Issues for Ada 2003 Revision Task Force

List of issues (green=resolved, yellow=pending Board vote, red=unresolved)

List options: All ; Open Issues only; or Closed Issues only

Issue 733: Ada mapping deficiency - orbos/97-09-26
Issue 734: Ada mapping deficiency - orbos/97-09-26 (2)
Issue 735: Ada mapping deficiency - orbos/97-09-26 (3)
Issue 996: Ada mapping issue
Issue 1112: Ada issue: Type string in package CORBA spec
Issue 1320: Ada and the POA
Issue 1359: Ada Language Mapping: Section 23.5.5, Mapping for Interface
Issue 1387: IDL to Ada Mapping: Ada package CORBA.Object (01)
Issue 1388: Mapping of IDL to Ada: Ada package CORBA.Object
Issue 1504: Chapter 23.2.7 of CORBA 2.2, IDL to Ada Mapping ( pragma Subsystem)
Issue 1702: Nil object reference (CORBA v. 2.2)
Issue 1806: Mapping of structure, union or exception types
Issue 1807: Mapping of sequesnce types
Issue 1808: Mapping for typedef
Issue 1809: Mapping for standard exceptions
Issue 1810: NamedValue in 23.6.1
Issue 1811: TypeCode in 23.6.6
Issue 1812: list_initial_services and resolve_initial_references are missing
Issue 1813: 23.6.8 Object circularities
Issue 1814: Parameter Result in Createrequest cannot be "in out NamedValue
Issue 1818: Mapping of Operations (23.5.9) "Returns" parameter
Issue 1846: 23.5.5 Mapping for Interfaces (Client-Side Specific)
Issue 1856: 23.5.5 Mapping for Interfaces (Client-Side Specific)
Issue 1896: 23.8.1 Package CORBA
Issue 2036: Error in section 21.3.3
Issue 2043: Section 21.8.9: Examples
Issue 2044: The name of the mapped type shall be "Fixed_" prepended
Issue 2095: Suggestion on mapping the OMG IDL language to Ada
Issue 2209: Method for converting an Object to a Ref
Issue 2262: Impl methods should be dispatchable
Issue 2458: Name and scope of instantiation of CORBA.Sequences.{Un}Bounded
Issue 2459: Mapping of operation parameters of same interface type.
Issue 2612: Mapping for String Types - Bounded Strings
Issue 2632: ptc/99-02-02 page 21-5 Server Side, common root type CORBA.Object.Objec
Issue 2649: ptc/99-02-02: Impl side mapping and the POA
Issue 2656: ptc/99-02-02: 21.22.1 Handling Known Types
Issue 2657: 21.2.7 Mapping Summary - Names and Scoping
Issue 2891: CORBA 2.3 Ada, Mapping for Wide String Types
Issue 3627: Inconsistency in the definition of implementation object types.
Issue 3639: The Ada mapping of the Interface Repository.
Issue 3701: narrowing of valuetypes
Issue 3702: tagged types mapped from abstract interfaces
Issue 3703: mapping of IDL factories (initializers) for valuetypes
Issue 3704: ada language mapping specification -- TYPOS
Issue 3705: Addition of a constructor for "empty" Any objects.
Issue 3706: Mapping of CORBA.Request in Ada
Issue 3722: declaration of an UnknownUserException
Issue 3736: Inconsistency in the definition of the location of TC_Object
Issue 5682: Insecurity about literals of typedefed enums
Issue 5768: Concern about the mapping of valuetypes to Ada
Issue 5773: IDL to Ada mapping for valuetypes
Issue 5859: Mapping of reopened modules to Ada
Issue 6344: Ada Mapping of Sequences Too Heavy
Issue 12426: Table 2-1 in section 2.2.4

Issue 733: Ada mapping deficiency - orbos/97-09-26 (ada-rtf)

