1<html lang="en"> 2<head> 3<title>Java Exceptions - Using the GNU Compiler Collection (GCC)</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Using the GNU Compiler Collection (GCC)"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="C_002b_002b-Extensions.html#C_002b_002b-Extensions" title="C++ Extensions"> 9<link rel="prev" href="Type-Traits.html#Type-Traits" title="Type Traits"> 10<link rel="next" href="Deprecated-Features.html#Deprecated-Features" title="Deprecated Features"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 141998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 152010 Free Software Foundation, Inc. 16 17Permission is granted to copy, distribute and/or modify this document 18under the terms of the GNU Free Documentation License, Version 1.3 or 19any later version published by the Free Software Foundation; with the 20Invariant Sections being ``Funding Free Software'', the Front-Cover 21Texts being (a) (see below), and with the Back-Cover Texts being (b) 22(see below). A copy of the license is included in the section entitled 23``GNU Free Documentation License''. 24 25(a) The FSF's Front-Cover Text is: 26 27 A GNU Manual 28 29(b) The FSF's Back-Cover Text is: 30 31 You have freedom to copy and modify this GNU Manual, like GNU 32 software. Copies published by the Free Software Foundation raise 33 funds for GNU development.--> 34<meta http-equiv="Content-Style-Type" content="text/css"> 35<style type="text/css"><!-- 36 pre.display { font-family:inherit } 37 pre.format { font-family:inherit } 38 pre.smalldisplay { font-family:inherit; font-size:smaller } 39 pre.smallformat { font-family:inherit; font-size:smaller } 40 pre.smallexample { font-size:smaller } 41 pre.smalllisp { font-size:smaller } 42 span.sc { font-variant:small-caps } 43 span.roman { font-family:serif; font-weight:normal; } 44 span.sansserif { font-family:sans-serif; font-weight:normal; } 45--></style> 46<link rel="stylesheet" type="text/css" href="../cs.css"> 47</head> 48<body> 49<div class="node"> 50<a name="Java-Exceptions"></a> 51<p> 52Next: <a rel="next" accesskey="n" href="Deprecated-Features.html#Deprecated-Features">Deprecated Features</a>, 53Previous: <a rel="previous" accesskey="p" href="Type-Traits.html#Type-Traits">Type Traits</a>, 54Up: <a rel="up" accesskey="u" href="C_002b_002b-Extensions.html#C_002b_002b-Extensions">C++ Extensions</a> 55<hr> 56</div> 57 58<h3 class="section">7.10 Java Exceptions</h3> 59 60<p>The Java language uses a slightly different exception handling model 61from C++. Normally, GNU C++ will automatically detect when you are 62writing C++ code that uses Java exceptions, and handle them 63appropriately. However, if C++ code only needs to execute destructors 64when Java exceptions are thrown through it, GCC will guess incorrectly. 65Sample problematic code is: 66 67<pre class="smallexample"> struct S { ~S(); }; 68 extern void bar(); // <span class="roman">is written in Java, and may throw exceptions</span> 69 void foo() 70 { 71 S s; 72 bar(); 73 } 74</pre> 75 <p class="noindent">The usual effect of an incorrect guess is a link failure, complaining of 76a missing routine called ‘<samp><span class="samp">__gxx_personality_v0</span></samp>’. 77 78 <p>You can inform the compiler that Java exceptions are to be used in a 79translation unit, irrespective of what it might think, by writing 80‘<samp><span class="samp">#pragma GCC java_exceptions<!-- /@w --></span></samp>’ at the head of the file. This 81‘<samp><span class="samp">#pragma</span></samp>’ must appear before any functions that throw or catch 82exceptions, or run destructors when exceptions are thrown through them. 83 84 <p>You cannot mix Java and C++ exceptions in the same translation unit. It 85is believed to be safe to throw a C++ exception from one file through 86another file compiled for the Java exception model, or vice versa, but 87there may be bugs in this area. 88 89 </body></html> 90 91