1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2<html> 3<head> 4<title>The Context Policy</title> 5<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> 6<link href="theme/style.css" rel="stylesheet" type="text/css"> 7<style type="text/css"> 8.style1 { 9 background-color: #EEEEEE; 10} 11</style> 12</head> 13<body> 14<table background="theme/bkd2.gif" border="0" cellspacing="2" width="100%"> 15 <tbody> 16 <tr> 17 <td width="21"> </td> 18 <td width="885"><font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>The 19 Context Policy </b></font></td> 20 <td width="96"><a href="http://www.boost.org"><img src="theme/wave.gif" align="right" border="0" height="68" width="93"></a></td> 21 </tr> 22 </tbody> 23</table> 24<br> 25<table border="0"> 26 <tbody> 27 <tr> 28 <td width="10"></td> 29 <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> 30 <td width="30"><a href="class_reference_inptpolcy.html"><img src="theme/l_arr.gif" border="0" height="19" width="20"></a></td> 31 <td width="30"><a href="class_reference_lexer.html"><img src="theme/r_arr.gif" border="0"></a></td> 32 </tr> 33 </tbody> 34</table> 35<blockquote> 36 <p><a href="class_reference_ctxpolicy.html#introduction">Introduction</a><br> 37 <a href="class_reference_ctxpolicy.html#header_synopsis">Header 'wave/preprocessing_hooks.hpp' 38 synopsis</a><br> 39 <a href="class_reference_ctxpolicy.html#member_functions">Member functions</a></p> 40</blockquote> 41<h2><b><a name="introduction"></a>Introduction</b></h2> 42<p>Please note that the following description relates to the new 43 preprocessing hooks interface used by default starting with the Boost 44 V1.35.0 release. If you are interested in the older interface please 45 look <a href="class_ref_ctxpolicy_depr.html">here</a>. </p> 46<p>The context policy is used to provide callback hooks, which are called from inside the library into the user code, whenever</p> 47<ul> 48 <li>a preprocessor directive has been recognized, </li> 49 <li>a token is about to be returned from the preprocessor, </li> 50 <li>a macro gets defined or undefined, </li> 51 <li>a macro has been expanded or rescanned,</li> 52 <li>an include file has been opened or closed, </li> 53 <li>a conditional expression was evaluated,</li> 54 <li>a token has to be skipped because it is contained in a non-evaluated conditional block, </li> 55 <li> a pragma of the form <tt>'wave option[(value)]'</tt> has been recognized. </li> 56</ul> 57<p>This policy type is used as a template parameter to the <a href="class_reference_context.html"><tt>boost::wave::context<></tt></a> object, where the default policy provides empty hook functions only.</p> 58<h2><a name="header_synopsis"></a>Header <a href="http://svn.boost.org/trac/boost/browser/trunk/boost/wave/preprocessing_hooks.hpp">wave/preprocessing_hooks.hpp</a> synopsis</h2> 59<pre><span class="keyword">namespace</span> boost {<br><span class="keyword">namespace</span> wave {<br><span class="keyword">namespace</span> context_policies {<br> <br> <span class="keyword">struct</span> default_preprocessing_hooks {<br><br> <span class="comment">// general hook functions</span> 60 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#found_directive">found_directive</a>(ContextT <span class="keyword">const</span> &ctx, <br> TokenT <span class="keyword">const </span>&directive);<br> 61 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ExceptionT><br> void <a href="class_reference_ctxpolicy.html#trow_exception">throw_exception</a>(ContextT <span class="keyword">const</span> &ctx, <br> ExceptionT <span class="keyword">const</span>& e);<br><br> <span class="comment">// test, whether a given token may be skipped</span><br> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#may_skip_whitespace">may_skip_whitespace</a> (ContextT <span class="keyword">const</span>& ctx,<br> TokenT &token, <span class="keyword">bool</span> &skipped_newline);<br> 62 <span class="comment">// Conditional compilation</span><span class="keyword"> 63 template</span> <<br> <span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT, <br> <span class="keyword">typename</span> ContainerT<br> ><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#evaluated_conditional_expression">evaluated_conditional_expression</a>(<br> ContextT <span class="keyword">const</span> &ctx, TokenT <span class="keyword">const</span>& directive, <br> ContainerT <span class="keyword">const</span>& expression, <span class="keyword">bool</span> expression_value);<br> 64 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#skipped_token">skipped_token</a>(ContextT <span class="keyword">const</span> &ctx, <br> TokenT <span class="keyword">const</span>& token);<br><br> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> TokenT <span class="keyword">const</span>& <a href="class_reference_ctxpolicy.html#generated_token">generated_token</a>(ContextT <span class="keyword">const</span> &ctx, <br> TokenT <span class="keyword">const</span>& token);<br><br> <span class="comment">// macro expansion tracing</span><span