The spec maps a constant within an IDL interface to a constexpr member, but this doesn't compile:

i.cpp:8:1: error: non-static data member ‘PI’ declared ‘constexpr’
8 | constexpr double PI = 3.14;

the code examples use = and {} to initialize the constants, recommend to make this consistent by always using {}

The spec in 7.4 says that only basic types/enum should be passed by value for an in argument, but that should also include all shared_ptr types, see https://herbsutter.com/2013/06/05/gotw-91-solution-smart-pointer-parameters/ for some information (more can be found on the internet).

Should the C++ mapping document specify that @value annotations, if specified for one field, MUST be used on all fields.

A link is broken, it mentions:

Maps shall provide the following specializations for the type traits defined in Clause Error: Reference source not found:

The mapping of external in this section is not similar to 7.17.4. In 7.17.4 it is a std::shared_ptr, so a pointer to something which is shared, when copying the struct where the external is a member of the external data will not be copied, just a refcount increment, but in D2.3.4 it is descriibed that when the struct which contains the external member is copied a deep copy is done. Also what is exactly "copy functions", is that the copy constructor or something else? This looks very unspecified, the user doesn't know the exact API and the semantics should be the same as in 7.17.4

The text:
"Inherits std::integral_constant<uint32_t, b> where b indicates
the bit_bound of the bitmask."

should instead state

Defines value - Where the value is mapped as the underlying bit_bound of the bit mask.

Given this is the old CORBA style, wouldn't it be more consistent to use CORBA::TinyShort and CORBA::UTinyShort, that matches the other types as defined in D.2.1.5

As far as I understand it enum_prefix/enum_postfix are a way to change the enum mapping but I don't understand why, because the enums itself are added to the enclosing module, so the following IDL is already illegal, red can't be defined twice
scope. For example the following IDL is illegal

enum Colors { red, green, blue };
enum Colors2 { red, green, blue };

See IDL4.2, chapter 7.5.2, search for "Enumeration value names are introduced into the enclosing scope and then are treated like any other declaration in that

The text describes that the destructor and other constructors are protected, but the example code shows them all public, the C++ code should be updated to match the text

Why does this example code for "C.2.1.2.4 Naming Data Types" map the IDL struct to a C++ class, that is the alternative mapping, but as far as I understand it the mapping prefers to map a IDL struct to a C++ struct by default

For IDL type VT1 the example code is not correct:

• virtual is missing for all pure virtual methods
• a_long_attr is an attribute, so "int32_t& a_long_attr() = 0;" should be removed

The valuetype VT2 is defined in IDL, but the example C++ code is not correct, it says

class VT2 : public virtual VT1 {
public:
virtual void op() = 0;
virtual int32_t third_long() const = 0;
virtual int32_t& third_long() const = 0;
virtual void third_long(int16_t value) = 0;
};

But it should be

class VT2 : public virtual VT1 {
public:
virtual void op() = 0;
virtual int32_t third_long() const = 0;
virtual int32_t& third_long() = 0;
virtual void third_long(int32_t value) = 0;
};

The example for interfaces full lists in IDL the attribute "an_attribute", but the cod example uses "attribute", which is not correct

As all types in the spec are lower case, shouldn't IDL fixed be mapped to C++ fixed (all lower case)

The mapping says "IDL strings shall be mapped to C++ std::string, or to a type named omg::types::string that delivers std::string semantics", but when I now have CORBA and use an interface with operation "void set_string (in string text);", what is now the C++ signature I have to override in my servant implementation, it could be "void set_string(const std::string& text) override;", or "void set_string(const omg::types::string& text) override;" which could lead to portability issues when some vendor uses std::string and another omg::types::string. For defining data it doesn't make a real difference, but it is a problem when using CORBA

In the example code there is "using Length = long;", but long is not portable, shouldn't be this be int32_t?

Can a default annotation be applied to string types (bounded and unbounded)?

The section is silent on maps.

What happens when the following is present in an IDL file:

typedef @min(2) @max(1) long Huh;

Prior to C++20, the following template cannot be instantiated:

template <typename T, const T thingy>
class MyTemplate {};

MyTemplate<double, 5.0> x;

For instance is this legal:

struct S

;

typedef @min(2) long MyMin;
typedef @max(5) MyMin MyMinMax;
typedef @default(3) MyMinMax defaultedMyMinMax;

Each annotation specified, either pre-defined or user-defined/custom, should discuss how it interacts with the IDL4 grammar such that the annotation has the desired effect (e.g. @range on a union).

Not sure where (not necessarily in the noted paragraph) should include a reference to an electronic mapping file as an example. Could also include test sample IDL and corresponding C++ output. This should probably be informational and could also be in an Annex. The key reason is to show the actual transformation as well as a test/verification of the mappings. Perhaps also include versions of tools/compiler used in which the transformations were validated. In addition unit tests could be referenced or included as informative content to the spec.

With C++20 it would be nice when the mapping would specify a module mapping (see https://en.cppreference.com/w/cpp/language/modules).

The spec says " In addition to the methods as described in 6.14, the class has an explicit constructor accepting values for each struct member in the order they are specified in IDL.", all values should be by value, so better it is to day " In addition to the methods as described in 6.14, the class has an explicit constructor accepting values for each struct member by value in the order they are specified in IDL."

The underlying_type traits is maybe something to remove, std::underlying_type does the same at the moment bitmask is implemented using an enum. Also I am doubting whether an enum or enum class is the best mapping, have you tried to implement some user code, there is no operator bool() for example, some for checking if a bit is set we always have to cast. Maybe mapping to a class with operator is easier for the user, or use an enum class with operators.

The bitmask mapping allows misuse and is not really a modern API. At least for the users who map a struct to a class the bitmask mapping could for example use a strong enum (mappping now two bitmasks with the same member name will result in non compiling C++ code), but provide the operators ~, |, &, ^, |=, &=, and ^= to make it safe.

The @value annotation does not fully specify the behavior. That includes:

• The behavior for unannotated values.
• The behavior for repeated values. Is it possible like in C++?