Summary: Inconsistencies between sections 21.2.1 and 21.7.3. The change from CORBA.Object.Object to CORBA.Implementation_Defined.Object is not reflected in 21.2.1 and 21.7.3. The private section still contains CORBA.Objetc.Object. The context clause  "with CORBA.object" should be changed to "with CORBA.Implementation_Defined"

 closed issue

Summary: The pseude-object specifications in the main body of the text do not match with the appendices. There are differences between specs and appendices include NVlist, Context, TypeCode, BOA, and Object

 closed issue

Summary: Inconsistencies in section 21.5.8 (standard exceptions) and Appendix A1 (package CORBA): Changes to standard exceptions section have not been reflected in Appendix 1A (System_Exception_Members, exception members type) The example exception members type is referred to as Unknown_Members and Unknown_Exception_Members. It is not clear how type Unknown_Members is used

 received issue

Summary: Please refer to Chapter 22 of ptc/98-01-04  and provide Ada language
 mappings for the operations that have been added to CORBA::Object and
 CORBA::ORB from Security Service in Core Revn 2.2 and 2.3.
 Ada Mapping issue

Summary: I have a suggestion regarding the current (CORBA version 2.2) IDL to Ada
 >mapping which concerns the type String in the package CORBA spec. 
 >Here is a diff of the addition that I propose:
 >
 >*** corba.ads.orig	Mon Mar  2 09:38:27 1998
 >--- corba.ads	Wed Mar 25 08:35:28 1998
 >***************
 >*** 29,34 ****
 >--- 29,37 ----
 >     type    Octet          is new Interfaces.Unsigned_8;
 >     type    String         is new Ada.Strings.Unbounded.Unbounded_String;
 >  
 >+    Null_Unbounded_String : constant String
 >+                       := String
 >(Ada.Strings.Unbounded.Null_Unbounded_String);
 >+ 
 >     -- Exceptions
 >  
 >     type IDL_Exception_Members is abstract tagged null record;
 >
 >
 >The lack of the Null_Unbounded_String constant in the current CORBA spec 
 >means it is cumbersome to compare a CORBA.String against the 
 >Ada.Strings.Unbounded.Null_Unbounded_String, as such comparison requires a 
 >type conversion.
 

Summary: The Ada language binding has not been updated to deal with the
 deletion of the BOA and the introduction of the native type for the POA.
 

 received issue

Summary: Ada Language Mapping:  Section 23.5.5, “Mapping for Interfaces”
 
 **The following text is added to the Ada language mapping within section
 23.5.5 at the end of the subsection titled, “Narrowing Object
 References”.**
 
 Narrowing an object reference can require a remote invocation (to either
 the target object or to an Interface Repository) to verify the
 relationship between the actual object and the desired narrow
 interface.  For cases where the application programmer wishes to avoid
 the possibility of this remote invocation, conforming implementations
 must provide a primitive subprogram in each interface package to perform
 an unchecked narrow operation.
 Each interface mapping shall include a function with specification:
 
 function Unchecked_To_Ref(The_Ref : in CORBA.Object.Ref’CLASS) return
 Ref;
 
 Regardless of whether or not The_Ref is known to support the desired
 interface, the provided implementation returns a narrowed reference.
 
 

Summary: I have a few suggestions concerning the Mapping of OMG IDL to 
 Ada (chapter 23 of the CORBA V2.2 spec.)
 
 The C++ mapping in the same document among other defines a class
 Object (see chapter 20.32.2). This class provides a number of
 methods that the equivalent Ada package CORBA.Object (chapter
 23.8.8) does not.
 
 My first suggestion is to supply the verbatim text of the IDL
 interface Object on which the Ada package CORBA.Object is
 based. (This is chapter 20.32.1 in the C++ mapping.)
 

Summary: My further suggestion is to adopt a single IDL specification as 
 the basis for both the C++ and the Ada language mappings for the
 interface Object (and other predefined interfaces). This is in
 the interest of compatibility of programming interfaces.
 
 In particular, I find the following methods lacking in the Ada
 package CORBA.Object that are present in the C++ class Object:
 

Summary:  Chapter 23.2.7 of the CORBA v2.2 Mapping of OMG IDL to Ada
 mentions:
 
 " Files (actually inclusion streams) create a package to contain the
   "bare" definitions defined in IDL"s global scope. The package name
   is formed from the concatenation of the file name and _IDL_File. 
 "
 
 In the absence of a pragma Subsystem, this solution is felt to be
 unsatisfying.

Summary: Section 20.3.5 of the OMG IDL to C++ Mapping states:
 
 " The mapping for an interface defines a static member function 
   named _nil that returns a nil object reference of that interface 
   type [...] "
 
 Although the section "Object Reference Operations" in the OMG IDL 
 to Ada Mapping chapter 23.5.5 defines a function
 
   function Is_Nil (Self : Ref) return Boolean;
 
 the mapping does not define a Nil operation.
 
