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Last change on this file since 30 was 29, checked in by landauf, 17 years ago

updated boost from 1_33_1 to 1_34_1
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1<html>
2<head>
3        <title>BOOST_PP_LINE</title>
4        <link rel="stylesheet" type="text/css" href="../styles.css">   
5</head>
6<body>
7        <div style="margin-left:  0px;">
8                The <b>BOOST_PP_LINE</b> macro places notes encoded as line directives in the preprocessing output.
9        </div>
10        <h4>Usage</h4>
11                <div class="code">
12                        #line <b>BOOST_PP_LINE</b>(<i>line</i>, <i>file</i>)
13                </div>
14        <h4>Arguments</h4>
15                <dl>
16                        <dt>line</dt>
17                        <dd>
18                                The new line number of the trailing line.&nbsp;
19                                The predefined macro <i>__LINE__</i> is commonly used.
20                        </dd>
21                        <dt>file</dt>
22                        <dd>
23                                Typically the name of the current file.&nbsp;
24                                However, any informative text will work.&nbsp;
25                                This text is internally stringized, so quotation marks are unnecessary.
26                        </dd>
27                </dl>
28        <h4>Remarks</h4>
29                <div>
30                        If the macro <b>BOOST_PP_CONFIG_EXTENDED_LINE_INFO</b> is defined as <i>1</i> and a <i>file-iteration</i>
31                        is in progress, this macro will automatically insert debugging information about the state of <i>file-iteration</i>.&nbsp;
32                        This information will show the all of the current iteration values with the inner most iteration last.
33                </div>
34                <div>
35                        This information is useful when errors might be spanning multiple iterations of the same source text.&nbsp;
36                        Finding any errors is sometimes less than straightforward.&nbsp;
37                        Use of this macro can provide information to make this much easier.&nbsp;
38                        For example, instead of getting several errors like this:
39                        <div><i>
40                                "file.hpp", line 2: error: expected a ";"<br>
41                                "file.hpp", line 4: error: improperly terminated macro invocation<br>
42                        </i></div>
43                        You might get something like this instead....
44                        <i><div>
45                                "file.hpp [1]", line 2: error: expected a ";"<br>
46                                "file.hpp [5]", line 4: error: improperly terminated macro invocation<br>
47                        </i></div>
48                        It is immediately evident that this error is spanning multiple iterations of the same source text.&nbsp;
49                        If it wasn't, the same errors would occur on each iteration.
50                </div>
51                <div>
52                        It must be noted however, that some compilers don't like filenames that aren't actually files.&nbsp;
53                        Those compilers typically issues warnings about the bad filename.&nbsp;
54                        This makes it a good idea to only define <b>BOOST_PP_CONFIG_EXTENDED_LINE_INFO</b> to <i>1</i> <i>only</i> when debugging.
55                </div>
56        <h4>See Also</h4>
57                <ul>
58                        <li><a href="config_extended_line_info.html">BOOST_PP_CONFIG_EXTENDED_LINE_INFO</a></li>
59                </ul>
60        <h4>Requirements</h4>
61                <div>
62                        <b>Header:</b> &nbsp;<a href="../headers/debug/line.html">&lt;boost/preprocessor/debug/line.hpp&gt;</a>
63                </div>
64        <h4>Sample Code</h4>
65<div><pre>
66// sample.cpp
67#if !defined(<a href="is_iterating.html">BOOST_PP_IS_ITERATING</a>)
68
69   #define <a href="config_extended_line_info.html">BOOST_PP_CONFIG_EXTENDED_LINE_INFO</a> 1
70
71   #include &lt;<a href="../headers/arithmetic/dec.html">boost/preprocessor/arithmetic/dec.hpp</a>&gt;
72   #include &lt;<a href="../headers/cat.html">boost/preprocessor/cat.hpp</a>&gt;
73   #include &lt;<a href="../headers/debug/line.html">boost/preprocessor/debug/line.hpp</a>&gt;
74   #include &lt;<a href="../headers/iteration/iterate.html">boost/preprocessor/iteration/iterate.hpp</a>&gt;
75
76   namespace sample {
77
78   #define <a href="iteration_params_x.html">BOOST_PP_ITERATION_PARAMS_1</a> (3, (1, 5, "sample.cpp"))
79   #include <a href="iterate.html">BOOST_PP_ITERATE</a>()
80
81   } // sample
82
83   int main(void) {
84      return 0;
85   }
86
87#else
88
89   #line <a href="line.html">BOOST_PP_LINE</a>(1, sample.cpp)
90
91   int <a href="cat.html">BOOST_PP_CAT</a>(x, <a href="iteration.html">BOOST_PP_ITERATION</a>())); // extra parenthesis
92   
93   struct <a href="cat.html">BOOST_PP_CAT</a>(s, <a href="dec.html">BOOST_PP_DEC</a>(<a href="iteration.html">BOOST_PP_ITERATION</a>()) {
94      // missing a parenthesis
95      // ...
96   };
97
98#endif
99</pre></div>
100        <hr size="1">
101        <div style="margin-left: 0px;">
102                <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
103                </br><i>© Copyright Paul Mensonides 2002</i>
104        </div>
105        <div style="margin-left: 0px;">
106                <p><small>Distributed under the Boost Software License, Version 1.0. (See
107                accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
108                copy at <a href=
109                "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
110        </div>
111</body>
112</html>
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