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