ISO/IEC C++ 2003 Language DDS PSM Avatar
  1. OMG Specification

ISO/IEC C++ 2003 Language DDS PSM — Closed Issues

  • Acronym: DDS-PSM-Cxx
  • Issues Count: 29
  • Description: Issues resolved by a task force and approved by Board
Closed All
Issues resolved by a task force and approved by Board

Issues Summary

Key Issue Reported Fixed Disposition Status
DDSPSMC-24 Inconsistencies related to use of const& DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMCF2-5 Update specification for final DDS-XTypes DDS-PSM-Cxx 1.0b2 DDS-PSM-Cxx 1.0 Resolved closed
DDSPSMCF2-4 Assignment Rule for Container Types DDS-PSM-Cxx 1.0b2 DDS-PSM-Cxx 1.0 Resolved closed
DDSPSMCF2-3 Useless ReaderQuery on DataReader read/take DDS-PSM-Cxx 1.0b2 DDS-PSM-Cxx 1.0 Resolved closed
DDSPSMCF2-2 ReaderState: the class name does not reflect the intent of the class DDS-PSM-Cxx 1.0b2 DDS-PSM-Cxx 1.0 Resolved closed
DDSPSMCF2-1 The Status API, e.g. sample_rejected_status, deadline_missed_status, etc., are missing from the DataReader DDS-PSM-Cxx 1.0b2 DDS-PSM-Cxx 1.0 Resolved closed
DDSPSMC-23 read/take consistency for loaned and non-loaned samples DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-22 Getter/Setter for member arrays DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-21 Expected use of AnyDataReader::get and its implication on AnyDataReader's template constructor DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-20 The tdds namespace should be merged into the dds namespace DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-19 IDL mapping for non-trivial struct fields DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-18 optional support DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-17 RadarTrack uses anonymous types DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-16 Typos in Value.hpp, Exception.hpp DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-15 Make parameter passing same for native/type parameters DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-14 Supporting automatic conversion from value types to delegate types DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-13 Improving usability of EntityQoS API DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-12 General Exception Safety Considerations DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-11 Exception safety guarantees for the DataReader API DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-10 Portable exception-safety guarantees for DDS C++ PSM DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-9 Use traits for topic/datareader/datawriter DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-8 Inheritance via dominance warning on Visual Studio DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-7 Fixing bugs and improving usability of the InstanceHandle class DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-6 Improving usability of Reference class DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-5 Compilation errors on Visual Studio 2008/2010 DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-4 Dividing a scalar in Duration and Time classes DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-3 Union/array/bounded types lacking DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-2 factory methods on the "parents" (e.g. create_topic, create_data_writer, etc.) DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed
DDSPSMC-1 XML-Based QoS Policy Settings (DDS-PSM-Cxx/DDS-PSM-Java) DDS-PSM-Cxx 1.0b1 DDS-PSM-Cxx 1.0b2 Resolved closed

Issues Descriptions

Inconsistencies related to use of const&

  • Key: DDSPSMC-24
  • Legacy Issue Number: 16269
  • Status: closed  
  • Source: Remedy IT ( Johnny Willemsen)
  • Summary:

    There is consistency issue in the spec with respect to the use of const & versus returning copies.

  • Reported: DDS-PSM-Cxx 1.0b1 — Thu, 26 May 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The API has been verified to consistently use const reference when possible and values when necessary. Notice that these changes do not change the semantics but in some case can reduce the number of temporary object created.

  • Updated: Fri, 6 Mar 2015 23:16 GMT

Update specification for final DDS-XTypes

  • Legacy Issue Number: 17305
  • Status: closed  
  • Source: DECA ( Rick Warren)
  • Summary:

    The second FTF of the DDS-XTypes spec introduced several API changes that should be incorporated into the DDS-PSM-Cxx spec.

  • Reported: DDS-PSM-Cxx 1.0b2 — Wed, 11 Apr 2012 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0
  • Disposition Summary:

    Update the DDS-PSM-Cxx API to reflect the finalization of the X-Type speficication.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Assignment Rule for Container Types

  • Legacy Issue Number: 17067
  • Status: closed  
  • Source: ADLINK Technology Ltd ( Angelo Corsaro)
  • Summary:

    The ctors declared by the macros OMG_DDS_REF_TYPE_BASE and OMG_DDS_REF_TYPE_BASE_T for initializing proxy classes with delegates should be declared protected as opposed to public. This will ensure (1) that client code is not able to invoke these methods and (2) that the C++ compiler won't try to apply some of the parametrized ctors to incomplete arg-list provided by the user.

    Resolution
    ---------------
    Change ctors declaration from "public" to "protected"

  • Reported: DDS-PSM-Cxx 1.0b2 — Thu, 26 Jan 2012 05:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0
  • Disposition Summary:

    The Reference class ctors identified in this issue were declared “protected”.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Useless ReaderQuery on DataReader read/take

  • Legacy Issue Number: 17066
  • Status: closed  
  • Source: ADLINK Technology Ltd ( Angelo Corsaro)
  • Summary:

    The ReaderQuery class bundles together the read-state as well as potential read conditions. However the read-condition is not always present. This leads to code that needs to check all the time wether something is set or not, which is not only very elegant/efficient but it is also error prone

    Resolution
    ---------------
    Remove the ReaderQuery and let the read API deal, through proper operations overloads, with ReadState and potential ReadConditions. This way it will always be clear if a read/take is with a condition or not both for the client code and the DDS implementor.