class="keyword"> 65 template</span> <<span class="keyword"> 66 typename</span> ContextT, <span class="keyword">typename</span> TokenT, <span class="keyword">typename</span> ContainerT,<br> <span class="keyword">typename</span> IteratorT<br> ><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#expanding_function_like_macro">expanding_function_like_macro</a>(<br> ContextT <span class="keyword">const</span> &ctx, TokenT <span class="keyword">const</span> &macrodef, <br> <span class="keyword">std::vector</span><TokenT> <span class="keyword">const</span> &formal_args, <br> ContainerT <span class="keyword">const</span> &definition, TokenT <span class="keyword">const</span> &macrocall, <br> <span class="keyword">std::vector</span><ContainerT> <span class="keyword">const</span> &arguments,<br> IteratorT <span class="keyword">const</span> &seqstart, Iterator <span class="keyword">const</span> &seqend);<br> <br> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#expanding_object_like_macro">expanding_object_like_macro</a>(<br> ContextT <span class="keyword">const</span> &ctx, TokenT <span class="keyword">const</span> &macro, <br> ContainerT <span class="keyword">const</span> &definition, TokenT <span class="keyword">const</span> &macrocall);<br> <br> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#expanded_macro">expanded_macro</a>(ContextT <span class="keyword">const</span> &ctx, <br> ContainerT <span class="keyword">const</span> &result);<br> <br> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#expanded_macro">rescanned_macro</a>(ContextT <span class="keyword">const</span> &ctx, <br> ContainerT <span class="keyword">const</span> &result);<br><br> 67 <span class="comment">// include file tracing functions</span> 68 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#opened_include_file">found_include_directive</a>(ContextT <span class="keyword">const</span> &ctx, <br> std::string <span class="keyword">const</span> &filename, <span class="keyword">bool</span> include_next);<br> 69 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT><br> <span class="keyword">void </span><a href="class_reference_ctxpolicy.html#opened_include_file">opened_include_file</a>(ContextT <span class="keyword">const</span> &ctx, <br> std::string <span class="keyword">const</span> &relname, std::string <span class="keyword">const</span>& absname,<br> <span class="keyword">bool</span> is_system_include); <br> 70 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#returning_from_include_file">returning_from_include_file</a>(ContextT <span class="keyword">const</span> &ctx);<br> 71 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT><br> <span class="keyword">void</span> <a href="#detected_include_guard">detected_include_guard</a>(ContextT <span class="keyword">const</span> &ctx, 72 std::string <span class="keyword">const</span>& filename, 73 std::string <span class="keyword">const</span>& include_guard);<br> 74 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> <span class="keyword">void</span> <a href="#detected_pragma_once">detected_pragma_once</a>(ContextT <span class="keyword">const</span> &ctx, 75 TokenT <span class="keyword">const</span>& pragma_token, 76 std::string <span class="keyword">const</span>& filename);<br><br> 77 <span class="comment">// interpretation of #pragmas of the form </span> 78 <span class="comment">// 'wave option[(value)]'</span> 79 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#interpret_pragma">interpret_pragma</a>(ContextT <span class="keyword">const</span> &ctx, ContainerT &pending, <br> <span class="keyword">typename</span> ContextT::token_type <span class="keyword">const</span> &option, <br> ContainerT <span class="keyword">const</span> &values, <br> <span class="keyword">typename</span> ContextT::token_type <span class="keyword">const</span> &pragma_token);<br><br> 80 <span class="comment">// macro definition hooks</span> 81 <span class="keyword">template</span> <<br> <span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT, <span class="keyword"> 82 typename</span> ParametersT, <span class="keyword">typename</span> DefinitionT<br> ><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#defined_macro">defined_macro</a>(ContextT <span class="keyword">const</span> &ctx, TokenT <span class="keyword">const</span> &name, <span class="keyword"> 83 bool</span> is_functionlike, ParametersT <span class="keyword">const</span> &parameters, <br> DefinitionT <span class="keyword">const</span> &definition, <span class="keyword">bool</span> is_predefined);<br><br> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#undefined_macro">undefined_macro</a>(ContextT <span class="keyword">const</span> &ctx, <br> TokenT<span class="keyword"> const</span> &name);<br><br> 84 <span class="comment">// #error and #warning directive hooks</span> 85 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#found_warning_directive">found_warning_directive</a>(ContextT <span class="keyword">const</span> &ctx, <br> ContainerT <span