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1744 lines
67 KiB
ReStructuredText
==============================
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CommandLine 2.0 Library Manual
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==============================
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.. contents::
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:local:
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Introduction
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============
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This document describes the CommandLine argument processing library. It will
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show you how to use it, and what it can do. The CommandLine library uses a
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declarative approach to specifying the command line options that your program
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takes. By default, these options declarations implicitly hold the value parsed
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for the option declared (of course this `can be changed`_).
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Although there are a **lot** of command line argument parsing libraries out
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there in many different languages, none of them fit well with what I needed. By
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looking at the features and problems of other libraries, I designed the
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CommandLine library to have the following features:
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#. Speed: The CommandLine library is very quick and uses little resources. The
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parsing time of the library is directly proportional to the number of
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arguments parsed, not the number of options recognized. Additionally,
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command line argument values are captured transparently into user defined
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global variables, which can be accessed like any other variable (and with the
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same performance).
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#. Type Safe: As a user of CommandLine, you don't have to worry about
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remembering the type of arguments that you want (is it an int? a string? a
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bool? an enum?) and keep casting it around. Not only does this help prevent
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error prone constructs, it also leads to dramatically cleaner source code.
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#. No subclasses required: To use CommandLine, you instantiate variables that
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correspond to the arguments that you would like to capture, you don't
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subclass a parser. This means that you don't have to write **any**
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boilerplate code.
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#. Globally accessible: Libraries can specify command line arguments that are
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automatically enabled in any tool that links to the library. This is
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possible because the application doesn't have to keep a list of arguments to
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pass to the parser. This also makes supporting `dynamically loaded options`_
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trivial.
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#. Cleaner: CommandLine supports enum and other types directly, meaning that
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there is less error and more security built into the library. You don't have
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to worry about whether your integral command line argument accidentally got
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assigned a value that is not valid for your enum type.
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#. Powerful: The CommandLine library supports many different types of arguments,
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from simple `boolean flags`_ to `scalars arguments`_ (`strings`_,
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`integers`_, `enums`_, `doubles`_), to `lists of arguments`_. This is
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possible because CommandLine is...
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#. Extensible: It is very simple to add a new argument type to CommandLine.
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Simply specify the parser that you want to use with the command line option
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when you declare it. `Custom parsers`_ are no problem.
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#. Labor Saving: The CommandLine library cuts down on the amount of grunt work
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that you, the user, have to do. For example, it automatically provides a
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``-help`` option that shows the available command line options for your tool.
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Additionally, it does most of the basic correctness checking for you.
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#. Capable: The CommandLine library can handle lots of different forms of
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options often found in real programs. For example, `positional`_ arguments,
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``ls`` style `grouping`_ options (to allow processing '``ls -lad``'
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naturally), ``ld`` style `prefix`_ options (to parse '``-lmalloc
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-L/usr/lib``'), and interpreter style options.
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This document will hopefully let you jump in and start using CommandLine in your
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utility quickly and painlessly. Additionally it should be a simple reference
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manual to figure out how stuff works.
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Quick Start Guide
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=================
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This section of the manual runs through a simple CommandLine'ification of a
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basic compiler tool. This is intended to show you how to jump into using the
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CommandLine library in your own program, and show you some of the cool things it
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can do.
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To start out, you need to include the CommandLine header file into your program:
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.. code-block:: c++
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#include "llvm/Support/CommandLine.h"
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Additionally, you need to add this as the first line of your main program:
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.. code-block:: c++
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int main(int argc, char **argv) {
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cl::ParseCommandLineOptions(argc, argv);
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...
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}
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... which actually parses the arguments and fills in the variable declarations.
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Now that you are ready to support command line arguments, we need to tell the
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system which ones we want, and what type of arguments they are. The CommandLine
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library uses a declarative syntax to model command line arguments with the
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global variable declarations that capture the parsed values. This means that
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for every command line option that you would like to support, there should be a
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global variable declaration to capture the result. For example, in a compiler,
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we would like to support the Unix-standard '``-o <filename>``' option to specify
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where to put the output. With the CommandLine library, this is represented like
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this:
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.. _scalars arguments:
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.. _here:
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.. code-block:: c++
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cl::opt<string> OutputFilename("o", cl::desc("Specify output filename"), cl::value_desc("filename"));
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This declares a global variable "``OutputFilename``" that is used to capture the
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result of the "``o``" argument (first parameter). We specify that this is a
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simple scalar option by using the "``cl::opt``" template (as opposed to the
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"``cl::list``" template), and tell the CommandLine library that the data
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type that we are parsing is a string.
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The second and third parameters (which are optional) are used to specify what to
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output for the "``-help``" option. In this case, we get a line that looks like
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this:
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::
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USAGE: compiler [options]
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OPTIONS:
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-help - display available options (-help-hidden for more)
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-o <filename> - Specify output filename
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Because we specified that the command line option should parse using the
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``string`` data type, the variable declared is automatically usable as a real
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string in all contexts that a normal C++ string object may be used. For
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example:
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.. code-block:: c++
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...
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std::ofstream Output(OutputFilename.c_str());
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if (Output.good()) ...
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...
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There are many different options that you can use to customize the command line
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option handling library, but the above example shows the general interface to
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these options. The options can be specified in any order, and are specified
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with helper functions like `cl::desc(...)`_, so there are no positional
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dependencies to remember. The available options are discussed in detail in the
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`Reference Guide`_.
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Continuing the example, we would like to have our compiler take an input
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filename as well as an output filename, but we do not want the input filename to
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be specified with a hyphen (ie, not ``-filename.c``). To support this style of
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argument, the CommandLine library allows for `positional`_ arguments to be
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specified for the program. These positional arguments are filled with command
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line parameters that are not in option form. We use this feature like this:
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.. code-block:: c++
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cl::opt<string> InputFilename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
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This declaration indicates that the first positional argument should be treated
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as the input filename. Here we use the `cl::init`_ option to specify an initial
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value for the command line option, which is used if the option is not specified
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(if you do not specify a `cl::init`_ modifier for an option, then the default
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constructor for the data type is used to initialize the value). Command line
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options default to being optional, so if we would like to require that the user
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always specify an input filename, we would add the `cl::Required`_ flag, and we
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could eliminate the `cl::init`_ modifier, like this:
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.. code-block:: c++
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cl::opt<string> InputFilename(cl::Positional, cl::desc("<input file>"), cl::Required);
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Again, the CommandLine library does not require the options to be specified in
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any particular order, so the above declaration is equivalent to:
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.. code-block:: c++
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cl::opt<string> InputFilename(cl::Positional, cl::Required, cl::desc("<input file>"));
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By simply adding the `cl::Required`_ flag, the CommandLine library will
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automatically issue an error if the argument is not specified, which shifts all
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of the command line option verification code out of your application into the
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library. This is just one example of how using flags can alter the default
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behaviour of the library, on a per-option basis. By adding one of the
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declarations above, the ``-help`` option synopsis is now extended to:
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::
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USAGE: compiler [options] <input file>
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OPTIONS:
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-help - display available options (-help-hidden for more)
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-o <filename> - Specify output filename
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... indicating that an input filename is expected.
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Boolean Arguments
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-----------------
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In addition to input and output filenames, we would like the compiler example to
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support three boolean flags: "``-f``" to force writing binary output to a
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terminal, "``--quiet``" to enable quiet mode, and "``-q``" for backwards
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compatibility with some of our users. We can support these by declaring options
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of boolean type like this:
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.. code-block:: c++
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cl::opt<bool> Force ("f", cl::desc("Enable binary output on terminals"));
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cl::opt<bool> Quiet ("quiet", cl::desc("Don't print informational messages"));
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cl::opt<bool> Quiet2("q", cl::desc("Don't print informational messages"), cl::Hidden);
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This does what you would expect: it declares three boolean variables
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("``Force``", "``Quiet``", and "``Quiet2``") to recognize these options. Note
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that the "``-q``" option is specified with the "`cl::Hidden`_" flag. This
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modifier prevents it from being shown by the standard "``-help``" output (note
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that it is still shown in the "``-help-hidden``" output).
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The CommandLine library uses a `different parser`_ for different data types.
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For example, in the string case, the argument passed to the option is copied
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literally into the content of the string variable... we obviously cannot do that
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in the boolean case, however, so we must use a smarter parser. In the case of
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the boolean parser, it allows no options (in which case it assigns the value of
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true to the variable), or it allows the values "``true``" or "``false``" to be
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specified, allowing any of the following inputs:
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::
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compiler -f # No value, 'Force' == true
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compiler -f=true # Value specified, 'Force' == true
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compiler -f=TRUE # Value specified, 'Force' == true
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compiler -f=FALSE # Value specified, 'Force' == false
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... you get the idea. The `bool parser`_ just turns the string values into
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boolean values, and rejects things like '``compiler -f=foo``'. Similarly, the
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`float`_, `double`_, and `int`_ parsers work like you would expect, using the
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'``strtol``' and '``strtod``' C library calls to parse the string value into the
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specified data type.
