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Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	1	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	2	<html><head><title>CommandLine 2.0 Library Manual</title></head>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	3	<body bgcolor=white>
				4
				5	<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	6	<tr><td>  <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>CommandLine 2.0 Library Manual</b></font></td>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	7	</tr></table>
				8
				9	<ol>
				10	<li><a href="#introduction">Introduction</a>
				11	<li><a href="#quickstart">Quick Start Guide</a>
				12	<ol>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	13	<li><a href="#bool">Boolean Arguments</a>
				14	<li><a href="#alias">Argument Aliases</a>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	15	<li><a href="#onealternative">Selecting an alternative from a
				16	set of possibilities</a>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	17	<li><a href="#namedalternatives">Named alternatives</a>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	18	<li><a href="#list">Parsing a list of options</a>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	19	<li><a href="#description">Adding freeform text to help output</a>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	20	</ol>
				21	<li><a href="#referenceguide">Reference Guide</a>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	22	<ol>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	23	<li><a href="#positional">Positional Arguments</a>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	24	<ul>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	25	<li><a href="#--">Specifying positional options with hyphens</a>
				26	<li><a href="#cl::ConsumeAfter">The <tt>cl::ConsumeAfter</tt>
				27	modifier</a>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	28	</ul>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	29	<li><a href="#storage">Internal vs External Storage</a>
				30	<li><a href="#attributes">Option Attributes</a>
				31	<li><a href="#modifiers">Option Modifiers</a>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	32	<ul>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	33	<li><a href="#hiding">Hiding an option from <tt>--help</tt> output</a>
				34	<li><a href="#numoccurances">Controlling the number of occurances
				35	required and allowed</a>
				36	<li><a href="#valrequired">Controlling whether or not a value must be
				37	specified</a>
				38	<li><a href="#formatting">Controlling other formatting options</a>
Chris Lattner	32a3284	2003-05-22 20:36:06 +0000	[diff] [blame]	39	<li><a href="#misc">Miscellaneous option modifiers</a>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	40	</ul>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	41	<li><a href="#toplevel">Top-Level Classes and Functions</a>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	42	<ul>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	43	<li><a href="#cl::ParseCommandLineOptions">The
				44	<tt>cl::ParseCommandLineOptions</tt> function</a>
Brian Gaeke	e584285	2003-08-19 23:11:43 +0000	[diff] [blame^]	45	<li><a href="#cl::ParseEnvironmentOptions">The
				46	<tt>cl::ParseEnvironmentOptions</tt> function</a>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	47	<li><a href="#cl::opt">The <tt>cl::opt</tt> class</a>
				48	<li><a href="#cl::list">The <tt>cl::list</tt> class</a>
				49	<li><a href="#cl::alias">The <tt>cl::alias</tt> class</a>
				50	</ul>
				51	<li><a href="#builtinparsers">Builtin parsers</a>
				52	<ul>
				53	<li><a href="#genericparser">The Generic <tt>parser<t></tt>
				54	parser</a>
				55	<li><a href="#boolparser">The <tt>parser<bool></tt>
				56	specialization</a>
				57	<li><a href="#stringparser">The <tt>parser<string></tt>
				58	specialization</a>
				59	<li><a href="#intparser">The <tt>parser<int></tt>
				60	specialization</a>
				61	<li><a href="#doubleparser">The <tt>parser<double></tt> and
				62	<tt>parser<float></tt> specializations</a>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	63	</ul>
				64	</ol>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	65	<li><a href="#extensionguide">Extension Guide</a>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	66	<ol>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	67	<li><a href="#customparser">Writing a custom parser</a>
				68	<li><a href="#explotingexternal">Exploiting external storage</a>
				69	<li><a href="#dynamicopts">Dynamically adding command line options</a>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	70	</ol>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	71
				72	<p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	73	</ol><p>
				74
				75
				76	<!-- *********************************************************************** -->
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	77	<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	78	<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				79	<a name="introduction">Introduction
				80	</b></font></td></tr></table><ul>
				81	<!-- *********************************************************************** -->
				82
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	83	This document describes the CommandLine argument processing library. It will
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	84	show you how to use it, and what it can do. The CommandLine library uses a
				85	declarative approach to specifying the command line options that your program
				86	takes. By default, these options declarations implicitly hold the value parsed
				87	for the option declared (of course this <a href="#storage">can be
				88	changed</a>).<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	89
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	90	Although there are a <b>lot</b> of command line argument parsing libraries out
				91	there in many different languages, none of them fit well with what I needed. By
				92	looking at the features and problems of other libraries, I designed the
				93	CommandLine library to have the following features:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	94
				95	<ol>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	96	<li>Speed: The CommandLine library is very quick and uses little resources. The
				97	parsing time of the library is directly proportional to the number of arguments
				98	parsed, not the the number of options recognized. Additionally, command line
Chris Lattner	edf351f	2003-06-21 21:45:56 +0000	[diff] [blame]	99	argument values are captured transparently into user defined global variables,
				100	which can be accessed like any other variable (and with the same
				101	performance).<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	102
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	103	<li>Type Safe: As a user of CommandLine, you don't have to worry about
				104	remembering the type of arguments that you want (is it an int? a string? a
				105	bool? an enum?) and keep casting it around. Not only does this help prevent
				106	error prone constructs, it also leads to dramatically cleaner source code.<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	107
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	108	<li>No subclasses required: To use CommandLine, you instantiate variables that
				109	correspond to the arguments that you would like to capture, you don't subclass a
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	110	parser. This means that you don't have to write <b>any</b> boilerplate code.<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	111
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	112	<li>Globally accessible: Libraries can specify command line arguments that are
				113	automatically enabled in any tool that links to the library. This is possible
				114	because the application doesn't have to keep a "list" of arguments to pass to
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	115	the parser. This also makes supporting <a href="#dynamicopts">dynamically
				116	loaded options</a> trivial.<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	117
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	118	<li>Cleaner: CommandLine supports enum and other types directly, meaning that
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	119	there is less error and more security built into the library. You don't have to
				120	worry about whether your integral command line argument accidentally got
				121	assigned a value that is not valid for your enum type.<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	122
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	123	<li>Powerful: The CommandLine library supports many different types of
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	124	arguments, from simple <a href="#boolparser">boolean flags</a> to <a
				125	href="#cl::opt">scalars arguments</a> (<a href="#stringparser">strings</a>, <a
				126	href="#intparser">integers</a>, <a href="#genericparser">enums</a>, <a
				127	href="#doubleparser">doubles</a>), to <a href="#cl::list">lists of
				128	arguments</a>. This is possible because CommandLine is...<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	129
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	130	<li>Extensible: It is very simple to add a new argument type to CommandLine.
				131	Simply specify the parser that you want to use with the command line option when
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	132	you declare it. <a href="#customparser">Custom parsers</a> are no problem.<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	133
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	134	<li>Labor Saving: The CommandLine library cuts down on the amount of grunt work
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	135	that you, the user, have to do. For example, it automatically provides a
				136	<tt>--help</tt> option that shows the available command line options for your
				137	tool. Additionally, it does most of the basic correctness checking for you.<p>
				138
				139	<li>Capable: The CommandLine library can handle lots of different forms of
				140	options often found in real programs. For example, <a
				141	href="#positional">positional</a> arguments, <tt>ls</tt> style <a
				142	href="#cl::Grouping">grouping</a> options (to allow processing '<tt>ls
				143	-lad</tt>' naturally), <tt>ld</tt> style <a href="#cl::Prefix">prefix</a>
				144	options (to parse '<tt>-lmalloc -L/usr/lib</tt>'), and <a
				145	href="#cl::ConsumeAfter">interpreter style options</a>.<p>
				146
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	147	</ol>
				148
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	149	This document will hopefully let you jump in and start using CommandLine in your
				150	utility quickly and painlessly. Additionally it should be a simple reference
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	151	manual to figure out how stuff works. If it is failing in some area (or you
				152	want an extension to the library), nag the author, <a
				153	href="mailto:sabre@nondot.org">Chris Lattner</a>.<p>
				154
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	155
				156
				157	<!-- *********************************************************************** -->
				158	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				159	<a name="quickstart">Quick Start Guide
				160	</b></font></td></tr></table><ul>
				161	<!-- *********************************************************************** -->
				162
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	163	This section of the manual runs through a simple CommandLine'ification of a
				164	basic compiler tool. This is intended to show you how to jump into using the
				165	CommandLine library in your own program, and show you some of the cool things it
				166	can do.<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	167
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	168	To start out, you need to include the CommandLine header file into your
				169	program:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	170
				171	<pre>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	172	#include "Support/CommandLine.h"
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	173	</pre><p>
				174
				175	Additionally, you need to add this as the first line of your main program:<p>
				176
				177	<pre>
				178	int main(int argc, char **argv) {
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	179	<a href="#cl::ParseCommandLineOptions">cl::ParseCommandLineOptions</a>(argc, argv);
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	180	...