class="keyword">const</span> &message);<br><br> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#found_error_directive">found_error_directive</a>(ContextT <span class="keyword">const</span> &ctx, <br> ContainerT <span class="keyword">const</span> &message);<br><br> <span class="comment">// #line directive hook</span> 86 <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#found_line_directive">found_line_directive</a>(ContextT <span class="keyword">const</span> &ctx, <br> ContainerT <span class="keyword">const</span> &arguments, <span class="keyword">unsigned int</span> line,<br> std::string <span class="keyword">const</span>& filename);<br> };<br><br>}}} <span class="comment">// namespace boost::wave::context_policies</span></pre> 87<h2><a name="member_functions"></a>Member functions</h2> 88<h3>General hook functions </h3> 89<p><a name="found_directive"></a><strong>found_directive</strong></p> 90<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> <span class="keyword">bool</span> found_directive(ContextT <span class="keyword">const</span>& ctx, TokenT <span class="keyword">const </span>&directive); 91</pre> 92<blockquote> 93 <p>The function <tt>found_directive</tt> is called, whenever the preprocessor has detected one of the preprocessing directives (<span class="preprocessor">#define</span>, <span class="preprocessor">#undef</span>, <span class="preprocessor">#if</span>, <span class="preprocessor">#idef</span>, <span class="preprocessor">#ifndef</span>, <span class="preprocessor">#elif</span>, <span class="preprocessor">#endif</span>, <span class="preprocessor">#error</span>, <span class="preprocessor">#include</span>, <span class="preprocessor">#pragma</span> or <span class="preprocessor">#warning</span>) .</p> 94 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 95 Note, this parameter was added for the Boost V1.35.0 release. </p> 96 <p>The parameter <tt>directive</tt> refers to the token containing the detected preprocessing directive. </p> 97 <p>If the return value is <tt>true</tt>, the directive will be 98 skipped altogether, i.e. no preprocessing is done. The overall 99 directive is replaced by a single newline character. If the return 100 value is <tt>false</tt>, the directive is processed in the normal manner. </p> 101</blockquote> 102<p><a name="throw_exception"></a><strong>throw_exception</strong></p> 103<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ExceptionT><br> void throw_exception(ContextT <span class="keyword">const</span> &ctx, <br> ExceptionT <span class="keyword">const</span>& e);</pre> 104<blockquote> 105 <p>he function <tt>throw_exception</tt> is called, whenever a preprocessing exception occurs .</p> 106 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. </p> 107 <p>The parameter <tt>e</tt> is the exception object containing detailed error information. </p> 108</blockquote> 109<p><a name="may_skip_whitespace" id="may_skip"></a><strong>may_skipwhitespace</strong></p> 110<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> <span class="keyword">bool</span> may_skip_whitespace(ContextT <span class="keyword">const</span>& ctx, TokenT &token, <br> <span class="keyword">bool</span>& skipped_newline); 111</pre> 112<blockquote> 113 <p>The function <tt>may_skipwhitespace</tt> will be called by the library, whenever a token is about to be returned to the calling application. </p> 114 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 115 Note, this parameter was added for the Wave V1.2.4 release. </p> 116 <p>The <tt>token</tt> parameter holds a reference to the current token. The policy is free to change this token if needed.</p> 117 <p>The <tt>skipped_newline</tt> parameter holds a reference to a 118 boolean value which should be set to true by the policy function 119 whenever a newline is going to be skipped. </p> 120 <p>If the return value is <tt>true</tt>, the given token is skipped and the preprocessing continues to the next token. If the return value is <tt>false</tt>, the given token is returned to the calling application. Caution has to be used, because by returning <span class="keyword">true</span> the policy function is able to force skipping even significant tokens not only whitespace. </p> 121</blockquote> 122<h3>Conditional compilation hook functions </h3> 123<p><a name="evaluated_conditional_expression"></a><strong>evaluated_conditional_expression</strong></p> 124<pre><span class="keyword"> template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT, <span class="keyword">typename</span> ContainerT> 125<span class="keyword"> bool</span> evaluated_conditional_expression(ContextT <span class="keyword">const</span>& ctx, <br> TokenT <span class="keyword">const</span>& directive, ContainerT <span class="keyword">const</span>& expression, <span class="keyword"><br> bool</span> expression_value); 126</pre> 127<blockquote> 128 <p>The function <tt>evaluated_conditional_expression</tt> is called, whenever the preprocessor has encountered a <span class="preprocessor">#if</span>, <span class="preprocessor">#elif</span>, <span class="preprocessor">#ifdef</span> or <span class="preprocessor">#ifndef</span> directive. This hook gets passed the non-expanded conditional 129 expression (as it was given in the analysed source file) and the result 130 of the evaluation of this expression in the current preprocessing 131 context.