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With the declarations above, "``compiler -help``" emits this:
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::
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USAGE: compiler [options] <input file>
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OPTIONS:
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-f - Enable binary output on terminals
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-o - Override output filename
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-quiet - Don't print informational messages
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-help - display available options (-help-hidden for more)
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and "``compiler -help-hidden``" prints this:
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::
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USAGE: compiler [options] <input file>
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OPTIONS:
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-f - Enable binary output on terminals
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-o - Override output filename
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-q - Don't print informational messages
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-quiet - Don't print informational messages
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-help - display available options (-help-hidden for more)
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This brief example has shown you how to use the '`cl::opt`_' class to parse
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simple scalar command line arguments. In addition to simple scalar arguments,
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the CommandLine library also provides primitives to support CommandLine option
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`aliases`_, and `lists`_ of options.
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.. _aliases:
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Argument Aliases
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----------------
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So far, the example works well, except for the fact that we need to check the
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quiet condition like this now:
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.. code-block:: c++
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...
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if (!Quiet && !Quiet2) printInformationalMessage(...);
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...
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... which is a real pain! Instead of defining two values for the same
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condition, we can use the "`cl::alias`_" class to make the "``-q``" option an
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**alias** for the "``-quiet``" option, instead of providing a value itself:
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.. code-block:: c++
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cl::opt<bool> Force ("f", cl::desc("Overwrite output files"));
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cl::opt<bool> Quiet ("quiet", cl::desc("Don't print informational messages"));
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cl::alias QuietA("q", cl::desc("Alias for -quiet"), cl::aliasopt(Quiet));
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The third line (which is the only one we modified from above) defines a "``-q``"
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alias that updates the "``Quiet``" variable (as specified by the `cl::aliasopt`_
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modifier) whenever it is specified. Because aliases do not hold state, the only
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thing the program has to query is the ``Quiet`` variable now. Another nice
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feature of aliases is that they automatically hide themselves from the ``-help``
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output (although, again, they are still visible in the ``-help-hidden output``).
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Now the application code can simply use:
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.. code-block:: c++
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...
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if (!Quiet) printInformationalMessage(...);
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...
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... which is much nicer! The "`cl::alias`_" can be used to specify an
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alternative name for any variable type, and has many uses.
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.. _unnamed alternatives using the generic parser:
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Selecting an alternative from a set of possibilities
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----------------------------------------------------
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So far we have seen how the CommandLine library handles builtin types like
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``std::string``, ``bool`` and ``int``, but how does it handle things it doesn't
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know about, like enums or '``int*``'s?
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The answer is that it uses a table-driven generic parser (unless you specify
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your own parser, as described in the `Extension Guide`_). This parser maps
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literal strings to whatever type is required, and requires you to tell it what
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this mapping should be.
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Let's say that we would like to add four optimization levels to our optimizer,
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using the standard flags "``-g``", "``-O0``", "``-O1``", and "``-O2``". We
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could easily implement this with boolean options like above, but there are
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several problems with this strategy:
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#. A user could specify more than one of the options at a time, for example,
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"``compiler -O3 -O2``". The CommandLine library would not be able to catch
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this erroneous input for us.
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#. We would have to test 4 different variables to see which ones are set.
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#. This doesn't map to the numeric levels that we want... so we cannot easily
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see if some level >= "``-O1``" is enabled.
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To cope with these problems, we can use an enum value, and have the CommandLine
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library fill it in with the appropriate level directly, which is used like this:
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.. code-block:: c++
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enum OptLevel {
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g, O1, O2, O3
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};
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cl::opt<OptLevel> OptimizationLevel(cl::desc("Choose optimization level:"),
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cl::values(
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clEnumVal(g , "No optimizations, enable debugging"),
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clEnumVal(O1, "Enable trivial optimizations"),
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clEnumVal(O2, "Enable default optimizations"),
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clEnumVal(O3, "Enable expensive optimizations"),
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clEnumValEnd));
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...
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if (OptimizationLevel >= O2) doPartialRedundancyElimination(...);
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...
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This declaration defines a variable "``OptimizationLevel``" of the
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"``OptLevel``" enum type. This variable can be assigned any of the values that
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are listed in the declaration (Note that the declaration list must be terminated
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with the "``clEnumValEnd``" argument!). The CommandLine library enforces that
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the user can only specify one of the options, and it ensure that only valid enum
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values can be specified. The "``clEnumVal``" macros ensure that the command
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line arguments matched the enum values. With this option added, our help output
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now is:
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::
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USAGE: compiler [options] <input file>
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OPTIONS:
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Choose optimization level:
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-g - No optimizations, enable debugging
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-O1 - Enable trivial optimizations
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-O2 - Enable default optimizations
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-O3 - Enable expensive optimizations
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-f - Enable binary output on terminals
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-help - display available options (-help-hidden for more)
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-o <filename> - Specify output filename
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-quiet - Don't print informational messages
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In this case, it is sort of awkward that flag names correspond directly to enum
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names, because we probably don't want a enum definition named "``g``" in our
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program. Because of this, we can alternatively write this example like this:
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.. code-block:: c++
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enum OptLevel {
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Debug, O1, O2, O3
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};
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cl::opt<OptLevel> OptimizationLevel(cl::desc("Choose optimization level:"),
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cl::values(
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clEnumValN(Debug, "g", "No optimizations, enable debugging"),
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clEnumVal(O1 , "Enable trivial optimizations"),
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clEnumVal(O2 , "Enable default optimizations"),
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clEnumVal(O3 , "Enable expensive optimizations"),
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clEnumValEnd));
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...
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if (OptimizationLevel == Debug) outputDebugInfo(...);
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...
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By using the "``clEnumValN``" macro instead of "``clEnumVal``", we can directly
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specify the name that the flag should get. In general a direct mapping is nice,
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but sometimes you can't or don't want to preserve the mapping, which is when you
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would use it.
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Named Alternatives
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------------------
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Another useful argument form is a named alternative style. We shall use this
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style in our compiler to specify different debug levels that can be used.
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Instead of each debug level being its own switch, we want to support the
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following options, of which only one can be specified at a time:
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"``--debug-level=none``", "``--debug-level=quick``",
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"``--debug-level=detailed``". To do this, we use the exact same format as our
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optimization level flags, but we also specify an option name. For this case,
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the code looks like this:
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.. code-block:: c++
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enum DebugLev {
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nodebuginfo, quick, detailed
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};
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// Enable Debug Options to be specified on the command line
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cl::opt<DebugLev> DebugLevel("debug_level", cl::desc("Set the debugging level:"),
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cl::values(
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clEnumValN(nodebuginfo, "none", "disable debug information"),
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clEnumVal(quick, "enable quick debug information"),
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clEnumVal(detailed, "enable detailed debug information"),
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clEnumValEnd));
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This definition defines an enumerated command line variable of type "``enum
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DebugLev``", which works exactly the same way as before. The difference here is
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just the interface exposed to the user of your program and the help output by
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|
the "``-help``" option:
|
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|
|
::
|
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|
USAGE: compiler [options] <input file>
|
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OPTIONS:
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Choose optimization level:
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-g - No optimizations, enable debugging
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-O1 - Enable trivial optimizations
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-O2 - Enable default optimizations
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-O3 - Enable expensive optimizations
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-debug_level - Set the debugging level:
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=none - disable debug information
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=quick - enable quick debug information
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=detailed - enable detailed debug information
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-f - Enable binary output on terminals
|
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-help - display available options (-help-hidden for more)
|
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-o <filename> - Specify output filename
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-quiet - Don't print informational messages
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Again, the only structural difference between the debug level declaration and
|
|
the optimization level declaration is that the debug level declaration includes
|
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an option name (``"debug_level"``), which automatically changes how the library
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processes the argument. The CommandLine library supports both forms so that you
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can choose the form most appropriate for your application.
