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  1. OMG Issue

CPP12 — Server-side exception specifications and ISO C++ std::exception

  • Key: CPP12-40
  • Legacy Issue Number: 4265
  • Status: closed  
  • Source: ZeroC ( Bernard Normier)
  • Summary:

    In CORBA C++ 2.4 and before, the exception specification of generated
    POA skeleton member functions is CORBA::SystemException plus the mapped C++
    class for exceptions specified in the raise expression of the corresponding
    IDL operation [see CORBA C++ 2.4 paragraph 23.27].
    As a result, a servant programmer needs to convert any exception other than
    those in the exception specification to one in the exception specification
    – else the C++ runtime will call std::unexpected() if an unexpected
    exception is thrown.

    This makes exception handling on the server-side quite painful:
    for example if a servant programmer calls operator new(), s/he's supposed
    to catch std::bad_alloc and convert it to CORBA::NO_MEMORY. Similarly,
    if s/he uses any of the ISO C++ libraries, s/he's supposed to convert the
    std::exception objects raised by the library into CORBA::SystemExceptions,
    or user-defined IDL exceptions.

    Given that C++ compilers provide more and more features of ISO C++,
    in particular the standard libraries, this is a real world issue!


    Add std::exception in the exception specification of generated
    POA-skeleton member functions. The POA (or POA skeleton) implementation
    is responsible to perform the following conversions:
    std::bad_alloc to CORBA::NO_MEMORY
    other std::exception to CORBA::UNKNOWN (see in CORBA 2.3 core)

    Source-code backward-compatibility
    I propose to make exception specifications in generated skeletons a bit
    less restrictive than they were in CORBA C++ 2.4 (and before).
    C++ servants written with the CORBA C++ 2.4 (and before) mapping do not
    require any change – their exception specifications will be more
    restrictive than required by the new mapping, which is perfectly correct.

    It does not affect interoperability: only CORBA exceptions go on the
    wire. An ORB-mediated operation can only raise a CORBA::SystemException
    or a user-defined IDL exception.

    Alternative Mapping for C++ Dialects
    Unfortunately, not all C++ compilers comply (or almost comply) with
    ISO C+. With such a "C+ compiler", the ORB/POA implementation will
    behave as in CORBA C++ 2.4 (i.e. no std::exception is the exception
    specification). Or maybe we can allow the ORB/POA to add an
    implementation-dependent class in the generated exception

    Portable user-written servants will simply include
    CORBA::SystemException (or something more restrictive) in their
    exception specifications.

  • Reported: CPP 1.1 — Wed, 11 Apr 2001 04:00 GMT
  • Disposition: Resolved — CPP 1.2
  • Disposition Summary:

    see below

  • Updated: Fri, 6 Mar 2015 21:38 GMT