</p> 132 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 133 Note, this parameter was added for the Boost V1.35.0 release. </p> 134 <p>The <tt>token</tt> parameter holds a reference to the evaluated directive token. </p> 135 <p>The parameter <tt>expression</tt> holds the non-expanded token sequence 136 comprising the evaluated expression.</p> 137 <p>The parameter <tt>expression_value</tt> contains the result of the evaluation of 138 the expression in the current preprocessing context. </p> 139 <p>The return value defines, whether the given expression has to be 140 evaluated again, allowing to decide which of the conditional branches 141 should be expanded. You need to return '<span class="keyword">true</span>' from this hook function to force the expression to be re-evaluated. Note, this was changed from a '<span class="keyword">void</span>' for the Boost V1.35.0 release. <br> 142 </p> 143</blockquote> 144<p><a name="skipped_token"></a><strong>skipped_token</strong></p> 145<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> <span class="keyword">void</span> skipped_token(ContextT <span class="keyword">const</span>& ctx, TokenT <span class="keyword">const</span>& token); 146</pre> 147<blockquote> 148 <p>The function <tt>skipped_token</tt> is called, whenever a token is about to be skipped due to a false preprocessor condition (code fragments to be 149 skipped inside the not evaluated conditional <span class="preprocessor">#if</span>/<span class="preprocessor">#else</span>/<span class="preprocessor">#endif</span> branches).</p> 150 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 151 Note, this parameter was added for the Boost V1.35.0 release. </p> 152 <p>The parameter <tt>token</tt> refers to the token to be skipped.</p> 153</blockquote> 154<p><a name="generated_token"></a><strong>generated_token</strong></p> 155<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> TokenT <span class="keyword">const</span>& generated_token(ContextT <span class="keyword">const</span>& ctx, TokenT <span class="keyword">const</span>& token); 156</pre> 157<blockquote> 158 <p>The function <tt>generated_token</tt> is called, whenever a token is about to be returned from the library.</p> 159 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 160 Note, this parameter was added for the Boost V1.35.0 release. </p> 161 <p>The parameter <tt>token</tt> refers to the token about to be 162 returned from the library. This function may alter the token, but in 163 this case it must be implemented with a non-const reference for the 164 token parameter, allowing to modify the token in place.</p> 165 <p>The default behavior is to return the passed token reference unchanged to the caller.</p> 166</blockquote> 167<h3>Macro expansion tracking functions</h3> 168<p><a name="expanding_function_like_macro"></a><b>expanding_function_like_macro</b></p> 169<pre><span class="keyword"> template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">bool</span> expanding_function_like_macro(<br> ContextT <span class="keyword">const</span>& ctx, TokenT <span class="keyword">const</span> &macrodef, <br> <span class="keyword">std::vector</span><TokenT> <span class="keyword">const</span> &formal_args, <br> ContainerT <span class="keyword">const</span> &definition, TokenT <span class="keyword">const</span> &macrocall, <br> <span class="keyword">std::vector</span><ContainerT> <span class="keyword">const</span> &arguments,<br> IteratorT <span class="keyword">const</span> &seqstart, Iterator <span class="keyword">const</span> &seqend);</pre> 170<blockquote> 171 <p>The function <tt>expanding_function_like_macro</tt> is called, whenever a 172 function-like macro is to be expanded, i.e. <i>before</i> the actual expansion 173 starts.</p> 174 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 175 Note, this parameter was added for the Boost V1.35.0 release. </p> 176 <p>The <tt>macroname</tt> parameter marks the position where the macro to expand 177 is defined. It contains the token which identifies the macro name used inside 178 the corresponding macro definition.</p> 179 <p>The <tt>formal_args</tt> parameter holds the formal arguments used during 180 the definition of the macro. </p> 181 <p>The <tt>definition</tt> parameter holds the macro definition for the macro 182 to trace. This is a standard STL container which holds the token sequence 183 identified during the macro definition as the macro replacement list.</p> 184 <p>The <tt>macrocall</tt> parameter marks the position where this macro is invoked. 