| <html> |
| <head> |
| <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> |
| <title>Check Utilities</title> |
| <link rel="stylesheet" href="../boostbook.css" type="text/css"> |
| <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> |
| <link rel="home" href="../index.html" title="Predef 1.2"> |
| <link rel="up" href="../index.html" title="Predef 1.2"> |
| <link rel="prev" href="reference/version_definition_macros.html" title="Version definition macros"> |
| <link rel="next" href="history.html" title="History"> |
| </head> |
| <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> |
| <div class="spirit-nav"> |
| <a accesskey="p" href="reference/version_definition_macros.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="history.html"><img src="../images/next.png" alt="Next"></a> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="predef.check_utilities"></a><a class="link" href="check_utilities.html" title="Check Utilities">Check Utilities</a> |
| </h2></div></div></div> |
| <p> |
| The <code class="computeroutput"><span class="identifier">predef_check</span></code> utility provides |
| a facility for building a program that will check a given set of expressions |
| against the definitions it detected when it was built. |
| </p> |
| <h4> |
| <a name="predef.check_utilities.h0"></a> |
| <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> |
| programs</a> |
| </h4> |
| <p> |
| Even though there is only one <code class="computeroutput"><span class="identifier">predef_check</span></code> |
| program, there are variations for each of the languages that are detected by |
| Predef to match the convention for sources files. For all of them one invokes |
| with a list of expression arguments. The expressions are evaluated within the |
| context of the particular <code class="literal">predef_check</code> program and if they |
| all are true zero (0) is returned. Otherwise the index of the first false expression |
| is returned. |
| </p> |
| <p> |
| The expression syntax is simple: |
| </p> |
| <pre class="programlisting">predef-definition [ relational-operator version-value ] |
| </pre> |
| <p> |
| <em class="replaceable"><code>predef-definition</code></em> can be any of the Predef definitions. |
| For example <code class="computeroutput"><span class="identifier">BOOST_COMP_GCC</span></code>. |
| </p> |
| <p> |
| <em class="replaceable"><code>relational-operator</code></em> can be any of: <code class="literal">></code>, |
| <code class="literal"><</code>, <code class="literal">>=</code>, <code class="literal"><=</code>, |
| <code class="literal">==</code> and <code class="literal">!=</code>. |
| </p> |
| <p> |
| <em class="replaceable"><code>version-number</code></em> can be a full or partial version |
| triplet value. If it's a partial version triple it is completed with zeros. |
| That is <code class="literal">x.y</code> is equivalent to <code class="literal">x.y.0</code> and |
| <code class="literal">x</code> is equivalent to <code class="literal">x.0.0</code>. |
| </p> |
| <p> |
| The <em class="replaceable"><code>relations-operator</code></em> and <em class="replaceable"><code>version-number</code></em> |
| can be ommited. In which case it is equivalent to: |
| </p> |
| <pre class="programlisting">predef-definition > 0.0.0 |
| </pre> |
| <h4> |
| <a name="predef.check_utilities.h1"></a> |
| <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 |
| with Boost.Build</a> |
| </h4> |
| <p> |
| You can use the <code class="literal">predef_check</code> programs directly from Boost |
| Build to configure target requirements. This is useful for controlling what |
| gets built as part of your project based on the detailed version information |
| available in Predef. The basic use is simple: |
| </p> |
| <pre class="programlisting">import path-to-predef-src/check/predef |
| : check require |
| : predef-check predef-require ; |
| |
| exe my_windows_program : windows_source.cpp |
| : [ predef-require "BOOST_OS_WINDOWS" ] ; |
| </pre> |
| <p> |
| That simple use case will skip building the <code class="literal">my_windows_program</code> |
| unless one is building for Windows. Like the direct <code class="literal">predef_check</code> |
| you can pass mutiple expressions using relational comparisons. For example: |
| </p> |
| <pre class="programlisting">import path-to-predef-src/check/predef |
| : check require |
| : predef-check predef-require ; |
| |
| lib my_special_lib : source.cpp |
| : [ predef-require "BOOST_OS_WINDOWS != 0" "BOOST_OS_VMS != 0"] ; |
| </pre> |
| <p> |
| And in that case the <code class="literal">my_special_lib</code> is built only when the |
| OS is not Windows or VMS. The <code class="literal">requires</code> rule is a special |
| case of the <code class="literal">check</code> rule. And is defined in terms of it: |
| </p> |
| <pre class="programlisting">rule require ( expressions + : language ? ) |
| { |
| return [ check $(expressions) : $(language) : : <build>no ] ; |
| } |
| </pre> |
| <p> |
| You can use the <code class="literal">check</code> rule for more control and to implement |
| something other than control of what gets built. The definition for the <code class="literal">check</code> |
| rule is: |
| </p> |
| <pre class="programlisting">rule check ( expressions + : language ? : true-properties * : false-properties * ) |
| </pre> |
| <p> |
| When invoked as a reuirement of a Boost Build target this rule will add the |
| <code class="literal">true-properties</code> to the target if all the <code class="literal">expressions</code> |
| evaluate to true. Otherwise the <code class="literal">false-properties</code> get added |
| as requirements. For example you could use it to enable or disable features |
| in your programs: |
| </p> |
| <pre class="programlisting">import path-to-predef-src/check/predef |
| : check require |
| : predef-check predef-require ; |
| |
| exe my_special_exe : source.cpp |
| : [ predef-check "BOOST_OS_WINDOWS == 0" |
| : <define>ENABLE_WMF=0 |
| : <define>ENABLE_WMF=1 ] ; |
| </pre> |
| <p> |
| For both <code class="literal">check</code> and <code class="literal">require</code> the <code class="literal">language</code> |
| argument controls which variant of the <code class="literal">predef_check</code> program |
| is used to check the expressions. It defaults to "c++", but can be |
| any of: "c", "cpp", "objc", and "objcpp". |
| </p> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2005, 2008-2014 Rene Rivera<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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>) |
| </p> |
| </div></td> |
| </tr></table> |
| <hr> |
| <div class="spirit-nav"> |
| <a accesskey="p" href="reference/version_definition_macros.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="history.html"><img src="../images/next.png" alt="Next"></a> |
| </div> |
| </body> |
| </html> |
