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<td width="885"> <font face="Verdana, Arial, Helvetica, sans-serif"><b><font size="6">Compile
Time Configuration</font></b></font></td>
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<p><b><a name="compiletime_config"></a>Library compile time configuration</b></p>
<P dir="ltr">The C++ preprocessor iterator library may be configured at compile
time by specifying different preprocessor constants to include different additional
features. The possible preprocessor constants are described in the following
table. </P>
<table width="100%" border="0" align="center">
<tr>
<td colspan="2" class="table_title"><b>Summary of possible preprocessor constants
for<br>
library configuration</b></td>
</tr>
<tr>
<td width="46%" class="table_cells"><code>BOOST_WAVE_SUPPORT_WARNING_DIRECTIVE</code></td>
<td width="54%" class="table_cells"> <p>Support the #warning directive</p></td>
</tr>
<tr>
<td width="46%" class="table_cells"><code><code>BOOST_</code>WAVE_SUPPORT_MS_EXTENSIONS</code></td>
<td width="54%" class="table_cells"> <p>Support several MS specific language
extensions (i.e. <tt>__int8</tt> et.al.)</p></td>
</tr>
<tr>
<td class="table_cells"><code><code>BOOST_</code>WAVE_PREPROCESS_ERROR_MESSAGE_BODY</code></td>
<td class="table_cells"><p>Enable the preprocessing of the message bodies
of <span class="keyword">#error</span> and <span class="keyword">#warning</span>
directives.</p></td>
</tr>
<tr>
<td class="table_cells"><code><code>BOOST_</code>WAVE_RETURN_PRAGMA_DIRECTIVES</code></td>
<td class="table_cells"><p>If defined, then the <span class="keyword">#pragma</span>
directives are returned as a token sequence to the caller, if not defined,
the whole <span class="keyword">#pragma</span> directive is skipped. </p></td>
</tr>
<tr>
<td class="table_cells"><code><code>BOOST_</code>WAVE_PREPROCESS_PRAGMA_BODY</code></td>
<td class="table_cells"><p>Enable the preprocessing of the bodies of <span class="keyword">
#pragma</span> directives.<br>
Note though, that the body of an <tt>operator _Pragma()</tt> is preprocessed
always, as required by the C99 Standard <a href="references.html#iso_c">[2]</a>.
</p></td>
</tr>
<tr>
<td class="table_cells"><code><code>BOOST_</code>WAVE_ENABLE_COMMANDLINE_MACROS</code></td>
<td class="table_cells"><p>Enable the functionality required to define macros
with the command line syntax (-DMACRO(x)=definition)</p></td>
</tr>
<tr>
<td class="table_cells"><code><code>BOOST_</code>WAVE_STRINGTYPE</code></td>
<td class="table_cells"><p>The tokens generated by the <tt>Wave</tt> library
contain the token data and the file position, where this token was found
in the input stream. <br>
This constant may be used to redefine the data type, which is used to
hold the token data and the corresponding file name. If this isn't defined
it defaults to std::string. (The here defined data type should be compatible
to the std::string type)</p></td>
</tr>
<tr>
<td class="table_cells"><code><code>BOOST_</code>WAVE_SUPPORT_VARIADICS_PLACEMARKERS</code></td>
<td class="table_cells"><p>If defined, then the preprocessor library supports
variadics and placemarkers. Note, to support C99 mode, this constant must
be defined too.</p></td>
</tr>
<tr>
<td class="table_cells"><code><code>BOOST_</code>WAVE_MAX_INCLUDE_LEVEL_DEPTH</code></td>
<td class="table_cells"><p>If defined, it will determine the initial maximal
possible include file nesting depth supported. It defaults to 1024.</p></td>
</tr>
<tr>
<td class="table_cells"><code><code>BOOST_</code>WAVE_SUPPORT_PRAGMA_ONCE</code></td>
<td class="table_cells"><p>If defined, then the <code>#pragma once</code> directive is supported by <tt>Wave</tt>. This specifies that the file, in which the pragma resides, will be included
(opened) only once by the compiler in a build. </p></td>
</tr>
<tr>
<td class="table_cells"><code>BOOST_</code><code>WAVE_SUPPORT_INCLUDE_NEXT</code></td>
<td class="table_cells"><p>If defined, then the <code>#include_next</code> directive is supported by <tt>Wave</tt>. This is syntactically equivalent to the <code>#include</code> directives, but may be used to inherit a header file (i.e. to include a file, which is named as the current file containing the <code>#include_next</code>).</p></td>
</tr>
</table>
<P dir="ltr"><b><a name="using_custom_lexer"></a>Using a different token type or lexer type in conjunction with Wave </b></P>
<P dir="ltr">It is possible to use the <tt>Wave</tt> library while using your own token and/or lexer types. This may be achieved by providing your lexer type as the second template parameter while instantiating the <tt>boost::wave::context<></tt> object. The token type used by the library is derived from the <tt>token_type</tt> typedef to be provided by the lexer type. If you want to provide your own token type only, you may use the <tt>boost::wave::lex_iterator<></tt> type contained with the library. This type needs to be parametrized with the token type to use. </P>
<P dir="ltr">To show, how this may be done, the <tt>Wave</tt> library contains several samples illustrating this possibility. The <tt>cpp_tokens</tt> sample shows the usage of a custom lexer and a custom token types. The lexer type used is functionally fully compatible to the <tt>re2c</tt> <a href="references.html#re2c">[3]</a> based lexer used by default. It is implemented based on the <tt>SLex</tt> <a href="references.html#slex">[5]</a> lexer example written by Dan Nuffer. The token type used therein is functionally equivalent to the default token type except for an additional <tt>operator<<</tt> used for dumping the information carried by the token.</P>
<P dir="ltr"><b><a name="compilation_models"></a>Separation and inclusion compilation
models</b></P>
<P dir="ltr">The <tt>Wave</tt> C++ preprocessor iterator library is build almost
completely as a header only library (except for the re2c based lexer). If you're
trying to include all required files at once you will mention, that the resulting
compilation times are very large (up to an hour - depending on your system configuration).