185 It contains the token, which identifies the macro call inside the preprocessed 186 input stream. </p> 187 <p>The <tt>arguments</tt> parameter holds the macro arguments used during the 188 invocation of the macro. This is a vector of standard STL containers which 189 contain the token sequences identified at the position of the macro call as 190 the arguments to be used during the macro expansion. </p> 191 <p>The parameters <tt>seqstart</tt> and <tt>seqend</tt> point into the input token 192 stream allowing to access the whole token sequence comprising the macro 193 invocation (starting with the opening parenthesis and ending after the 194 closing one).</p> 195 <p>If the return value is <tt>true</tt>, the macro is not expanded, 196 i.e. the overall macro invocation sequence, including the parameters 197 are copied to the output without further processing . If the return 198 value is <tt>false</tt>, the macro is expanded as expected. <br> 199 </p> 200</blockquote> 201<p><a name="expanding_object_like_macro"></a><b>expanding_object_like_macro</b></p> 202<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">bool</span> expanding_object_like_macro(<br> ContextT <span class="keyword">const</span>& ctx, TokenT <span class="keyword">const</span> &macro, <br> ContainerT <span class="keyword">const</span> &definition, TokenT <span class="keyword">const</span> &macrocall); 203</pre> 204<blockquote> 205 <p>The function <tt>expanding_object_like_macro</tt> is called, whenever a object-like 206 macro is to be expanded, i.e. <i>before</i> the actual expansion starts.</p> 207 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 208 Note, this parameter was added for the Boost V1.35.0 release. </p> 209 <p>The <tt>macroname</tt> parameter marks the position where the macro to expand 210 is defined. It contains the token which identifies the macro name used inside 211 the corresponding macro definition.</p> 212 <p> The <tt>definition</tt> parameter holds the macro definition for the macro 213 to trace. This is a standard STL container which holds the token sequence 214 identified during the macro definition as the macro replacement list.</p> 215 <p>The <tt>macrocall</tt> parameter marks the position where this macro is invoked. 216 It contains the token which identifies the macro call inside the preprocessed 217 input stream. </p> 218 <p>If the return value is <tt>true</tt>, the macro is not expanded, i.e. the macro symbol is copied to the output without further processing. If the return value is <tt>false</tt>, the macro is expanded as expected. <br> 219 </p> 220</blockquote> 221<p><a name="expanded_macro"></a><b>expanded_macro</b></p> 222<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">void</span> expanded_macro(ContextT <span class="keyword">const</span>& ctx, ContainerT <span class="keyword">const</span> &result); 223</pre> 224<blockquote> 225 <p>The function <tt>expanded_macro</tt> is called whenever the expansion of 226 a macro is finished, the replacement list is completely scanned and the identified 227 macros herein are replaced by its corresponding expansion results, but <i>before</i> the rescanning process starts.</p> 228 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 229 Note, this parameter was added for the Boost V1.35.0 release. </p> 230 <p>The parameter <tt>result</tt> contains the the result of the macro expansion 231 so far. This is a standard STL container containing the generated token sequence.</p> 232</blockquote> 233<p><a name="rescanned_macro"></a><b>rescanned_macro</b></p> 234<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">void</span> rescanned_macro(ContextT <span class="keyword">const</span>& ctx, ContainerT <span class="keyword">const</span> &result); 235</pre> 236<blockquote> 237 <p>The function <tt>rescanned_macro</tt> is called whenever the rescanning 238 of a macro is finished, i.e. the macro expansion is complete.</p> 239 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 240 Note, this parameter was added for the Boost V1.35.0 release. </p> 241 <p>The parameter <tt>result</tt> contains the the result of the whole macro 242 expansion. This is a standard STL container containing the generated token 243 sequence.</p> 244</blockquote> 245<h3>Include file tracing functions</h3> 246<p><a name="opened_include_file" id="found_include_directive"></a><strong>found_include_directive</strong></p> 247<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT><br> <span class="keyword">bool</span> found_include_directive(ContextT <span class="keyword">const</span>& ctx, <br> std::string <span class="keyword">const</span> &filename, <span class="keyword">bool</span> include_next); 248</pre> 249<blockquote> 250 <p>The function <tt>found_include_directive</tt> is called whenever whenever a #include directive was located..</p> 251 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 252 Note, this parameter was added for the Boost V1.35.0 release. </p> 253 <p>The parameter <tt>filename</tt> contains the (expanded) file name found after 254 the <span class="preprocessor">#include</span> directive. This has the format <tt><file></tt>, <tt>"file"</tt> or <tt>file</tt>. 