  • Reported: DDS-PSM-Cxx 1.0b2 — Thu, 26 Jan 2012 05:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0
  • Disposition Summary:

    The DataReader API has been updated to provide the proper read/take overloads and remove the useless ReaderQuery. The concept of a Selector has been introduced to orchestrate complex read/take operations requiring selection based on state, content and instance. The new API is orthogonal, simple and composable. Below an example usage of the selector API:

    LoanedSamples<Foo> ls =
    dr.select()
    .instance(handle)
    . content(query)
    .take();

    This example takes the samples matching the query q for the instance with given handle.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

ReaderState: the class name does not reflect the intent of the class

  • Legacy Issue Number: 17064
  • Status: closed  
  • Source: ADLINK Technology Ltd ( Angelo Corsaro)
  • Summary:

    The class ReaderState encapsulate the Sample, Instance and View States and provides some useful predefined statuses.
    However the name of the class is relatively misleading as these statuses have nothing to do with the DataReader.
    These statuses are really used to "filter" the data on the reader cache based on its status. The name of the class should
    be replaced by something that better express its role.

    Resolution
    ---------------
    Rename the "ReaderState" class into "DataStatus".

  • Reported: DDS-PSM-Cxx 1.0b2 — Thu, 26 Jan 2012 05:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0
  • Disposition Summary:

    Rename the "ReaderState" class into "DataStatus".

  • Updated: Fri, 6 Mar 2015 20:58 GMT

The Status API, e.g. sample_rejected_status, deadline_missed_status, etc., are missing from the DataReader

  • Legacy Issue Number: 17048
  • Status: closed  
  • Source: ADLINK Technology Ltd ( Angelo Corsaro)
  • Summary:

    Description
    ---------------
    The Status API, e.g. sample_rejected_status, deadline_missed_status, etc., are missing from the DataReader.

    Resolution
    ---------------
    Simply add them.

  • Reported: DDS-PSM-Cxx 1.0b2 — Thu, 26 Jan 2012 05:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0
  • Disposition Summary:

    The missing statuses methods have been added to the DataReader

  • Updated: Fri, 6 Mar 2015 20:58 GMT

read/take consistency for loaned and non-loaned samples

  • Key: DDSPSMC-23
  • Legacy Issue Number: 17337
  • Status: closed  
  • Source: ADLINK Technology Ltd ( Angelo Corsaro)
  • Summary:

    The current DataReader API provides a slightly different API for getting samples when loaning the data vs. when providing user storage.

    When loaning the data the data and the SampleInfo is encapsulated on a Sample type, while when providing user storage two different containers hold the data and the SampleInfo.

    For consistency the two API should encapsulate the data and the SamplInfo on the Sample data structure.

  • Reported: DDS-PSM-Cxx 1.0b1 — Wed, 25 Apr 2012 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    This issue raises a relevant consistency issue. All the operations on the DataReader have been revised to consistently use the Sample type to hold both sample data and sample info.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Getter/Setter for member arrays

  • Key: DDSPSMC-22
  • Legacy Issue Number: 16886
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    The specification maps IDL array to C++ native array. There are two possible alternatives as far as getter/setter functions are concerned.

    class Foo {
    char data[10];
    public:
    char * begin_data()

    { return data; }
    char * end_data() { return data + 10; }


    void data(char * begin, char *end) {}


    template <class Iter>
    void data(Iter begin, Iter end) {}
    };


    AND


    class Foo {
    char data[10];
    public:
    char * data() { return data; }

    size_t data_size()

    { return 10; }

    void data(char *ptr, size_t size) {}
    };

    The first version is more consistent with modern C++ usage of iterators. In either case a convention must be defined for portability. This may also be applicable to idl sequences.

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 9 Dec 2011 05:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    This issue is automatically resolved as a consequence of the new mapping defined for array as result of issue 16261.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Expected use of AnyDataReader::get and its implication on AnyDataReader's template constructor

  • Key: DDSPSMC-21
  • Legacy Issue Number: 16885
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    AnyDataReader::get is a member template function, which requires passing a type to retrieve a typed data-reader. For example,

    AnyDataReader adr;
    DataReader<RadarTrack> dr = adr.get<RadarTrack>();

    It is better to pass the topic type instead of the data-reader type. For example,

    AnyDataReader adr;
    DataReader<RadarTrack> dr = adr.get<dds::sub::DataReader<RadarTrack> >();

    The first version is less error prone.

    Construction of AnyDataReader, however, does not look consistent with this use. Currently, the template constructor of the AnyDataReader accepts a data-reader as a type parameter (not just the topic type).

    Also, it is not consistent with AnyDataWriter constructor, which takes topic type as a type parameter.