				181	}
				182	</pre><p>
				183
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	184	... which actually parses the arguments and fills in the variable
				185	declarations.<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	186
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	187	Now that you are ready to support command line arguments, we need to tell the
				188	system which ones we want, and what type of argument they are. The CommandLine
Chris Lattner	edf351f	2003-06-21 21:45:56 +0000	[diff] [blame]	189	library uses a declarative syntax to model command line arguments with the
				190	global variable declarations that capture the parsed values. This means that
				191	for every command line option that you would like to support, there should be a
				192	global variable declaration to capture the result. For example, in a compiler,
				193	we would like to support the unix standard '<tt>-o <filename></tt>' option
				194	to specify where to put the output. With the CommandLine library, this is
				195	represented like this:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	196
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	197	<pre><a name="value_desc_example">
				198	<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>"));
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	199	</pre><p>
				200
Chris Lattner	edf351f	2003-06-21 21:45:56 +0000	[diff] [blame]	201	This declares a global variable "<tt>OutputFilename</tt>" that is used to
				202	capture the result of the "<tt>o</tt>" argument (first parameter). We specify
				203	that this is a simple scalar option by using the "<tt><a
				204	href="#cl::opt">cl::opt</a></tt>" template (as opposed to the <a
				205	href="#list">"<tt>cl::list</tt> template</a>), and tell the CommandLine library
				206	that the data type that we are parsing is a string.<p>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	207
				208	The second and third parameters (which are optional) are used to specify what to
				209	output for the "<tt>--help</tt>" option. In this case, we get a line that looks
				210	like this:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	211
				212	<pre>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	213	USAGE: compiler [options]
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	214
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	215	OPTIONS:
				216	-help - display available options (--help-hidden for more)
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	217	<b>-o <filename> - Specify output filename</b>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	218	</pre>
				219
				220	Because we specified that the command line option should parse using the
				221	<tt>string</tt> data type, the variable declared is automatically usable as a
				222	real string in all contexts that a normal C++ string object may be used. For
				223	example:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	224
				225	<pre>
				226	...
				227	ofstream Output(OutputFilename.c_str());
				228	if (Out.good()) ...
				229	...
				230	</pre><p>
				231
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	232	There are many different options that you can use to customize the command line
				233	option handling library, but the above example shows the general interface to
				234	these options. The options can be specified in any order, and are specified
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	235	with helper functions like <a href="#cl::desc"><tt>cl::desc(...)</tt></a>, so
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	236	there are no positional dependencies to remember. The available options are
				237	discussed in detail in the <a href="#referenceguide">Reference Guide</a>.<p>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	238
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	239
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	240	Continuing the example, we would like to have our compiler take an input
				241	filename as well as an output filename, but we do not want the input filename to
				242	be specified with a hyphen (ie, not <tt>-filename.c</tt>). To support this
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	243	style of argument, the CommandLine library allows for <a
				244	href="#positional">positional</a> arguments to be specified for the program.
				245	These positional arguments are filled with command line parameters that are not
				246	in option form. We use this feature like this:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	247
				248	<pre>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	249	<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>"));
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	250	</pre>
				251
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	252	This declaration indicates that the first positional argument should be treated
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	253	as the input filename. Here we use the <tt><a
				254	href="#cl::init">cl::init</a></tt> option to specify an initial value for the
				255	command line option, which is used if the option is not specified (if you do not
				256	specify a <tt><a href="#cl::init">cl::init</a></tt> modifier for an option, then
				257	the default constructor for the data type is used to initialize the value).
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	258	Command line options default to being optional, so if we would like to require
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	259	that the user always specify an input filename, we would add the <tt><a
				260	href="#cl::Required">cl::Required</a></tt> flag, and we could eliminate the
				261	<tt><a href="#cl::init">cl::init</a></tt> modifier, like this:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	262
				263	<pre>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	264	<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>);
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	265	</pre>
				266
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	267	Again, the CommandLine library does not require the options to be specified in
				268	any particular order, so the above declaration is equivalent to:<p>
				269
				270	<pre>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	271	<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>"));
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	272	</pre>
				273
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	274	By simply adding the <tt><a href="#cl::Required">cl::Required</a></tt> flag, the
				275	CommandLine library will automatically issue an error if the argument is not
				276	specified, which shifts all of the command line option verification code out of
				277	your application into the library. This is just one example of how using flags
				278	can alter the default behaviour of the library, on a per-option basis. By
				279	adding one of the declarations above, the <tt>--help</tt> option synopsis is now
				280	extended to:<p>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	281
				282	<pre>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	283	USAGE: compiler [options] <b><input file></b>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	284
				285	OPTIONS:
				286	-help - display available options (--help-hidden for more)
				287	-o <filename> - Specify output filename
				288	</pre>
				289
				290	... indicating that an input filename is expected.<p>
				291
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	292
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	293
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	294	<!-- ======================================================================= -->
				295	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	296	<a name="bool">Boolean Arguments
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	297	</b></font></td></tr></table><ul>
				298
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	299	In addition to input and output filenames, we would like the compiler example to
				300	support three boolean flags: "<tt>-f</tt>" to force overwriting of the output
				301	file, "<tt>--quiet</tt>" to enable quiet mode, and "<tt>-q</tt>" for backwards
				302	compatibility with some of our users. We can support these by declaring options
				303	of boolean type like this:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	304
				305	<pre>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	306	<a href="#cl::opt">cl::opt</a><bool> Force ("<i>f</i>", <a href="#cl::desc">cl::desc</a>("<i>Overwrite output files</i>"));
				307	<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>"));
				308	<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>);
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	309	</pre><p>
				310
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	311	This does what you would expect: it declares three boolean variables
				312	("<tt>Force</tt>", "<tt>Quiet</tt>", and "<tt>Quiet2</tt>") to recognize these
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	313	options. Note that the "<tt>-q</tt>" option is specified with the "<a
				314	href="#cl::Hidden"><tt>cl::Hidden</tt></a>" flag. This modifier prevents it
				315	from being shown by the standard "<tt>--help</tt>" output (note that it is still
				316	shown in the "<tt>--help-hidden</tt>" output).<p>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	317
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	318	The CommandLine library uses a <a href="#builtinparsers">different parser</a>
				319	for different data types. For example, in the string case, the argument passed
				320	to the option is copied literally into the content of the string variable... we
				321	obviously cannot do that in the boolean case, however, so we must use a smarter
				322	parser. In the case of the boolean parser, it allows no options (in which case
				323	it assigns the value of true to the variable), or it allows the values
				324	"<tt>true</tt>" or "<tt>false</tt>" to be specified, allowing any of the
				325	following inputs:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	326
				327	<pre>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	328	compiler -f # No value, 'Force' == true
				329	compiler -f=true # Value specified, 'Force' == true
				330	compiler -f=TRUE # Value specified, 'Force' == true
				331	compiler -f=FALSE # Value specified, 'Force' == false
				332	</pre>
				333
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	334	... you get the idea. The <a href="#boolparser">bool parser</a> just turns the
				335	string values into boolean values, and rejects things like '<tt>compiler
				336	-f=foo</tt>'. Similarly, the <a href="#doubleparser">float</a>, <a
				337	href="#doubleparser">double</a>, and <a href="#intparser">int</a> parsers work
				338	like you would expect, using the '<tt>strtol</tt>' and '<tt>strtod</tt>' C
				339	library calls to parse the string value into the specified data type.<p>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	340
				341	With the declarations above, "<tt>compiler --help</tt>" emits this:<p>
				342
				343	<pre>
				344	USAGE: compiler [options] <input file>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	345
				346	OPTIONS:
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	347	<b>-f - Overwrite output files</b>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	348	-o - Override output filename
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	349	<b>-quiet - Don't print informational messages</b>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	350	-help - display available options (--help-hidden for more)
				351	</pre><p>
				352
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	353	and "<tt>opt --help-hidden</tt>" prints this:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	354
				355	<pre>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	356	USAGE: compiler [options] <input file>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	357
				358	OPTIONS:
				359	-f - Overwrite output files
				360	-o - Override output filename
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	361	<b>-q - Don't print informational messages</b>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	362	-quiet - Don't print informational messages
				363	-help - display available options (--help-hidden for more)
				364	</pre><p>
				365
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	366	This brief example has shown you how to use the '<tt><a
				367	href="#cl::opt">cl::opt</a></tt>' class to parse simple scalar command line
				368	arguments. In addition to simple scalar arguments, the CommandLine library also
				369	provides primitives to support CommandLine option <a href="#alias">aliases</a>,
				370	and <a href="#list">lists</a> of options.<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	371
				372
				373	<!-- ======================================================================= -->
				374	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	375	<a name="alias">Argument Aliases
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	376	</b></font></td></tr></table><ul>
				377
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	378	So far, the example works well, except for the fact that we need to check the
				379	quiet condition like this now:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	380
				381	<pre>
				382	...
				383	if (!Quiet && !Quiet2) printInformationalMessage(...);
				384	...
				385	</pre><p>
				386
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	387	... which is a real pain! Instead of defining two values for the same
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	388	condition, we can use the "<tt><a href="#cl::alias">cl::alias</a></tt>" class to make the "<tt>-q</tt>"
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	389	option an <b>alias</b> for the "<tt>-quiet</tt>" option, instead of providing
				390	a value itself:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	391
				392	<pre>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	393	<a href="#cl::opt">cl::opt</a><bool> Force ("<i>f</i>", <a href="#cl::desc">cl::desc</a>("<i>Overwrite output files</i>"));
				394	<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>"));
				395	<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));
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	396	</pre><p>
				397
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	398	The third line (which is the only one we modified from above) defines a
				399	"<tt>-q</tt> alias that updates the "<tt>Quiet</tt>" variable (as specified by
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	400	the <tt><a href="#cl::aliasopt">cl::aliasopt</a></tt> modifier) whenever it is
				401	specified. Because aliases do not hold state, the only thing the program has to
				402	query is the <tt>Quiet</tt> variable now. Another nice feature of aliases is
				403	that they automatically hide themselves from the <tt>-help</tt> output
				404	(although, again, they are still visible in the <tt>--help-hidden
				405	output</tt>).<p>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	406
				407	Now the application code can simply use:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	408
				409	<pre>
				410	...