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.. _lists:
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Parsing a list of options
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|
-------------------------
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Now that we have the standard run-of-the-mill argument types out of the way,
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lets get a little wild and crazy. Lets say that we want our optimizer to accept
|
|
a **list** of optimizations to perform, allowing duplicates. For example, we
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|
might want to run: "``compiler -dce -constprop -inline -dce -strip``". In this
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|
case, the order of the arguments and the number of appearances is very
|
|
important. This is what the "``cl::list``" template is for. First, start by
|
|
defining an enum of the optimizations that you would like to perform:
|
|
|
|
.. code-block:: c++
|
|
|
|
enum Opts {
|
|
// 'inline' is a C++ keyword, so name it 'inlining'
|
|
dce, constprop, inlining, strip
|
|
};
|
|
|
|
Then define your "``cl::list``" variable:
|
|
|
|
.. code-block:: c++
|
|
|
|
cl::list<Opts> OptimizationList(cl::desc("Available Optimizations:"),
|
|
cl::values(
|
|
clEnumVal(dce , "Dead Code Elimination"),
|
|
clEnumVal(constprop , "Constant Propagation"),
|
|
clEnumValN(inlining, "inline", "Procedure Integration"),
|
|
clEnumVal(strip , "Strip Symbols"),
|
|
clEnumValEnd));
|
|
|
|
This defines a variable that is conceptually of the type
|
|
"``std::vector<enum Opts>``". Thus, you can access it with standard vector
|
|
methods:
|
|
|
|
.. code-block:: c++
|
|
|
|
for (unsigned i = 0; i != OptimizationList.size(); ++i)
|
|
switch (OptimizationList[i])
|
|
...
|
|
|
|
... to iterate through the list of options specified.
|
|
|
|
Note that the "``cl::list``" template is completely general and may be used with
|
|
any data types or other arguments that you can use with the "``cl::opt``"
|
|
template. One especially useful way to use a list is to capture all of the
|
|
positional arguments together if there may be more than one specified. In the
|
|
case of a linker, for example, the linker takes several '``.o``' files, and
|
|
needs to capture them into a list. This is naturally specified as:
|
|
|
|
.. code-block:: c++
|
|
|
|
...
|
|
cl::list<std::string> InputFilenames(cl::Positional, cl::desc("<Input files>"), cl::OneOrMore);
|
|
...
|
|
|
|
This variable works just like a "``vector<string>``" object. As such, accessing
|
|
the list is simple, just like above. In this example, we used the
|
|
`cl::OneOrMore`_ modifier to inform the CommandLine library that it is an error
|
|
if the user does not specify any ``.o`` files on our command line. Again, this
|
|
just reduces the amount of checking we have to do.
|
|
|
|
Collecting options as a set of flags
|
|
------------------------------------
|
|
|
|
Instead of collecting sets of options in a list, it is also possible to gather
|
|
information for enum values in a **bit vector**. The representation used by the
|
|
`cl::bits`_ class is an ``unsigned`` integer. An enum value is represented by a
|
|
0/1 in the enum's ordinal value bit position. 1 indicating that the enum was
|
|
specified, 0 otherwise. As each specified value is parsed, the resulting enum's
|
|
bit is set in the option's bit vector:
|
|
|
|
.. code-block:: c++
|
|
|
|
bits |= 1 << (unsigned)enum;
|
|
|
|
Options that are specified multiple times are redundant. Any instances after
|
|
the first are discarded.
|
|
|
|
Reworking the above list example, we could replace `cl::list`_ with `cl::bits`_:
|
|
|
|
.. code-block:: c++
|
|
|
|
cl::bits<Opts> OptimizationBits(cl::desc("Available Optimizations:"),
|
|
cl::values(
|
|
clEnumVal(dce , "Dead Code Elimination"),
|
|
clEnumVal(constprop , "Constant Propagation"),
|
|
clEnumValN(inlining, "inline", "Procedure Integration"),
|
|
clEnumVal(strip , "Strip Symbols"),
|
|
clEnumValEnd));
|
|
|
|
To test to see if ``constprop`` was specified, we can use the ``cl:bits::isSet``
|
|
function:
|
|
|
|
.. code-block:: c++
|
|
|
|
if (OptimizationBits.isSet(constprop)) {
|
|
...
|
|
}
|
|
|
|
It's also possible to get the raw bit vector using the ``cl::bits::getBits``
|
|
function:
|
|
|
|
.. code-block:: c++
|
|
|
|
unsigned bits = OptimizationBits.getBits();
|
|
|
|
Finally, if external storage is used, then the location specified must be of
|
|
**type** ``unsigned``. In all other ways a `cl::bits`_ option is equivalent to a
|
|
`cl::list`_ option.
|
|
|
|
.. _additional extra text:
|
|
|
|
Adding freeform text to help output
|
|
-----------------------------------
|
|
|
|
As our program grows and becomes more mature, we may decide to put summary
|
|
information about what it does into the help output. The help output is styled
|
|
to look similar to a Unix ``man`` page, providing concise information about a
|
|
program. Unix ``man`` pages, however often have a description about what the
|
|
program does. To add this to your CommandLine program, simply pass a third
|
|
argument to the `cl::ParseCommandLineOptions`_ call in main. This additional
|
|
argument is then printed as the overview information for your program, allowing
|
|
you to include any additional information that you want. For example:
|
|
|
|
.. code-block:: c++
|
|
|
|
int main(int argc, char **argv) {
|
|
cl::ParseCommandLineOptions(argc, argv, " CommandLine compiler example\n\n"
|
|
" This program blah blah blah...\n");
|
|
...
|
|
}
|
|
|
|
would yield the help output:
|
|
|
|
::
|
|
|
|
**OVERVIEW: CommandLine compiler example
|
|
|
|
This program blah blah blah...**
|
|
|
|
USAGE: compiler [options] <input file>
|
|
|
|
OPTIONS:
|
|
...
|
|
-help - display available options (-help-hidden for more)
|
|
-o <filename> - Specify output filename
|
|
|
|
.. _grouping options into categories:
|
|
|
|
Grouping options into categories
|
|
--------------------------------
|
|
|
|
If our program has a large number of options it may become difficult for users
|
|
of our tool to navigate the output of ``-help``. To alleviate this problem we
|
|
can put our options into categories. This can be done by declaring option
|
|
categories (`cl::OptionCategory`_ objects) and then placing our options into
|
|
these categories using the `cl::cat`_ option attribute. For example:
|
|
|
|
.. code-block:: c++
|
|
|
|
cl::OptionCategory StageSelectionCat("Stage Selection Options",
|
|
"These control which stages are run.");
|
|
|
|
cl::opt<bool> Preprocessor("E",cl::desc("Run preprocessor stage."),
|
|
cl::cat(StageSelectionCat));
|
|
|
|
cl::opt<bool> NoLink("c",cl::desc("Run all stages except linking."),
|
|
cl::cat(StageSelectionCat));
|
|
|
|
The output of ``-help`` will become categorized if an option category is
|
|
declared. The output looks something like ::
|
|
|
|
OVERVIEW: This is a small program to demo the LLVM CommandLine API
|
|
USAGE: Sample [options]
|
|
|
|
OPTIONS:
|
|
|
|
General options:
|
|
|
|
-help - Display available options (-help-hidden for more)
|
|
-help-list - Display list of available options (-help-list-hidden for more)
|
|
|
|
|
|
Stage Selection Options:
|
|
These control which stages are run.
|
|
|
|
-E - Run preprocessor stage.
|
|
-c - Run all stages except linking.
|
|
|
|
In addition to the behaviour of ``-help`` changing when an option category is
|
|
declared, the command line option ``-help-list`` becomes visible which will
|
|
print the command line options as uncategorized list.
|
|
|
|
Note that Options that are not explicitly categorized will be placed in the
|
|
``cl::GeneralCategory`` category.
|
|
|
|
.. _Reference Guide:
|
|
|
|
Reference Guide
|
|
===============
|
|
|
|
Now that you know the basics of how to use the CommandLine library, this section
|
|
will give you the detailed information you need to tune how command line options
|
|
work, as well as information on more "advanced" command line option processing
|
|
capabilities.
|
|
|
|
.. _positional:
|
|
.. _positional argument:
|
|
.. _Positional Arguments:
|
|
.. _Positional arguments section:
|
|
.. _positional options:
|
|
|
|
Positional Arguments
|
|
--------------------
|
|
|
|
Positional arguments are those arguments that are not named, and are not
|
|
specified with a hyphen. Positional arguments should be used when an option is
|
|
specified by its position alone. For example, the standard Unix ``grep`` tool
|
|
takes a regular expression argument, and an optional filename to search through
|
|
(which defaults to standard input if a filename is not specified). Using the
|
|
CommandLine library, this would be specified as:
|
|
|
|
.. code-block:: c++
|
|
|
|
cl::opt<string> Regex (cl::Positional, cl::desc("<regular expression>"), cl::Required);
|
|
cl::opt<string> Filename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
|
|
|
|
Given these two option declarations, the ``-help`` output for our grep
|
|
replacement would look like this:
|
|
|
|
::
|
|
|
|
USAGE: spiffygrep [options] <regular expression> <input file>
|
|
|
|
OPTIONS:
|
|
-help - display available options (-help-hidden for more)
|
|
|
|
... and the resultant program could be used just like the standard ``grep``
|
|
tool.