    Resolution: Use the style of AnyDataWriter in AnyDataReader, AnyTopic, and AnyTopicDescription. I.e., Use the topic type as a type parameter for constructor and get() member function.

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 9 Dec 2011 05:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The AnyDataWriter in AnyDataReader, AnyTopic, and AnyTopicDescription now use consistently the topic type as a type parameter for constructor and get() member function. Free function get() have also been added to avoid exotic C++ syntax under some circumstances.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

The tdds namespace should be merged into the dds namespace

  • Key: DDSPSMC-20
  • Legacy Issue Number: 16655
  • Status: closed  
  • Source: ADLINK Technology Ltd ( Angelo Corsaro)
  • Summary:

    The DDS-PSM-Cxx specification groups types constructors into the "tdds" namespace. However this separation makes it harder than it should be to navigate the code. The suggested approach is to remove the "tdds" namespace and migrate those classes into the "dds" namespace by prefixing them with a "T". For instance the "tdds::sub::Subscriber" would become "dds::sub::TSubscriber".

  • Reported: DDS-PSM-Cxx 1.0b1 — Tue, 8 Nov 2011 05:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The API code has been refactored to remove the tdds namespace as suggested by the issue description. In addition figure 7.1 in section 7.2 and page 5 has been updated to reflect the new organization and figure 7.2 has been removed.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

IDL mapping for non-trivial struct fields

  • Key: DDSPSMC-19
  • Legacy Issue Number: 16565
  • Status: closed  
  • Source: Northrop Grumman ( Trent Nadeau)
  • Summary:

    The “representative” example in Section 8.2 is not very “representative”. For example, everything in the struct can be trivially returned by value (either a basic type or a pointer) with no impact on performance.

    If, instead, there were a substructure that was large and/or deeply nested, this example seems to break down. For example:

    typedef sequence<long, 1000000> HugeLongSeq; // 4 MB

    struct LargeStruct

    { long id; HugeLongSeq mySeq; }

    ;

    struct RadarTrack

    { string id; long x; long y; long z; //@optional sequence<octet> plot; //@shared LargeStruct myLargeMember; // new field }

    ;

    According to Section 7.4, the return value of the accessor for myLargeMember would either return by value or const reference. This would cause two copies (one for return value of getter and another for setter) of 4 MB of data in order to change one element of LargeStruct::mySeq in the instance.

    I believe that use cases like this require accessors that return by non-const reference if the generated code is to be at all efficient. On page 17 of the Beta 1 spec, there is already use of this pattern for the non-const accessors on the History class (where it probably makes less sense since the types are small). I believe that this pattern should also be used for generated code where many large types can be arbitrarily nested.

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 23 Sep 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    This issue can be easily fixed by ensuring that constructed and sequence types have a reference return type as opposed to a const reference.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

optional support

  • Key: DDSPSMC-18
  • Legacy Issue Number: 16564
  • Status: closed  
  • Source: Remedy IT ( Johnny Willemsen)
  • Summary:

    DDS PSM does expose dds::core::optional to the end user when he uses
    @optional. At some moment we also have this available at the CCM level,
    what about using something that is not tied to DDS in the user defined
    type? Is there nothing in STL that can be used for this?

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 23 Sep 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    No Data Available

  • Updated: Fri, 6 Mar 2015 20:58 GMT

RadarTrack uses anonymous types

  • Key: DDSPSMC-17
  • Legacy Issue Number: 16563
  • Status: closed  
  • Source: Remedy IT ( Johnny Willemsen)
  • Summary:

    The RaderTrack uses an anonymous type in the example for plot on page 22
    of the beta 1 spec.

    So change

    struct RadarTrack

    { string id; long x; long y; long z; //@optional sequence<octet> plot; //@shared }

    ;

    To

    typdef sequence<octet> plot_type;
    struct RadarTrack

    { string id; long x; long y; long z; //@optional plot_type plot; //@shared }

    ;

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 23 Sep 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    Insert required typedefs

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Typos in Value.hpp, Exception.hpp

  • Key: DDSPSMC-16
  • Legacy Issue Number: 16562
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:
    • hpp\dds\core\Value.hpp around line 67 added & to the return value:

    const D* operator->() const

    { return &d_; }

    2- same file, line 58, 62 added "const" to != and == operators
    bool operator==(const Value& other) const

    { return (d_ == other.d_); }

    bool operator !=(const Value& other) const

    { return !(d_ == other.d_); }

    3- hpp\tdds\core\qos\EntityQos.hpp line 88 added "const" to declaration

    const EntityQos& operator >> (POLICY& p) const {

    4- dds\core\policy\CorePolicy.hpp, line 38. name() method is not public.
    class policy_name<POLICY>

    { \ public: \ static const std::string& name(); \ }

    ;

    5- hpp\dds\core\Exception.hpp, line 202 wrong parameter type in the ctor
    InvalidDataError(const InvalidDataError& src);

    Proposed solution:

    Add the missing things.