				411	if (!Quiet) printInformationalMessage(...);
				412	...
				413	</pre><p>
				414
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	415	... which is much nicer! The "<tt><a href="#cl::alias">cl::alias</a></tt>" can be used to specify an
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	416	alternative name for any variable type, and has many uses.<p>
				417
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	418
				419
				420	<!-- ======================================================================= -->
				421	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	422	<a name="onealternative">Selecting an alternative from a set of possibilities
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	423	</b></font></td></tr></table><ul>
				424
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	425	So far, we have seen how the CommandLine library handles builtin types like
				426	<tt>std::string</tt>, <tt>bool</tt> and <tt>int</tt>, but how does it handle
				427	things it doesn't know about, like enums or '<tt>int*</tt>'s?<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	428
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	429	The answer is that it uses a table driven generic parser (unless you specify
				430	your own parser, as described in the <a href="#extensionguide">Extension
				431	Guide</a>). This parser maps literal strings to whatever type is required, are
				432	requires you to tell it what this mapping should be.<p>
				433
				434	Lets say that we would like to add four optimizations levels to our optimizer,
				435	using the standard flags "<tt>-g</tt>", "<tt>-O0</tt>", "<tt>-O1</tt>", and
				436	"<tt>-O2</tt>". We could easily implement this with boolean options like above,
				437	but there are several problems with this strategy:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	438
				439	<ol>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	440	<li>A user could specify more than one of the options at a time, for example,
				441	"<tt>opt -O3 -O2</tt>". The CommandLine library would not be able to catch this
				442	erroneous input for us.
				443
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	444	<li>We would have to test 4 different variables to see which ones are set.
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	445
				446	<li>This doesn't map to the numeric levels that we want... so we cannot easily
				447	see if some level >= "<tt>-O1</tt>" is enabled.
				448
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	449	</ol><p>
				450
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	451	To cope with these problems, we can use an enum value, and have the CommandLine
				452	library fill it in with the appropriate level directly, which is used like
				453	this:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	454
				455	<pre>
				456	enum OptLevel {
				457	g, O1, O2, O3
				458	};
				459
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	460	<a href="#cl::opt">cl::opt</a><OptLevel> OptimizationLevel(<a href="#cl::desc">cl::desc</a>("<i>Choose optimization level:</i>"),
				461	<a href="#cl::values">cl::values</a>(
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	462	clEnumVal(g , "<i>No optimizations, enable debugging</i>"),
				463	clEnumVal(O1, "<i>Enable trivial optimizations</i>"),
				464	clEnumVal(O2, "<i>Enable default optimizations</i>"),
				465	clEnumVal(O3, "<i>Enable expensive optimizations</i>"),
				466	0));
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	467
				468	...
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	469	if (OptimizationLevel >= O2) doPartialRedundancyElimination(...);
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	470	...
				471	</pre><p>
				472
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	473	This declaration defines a variable "<tt>OptimizationLevel</tt>" of the
				474	"<tt>OptLevel</tt>" enum type. This variable can be assigned any of the values
				475	that are listed in the declaration (Note that the declaration list must be
				476	terminated with the "<tt>0</tt>" argument!). The CommandLine library enforces
				477	that the user can only specify one of the options, and it ensure that only valid
				478	enum values can be specified. The "<tt>clEnumVal</tt>" macros ensure that the
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	479	command line arguments matched the enum values. With this option added, our
				480	help output now is:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	481
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	482	<pre>
				483	USAGE: compiler [options] <input file>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	484
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	485	OPTIONS:
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	486	<b>Choose optimization level:
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	487	-g - No optimizations, enable debugging
				488	-O1 - Enable trivial optimizations
				489	-O2 - Enable default optimizations
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	490	-O3 - Enable expensive optimizations</b>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	491	-f - Overwrite output files
				492	-help - display available options (--help-hidden for more)
				493	-o <filename> - Specify output filename
				494	-quiet - Don't print informational messages
				495	</pre>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	496
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	497	In this case, it is sort of awkward that flag names correspond directly to enum
				498	names, because we probably don't want a enum definition named "<tt>g</tt>" in
				499	our program. Because of this, we can alternatively write this example like
				500	this:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	501
				502	<pre>
				503	enum OptLevel {
				504	Debug, O1, O2, O3
				505	};
				506
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	507	<a href="#cl::opt">cl::opt</a><OptLevel> OptimizationLevel(<a href="#cl::desc">cl::desc</a>("<i>Choose optimization level:</i>"),
				508	<a href="#cl::values">cl::values</a>(
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	509	clEnumValN(Debug, "g", "<i>No optimizations, enable debugging</i>"),
				510	clEnumVal(O1 , "<i>Enable trivial optimizations</i>"),
				511	clEnumVal(O2 , "<i>Enable default optimizations</i>"),
				512	clEnumVal(O3 , "<i>Enable expensive optimizations</i>"),
				513	0));
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	514
				515	...
				516	if (OptimizationLevel == Debug) outputDebugInfo(...);
				517	...
				518	</pre><p>
				519
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	520	By using the "<tt>clEnumValN</tt>" macro instead of "<tt>clEnumVal</tt>", we can
				521	directly specify the name that the flag should get. In general a direct mapping
				522	is nice, but sometimes you can't or don't want to preserve the mapping, which is
				523	when you would use it.<p>
				524
				525
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	526
				527	<!-- ======================================================================= -->
				528	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				529	<a name="namedalternatives">Named Alternatives
				530	</b></font></td></tr></table><ul>
				531
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	532	Another useful argument form is a named alternative style. We shall use this
				533	style in our compiler to specify different debug levels that can be used.
				534	Instead of each debug level being its own switch, we want to support the
				535	following options, of which only one can be specified at a time:
				536	"<tt>--debug-level=none</tt>", "<tt>--debug-level=quick</tt>",
				537	"<tt>--debug-level=detailed</tt>". To do this, we use the exact same format as
				538	our optimization level flags, but we also specify an option name. For this
				539	case, the code looks like this:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	540
				541	<pre>
				542	enum DebugLev {
				543	nodebuginfo, quick, detailed
				544	};
				545
				546	// Enable Debug Options to be specified on the command line
Chris Lattner	dc844fa	2003-06-03 04:40:06 +0000	[diff] [blame]	547	<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>"),
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	548	<a href="#cl::values">cl::values</a>(
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	549	clEnumValN(nodebuginfo, "none", "<i>disable debug information</i>"),
				550	clEnumVal(quick, "<i>enable quick debug information</i>"),
				551	clEnumVal(detailed, "<i>enable detailed debug information</i>"),
				552	0));
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	553	</pre>
				554
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	555	This definition defines an enumerated command line variable of type "<tt>enum
				556	DebugLev</tt>", which works exactly the same way as before. The difference here
				557	is just the interface exposed to the user of your program and the help output by
				558	the "<tt>--help</tt>" option:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	559
				560	<pre>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	561	USAGE: compiler [options] <input file>
				562
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	563	OPTIONS:
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	564	Choose optimization level:
				565	-g - No optimizations, enable debugging
				566	-O1 - Enable trivial optimizations
				567	-O2 - Enable default optimizations
				568	-O3 - Enable expensive optimizations
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	569	<b>-debug_level - Set the debugging level:
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	570	=none - disable debug information
				571	=quick - enable quick debug information
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	572	=detailed - enable detailed debug information</b>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	573	-f - Overwrite output files
				574	-help - display available options (--help-hidden for more)
				575	-o <filename> - Specify output filename
				576	-quiet - Don't print informational messages
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	577	</pre><p>
				578
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	579	Again, the only structural difference between the debug level declaration and
				580	the optimiation level declaration is that the debug level declaration includes
				581	an option name (<tt>"debug_level"</tt>), which automatically changes how the
				582	library processes the argument. The CommandLine library supports both forms so
				583	that you can choose the form most appropriate for your application.<p>
				584
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	585
				586
				587	<!-- ======================================================================= -->
				588	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	589	<a name="list">Parsing a list of options
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	590	</b></font></td></tr></table><ul>
				591
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	592	Now that we have the standard run of the mill argument types out of the way,
				593	lets get a little wild and crazy. Lets say that we want our optimizer to accept
				594	a <b>list</b> of optimizations to perform, allowing duplicates. For example, we
				595	might want to run: "<tt>compiler -dce -constprop -inline -dce -strip</tt>". In
				596	this case, the order of the arguments and the number of appearances is very
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	597	important. This is what the "<tt><a href="#cl::list">cl::list</a></tt>"
				598	template is for. First, start by defining an enum of the optimizations that you
				599	would like to perform:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	600
				601	<pre>
				602	enum Opts {
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	603	// 'inline' is a C++ keyword, so name it 'inlining'
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	604	dce, constprop, inlining, strip
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	605	};
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	606	</pre><p>
				607
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	608	Then define your "<tt><a href="#cl::list">cl::list</a></tt>" variable:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	609
				610	<pre>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	611	<a href="#cl::list">cl::list</a><Opts> OptimizationList(<a href="#cl::desc">cl::desc</a>("<i>Available Optimizations:</i>"),
				612	<a href="#cl::values">cl::values</a>(
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	613	clEnumVal(dce , "<i>Dead Code Elimination</i>"),
Misha Brukman	82c89b9	2003-05-20 21:01:22 +0000	[diff] [blame]	614	clEnumVal(constprop , "<i>Constant Propagation</i>"),
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	615	clEnumValN(inlining, "<i>inline</i>", "<i>Procedure Integration</i>"),
				616	clEnumVal(strip , "<i>Strip Symbols</i>"),
				617	0));
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	618	</pre><p>
				619
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	620	This defines a variable that is conceptually of the type
				621	"<tt>std::vector<enum Opts></tt>". Thus, you can access it with standard
				622	vector methods:<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	623
				624	<pre>
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	625	for (unsigned i = 0; i != OptimizationList.size(); ++i)
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	626	switch (OptimizationList[i])
				627	...
