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<title>Boost.MultiIndex Documentation - Compiler specifics</title>
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<h1><img src="../../../boost.png" alt="boost.png (6897 bytes)" align=
"middle" width="277" height="86">Boost.MultiIndex Compiler specifics</h1>
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Key extraction
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Performance
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<hr>
<p>
Boost.MultiIndex utilizes some C++11 capabilities but is also equipped
to work reasonably well in decent C++03-compliant environments.
We list some of the possible limitations along with suitable workarounds when available.
</p>
<h2>Contents</h2>
<ul>
<li><a href="#move">Move semantics</a></li>
<li><a href="#emplace">Emplace functions</a></li>
<li><a href="#initializer_list">Initializer lists</a></li>
<li><a href="#tuple">Tuples</a></li>
<li><a href="#symbol_reduction">Reduction of symbol name lengths</a>
<ul>
<li><a href="#argument_limitation">Limitation of maximum number of arguments</a></li>
<li><a href="#type_hiding">Type hiding</a></li>
</ul>
</li>
<li><a href="#legacy">Legacy compilers</a></li>
</ul>
<h2><a name="move">Move semantics</a></h2>
<p>
Boost.MultiIndex uses <a href="../../../doc/html/move.html">Boost.Move</a>
to support compilers without rvalue references. In such scenarios, taking
advantage of <code>multi_index_container&lt;Value&gt;</code> capabilities for
increased efficiency in insertion and handling of moveable-only elements will
require that <code>Value</code> be suitably instrumented.
</p>
<h2><a name="emplace">Emplace functions</a></h2>
<p>
In compilers without variadic template support, Boost.MultiIndex emplace
functions emulate this missing functionality by accepting up to
<code>BOOST_MULTI_INDEX_LIMIT_VARTEMPL_ARGS</code>
construction arguments that are internally forwarded with
<a href="../../../doc/html/move.html">Boost.Move</a>:
only constant lvalue references and rvalues are permitted as construction arguments
in such case.
</p>
<p>
<code>BOOST_MULTI_INDEX_LIMIT_VARTEMPL_ARGS</code>, which by default is 5, can
be globally defined by the user to a different value.
</p>
<h2><a name="initializer_list">Initializer lists</a></h2>
<p>
No transparent emulation of this functionality can be provided in the absence of
<code>std::initializer_list</code>: consider
<a href="../../../libs/assign/index.html">Boost.Assign</a> as a
possible replacement.
</p>
<h2><a name="tuple">Tuples</a></h2>
<p>
Everywhere where <code>std::tuple</code>s are used in the library interface,
<code>boost::tuple</code>s can be resorted to in their place. The converse, however,
is not true.
</p>
<h2><a name="symbol_reduction">Reduction of symbol name lengths</a></h2>
<p>
The types generated on the instantiations of <code>multi_index_container</code>s
typically produce very long symbol names, sometimes beyond the internal limits
of some compilers. There are several techniques to shorten generated symbol
names: these techniques have also the beneficial side effect that resulting error
messages are more readable.
</p>
<h3><a name="argument_limitation">Limitation of maximum number of arguments</a></h3>
<p>
The class templates <a href="reference/indices.html#indexed_by"><code>indexed_by</code></a>,
<a href="reference/indices.html#tag"><code>tag</code></a> and
<a href="reference/key_extraction.html#composite_key"><code>composite_key</code></a>
accept a variable number of arguments whose maximum number is limited by
internal macros. Even non-used arguments contribute to the final types,
so manually adjusting the corresponding macros can result in a modest reduction
of symbol names.
