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| <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="id1261680"></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="id1261869"></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> |
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| <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> |
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