current_exception.html 5.5 KB

12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364
  1. <!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Strict//EN'
  2. 'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'>
  3. <html xmlns='http://www.w3.org/1999/xhtml' xml:lang='en' lang='en'>
  4. <head>
  5. <meta http-equiv='Content-Type' content='text/html; charset=utf-8'/>
  6. <title>current_exception</title>
  7. <link href='reno.css' type='text/css' rel='stylesheet'/>
  8. </head>
  9. <body>
  10. <div class="body-0">
  11. <div class="body-1">
  12. <div class="body-2">
  13. <div>
  14. <div id="boost_logo">
  15. <a href="http://www.boost.org"><img style="border:0" src="../../../boost.png" alt="Boost" width="277" height="86"/></a>
  16. </div>
  17. <h1>Boost Exception</h1>
  18. </div>
  19. <!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. -->
  20. <!-- Distributed under the Boost Software License, Version 1.0. (See accompanying -->
  21. <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
  22. <div class="RenoIncludeDIV"><div class="RenoAutoDIV"><h3>current_exception</h3>
  23. </div>
  24. <div class="RenoIncludeDIV"><p><span class="RenoEscape">&#35;<!--<wiki>`&#35;</wiki>--></span>include &lt;<span class="RenoLink"><a href="boost_exception_ptr_hpp.html">boost/exception_ptr.hpp</a></span>&gt;</p>
  25. <pre>namespace
  26. boost
  27. {
  28. <span class="RenoIncludeSPAN"> <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> <span class="RenoLink">current_exception</span>();</span>
  29. }</pre>
  30. </div><h4>Requirements:</h4>
  31. <p>The <span class="RenoLink">current_exception</span> function must not be called outside of a catch block.</p>
  32. <p>In addition, to safely copy an exception from one thread to another, if the exception object is copied by <span class="RenoLink">current_exception</span> or <span class="RenoLink"><a href="copy_exception.html">copy_exception</a></span>, the two copies must not have shared state. Exceptions that have value-type semantics (as well as the boost::<span class="RenoLink"><a href="exception.html">exception</a></span> type itself) satisfy this requirement.</p>
  33. <h4>Returns:</h4>
  34. <div><ul><li> An <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> that refers to the currently handled exception or a copy of the currently handled exception.</li>
  35. <li> If the function needs to allocate memory and the attempt fails, it returns an <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> that refers to an instance of std::bad_alloc.</li>
  36. </ul></div>
  37. <h4>Throws:</h4>
  38. <p>Nothing.</p>
  39. <h4>Notes:</h4>
  40. <div><ul><li> It is unspecified whether the return values of two successive calls to <span class="RenoLink">current_exception</span> refer to the same exception object.</li>
  41. <li> Correct implementation of <span class="RenoLink">current_exception</span> may require compiler support, unless <span class="RenoLink"><a href="enable_current_exception.html">enable_current_exception</a></span> was used at the time the currently handled exception object was passed to throw. Whenever <span class="RenoLink">current_exception</span> fails to properly copy the current exception object, it returns an <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> to an object of type that is as close as possible to the original exception type, using <span class="RenoLink"><a href="unknown_exception.html">unknown_exception</a></span> as a final fallback. All such types derive from boost::<span class="RenoLink"><a href="exception.html">exception</a></span>, and:<div><ul><li> if the original exception object derives from boost::<span class="RenoLink"><a href="exception.html">exception</a></span>, then the boost::<span class="RenoLink"><a href="exception.html">exception</a></span> sub-object of the object referred to by the returned <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> is initialized by the boost::<span class="RenoLink"><a href="exception.html">exception</a></span> copy constructor;</li>
  42. <li> if available, the exception contains the std::type_info of the original exception object, accessible through <span class="RenoLink"><a href="get_error_info.html">get_error_info</a></span>&lt;<span class="RenoLink"><a href="original_exception_type.html">original_exception_type</a></span>&gt;.</li>
  43. </ul></div>
  44. </li>
  45. </ul></div>
  46. </div><div class="RenoAutoDIV"><div class="RenoHR"><hr/></div>
  47. See also: <span class="RenoPageList"><a href="boost-exception.html">Boost Exception</a>&nbsp;| <a href="boost_exception_ptr_hpp.html">boost/exception_ptr.hpp</a>&nbsp;| <a href="copy_exception.html">copy_exception</a>&nbsp;| <a href="enable_current_exception.html">enable_current_exception</a>&nbsp;| <a href="frequently_asked_questions.html">Frequently Asked Questions</a>&nbsp;| <a href="original_exception_type.html">original_exception_type</a>&nbsp;| <a href="unknown_exception.html">unknown_exception</a></span>
  48. </div>
  49. <!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. -->
  50. <!-- Distributed under the Boost Software License, Version 1.0. (See accompanying -->
  51. <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
  52. <div id="footer">
  53. <p>
  54. <a class="logo" href="http://jigsaw.w3.org/css-validator/check/referer"><img class="logo_pic" src="valid-css.png" alt="Valid CSS" height="31" width="88"/></a>
  55. <a class="logo" href="http://validator.w3.org/check?uri=referer"><img class="logo_pic" src="valid-xhtml.png" alt="Valid XHTML 1.0" height="31" width="88"/></a>
  56. <small>Copyright (c) 2006-2009 by Emil Dotchevski and Reverge Studios, Inc.<br/>
  57. Distributed under the <a href="http://www.boost.org/LICENSE_1_0.txt">Boost Software License, Version 1.0</a>.</small>
  58. </p>
  59. </div>
  60. </div>
  61. </div>
  62. </div>
  63. </body>
  64. </html>