</p>
<p align="center">
<table cellspacing="0">
<caption><b>Limiting maximum number of arguments of some class templates
of Boost.MultiIndex.</b></caption>
<tr>
<th>class template</th>
<th>limiting macro</th>
<th>default value</th>
</tr>
<tr>
<td align="center">&nbsp;<code>indexed_by</code>&nbsp;</td>
<td align="center">&nbsp;<code>BOOST_MULTI_INDEX_LIMIT_INDEXED_BY_SIZE</code>&nbsp;</td>
<td align="center">20</td>
</tr>
<tr class="odd_tr">
<td align="center">&nbsp;<code>tag</code>&nbsp;</td>
<td align="center">&nbsp;<code>BOOST_MULTI_INDEX_LIMIT_TAG_SIZE</code>&nbsp;</td>
<td align="center">20</td>
</tr>
<tr>
<td align="center">&nbsp;<code>composite_key</code>&nbsp;</td>
<td align="center">&nbsp;<code>BOOST_MULTI_INDEX_LIMIT_COMPOSITE_KEY_SIZE</code>&nbsp;</td>
<td align="center">10</td>
</tr>
</table>
</p>
<h3><a name="type_hiding">Type hiding</a></h3>
<p>
Consider a typical instantiation of <code>multi_index_container</code>:
</p>
<blockquote><pre>
<span class=keyword>typedef</span> <span class=identifier>multi_index_container</span><span class=special>&lt;</span>
<span class=identifier>employee</span><span class=special>,</span>
<span class=identifier>indexed_by</span><span class=special>&lt;</span>
<span class=identifier>ordered_unique</span><span class=special>&lt;</span><span class=identifier>identity</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>&gt;</span> <span class=special>&gt;,</span>
<span class=identifier>ordered_non_unique</span><span class=special>&lt;</span><span class=identifier>member</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,&amp;</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>name</span><span class=special>&gt;</span> <span class=special>&gt;,</span>
<span class=identifier>ordered_unique</span><span class=special>&lt;</span><span class=identifier>member</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>,</span><span class=keyword>int</span><span class=special>,&amp;</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>ssnumber</span><span class=special>&gt;</span> <span class=special>&gt;</span>
<span class=special>&gt;</span>
<span class=special>&gt;</span> <span class=identifier>employee_set</span><span class=special>;</span>
</pre></blockquote>
<p>
Then, for instance, the type <code>employee_set::nth_index&lt;0&gt;::type</code>
resolves to the following in GCC:
</p>
<blockquote><pre>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>ordered_index</span><span class=special>&lt;</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>identity</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>&gt;,</span>
<span class=identifier>std</span><span class=special>::</span><span class=identifier>less</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>&gt;,</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>nth_layer</span><span class=special>&lt;</span>
<span class=number>1</span><span class=special>,</span> <span class=identifier>employee</span><span class=special>,</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>indexed_by</span><span class=special>&lt;</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>ordered_unique</span><span class=special>&lt;</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>identity</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>&gt;,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span>
<span class=special>&gt;,</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>ordered_non_unique</span><span class=special>&lt;</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>member</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>,</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,</span> <span class=special>&amp;</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>name</span><span class=special>&gt;,</span>
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span>
<span class=special>&gt;,</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>ordered_unique</span><span class=special>&lt;</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>member</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>,</span> <span class=keyword>int</span><span class=special>,</span> <span class=special>&amp;</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>ssnumber</span><span class=special>&gt;,</span>
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span>
<span class=special>&gt;,</span>
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span>
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span>
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span>
<span class=special>&gt;,</span>
<span class=identifier>std</span><span class=special>::</span><span class=identifier>allocator</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>&gt;</span>
<span class=special>&gt;,</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>mpl</span><span class=special>::</span><span class=identifier>vector0</span><span class=special>&lt;</span><span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>&gt;,</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>ordered_unique_tag</span>
<span class=special>&gt;</span>
</pre></blockquote>
<p>
It can be seen that a significant portion of the type name is contributed by
the <code>indexed_by&lt;...&gt;</code> part, which is nothing but an expanded
version of the index specifier list provided in the definition of
<code>employee_set</code>. We can prevent this very long name from appearing
in the final type by encapsulating it into another, shorter-named construct:
</p>
<blockquote><pre>
<span class=comment>// reducing symbol names through type hiding
// type hide the index specifier list within employee_set_indices</span>
<span class=keyword>struct</span> <span class=identifier>employee_set_indices</span><span class=special>:</span>
<span class=identifier>indexed_by</span><span class=special>&lt;</span>
<span class=identifier>ordered_unique</span><span class=special>&lt;</span><span class=identifier>identity</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>&gt;</span> <span class=special>&gt;,</span>
<span class=identifier>ordered_non_unique</span><span class=special>&lt;</span><span class=identifier>member</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,&amp;</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>name</span><span class=special>&gt;</span> <span class=special>&gt;,</span>
<span class=identifier>ordered_unique</span><span class=special>&lt;</span><span class=identifier>member</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>,</span><span class=keyword>int</span><span class=special>,&amp;</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>ssnumber</span><span class=special>&gt;</span> <span class=special>&gt;</span>
<span class=special>&gt;</span>
<span class=special>{};</span>
<span class=keyword>typedef</span> <span class=identifier>multi_index_container</span><span class=special>&lt;</span>
<span class=identifier>employee</span><span class=special>,</span>
<span class=identifier>employee_set_indices</span>
<span class=special>&gt;</span> <span class=identifier>employee_set</span><span class=special>;</span>
</pre></blockquote>
<p>
<code>employee_set_indices</code> works as a conventional <code>typedef</code>
in all respects, save for a detail: its name does not explicitly
include the information contained in the <code>indexed_by</code> instantiation.