				628	</pre>
				629
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	630	... to iterate through the list of options specified.<p>
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	631
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	632	Note that the "<tt><a href="#cl::list">cl::list</a></tt>" template is completely general and may be used
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	633	with any data types or other arguments that you can use with the
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	634	"<tt><a href="#cl::opt">cl::opt</a></tt>" template. One especially useful way to use a list is to
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	635	capture all of the positional arguments together if there may be more than one
				636	specified. In the case of a linker, for example, the linker takes several
				637	'<tt>.o</tt>' files, and needs to capture them into a list. This is naturally
				638	specified as:<p>
Chris Lattner	3e5fe17	2002-04-13 18:35:59 +0000	[diff] [blame]	639
				640	<pre>
				641	...
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	642	<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>);
Chris Lattner	3e5fe17	2002-04-13 18:35:59 +0000	[diff] [blame]	643	...
				644	</pre><p>
				645
Chris Lattner	ae85363	2002-07-25 19:27:01 +0000	[diff] [blame]	646	This variable works just like a "<tt>vector<string></tt>" object. As
				647	such, accessing the list is simple, just like above. In this example, we used
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	648	the <tt><a href="#cl::OneOrMore">cl::OneOrMore</a></tt> modifier to inform the
				649	CommandLine library that it is an error if the user does not specify any
				650	<tt>.o</tt> files on our command line. Again, this just reduces the amount of
				651	checking we have to do.<p>
Chris Lattner	3e5fe17	2002-04-13 18:35:59 +0000	[diff] [blame]	652
Chris Lattner	3e5fe17	2002-04-13 18:35:59 +0000	[diff] [blame]	653
				654
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	655	<!-- ======================================================================= -->
				656	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				657	<a name="description">Adding freeform text to help output
				658	</b></font></td></tr></table><ul>
				659
				660	As our program grows and becomes more mature, we may decide to put summary
				661	information about what it does into the help output. The help output is styled
				662	to look similar to a Unix <tt>man</tt> page, providing concise information about
				663	a program. Unix <tt>man</tt> pages, however often have a description about what
				664	the program does. To add this to your CommandLine program, simply pass a third
				665	argument to the <a
				666	href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>
				667	call in main. This additional argument is then printed as the overview
				668	information for your program, allowing you to include any additional information
				669	that you want. For example:<p>
				670
				671	<pre>
				672	int main(int argc, char **argv) {
				673	<a href="#cl::ParseCommandLineOptions">cl::ParseCommandLineOptions</a>(argc, argv, " CommandLine compiler example\n\n"
				674	" This program blah blah blah...\n");
				675	...
				676	}
				677	</pre><p>
				678
				679	Would yield the help output:
				680
				681	<pre>
				682	<b>OVERVIEW: CommandLine compiler example
				683
				684	This program blah blah blah...</b>
				685
				686	USAGE: compiler [options] <input file>
				687
				688	OPTIONS:
				689	...
				690	-help - display available options (--help-hidden for more)
				691	-o <filename> - Specify output filename
				692	</pre><p>
				693
				694
				695
				696
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	697	<!-- *********************************************************************** -->
				698	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				699	<a name="referenceguide">Reference Guide
				700	</b></font></td></tr></table><ul>
				701	<!-- *********************************************************************** -->
				702
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	703	Now that you know the basics of how to use the CommandLine library, this section
				704	will give you the detailed information you need to tune how command line options
				705	work, as well as information on more "advanced" command line option processing
				706	capabilities.<p>
				707
				708
				709	<!-- ======================================================================= -->
				710	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				711	<a name="positional">Positional Arguments
				712	</b></font></td></tr></table><ul>
				713
				714	Positional arguments are those arguments that are not named, and are not
				715	specified with a hyphen. Positional arguments should be used when an option is
				716	specified by its position alone. For example, the standard Unix <tt>grep</tt>
				717	tool takes a regular expression argument, and an optional filename to search
				718	through (which defaults to standard input if a filename is not specified).
				719	Using the CommandLine library, this would be specified as:<p>
				720
				721	<pre>
				722	<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>);
				723	<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>"));
				724	</pre>
				725
				726	Given these two option declarations, the <tt>--help</tt> output for our grep
				727	replacement would look like this:<p>
				728
				729	<pre>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	730	USAGE: spiffygrep [options] <b><regular expression> <input file></b>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	731
				732	OPTIONS:
				733	-help - display available options (--help-hidden for more)
				734	</pre>
				735
				736	... and the resultant program could be used just like the standard <tt>grep</tt>
				737	tool.<p>
				738
				739	Positional arguments are sorted by their order of construction. This means that
				740	command line options will be ordered according to how they are listed in a .cpp
				741	file, but will not have an ordering defined if they positional arguments are
				742	defined in multiple .cpp files. The fix for this problem is simply to define
				743	all of your positional arguments in one .cpp file.<p>
				744
				745
				746
				747	<!-- _______________________________________________________________________ -->
				748	</ul><a name="--"><h4><hr size=0>Specifying positional options with hyphens</h4><ul>
				749
				750	Sometimes you may want to specify a value to your positional argument that
				751	starts with a hyphen (for example, searching for '<tt>-foo</tt>' in a file). At
				752	first, you will have trouble doing this, because it will try to find an argument
				753	named '<tt>-foo</tt>', and will fail (and single quotes will not save you).
				754	Note that the system <tt>grep</tt> has the same problem:<p>
				755
				756	<pre>
				757	$ spiffygrep '-foo' test.txt
				758	Unknown command line argument '-foo'. Try: spiffygrep --help'
				759
				760	$ grep '-foo' test.txt
				761	grep: illegal option -- f
				762	grep: illegal option -- o
				763	grep: illegal option -- o
				764	Usage: grep -hblcnsviw pattern file . . .
				765	</pre><p>
				766
				767	The solution for this problem is the same for both your tool and the system
				768	version: use the '<tt>--</tt>' marker. When the user specifies '<tt>--</tt>' on
				769	the command line, it is telling the program that all options after the
				770	'<tt>--</tt>' should be treated as positional arguments, not options. Thus, we
				771	can use it like this:<p>
				772
				773	<pre>
				774	$ spiffygrep -- -foo test.txt
				775	...output...
				776	</pre><p>
				777
				778
				779
				780	<!-- _______________________________________________________________________ -->
				781	</ul><a name="cl::ConsumeAfter"><h4><hr size=0>The <tt>cl::ConsumeAfter</tt> modifier</h4><ul>
				782
				783	The <tt>cl::ConsumeAfter</tt> <a href="#formatting">formatting option</a> is
				784	used to construct programs that use "interpreter style" option processing. With
				785	this style of option processing, all arguments specified after the last
				786	positional argument are treated as special interpreter arguments that are not
				787	interpreted by the command line argument.<p>
				788
				789	As a concrete example, lets say we are developing a replacement for the standard
				790	Unix Bourne shell (<tt>/bin/sh</tt>). To run <tt>/bin/sh</tt>, first you
				791	specify options to the shell itself (like <tt>-x</tt> which turns on trace
				792	output), then you specify the name of the script to run, then you specify
				793	arguments to the script. These arguments to the script are parsed by the bourne
				794	shell command line option processor, but are not interpreted as options to the
				795	shell itself. Using the CommandLine library, we would specify this as:<p>
				796
				797	<pre>
				798	<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>("-"));
				799	<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>"));
				800	<a href="#cl::opt">cl::opt</a><bool> Trace("<i>x</i>", <a href="#cl::desc">cl::desc</a>("<i>Enable trace output</i>"));
				801	</pre><p>
				802
				803	which automatically provides the help output:<p>
				804
				805	<pre>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	806	USAGE: spiffysh [options] <b><input script> <program arguments>...</b>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	807
				808	OPTIONS:
				809	-help - display available options (--help-hidden for more)
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	810	<b>-x - Enable trace output</b>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	811	</pre><p>
				812
				813	At runtime, if we run our new shell replacement as '<tt>spiffysh -x test.sh -a
				814	-x -y bar</tt>', the <tt>Trace</tt> variable will be set to true, the
				815	<tt>Script</tt> variable will be set to "<tt>test.sh</tt>", and the
				816	<tt>Argv</tt> list will contain <tt>["-a", "-x", "-y", "bar"]</tt>, because
				817	they were specified after the last positional argument (which is the script
				818	name).<p>
				819
				820	There are several limitations to when <tt>cl::ConsumeAfter</tt> options can be
				821	specified. For example, only one <tt>cl::ConsumeAfter</tt> can be specified per
				822	program, there must be at least one <a href="#positional">positional
				823	argument</a> specified, and the <tt>cl::ConsumeAfter</tt> option should be a <a
				824	href="#cl::list">cl::list</a> option.<p>
				825
				826
				827
				828	<!-- ======================================================================= -->
				829	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				830	<a name="storage">Internal vs External Storage
				831	</b></font></td></tr></table><ul>
				832
				833	By default, all command line options automatically hold the value that they
				834	parse from the command line. This is very convenient in the common case,
				835	especially when combined with the ability to define command line options in the
				836	files that use them. This is called the internal storage model.<p>
				837
				838	Sometimes, however, it is nice to separate the command line option processing
				839	code from the storage of the value parsed. For example, lets say that we have a
				840	'<tt>-debug</tt>' option that we would like to use to enable debug information
				841	across the entire body of our program. In this case, the boolean value
				842	controlling the debug code should be globally accessable (in a header file, for
				843	example) yet the command line option processing code should not be exposed to
				844	all of these clients (requiring lots of .cpp files to #include
				845	<tt>CommandLine.h</tt>).<p>
				846
				847	To do this, set up your .h file with your option, like this for example:<p>
				848
				849	<pre>
				850	<i>// DebugFlag.h - Get access to the '-debug' command line option
				851	//
				852
				853	// DebugFlag - This boolean is set to true if the '-debug' command line option
				854	// is specified. This should probably not be referenced directly, instead, use
				855	// the DEBUG macro below.
