem to accept reasonable file sizes. This wraps up the "custom parser"
+tutorial.
+
+Exploiting external storage
+---------------------------
+
+Several of the LLVM libraries define static ``cl::opt`` instances that will
+automatically be included in any program that links with that library. This is
+a feature. However, sometimes it is necessary to know the value of the command
+line option outside of the library. In these cases the library does or should
+provide an external storage location that is accessible to users of the
+library. Examples of this include the ``llvm::DebugFlag`` exported by the
+``lib/Support/Debug.cpp`` file and the ``llvm::TimePassesIsEnabled`` flag
+exported by the ``lib/VMCore/PassManager.cpp`` file.
+
+.. todo::
+
+ TODO: complete this section
+
+.. _dynamically loaded options:
+
+Dynamically adding command line options
+
+.. todo::
+
+ TODO: fill in this section
projects / oota-llvm.git / commitdiff