GNU Info

(gcc-300.info)Java Exceptions

---

Next: Deprecated Features Prev: C++ Attributes Up: C++ Extensions

---

Enter node , (file) or (file)node

Java Exceptions
===============

   The Java language uses a slightly different exception handling model
from C++.  Normally, GNU C++ will automatically detect when you are
writing C++ code that uses Java exceptions, and handle them
appropriately.  However, if C++ code only needs to execute destructors
when Java exceptions are thrown through it, GCC will guess incorrectly.
Sample problematic code:

       struct S { ~S(); };
       extern void bar();    // is implemented in Java and may throw exceptions
       void foo()
       {
         S s;
         bar();
       }

The usual effect of an incorrect guess is a link failure, complaining of
a missing routine called `__gxx_personality_v0'.

   You can inform the compiler that Java exceptions are to be used in a
translation unit, irrespective of what it might think, by writing
`#pragma GCC java_exceptions' at the head of the file.  This `#pragma'
must appear before any functions that throw or catch exceptions, or run
destructors when exceptions are thrown through them.

   You cannot mix Java and C++ exceptions in the same translation unit.
It is believed to be safe to throw a C++ exception from one file
through another file compiled for the for the Java exception model, or
vice versa, but there may be bugs in this area.