DDS-XTYPES does specify the behavior of @value and such description should be added to IDL:

7.3.1.2.1.5 Enumerated Literal Values
Prior to this specification, it was impossible to indicate that objects of enumerated types could be stored using an integer size other than 32 bits. This specification uses the @bit_bound annotation defined in Sub Clause 8.3.4.1 of [IDL] for this purpose.

It is important to note that the value member of the annotation may take any value from 1 to 32, inclusive, when this annotation is applied to an enumerated type. Furthermore, prior to this specification, it was impossible to provide an explicit value for an enumerated literal. The value was always inferred based on the definition order of the literals. That behavior is still supported. However, additionally, this specification allows enumerated literals to be given explicit custom values, just as they can be in the C and C++ programming
languages. This can be done by means of the @value annotation defined in Sub Clause 8.3.1.5 of [IDL], which may be applied to individual literals.
It is permitted for some literals in an enumerated type to bear the @value annotation while others do not. In such cases, as in C and C++ enumerations, implicit values are assigned in a progression starting from the most-recently specified value (or an implicit value of zero for the first literal, if there is no previous specified value) and adding one with each successive literal.

According to IDL4, annotations like range need to specify the arguments that are set. However, in the example we include for the mapping of @range we don't specify min and max in the arguments.

We need to address that as follows:

struct StructureOfRangedValues {
    @range(min=-10, max=10) long x;
};

Reporting this for bounded sequences, but very likely this has to be addressed for all bounded types. The spec says "NOTE—In any case, bound checking on bounded sequences may be performed at serialization time, raising an
exception or reporting an error if necessary", but this should be more strict to my idea, the bounds check must be performed, and the spec should specify which exception is raised when the bound is not respected

In the example code the destructors in classes that derive from a base should be marked override, not virtual, this applies to

• 6.18.4: Change "virtual ~Example();" to "~Example() override;" and "virtual ~OBV_Example();" to "~OBV_Example() override;"
• 6.20: Change "virtual ~Exception();" to "~Exception() override;" and "virtual ~SystemException();" to "~SystemException() override;"
• 6.25: Change "virtual ~MyLocalIF();" to "~MyLocalIF() override;"
• 6.26.6: Change "virtual ~A_skel ();" to "~A_skel () override;" and "virtual ~A_impl ();" to "~A_impl () override;"
• 6.26.8: Change "virtual ~TIE() = default;" to "~TIE() override = default;"

In the example code it lists
const int16_t& a_short()

This should be a return by value, using `const int16_t` will lead to a compiler warning, so it should be 'int16_t', all accessors should be checked.

As there is no conversion implicit from a std::string_view to a std::string there is no possibility to easily pass now a IDL defined string to an operation expecting an IDL string input, will this mapping proposal work for the users?

This mapping defines the bound as std::integral_constant<size_t, b> but in most compilers size_t is 64bit where sequences/strings are bound to 32bit by IDL, so shouldn't size_t be replaced by uint32_t. If this is changed here, also check all other size_t types in this mapping

This new spec seems to try to support anonymous types (at least it doesn't disallow them like IDL to C++11), but how are then the type traits provided for anonymous types. For example the type

struct TopicA

;

Is there a way for the user to get the IDL traits for bound/is_bounded for the l5s member? If that is not possible for anonymous types this language mapping should make that clear, that anonymous types don't have a type trait.

Keys of maps can be any IDL type. How should the generated C++ code support key comparison of any type?

I find it not very maintainable to extend in this spec silently the IDL to C++11 language mapping. In the v1.7 revision I think all is already mapped, so I propose to remove D.3 completely from this spec

The spec says for bounded strings " For interoperability purposes, implementers shall always define omg::types::bounded_string<N>, which may be declared as an alias to std::string". There is a problem when a bounded string is mapped to just a typedef/using of a std::string. At that moment it is not a distinct type so the traits will not work, as example, when defining this IDL

typedef string<5> bounded_bar1;
typedef string<5> bounded_bar2;

And both map to just std::string, the following code will not work correctly

if (traits<Test::bounded_bar>::is_bounded ()) {}
if (traits<Test::bounded_bar>::bound () == 5) {}

Should the IDL4 grammar specify that @value annotations, if specified for one enum field, MUST be used on all enum fields?
Regardless of whether we make this restriction, the specification should clearly state what happens when one field is annotated, but the next one is not.

In the example code it lists "AnException(int32_t error_code, const char* what)

", but the what argument is not described anywhere, it is not in IDL, where is it coming from?

A few remarks on 7.17.3:

• formatting of code in text is not done
• what is the impact of range when applied to a typedef of a basic type on all argument passing rules when that typedef is passed with a function, stored in an union or exception?
• how should min/max be implemented, shouldn't also omg::types::ranged be used?
• what should be done when min/max but also range are used as annotation?

Spec says:

If the union has a default case, the default constructor shall initialize the discriminator, and the selected
member field following the initialization rules described in Clause 7.2.4.3.1. If it does not, the default
constructor shall initialize the union to the first discriminant value specified in the IDL definition.

But when there is an implicit default member, that should be selected, for example, the example below (

  enum DataType
  {
    dtEmpty,
    dtLong,
    dtShort,
    dtString,
    dtPoint,
    dtTrack,
    dtGlobal
  };

  union Data switch (DataType)
    {
      case dtLong: long longData;
      case dtShort: short shortData;
      case dtString: string stringData;
      case dtPoint: string pointData;
      case dtTrack: string trackData;
      case dtGlobal: string globalData;
      // by default (implicit), empty union
    };

The spec clearly specifies that when a union has an explicit default member, then this member should be chosen in its default constructor. When this is not the case, it would pick the first available case that is listed for its first available member.
However, it makes sense that if there is an implicit default member, then it is picked by the default constructor for the union.
Finally, it should be stated that you cannot overrule in any way what member the default constructor of a union will pick by using the @default annotation on any specific member,

The bit_bound annotation can also be applied to an enum, so add bit_bound/underlying_type also to the enum traits

The

As a OMG IDL user, I have messages that treat NaN or infinity as a significant value. I would like to specify this as a default for a field.