  • Reported: DDS-PSM-Cxx 1.0b1 — Wed, 21 Sep 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    Add missing designators. Notice that as the final API does not include any implementation only designators have been addressed

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Make parameter passing same for native/type parameters

  • Key: DDSPSMC-15
  • Legacy Issue Number: 16411
  • Status: closed  
  • Source: Remedy IT ( Johnny Willemsen)
  • Summary:

    We would like to propose to make the mapping for native and type parameters the same. So const T& for in and T/const T& for return. This makes the mapping easier and more consistent. For example the DDS InstanceHandle_t is defined as native, some vendors define it as long, some as a struct which leads to different code being generated when the end user has a local interface with a DDS InstanceHandle_t as argument. Also when the end user changes a typedef from a native to a struct the argument passing doesn't change from T to const T&. This doesn't impact performance in anyway, it just makes the mapping the same for all types

  • Reported: DDS-PSM-Cxx 1.0b1 — Mon, 1 Aug 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    No Data Available

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Supporting automatic conversion from value types to delegate types

  • Key: DDSPSMC-14
  • Legacy Issue Number: 16405
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    Supporting some vendor-specific extension api is significantly easier using automatic conversion from value types to the delegate types. The situation arises when an extension method defined in the idds namespace takes a parameter defined only in the idds namespace. The parameter type may also be used as a delegate elsewhere. While the programmers can use the -> operator to invoke the extension method, the parameter need must be obtained using the delegate() method of the value type. It would be quite seamless to support automatic convertibility from value types to the delegate.

    Proposed Solution:
    Define two additional generic conversion operators in dds::core::Value<D> template.

    operator D & ()

    { return d_; }
    operator const D & () const { return d_; }

    ;

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 29 Jul 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The suggested conversion operators have been added into the Value and Reference classes.
    See:
    dds-psm-cxx/src/hpp/dds/core/Reference.hpp
    dds-psm-cxx/src/hpp/dds/core/Value.hpp

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Improving usability of EntityQoS API

  • Key: DDSPSMC-13
  • Legacy Issue Number: 16404
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    8. Supporting method chaining for setting qos parameters would improve readability of the API.

    For instance,
    DataWriterQos dwqos;
    dw >> dwqos;
    Dwqos.policy<History>().kind(KEEP_ALL).depth(200);
    Dwqos.policy<ResourceLimits>().max_samples(p).max_instances(q).max_samples_per_instance(r);
    dw << dwqos;

    Currently, it needs different function calls for every qos parameter.

    Proposed Solution: Change all the normative core qos policy classes (e.g., History, ResourceLimits) to return a reference to itself from the setters. Currently they return nothing.

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 29 Jul 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The problem raised has been addressed by equipping all the Policy classes with fluent setter methods. The example provided by this issue can now written as follows:

    DataWriterQos dwqos;
    dw >> dwqos;
    dwqos << History::KeepAll(200)
    << dwqos.policy<ResourceLimits>()
    .max_samples(p)
    .max_instances(q)
    .max_samples_per_instance(r);

    dw << dwqos;

    The changes applied to the given policy class P is to have its setter return P&.
    See dds-psm-cxx/blob/master/src/hpp/dds/core/policy/TCorePolicy.hpp

  • Updated: Fri, 6 Mar 2015 20:58 GMT

General Exception Safety Considerations

  • Key: DDSPSMC-12
  • Legacy Issue Number: 16403
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    1. The normative implementations shown in the wrapper classes should be at strong exception safe (or at least basic safe). For instance, implementation of DataReader:: create_readcondition as in dds-psm-cxx\src\hpp\dds\sub\DataReader.hpp is a shared_ptr usage anti-pattern.

    Proposed Solution:
    Create separate shared_ptr<T> objects for every new operation. Pass the shared_ptr<T> to the constructor of ReadCondition.

    2. All setters and getters (including overloaded operators) of EntityQos should be strong exception safe.

    Proposed Solution: Make copy-assignment operator of every qos type in normative namespaces strong exception safe.

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 29 Jul 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    No Data Available

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Exception safety guarantees for the DataReader API

  • Key: DDSPSMC-11
  • Legacy Issue Number: 16402
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    The DataReader API must provide an exception-safe way to retrieve samples and must specify guarantees when exceptions are thrown. The exception safety of the DataReader API is analyzed with respect to user level state and middleware state. Read and take are both logically non-const operations with respect to the m/w because both of them have side effects such as changes in the sample_state and instance_state. There could be exceptions while delivering samples from m/w space to user space on the boundary of the read/take function calls. Depending upon the implementation there may or may not be a way to roll-back the changes in sample_state and instance_state. However, it is critical to have a way to not lose the samples even in case of exceptions. In general, it is difficult to provide strong guarantees with respect to m/w for datareader api.

    1. Strong and no throw guarantees for LoanedSamples:

    The constructor of LoanedSamples should provide strong guarantees. All the remaining operations (specifically copy-ctor and copy-assignment operator) should provide no-throw guarantees. It is important for LoanedSample to not throw exception during copy because then the samples would be lost. Further, read/take api should minimize dynamic memory allocation and locks on the critical path for performance reasons. Therefore LoanedSamples can’t use reference semantics either. (Reference<D> uses shared_ptr, which uses dynamic memory allocation and mutex to construct and protect the reference count.)