|
|
|
|
Positional arguments are sorted by their order of construction. This means that
|
|
command line options will be ordered according to how they are listed in a .cpp
|
|
file, but will not have an ordering defined if the positional arguments are
|
|
defined in multiple .cpp files. The fix for this problem is simply to define
|
|
all of your positional arguments in one .cpp file.
|
|
|
|
Specifying positional options with hyphens
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Sometimes you may want to specify a value to your positional argument that
|
|
starts with a hyphen (for example, searching for '``-foo``' in a file). At
|
|
first, you will have trouble doing this, because it will try to find an argument
|
|
named '``-foo``', and will fail (and single quotes will not save you). Note
|
|
that the system ``grep`` has the same problem:
|
|
|
|
::
|
|
|
|
$ spiffygrep '-foo' test.txt
|
|
Unknown command line argument '-foo'. Try: spiffygrep -help'
|
|
|
|
$ grep '-foo' test.txt
|
|
grep: illegal option -- f
|
|
grep: illegal option -- o
|
|
grep: illegal option -- o
|
|
Usage: grep -hblcnsviw pattern file . . .
|
|
|
|
The solution for this problem is the same for both your tool and the system
|
|
version: use the '``--``' marker. When the user specifies '``--``' on the
|
|
command line, it is telling the program that all options after the '``--``'
|
|
should be treated as positional arguments, not options. Thus, we can use it
|
|
like this:
|
|
|
|
::
|
|
|
|
$ spiffygrep -- -foo test.txt
|
|
...output...
|
|
|
|
Determining absolute position with getPosition()
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Sometimes an option can affect or modify the meaning of another option. For
|
|
example, consider ``gcc``'s ``-x LANG`` option. This tells ``gcc`` to ignore the
|
|
suffix of subsequent positional arguments and force the file to be interpreted
|
|
as if it contained source code in language ``LANG``. In order to handle this
|
|
properly, you need to know the absolute position of each argument, especially
|
|
those in lists, so their interaction(s) can be applied correctly. This is also
|
|
useful for options like ``-llibname`` which is actually a positional argument
|
|
that starts with a dash.
|
|
|
|
So, generally, the problem is that you have two ``cl::list`` variables that
|
|
interact in some way. To ensure the correct interaction, you can use the
|
|
``cl::list::getPosition(optnum)`` method. This method returns the absolute
|
|
position (as found on the command line) of the ``optnum`` item in the
|
|
``cl::list``.
|
|
|
|
The idiom for usage is like this:
|
|
|
|
.. code-block:: c++
|
|
|
|
static cl::list<std::string> Files(cl::Positional, cl::OneOrMore);
|
|
static cl::list<std::string> Libraries("l", cl::ZeroOrMore);
|
|
|
|
int main(int argc, char**argv) {
|
|
// ...
|
|
std::vector<std::string>::iterator fileIt = Files.begin();
|
|
std::vector<std::string>::iterator libIt = Libraries.begin();
|
|
unsigned libPos = 0, filePos = 0;
|
|
while ( 1 ) {
|
|
if ( libIt != Libraries.end() )
|
|
libPos = Libraries.getPosition( libIt - Libraries.begin() );
|
|
else
|
|
libPos = 0;
|
|
if ( fileIt != Files.end() )
|
|
filePos = Files.getPosition( fileIt - Files.begin() );
|
|
else
|
|
filePos = 0;
|
|
|
|
if ( filePos != 0 && (libPos == 0 || filePos < libPos) ) {
|
|
// Source File Is next
|
|
++fileIt;
|
|
}
|
|
else if ( libPos != 0 && (filePos == 0 || libPos < filePos) ) {
|
|
// Library is next
|
|
++libIt;
|
|
}
|
|
else
|
|
break; // we're done with the list
|
|
}
|
|
}
|
|
|
|
Note that, for compatibility reasons, the ``cl::opt`` also supports an
|
|
``unsigned getPosition()`` option that will provide the absolute position of
|
|
that option. You can apply the same approach as above with a ``cl::opt`` and a
|
|
``cl::list`` option as you can with two lists.
|
|
|
|
.. _interpreter style options:
|
|
.. _cl::ConsumeAfter:
|
|
.. _this section for more information:
|
|
|
|
The ``cl::ConsumeAfter`` modifier
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::ConsumeAfter`` `formatting option`_ is used to construct programs that
|
|
use "interpreter style" option processing. With this style of option
|
|
processing, all arguments specified after the last positional argument are
|
|
treated as special interpreter arguments that are not interpreted by the command
|
|
line argument.
|
|
|
|
As a concrete example, lets say we are developing a replacement for the standard
|
|
Unix Bourne shell (``/bin/sh``). To run ``/bin/sh``, first you specify options
|
|
to the shell itself (like ``-x`` which turns on trace output), then you specify
|
|
the name of the script to run, then you specify arguments to the script. These
|
|
arguments to the script are parsed by the Bourne shell command line option
|
|
processor, but are not interpreted as options to the shell itself. Using the
|
|
CommandLine library, we would specify this as:
|
|
|
|
.. code-block:: c++
|
|
|
|
cl::opt<string> Script(cl::Positional, cl::desc("<input script>"), cl::init("-"));
|
|
cl::list<string> Argv(cl::ConsumeAfter, cl::desc("<program arguments>..."));
|
|
cl::opt<bool> Trace("x", cl::desc("Enable trace output"));
|
|
|
|
which automatically provides the help output:
|
|
|
|
::
|
|
|
|
USAGE: spiffysh [options] <input script> <program arguments>...
|
|
|
|
OPTIONS:
|
|
-help - display available options (-help-hidden for more)
|
|
-x - Enable trace output
|
|
|
|
At runtime, if we run our new shell replacement as ```spiffysh -x test.sh -a -x
|
|
-y bar``', the ``Trace`` variable will be set to true, the ``Script`` variable
|
|
will be set to "``test.sh``", and the ``Argv`` list will contain ``["-a", "-x",
|
|
"-y", "bar"]``, because they were specified after the last positional argument
|
|
(which is the script name).
|
|
|
|
There are several limitations to when ``cl::ConsumeAfter`` options can be
|
|
specified. For example, only one ``cl::ConsumeAfter`` can be specified per
|
|
program, there must be at least one `positional argument`_ specified, there must
|
|
not be any `cl::list`_ positional arguments, and the ``cl::ConsumeAfter`` option
|
|
should be a `cl::list`_ option.
|
|
|
|
.. _can be changed:
|
|
.. _Internal vs External Storage:
|
|
|
|
Internal vs External Storage
|
|
----------------------------
|
|
|
|
By default, all command line options automatically hold the value that they
|
|
parse from the command line. This is very convenient in the common case,
|
|
especially when combined with the ability to define command line options in the
|
|
files that use them. This is called the internal storage model.
|
|
|
|
Sometimes, however, it is nice to separate the command line option processing
|
|
code from the storage of the value parsed. For example, lets say that we have a
|
|
'``-debug``' option that we would like to use to enable debug information across
|
|
the entire body of our program. In this case, the boolean value controlling the
|
|
debug code should be globally accessible (in a header file, for example) yet the
|
|
command line option processing code should not be exposed to all of these
|
|
clients (requiring lots of .cpp files to ``#include CommandLine.h``).
|
|
|
|
To do this, set up your .h file with your option, like this for example:
|
|
|
|
.. code-block:: c++
|
|
|
|
// DebugFlag.h - Get access to the '-debug' command line option
|
|
//
|
|
|
|
// DebugFlag - This boolean is set to true if the '-debug' command line option
|
|
// is specified. This should probably not be referenced directly, instead, use
|
|
// the DEBUG macro below.
|
|
//
|
|
extern bool DebugFlag;
|
|
|
|
// DEBUG macro - This macro should be used by code to emit debug information.
|
|
// In the '-debug' option is specified on the command line, and if this is a
|
|
// debug build, then the code specified as the option to the macro will be
|
|
// executed. Otherwise it will not be.
|
|
#ifdef NDEBUG
|
|
#define DEBUG(X)
|
|
#else
|
|
#define DEBUG(X) do { if (DebugFlag) { X; } } while (0)
|
|
#endif
|
|
|
|
This allows clients to blissfully use the ``DEBUG()`` macro, or the
|
|
``DebugFlag`` explicitly if they want to. Now we just need to be able to set
|
|
the ``DebugFlag`` boolean when the option is set. To do this, we pass an
|
|
additional argument to our command line argument processor, and we specify where
|
|
to fill in with the `cl::location`_ attribute:
|
|
|
|
.. code-block:: c++
|
|
|
|
bool DebugFlag; // the actual value
|
|
static cl::opt<bool, true> // The parser
|
|
Debug("debug", cl::desc("Enable debug output"), cl::Hidden, cl::location(DebugFlag));
|
|
|
|
In the above example, we specify "``true``" as the second argument to the
|
|
`cl::opt`_ template, indicating that the template should not maintain a copy of
|
|
the value itself. In addition to this, we specify the `cl::location`_
|
|
attribute, so that ``DebugFlag`` is automatically set.
