Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!brunix!sdm
From: sdm@cs.brown.edu (Scott Meyers)
Newsgroups: comp.lang.c++
Subject: Exception Handling
Message-ID: <62297@brunix.UUCP>
Date: 23 Jan 91 14:39:28 GMT
Sender: news@brunix.UUCP
Reply-To: sdm@cs.brown.edu (Scott Meyers)
Organization: Brown University Department of Computer Science
Lines: 55

I'm trying to understand the proposed exception handling mechanism, and
since I don't have access to an implementation, I have a couple of
questions about exceptions, especially as regards constructors.  Consider:

    class NoMoreMemory { ... };    // one class of exceptions
    class OtherException { ... };  // another class of exceptions

    // a class where the constructor may raise exceptions
    class Foo {
      public:
        Foo() throw (NoMoreMemeory, OtherException);
    };

    // a global object whose construction may raise exceptions
    Foo globalFoo;    

    // a function with local objects that may raise exceptions
    void f()
    {
      Foo local1;

      try {
        Foo local2;
      }
      catch (NoMoreMemory) { /* do something */ }
      catch (OtherException) { /* do something else */ }
    }

Is it true that:

    1.  There is no way to catch exceptions raised during the construction
        of globalFoo except via calls to set_unexpected?

    2.  f cannot catch exceptions raised during the construction of local1
        because that declaration isn't in a try block?

    3.  Any function can be declared to raise an exception, including
        operators new and delete and class destructors?

    4.  Assuming that it is legal for destructors to raise exceptions,
        you may get different behavior from such a destructor depending on
        whether it is called "normally" or as part of the stack unwinding
        process during the handling of another exception (ARM 15.6.1c)?

Also, speaking of implementations, what's the state of g++ exception
handling these days -- does it implement something akin to that described
in chapter 15 of the ARM?

Thanks,

Scott


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