CPP 1.2 NO IDEA Avatar
  1. OMG Issue

CPP12 — Escaped keyword mapping?

  • Key: CPP12-9
  • Legacy Issue Number: 4498
  • Status: closed  
  • Source: Triodia Technologies Pty Ltd ( Michi Henning)
  • Summary:

    the mapping says in section 1.1.2:

    To avoid C++ compilation problems, every use in OMG IDL of a
    C++ keyword as an identifier is mapped into the same name preceded
    by the prefix "cxx." For example, an IDL interface named "try"
    would be named "_cxx_try" when its name is mapped into C++.
    For consistency, this rule also applies to identifiers that
    are derived from IDL identifiers. For example, an IDL interface
    "try" generates the names "_cxx_try_var" and "cxx_try_ptr,"
    ^^^^^^^^^^^
    that is, the IDL compiler behaves as if the interface were
    names "cxx_try" and then applies the normal mapping rules.
    ^ ^^^^^^^

    Four issues here:

    1) I think we have a typo at the first place I highlighed. I
    believe it should be "_cxx_try_ptr". (The leading underscore
    is missing in the text as it stands now.)

    2) Typo: It should be '...were named "cxx_try"', not
    '... were names "cxx_try"'

    3) To state that the compiler behaves is if the interface were
    named "cxx_try" doesn't explain where the additional leading
    underscore comes from because we get cxx, not cxx_
    for the mapped identifiers.

    Unfortunately, changing this sentence to state that the compiler
    behaves as if the interface were named "_cxx_try" won't fix
    it, because the leading underscore would be dropped by the
    IDL keyword escape mechanism.

    4) The explanations are insufficient:

    interface try {};

    This will result in "_cxx_try" as the interface name. But what
    about the generated tc type code constant? It could be:

    a) _cxx_tc_try

    This mapping would be consistent with the statement that
    the "cxx" is a prefix.

    b) cxx_tc_try

    Same as above but, given that, normally, the tc type code
    constants already start with an underscore, the escaped
    mapping results in a double underscore.

    c) _tc_cxx_try

    This mapping would be consistent with the directive to map
    as if the type were named "cxx_try".

    d) tc_cxx_try

    Same as above but preserves the underscore for both the
    "tc" and the "cxx", resulting in a double underscore.

    To me, interpretation (d) seems the most natural and intuitive because
    it preserves the leading "tc" for all type code constants (including ones
    for identifiers that are C++ keywords). Also, if the mapping of the type
    is to "_cxx_try", then it makes sense to have the double underscore because
    that is consistent and doesn't make an exception to the rule of "use
    "tc" for type code constants and "cxx" for IDL identifiers that are
    C++ keywords."

    Proposal:

    Rewrite the above para to read:

    To avoid C++ compilation problems, every use in OMG IDL of a
    C++ keyword as an identifier is mapped into the same name preceded
    by the prefix "cxx." For example, an IDL interface named "try"
    would be named "_cxx_try" when its name is mapped into C++.
    For consistency, this rule also applies to identifiers that
    are derived from IDL identifiers. For example, an IDL interface
    "try" generates the names "_cxx_try_var," "_cxx_try_ptr,"
    and "tc_cxx_try".

  • Reported: CPP 1.1 — Thu, 16 Aug 2001 04:00 GMT
  • Disposition: Resolved — CPP 1.2
  • Disposition Summary:

    accept the suggested proposal

  • Updated: Fri, 6 Mar 2015 20:57 GMT