|
|
|
|
Option Attributes
|
|
-----------------
|
|
|
|
This section describes the basic attributes that you can specify on options.
|
|
|
|
* The option name attribute (which is required for all options, except
|
|
`positional options`_) specifies what the option name is. This option is
|
|
specified in simple double quotes:
|
|
|
|
.. code-block:: c++
|
|
|
|
cl::opt<bool> Quiet("quiet");
|
|
|
|
.. _cl::desc(...):
|
|
|
|
* The **cl::desc** attribute specifies a description for the option to be
|
|
shown in the ``-help`` output for the program. This attribute supports
|
|
multi-line descriptions with lines separated by '\n'.
|
|
|
|
.. _cl::value_desc:
|
|
|
|
* The **cl::value_desc** attribute specifies a string that can be used to
|
|
fine tune the ``-help`` output for a command line option. Look `here`_ for an
|
|
example.
|
|
|
|
.. _cl::init:
|
|
|
|
* The **cl::init** attribute specifies an initial value for a `scalar`_
|
|
option. If this attribute is not specified then the command line option value
|
|
defaults to the value created by the default constructor for the
|
|
type.
|
|
|
|
.. warning::
|
|
|
|
If you specify both **cl::init** and **cl::location** for an option, you
|
|
must specify **cl::location** first, so that when the command-line parser
|
|
sees **cl::init**, it knows where to put the initial value. (You will get an
|
|
error at runtime if you don't put them in the right order.)
|
|
|
|
.. _cl::location:
|
|
|
|
* The **cl::location** attribute where to store the value for a parsed command
|
|
line option if using external storage. See the section on `Internal vs
|
|
External Storage`_ for more information.
|
|
|
|
.. _cl::aliasopt:
|
|
|
|
* The **cl::aliasopt** attribute specifies which option a `cl::alias`_ option is
|
|
an alias for.
|
|
|
|
.. _cl::values:
|
|
|
|
* The **cl::values** attribute specifies the string-to-value mapping to be used
|
|
by the generic parser. It takes a **clEnumValEnd terminated** list of
|
|
(option, value, description) triplets that specify the option name, the value
|
|
mapped to, and the description shown in the ``-help`` for the tool. Because
|
|
the generic parser is used most frequently with enum values, two macros are
|
|
often useful:
|
|
|
|
#. The **clEnumVal** macro is used as a nice simple way to specify a triplet
|
|
for an enum. This macro automatically makes the option name be the same as
|
|
the enum name. The first option to the macro is the enum, the second is
|
|
the description for the command line option.
|
|
|
|
#. The **clEnumValN** macro is used to specify macro options where the option
|
|
name doesn't equal the enum name. For this macro, the first argument is
|
|
the enum value, the second is the flag name, and the second is the
|
|
description.
|
|
|
|
You will get a compile time error if you try to use cl::values with a parser
|
|
that does not support it.
|
|
|
|
.. _cl::multi_val:
|
|
|
|
* The **cl::multi_val** attribute specifies that this option takes has multiple
|
|
values (example: ``-sectalign segname sectname sectvalue``). This attribute
|
|
takes one unsigned argument - the number of values for the option. This
|
|
attribute is valid only on ``cl::list`` options (and will fail with compile
|
|
error if you try to use it with other option types). It is allowed to use all
|
|
of the usual modifiers on multi-valued options (besides
|
|
``cl::ValueDisallowed``, obviously).
|
|
|
|
.. _cl::cat:
|
|
|
|
* The **cl::cat** attribute specifies the option category that the option
|
|
belongs to. The category should be a `cl::OptionCategory`_ object.
|
|
|
|
Option Modifiers
|
|
----------------
|
|
|
|
Option modifiers are the flags and expressions that you pass into the
|
|
constructors for `cl::opt`_ and `cl::list`_. These modifiers give you the
|
|
ability to tweak how options are parsed and how ``-help`` output is generated to
|
|
fit your application well.
|
|
|
|
These options fall into five main categories:
|
|
|
|
#. Hiding an option from ``-help`` output
|
|
|
|
#. Controlling the number of occurrences required and allowed
|
|
|
|
#. Controlling whether or not a value must be specified
|
|
|
|
#. Controlling other formatting options
|
|
|
|
#. Miscellaneous option modifiers
|
|
|
|
It is not possible to specify two options from the same category (you'll get a
|
|
runtime error) to a single option, except for options in the miscellaneous
|
|
category. The CommandLine library specifies defaults for all of these settings
|
|
that are the most useful in practice and the most common, which mean that you
|
|
usually shouldn't have to worry about these.
|
|
|
|
Hiding an option from ``-help`` output
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::NotHidden``, ``cl::Hidden``, and ``cl::ReallyHidden`` modifiers are
|
|
used to control whether or not an option appears in the ``-help`` and
|
|
``-help-hidden`` output for the compiled program:
|
|
|
|
.. _cl::NotHidden:
|
|
|
|
* The **cl::NotHidden** modifier (which is the default for `cl::opt`_ and
|
|
`cl::list`_ options) indicates the option is to appear in both help
|
|
listings.
|
|
|
|
.. _cl::Hidden:
|
|
|
|
* The **cl::Hidden** modifier (which is the default for `cl::alias`_ options)
|
|
indicates that the option should not appear in the ``-help`` output, but
|
|
should appear in the ``-help-hidden`` output.
|
|
|
|
.. _cl::ReallyHidden:
|
|
|
|
* The **cl::ReallyHidden** modifier indicates that the option should not appear
|
|
in any help output.
|
|
|
|
Controlling the number of occurrences required and allowed
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
This group of options is used to control how many time an option is allowed (or
|
|
required) to be specified on the command line of your program. Specifying a
|
|
value for this setting allows the CommandLine library to do error checking for
|
|
you.
|
|
|
|
The allowed values for this option group are:
|
|
|
|
.. _cl::Optional:
|
|
|
|
* The **cl::Optional** modifier (which is the default for the `cl::opt`_ and
|
|
`cl::alias`_ classes) indicates that your program will allow either zero or
|
|
one occurrence of the option to be specified.
|
|
|
|
.. _cl::ZeroOrMore:
|
|
|
|
* The **cl::ZeroOrMore** modifier (which is the default for the `cl::list`_
|
|
class) indicates that your program will allow the option to be specified zero
|
|
or more times.
|
|
|
|
.. _cl::Required:
|
|
|
|
* The **cl::Required** modifier indicates that the specified option must be
|
|
specified exactly one time.
|
|
|
|
.. _cl::OneOrMore:
|
|
|
|
* The **cl::OneOrMore** modifier indicates that the option must be specified at
|
|
least one time.
|
|
|
|
* The **cl::ConsumeAfter** modifier is described in the `Positional arguments
|
|
section`_.
|
|
|
|
If an option is not specified, then the value of the option is equal to the
|
|
value specified by the `cl::init`_ attribute. If the ``cl::init`` attribute is
|
|
not specified, the option value is initialized with the default constructor for
|
|
the data type.
|
|
|
|
If an option is specified multiple times for an option of the `cl::opt`_ class,
|
|
only the last value will be retained.
|
|
|
|
Controlling whether or not a value must be specified
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
This group of options is used to control whether or not the option allows a
|
|
value to be present. In the case of the CommandLine library, a value is either
|
|
specified with an equal sign (e.g. '``-index-depth=17``') or as a trailing
|
|
string (e.g. '``-o a.out``').
|
|
|
|
The allowed values for this option group are:
|
|
|
|
.. _cl::ValueOptional:
|
|
|
|
* The **cl::ValueOptional** modifier (which is the default for ``bool`` typed
|
|
options) specifies that it is acceptable to have a value, or not. A boolean
|
|
argument can be enabled just by appearing on the command line, or it can have
|
|
an explicit '``-foo=true``'. If an option is specified with this mode, it is
|
|
illegal for the value to be provided without the equal sign. Therefore
|
|
'``-foo true``' is illegal. To get this behavior, you must use
|
|
the `cl::ValueRequired`_ modifier.
|
|
|
|
.. _cl::ValueRequired:
|
|
|
|
* The **cl::ValueRequired** modifier (which is the default for all other types
|
|
except for `unnamed alternatives using the generic parser`_) specifies that a
|
|
value must be provided. This mode informs the command line library that if an
|
|
option is not provides with an equal sign, that the next argument provided
|
|
must be the value. This allows things like '``-o a.out``' to work.