 

Summary: In the mapping of structure, union or exception types, the same 
 complex_declarator component may occur in two or more structure 
 definitions, the name of the generated types will collide in the 
 proposed mapping. It would be wise to prepend the name of the 
 enclosing structure:   
 mapping of structure, union or exception types

 Close with no change:

Summary: The mapping of the sequence types does not corresponds to the 
 definition of the packages defined in 23.8.12, 23.8.13 and 23.8.14 :
 - with clauses are not correct
 - there is no array type as generic formal parameter
 
 

 Addressed by previousRTF:

Summary: In the mapping for typedef, if the ancestor type is the Object type 
 or an interface, then subtyping should occur in place of derivation.
 This would avoid several difficulties either in the generated code 
 and in the application code.
 

Summary: In the mapping of standard exceptions, ex_body maps to 
 System_Exception_Members which is defined as Ex_Body in the Corba 
 package.
 

Summary: In 23.6.1 NamedValue, the len component is useless and meaningless in 
 Ada.
 

 received issue

Summary: In 23.6.6 TypeCode, the package TypeCode should correspond to the 
 pseudo-IDL given in the CORBA 2 specification.
 

 received issue

Summary: In 23.6.7 ORB, the operations list_initial_services and 
 resolve_initial_references are missing. They need an ORB object to 
 apply to.
 ORB_init is nowhere defined but it could be added to Corba.Orb.
 

Summary: In 23.6.8 Object,
 - there are circularities as Corba.ImplementationDef.Ref and 
 Corba.InterfaceDef.Ref are derived from Corba.Object.Ref. One 
 solution to these circularities is to replace these types by 
 Corba.Object.Ref"class.
 

 Accept with Modification:

Summary: - The parameter Result in CreateRequest cannot be an "in out 
 NamedValue" as the result will be unreachable once the operation has 
 completed. Instead, it should be of an access type to NamedValue.
 

Summary: Section 23.5.9, 2nd paragraph, states that
 
   [...] The non-void result, if any, is returned via an added 
   argument with name "Returns".
 
 The word "added" would seem to imply that the Returns parameter 
 shall appear at the end of the parameter list. However, the 
 standard should be more explicit about the required parameter 
 position of the Returns parameter.
 
 

Summary: 23.5.5 Mapping for Interfaces (Client-Side Specific)
 
 The section "Nil Object Reference" states:
   [...] This mapping relies on the Is_Nil function to detect 
   uninitialized object references, and does require or allow 
   definition of a Nil constant.
 
 Could it be that this should read: "... does NOT require ..." ?
 

Summary: 23.5.5 Mapping for Interfaces (Client-Side Specific)
 
 The section "Object Reference Operations" has some lines in 
 typewriter font:
 
   function Is_Nil(Self : Ref) return Boolean;
 
   procedure Release(Self : Ref"CLASS);
 
 I believe these lines should instead be:
 
   function Is_Nil(Self : Ref"CLASS) return Boolean;
 
   procedure Release(Self : in out Ref"CLASS);
 
 Also, the Release operation is missing from 23.6.8 (Object) 
 and lacking the "CLASS attribute in 23.8.8 (package CORBA.Object)
 
 

Summary: I propose the addition of two functions to the  package CORBA:  function To_CORBA_String (Source :  Standard.String) return CORBA.String;
 function To_Standard_String (Source :  CORBA.String) return Standard.String;  In my opinion, the frequency with which these  conversion functions are 
 needed when dealing with the type CORBA.String  justify their inclusion 
 in the CORBA package.

Summary: Ada"s "not" is not specified for signed integers.
 
 If the table entry is to be read as "for signed integers, use the expression
 -(value-1)", then it would be more obvious, if the check sign appeared in
 the second line (where the expression is), not in the first line (where the
 not operator is).
 
 At least a comment seems appropriate.
 

Summary: Section 21.8.9:
 
 Example Chicken.idl:
 
 Freezing rules (ARM 13.14) cause the packages Egg and Chicken to be illegal.
 The declaration of
   function To_Ref (The_Ref : in Corba.Object.Ref"Class) return Ref;
 has to occur before the declaration of
     package Convert is new Egg/Chicken_Forward.Convert (Ref);
 ARM 13.14(5,16).
 
