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[Serialize] error 'unable to start program' with demo.cpp compiled in debug mode under msvc7.1
by David Körner 07 Dec '08

07 Dec '08

Hi, when I compile the demo.cpp from the boost.serialize tutorial in release mode everything works fine. But when I compile it in debug mode the application wont start and the error 'unable to start program' is displayed. It further says that the application has failed to start because the configuration is incorrect. When I change something and do a recompile - the compiler fails: 'unable to update manifest. wrong parameter'. I then have to do a clean+rebuild and it compiles again but wont run until I comment out every boost.serialize code. I use MSVC7.1 (VS2005). I already have used the serialize library with boost version 1.34 successfully. Can someone help me with that issue? Has anybody experienced similar problems? Any help or hint would be appreciated. Thank you very much in advance. David _________________________________________________________________ Wer erfand den Glückskeks? Kleiner Tipp: Die Chinesen waren es nicht! - Mehr auf msn.de http://redirect.gimas.net/?n=M0812xMSNDE

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Re: [boost] [UUID] Code for UUIDs as PODs and other changes
by Vladimir Batov 07 Dec '08

07 Dec '08

Scott, Many thanks for your crash-course on aggregates and your patence with me. Much and truly appreciated. I had to dig the Standard up for a "refreshment". It's embarassing but I admit I all forgot about that "C" stuff tucked away in a corner of C++. I never thought I'd come across it ever again. Kudos to you for your effort. I am coming to appreciate your implementation. It's very impressive how efficiently you managed to cut off "all the excess" and how far you've got without C++ "perks and whistles". I am sure it had its uses. That said, I feel aggregates' limitations are far too restrictive for a full-fledged implementation (and especially the interface). Best, Vladimir. > ... > It comes from making it a POD, as all PODs are also aggregates. > > 8.5.1 Aggregates [dcl.init.aggr] > > An aggregate is an array or a class (clause 9) with no user-declared > constructors (12.1), no private or protected non-static data members > (clause 11), no base classes (clause 10), and no virtual functions > (10.3). When an aggregate is initialized the initializer can contain > an initializer-clause consisting of a brace-enclosed, comma-separated > list of initializer-clauses for the members of the aggregate, written > in increasing subscript or member order. If the aggregate contains > subaggregates, this rule applies recursively to the members of the > subaggregate.

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Re: [boost] [UUID] Code for UUIDs as PODs and other changes
by Vladimir Batov 07 Dec '08

07 Dec '08

... > >> uuid u = { /* 6ba7b814-9dad-11d1-80b4-00c04fd430c8 */ > >> 0x6b, 0xa7, 0xb8, 0x14, > >> 0x9d, 0xad, > >> 0x11, 0xd1, > >> 0x80, 0xb4, > >> 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8 > >> }; > > > > I am not sure as a user I'd be interested in doing that kind of low-level stuff and in fact I am doubtful it'll even compile. > > > > It does work, actually. I use it to implement > uuids::namespaces::dns() and friends. It compiles indeed! Tried MSVC++9 and even ol' gcc 3.4.4. C++0X talks about initialization of that kind but for standard containers. To me it feels like very non-standard behavior. What am I missing? Someone help me out here. > 4.1.7. Nil UUID > > The nil UUID is special form of UUID that is specified to have all > 128 bits set to zero. > > I'm not particularly attached to nil(), but at the same time, I don't > have any better name. I dislike null(), when people are used to > treating NULL as pointer (even when it actually isn't). C# uses > Empty, but that's also not great, since empty is strongly entrenched > through its use in the Container concept. Fair enough. The standard expicitly mentioning uuid::nil() sounds like a good reason. > Really, I'd be plenty happy to get rid of it entirely, since value > initialization provides the same functionality: uuid id = uuid(); Have to disagree as to me the above is unclear as I am not sure if it means "create a new uuid" or "create an invalid uuid". I prefer saying clearly what I mean, i.e. uuid id(uuid::nil()); Best, Vladimir.

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Re: [boost] [UUID] Code for UUIDs as PODs and other changes
by Vladimir Batov 07 Dec '08