				856	//</i>
				857	extern bool DebugFlag;
				858
				859	<i>// DEBUG macro - This macro should be used by code to emit debug information.
				860	// In the '-debug' option is specified on the command line, and if this is a
				861	// debug build, then the code specified as the option to the macro will be
				862	// executed. Otherwise it will not be. Example:
				863	//
				864	// DEBUG(cerr << "Bitset contains: " << Bitset << "\n");
				865	//</i>
				866	<font color=red>#ifdef NDEBUG
				867	#define DEBUG(X)
				868	#else
				869	#define DEBUG(X)</font> \
				870	do { if (DebugFlag) { X; } } while (0)
				871	<font color=red>#endif</font>
				872	</pre>
				873
				874	This allows clients to blissfully use the <tt>DEBUG()</tt> macro, or the
				875	<tt>DebugFlag</tt> explicitly if they want to. Now we just need to be able to
				876	set the <tt>DebugFlag</tt> boolean when the option is set. To do this, we pass
				877	an additial argument to our command line argument processor, and we specify
				878	where to fill in with the <a href="#cl::location">cl::location</a> attribute:<p>
				879
				880	<pre>
				881	bool DebugFlag; <i>// the actual value</i>
Chris Lattner	589a4cc	2003-08-01 21:30:37 +0000	[diff] [blame]	882	static <a href="#cl::opt">cl::opt</a><bool, true> <i>// The parser</i>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	883	Debug("<i>debug</i>", <a href="#cl::desc">cl::desc</a>("<i>Enable debug output</i>")</a>, <a href="#cl::Hidden">cl::Hidden</a>,
				884	<a href="#cl::location">cl::location</a>(DebugFlag));
				885	</pre>
				886
				887	In the above example, we specify "<tt>true</tt>" as the second argument to the
				888	<a href="#cl::opt">cl::opt</a> template, indicating that the template should not
				889	maintain a copy of the value itself. In addition to this, we specify the <a
				890	href="#cl::location">cl::location</a> attribute, so that <tt>DebugFlag</tt> is
				891	automatically set.<p>
				892
				893
				894
				895	<!-- ======================================================================= -->
				896	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				897	<a name="attributes">Option Attributes
				898	</b></font></td></tr></table><ul>
				899
				900	This section describes the basic attributes that you can specify on options.<p>
				901
				902	<ul>
				903
				904	<li>The option name attribute (which is required for all options, except <a
				905	href="#positional">positional options</a>) specifies what the option name is.
				906	This option is specified in simple double quotes:<p>
				907
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	908	<pre>
				909	<a href="#cl::opt">cl::opt</a><<b>bool</b>> Quiet("<i>quiet</i>");
				910	</pre><p>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	911
				912	<li><a name="cl::desc">The <b><tt>cl::desc</tt></b> attribute specifies a
				913	description for the option to be shown in the <tt>--help</tt> output for the
				914	program.<p>
				915
				916	<li><a name="cl::value_desc">The <b><tt>cl::value_desc</tt></b> attribute
				917	specifies a string that can be used to fine tune the <tt>--help</tt> output for
				918	a command line option. Look <a href="#value_desc_example">here</a> for an
				919	example.<p>
				920
				921	<li><a name="cl::init">The <b><tt>cl::init</tt></b> attribute specifies an
				922	inital value for a <a href="#cl::opt">scalar</a> option. If this attribute is
				923	not specified then the command line option value defaults to the value created
Brian Gaeke	9d292ff	2003-08-19 22:56:22 +0000	[diff] [blame]	924	by the default constructor for the type. <b>Warning</b>: If you specify both
				925	<b><tt>cl::init</tt></b> and <b><tt>cl::location</tt></b> for an option,
				926	you must specify <b><tt>cl::location</tt></b> first, so that when the
				927	command-line parser sees <b><tt>cl::init</tt></b>, it knows where to put the
				928	initial value. (You will get an error at runtime if you don't put them in
				929	the right order.)<p>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	930
				931	<li><a name="cl::location">The <b><tt>cl::location</tt></b> attribute where to
				932	store the value for a parsed command line option if using external storage. See
				933	the section on <a href="#storage">Internal vs External Storage</a> for more
				934	information.<p>
				935
				936	<li><a name="cl::aliasopt">The <b><tt>cl::aliasopt</tt></b> attribute specifies
				937	which option a <a href="#cl::alias">cl::alias</a> option is an alias for.<p>
				938
				939	<li><a name="cl::values">The <b><tt>cl::values</tt></b> attribute specifies the
				940	string-to-value mapping to be used by the generic parser. It takes a <b>null
				941	terminated</b> list of (option, value, description) triplets that specify the
				942	option name, the value mapped to, and the description shown in the
				943	<tt>--help</tt> for the tool. Because the generic parser is used most frequently with enum values, two macros are often useful:<p>
				944	<ol>
				945	<li><a name="clEnumVal">The <b><tt>clEnumVal</tt></b> macro is used as a nice
				946	simple way to specify a triplet for an enum. This macro automatically makes the
				947	option name be the same as the enum name. The first option to the macro is the
				948	enum, the second is the description for the command line option.<p> <li><a
				949	name="clEnumValN">The <b><tt>clEnumValN</tt></b> macro is used to specify macro
				950	options where the option name doesn't equal the enum name. For this macro, the
				951	first argument is the enum value, the second is the flag name, and the second is
				952	the description.<p>
				953	</ol>
				954
				955	You will get a compile time error if you try to use cl::values with a parser
				956	that does not support it.<p>
				957
				958	</ul>
				959
				960
				961
				962	<!-- ======================================================================= -->
				963	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				964	<a name="modifiers">Option Modifiers
				965	</b></font></td></tr></table><ul>
				966
				967	Option modifiers are the flags and expressions that you pass into the
				968	constructors for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
				969	href="#cl::list">cl::list</a></tt>. These modifiers give you the ability to
				970	tweak how options are parsed and how <tt>--help</tt> output is generated to fit
				971	your application well.<p>
				972
Chris Lattner	32a3284	2003-05-22 20:36:06 +0000	[diff] [blame]	973	These options fall into five main catagories:<p>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	974
				975	<ol>
				976	<li><a href="#hiding">Hiding an option from <tt>--help</tt> output</a>
				977	<li><a href="#numoccurances">Controlling the number of occurances
				978	required and allowed</a>
				979	<li><a href="#valrequired">Controlling whether or not a value must be
				980	specified</a>
				981	<li><a href="#formatting">Controlling other formatting options</a>
Chris Lattner	32a3284	2003-05-22 20:36:06 +0000	[diff] [blame]	982	<li><a href="#misc">Miscellaneous option modifiers</a>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	983	</ol><p>
				984
				985	It is not possible to specify two options from the same catagory (you'll get a
Chris Lattner	32a3284	2003-05-22 20:36:06 +0000	[diff] [blame]	986	runtime error) to a single option, except for options in the miscellaneous
				987	catagory. The CommandLine library specifies defaults for all of these settings
				988	that are the most useful in practice and the most common, which mean that you
				989	usually shouldn't have to worry about these.<p>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	990
				991
				992	<!-- _______________________________________________________________________ -->
				993	</ul><a name="hiding"><h4><hr size=0>Hiding an option from <tt>--help</tt> output</h4><ul>
				994
				995	The <tt>cl::NotHidden</tt>, <tt>cl::Hidden</tt>, and <tt>cl::ReallyHidden</tt>
				996	modifiers are used to control whether or not an option appears in the
				997	<tt>--help</tt> and <tt>--help-hidden</tt> output for the compiled program:<p>
				998
				999	<ul>
				1000
				1001	<a name="cl::NotHidden">The <b><tt>cl::NotHidden</tt></b> modifier (which is the
				1002	default for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
				1003	href="#cl::list">cl::list</a></tt> options), indicates the option is to appear
				1004	in both help listings.<p>
				1005
				1006	<a name="cl::Hidden">The <b><tt>cl::Hidden</tt></b> modifier (which is the
				1007	default for <tt><a href="#cl::alias">cl::alias</a></tt> options), indicates that
				1008	the option should not appear in the <tt>--help</tt> output, but should appear in
				1009	the <tt>--help-hidden</tt> output.<p>
				1010
				1011	<a name="cl::ReallyHidden">The <b><tt>cl::ReallyHidden</tt></b> modifier,
				1012	indicates that the option should not appear in any help output.<p>
				1013	</ul>
				1014
				1015	<!-- _______________________________________________________________________ -->
				1016	</ul><a name="numoccurances"><h4><hr size=0>Controlling the number of occurances required and allowed</h4><ul>
				1017
				1018	This group of options is used to control how many time an option is allowed (or
				1019	required) to be specified on the command line of your program. Specifying a
				1020	value for this setting allows the CommandLine library to do error checking for
				1021	you.<p>
				1022
				1023	The allowed values for this option group are:<p>
				1024
				1025	<ul>
				1026	<a name="cl::Optional">The <b><tt>cl::Optional</tt></b> modifier (which is the
				1027	default for the <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
				1028	href="#cl::alias">cl::alias</a></tt> classes) indicates that your program will