Applying this technique, <code>employee_set::nth_index&lt;0&gt;::type</code>
now becomes:
</p>
<blockquote><pre>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>ordered_index</span><span class=special>&lt;</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>identity</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>&gt;,</span>
<span class=identifier>std</span><span class=special>::</span><span class=identifier>less</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>&gt;,</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>nth_layer</span><span class=special>&lt;</span>
<span class=number>1</span><span class=special>,</span> <span class=identifier>employee</span><span class=special>,</span>
<span class=identifier>employee_set_indices</span><span class=special>,</span>
<span class=identifier>std</span><span class=special>::</span><span class=identifier>allocator</span><span class=special>&lt;</span><span class=identifier>employee</span><span class=special>&gt;</span>
<span class=special>&gt;,</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>mpl</span><span class=special>::</span><span class=identifier>vector0</span><span class=special>&lt;</span><span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>&gt;,</span>
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>ordered_unique_tag</span>
<span class=special>&gt;</span>
</pre></blockquote>
<p>
which is considerably shorter than the original, and also more
easily parsed by a human reader. Type hiding would not work if, instead of
making <code>employee_set_indices</code> a derived <code>struct</code> of
<code>indexed_by&lt;...&gt;</code>, we had defined it as a <code>typedef</code>:
<code>typedef</code>s are syntactic aliases and usually get expanded
by the compiler before doing any further type handling.
</p>
<p>
Type hiding techniques can also be applied to <code>composite_key</code> intantiations,
which often contribute a great deal to symbol name lengths.
</p>
<h2><a name="legacy">Legacy compilers</a></h2>
<p>
Boost.MultiIndex support for legacy compilers is not actively kept, so if you happen
to work with an old environment you might need to use a former version of the library.
A table is provided of some legacy compilers along with the latest version of
Boost.MultiIndex known to work for them (frequently with limitations as explained
in the corresponding compiler specifics section.) If you successfully try one of those
with newer versions of Boost.MultiIndex than stated here, please report back so that
the information can be updated.
</p>
<p align="center">
<table cellspacing="0" cellpadding="5">
<caption><b>Support for legacy compilers.</b></caption>
<tr>
<th>Compiler</th>
<th>Latest known<br>compatible version</th>
<th>Date</th>
</tr>
<tr>
<td>Borland C++ Builder 6.4 through 2006, CodeGear C++Builder 2010</td>
<td>Never worked with Boost.MultiIndex</td>
<td></td>
</tr>
<tr class="odd_tr">
<td>Comeau C/C++ 4.3.10.1 for Windows (VC++ 9.0 backend)</td>
<td><a href="http://www.boost.org/doc/libs/1_38_0/libs/multi_index/doc/compiler_specifics.html#comeau_43101_win_vc7_71">Boost 1.38</a></td>
<td>February 2009</td>
</tr>
<tr>
<td>Compaq C++ 6.5-042 through 7.1-006 for Tru64 UNIX</td>
<td><a href="http://www.boost.org/doc/libs/1_38_0/libs/multi_index/doc/compiler_specifics.html#compaq_65">Boost 1.38</a></td>
<td>February 2009</td>
</tr>
<tr class="odd_tr">
<td>GCC 3.2 through 3.4</td>