|
|
|
|
.. _cl::ValueDisallowed:
|
|
|
|
* The **cl::ValueDisallowed** modifier (which is the default for `unnamed
|
|
alternatives using the generic parser`_) indicates that it is a runtime error
|
|
for the user to specify a value. This can be provided to disallow users from
|
|
providing options to boolean options (like '``-foo=true``').
|
|
|
|
In general, the default values for this option group work just like you would
|
|
want them to. As mentioned above, you can specify the `cl::ValueDisallowed`_
|
|
modifier to a boolean argument to restrict your command line parser. These
|
|
options are mostly useful when `extending the library`_.
|
|
|
|
.. _formatting option:
|
|
|
|
Controlling other formatting options
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The formatting option group is used to specify that the command line option has
|
|
special abilities and is otherwise different from other command line arguments.
|
|
As usual, you can only specify one of these arguments at most.
|
|
|
|
.. _cl::NormalFormatting:
|
|
|
|
* The **cl::NormalFormatting** modifier (which is the default all options)
|
|
specifies that this option is "normal".
|
|
|
|
.. _cl::Positional:
|
|
|
|
* The **cl::Positional** modifier specifies that this is a positional argument
|
|
that does not have a command line option associated with it. See the
|
|
`Positional Arguments`_ section for more information.
|
|
|
|
* The **cl::ConsumeAfter** modifier specifies that this option is used to
|
|
capture "interpreter style" arguments. See `this section for more
|
|
information`_.
|
|
|
|
.. _prefix:
|
|
.. _cl::Prefix:
|
|
|
|
* The **cl::Prefix** modifier specifies that this option prefixes its value.
|
|
With 'Prefix' options, the equal sign does not separate the value from the
|
|
option name specified. Instead, the value is everything after the prefix,
|
|
including any equal sign if present. This is useful for processing odd
|
|
arguments like ``-lmalloc`` and ``-L/usr/lib`` in a linker tool or
|
|
``-DNAME=value`` in a compiler tool. Here, the '``l``', '``D``' and '``L``'
|
|
options are normal string (or list) options, that have the **cl::Prefix**
|
|
modifier added to allow the CommandLine library to recognize them. Note that
|
|
**cl::Prefix** options must not have the **cl::ValueDisallowed** modifier
|
|
specified.
|
|
|
|
.. _grouping:
|
|
.. _cl::Grouping:
|
|
|
|
* The **cl::Grouping** modifier is used to implement Unix-style tools (like
|
|
``ls``) that have lots of single letter arguments, but only require a single
|
|
dash. For example, the '``ls -labF``' command actually enables four different
|
|
options, all of which are single letters. Note that **cl::Grouping** options
|
|
cannot have values.
|
|
|
|
The CommandLine library does not restrict how you use the **cl::Prefix** or
|
|
**cl::Grouping** modifiers, but it is possible to specify ambiguous argument
|
|
settings. Thus, it is possible to have multiple letter options that are prefix
|
|
or grouping options, and they will still work as designed.
|
|
|
|
To do this, the CommandLine library uses a greedy algorithm to parse the input
|
|
option into (potentially multiple) prefix and grouping options. The strategy
|
|
basically looks like this:
|
|
|
|
::
|
|
|
|
parse(string OrigInput) {
|
|
|
|
1. string input = OrigInput;
|
|
2. if (isOption(input)) return getOption(input).parse(); // Normal option
|
|
3. while (!isOption(input) && !input.empty()) input.pop_back(); // Remove the last letter
|
|
4. if (input.empty()) return error(); // No matching option
|
|
5. if (getOption(input).isPrefix())
|
|
return getOption(input).parse(input);
|
|
6. while (!input.empty()) { // Must be grouping options
|
|
getOption(input).parse();
|
|
OrigInput.erase(OrigInput.begin(), OrigInput.begin()+input.length());
|
|
input = OrigInput;
|
|
while (!isOption(input) && !input.empty()) input.pop_back();
|
|
}
|
|
7. if (!OrigInput.empty()) error();
|
|
|
|
}
|
|
|
|
Miscellaneous option modifiers
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The miscellaneous option modifiers are the only flags where you can specify more
|
|
than one flag from the set: they are not mutually exclusive. These flags
|
|
specify boolean properties that modify the option.
|
|
|
|
.. _cl::CommaSeparated:
|
|
|
|
* The **cl::CommaSeparated** modifier indicates that any commas specified for an
|
|
option's value should be used to split the value up into multiple values for
|
|
the option. For example, these two options are equivalent when
|
|
``cl::CommaSeparated`` is specified: "``-foo=a -foo=b -foo=c``" and
|
|
"``-foo=a,b,c``". This option only makes sense to be used in a case where the
|
|
option is allowed to accept one or more values (i.e. it is a `cl::list`_
|
|
option).
|
|
|
|
.. _cl::PositionalEatsArgs:
|
|
|
|
* The **cl::PositionalEatsArgs** modifier (which only applies to positional
|
|
arguments, and only makes sense for lists) indicates that positional argument
|
|
should consume any strings after it (including strings that start with a "-")
|
|
up until another recognized positional argument. For example, if you have two
|
|
"eating" positional arguments, "``pos1``" and "``pos2``", the string "``-pos1
|
|
-foo -bar baz -pos2 -bork``" would cause the "``-foo -bar -baz``" strings to
|
|
be applied to the "``-pos1``" option and the "``-bork``" string to be applied
|
|
to the "``-pos2``" option.
|
|
|
|
.. _cl::Sink:
|
|
|
|
* The **cl::Sink** modifier is used to handle unknown options. If there is at
|
|
least one option with ``cl::Sink`` modifier specified, the parser passes
|
|
unrecognized option strings to it as values instead of signaling an error. As
|
|
with ``cl::CommaSeparated``, this modifier only makes sense with a `cl::list`_
|
|
option.
|
|
|
|
So far, these are the only three miscellaneous option modifiers.
|
|
|
|
.. _response files:
|
|
|
|
Response files
|
|
^^^^^^^^^^^^^^
|
|
|
|
Some systems, such as certain variants of Microsoft Windows and some older
|
|
Unices have a relatively low limit on command-line length. It is therefore
|
|
customary to use the so-called 'response files' to circumvent this
|
|
restriction. These files are mentioned on the command-line (using the "@file")
|
|
syntax. The program reads these files and inserts the contents into argv,
|
|
thereby working around the command-line length limits. Response files are
|
|
enabled by an optional fourth argument to `cl::ParseEnvironmentOptions`_ and
|
|
`cl::ParseCommandLineOptions`_.
|
|
|
|
Top-Level Classes and Functions
|
|
-------------------------------
|
|
|
|
Despite all of the built-in flexibility, the CommandLine option library really
|
|
only consists of one function `cl::ParseCommandLineOptions`_) and three main
|
|
classes: `cl::opt`_, `cl::list`_, and `cl::alias`_. This section describes
|
|
these three classes in detail.
|
|
|
|
.. _cl::getRegisteredOptions:
|
|
|
|
The ``cl::getRegisteredOptions`` function
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::getRegisteredOptions`` function is designed to give a programmer
|
|
access to declared non positional command line options so that how they appear
|
|
in ``-help`` can be modified prior to calling `cl::ParseCommandLineOptions`_.
|
|
Note this method should not be called during any static initialisation because
|
|
it cannot be guaranteed that all options will have been initialised. Hence it
|
|
should be called from ``main``.
|
|
|
|
This function can be used to gain access to options declared in libraries that
|
|
the tool writter may not have direct access to.
|
|
|
|
The function retrieves a :ref:`StringMap <dss_stringmap>` that maps the option
|
|
string (e.g. ``-help``) to an ``Option*``.
|
|
|
|
Here is an example of how the function could be used:
|
|
|
|
.. code-block:: c++
|
|
|
|
using namespace llvm;
|
|
int main(int argc, char **argv) {
|
|
cl::OptionCategory AnotherCategory("Some options");
|
|
|
|
StringMap<cl::Option*> Map;
|
|
cl::getRegisteredOptions(Map);
|
|
|
|
//Unhide useful option and put it in a different category
|
|
assert(Map.count("print-all-options") > 0);
|
|
Map["print-all-options"]->setHiddenFlag(cl::NotHidden);
|
|
Map["print-all-options"]->setCategory(AnotherCategory);
|
|
|
|
//Hide an option we don't want to see
|
|
assert(Map.count("enable-no-infs-fp-math") > 0);
|
|
Map["enable-no-infs-fp-math"]->setHiddenFlag(cl::Hidden);
|
|
|
|
//Change --version to --show-version
|
|
assert(Map.count("version") > 0);
|
|
Map["version"]->setArgStr("show-version");
|
|
|
|
//Change --help description
|
|
assert(Map.count("help") > 0);
|
|
Map["help"]->setDescription("Shows help");
|
|
|
|
cl::ParseCommandLineOptions(argc, argv, "This is a small program to demo the LLVM CommandLine API");
|
|
...