    These strict guarantees for LoanedSamples appear to be essential to support at least minimally exception safe read/take api that does no lose samples in case of exceptions. It is also the intent of LoanedSamples<T> to return the resources to m/w as soon as it goes out of scope.

    Proposed Solution: Use std::auto_ptr semantics in LoanedSamples. A key property of std::auto_ptr is that it can be safely returned while moving the resources out of an inner scope to an outer. No exceptions will be thrown. LoanedSamples<T> should be designed as such to avoid exceptions on copy. There is an idiomatic way of implementing such a class: The Move-constructor Idiom.

    Consequences: No std::vector<LoanedSamples<T>> would be possible. However the anticipated use-case of LoandedSamples is that the users would iterate over the range of samples and copy them and return the loan. For those users who really want to create vectors of loaned buffers, they would take ownership of the buffer from the LoanedSamples and use std::vector<shared_ptr<T> > to automate memory management. Use of custom deleters feature of shared_ptr may facilitate returning of the loan.

    2. LoanedSamples take(): Basic exception safe.

    The take function is loaning a buffer from the m/w. The implementations may or may not provide a way to ‘untake' samples. So this function cannot provide strong exception safety with respect to m/w. Therefore, guarantees of LoanedSample above are applicable here. This would guarantee that the samples that are removed from the history cache are not destoyed before the user gets a chance to access them.

    3. LoanedSamples read(): Basic exception safe.

    An attempt can be made to reread the samples. Above guarantees of LoanedSamples are applicable here

    4. // — Forward Iterators: — //
    void read(SamplesFWIterator, InfoFWIterator, size_t max_samples): Basic exception safe void take(SamplesFWIterator, InfoFWIterator, size_t max_samples): Basic exception safe

    This API probably needs to specify guarantees with respect to two different things:

    1. With respect to state changes in the user supplied range
    2. With respect to m/w state

    Changes to user-supplied range ==== If Nth copy throws there is no way to recover earlier N-1 objects that were already copied successfully. So in general only basic guarantee is provided. If the first object in the range throws, nothing changes and strong safety is provided. Further the API must provide a way to return # of objects were actually copied. API should specify a precondition: iterators must be from a range that is initialized and contain valid max_samples objects. In other words, the range cannot contain any uninitialized object. This prohibits uses such as

    std::vector<T> v;
    v.reserve(max);
    dr.read(v.begin(), v.end(), max);

    Changes to m/w state ==== The read() function has side effects like changes in the view_state and instance_state so it's really not a const function. The implementations may or may not provide a way to ‘unread' samples. So with respect to these status bits there is no way to provide strong exception guarantee so only basic guarantee is provided.

    Proposed Solution: In case of an exception (e.g., std::bad_alloc) during these function calls, construct an internal LoanedSamples<T> object and wrap it in a ‘ReadTakeException’ object and throw it. ReadTakeException class must provide an API to retrieve the LoanedSamples. Nothrow guarantees of LoanedSamples are important here again. This solution provides at least one way to retrieve the samples that are read/take from the history cache. Such a wrapper may also need to wrap the original exception that was raised to support exception neutrality.

    5. // — Back-Inserting Iterators: — //
    read(SamplesBIIterator, InfoBIIterator, size_t max_samples): Basic exception safe take(SamplesBIIterator, InfoBIIterator, size_t max_samples): Basic exception safe

    In addition to the exceptions that forward iterator versions can throw, these functions can throw when vector::push_back throws. I think the same rules are applicable to these functions.

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 29 Jul 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    This issue raises a very important and tricky point. Exceptions raised during a read/take operation might leave user without data and the cache with a side-effect. Although the exceptions that would induce such a undesirable side-effect are due to memory exhaustion, it is desirable to provide at least some variation of the read/take API that are exception safe.
    This issue has been addressed by recommending that the loan-based implementation of read/take operations on the data-reader are implemented using a move-idiom (see http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Move_Constructor) and thus are exception safe (see resolution for issue 16401).
    In addition a new class called SharedSamples has been introduced to ensure we can still use loaned data in combination with standard containers.
    The specification of the SharedSamples class is available at:
    dds-psm-cxx/src/hpp/dds/sub/SharedSamples.hpp

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Portable exception-safety guarantees for DDS C++ PSM

  • Key: DDSPSMC-10
  • Legacy Issue Number: 16401
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    The users of the DDS C++ PSM can benefit significantly if the specification standardizes exception-safety guarantees of the API. Exception safety specification for normative classes would support portable safety guarantees irrespective of vendor implementation and extensions. This would facilitate frictionless transition from one vendor to another in user code.

    Exception safety is about how programs, libraries behave when an exceptional condition arises. It is often much more than just raising an exception. For instance, constructor or copy-ctor of std::string may run out of memory resulting into std::bad_alloc exception. However, in practice, APIs must specify guarantees about the internal state of the data structures after any exception propagates out. Exception-safety guarantees for C++ abstractions come in four categories: strong, basic, nothrow, and neutral. For instance, the push_back member function of std::vector, std::list guarantees that the container remains unchanged (strong exception safety) in case of any exception. In general, programmers expect strong exception safety guarantees but it is often expensive to do so.