Currently, the OMG IDL specification says that a floating point value must include an integer part. It does not mention how to set or use special floating point values.

Per IEEE-754, there are a few types of NaN. It would be desirable for OMG DDS IDL to interpret NaN as a quiet NaN, which matches C++ and Python.

In ROS-IDL, it would look like this:
float32 float32_nan NaN
float64 float64_nan nan

In ROS 2, I proposed an implementation that sets NaN. In the IDL generator, it creates the following IDL file, which is not supposedly valid according to the standard:

module rosidl_generator_tests {
module msg {
module NanValueConstant_Constants

;
struct NanValueConstant

;
};
};

Can the specification be amended to support NaN, +inf, and -inf? This is blocking implementation in ROS 2.

1.
In table 7.1 5th row (struct is_bounded) right column:

Indicates whether a type is bounded or not.,

→ Remove comma at end.

2.
In section A.1.7.4 TypeCode Replacement, there is a small typo,

Omg::types::ref_type<CORBA::TypeCode> type() const;

The beginning should be omg:: not Omg::.

3.
Section title,
D.2.1.3.3 Bitmask Tye

→ Bitmask Type

4.
In section D.3.1.3.2 Bitsets,

IDL biset types shall be mapped as defined in Clause 7.14.3.2 of this specification.

→ bitset types

it is not clear what the traits is_bounded/bound are for non string/sequence types, for example a long. The spec says the trait is empty, but it is there, what is the value then. When looking at the std traits, it seems better that is_bounded returns false_type (follows https://en.cppreference.com/w/cpp/types/is_bounded_array) and bound returns 0 (follows https://en.cppreference.com/w/cpp/types/rank)

The spec describes that with CORBA an invalid usage of union can result in a CORBA::BAD_PARAM exception, for bounded string/vector also a CORBA::BAD_PARAM, but when not using CORBA when IDL4CSP11-9 is resolved a different exception is thrown for an union (for vector it seems this still has to be added also). When a user now has appliation code that uses IDL defined data types with and without CORBA their exception code is different. In order to achieve portability of user code I think the spec should define a omg::bad_param alias type which maps to CORBA::BAD_PARAM or the selected std exception. That way user code can be written portable when the user has data types defined by IDL and wants to support use cases with and without CORBA

The IDL 4 spec states the default bit_bound is 32 bits the C++ mapping document states:
IDL bitmask declarations shall be mapped to two C++ type names:

• An unscoped enum named <Bitmask>Bits with an explicitly defined underlying type. That underlying type
  is the smallest mapped unsigned integer type that has sufficient bits for the bit_bound of the bitmask:
  uint8_t, for values between 1 and 8; uint16_t for bit_bound values between 9 and 16; uint32_t, for
  values between 17 and 32; and uint64_t for values between 33 and 64. The <Bitmask>Bits enumerators
  are the values defined in the scope of the IDL bitmask, with each enumerator explicitly initialized to its
  corresponding integer value.

Currently only TRUE or FALSE are allowed boolean values, but why not allow true and false (all lower case) as values

The spec should be describe that bitmasks do follow the same argument passing rules as a enum/basic type, for an in argument they should be passed by value. Also for union accessors it should describe that they follow the enum rules

The spec is silent about the relationship between min/max/range annotations and the default value. When I have an unsigned long and define min=10/max=20, is that legal without specifying a default value annotation? The default of an unsigned long is zero, so what should be generated in the code now as default? Or should the spec say that when min/max/range are used and the default value of the type is not in the range of those default should be specified by the user?

For anyone using the class mapping of a structure the spec should also provide a class mapping for a bitset, that way they have a consistent API. Also why is a inherited bitset not mapped to C++ inheritance, by removing the inheritance the inheritance relation can't be used in C++ also

The IDL 4.2 page has a download link for the spec as published as an ISO: https://www.omg.org/spec/IDL/ISO/19516/PDF

All (?? - verification left as an exercise but there's 926 instances) the internal document links look to be screwy.

Search for e.g. "Reference source not found"

An example (from page 102):

Annex A
Consolidated IDL Grammar
This annex gathers all the rules from all the building blocks.
Error! Reference source not found.:
Error! Reference source not found. Error! Reference source not found.
Error! Reference source not found. Error! Reference source not found.
Error! Reference source not found. Error! Reference source not found.
... etc...

The mapping for alternative struct mapping is lacking the constructors, member initialization, non-const accessors, description of how it works when using IDL4 struct inheritance, etc, see the IDL to C++11 language mapping for a full description

For all c++ code in this chapter the destructor should be override, not virtual

The raise operation should be _raise, that way any derived user exception can have a raise member, similar to _name and _rep_id. Looks an oversight when adding the code from TAOX11, we use _raise always there

The data retrieval of described rules of constants entity during document compilation failed.

With a bitset/bitfield I assume you can use @default to specify a default value, would be nice if a binary constant could be used, as with C++, a binary constant consists of a sequence of ‘0’ and ‘1’ digits, prefixed by ‘0b’ or ‘0B’ for example 0b101010

IDL 4.2 says for bitset the following, but to our idea the IDL spec goes to far, how the data is organized in memory is something IDL can't enforce, probably not all programming languages provide such a direct way to control the memory layout. Middleware could control how a bitset is transferred on the wire, but I think IDL should not enforce the layout

Bit sets are sequences of bits stored optimally and organized in concatenated addressable pieces called bit fields,
themselves stored optimally. "Stored optimally" means that one bit uses just one bit in memory. "Concatenated" means
that each bit field will be placed in memory just after its predecessor within the bit set (no alignment considerations
apply).

I assume that in a map keys may not be unique (this should be added to 7.4.13.4.3.1), in case that is a restriction for a map, I propose to add a multimap which allows keys to be duplicate.