<td><a href="http://www.boost.org/doc/libs/1_41_0/libs/multi_index/doc/compiler_specifics.html#gcc_32">Boost 1.41</a></td>
<td>November 2009</td>
</tr>
<tr>
<td>HP aC++ A.06.12 through A.06.17 for HP-UX IA64</td>
<td><a href="http://www.boost.org/doc/libs/1_38_0/libs/multi_index/doc/compiler_specifics.html#acc_612_ia64">Boost 1.38</a></td>
<td>February 2009</td>
</tr>
<tr class="odd_tr">
<td>HP aC++ A.03.80 through A.03.85 for HP-UX PA-RISC</td>
<td><a href="http://www.boost.org/doc/libs/1_38_0/libs/multi_index/doc/compiler_specifics.html#acc_380_pa_risc">Boost 1.38</a></td>
<td>February 2009</td>
</tr>
<tr>
<td>IBM VisualAge C++ V6.0 for AIX</td>
<td><a href="http://www.boost.org/doc/libs/1_33_1/libs/multi_index/doc/compiler_specifics.html#va_60">Boost 1.33.1</a></td>
<td>December 2006</td>
</tr>
<tr class="odd_tr">
<td>IBM XL C/C++ V9.0 through V10.1 for AIX</td>
<td><a href="http://www.boost.org/doc/libs/1_41_0/libs/multi_index/doc/compiler_specifics.html#xl_90">Boost 1.41</a></td>
<td>November 2009</td>
</tr>
<tr>
<td>Intel C++ Compiler for Linux 8.1 through 11.1</td>
<td><a href="http://www.boost.org/doc/libs/1_41_0/libs/multi_index/doc/compiler_specifics.html#intel_81_lin">Boost 1.41</a></td>
<td>November 2009</td>
</tr>
<tr class="odd_tr">
<td>Intel C++ Compiler for Mac OS 9.1 through 11.0</td>
<td><a href="http://www.boost.org/doc/libs/1_41_0/libs/multi_index/doc/compiler_specifics.html#intel_91_mac">Boost 1.41</a></td>
<td>November 2009</td>
</tr>
<tr>
<td>Intel C++ Compiler for Windows 32-bit 8.0 through 11.1</td>
<td><a href="http://www.boost.org/doc/libs/1_41_0/libs/multi_index/doc/compiler_specifics.html#intel_80_win">Boost 1.41</a></td>
<td>November 2009</td>
</tr>
<tr class="odd_tr">
<td>Intel C++ Compiler for Windows 64-bit 10.0 through 11.11</td>
<td><a href="http://www.boost.org/doc/libs/1_41_0/libs/multi_index/doc/compiler_specifics.html#intel_100_win64">Boost 1.41</a></td>
<td>November 2009</td>
</tr>
<tr>
<td>Metrowerks CodeWarrior 8.3</td>
<td><a href="http://www.boost.org/doc/libs/1_36_0/libs/multi_index/doc/compiler_specifics.html#cw_83">Boost 1.36</a></td>
<td>August 2008</td>
</tr>
<tr class="odd_tr">
<td>Metrowerks CodeWarrior 9 through 9.5</td>
<td><a href="http://www.boost.org/doc/libs/1_34_1/libs/multi_index/doc/compiler_specifics.html#cw_9x">Boost 1.34.1</a></td>
<td>July 2007</td>
</tr>
<tr>
<td>Microsoft Visual C++ 6.0 Service Pack 5</td>
<td><a href="http://www.boost.org/doc/libs/1_36_0/libs/multi_index/doc/compiler_specifics.html#msvc_60">Boost 1.36</a></td>
<td>August 2008</td>
</tr>
<tr class="odd_tr">
<td>Microsoft Visual C++ 7.0</td>
<td><a href="http://www.boost.org/doc/libs/1_35_0/libs/multi_index/doc/compiler_specifics.html#msvc_70">Boost 1.35</a></td>
<td>March 2008</td>
</tr>
<tr>
<td>Sun Studio 10 through 12 Update 1 for Solaris</td>
<td><a href="http://www.boost.org/doc/libs/1_41_0/libs/multi_index/doc/compiler_specifics.html#sun_10">Boost 1.41</a></td>
<td>November 2009</td>
</tr>
</table>
</p>
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<p>Revised August 20th 2014</p>
<p>&copy; Copyright 2003-2014 Joaqu&iacute;n M L&oacute;pez Mu&ntilde;oz.
Distributed under the Boost Software
License, Version 1.0. (See accompanying file <a href="../../../LICENSE_1_0.txt">
LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">
http://www.boost.org/LICENSE_1_0.txt</a>)
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