    RTI is proposing refined specifications for normative DDS C++ PSM API to make it easier to use even in the face of exceptions.

    1. Strong guarantees for value types:

    All the constructors and copy-assignment operators of normative classes that inherit from Value<D> and the Value<D> template itself should provide strong guarantees. A simple way to achieve that is to ensure that Value<D> template provides strong guarantees and then implement the derived classes in terms of value<D>.

    Not all value types are POD. Some of them use std::string and may throw. Consider, for instance, SubscriptionBuiltinTopicData. Value<D> delegates the assignment to its delegate, SubscriptionBuiltinTopicDataImpl. This impl class has non-pod members such as std::string and does not define its own assignment operator. Assignment of one string (topic_name) may succeed but the assignment of second string (type_name) may fail with a bad_alloc exception. This may result into inconsistent left-hand-side SubscriptionBuiltinTopicData object when DataWriter:: matched_subscription_data is called.

    In general, classes that have more than one non-pod types should have an assignment operator that is strongly safe. Instead of handpicking such classes, Value<D should be made strong exception-safe so that irrespective of vendor-specific extensions, types that users will deal with the most, will be safe to use.

    Proposed solution: Implement the copy-assignment operator of Value<D> using copy-and-swap technique.

    2. At least basic guarantees for reference types:

    Not all implementations may be able to provide strong guarantees for reference types such as DataWriter<Foo>, DataReader<Foo>. Therefore, constructors and copy-assignment operators must provide at least basic guarantees. While Reference<D> itself should provide strong guarantees; just that is insufficient to extend the guarantees to all its derived classes. The normative reference types should provide strong guarantees whenever it is not prohibitively expensive to do so.

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 29 Jul 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    Section 7.3 on page 16 of the specification lists not the mandatory exception safety requiremenst on Value types and Reference Types. Specifically, for reference types it is required that loan-based read/take are exception safe.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Use traits for topic/datareader/datawriter

  • Key: DDSPSMC-9
  • Legacy Issue Number: 16374
  • Status: closed  
  • Source: Remedy IT ( Johnny Willemsen)
  • Summary:

    The proposed PSM takes the DDS PSM and now gives the users templates instead of new classes as with the IDL to C++ mapping.

    For example RadarTrackDataWriter becomes DataWriter<RadarTrack>.

    To my idea this this is syntactical sugar and I still see how the DDS implementation implement their support. I would like to propose a different way. As user I just have RadarTrack, that is coming from my user domain, so why now create a set of traits that can be used by the end user. Than he doesn't see anything special from DDS, not whether it is a template or a class.

    So he writes
    RadarTrack::data_writer_type dw = pub.create_datawriter()
    RadarTrack::topic_type tp = dp.create_topic().

    The DDS implementation can than do anything behind data_writer_type, the only thing the user has to know are the traits and the methods that are possible to be used.

  • Reported: DDS-PSM-Cxx 1.0b1 — Wed, 20 Jul 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    No Data Available

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Inheritance via dominance warning on Visual Studio

  • Key: DDSPSMC-8
  • Legacy Issue Number: 16354
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    Visual Studio spits out many #C4250 warnings on the diamond hierarchy of listeners:

    for instance,
    DomainParticipantListener.hpp(48): warning C4250: 'dds::domain::NoOpDomainParticipantListener' : inherits 'dds::pub::NoOpPublisherListener::dds::pub::NoOpPublisherListener::on_offered_deadline_missed' via dominance

    Proposed solution:

    Add empty bodies for all the inherited virtual functions in all the NoOp*Listener classes. Particularly, NoOpDomainParticipantListener, NoOpPublisherListener, and NoOpSubscriberListener.

    Alternatively, #pragma warning( disable : 4250 ) could be used but its purpose will be less clear even with documentation: "Prevents via dominance warning."

  • Reported: DDS-PSM-Cxx 1.0b1 — Thu, 30 Jun 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    This problems raised by this issue are gone since the specification is not providing with default implementation of any methods. Trivial implementations where used during specification and finalization to ensure the implement-ability of the API along with catching compilation errors. However the finalized API does not include any implementation to avoid over-specification.

    Revised Text:
    No change.

    Disposition: Closed, no change

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Fixing bugs and improving usability of the InstanceHandle class

  • Key: DDSPSMC-7
  • Legacy Issue Number: 16340
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    The InstanceHandle class in dds-psm-cxx\src\hpp\tdds\core\instancehandle.hpp appears to be incomplete in several ways.

    1. A missing constructor
    InstanceHandle(const DELEGATE & d) :
    dds::core::Value<DELEGATE>(d) {}

    There is no way to construct an instance handle except a null one!