255 The formats <tt><file></tt> or <tt>"file"</tt> are used for <span class="preprocessor">#include</span> directives found 256 in the preprocessed token stream, the format <tt>file</tt> is used for files 257 specified through the --force_include command line argument.</p> 258 <p>The parameter <tt>include_next</tt> is set to true if the found directive was 259 a <span class="preprocessor">#include_next</span> directive and the <tt>BOOST_WAVE_SUPPORT_INCLUDE_NEXT</tt> preprocessing constant was defined to something != 0.</p> 260 <p>If the return value is <tt>true</tt>, the include directive is not 261 executed, i.e. the file to include is not loaded nor processed. The 262 overall directive is replaced by a single newline character. If the 263 return value is <tt>false</tt>, the directive is executed in a normal manner. <br> 264 </p> 265</blockquote> 266<p><a name="opened_include_file" id="opened_include_file"></a><strong>opened_include_file</strong></p> 267<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT><br> <span class="keyword">void</span> opened_include_file(ContextT <span class="keyword">const</span>& ctx, <br> std::string <span class="keyword">const</span> &rel_filename, std::string <span class="keyword">const</span> &abs_filename, <br> <span class="keyword">bool</span> is_system_include); 268</pre> 269<blockquote> 270 <p>The function <tt>opened_include_file</tt> is called whenever a file referred 271 by an <span class="preprocessor">#include</span> directive was successfully located and opened.</p> 272 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 273 Note, this parameter was added for the Boost V1.35.0 release. </p> 274 <p>The parameter <tt>rel_filename</tt> contains the (normalised) 275 probably relative file system path of the opened file. The concrete 276 format of this file name depends on the format of the include search 277 path given to the library beforehand.</p> 278 <p>The parameter <tt>abs_filename</tt> contains the (normalised) full file system path of the 279 opened file.</p> 280 <p>The <tt>is_system_include</tt> parameter denotes, if the given file was found 281 as a result of a <tt>#include <...></tt> directive.</p> 282</blockquote> 283<p><a name="returning_from_include_file" id="returning_from_include_file"></a><strong>returning_from_include_file</strong></p> 284<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT><br> <span class="keyword">void</span> returning_from_include_file(ContextT <span class="keyword">const</span>& ctx); 285</pre> 286<blockquote> 287 <p>The function <tt>returning_from_include_file</tt> is called whenever an 288 included file is about to be closed after it's processing is complete.</p> 289 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 290 Note, this parameter was added for the Boost V1.35.0 release. </p> 291</blockquote> 292<p><a name="detected_include_guard" id="detected_include_guard"></a><strong>detected_include_guard</strong></p> 293<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT><br> <span class="keyword">void</span> detected_include_guard(ContextT <span class="keyword">const</span>& ctx, 294 std::string <span class="keyword">const</span>& filename, 295 std::string <span class="keyword">const</span>& include_guard); 296</pre> 297<blockquote> 298 <p>The function <tt>detected_include_guard</tt> is called whenever a<span lang="de">n</span> 299 include file is about to be added to the list of #pragma once headers as the 300 result of a detected include guard scheme. That means this header file will 301 not be opened and parsed again even if it is specified in a later 302 <span class="preprocessor">#include</span> directive. </p> 303 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> 304 used during instantiation of the preprocessing iterators by the user. </p> 305 <p>The parameter <tt>filename</tt> contains the file system path of the opened file 306 (this is relative to the directory of the currently processed file or a 307 absolute path depending on the paths given as the include search paths).</p> 308 <p>The parameter <tt>include_guard</tt> contains the name of the detected include guard.<br> </p> 309</blockquote> 310<p><a name="detected_pragma_once" id="detected_pragma_once"></a><strong>detected_pragma_once</strong></p> 311<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename </span>TokenT><br> <span class="keyword">void</span> detected_<span lang="de">p<span class="style1">ragma<span lang="en-us">_</span>once</span></span>(ContextT <span class="keyword">const</span>& ctx, 312<span lang="de"> TokenT <span class="keyword">const</span>& pragma_token,</span> 313 std::string <span class="keyword">const</span>& filename);</pre> 314<blockquote> 315 <p>The function <tt>detected_pragma_once</tt> is called whenever either a<span lang="de">n</span> 316 include file is about to be added to the list of #pragma once headers as the 317 result of a detected <span lang="de"><span class="preprocessor">#pragma once</span> 318 directive</span>. That means this header file will not be opened and parsed 319 again even if it is specified in a later <span class="preprocessor">#include</span> 320 directive. </p> 321 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> 322 used during instantiation of the preprocessing iterators by the user. </p> 323 <p><span lang="de">The parameter pragma_token refers to the token "#pragma" 324 triggering this preprocessing hook.