Now that with IDL4 the user can use @default to specify a specific default it would be good to also specify the default for all basic types when no @default is used. That way the user (or tool) can make a decision whether it must use @default in IDL or not

In the footnote the link to http://www.bipm.org/en/measurement-units/ is mentioned, but this seems to be dead, the link should probably be https://www.bipm.org/en/measurement-units/

There is nothing explained what the expected behavior is when an annotation is applied at multiple levels, for example see the changed example from 8.3.3, what is the range for Foo:bar2, is it min=10,max=20 or min=5,max=10

@range (min=10, max=20)
typedef long MyLong;
...
struct Foo

;

Section 8.3.3
Has the normative example;

@range (min=10, max=20)
typedef long MyLong;

It is unclear to me if the annotation applies to the typedef keyword or to the type in the typedef definition.

Add ruby as language, there is a formal OMG language mapping for that, maybe just add all programming languages for which the OMG already has a formal language mapping

The spec doesn't say anything about bitmask bit_value scoping. I think the spec currently allows

bitmask MyBitMask

;

This is problematic when a bitmask maps to an enum in C++. As a bitmask is pretty similar to an enum I do ask the following, in section 7.5.2 it says:

Enumeration value names are introduced into the enclosing scope and then are treated like any other declaration in that scope.

What about a bitvalue, shouldn't this also be done for a bitvalue (the members of a bitmask), that would allow a safe mapping to an enum in C++.

The spec should be clear about where bitmasks are introduced, within the bitmask scope itself, or in the enclosing scope

For int8 a new signed_type_int is defined, but I think it should just do the following so that anywhere where octet is used now int8 can be used

<octet_type> ::+ "int8",

Currently the key element type for maps is the same as the value element type, but that looks to be open, this allows for example a union, struct, reference, or other complex type as key type, all of them lack a comparison operator, very likely it is better to define a special map_key_type_spec just as we have for the union as switch_type_spec

IDL 4.2 syntax supports inheritance of only interfaces, valuetypes, and structures.

There are multiple scenarios where it would be useful to inherit other types, specifically Unions and Enumerations.

(1) Inheritance of unions

This would be very useful in some specs where unions are automatically generated. For example unions are created interface definitions in DDS-RPC and derived interfaces would like to use unions that "inherit" the unions in the base interfaces.

This would be useful when a "derived" union wants to add some more cases to the base union.

The derived union would have to use the same discriminator type. All it can do is add new discriminator cases that do not conflict with the non-default discriminator in the base union.

It can add a default case if not present in the base union.

Proposed syntax would be:

union DerivedUnion : BaseUnion {
    case 1 :
       Case1Type case1meber;
...
};

(2) Inheritance of enumerations

This is useful to add literals to an existing enumeration without touching the original definition.

The literals on the derived union would be constrained to not conflict the literals in the base class.

Proposed syntax would be:

enum DerivedEnum : BaseEnum {
    AdditionalLiteral1,
    ...
};

For bitmask the spec says "By default, the size of a bit mask is 32", but what unit is 32, I assume the spec wants to say "By default, the size of a bit mask is 32 bits"

All constructed types map to a C+11 class with accessors, but the new bitset mapping is an exception now, it delivers no accessor methods which gives a different API to the programmer. We propose to map to a class with accessors, similar like struct, or fastdds does in their implementation (see https://fast-dds.docs.eprosima.com/en/latest/fastddsgen/dataTypes/dataTypes.html#bitsets). Also the IDL inheritance is gone in C11, propose to use a derived class, so that in the C+11 code there is also an inheritance

The spec says for bitfield " list of identifiers (<identifier>*).", shouldn't this be 1 or 0 identifiers, what if the user specifies 4 identifiers, how to separate them, what is the meaning?

There is a general need to document the IDL. However the IDL language does not provide any standard way to do this. As a consequence people may be forced to define custom annotations which would preclude the use across projects and/or development of general tools that are documentation aware.

To remediate this the suggestion is to add some built-in annotations that maybe used to document the IDL. For example the @documentation annotation below:

@annotation documentation {
    string value default "TBD";
};

This annotation could applied to a type declaration or to a member / element, as in:

@documentation("This documents the type Foo")
struct Foo {
    @documentation("documentation for member m1")
    long m1;
    @documentation("documentation for member m2")
    long m2;
 };

@documentation("This documents the type MyEnum")
enum MyEnum {
    @documentation("documentation for literal L1")
    L1,

    @documentation("documentation for literal L2")
    L2
 };

When map/bitset/bitmask are added it looks formal_parameter_type is not extended to allow these new types to be used as templated module arguments.

The spec gives:

const <MemberType>& <MemberName>() const

But for basic types/int this will result in a warning, for basic/enum it should be

<MemberType> <MemberName>() const

The spec says:

A public constant accessor method with the name of the union member that returns a constant reference to
its value:
const <MemberType>& <MemberName>() const;
Accessing an invalid union member may result in an undefined error.

A language mapping should be precise and very clear to my idea, the user should know what happens if an invalid union member is accessed, this could happen in some cases, the spec should specify which exception will be thrown so that the programmer can react on this, saying it is undefined is not enough.

Section 7.4.13.4.3.1 defines IDL Maps but doesn't specify:

• Which types may be keys
• If maps need to de-duplicate equivalent entries
• If maps need to preserve order

The most essential of these is the first. It's currently unrestricted but this causes problems for language mappings where some additional operations (like less-than or equal-to) must be defined for these types. In order to prevent different language mappings adding different (conflicting) restrictions, the IDL spec should define this.

One approach to this would be that each building block should define how its types can (or can't) be used in maps. For example: everything in core data types is allowed; interfaces are not allowed; valuetypes are not allowed; etc.

The section Imports contains

The effects of an import statement are as follows:

• [...]
• Importing a name scope recursively imports all name scopes nested within it.

This looks counter intuitive to me.

Example:

module commontypes {
   module nested1 {
      enum RGBColor { RED, GREEN, BLUE };
   }
   module nested2 {
      enum TrafficLight { READ, YELLOW, GREEN };
   }
};

What happens if another module does "import commontypes"?

