1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> 5<title>Check Utilities</title> 6<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../predef.html" title="Chapter 29. Boost.Predef 1.10"> 10<link rel="prev" href="reference.html" title="Reference"> 11<link rel="next" href="history.html" title="History"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> 16<td align="center"><a href="../../../index.html">Home</a></td> 17<td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="reference.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../predef.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="history.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="section"> 27<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 28<a name="predef.check_utilities"></a><a class="link" href="check_utilities.html" title="Check Utilities">Check Utilities</a> 29</h2></div></div></div> 30<p> 31 The <code class="computeroutput"><span class="identifier">predef_check</span></code> utility provides 32 a facility for building a program that will check a given set of expressions 33 against the definitions it detected when it was built. 34 </p> 35<h4> 36<a name="predef.check_utilities.h0"></a> 37 <span class="phrase"><a name="predef.check_utilities.predef_check_programs"></a></span><a class="link" href="check_utilities.html#predef.check_utilities.predef_check_programs"><code class="literal">predef_check</code> 38 programs</a> 39 </h4> 40<p> 41 Even though there is only one <code class="computeroutput"><span class="identifier">predef_check</span></code> 42 program, there are variations for each of the languages that are detected by 43 Predef to match the convention for sources files. For all of them one invokes 44 with a list of expression arguments. The expressions are evaluated within the 45 context of the particular <code class="literal">predef_check</code> program and if they 46 all are true zero (0) is returned. Otherwise the index of the first false expression 47 is returned. 48 </p> 49<p> 50 The expression syntax is simple: 51 </p> 52<pre class="programlisting">predef-definition [ relational-operator version-value ] 53</pre> 54<p> 55 <em class="replaceable"><code>predef-definition</code></em> can be any of the Predef definitions. 56 For example <code class="computeroutput"><span class="identifier">BOOST_COMP_GCC</span></code>. 57 </p> 58<p> 59 <em class="replaceable"><code>relational-operator</code></em> can be any of: <code class="literal">></code>, 60 <code class="literal"><</code>, <code class="literal">>=</code>, <code class="literal"><=</code>, 61 <code class="literal">==</code> and <code class="literal">!=</code>. 62 </p> 63<p> 64 <em class="replaceable"><code>version-number</code></em> can be a full or partial version 65 triplet value. If it's a partial version triple it is completed with zeros. 66 That is <code class="literal">x.y</code> is equivalent to <code class="literal">x.y.0</code> and 67 <code class="literal">x</code> is equivalent to <code class="literal">x.0.0</code>. 68 </p> 69<p> 70 The <em class="replaceable"><code>relations-operator</code></em> and <em class="replaceable"><code>version-number</code></em> 71 can be ommited. In which case it is equivalent to: 72 </p> 73<pre class="programlisting">predef-definition > 0.0.0 74</pre> 75<h4> 76<a name="predef.check_utilities.h1"></a> 77 <span class="phrase"><a name="predef.check_utilities.using_with_boost_build"></a></span><a class="link" href="check_utilities.html#predef.check_utilities.using_with_boost_build">Using 78 with Boost.Build</a> 79 </h4> 80<p> 81 You can use the <code class="literal">predef_check</code> programs directly from Boost 82 Build to configure target requirements. This is useful for controlling what 83 gets built as part of your project based on the detailed version information 84 available in Predef. The basic use is simple: 85 </p> 86<pre class="programlisting">import path-to-predef-src/tools/check/predef 87 : check require 88 : predef-check predef-require ; 89 90exe my_windows_program : windows_source.cpp 91 : [ predef-require "BOOST_OS_WINDOWS" ] ; 92</pre> 93<p> 94 That simple use case will skip building the <code class="literal">my_windows_program</code> 95 unless one is building for Windows. Like the direct <code class="literal">predef_check</code> 96 you can pass mutiple expressions using relational comparisons. For example: 97 </p> 98<pre class="programlisting">import path-to-predef-src/tools/check/predef 99 : check require 100 : predef-check predef-require ; 101 102lib my_special_lib : source.cpp 103 : [ predef-require "BOOST_OS_WINDOWS != 0" "BOOST_OS_VMS != 0"] ; 104</pre> 105<p> 106 And in that case the <code class="literal">my_special_lib</code> is built only when the 107 OS is not Windows or VMS. The <code class="literal">requires</code> rule is a special 108 case of the <code class="literal">check</code> rule. And is defined in terms of it: 109 </p> 110<pre class="programlisting">rule require ( expressions + : language ? ) 111{ 112 return [ check $(expressions) : $(language) : : <build>no ] ; 113} 114</pre> 115<p> 116 The expression can also use explicit "and", "or" logical 117 operators to for more complex checks: 118 </p> 119<pre class="programlisting">import path-to-predef-src/tools/check/predef 120 : check require 121 : predef-check predef-require ; 122 123lib my_special_lib : source.cpp 124 : [ predef-require "BOOST_OS_WINDOWS" or "BOOST_OS_VMS"] ; 125</pre> 126<p> 127 You can use the <code class="literal">check</code> rule for more control and to implement 128 something other than control of what gets built. The definition for the <code class="literal">check</code> 129 rule is: 130 </p> 131<pre class="programlisting">rule check ( expressions + : language ? : true-properties * : false-properties * ) 132</pre> 133<p> 134 When invoked as a reuirement of a Boost Build target this rule will add the 135 <code class="literal">true-properties</code> to the target if all the <code class="literal">expressions</code> 136 evaluate to true. Otherwise the <code class="literal">false-properties</code> get added 137 as requirements. For example you could use it to enable or disable features 138 in your programs: 139 </p> 140<pre class="programlisting">import path-to-predef-src/tools/check/predef 141 : check require 142 : predef-check predef-require ; 143 144exe my_special_exe : source.cpp 145 : [ predef-check "BOOST_OS_WINDOWS == 0" 146 : : <define>ENABLE_WMF=0 147 : <define>ENABLE_WMF=1 ] ; 148</pre> 149<p> 150 For both <code class="literal">check</code> and <code class="literal">require</code> the <code class="literal">language</code> 151 argument controls which variant of the <code class="literal">predef_check</code> program 152 is used to check the expressions. It defaults to "c++", but can be 153 any of: "c", "cpp", "objc", and "objcpp". 154 </p> 155</div> 156<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 157<td align="left"></td> 158<td align="right"><div class="copyright-footer">Copyright © 2005-2019 Rene Rivera<br>Copyright © 2015 Charly Chevalier<br>Copyright © 2015 Joel Falcou<p> 159 Distributed under the Boost Software License, Version 1.0. (See accompanying 160 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 161 </p> 162</div></td> 163</tr></table> 164<hr> 165<div class="spirit-nav"> 166<a accesskey="p" href="reference.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../predef.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="history.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 167</div> 168</body> 169</html> 170
