Re: exception raised in destructor

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Mon, 6 Aug 2007 14:22:54 -0400

Message-ID:

<f97ott$fju$1@news.datemas.de>

puzzlecracker wrote:

BTW, how can you have two active exception
at the same time?

I can't.

Is it not possible, even in theory, to have two or more active
exceptions simultaneously? I read somewhere - in effective c++ or
exceptional c++, don't remember exactly - where an author listed
circumstances where it was possible.

OK, it's possible. If any destructor during execution of its code
encounters any exception, it better catch it itself. At the time
between throwing such exception and catching it in the destructor
itself, there will be two exceptions "active" simultaneously. Here
is a contrived example:

    void foo() throw(int) {
        static int a = 42;
        throw a++;
    }

    #include <iostream>

    struct A {
        ~A() {
            try {
                foo();
            }
            catch (int i) {
                std::cout << "caught " << i << " in ~A()\n";
            }
        }
    };

    int main() {
        try {
            A a;
            foo();
        }
        catch (int i) {
            std::cout << "caught " << i << " in main()\n";
        }
    }

V
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