Is it legal in C++ to have the same catch handler twice? For example

try {
} catch(const ExceptionClass& ex) {
    // ...
} catch(const ExceptionClass& ex) {
  // same as previous. never executed
}

I think the code is legal. I have not found any such restrictions in the
draft standard. I do not have a copy of the final standard.The draft
metions:

"15.3 Handlers for a try block are tried in order of appearance. This
makes it possible to write handlers that can never be executed, for
example by placing a handler for a derived class after a handler for a
corresponding base class."

Someone will probably want to know why I would want to know this. Here
is the reason: This question came up in the pthreads-win32 forum because
the package defines the following catch macro::

>
> I noticed that pthread.h has a macro that defines 'catch'.  (macro
> reproduced here for convenience)
>
> /*
>  * Redefine the C++ catch keyword to ensure that applications
>  * propagate our internal exceptions up to the library's internal
handlers.
>  */
> #define catch(E) \
>          catch(Pthread_exception_cancel) \
>          { \
>             throw; \
>          } \
>          catch(Pthread_exception_exit) \
>          { \
>             throw; \
>          } \
>          catch(E)
>
> This breaks the following legal C++ code (because there will be
multiple
> catch blocks for Pthread_exception_cancel and Pthread_exception_exit):

>
> try {
>     // ...
> }
>
> catch ( some_exception ) { }
>
> catch ( some_other_exception ) { }

Claude

--

Claude Qu=E9zel (claude_quezel@syntell.corba)
anti-spam: replace corba by com in private replies


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