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  1. OMG Issue

CORBA34 — How does DynValue handle derived valuetypes?

  • Key: CORBA34-207
  • Legacy Issue Number: 5467
  • Status: closed  
  • Source: Floorboard Software ( Jonathan Biggar)
  • Summary:

    I just noticed that the description of DynValue is totally silent on the
    issue of derived valuetypes.

    Here's an example to set things up:

    // IDL

    valuetype A

    { public short s; }

    ;

    valuetype B

    { public long l; }

    ;

    struct S

    { A an_a; }

    ;

    // C++

    DynamicAny::DynFactory df = ...;
    B *b = ...;
    S my_s;
    CORBA::Any my_any;

    s.an_a = b;
    my_any <<= s;

    DynamicAny::DynAny_var da = df->create_dyn_any(my_any);
    DynamicAny::DynStruct_var ds = DynamicAny::DynStruct::_narrow(da);

    ds->seek(0);
    da = ds->current_component();

    DynamicAny::DynValue_var dv = DynamicAny::DynValue::_narrow(da);
    CORBA::TypeCode_var tc = dv->type();

    cout << tc->id() << endl;

    -----------

    Now some questions:

    1. What is printed by the above C++ code? "IDL:A:1.0" or "IDL:B:1.0"?

    2. If the typecode is for valuetype A, what happens to the members
    defined in valuetype B? Seems they must be inaccessable yet still
    recoverable if I convert the DynValue back to an any and extract the
    value, because I can't truncate a B to an A.

    3. If the typecode is for valuetype B, we now have the interesting case
    where:

    tc->equivalent(ds->type()->member_type(0))

    is false. Is this going to confuse programmers or programs? I think it
    will, since it means that if I try to insert dv into another DynStruct
    via assign() or the like, it will fail, since the TypeCodes are no
    longer equivalent.

    4. Do the answers change if B is truncatable and the program can find
    the TypeCode for B (perhaps via SendingContextRunTime)? How about if it
    can't find the TypeCode?

  • Reported: CORBA 3.0 — Tue, 16 Jul 2002 04:00 GMT
  • Disposition: Deferred — CORBA 3.4
  • Disposition Summary:

    Deferred

    This proposal was generated automatically by request of the Task Force Chair Adam Mitz.

  • Updated: Mon, 30 Mar 2020 19:47 GMT