07 Dec '08

> PODness: I am personally far from thrilled and fail to see benefits of that move. > As a POD, all the constructors are of course gone. Well, "constructors are of course *not* gone" as the default and copy constructors will be generated for you. The auto-generated default constructor does not seem to initialize the underlying boost::array to anything. Therefore, I suspect "uuid id;" will be left uninitialized. > ... > I don't think that serialization to and from strings > belongs in the type, and it seems like using a lexical_cast is > perfectly reasonable: Yes, taking out the conversions to/from string certainly make the UUID-related code/interface cleaner. More so, IMHO lexical_cast has become somewhat idiomatic for that kind of tasks and provides the well-defined and well-known path to enable the functionality. Much preferred. > ... > I don't know if it's useful, but aggregate syntax also opens > possibilities: > > uuid u = { /* 6ba7b814-9dad-11d1-80b4-00c04fd430c8 */ > 0x6b, 0xa7, 0xb8, 0x14, > 0x9d, 0xad, > 0x11, 0xd1, > 0x80, 0xb4, > 0x00, 0xc0, 0x4f, 0xd4, 0x30, 0xc8 > }; I am not sure as a user I'd be interested in doing that kind of low-level stuff and in fact I am doubtful it'll even compile. I see nil() introduced in the code with "As named in RFC 4112, 4.1.7" comment. I tried googling for "RFC 4112" and it gave me "RFC4112 - Electronic Commerce Modeling Language (ECML) Version" with no "nil" mentioned. I have no issues with "nil" pre se as it's well-entrenched in other languages. However, I feel that C/C++ settled on "null" (and C++ 0x introduces nullptr). So, I fail to see any reasons to deviate from that. >> ... the rest snipped. I see a lot of code cleanup, reorganization and reshuffling. Everything has its place and time. Even though I agree that at some point it needs to be done, I do not feel we've reached that point. I'd much prefer to focus on providing well-thought-through interface. Without having agreed on the interface and settling on what and how certain functionality is delivered to the user I feel that "implementation-detail" discussions seem premature and in fact distracting at this point. Best, Vladimir.

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Re: [boost] [Review] UUID library (mini-)review starts today, November 23rd
by Vladimir.Batov＠wrsa.com.au 07 Dec '08

07 Dec '08

> ... > Hmm, I looked at some other value types in boost and this is what I > found. > > boost::gregorian::date() creates an 'not_a_date_time'. > One can exclude this constructor with a #define. > boost::posix_time::ptime() is the same as above > boost::function() is initialized as empty > std::string() is initialized as empty > boost::numeric::interval() the created interval is the singleton zero > boost::quaternion() initialized each component/member to the default > values for their type (i.e. zero for floating numbers) > boost::optional() is uninitialized > boost::rational() is 'zero' Some usages are legitimate (like an empty std::string is still a string and boost::rational() default initialization to 0). Some usages are IMHO mildly confusing (like boost::function()) as there is a clear understanding that it has to have some function, i.e. no-function is clearly invalid. Some others are IMHO unfortunate and quite confusing -- does boost::gregorian::date() mean 'not_a_date_time' or boost::gregorian::date() means 'now'? My view is that the interface needs to be intuitive. With the date I would not probably use the default constructor at all as it is not immediately clear what it does. Instead I'd have boost::date::invalid() and boost::date::now(). Deploying the default constructor for something apart from default construction is a hack unfortunately abused quite often. It does not make it right though. > ... > And, what should the default constructor do? Create a null uuid or a > unique one? It feels like you are struggling to associate the default constructor with something. :-) You know, you really do not have to. The default constructor has quite a clear meaning. If a class has no functionality matching that meaning, that class should not be defining the default constructor and should not be hijacking that constructor for anything else. Convenient? Sure. Good API? Hmm, I am not sure -- a good interface should be saying what it means. > ... > This is what I want to prevent as well. I'm concerned about the user > who does: > boost::uuid u; // this create a unique uuid > and does not realize that they just ran a computational intensive > function when they didn't need or want to. I am not sure what there is not to realize? The language is clear that "boost::uuid u" calls the default constructor... whatever that constructor does (intensive or not). Treating object creation as it were built-in types (i.e. created uninitialized/invalid) is wrong, encourages the wrong programming practice and expectations and should not be encouraged. > ... > Fair. These people are likely either doing: > > boost::uuid u = get_uuid_from_somewhere(); // eg from database > > or > > boost::uuid u; > get_uuid_from_somewhere(u); // eg from database > > The second case would create a unique uuid unless they remembered to do: > boost::uuid u(boost::uuid::null()); There is a big difference between #1 and #2 and the language is lucidly clear what the difference is -- #1 does just one step and creates and object from another object; #2 does 2 steps -- creates an object with the default constructor and then applies operator=(). Painting over that difference and encouraging user's ignorance of that important subtlety (for a novice) won't do anyone any good. > It sounds very easy for one to forget. This doesn't change symentics, > it is just less efficient. It *does* change semantics and it does change execution flow and the language cannot be any clearer on that. If you mean #1, then instead of making #2 to behave like #1, I'd prohibit #2 altogether by not providing the default constructor. Having said that to *me* "boost::uuid id;" makes sense as I read it as the language describes -- I create a UUUID with the default constructor. My interpretation of it is that I trust the implementer to do the right thing for me -- the user. I'd say, if that interpretation is subtle and really controversial, just get rid of the default constructor altogether. In the end, it's just my view. I am not prepared to die fighting for it. :-) Thanks, Vladimir.

