Clarification needed for 18.6.4: terminate() and uncaught_excaption()

From:

Eric Niebler <eric@boost-consulting.com>

Newsgroups:

comp.std.c++

Date:

Mon, 6 Aug 2007 17:16:54 CST

Message-ID:

<46b79cd8$0$503$815e3792@news.qwest.net>

The question is regarding the behavior of the following program.

     #include <cstdio>
     #include <cstdlib>
     #include <exception>

     struct E {};

     void t()
     {
         if (!std::uncaught_exception())
             std::printf("HERE\n");
         std::exit(0);
     }

     int main()
     {
         E e;
         std::set_terminate(&t);
         throw e;
     }

Should it print "HERE"? This is the relevant part of the standard
(18.6.4, or for those looking at the working paper, 18.7.4):

   bool uncaught_exception() throw();

   Returns: true after completing evaluation of a
   throw-expression until either completing
   initialization of the exception-declaration in
   the matching handler or entering unexpected()
   due to the throw; or after entering terminate()
   for any reason other than an explicit call to
   terminate().

I can read this two ways:

1) Returns true after <blah> or after entering terminate() ...
2) Returns true after <blah> until either ... or after entering
terminate() ...

If I choose the second reading, the program should print "HERE". If I
choose the first, it shouldn't. What is the intention?

FWIW, the compilers I have available to me (metrowerks, visual c++, g++)
seem to agree with the second reading, but a well-respected conformance
testing suite interprets this the other way.

--
Eric Niebler
Boost Consulting
www.boost-consulting.com

The Astoria Seminar ==> http://www.astoriaseminar.com

---
[ comp.std.c++ is moderated. To submit articles, try just posting with ]
[ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ]
[ --- Please see the FAQ before posting. --- ]
[ FAQ: http://www.comeaucomputing.com/csc/faq.html ]