<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Portability</title> <link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> <link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> <link rel="up" href="../foreach.html" title="Chapter 6. Boost.Foreach"> <link rel="prev" href="extensibility.html" title="Extensibility"> <link rel="next" href="pitfalls.html" title="Pitfalls"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> <td align="center"><a href="../../../index.html">Home</a></td> <td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="extensibility.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../foreach.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="pitfalls.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> </div> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="foreach.portability"></a><a class="link" href="portability.html" title="Portability">Portability</a> </h2></div></div></div> <p> <code class="literal">BOOST_FOREACH</code> uses some fairly sophisticated techniques that not all compilers support. Depending on how compliant your compiler is, you may not be able to use <code class="literal">BOOST_FOREACH</code> in some scenarios. Since <code class="literal">BOOST_FOREACH</code> uses <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>, it inherits <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>'s portability issues. You can read about those issues in the <a href="../../../libs/range/doc/html/range/portability.html" target="_top">Boost.Range Portability</a> section. </p> <p> In addition to the demands placed on the compiler by <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>, <code class="literal">BOOST_FOREACH</code> places additional demands in order to handle rvalue sequences properly. (Recall that an rvalue is an unnamed object, so an example of an rvalue sequence would be a function that returns a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><></span></code> by value.) Compilers vary in their handling of rvalues and lvalues. To cope with the situation <code class="literal">BOOST_FOREACH</code> defines three levels of compliance, described below: </p> <div class="table"> <a name="id1261693"></a><p class="title"><b>Table 6.1. BOOST_FOREACH Compliance Levels</b></p> <div class="table-contents"><table class="table" summary="BOOST_FOREACH Compliance Levels"> <colgroup> <col> <col> </colgroup> <thead><tr> <th> <p> Level </p> </th> <th> <p> Meaning </p> </th> </tr></thead> <tbody> <tr> <td> <p> <span class="bold"><strong>Level 0</strong></span> </p> </td> <td> <p> <span class="emphasis"><em><span class="underline">Highest level of compliance</span></em></span><br> <code class="literal">BOOST_FOREACH</code> works with lvalues, rvalues and const-qualified rvalues. </p> </td> </tr> <tr> <td> <p> <span class="bold"><strong>Level 1</strong></span> </p> </td> <td> <p> <span class="emphasis"><em><span class="underline">Moderate level of compliance</span></em></span><br> <code class="literal">BOOST_FOREACH</code> works with lvalues and plain rvalues, but not const-qualified rvalues.<br> <code class="computeroutput"><span class="identifier">BOOST_FOREACH_NO_CONST_RVALUE_DETECTION</span></code> is defined in this case. </p> </td> </tr> <tr> <td> <p> <span class="bold"><strong>Level 2</strong></span> </p> </td> <td> <p> <span class="emphasis"><em><span class="underline">Lowest level of compliance</span></em></span><br> <code class="literal">BOOST_FOREACH</code> works with lvalues only, not rvalues.<br> <code class="computeroutput"><span class="identifier">BOOST_FOREACH_NO_RVALUE_DETECTION</span></code> is defined in this case. </p> </td> </tr> </tbody> </table></div> </div> <br class="table-break"><p> Below are the compilers with which <code class="literal">BOOST_FOREACH</code> has been tested, and the compliance level <code class="literal">BOOST_FOREACH</code> provides for them. </p> <div class="table"> <a name="id1261882"></a><p class="title"><b>Table 6.2. Compiler Compliance Level</b></p> <div class="table-contents"><table class="table" summary="Compiler Compliance Level"> <colgroup> <col> <col> </colgroup> <thead><tr> <th> <p> Compiler </p> </th> <th> <p> Compliance Level </p> </th> </tr></thead> <tbody> <tr> <td> <p> Visual C++ 8.0 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> Visual C++ 7.1 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> Visual C++ 7.0 </p> </td> <td> <p> Level 2 </p> </td> </tr> <tr> <td> <p> Visual C++ 6.0 </p> </td> <td> <p> Level 2 </p> </td> </tr> <tr> <td> <p> gcc 4.0 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> gcc 3.4 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> gcc 3.3 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> mingw 3.4 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> Intel for Linux 9.0 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> Intel for Windows 9.0 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> Intel for Windows 8.0 </p> </td> <td> <p> Level 1 </p> </td> </tr> <tr> <td> <p> Intel for Windows 7.0 </p> </td> <td> <p> Level 2 </p> </td> </tr> <tr> <td> <p> Comeau 4.3.3 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> Borland 5.6.4 </p> </td> <td> <p> Level 2 </p> </td> </tr> <tr> <td> <p> Metrowerks 9.5 </p> </td> <td> <p> Level 1 </p> </td> </tr> <tr> <td> <p> Metrowerks 9.4 </p> </td> <td> <p> Level 1 </p> </td> </tr> <tr> <td> <p> SunPro 5.8 </p> </td> <td> <p> Level 2 </p> </td> </tr> <tr> <td> <p> qcc 3.3 </p> </td> <td> <p> Level 0 </p> </td> </tr> <tr> <td> <p> tru64cxx 65 </p> </td> <td> <p> Level 2 </p> </td> </tr> <tr> <td> <p> tru64cxx 71 </p> </td> <td> <p> Level 2 </p> </td> </tr> </tbody> </table></div> </div> <br class="table-break"> </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 © 2004 Eric Niebler<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="extensibility.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../foreach.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="pitfalls.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>