				1029	allow either zero or one occurance of the option to be specified.<p>
				1030
				1031	<a name="cl::ZeroOrMore">The <b><tt>cl::ZeroOrMore</tt></b> modifier (which is
				1032	the default for the <tt><a href="#cl::list">cl::list</a></tt> class) indicates
				1033	that your program will allow the option to be specified zero or more times.<p>
				1034
				1035	<a name="cl::Required">The <b><tt>cl::Required</tt></b> modifier indicates that
				1036	the specified option must be specified exactly one time.<p>
				1037
				1038	<a name="cl::OneOrMore">The <b><tt>cl::OneOrMore</tt></b> modifier indicates
				1039	that the option must be specified at least one time.<p>
				1040
				1041	The <b><tt>cl::ConsumeAfter</tt></b> modifier is described in the <a
				1042	href="#positional">Positional arguments section</a><p>
				1043
				1044	</ul>
				1045
				1046	If an option is not specified, then the value of the option is equal to the
				1047	value specified by the <tt><a href="#cl::init">cl::init</a></tt> attribute. If
				1048	the <tt><a href="#cl::init">cl::init</a></tt> attribute is not specified, the
				1049	option value is initialized with the default constructor for the data type.<p>
				1050
				1051	If an option is specified multiple times for an option of the <tt><a
				1052	href="#cl::opt">cl::opt</a></tt> class, only the last value will be retained.<p>
				1053
				1054
				1055	<!-- _______________________________________________________________________ -->
				1056	</ul><a name="valrequired"><h4><hr size=0>Controlling whether or not a value must be specified</h4><ul>
				1057
				1058	This group of options is used to control whether or not the option allows a
				1059	value to be present. In the case of the CommandLine library, a value is either
				1060	specified with an equal sign (e.g. '<tt>-index-depth=17</tt>') or as a trailing
				1061	string (e.g. '<tt>-o a.out</tt>').<p>
				1062
				1063	The allowed values for this option group are:<p>
				1064
				1065	<ul>
				1066	<a name="cl::ValueOptional">The <b><tt>cl::ValueOptional</tt></b> modifier
				1067	(which is the default for <tt>bool</tt> typed options) specifies that it is
				1068	acceptable to have a value, or not. A boolean argument can be enabled just by
				1069	appearing on the command line, or it can have an explicit '<tt>-foo=true</tt>'.
				1070	If an option is specified with this mode, it is illegal for the value to be
				1071	provided without the equal sign. Therefore '<tt>-foo true</tt>' is illegal. To
				1072	get this behavior, you must use the <a
				1073	href="#cl::ValueRequired">cl::ValueRequired</a> modifier.<p>
				1074
				1075	<a name="cl::ValueRequired">The <b><tt>cl::ValueRequired</tt></b> modifier
				1076	(which is the default for all other types except for <a
				1077	href="#onealternative">unnamed alternatives using the generic parser</a>)
				1078	specifies that a value must be provided. This mode informs the command line
				1079	library that if an option is not provides with an equal sign, that the next
				1080	argument provided must be the value. This allows things like '<tt>-o
				1081	a.out</tt>' to work.<p>
				1082
				1083	<a name="cl::ValueDisallowed">The <b><tt>cl::ValueDisallowed</tt></b> modifier
				1084	(which is the default for <a href="#onealternative">unnamed alternatives using
				1085	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>').<p>
				1086
				1087	</ul>
				1088
				1089	In general, the default values for this option group work just like you would
				1090	want them to. As mentioned above, you can specify the <a
				1091	href="#cl::ValueDisallowed">cl::ValueDisallowed</a> modifier to a boolean
				1092	argument to restrict your command line parser. These options are mostly useful
				1093	when <a href="#extensionguide">extending the library</a>.<p>
				1094
				1095
				1096
				1097	<!-- _______________________________________________________________________ -->
				1098	</ul><a name="formatting"><h4><hr size=0>Controlling other formatting options</h4><ul>
				1099
				1100	The formatting option group is used to specify that the command line option has
				1101	special abilities and is otherwise different from other command line arguments.
				1102	As usual, you can only specify at most one of these arguments.<p>
				1103
				1104	<ul>
				1105	<a name="cl::NormalFormatting">The <b><tt>cl::NormalFormatting</tt></b> modifier
				1106	(which is the default all options) specifies that this option is "normal".<p>
				1107
				1108	<a name="cl::Positional">The <b><tt>cl::Positional</tt></b> modifier specifies
				1109	that this is a positional argument, that does not have a command line option
				1110	associated with it. See the <a href="#positional">Positional Arguments</a>
				1111	section for more information.<p>
				1112
				1113	The <b><a href="#cl::ConsumeAfter"><tt>cl::ConsumeAfter</tt></a></b> modifier
				1114	specifies that this option is used to capture "interpreter style" arguments. See <a href="#cl::ConsumeAfter">this section for more information</a>.<p>
				1115
				1116
				1117	<a name="cl::Prefix">The <b><tt>cl::Prefix</tt></b> modifier specifies that this
				1118	option prefixes its value. With 'Prefix' options, there is no equal sign that
Misha Brukman	bc0e998	2003-07-14 17:20:40 +0000	[diff] [blame]	1119	separates the value from the option name specified. This is useful for
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1120	processing odd arguments like '<tt>-lmalloc -L/usr/lib'</tt> in a linker tool.
				1121	Here, the '<tt>l</tt>' and '<tt>L</tt>' options are normal string (list)
				1122	options, that have the <a href="#cl::Prefix">cl::Prefix</a> modifier added to
				1123	allow the CommandLine library to recognize them. Note that <a
				1124	href="#cl::Prefix">cl::Prefix</a> options must not have the <a
				1125	href="#cl::ValueDisallowed">cl::ValueDisallowed</a> modifier specified.<p>
				1126
				1127	<a name="cl::Grouping">The <b><tt>cl::Grouping</tt></b> modifier is used to
				1128	implement unix style tools (like <tt>ls</tt>) that have lots of single letter
				1129	arguments, but only require a single dash. For example, the '<tt>ls -labF</tt>'
				1130	command actually enables four different options, all of which are single
				1131	letters. Note that <a href="#cl::Grouping">cl::Grouping</a> options cannot have
				1132	values.<p>
				1133
				1134	</ul>
				1135
				1136	The CommandLine library does not restrict how you use the <a
				1137	href="#cl::Prefix">cl::Prefix</a> or <a href="#cl::Grouping">cl::Grouping</a>
				1138	modifiers, but it is possible to specify ambiguous argument settings. Thus, it
				1139	is possible to have multiple letter options that are prefix or grouping options,
				1140	and they will still work as designed.<p>
				1141
				1142	To do this, the CommandLine library uses a greedy algorithm to parse the input
				1143	option into (potentially multiple) prefix and grouping options. The strategy
				1144	basically looks like this:<p>
				1145
				1146	<tt>parse(string OrigInput) {</tt>
				1147	<ol>
				1148	<li><tt>string input = OrigInput;</tt>
				1149	<li><tt>if (isOption(input)) return getOption(input).parse();</tt>    <i>// Normal option</i>
				1150	<li><tt>while (!isOption(input) && !input.empty()) input.pop_back();</tt>    <i>// Remove the last letter</i>
				1151	<li><tt>if (input.empty()) return error();</tt>    <i>// No matching option</i>
				1152	<li><tt>if (getOption(input).isPrefix())<br>
				1153	return getOption(input).parse(input);</tt>
				1154	<li><tt>while (!input.empty()) {    <i>// Must be grouping options</i><br>
				1155	getOption(input).parse();<br>
				1156	OrigInput.erase(OrigInput.begin(), OrigInput.begin()+input.length());<br>
				1157	input = OrigInput;<br>
				1158	while (!isOption(input) && !input.empty()) input.pop_back();<br>
				1159	}</tt>
				1160	<li><tt>if (!OrigInput.empty()) error();</tt>
				1161	</tt>
				1162
				1163	</ol>
				1164	<tt>}</tt><p>
				1165
				1166
Chris Lattner	32a3284	2003-05-22 20:36:06 +0000	[diff] [blame]	1167
				1168	<!-- _______________________________________________________________________ -->
				1169	</ul><a name="misc"><h4><hr size=0>Miscellaneous option modifiers</h4><ul>
				1170
				1171	The miscellaneous option modifiers are the only flags where you can specify more
				1172	than one flag from the set: they are not mutually exclusive. These flags
				1173	specify boolean properties that modify the option.<p>
				1174
				1175	<ul>
				1176
				1177	<a name="cl::CommaSeparated">The <b><tt>cl::CommaSeparated</tt></b> modifier
				1178	indicates that any commas specified for an option's value should be used to
				1179	split the value up into multiple values for the option. For example, these two
				1180	options are equivalent when <tt>cl::CommaSeparated</tt> is specified:
				1181	"<tt>-foo=a -foo=b -foo=c</tt>" and "<tt>-foo=a,b,c</tt>". This option only
				1182	makes sense to be used in a case where the option is allowed to accept one or
				1183	more values (i.e. it is a <a href="#cl::list">cl::list</a> option).<p>
				1184	</ul>
				1185
				1186	So far, the only miscellaneous option modifier is the
				1187	<tt>cl::CommaSeparated</tt> modifier.<p>
				1188
				1189
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1190	<!-- ======================================================================= -->
				1191	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	1192	<a name="toplevel">Top-Level Classes and Functions
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1193	</b></font></td></tr></table><ul>
				1194
				1195	Despite all of the builtin flexibility, the CommandLine option library really
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	1196	only consists of one function (<a
				1197	href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>)