If, as the standard says, all name scopes nested within "commontypes" are recursively imported then this would lead to errors:
The enum values RED and GREEN would be directly visible and would be in conflict with each other.

The 'Group of Annotations General Purpose' includes the @autoid annotations which can optionally specify a HASH as in @autoid(HASH).

To be useful this must be augmented with the @hashid("MyString") annotation that allows an ID to be explicitly assigned by computing the hash of a string using the same algorithm that @autoid(HASH) uses.

ptc/19-07-02 section 7.2.4.2.1 defines the mapping of sequences of basic and non basic types in terms of Java interfaces.
However, the classes implementing the interfaces are not defined.
The implementation classes are required for actual programming.
If it is intended that the user shall provide own implementations then this should be expressly stated.

7.4.15.4.2 on p.101 contains the rule

(225) <annotation_appl> ::= "@" <scoped_name> [ "(" <annotation_appl_params> ")" ]

The nature of the EBNF notation leaves room for interpreting that between the @ and the <scoped_name> there could appear spaces, tabs, or even comments.

On the other hand, 7.4.15.4.1 on p.100 contains:

(220) <annotation_header> ::= "@annotation" <identifier>

Here, it is clear that @annotation shall be treated as a single token without intermittent characters between @ and annotation.

I propose adding a clarification in the explanations at the beginning of p.102 (following rule 227):

Applying an annotation consists in prefixing the element under annotation with:

• The annotation name ( <scoped_name> ) prefixed with the at symbol( @ ), also known as commercial at. There shall be no intermittent spaces, tabs, or comments between @ and <scoped_name>.

The last sentence is my proposed addition.

Table 7-13 (Integer types) should have a little bit wider column 1 and the font size "See Building Block Extended Data" should match the other font in this table

Extend the grammar for Constants to allow constants for all Core Data Types that are currently not allowed:

• sequence
• structure
• union
• array

Section 7.4.1.4.4.4.4 Constructed Recursive Types and Forward Declarations (in the Core Data Types BB) has special semantic rules for sequences. The intent of Maps (in the Extended Data Types BB) seems to be that maps should have these same semantic rules.

There are a lot of more possibilities to be used with C++11 compared to C++, there is a specific OMG language mapping for C++11, so we would like to propose to add c++11 as defined value

Currently when we want to declare a type in a deeply nested module we have to start with all higher level modules, for example

module A {
module B {
module C

7.3 Any says:

"The IDL any type shall be mapped to org.omg.type.Any type."

A.1.4 Any says:

"The IDL type any maps to a public class named org.omg.CORBA.Any with the following definition

package org.omg.CORBA;
public class Any {
..."

Suggested solution:

Replace class declaration with:

"package org.omg.CORBA;
public class Any implements org.omg.type.Any {
..."

It is unclear whether or how annotations such as "unit" and "range" apply to the values in an array or sequence. Other annotations may have similar ambiguity.

Do they apply to each contained value, or do do they somehow apply to the aggregate value? What about multi-dimensional arrays or nested sequences?

Does the range somehow apply to the sequence length, perhaps as a minimum?

Where do they belong in the array or sequence definitions – before the keyword, before the type name, or somewhere else?

Do the different locations accept different annotations? Do the annotations change meaning depending on location?

IDL 4.0 contained specific grammar rules for where annotations can be applied. Issue IDL41-9 revised these rules and left the spec with the general statement that (7.4.15.4.2): "An annotation may be applied to any IDL constructs or sub-constructs."

This is problematic for the following reasons:

• The phrase "under annotation" is used in multiple places in the spec without it being defined
• Tool implementors using a grammar based on the one in the spec need to make their own enhanced grammar to include <annotation_appl>, which undermines the usefulness of having a grammar in the spec
• Documentation of specific annotations (whether standardized in IDL, standardized in other OMG documents such as XTYPES, or non-standard) has no systemic way of describing where the annotation should be used
• Users have little assurance that their IDL will be understood by all conforming tools, even when using standardized annotations

IDL 4.2 section 7.4.1.4.3 Constants consistency rules on page 32 contains

• An octet constant can be defined using an integer literal or an integer constant expression but values outside the range 0…255 shall be treated as an error.

ptc/20-05-17 section 7.2.4.1.6 maps IDL octet to Java byte.
For mapping IDL const octet values 128 to 255 to Java, it should be permissible to apply promote_integer_width to octet.

The annotation optional impacts the language mapping, for example in C it results in a pointer, with C++11 it could be a IDL::optional<>. The usage of an annotation is very weak in terms of semantics, it is much better to use a new optional keyword as optional heavily impacts the type presented to the programmer. Adding optional will break existing user code, it is not only something that is checked by a concrete middleware.

This should be changed to a "may" or a "could". Shall seems overly prescriptive.

How could a compliant implementation of Equals<T> be distinguished from Equals(Object) from the callers/users perspective?

The annotations should be covered in a separate section of the document and NOT be part of a clean, canonical example.

Suggest:
// IDL
enum E

;

// C#
public enum E

;

Also should enums inherit uint?

Anonymous types should be moved to their own section

Suggest:

//IDL
typedef long myLongArray[2][3];

// C# example

Since IDL is a specification language why have an IDL interface that cannot define data types it wishes to encapsulate and use as parameters for methods and attribute types? It looks like someone had a programming language in mind. I guess in the end the reason I think basic interfaces are a bad idea is that they can only be identified heuristically. The absence of contained types is a poor indicator of the IDL authors intent regarding whether the interface is basic or not.

Currently the specification says: Note – The default value (TRUE) is significant when the annotation is present (this means that using the compact form @nested will set the element as nested, which is what is expected intuitively). It does not mean that by default (i.e.,when no annotation is present) an element is nested.

The case when no nested is present should be specified, it should be the same as TRUE or FALSE and not left open. We observed that different DDS vendors take different decisions making portability of user IDL which uses partly @nested broken. Some vendors assume default nested TRUE, others FALSE which in practice means when the user wants portable IDL he has to specify it which each IDL type.