This straightforward method we'll call the inclusion compilation model. If you
do not pay attention to compilation times, that's the way to go, no special
handling is needed.</P>
<P dir="ltr">If you're interested in decreasing compilation times, the following
method is to be used. This we will call it the separation compilation model.
The trick is to separate the different objects such, that they are compilable
separately. The function, which instantiates the templated object in question
is factored out such, that its definition is visible to only one translation
unit. To simplify this further this creation function is packaged into a small
generator template structure.</P>
<P dir="ltr">There are two levels of separation implemented: the separation of
the compilation of the C++ lexer and the separation of the compilation of the
different Spirit grammars used. To use these separations you will have to define
two preprocessor constants while compiling the whole application and you will
have to explicitely instantiate some helper templates. The following tables
shows these constants in detail.</P>
<table width="90%" border="0" align="center">
<tr>
<td colspan="2" class="table_title"><b>Summary of possible compilation constants
required <br>
to enable the separation compilation model</b></td>
</tr>
<tr class="table_title">
<td width="25%"><b>Separate</b></td>
<td width="75%"><p><code><font face="Verdana, Arial, Helvetica, sans-serif">Preprocessor
constant</font></code></p></td>
</tr>
<tr>
<td width="25%" class="table_cells"><code>C++ lexer</code></td>
<td width="75%" class="table_cells"> <p><code><code>BOOST_</code>WAVE_SEPARATE_LEXER_INSTANTIATION</code></p></td>
</tr>
<tr>
<td width="25%" class="table_cells"><code>Spirit grammars</code></td>
<td width="75%" class="table_cells"> <p><code><code>BOOST_</code>WAVE_SEPARATE_GRAMMAR_INSTANTIATION</code></p></td>
</tr>
</table>
<P dir="ltr">The following table shows the explicit template instantiations required,
if you want to use the separation compilation model. The <tt>TokenT</tt> placeholder
type has to be replaced with your token type to use and the <code><tt>LexIteratorT</tt></code> placeholder type has to be replaced with your lex iterator type you've used while instantiation of the <tt>boost::wave::context<></tt> object. You will achieve the best
results, if you place these into separate compilation units each. The <tt>IteratorT</tt>
placeholder should be replaced by the iterator type, which was used to instantiate
the <tt>boost::wave::context<></tt> object.</P>
<table width="90%" border="0" align="center">
<tr>
<td colspan="2" class="table_title"><b>Summary of required explicit template
instantiations <br>
required when using the separation compilation model</b></td>
</tr>
<tr class="table_title">
<td width="25%"><b>Separate</b></td>
<td width="75%"><p><code><font face="Verdana, Arial, Helvetica, sans-serif">Templates
to explicitly instantiate</font></code></p></td>
</tr>
<tr>
<td width="25%" class="table_cells"><code>C++ lexer</code></td>
<td width="75%" class="table_cells"> <code><span class="keyword">template</span>
cpplexer::re2clex::new_lexer_gen<<tt>IteratorT</tt>>;</code></td>
</tr>
<tr>
<td width="25%" class="table_cells"><code>Spirit grammars</code></td>
<td width="75%" class="table_cells"> <p><code><span class="keyword">template</span> wave::grammars::expression_grammar_gen<<tt>TokenT</tt>>;<br>
<span class="keyword"> template</span> wave::grammars::intlit_grammar_gen<<tt>TokenT</tt>>;<br>
<span class="keyword"> template</span> wave::grammars::chlit_grammar_gen<<tt>TokenT</tt>>;<br>
<span class="keyword"> <code>template</code><code></code><code> wave::grammars::cpp_grammar_gen<<tt>LexIteratorT</tt>>;<br>
</code>template</span> wave::grammars::predefined_macros_grammar_gen<<tt>LexIteratorT</tt>>;<br>
<span class="keyword"> template</span> wave::grammars::defined_grammar_gen<<tt>LexIteratorT</tt>>;</code></p></td>
</tr>
</table>
<p>To see an example of this you can look at the <tt>Wave</tt> driver program
included as an acompanion sample to the C++ preprocessor iterator library. The
corresponding files are named obviously <span class="string">"instantiate_...something.cpp"</span>,
where the <span class="string">'...somthing'</span> is a hint, which grammars
are explicitely instantiated inside. By using the separation model the compilation
times required to build the <tt>Wave</tt> example are dropped by up to 90%.</p>
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<p class="copyright">Copyright © 2003-2005 Hartmut Kaiser<br>
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<font size="2">Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) </font> </p>
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<p class="copyright"><span class="updated">Last updated:
<!-- #BeginDate format:fcAm1m -->Sunday, May 15, 2005 12:23<!-- #EndDate -->
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