 
 Example Tank:
 
 package Tank is
 
   type Ref is new Vehicle.Ref with record
     Mixin: Asset.Ref;
   end record;
 
 If I"m not missing something fundamental, this mixin is needed to allow
 reference to Asset.Op1/2.
 

 in Corba.Object.Ref"Class) return Ref;

Summary: Section 21.10:
 
 The name of the mapped type shall be "Fixed_" prepended [rather than
 appended] to the IDL specified number of digits, ...
 

Summary: This is a suggestion for consideration by the Ada Revision Task Force.
 
 
 Experience with the IDL to Ada mapping (OMG Document 95-5-16) 
 convention for generating distinct types for each IDL typedef leads me to 
 suggest that generating a distinct Ada type for each IDL typedef results in 
 numerous types which might more clearly be generated as subtypes of a single 
 (family of) types.
 

Summary: The Ada mapping lacks a method for converting an 
 implementation side Object to the corresponding 
 proxy side Ref. The C++ mapping defines a method, 
 _this(), for this purpose (see CORBA V2.2 chapter 
 20.34.2.)
 
 I propose the addition in the code generated for an 
 interface A, in package A.Impl:
 
    function To_Ref (Self : access Object) return Ref;
 

Summary: I suggest that the IDL to Ada mapping standard specifically 
 mention that Impl side methods be dispatching. In order to 
 achieve this, the Impl package spec generated for an 
 interface A should contain the marked declaration:
 
 with POA_A;
 package A.Impl is
    type Object is new POA_A.Object with private;
    -------- ADDITION :
    type Object_Access is access all Object"Class;
    -------- END OF ADDITION
 
    -- example method:
    procedure Meth (Self : access Object);
 
 end A.Impl;
 

Summary: CORBA V2.2 section 23.5.6, Mapping for Sequence Types, 
 states that
 
 " The name and scope of the instantiation
   [of CORBA.Sequences.Bounded or CORBA.Sequences.Unbounded]
   is left implementation defined. "
 
 However, the drawing.idl mapping example in the same section 
 suggests that
 
 1) the name of the instantiation be the simple_type_spec 
    with "IDL_SEQUENCE_" prepended
 
 2) the instantiation be located within the same scope as 
    the corresponding IDL sequence type declaration.
    (This could be expanded to state that if the sequence 
    type declaration appears at the IDL file scope level, 
    then the instantation shall appear within the 
    synthesized IDL_FILE_ package.)
 

Summary: It is a natural consequence of the Ada language rules that an operation
 parameter of the same interface type, other than the implied parameter,
 must be mapped to a class-wide reference type. The Ada language rules
 disallow two controlling parameters, and the first added Ref parameter must
 be the controlling parameter. So, for an operation that has an implicit
 parameter of the enclosing interface, a special mapping rule is needed so
 that the operation is not primitive on that parameter. 
 

Summary: It should be clarified that mentions of the type String in this 
 package refer to Standard.String. Being a child package of package 
 CORBA, the type String in CORBA.Bounded_Strings otherwise refers to 
 the type CORBA.String.
 

Summary: The Ada RTF submission for the CORBA 2.4 Ada Mapping, 
 document ptc/99-02-02, under section 21.2.1 Interfaces 
 and Tagged Types, Server Side, states
 
 " The package contains a declaration for the Object 
   type, derived from the parent interface"s object type 
   or from a common root, CORBA.Object.Object, [...] "
 
 The common root type should be PortableServer.Servant_Base.
 
 

Summary: Has the Ada RTF considered the generation of a POA_<interface_name> 
 package for the Impl side mapping? 
 
 This is the approach taken by the C and C++ mappings, and has 
 the advantage of keeping the Impl package completely free of 
 code required by the ORB.
 

Summary: Issue Type: Editorial
 
 21.22.1 Mapping for Any Type - Handling Known Types 
 has:
 
   function Get_Type (The_Any : in Any) return TypeCode.Ref;
 
 The return type should be TypeCode.Object
 

Summary: Delete the paragraph:
 
 " This mapping supports the introduction of a subsystem name 
   that serves as a root virtual module for all declarations 
   in one or more files. When specified, subsystems create a 
   library package. "
 
 The concept of subsystem is nowhere further explained.
 I believe this might be a remainder from the time when the 
 #pragma Subsystem was supported.
 