</span></p> 325 <p>The parameter <tt>filename</tt> contains the file system path of the opened file 326 (this is relative to the directory of the currently processed file or a 327 absolute path depending on the paths given as the include search paths).</p> 328</blockquote> 329<h3>Interpretation of #pragmas</h3> 330<p><strong><a name="interpret_pragma"></a>interpret_pragma</strong></p> 331<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> bool <a href="class_reference_ctxpolicy.html#interpret_pragma">interpret_pragma</a>(ContextT <span class="keyword">const</span> &ctx, ContainerT &pending, <br> <span class="keyword">typename</span> ContextT::token_type <span class="keyword">const</span> &option, <br> ContainerT <span class="keyword">const</span> &values, <br> <span class="keyword">typename</span> ContextT::token_type<span class="keyword"> const</span> &pragma_token);<br> 332</pre> 333<blockquote> 334 <p>The function <tt>interpret_pragma</tt> is called whenever an unrecognized <tt>#pragma wave ...</tt> or operator <tt>_Pragma("wave ...")</tt> is found in the input stream.</p> 335 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. </p> 336 <p>The <tt>pending</tt> parameter may be used to push tokens back into the input 337 stream which are to be used as the replacement text for the whole <tt>#pragma wave()</tt> directive. If this sequence is left empty, no replacement takes place, i.e. 338 the interpreted directive is removed from the generated token stream.</p> 339 <p>The <tt>option</tt> parameter contains the name of the interpreted pragma.</p> 340 <p>The <tt>values</tt> parameter holds the value of the parameter provided to 341 the pragma operator.</p> 342 <p>The <tt>pragma_token</tt> parameter contains the actual #pragma token which 343 may be used for extraction of the location information for some error output.</p> 344 <p>If the return value is 'false', the whole #pragma directive is interpreted 345 as unknown and a corresponding error message is issued. A return value of 346 'true' signs a successful interpretation of the given #pragma.<br> 347 </p> 348</blockquote> 349<h3>Macro definition </h3> 350<p><strong><a name="defined_macro" id="defined_macro"></a>defined_macro</strong></p> 351<pre> <span class="keyword">template</span> <<br> <span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT, <span class="keyword">typename</span> ParametersT, <span class="keyword"> 352 typename</span> DefinitionT<br> ><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#defined_macro">defined_macro</a>(ContextT <span class="keyword">const</span>& ctx, <br> TokenT <span class="keyword">const</span> &name, <span class="keyword">bool</span> is_functionlike,<br> ParametersT <span class="keyword">const</span> &parameters, DefinitionT <span class="keyword">const</span> &definition,<br> <span class="keyword">bool</span> is_predefined);<br> 353</pre> 354<blockquote> 355 <p>The function <tt>defined_macro</tt> is called whenever a macro was defined successfully.</p> 356 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 357 Note, this parameter was added for the Boost V1.35.0 release. </p> 358 <p>The parameter <tt>name</tt> is a reference to the token holding the macro name.</p> 359 <p>The parameter <tt>is_functionlike</tt> is set to true whenever the newly 360 defined macro is defined as a function like macro.</p> 361 <p>The parameter <tt>parameters</tt> holds the parameter tokens for the macro 362 definition. If the macro has no parameters or if it is a object like 363 macro, then this container is empty.</p> 364 <p>The parameter <tt>definition</tt> contains the token sequence given as the 365 replacement sequence (definition part) of the newly defined macro.</p> 366 <p>The parameter <tt>is_predefined</tt> is set to true for all macros predefined 367 during the initialisation pahase of the library.<br> 368 </p> 369</blockquote> 370<p><strong><a name="undefined_macro" id="undefined_macro"></a>undefined_macro</strong></p> 371<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> TokenT><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#undefined_macro">undefined_macro</a>(ContextT <span class="keyword">const</span>& ctx, TokenT <span class="keyword">const</span> &name);<br> 372</pre> 373<blockquote> 374 <p>The function <tt>undefined_macro</tt> is called whenever a macro definition 375 was removed successfully.</p> 376 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. 377 Note, this parameter was added for the Boost V1.35.0 release. </p> 378 <p>The parameter <tt>name</tt> holds the token of the macro which definition was removed.