    2. A missing copy-constructor
    InstanceHandle(const InstanceHandle& src) :
    dds::core::Value<DELEGATE>(src.delegate())
    { }

    3. Typos: a missing return and needs a dot instead of an arrow.

    InstanceHandle& operator=(const dds::core::null_type& src)

    { return this->delegate().operator=(src); }

    4. Missing comparison operators to allow comparisons like
    if(dds::null == instance_handle_object)

    Currently it supports other way round. The proposed solution is to add two overloaded operators in tdds::core namespace.

    template <class D>
    bool operator == (dds::core::null_type, InstanceHandle<D> const &ih)

    { return ih.is_nil(); }

    template <class D>
    bool operator != (dds::core::null_type, InstanceHandle<D> const &ih)

    { return !ih.is_nil(); }

    5. Finally, the InstanceHandle<D> class and in general the classes that support comparison with dds::null will benefit from supporting a generic and succinct syntax of the form: if(instance_handle_object).

    Proposed Solution:
    An idiomatic way of implenting it is the safe-bool idiom, which has been used widely in standard and boost smart pointer classes, such as std::auto_ptr, boost::shared_ptr. Here is a self-sufficient file that shows one way of implementing the safe bool idiom for the instance handle class:

    http://cpptruths.googlecode.com/svn/trunk/cpp/instance_handle.cpp

    Other possible implementation based on the discussions on the boost mailing list is available here:

    http://codepaste.net/c83uuj

  • Reported: DDS-PSM-Cxx 1.0b1 — Mon, 20 Jun 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The following changes have been applied to the TInstanceHandle class to address this issue:
    1. Defined a new constructor for initializing the instance handle with a specific type:
    template <typename ARG0>
    TInstanceHandle(const ARG0& arg0);
    2. Added copy constructor

    The problems 3, 4 , and 5 are rejected since an InstanceHandle is a Value as opposed to a Reference type. As such comparison with null_ref is conceptually non-correct and potentially highly misleading. The current API provides an isNil method to check wether the handle is or isn’t nil. In addition, the InstanceHandle defines the NilHandle to allow proper comparisons. To this hand an operator== for the InstanceHandle has been added.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Improving usability of Reference class

  • Key: DDSPSMC-6
  • Legacy Issue Number: 16339
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    1. Safety of Reference<D> class should be improved by adding "explicit" keyword in the following constructors:

    template <typename D>
    Reference(const Reference<D>& ref);

    template <typename R>
    Reference(const R& that);

    Reference(const DELEGATE_REF_T& ref);

    2. With just member operator== and operator!= functions, Reference<D> can't be used in expressions like

    if(dds::null == r)

    { ... }

    Proposed solution: Add the following free functions in dds::core in Reference.hpp.

    template <class D>
    bool operator == (dds::null_type,
    const Reference<D> & r)

    { return r.is_nil(); }

    template <class D>
    bool operator != (dds::null_type,
    const Reference<D> & r)

    { return !r.is_nil(); }

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 17 Jun 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The changes suggested by the issue submitter have been applied to the Refence class.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Compilation errors on Visual Studio 2008/2010

  • Key: DDSPSMC-5
  • Legacy Issue Number: 16338
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    Description: The sources obtained from dds-psm-cxx.googlecode.com do not compile on Visual Studio compilers without significant efforts. There are multiple issues most related to type conversion.

    1. All the classes that inherit from dds::core::Value<D> seem to be missing a copy-ctor. For example, QosPolicyCount in src\hpp\tdds\core\policy\QosPolicyCount.hpp. Without a copy-ctor, VS2010 issues a “cannot convert from ...” error.

    Most of these classes are found in the following files:

    src\hpp\tdds\core\InstanceHandle.hpp
    src\hpp\tdds\core\policy\CorePolicy.hpp
    src\hpp\tdds\core\policy\QosPolicyCount.hpp
    src\hpp\tdds\core\qos\EntityQos.hpp

    Proposed Solution: Add a copy constructor to all the classes that inherit from dds::core::Value<D> as follows:

    QosPolicyCount(const QosPolicyCount& src) : dds::core::Value<DELEGATE>(src.delegate()) { }

    2. The exception classes in dds-psm-cxx\src\hpp\dds\core\Exception.hpp do not need copy-ctor because there is nothing to copy and the base classes don’t have copy constructors either.

    Proposed resolution: Remove the declarations of copy constructors in dds-psm-cxx\src\hpp\dds\core\Exception.hpp

    3. The private constructor of SampleRejectedStatus in dds-psm-cxx-read-only\src\hpp\dds\core\status\State.hpp needs a typecast to avoid compilation errors on Visual studio versions of STL.

    The following constructor can’t be called due to ambiguous overloads of bistset<N> constructors.

    private: SampleRejectedState(uint32_t s) : MaskType(s) { }

    Proposed solution: Change the call to the base constructor to include an explicit static_cast to int.

    private: SampleRejectedState(uint32_t s) : MaskType(static_cast<int>(s)) { }

  • Reported: DDS-PSM-Cxx 1.0b1 — Fri, 17 Jun 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The Visual Studio C++ 2010 compiler was raising a series of errors and warning that were not caught by GCC relating to some lacking ctors and conversion operators in some template classes. All the errors raised by Visual Studio C++ 2010 have been addressed as verifiable on the latest version of the dds-psm-cxx source code available at https://github.com/kydos/dds-psm-cxx

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Dividing a scalar in Duration and Time classes

  • Key: DDSPSMC-4
  • Legacy Issue Number: 16308
  • Status: closed  
  • Source: Real-Time Innovations ( Sumant Tambe)
  • Summary:

    Duration and Time have some arithmetic operators that have the form:

    const Duration operator /(uint32_t lhs, const Duration& rhs);
    const Time operator /(uint32_t lhs, const Time& rhs);

    In the above, the intent of dividing a scalar by Duration/Time is not clear.