Suggestion is to have one section or appendix where possible naming mappings could be covered.

Change the IDL example naming to match the C# community expectations if that makes it easier to specify

Beside basic types no other canonical example is included. I suggest removing the basic types and having one example.

// IDL
struct foo

;

Something like this.

Types such as sbyte and int32 are included in this section and should not be.

These types should be moved to the extended types section.

The section for these types is missing from the document.

For the CORBA specifications as part of the scope chapter there are no hyperlinks, these should be added

The specification just lists any as value for the min/max/default annotations, but that tells nothing about what is allowed as value, are for what about hex/octet values, floats, etc. Maybe make this more precise by referring to the value_expression rules `<const_expr>` as specified in 7.4.1.4.3 constants

The specification is unclear of what the user can expect when using mutable and annotations like range, what when the old version of the type has a range of 1-10 and the new one range of 1-5. An old version is send with value 6, what does the receiver get? Very likely more annotations need to be extended in their description related to mutable

extensibility is heavily under specified in IDL4.2. It is listed as a general purpose annotation but it says nothing at the moment for the case appendable/mutable is specified and types are evolved. What are at that moment the rules for assignability/compatibility. Someone who just looks at IDL4 lacks a lot of required information

This building block section is missing (e.g. sbyte).

It seems every section has this deviation of alternative identifier mappings. I find that it maps the document more difficult to read. The document at large should provide canonical text and examples. These alternatives should be placed in a section that caters to those alternatives with easy links to this section elsewhere in the document.

I could not find a place that discussed what is expected if an IDL compiler encounters an annotation that it can parse but does not understand.

The section on annotations should contain examples of how to use the various standard annotations.

This section needs to be filled out with examples of anonymous IDL types.

The example uses annotation to define the type. The mapping should be clean/pure without annotations. The annotation should be moved to the sections on annotations.
// IDL
enum AnEnum

;

// Java
public enum AnEnum {
X,
Y;
private int value;
private AnEnum(int value)

public int getValue()

public static AnEnum valueOf(int v)

7.17 Standardized Annotations
}

Same as the description

Ensure the correct separation of building block basic types (e.g. sbye)

There needs to be a section on IDL interfaces being mapped to Java 8 interfaces which provide the capability to be a proper container. This removes the need for the old fooPackage id foo were defined in an IDL interface named foo.

Now that IDL is modular with building blocks, IDL authors need a way of guarding IDL files so they are compatible with tools that implement different subsets of the building blocks. See discussion in IDL43-21 for a motivating example.

See C++ feature test macros for a possible implementation pattern.
https://en.cppreference.com/w/cpp/feature_test

Another option is to have an "IDL_VERSION" macro that can be used as a pre-processor condition.

At present, annotation syntax must be placed in the IDL file, usually right before or after the syntax being annotated.

This works very well for annotations that define shared interface constraints. It does not work well for annotations that control internal implementation details, such as the selection of an API option. These internal details should be separated from the shared interface and so do not belong in the shared IDL file.

This proposal is to add a new syntax for annotating IDL structures. The basic idea is to define an annotation that takes two parameters, a "place" in the IDL and an annotation, and has the effect of inserting the annotation at the given place. For example @insert(Foo.x, @some(value)) would be equivalent to placing @some(value) by the definition of Foo.x.

With this mechanism, end users could create a custom IDL that includes the shared IDL and then adds the custom annotations.

7.4.13.4 "Explanations and Semantics" gives a synoptic list of the complements,

Those complements are:

• Additions to structure definition in order to support single inheritance and void content (no members).
• Ability to discriminate a union with other types (wide char and octet).
• An additional template type (maps).
• Additional constructed types (bitsets and bitmasks).

The complement "Integers restricted to holding 8 bits of information" (7.4.13.4.4) should be added there.

Predecessor: CPP1116-3

For mapping the switch of unions, the language mappings choose different fixed names.
It would be desirable to permit names that reflect the user's application domain.
Example:

  enum environment_t { air, water, land };

  @switchname("environment")
  union env_info_t switch (environment_t) {
    case air:
      air_info_t air_info;
    case water:
      [...]
  };

The @switchname annotation would cause the discriminator to be mapped using the given name.

This may replace the name chosen by the language mapping (such as in the Ada mapping), or it may supplement the mapping chosen name (such as in the C++ mapping), depending on the nature of the mapped union.

The provided name may not overlap with an enum value given in a case and it may also not overlap with a branch member name.

Currently the spec says:

The << binary operator indicates that the value of the left operand shall be shifted left the number of bits specified by the right operand, with 0 fill for the vacated bits. The right operand shall be in the range 0 <= right operand < 64.•The >> binary operator indicates that the value of the left operand shall be shifted right the number of bits specified by the right operand, with 0 fill for the vacated bits. The right operand shall be in the range 0 <= right operand < 64

But this should be more restricted, the range should be dependent on the number of bits of the underlying type, when it is for example a 32bit long, the operand should be in the range of 0 <= 32

IDL 4.2 allows the @value on an enum to set a specific value for example

enum Test_E

;

It would be more clear and logical when IDL would allow

enum Test_E

;

The section that describes the default value does not include a discussion
of what to do when a default is not present. In this case a method called _default or
__default should be defined to set the discriminant to a non-switched field value.
This should be fixed before December.

The use of the Omg.Types name should be changed to OMG.Types.

Every scope containing a constant declaration shall contain a public static partial class.

The "public static partial class" is inconsistent with the examples in 7.2.3.1 above.

The use of "partial" is suspect and cannot span assemblies. It may be useful for forward interface declarations though whose definition appears in another IDL file.

At the moment model generated IDL files are used it could happen that in a certain configuration setting an empty IDL module appears in an IDL file or when doing some prototyping the users uses an empty IDL file. Currently seciton 7.4.1.4.2 of the IDL specification requires an IDL module to have at least 1 definition. We propose to more relax this, to allow an empty IDL module.