|
|
}
|
|
|
|
|
|
.. _cl::ParseCommandLineOptions:
|
|
|
|
The ``cl::ParseCommandLineOptions`` function
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::ParseCommandLineOptions`` function is designed to be called directly
|
|
from ``main``, and is used to fill in the values of all of the command line
|
|
option variables once ``argc`` and ``argv`` are available.
|
|
|
|
The ``cl::ParseCommandLineOptions`` function requires two parameters (``argc``
|
|
and ``argv``), but may also take an optional third parameter which holds
|
|
`additional extra text`_ to emit when the ``-help`` option is invoked, and a
|
|
fourth boolean parameter that enables `response files`_.
|
|
|
|
.. _cl::ParseEnvironmentOptions:
|
|
|
|
The ``cl::ParseEnvironmentOptions`` function
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::ParseEnvironmentOptions`` function has mostly the same effects as
|
|
`cl::ParseCommandLineOptions`_, except that it is designed to take values for
|
|
options from an environment variable, for those cases in which reading the
|
|
command line is not convenient or desired. It fills in the values of all the
|
|
command line option variables just like `cl::ParseCommandLineOptions`_ does.
|
|
|
|
It takes four parameters: the name of the program (since ``argv`` may not be
|
|
available, it can't just look in ``argv[0]``), the name of the environment
|
|
variable to examine, the optional `additional extra text`_ to emit when the
|
|
``-help`` option is invoked, and the boolean switch that controls whether
|
|
`response files`_ should be read.
|
|
|
|
``cl::ParseEnvironmentOptions`` will break the environment variable's value up
|
|
into words and then process them using `cl::ParseCommandLineOptions`_.
|
|
**Note:** Currently ``cl::ParseEnvironmentOptions`` does not support quoting, so
|
|
an environment variable containing ``-option "foo bar"`` will be parsed as three
|
|
words, ``-option``, ``"foo``, and ``bar"``, which is different from what you
|
|
would get from the shell with the same input.
|
|
|
|
The ``cl::SetVersionPrinter`` function
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::SetVersionPrinter`` function is designed to be called directly from
|
|
``main`` and *before* ``cl::ParseCommandLineOptions``. Its use is optional. It
|
|
simply arranges for a function to be called in response to the ``--version``
|
|
option instead of having the ``CommandLine`` library print out the usual version
|
|
string for LLVM. This is useful for programs that are not part of LLVM but wish
|
|
to use the ``CommandLine`` facilities. Such programs should just define a small
|
|
function that takes no arguments and returns ``void`` and that prints out
|
|
whatever version information is appropriate for the program. Pass the address of
|
|
that function to ``cl::SetVersionPrinter`` to arrange for it to be called when
|
|
the ``--version`` option is given by the user.
|
|
|
|
.. _cl::opt:
|
|
.. _scalar:
|
|
|
|
The ``cl::opt`` class
|
|
^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::opt`` class is the class used to represent scalar command line
|
|
options, and is the one used most of the time. It is a templated class which
|
|
can take up to three arguments (all except for the first have default values
|
|
though):
|
|
|
|
.. code-block:: c++
|
|
|
|
namespace cl {
|
|
template <class DataType, bool ExternalStorage = false,
|
|
class ParserClass = parser<DataType> >
|
|
class opt;
|
|
}
|
|
|
|
The first template argument specifies what underlying data type the command line
|
|
argument is, and is used to select a default parser implementation. The second
|
|
template argument is used to specify whether the option should contain the
|
|
storage for the option (the default) or whether external storage should be used
|
|
to contain the value parsed for the option (see `Internal vs External Storage`_
|
|
for more information).
|
|
|
|
The third template argument specifies which parser to use. The default value
|
|
selects an instantiation of the ``parser`` class based on the underlying data
|
|
type of the option. In general, this default works well for most applications,
|
|
so this option is only used when using a `custom parser`_.
|
|
|
|
.. _lists of arguments:
|
|
.. _cl::list:
|
|
|
|
The ``cl::list`` class
|
|
^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::list`` class is the class used to represent a list of command line
|
|
options. It too is a templated class which can take up to three arguments:
|
|
|
|
.. code-block:: c++
|
|
|
|
namespace cl {
|
|
template <class DataType, class Storage = bool,
|
|
class ParserClass = parser<DataType> >
|
|
class list;
|
|
}
|
|
|
|
This class works the exact same as the `cl::opt`_ class, except that the second
|
|
argument is the **type** of the external storage, not a boolean value. For this
|
|
class, the marker type '``bool``' is used to indicate that internal storage
|
|
should be used.
|
|
|
|
.. _cl::bits:
|
|
|
|
The ``cl::bits`` class
|
|
^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::bits`` class is the class used to represent a list of command line
|
|
options in the form of a bit vector. It is also a templated class which can
|
|
take up to three arguments:
|
|
|
|
.. code-block:: c++
|
|
|
|
namespace cl {
|
|
template <class DataType, class Storage = bool,
|
|
class ParserClass = parser<DataType> >
|
|
class bits;
|
|
}
|
|
|
|
This class works the exact same as the `cl::list`_ class, except that the second
|
|
argument must be of **type** ``unsigned`` if external storage is used.
|
|
|
|
.. _cl::alias:
|
|
|
|
The ``cl::alias`` class
|
|
^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::alias`` class is a nontemplated class that is used to form aliases for
|
|
other arguments.
|
|
|
|
.. code-block:: c++
|
|
|
|
namespace cl {
|
|
class alias;
|
|
}
|
|
|
|
The `cl::aliasopt`_ attribute should be used to specify which option this is an
|
|
alias for. Alias arguments default to being `cl::Hidden`_, and use the aliased
|
|
options parser to do the conversion from string to data.
|
|
|
|
.. _cl::extrahelp:
|
|
|
|
The ``cl::extrahelp`` class
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::extrahelp`` class is a nontemplated class that allows extra help text
|
|
to be printed out for the ``-help`` option.
|
|
|
|
.. code-block:: c++
|
|
|
|
namespace cl {
|
|
struct extrahelp;
|
|
}
|
|
|
|
To use the extrahelp, simply construct one with a ``const char*`` parameter to
|
|
the constructor. The text passed to the constructor will be printed at the
|
|
bottom of the help message, verbatim. Note that multiple ``cl::extrahelp``
|
|
**can** be used, but this practice is discouraged. If your tool needs to print
|
|
additional help information, put all that help into a single ``cl::extrahelp``
|
|
instance.
|
|
|
|
For example:
|
|
|
|
.. code-block:: c++
|
|
|
|
cl::extrahelp("\nADDITIONAL HELP:\n\n This is the extra help\n");
|
|
|
|
.. _cl::OptionCategory:
|
|
|
|
The ``cl::OptionCategory`` class
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
The ``cl::OptionCategory`` class is a simple class for declaring
|
|
option categories.
|
|
|
|
.. code-block:: c++
|
|
|
|
namespace cl {
|
|
class OptionCategory;
|
|
}
|
|
|
|
An option category must have a name and optionally a description which are
|
|
passed to the constructor as ``const char*``.
|
|
|
|
Note that declaring an option category and associating it with an option before
|
|
parsing options (e.g. statically) will change the output of ``-help`` from
|
|
uncategorized to categorized. If an option category is declared but not
|
|
associated with an option then it will be hidden from the output of ``-help``
|
|
but will be shown in the output of ``-help-hidden``.
|
|
|
|
.. _different parser:
|
|
.. _discussed previously:
|
|
|
|
Builtin parsers
|
|
---------------
|
|
|
|
Parsers control how the string value taken from the command line is translated
|
|
into a typed value, suitable for use in a C++ program. By default, the
|
|
CommandLine library uses an instance of ``parser<type>`` if the command line
|
|
option specifies that it uses values of type '``type``'. Because of this,
|
|
custom option processing is specified with specializations of the '``parser``'
|
|
class.
|
|
|
|
The CommandLine library provides the following builtin parser specializations,
|
|
which are sufficient for most applications. It can, however, also be extended to
|
|
work with new data types and new ways of interpreting the same data. See the
|
|
`Writing a Custom Parser`_ for more details on this type of library extension.