				1198	and three main classes: <a href="#cl::opt"><tt>cl::opt</tt></a>, <a
				1199	href="#cl::list"><tt>cl::list</tt></a>, and <a
				1200	href="#cl::alias"><tt>cl::alias</tt></a>. This section describes these three
				1201	classes in detail.<p>
				1202
				1203	<!-- _______________________________________________________________________ -->
				1204	</ul><a name="cl::ParseCommandLineOptions"><h4><hr size=0>The
				1205	<tt>cl::ParseCommandLineOptions</tt> function</h4><ul>
				1206
				1207	The <tt>cl::ParseCommandLineOptions</tt> function is designed to be called
				1208	directly from <tt>main</tt>, and is used to fill in the values of all of the
				1209	command line option variables once <tt>argc</tt> and <tt>argv</tt> are
				1210	available.<p>
				1211
				1212	The <tt>cl::ParseCommandLineOptions</tt> function requires two parameters
				1213	(<tt>argc</tt> and <tt>argv</tt>), but may also take an optional third parameter
				1214	which holds <a href="#description">additional extra text</a> to emit when the
				1215	<tt>--help</tt> option is invoked.<p>
				1216
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1217
				1218	<!-- _______________________________________________________________________ -->
Brian Gaeke	e584285	2003-08-19 23:11:43 +0000	[diff] [blame^]	1219	</ul><a name="cl::ParseEnvironmentOptions"><h4><hr size=0>The
				1220	<tt>cl::ParseEnvironmentOptions</tt> function</h4><ul>
				1221
				1222	The <tt>cl::ParseEnvironmentOptions</tt>
				1223	function has mostly the same effects as
				1224	<a href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>,
				1225	except that it is designed to take values for options from an
				1226	environment variable, for those cases in which reading the
				1227	command line is not convenient or not desired. It fills in
				1228	the values of all the command line option variables just like
				1229	<a href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>
				1230	does.<p>
				1231
				1232	It takes three parameters: first, the name of the program (since <tt>argv</tt>
				1233	may not be available, it can't just look in <tt>argv[0]</tt>), second,
				1234	the name of the environment variable to examine, and third, the optional
				1235	<a href="#description">additional extra text</a> to emit when the
				1236	<tt>--help</tt> option is invoked.<p>
				1237
				1238	<tt>cl::ParseEnvironmentOptions</tt> will break the environment
				1239	variable's value up into words and then process them using
				1240	<a href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>.
				1241	<b>Note:</b> Currently <tt>cl::ParseEnvironmentOptions</tt> does not support
				1242	quoting, so an environment variable containing <tt>-option "foo bar"</tt> will
				1243	be parsed as three words, <tt>-option</tt>, <tt>"foo</tt>, and <tt>bar"</tt>,
				1244	which is different from what you would get from the shell with the same
				1245	input.<p>
				1246
				1247	<!-- _______________________________________________________________________ -->
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1248	</ul><a name="cl::opt"><h4><hr size=0>The <tt>cl::opt</tt> class</h4><ul>
				1249
				1250	The <tt>cl::opt</tt> class is the class used to represent scalar command line
				1251	options, and is the one used most of the time. It is a templated class which
				1252	can take up to three arguments (all except for the first have default values
				1253	though):<p>
				1254
				1255	<pre>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	1256	<b>namespace</b> cl {
				1257	<b>template</b> <<b>class</b> DataType, <b>bool</b> ExternalStorage = <b>false</b>,
				1258	<b>class</b> ParserClass = parser<DataType> >
				1259	<b>class</b> opt;
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1260	}
				1261	</pre><p>
				1262
				1263	The first template argument specifies what underlying data type the command line
				1264	argument is, and is used to select a default parser implementation. The second
				1265	template argument is used to specify whether the option should contain the
				1266	storage for the option (the default) or whether external storage should be used
				1267	to contain the value parsed for the option (see <a href="#storage">Internal vs
				1268	External Storage</a> for more information).<p>
				1269
				1270	The third template argument specifies which parser to use. The default value
				1271	selects an instantiation of the <tt>parser</tt> class based on the underlying
				1272	data type of the option. In general, this default works well for most
				1273	applications, so this option is only used when using a <a
				1274	href="#customparser">custom parser</a>.<p>
				1275
				1276
				1277	<!-- _______________________________________________________________________ -->
				1278	</ul><a name="cl::list"><h4><hr size=0>The <tt>cl::list</tt> class</h4><ul>
				1279
				1280	The <tt>cl::list</tt> class is the class used to represent a list of command
				1281	line options. It too is a templated class which can take up to three
				1282	arguments:<p>
				1283
				1284	<pre>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	1285	<b>namespace</b> cl {
				1286	<b>template</b> <<b>class</b> DataType, <b>class</b> Storage = <b>bool</b>,
				1287	<b>class</b> ParserClass = parser<DataType> >
				1288	<b>class</b> list;
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1289	}
				1290	</pre><p>
				1291
				1292	This class works the exact same as the <a href="#cl::opt"><tt>cl::opt</tt></a>
				1293	class, except that the second argument is the <b>type</b> of the external
				1294	storage, not a boolean value. For this class, the marker type '<tt>bool</tt>'
				1295	is used to indicate that internal storage should be used.<p>
				1296
				1297
				1298	<!-- _______________________________________________________________________ -->
				1299	</ul><a name="cl::alias"><h4><hr size=0>The <tt>cl::alias</tt> class</h4><ul>
				1300
				1301	The <tt>cl::alias</tt> class is a nontemplated class that is used to form
				1302	aliases for other arguments.<p>
				1303
				1304	<pre>
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	1305	<b>namespace</b> cl {
				1306	<b>class</b> alias;
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1307	}
				1308	</pre></p>
				1309
				1310	The <a href="#cl::aliasopt"><tt>cl::aliasopt</tt></a> attribute should be used
				1311	to specify which option this is an alias for. Alias arguments default to being
				1312	<a href="#cl::Hidden">Hidden</a>, and use the aliased options parser to do the
				1313	conversion from string to data.<p>
				1314
				1315
				1316	<!-- ======================================================================= -->
				1317	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%">  <font color="#EEEEFF" face="Georgia,Palatino"><b>
				1318	<a name="builtinparsers">Builtin parsers
				1319	</b></font></td></tr></table><ul>
				1320
				1321	Parsers control how the string value taken from the command line is translated
				1322	into a typed value, suitable for use in a C++ program. By default, the
				1323	CommandLine library uses an instance of <tt>parser<type></tt> if the
				1324	command line option specifies that it uses values of type '<tt>type</tt>'.
				1325	Because of this, custom option processing is specified with specializations of
				1326	the '<tt>parser</tt>' class.<p>
				1327
				1328	The CommandLine library provides the following builtin parser specializations,
				1329	which are sufficient for most applications. It can, however, also be extended to
				1330	work with new data types and new ways of interpreting the same data. See the <a
				1331	href="#customparser">Writing a Custom Parser</a> for more details on this type
				1332	of library extension.<p>
				1333
				1334	<li><a name="genericparser">The <b>generic <tt>parser<t></tt> parser</b>
				1335	can be used to map strings values to any data type, through the use of the <a
				1336	href="#cl::values">cl::values</a> property, which specifies the mapping
				1337	information. The most common use of this parser is for parsing enum values,
				1338	which allows you to use the CommandLine library for all of the error checking to
				1339	make sure that only valid enum values are specified (as opposed to accepting
				1340	arbitrary strings). Despite this, however, the generic parser class can be used
				1341	for any data type.<p>
				1342
				1343	<li><a name="boolparser">The <b><tt>parser<bool></tt> specialization</b>
				1344	is used to convert boolean strings to a boolean value. Currently accepted
				1345	strings are "<tt>true</tt>", "<tt>TRUE</tt>", "<tt>True</tt>", "<tt>1</tt>",
				1346	"<tt>false</tt>", "<tt>FALSE</tt>", "<tt>False</tt>", and "<tt>0</tt>".<p>
				1347
				1348	<li><a name="stringparser">The <b><tt>parser<string></tt> specialization</b> simply stores the parsed string into the string value specified. No conversion or modification of the data is performed.<p>
				1349
				1350	<li><a name="intparser">The <b><tt>parser<int></tt> specialization</b>
				1351	uses the C <tt>strtol</tt> function to parse the string input. As such, it will
				1352	accept a decimal number (with an optional '+' or '-' prefix) which must start
				1353	with a non-zero digit. It accepts octal numbers, which are identified with a
				1354	'<tt>0</tt>' prefix digit, and hexadecimal numbers with a prefix of
				1355	'<tt>0x</tt>' or '<tt>0X</tt>'.<p>
				1356
				1357	<li><a name="doubleparser">The <b><tt>parser<double></tt></b> and
				1358	<b><tt>parser<float></tt> specializations</b> use the standard C
				1359	<tt>strtod</tt> function to convert floating point strings into floating point
				1360	values. As such, a broad range of string formats is supported, including
				1361	exponential notation (ex: <tt>1.7e15</tt>) and properly supports locales.