<br> 379 </p> 380</blockquote> 381<p><strong><a name="found_warning_directive" id="found_warning_directive"></a>found_warning_directive</strong></p> 382<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#found_warning_directive">found_warning_directive</a>(ContextT <span class="keyword">const</span>& ctx, <br> ContainerT <span class="keyword">const</span> &message);<br> 383</pre> 384<blockquote> 385 <p>The function <tt>found_warning_directive </tt> is called whenever a <span class="preprocessor">#warning </span>directive 386 has been encountered. Note, this function was added for the Boost 387 V1.35.0 release. This function will be called only if the <tt>BOOST_WAVE_SUPPORT_WARNING_DIRECTIVE</tt> compile time constant was defined to something not equal to zero (see the <a href="compiletime_config.html">Compile Time Configuration</a> for more information). </p> 388 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. </p> 389 <p>The parameter <tt>message</tt> references the argument token sequence of the encountered <span class="preprocessor">#warning</span> directive.</p> 390 <p>If the return value is <tt>false</tt>, the library throws a preprocessor 391 exception of the type <code>warning_directive</code> (normal execution continues), if the return value is <tt>true</tt> the execution continues as if no <span class="preprocessor">#warning</span> directive has been found and the overall directive is replaced by a single newline. </p> 392</blockquote> 393<p><strong><a name="found_error_directive" id="found_error_directive"></a>found_error_directive</strong></p> 394<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">bool</span> <a href="class_reference_ctxpolicy.html#found_error_directive">found_error_directive</a>(ContextT <span class="keyword">const</span>& ctx, <br> ContainerT <span class="keyword">const</span> &message);<br> 395</pre> 396<blockquote> 397 <p>The function <tt>found_error_directive </tt> is called whenever a <span class="preprocessor">#error </span>directive has been encountered. Note, this function was added for the Boost V1.35.0 release. </p> 398 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. </p> 399 <p>The parameter <tt>message</tt> references the argument token sequence of the encountered <span class="preprocessor">#error</span> directive.</p> 400 <p>If the return value is <tt>false</tt>, the library throws a preprocessor 401 exception of the type <code>error_directive</code> (normal execution continues), if the return value is <tt>true</tt> the execution continues as if no <span class="preprocessor">#error</span> directive has been found and the overall directive is replaced by a single newline. </p> 402</blockquote> 403<p><strong><a name="found_line_directive" id="found_line_directive"></a>found_line_directive</strong></p> 404<pre> <span class="keyword">template</span> <<span class="keyword">typename</span> ContextT, <span class="keyword">typename</span> ContainerT><br> <span class="keyword">void</span> <a href="class_reference_ctxpolicy.html#found_error_directive"><strong>found_line_directive</strong></a>(ContextT <span class="keyword">const</span>& ctx, <br> ContainerT <span class="keyword">const</span> &arguments, <span class="keyword">unsigned int</span> line,<br> std::string <span class="keyword">const</span>& filename); 405</pre> 406<blockquote> 407 <p>The function <tt>found_line_directive </tt> is called whenever a <span class="preprocessor">#line </span>directive has been encountered. Note, this function was added for the Boost V1.35.0 release. </p> 408 <p>The <tt>ctx</tt> parameter provides a reference to the <tt>context_type</tt> used during instantiation of the preprocessing iterators by the user. </p> 409 <p>The parameter <tt>arguments</tt> references the argument token sequence of the encountered <span class="preprocessor">#line</span> directive.</p> 410 <p>The parameter <tt>line</tt> contains the recognized line number from the <span class="preprocessor">#line</span> directive.</p> 411 <p>The parameter <tt>filename</tt> references the recognized file name from the <span class="preprocessor">#line</span> directive (if there was one given).<br> 412 </p> 413</blockquote> 414<table border="0"> 415 <tbody> 416 <tr> 417 <td width="10"></td> 418 <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> 419 <td width="30"><a href="class_reference_inptpolcy.html"><img src="theme/l_arr.gif" border="0" height="19" width="20"></a></td> 420 <td width="30"><a href="class_reference_lexer.html"><img src="theme/r_arr.gif" border="0"></a></td> 421 </tr> 422 </tbody> 423</table> 424<hr size="1"> 425<p class="copyright">Copyright © 2003-2011 Hartmut Kaiser<br> 426 <br> 427 <font size="2">Distributed under the Boost Software License, Version 428 1.0. (See accompanying file LICENSE_1_0.txt or copy at 429 http://www.boost.org/LICENSE_1_0.txt) </font> </p> 430<p class="copyright"><span class="updated">Last updated: 431 <!-- #BeginDate format:fcAm1m -->Thursday, September 1<span lang="de">8</span>, 2010 432<span lang="de">09</span>:<span lang="de">10</span><!-- #EndDate --> 433 </span></p> 434</body> 435</html> 436