|
|
|
|
.. _enums:
|
|
.. _cl::parser:
|
|
|
|
* The generic ``parser<t>`` parser can be used to map strings values to any data
|
|
type, through the use of the `cl::values`_ property, which specifies the
|
|
mapping information. The most common use of this parser is for parsing enum
|
|
values, which allows you to use the CommandLine library for all of the error
|
|
checking to make sure that only valid enum values are specified (as opposed to
|
|
accepting arbitrary strings). Despite this, however, the generic parser class
|
|
can be used for any data type.
|
|
|
|
.. _boolean flags:
|
|
.. _bool parser:
|
|
|
|
* The **parser<bool> specialization** is used to convert boolean strings to a
|
|
boolean value. Currently accepted strings are "``true``", "``TRUE``",
|
|
"``True``", "``1``", "``false``", "``FALSE``", "``False``", and "``0``".
|
|
|
|
* The **parser<boolOrDefault> specialization** is used for cases where the value
|
|
is boolean, but we also need to know whether the option was specified at all.
|
|
boolOrDefault is an enum with 3 values, BOU_UNSET, BOU_TRUE and BOU_FALSE.
|
|
This parser accepts the same strings as **``parser<bool>``**.
|
|
|
|
.. _strings:
|
|
|
|
* The **parser<string> specialization** simply stores the parsed string into the
|
|
string value specified. No conversion or modification of the data is
|
|
performed.
|
|
|
|
.. _integers:
|
|
.. _int:
|
|
|
|
* The **parser<int> specialization** uses the C ``strtol`` function to parse the
|
|
string input. As such, it will accept a decimal number (with an optional '+'
|
|
or '-' prefix) which must start with a non-zero digit. It accepts octal
|
|
numbers, which are identified with a '``0``' prefix digit, and hexadecimal
|
|
numbers with a prefix of '``0x``' or '``0X``'.
|
|
|
|
.. _doubles:
|
|
.. _float:
|
|
.. _double:
|
|
|
|
* The **parser<double>** and **parser<float> specializations** use the standard
|
|
C ``strtod`` function to convert floating point strings into floating point
|
|
values. As such, a broad range of string formats is supported, including
|
|
exponential notation (ex: ``1.7e15``) and properly supports locales.
|
|
|
|
.. _Extension Guide:
|
|
.. _extending the library:
|
|
|
|
Extension Guide
|
|
===============
|
|
|
|
Although the CommandLine library has a lot of functionality built into it
|
|
already (as discussed previously), one of its true strengths lie in its
|
|
extensibility. This section discusses how the CommandLine library works under
|
|
the covers and illustrates how to do some simple, common, extensions.
|
|
|
|
.. _Custom parsers:
|
|
.. _custom parser:
|
|
.. _Writing a Custom Parser:
|
|
|
|
Writing a custom parser
|
|
-----------------------
|
|
|
|
One of the simplest and most common extensions is the use of a custom parser.
|
|
As `discussed previously`_, parsers are the portion of the CommandLine library
|
|
that turns string input from the user into a particular parsed data type,
|
|
validating the input in the process.
|
|
|
|
There are two ways to use a new parser:
|
|
|
|
#. Specialize the `cl::parser`_ template for your custom data type.
|
|
|
|
This approach has the advantage that users of your custom data type will
|
|
automatically use your custom parser whenever they define an option with a
|
|
value type of your data type. The disadvantage of this approach is that it
|
|
doesn't work if your fundamental data type is something that is already
|
|
supported.
|
|
|
|
#. Write an independent class, using it explicitly from options that need it.
|
|
|
|
This approach works well in situations where you would line to parse an
|
|
option using special syntax for a not-very-special data-type. The drawback
|
|
of this approach is that users of your parser have to be aware that they are
|
|
using your parser instead of the builtin ones.
|
|
|
|
To guide the discussion, we will discuss a custom parser that accepts file
|
|
sizes, specified with an optional unit after the numeric size. For example, we
|
|
would like to parse "102kb", "41M", "1G" into the appropriate integer value. In
|
|
this case, the underlying data type we want to parse into is '``unsigned``'. We
|
|
choose approach #2 above because we don't want to make this the default for all
|
|
``unsigned`` options.
|
|
|
|
To start out, we declare our new ``FileSizeParser`` class:
|
|
|
|
.. code-block:: c++
|
|
|
|
struct FileSizeParser : public cl::basic_parser<unsigned> {
|
|
// parse - Return true on error.
|
|
bool parse(cl::Option &O, const char *ArgName, const std::string &ArgValue,
|
|
unsigned &Val);
|
|
};
|
|
|
|
Our new class inherits from the ``cl::basic_parser`` template class to fill in
|
|
the default, boiler plate code for us. We give it the data type that we parse
|
|
into, the last argument to the ``parse`` method, so that clients of our custom
|
|
parser know what object type to pass in to the parse method. (Here we declare
|
|
that we parse into '``unsigned``' variables.)
|
|
|
|
For most purposes, the only method that must be implemented in a custom parser
|
|
is the ``parse`` method. The ``parse`` method is called whenever the option is
|
|
invoked, passing in the option itself, the option name, the string to parse, and
|
|
a reference to a return value. If the string to parse is not well-formed, the
|
|
parser should output an error message and return true. Otherwise it should
|
|
return false and set '``Val``' to the parsed value. In our example, we
|
|
implement ``parse`` as:
|
|
|
|
.. code-block:: c++
|
|
|
|
bool FileSizeParser::parse(cl::Option &O, const char *ArgName,
|
|
const std::string &Arg, unsigned &Val) {
|
|
const char *ArgStart = Arg.c_str();
|
|
char *End;
|
|
|
|
// Parse integer part, leaving 'End' pointing to the first non-integer char
|
|
Val = (unsigned)strtol(ArgStart, &End, 0);
|
|
|
|
while (1) {
|
|
switch (*End++) {
|
|
case 0: return false; // No error
|
|
case 'i': // Ignore the 'i' in KiB if people use that
|
|
case 'b': case 'B': // Ignore B suffix
|
|
break;
|
|
|
|
case 'g': case 'G': Val *= 1024*1024*1024; break;
|
|
case 'm': case 'M': Val *= 1024*1024; break;
|
|
case 'k': case 'K': Val *= 1024; break;
|
|
|
|
default:
|
|
// Print an error message if unrecognized character!
|
|
return O.error("'" + Arg + "' value invalid for file size argument!");
|
|
}
|
|
}
|
|
}
|
|
|
|
This function implements a very simple parser for the kinds of strings we are
|
|
interested in. Although it has some holes (it allows "``123KKK``" for example),
|
|
it is good enough for this example. Note that we use the option itself to print
|
|
out the error message (the ``error`` method always returns true) in order to get
|
|
a nice error message (shown below). Now that we have our parser class, we can
|
|
use it like this:
|
|
|
|
.. code-block:: c++
|
|
|
|
static cl::opt<unsigned, false, FileSizeParser>
|
|
MFS("max-file-size", cl::desc("Maximum file size to accept"),
|
|
cl::value_desc("size"));
|
|
|
|
Which adds this to the output of our program:
|
|
|
|
::
|
|
|
|
OPTIONS:
|
|
-help - display available options (-help-hidden for more)
|
|
...
|
|
-max-file-size=<size> - Maximum file size to accept
|
|
|
|
And we can test that our parse works correctly now (the test program just prints
|
|
out the max-file-size argument value):
|
|
|
|
::
|
|
|
|
$ ./test
|
|
MFS: 0
|
|
$ ./test -max-file-size=123MB
|
|
MFS: 128974848
|
|
$ ./test -max-file-size=3G
|
|
MFS: 3221225472
|
|
$ ./test -max-file-size=dog
|
|
-max-file-size option: 'dog' value invalid for file size argument!
|
|
|
|
It looks like it works. The error message that we get is nice and helpful, and
|
|
we seem to accept reasonable file sizes. This wraps up the "custom parser"
|
|
tutorial.
|
|
|
|
Exploiting external storage
|
|
---------------------------
|
|
|
|
Several of the LLVM libraries define static ``cl::opt`` instances that will
|
|
automatically be included in any program that links with that library. This is
|
|
a feature. However, sometimes it is necessary to know the value of the command
|
|
line option outside of the library. In these cases the library does or should
|
|
provide an external storage location that is accessible to users of the
|
|
library. Examples of this include the ``llvm::DebugFlag`` exported by the
|
|
``lib/Support/Debug.cpp`` file and the ``llvm::TimePassesIsEnabled`` flag
|
|
exported by the ``lib/VMCore/PassManager.cpp`` file.
|
|
|
|
.. todo::
|
|
|
|
TODO: complete this section
|
|
|
|
.. _dynamically loaded options:
|
|
|
|
Dynamically adding command line options
|
|
|
|
.. todo::
|
|
|
|
TODO: fill in this section
|