    Duration/N is conceivable but not N/Duration.

    Proposed solution:

    Remove the following free functions.
    const Duration operator /(uint32_t lhs, const Duration& rhs);

    const Time operator /(uint32_t lhs, const Time& rhs);

  • Reported: DDS-PSM-Cxx 1.0b1 — Wed, 1 Jun 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    Removed the operation:
    const Duration operator /(uint32_t lhs, const Duration& rhs);

    from the Duration class. The Time class did not have such a method to begin with.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

Union/array/bounded types lacking

  • Key: DDSPSMC-3
  • Legacy Issue Number: 16261
  • Status: closed  
  • Source: Remedy IT ( Johnny Willemsen)
  • Summary:

    The specification should describe the mapping for Union, Array, and the behavior for bounded strings (what happens if we go beyond the bound)

  • Reported: DDS-PSM-Cxx 1.0b1 — Tue, 24 May 2011 04:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    Arrays are now mapped to the dds::core::array<T,N> type which is designed to be compatible with C+11 arrays and thus to simplify idiomatic C11 usage as well as portability of DDS code to C+11 compilers.

    The table 7.1 in section 7.4.2 reflects the new mapping of array (see last column).

    Section 7.4.3 provides now a definition of the mapping for enumerations.

    Section 7.4.4 provides a definition of the mapping for unions.

  • Updated: Fri, 6 Mar 2015 20:58 GMT

factory methods on the "parents" (e.g. create_topic, create_data_writer, etc.)

  • Key: DDSPSMC-2
  • Legacy Issue Number: 15967
  • Status: closed  
  • Source: ADLINK Technology Ltd ( Angelo Corsaro)
  • Summary:

    The changes introduced in the final submission to support factory methods on
    the "parents" (e.g. create_topic, create_data_writer, etc.) has introduced a
    few issues.

    a. Reference types are not created in a uniform way. In essence,
    DomainParticipant, Subscriber, Publisher, DataReader and DataWriter
    types are instantiated using a different syntax than that used by
    WaitSets or Conditions. This is unfortunate as it reduces the
    consistency of the API.

    b. To eliminate the circular dependencies induced by the factory methods
    the API has to implement a few "creative" solutions that impact
    clarity as well as robustness. All of a sudden it is relatively hard
    to find where is defined what and also the include systems is very
    fragile, e.g. one can break the API very easily by mistakenly changing
    one include order.

    The changes suggested to the submission is to equip each
    Reference type with a factory method called "create". This not only allows to
    remove circular references, but it also allows for an organization of the API
    that is more robust and easier to follow. Furthermore, it ensures that
    all references are created in an uniform manner.

  • Reported: DDS-PSM-Cxx 1.0b1 — Mon, 17 Jan 2011 05:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The dds-psm-cxx API has been updated to remove the circular dependencies introduced by factory methods. Along with removing circular dependencies the API has been refactored to ensure that no forward includes are needed thus maintaining local, and thus clear and visible, the set of dependencies for each file. The necessary changes have been applied to all the DDS entities, such as DomainParticipant, Publisher and Subscriber.
    Examples in the specification have been updated to reflect the API change

  • Updated: Fri, 6 Mar 2015 20:58 GMT

XML-Based QoS Policy Settings (DDS-PSM-Cxx/DDS-PSM-Java)

  • Key: DDSPSMC-1
  • Legacy Issue Number: 15965
  • Status: closed  
  • Source: ADLINK Technology Ltd ( Angelo Corsaro)
  • Summary:

    The newly introduced XML Based Policy configuration adds new methods in the core DDS entities that allow to fetch QoS from XML filers. This solution is not ideal since if generalized, e.g. QoS configuration from an URI, JSON stream, etc., would lead to an explosion of the core DDS API.

    The suggestion is to remove the added methods from the core API and use instead a Builder pattern (of some form).

    A sketch of the suggested change is provided below:

    PolicyBuilder builder = PolicyBuilder::load("XMLBuilder");

    TopicQos tqos = builder.topic_qos(file_name, profile_name);

    ==============================================================================

    Notice that the suggested approach allows to easily extend the supported format for QoS representation w/o any impact on the core DDS API and overall facilitate the support for multiple approaches.

  • Reported: DDS-PSM-Cxx 1.0b1 — Mon, 17 Jan 2011 05:00 GMT
  • Disposition: Resolved — DDS-PSM-Cxx 1.0b2
  • Disposition Summary:

    The class dds::core::qos::TQoSProvider provider has been added to the C++ API to allow the external configuration of QoS. Section 7.6.2.1 of the specification document has been updated accordingly to describe the dds::core::TQoSProvider

  • Updated: Fri, 6 Mar 2015 20:58 GMT