| Brian Silverman | f27e085 | 2018-08-04 23:56:45 -0700 | [diff] [blame^] | 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. |
| 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. |
| 24 | However, any informative text will work. |
| 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>. |
| 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. |
| 36 | Finding any errors is sometimes less than straightforward. |
| 37 | Use of this macro can provide information to make this much easier. |
| 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. |
| 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. |
| 53 | Those compilers typically issues warnings about the bad filename. |
| 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> <a href="../headers/debug/line.html"><boost/preprocessor/debug/line.hpp></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 <<a href="../headers/arithmetic/dec.html">boost/preprocessor/arithmetic/dec.hpp</a>> |
| 72 | #include <<a href="../headers/cat.html">boost/preprocessor/cat.hpp</a>> |
| 73 | #include <<a href="../headers/debug/line.html">boost/preprocessor/debug/line.hpp</a>> |
| 74 | #include <<a href="../headers/iteration/iterate.html">boost/preprocessor/iteration/iterate.hpp</a>> |
| 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> |