 

Summary: At the end of section 1.17 of the 99-07-29 document,
 there is:
 
   type WTitle is new CORBA.Bounded_Wide_String_512.Bounded_String;
 
 The wide string type should be Bounded_Wide_String if 
 the CORBA.Bounded_Wide_Strings package is to have the 
 same specification as 
 Ada.Strings.Wide_Bounded.Generic_Bounded_Length.
 

	4.4.2 "Base types" specifies that PortableServer.Servant_Base
	and CORBA.Value.Impl_Base shall inherit from CORBA.Impl.Object.

	5.2.3 "CORBA.Value.Base" and 5.2.6 "PortableServer.Servant_Base"
	show both types as "abstract tagged null record"s. This contradicts
	the aforementioned provision.

	The following revision is proposed to resolve this issue:
	- In 5.2.3 "CORBA.Value.Base" define type Impl_Base as
           "type Impl_Base is abstract new CORBA.Impl.Object with private;"
	- In 5.2.6 "PortableServer.Servant_Base", define type Servant_Base as
           "type Servant_Base is abstract new CORBA.Impl.Object with private;"

Summary: Standardisation of the declaration of the Ada units mapping the
        Interface Repository Specification

Description:
	The mapping of the IDL specification of the IR in Ada implies
	the creation of forward declarations of interfaces (the
	"IDLType" interface for instance). Those should be mapped in
	Ada to subpackages of CORBA using the CORBA.Forward
	package. This leads to a circular dependency in the new CORBA
	package.

Proposed solution:
        These interfaces cannot be mapped as instanciations of
        CORBA.Forward that are child packages of CORBA, because
        they are subsequently used in the definition of record
        types in the declaration of CORBA (eg interface IDLType
        as a component of StructMember).

	We therefore propose the following addition to the standard
        mapping definition for module CORBA:

        "The types defined within module CORBA by the Interface
        Repository Specification (formal/99-10-07, p10-56 to 10-68),
        except the TypeCode and ORB interfaces, shall be mapped to a
        (child) library package CORBA.Repository_Root." 

	A comment at the end of the declaration of the package CORBA
	implies that this is probably the intent of the author to
	provide such a standard child unit. 

	We further propose that the contents of the declaration of
	child package CORBA.Repository_Root be standardized. We will
	provide a proposed specification on request.

Paragraph 5.2.6 of CORBA v2.3.1 specifies that "value type
instances may be widened/narrowed to other value types. Each language
mapping is responsible for specifying how these operations are made
available to the programmer."  Ada mapping v1.2 specifies a
To_Abstract_Value function to widen a value type to an abstract value
type (paragraph 1.10.2.2). The same document reads that concrete value
types may be widened to other concrete value types using ada's view
conversion (paragraph 1.10.2.3). However, nothing is specified to
support narrowing of value types (concrete or abstract) to inheriting
concrete value types.

Proposed solution: We propose the definition of a To_Value_Ref function
in the helper package associated with the value type, with the following
signature:
function To_Value_Ref
   (From : in CORBA.Value.Base'Class)
    return Value_Ref;

The semantic of this function would be to cast the object reference
passed as a paramater to a reference of the current interface, if it
is legal. Otherwise, this function would raise CORBA.Bad_Param.

The current Ada mapping specifies that ada Abstract_Ref types
	mapped from IDL abstract interfaces should inherit directly
	from CORBA.AbstractBase.Ref, and not from CORBA.Object.Ref.

	It seems more natural to us to make Abstract_Ref types inherit
	from CORBA.Object.Ref. Otherwise, these Abstract_Ref tagged
	types would not inherit thr primitives of CORBA.Object.Ref
	(Is_A, Is_Equivalent, Hash)

Description: section 4.5.5 of the ada mapping specifies that IDL
initializers have to be mapped into Ada functions. It reads "Thus they
will be primitive on the value reference type". For example,

// IDL
valuetype VT {
factory create(in long l);
}

is mapped into

// ada
package VT is
type Value_Ref is ...
function VT (l : in CORBA.Long) return Value_Ref;
end VT;

The fact that these functions be primitives implies that they have to
be overriden for each inheriting valuetype. This implies code
rewriting, with unprecise semantics: what should the semantic of the
overriding function be ?