				1362	<p>
				1363
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	1364
				1365
				1366	<!-- *********************************************************************** -->
				1367	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				1368	<a name="extensionguide">Extension Guide
				1369	</b></font></td></tr></table><ul>
				1370	<!-- *********************************************************************** -->
				1371
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	1372	Although the CommandLine library has a lot of functionality built into it
				1373	already (as discussed previously), one of its true strengths lie in its
				1374	extensibility. This section discusses how the CommandLine library works under
				1375	the covers and illustrates how to do some simple, common, extensions.<p>
				1376
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	1377
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1378	<!-- ======================================================================= -->
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	1379	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1380	<tr><td> </td><td width="100%">  <font color="#EEEEFF"
				1381	face="Georgia,Palatino"><b> <a name="customparser">Writing a custom parser
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1382	</b></font></td></tr></table><ul>
				1383
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	1384	One of the simplest and most common extensions is the use of a custom parser.
				1385	As <a href="#builtinparsers">discussed previously</a>, parsers are the portion
				1386	of the CommandLine library that turns string input from the user into a
				1387	particular parsed data type, validating the input in the process.<p>
				1388
				1389	There are two ways to use a new parser:<p>
				1390
				1391	<ol>
				1392	<li>Specialize the <a href="#genericparser"><tt>cl::parser</tt></a> template for
				1393	your custom data type.<p>
				1394
				1395	This approach has the advantage that users of your custom data type will
				1396	automatically use your custom parser whenever they define an option with a
				1397	value type of your data type. The disadvantage of this approach is that it
				1398	doesn't work if your fundemental data type is something that is already
				1399	supported.<p>
				1400
				1401	<li>Write an independant class, using it explicitly from options that need
				1402	it.<p>
				1403
				1404	This approach works well in situations where you would line to parse an
				1405	option using special syntax for a not-very-special data-type. The drawback
				1406	of this approach is that users of your parser have to be aware that they are
				1407	using your parser, instead of the builtin ones.<p>
				1408
				1409	</ol><p>
				1410
				1411	To guide the discussion, we will discuss a custom parser that accepts file
				1412	sizes, specified with an optional unit after the numeric size. For example, we
				1413	would like to parse "102kb", "41M", "1G" into the appropriate integer value. In
				1414	this case, the underlying data type we want to parse into is
				1415	'<tt>unsigned</tt>'. We choose approach #2 above because we don't want to make
				1416	this the default for all <tt>unsigned</tt> options.<p>
				1417
				1418	To start out, we declare our new <tt>FileSizeParser</tt> class:<p>
				1419
				1420	<pre>
				1421	<b>struct</b> FileSizeParser : <b>public</b> cl::basic_parser<<b>unsigned</b>> {
				1422	<i>// parse - Return true on error.</i>
				1423	<b>bool</b> parse(cl::Option &O, <b>const char</b> *ArgName, <b>const</b> std::string &ArgValue,
				1424	<b>unsigned</b> &Val);
				1425	};
				1426	</pre><p>
				1427
				1428	Our new class inherits from the <tt>cl::basic_parser</tt> template class to fill
				1429	in the default, boiler plate, code for us. We give it the data type that we
				1430	parse into (the last argument to the <tt>parse</tt> method so that clients of
				1431	our custom parser know what object type to pass in to the parse method (here we
				1432	declare that we parse into '<tt>unsigned</tt>' variables.<p>
				1433
				1434	For most purposes, the only method that must be implemented in a custom parser
				1435	is the <tt>parse</tt> method. The <tt>parse</tt> method is called whenever the
				1436	option is invoked, passing in the option itself, the option name, the string to
				1437	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>
				1438
				1439	<pre>
				1440	<b>bool</b> FileSizeParser::parse(cl::Option &O, <b>const char</b> *ArgName,
				1441	<b>const</b> std::string &Arg, <b>unsigned</b> &Val) {
				1442	<b>const char</b> *ArgStart = Arg.c_str();
				1443	<b>char</b> *End;
				1444
				1445	<i>// Parse integer part, leaving 'End' pointing to the first non-integer char</i>
				1446	Val = (unsigned)strtol(ArgStart, &End, 0);
				1447
				1448	<b>while</b> (1) {
				1449	<b>switch</b> (*End++) {
				1450	<b>case</b> 0: <b>return</b> false; <i>// No error</i>
				1451	<b>case</b> 'i': <i>// Ignore the 'i' in KiB if people use that</i>
				1452	<b>case</b> 'b': <b>case</b> 'B': <i>// Ignore B suffix</i>
				1453	<b>break</b>;
				1454
				1455	<b>case</b> 'g': <b>case</b> 'G': Val = 10241024*1024; <b>break</b>;
				1456	<b>case</b> 'm': <b>case</b> 'M': Val = 10241024; <b>break</b>;
				1457	<b>case</b> 'k': <b>case</b> 'K': Val *= 1024; <b>break</b>;
				1458
				1459	default:
				1460	<i>// Print an error message if unrecognized character!</i>
				1461	<b>return</b> O.error(": '" + Arg + "' value invalid for file size argument!");
				1462	}
				1463	}
				1464	}
				1465	</pre><p>
				1466
				1467	This function implements a very simple parser for the kinds of strings we are
				1468	interested in. Although it has some holes (it allows "<tt>123KKK</tt>" for
				1469	example), it is good enough for this example. Note that we use the option
				1470	itself to print out the error message (the <tt>error</tt> method always returns
				1471	true) in order to get a nice error message (shown below). Now that we have our
				1472	parser class, we can use it like this:<p>
				1473
				1474	<pre>
				1475	<b>static</b> <a href="#cl::opt">cl::opt</a><<b>unsigned</b>, <b>false</b>, FileSizeParser>
				1476	MFS(<i>"max-file-size"</i>, <a href="#cl::desc">cl::desc</a>(<i>"Maximum file size to accept"</i>),
				1477	<a href="#cl::value_desc">cl::value_desc</a>("<i>size</i>"));
				1478	</pre><p>
				1479
				1480	Which adds this to the output of our program:<p>
				1481
				1482	<pre>
				1483	OPTIONS:
				1484	-help - display available options (--help-hidden for more)
				1485	...
				1486	<b>-max-file-size=<size> - Maximum file size to accept</b>
				1487	</pre><p>
				1488
				1489	And we can test that our parse works correctly now (the test program just prints
				1490	out the max-file-size argument value):<p>
				1491
				1492	<pre>
				1493	$ ./test
				1494	MFS: 0
				1495	$ ./test -max-file-size=123MB
				1496	MFS: 128974848
				1497	$ ./test -max-file-size=3G
				1498	MFS: 3221225472
				1499	$ ./test -max-file-size=dog
				1500	-max-file-size option: 'dog' value invalid for file size argument!
				1501	</pre><p>
				1502
				1503	It looks like it works. The error message that we get is nice and helpful, and
				1504	we seem to accept reasonable file sizes. This wraps up the "custom parser"
				1505	tutorial.<p>
				1506
				1507
				1508	<!-- ======================================================================= -->
				1509	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1510	<tr><td> </td><td width="100%">  <font color="#EEEEFF"
				1511	face="Georgia,Palatino"><b> <a name="explotingexternal">Exploiting external
				1512	storage </b></font></td></tr></table><ul>
				1513
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1514
				1515
				1516	<!-- ======================================================================= -->
Chris Lattner	c1ae40c	2002-08-07 18:27:04 +0000	[diff] [blame]	1517	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1518	<tr><td> </td><td width="100%">  <font color="#EEEEFF"
				1519	face="Georgia,Palatino"><b> <a name="dynamicopts">Dynamically adding command
				1520	line options </b></font></td></tr></table><ul>
Chris Lattner	e76d4ab	2002-08-06 19:36:06 +0000	[diff] [blame]	1521
				1522
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	1523
				1524
				1525
				1526	<!-- *********************************************************************** -->
				1527	</ul>
				1528	<!-- *********************************************************************** -->
				1529
				1530	<hr>
				1531	<font size=-1>
				1532	<address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
				1533	<!-- Created: Tue Jan 23 15:19:28 CST 2001 -->
				1534	<!-- hhmts start -->
Chris Lattner	589a4cc	2003-08-01 21:30:37 +0000	[diff] [blame]	1535	Last modified: Fri Aug 1 16:30:11 CDT 2003
Chris Lattner	209c7f4	2001-07-23 23:03:12 +0000	[diff] [blame]	1536	<!-- hhmts end -->
				1537	</font>
				1538	</body></html>