Rule 3 should be changed to

<module_dcl> ::= "module" <identifier> "

" A module

And in the text

A list of at least one definition (<definition>+) enclosed within braces ({}). Those definitions form the module body.

Could be changed to

A list of zero or more definitions (<definition>*) enclosed within braces ({}). Those definitions form the module body

It is possible to put an annotation on an attribute with multiple declarators, like this:

struct Foo {
  @key long x, y;
};

What is the effect of this? Does the annotation apply to both declarators? In that case, how do you interpret the following:

struct Foo {
  @fieldid(0x01000) long x, y;
};

The spec should say how to handle this case.

Proposal - annotation applies to all declared members. In some cases this causes an error (same ID on 2 members). In other cases, tools could decide to issue warnings.

Structure inheritance is described by rules (45) and (48), page 27. The constraints on using forward-declared structures are given in section 7.4.1.4.4.4.4, page 40. For clarity, it would be better if this section made explicit the prohibited uses of forward declarations. This is done for value types in section 7.4.5.4.2 on page 57, "It is illegal to inherit from from a forward-declared value type not previously defined". Though this is a clarification it has been shown to be needed as this illegal use for forward-declared structures has occurred in external (to OMG) specifications that use IDL.

Programming languages that have the concept of modules/namespaces also include the concept of "using" a namespace type such that one can ommit the explicit reference to the 'used' namespace.

The following is an example for C++:

Assume the declaration:

namespace MyNamespace
{
    class MyClass
    {
    public:
        void my_operation() {}
    };
    void MyFunction1(MyClass) {}
}

Normally these types need to be accessed using their fully qualified names:

MyNamespace::MyClass obj;
obj.my_operation();
MyNamespace::MyFunction1(obj);

This can be cumbersome when having to reference a lot of types in the same namespace, specially for deep nested namespaces.

The C++ using declaration can bring the name space or individual types into scope simplifying the coding as in:

using MyNamespace::MyClass;
MyClass obj;
obj.my_operation();
MyFunction1(obj);

Or alternatively bringing every type in the name space into the scope:

using namespace MyNamespace;
MyClass obj;
obj.my_operation();
MyFunction1(obj);

Java and C# provide similar facilities:
In Java the "import" keyword is used to import packages or types into the scope. The syntax is:

import package.name.ClassName;   // To import a certain class only
import package.name.*;

In C# the "using" keyword is used to import namespaces or types into the scope. The syntax is:

using  MyNamespaceName.MyClassName;   // To import a certain class only
using MyNamespaceName;

This issue request that a similar facility is added to IDL

This was originally reported as https://issues.omg.org/browse/CORBA34-1

In 7.5.1, the 3rd bullet point lists "interface, struct, union, exception." Instead the same language from 7.5.2 ("The following kinds of definitions...") should be in effect.

In section 7.4.4.4.2 it is explained that an annotation may be used in a shortened form in the following conditions:

• There is no member or only one member with a default value.
  • In that it is allowed to apply the annotation by using just the annotation name.
• There is only one member.
  • In that case you may apply the name of the annotation and the value of its member, without explicitly mentioning the member name and the equals sign.

However, the second bullet may break backward compatibility when annotations get extended with additional members in future spec releases. Consider the following example:

@bit_bound(32)
bitmask DataRepresentationMask {
   @position(0) XCDR, 
   @position(1) XML,
   @posiiton(2) XCDR2
}

@annotation data_representation {
    DataRepresentationKind allowed_kinds;
};

Now to annotate an IDL type to support only the XCDR2 annotation, I can apply a shortened annotation like this:

@data_representation(XCDR | XCDR2)
struct Foo {
   long my_long;
};

Now suppose in a future version of the spec, we extend the @data_representation annotation with an additional field to specify the supported endianness, like this:

enum EndiannessKind {
    BIG_ENDIAN,
    LITTLE_ENDIAN,
    NATIVE_PLATFORM
};

@annotation data_representation {
    DataRepresentationKind allowed_kinds;
    EndiannessKind endianness;
};

In this case, the addition of the new member suddenly invalidates existing IDL files that use the shorthand notation.

What I want to propose is to allow the shorthand notation to be used for implicitly referring to the first available member. That is fully compatible with the current rule, but will also still apply when new members are added afterwards.

The example for 'References to a Template Module' contains the line:
alias MyTemplModule2<S1, S2, m> MyTemplModule;

According to rule 193, 'MyTemplModule2' should be a scoped_name that refers to a previously defined Template Module. There is nothing else (successfully) defined as 'MyTemplModule2'. I think this line should be:

alias MyTemplModule<S1, S2, m> MyTemplModule2;

The grammar rule 195 (for struct_def) indicates that a structure may either inherit from a base or may be empty, but not both. The intent based on the text around the rule seems to be to allow structs that are both empty and inheriting.

8.3.3.1 "@default" and 8.3.6.2 "@oneway" specify standardized annotations that a user is not allowed to make use of because grammar rule 225 (in 7.4.15.4.2) states that a <scoped_name> is used to identify the applied annotation. From rule 4, a <scoped_name> is built out of <identifiers> which can't be keywords (see 7.2.1, 7.2.3, 7.2.4).

Section 7.4.11.4.3 on page 85 contains:

(181) <connector_inherit_spec> ::= ":" <scoped_name>

The rule number should be 182.

Page 112 top continues the bullet list started on p.111 bottom:

• May precise on which elements the annotation is valid in that specific context. That list may be only a subset of all the possible ones.

Replace "precise" by a verb, e.g. specify, detail, elaborate, or expound.

• Shall indicate the default behavior [...]. This is because the later values are intended to be the most logical values when the annotation is present.

"later" -> latter

How are bitsets that use inheritance mapped?

In section 7.2.4.2.1.1 on page 13 top of page after end of fixed font Java code:

Where:
• <IntarfaceName> is the interface name indicated in Table 7.4.

<IntarfaceName> should be <InterfaceName>

In Clause 7.2.4.2.1.2, Sequence of non Basic Types, the text describing when to throw an exception is somewhat repetitive.