Therefore, we suggest that the return type of the function be a
Value_Ref'Class, so that these functions are not primitives, and do
not have to be overriden.

page 1.14, end of page:
new PortableServer.Servant
should be
new PortableServer.ServantBase


p 4.22, beginning of section 4.9.1,
CORBA.Value_Forward
should be
CORBA.Value.Forward

 There is at this moment no way of creating an Any with a given 
type but no value. This is however helpfull (if not needed) when 
creating the Any passed (through a NamedValue) as the result parameter 
of the CORBA.create_request method. I suggest to add a constructor for 
Any objects with the following syntax :
package CORBA {
  function Get_Empty_Any (Tc : in TypeCode.Object) return Any;
};

Modification of the IDL specification of the CORBA.Object 
package in order to include another way of creating Requests.
         Addition of two new interfaces : ExceptionList and ContextList.
         Modification of the CORBA.Request package to allow the user to 
set the result type.

Description:
	The mapping of the IDL specification of the CORBA.Object package in 

Ada provides a single way of creating requests through the 
create_request procedure. This procedure does not take into account the 
context nor the exception possibly returned by the method invoked. 
Therefore I suggest to add a new create_request procedure whose Ada 
specification is :

   procedure Create_Request
     (Self      : in     CORBA.AbstractBase.Ref;
      Ctx       : in     CORBA.Context.Ref;
      Operation : in     Identifier;
      Arg_List  : in     CORBA.NVList.Ref;
      Result    : in out NamedValue;
      Exc_List  : in     ExceptionList;
      Ctxt_List : in     ContextList;
      Request   :    out CORBA.Request.Object;
      Req_Flags : in     Flags);

The specification of the types ExceptionList and ContextList are mapped 
from the following pseudo Idl :

interface ExceptionList {
  readonly attribute unsigned long count;
  void add(in TypeCode exc);
  TypeCode item(in unsigned long index) raises(Bounds);
  void remove(in unsigned long index) raises(Bounds);
};

pseudo interface ContextList {
  readonly attribute unsigned long count;
  void add(in string ctxt);
  string item(in unsigned long index) raises(Bounds);
  void remove(in unsigned long index) raises(Bounds);
};

In addition, a method is missing in the package CORBA.Request to allow 
the user to set the result type if he passed a null NamedValue at 
creation of the request. I suggest to add the following method in 
CORBA.Request :

package CORBA.request {
  procedure Set_Return_Type (CORBA.TypeCode.Object Tc);
};

The dynamic invocation interface does not provide a way of raising 
the exception potentially returned by a dynamic call. We thus propose to 


add the following definitions in the CORBA package :

   UnknownUserException : exception;
   type UnknownUserException_Members is
     new CORBA.IDL_Exception_Members with record
       IDL_Exception : CORBA.Any;
     end record;

   procedure Get_Members
     (From : Ada.Exceptions.Exception_Occurrence;
      To   : out UnknownUserException_Members);

corresponding to the following pseudoIDL :

exception UnknownUserException { any _Exception; };

A CORBA implementation for Ada 95 must provide a typecode constant
	for predefined type Object. This typecode constant is a function
	"function TC_Object return CORBA.TypeCode.Object".

	According to the standard declaration of package CORBA
	(5.4 CORBA package), "function TC_Object is in CORBA.Object".

	According to the standard declaration of package CORBA.Object
	(5.2.2 Object), package CORBA.Object does not contain any such
	declaration.

	Thus we claim that there exist an inconsistency in the definition
	of the location of function TC_Object.

	The proposed resolution of this issue is to define a standard
	location for funtion TC_Object. For consistency with user-defined
	interfaces, we propose that a new standard package CORBA.Object.Helper
	be defined, containing the declaration of function TC_Object.
	We propose that the declaration of package CORBA be updated to
	mention that function TC_Object is in CORBA.Object.Helper.

Description:


Given the declarations


 module m_a {
   enum enum_a { value_1, value_2 };
 };
 module m_b {
   typedef m_a::enum_a enum_b;
 };


I believe the following is illegal:


 const m_b::enum_b bconst = m_b::value_2;


Instead, to define such a constant in IDL, one needs to write


 const m_b::enum_b bconst = m_a::value_2;


However, when mapping the typedefed enum to Ada, a derived type is 
created.
The derived type implicitly creates visibility of the enum literals 
in the new scope (in this example, module m_b). 
Furthermore, enum_a and enum_b are not assignment-compatible in Ada.


A clarification should be added to the Ada mapping stating that
all mentions of scope prefixes at enum literals must be converted to 
match the Ada rules.
Thus the above example


 const m_b::enum_b bconst = m_a::value_2;


must be mapped as follows to Ada:


 bconst : constant m_b.enum_b := m_b.value_2;

The IDL to Ada mapping version 1.2 (01-10-42) of valuetypes
causes serious problems when combined with other IDL constructs.
 
Here is an example:


// file: my_module.idl
module my_module {
 
   valuetype vtype {
      public short member;
   };
 
   typedef vtype array_of_vtype[10];
 
/* Further sources of problems:
 *
   struct struct_with_vtype {
      vtype smember;
   };
 
   union union_with_vtype switch (boolean) {
      case true:
         vtype umember;
   };
 */
 
};
 
The array_of_vtype cannot be mapped to Ada, neither can the
struct_with_vtype or union_with_vtype.
 
I propose a change to the mapping for valuetypes as follows:
 
" A valuetype shall be mapped to a package, or a nested package
  when the valuetype is declared within a module. "


For clarity, here is the mapping that I propose for the above
example:


-- file: my_module.ads
with CORBA.Value;


package my_module is


   package vtype is


      type Value_Ref is new CORBA.Value.Base with null record;


      Null_Value : constant Value_Ref;


      procedure Set_member
        (Self : in Value_Ref;
         To : in CORBA.Short);


      function Get_member
        (Self : in Value_Ref)
         return CORBA.Short;


   private
      -- elided
   end vtype;


   type array_of_vtype is array (0 .. 9) of vtype.Value_Ref;


end my_module;


The change of mapping also affects the naming rules for the
generated Value_Impl package because in Ada, it is not possible
to formulate child packages of nested packages.
I propose the following naming scheme for the Value_Impl
package:


The name of the Value_Impl package be formed from the name
of the value type mapped package with "_Value_Impl" appended.


Thus, the name of the Value_Impl package for the above example
would be: my_module.vtype_Value_Impl.

The version 1.2 IDL to Ada mapping specification (01-10-42)
maps concrete valuetypes into two classes:
1. the class hosted in a package with the mapped name of the
   IDL valuetype, and
2. a child package of this package named Value_Impl.


These two classes are separate and incompatible both in their
controlling types (their inheritance graphs are unrelated)
and operations (class 1 uses "in Value_Ref" for the controlling
parameter while class 2 uses "access Object" for the controlling
parameter.)


It is felt that this design choice is not sufficiently explained.


In particular, it is not obvious why class 2 is not derived from
class 1, and it is not explained why the signatures of the mapped
operations are incompatible between the two classes.


===================
Further Elaboration


Other language mappings, such as the IDL to C++ mapping, choose
to make the two classes compatible: Class 2 inherits from class 1,
and the mapped operations in class 2 override those in class 1 
(i.e. they have compatible signatures.)


The "Package Pattern for Mapping" (4.4.1) treats valuetypes the
same as interfaces. However, the distinct "proxy" and "impl"
pattern applied to valuetypes makes necessary extra "Set" operations
for associating implementation values with the "proxy" values.
The programming of applications is encumbered by the need to cater
to two distinct types.


During the design of the Ada mapping for valuetypes, has it been
considered to have the Value_Impl class inherit from the valuetype-
mapped package? (The type Object could perhaps originate in the
valuetype-mapped package, the type Value_Ref could be a classwide
access to Object, and the methods in that package could have
signatures like those in the Value_Impl package.)
What were the reasons for not adopting such a mapping?

The IDL to Ada mapping specification version 1.2 (01-10-42)
does not mention how to map reopened IDL modules to Ada.

The current mapping of IDL sequences to the Ada language results in a instantiation of a defined generic package. However, each instantiation results in roughly 150K of additional object code. This is excessive for embedded systems, especially if multiple sequences are used in an application. A lightweight alternative, such as the mapping defined for C++, should be defined.

Table 2-1 in section 2.2.4 contains a couple of columns labelled "Applicable to". However the entries in the columes are the number "4". (These are probably meant to be check marks.)