In Clause 7.2.4.3.2 Unions, the requirement for implementing java.io.Serializable is repeated.

In section 7.2.4.3.2 on page 16 paragraph before the union U1 example:

[...] The first modifier method shall
take no arguments, return void, and setsthe discriminant to the first available default value starting from a 0 index of the
discriminant type.

setsthe should be set the.

In section 8.1.3 table 8.2 column "IDL Construct", repeated typo:
Accesor should be Accessor.
In particular, on page 32:

Structure Member Name in
Accesor/Modifier Methods

Union Member Name in
Accesor/Modifier Methods

and on page 33:

Interface Attribute Name in
Accesor/Modifier Methods

Exception Member Name in
Accesor/Modifier Methods

Bitfield Name in Bitset
Accesor/Modifier Methods

Throughout the document URIs starting with "http://" should start with "https://" instead.

The revised submission contains a number of typos and inconsistencies that should be fixed:

• In Clause 7.2.4.2.1.1, Sequence of Basic Types, IntarfaceName should be InterfaceName.

• In Clause 7.2.4.2.1.2, Sequence of non Basic Types, the text describing when to throw an exception is somewhat repetitive.

• In Clause 7.2.4.3.2 Unions, the requirement for implementing java.io.Serializable is repeated.

The ptc/19-07-02 section 7.2.4.4 proposes a weak mapping for IDL arrays in that they are mapped directly to Java arrays.
This means that the fixed size nature of IDL arrays cannot be enforced at the location of usage (e.g. index checking and handling of variable size operations of java.util.List).

On the other hand, 7.2.4.2.1.1 does define an abstraction for "Sequence of Basic Types", see Table 7.4 where e.g. sequence<boolean> is mapped to the interface BooleanSeq.
A similar mapping could be defined for IDL arrays.

Example:

  // IDL
  enum Color { RED, GREEN, BLUE };

  typedef Color ColorArray[3];

could be mapped to

  public enum Color {
    // [...]
  }

  public class ColorArray implements org.omg.type.Array<Color> {
    public ColorArray() {
      elementData = new Color[3];   // initialize private member
    }
    // [...] most of the operations can be implemented in the superclass
  }

The generic abstract class org.omg.type.Array would provide getter, setter, and other methods. It could also throw an exception on use of java.util.List operations that undermine the fixed size. I can provide a demo implementation of the class if desired.

If it is desired to maintain the possibility of using plain Java arrays then the mapping could be made switchable via an annotation.

Examples given throughout ptc/19-07-02 make indiscriminate use of anonymous types; see

• 7.2.4.2.1.2 struct MyType
• 7.2.4.4 struct S2
• 7.2.4.6 struct MyType
• 7.14.3.1 struct S4

For IDL compatibility with other mappings that do not support anonymous types (see e.g. C++11 mapping version 1.4 stion 6.2), the examples should preferably use typedefs.
Further, it should be mentioned that anonymous types can incur portability problems when used with other language mappings.

Something I noticed while looking at the union mapping for CORBA. Why is it that the IDL4 mapping uses two underscores prepended to the default method (e.g. __default v.s. _default)?

If there is no technical reason for it I think the single underscore is preferred.

Interfaces - Full should define a FooOperations interface like we have done in the IDL to C# Language Mapping.

Also, public abstract void op1(S sIn); should be changed to void op1(S sIn);.

7.2.6.2.1 on page 23 contains:

A character literal is one or more characters enclosed in single quotes, as in:
const char C1 = ’X’;

Please use the ASCII apostrophe:
const char C1 = 'X';

If an implementation wishes to claim support for the "Building Block Extended Data-Types", it must support all of its complements, including the section 7.4.13.4.4 "Integers restricted to holding 8-bits of information".

However, if the targeted programming language does not natively support int8 or uint8 then it is not obvious how the "unsupported" type may be mapped.

For example, the Java language has a native type byte which is signed.
The question then arises how the implementation maps the type uint8.

The implementation could choose to

• Maintain bit size:
  In that case, it would map uint8 to Java byte.
  The question then arises how values exceeding the positive signed maximum (127) are handled.
• Maintain numeric range:
  In that case, it could map uint8 e.g. to Java short (16 bit quantity) or int (32 bit quantity).
  The implementation must then address the interoperability with other languages where uint8 is
  mapped to an 8 bit quantity.
• Use yet a different mapping, for example a holder class (cf. Short, Integer, etc.)

I therefore propose adding the requirement that the implementation shall document its mapping choice:

If the targeted programming language does not natively support int8 or uint8 then an implementation
shall include information about how it maps the types which lack the native language support.

In section 7.4.11.4.3 page 87 and in Annex A page 132, <connector_inherit_spec> should have the rule number 182.

There is a stray > at the end of the title,

7.4.1.4.1 IDL Specification>

Page 133 last item of "From Building Block Extended Data-Types" :

(1) <unsigned_longlong_int> ::+ “uint64”

The rule number should be 215.

As an aside, the quotation marks used in rules 208 to 215 are fancy Unicode characters while the rest of the grammar uses the regular ASCII code 34 decimal.

This is not an issue in the strict sense, just a usability observation.
If I copy/paste the word <porttype_def> of rule 174, it comes out as

>‎ yedeepyotrop <

In section 4 "Terms and Definitions" on page 7, the last sentence is:

> [...] Building blocks are described in
> clause 0,

The sentence seems to end on the comma; furthermore, I cannot find a "clause 0".

The title of 7.4.13.4 says:

7.4.13.4 <unsigned_longlong_int> ::+ “uint64”Explanations and Semantics

This is a formatting error. The {{ <unsigned_longlong_int> ::+ “uint64”}} should appear before the title as one of the rules following:

(214) <unsigned_long_int> ::+ “uint32”

Note that this problem appears only in the generated PDF. The word document is fine.

Section 7.4.1.4.4.4.3 Enumerations says:

An enumeration must contain at least one enumerator and no more than 232.

The 232 is a typo. It was meant to be 2 ³²