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A design for geometric objects
by Mathias Gaunard 06 Dec '08

06 Dec '08

The past discussions on geometric libraries focused on how to define points. What matters even more however is how geometric objects are designed. There is a natural subtyping relationship between geometric objects. Deriving a square from a rectangle is usually frowned upon in OOP, because it can easily break the Liskov Substitution Principle if the objects are mutable. Making them immutable, however, solves the issue altogether. Morever, by using static subtyping, e.g. with concepts, we have multiple dispatch for free and don't pay any performance overhead, making such a design much better than with OOP. Concepts being non-intrusive, a mutable object may well be implemented but the concept can be a read-only view. Note that while I'm talking about concepts, I don't necessarily mean C++0x concepts, it could also be an alternative system. I would like to be able to write generic algorithms for geometric objects. Say I write an algorithm for any simple polygon. That algorithm should work with any simple quadrilateral, simple triangle, a rectangle, etc. Then I rewrite the same algorithm for convex polygons. So non-convex simple polygons should invoke the old algorithm, and convex ones the new one. So a system to find best matches is required. If we consider the subtyping graph for rectangle (which is not the most complex object, but certainly is complex enough to expose a complex graph), here is what we get: Rectangle < Right-angled Trapezium < Trapezium < ConvexQuadrilateral < Parallelogram < Trapezium ConvexQuadrilateral < SimpleQuadrilateral < Quadrilateral < Polygon < ConvexPolygon < SimplePolygon SimplePolygon < InsideSimplePolygonalLine SimplePolygon < Polygon Polygon < PolygonHole < Curve Polygon < InsidePolygonalLine InsideSimplePolygonalLine < InsideSimpleClosedCurve InsideSimplePolygonalLine < InsidePolygonalLine < InsideClosedCurve InsideSimpleClosedCurve < InsideClosedCurve < Curve SimpleClosedCurve < ClosedCurve < Curve InsideSimpleClosedCurve -> SimpleClosedCurve (composition thingy) InsideClosedCurve -> ClosedCurve (composition thingy) Curve < Object For clarification, a curve is here defined as the image of a continuous map from a real interval to the space. That is to say any set of points that is "connected". A simple curve is a curve that doesn't cross itself (just like simple polygons), which means the the map is injective, and a closed curve is a curve where the application comes from a closed interval and where the image is the same on both boundaries. A closed simple curve is a closed curve that is injective but for the boundaries. InsideClosedCurve defines the space with is "inside" a closed curve, which could also be defined by another map (known as a space-filling curve, but they are harder to manipulate, at least for polygons). A Polygon is an InsideClosedCurve with the closed curve being line segments within a plan. A PolygonHole is a Polygon which may have holes themselves defined by closed curves. An Object is a possibly (likely, even) infinite set of points in space. There is quite a complexity and redundancy here. It would be nice if it was possible to enhance that somehow. And that graph probably isn't fully complete, for example "right-angled" should probably be made separate propriety from trapezium. Also there should probably be Polytope somewhere. And PolygonHole lacks specializations too. The worse is the Inside thingies. I suppose having template concepts of some kind could help. Therefore I am wondering if there is any way to make the design simpler and more elegant. Indeed, such a design seems hard to maintain, it doesn't scale so well, and if I want to include something in there I probably have to modify other concepts as well. A geometric object is really just a set of proprieties. Working with meta-functions like is_quadrilateral, is_convex or is_simple seems like less work and verbosity. But how can such a system provide subtyping and best matches? Any comments and ideas are welcome.

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[python] Python 3.0
by Robert Dailey 06 Dec '08

06 Dec '08

Will Boost.Python 1.37 work with the Python 3.0 library?

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Re: [boost] [Review] UUID library (mini-)review starts today, November 23rd
by Vladimir Batov 06 Dec '08

06 Dec '08

> ... > All in all my impression of the *current* situation with the proposal is > that at *present* we have many useful and promising bits and pieces lying > around. I see good ideas. I see good suggestions. I fail to see the > product. It surely is a good start but to me we have not reached the > destination yet. I'd be more comfortable after I see those bits and pieces > taking shape. For me that shape primarily would be the interface and the > documentation -- the initial pieces of the contract between the user and > the implementor. Once both parties are happy with the contract, you'll > beaver away providing the content/implementation. Now that I looked at the code once again, I think I'd like to take back the "bits and pieces lying around" bit (as it feels plain wrong and I think I need better glasses to see things the first time around :-)). In fact, I feel that all the pieces are more/less in place and I'll be very much in content if I see something along the following lines: namespace boost { class uuid { struct time_generator; struct random_generator; struct best_generator; template<class Generator> uuid(Generator const&) {...} or template<class Generator> uuid(Generator const& =best_generator()) {...} static uuid null() { ... } typedef void (base::*bool_type)(); void internal_bool() {}; operator bool_type() const { return *this == null() ? 0 : &base::internal_bool; } ... }; struct uuid::time_generator { ... }; struct uuid::random_generator { ... }; struct uuid::best_generator { ... }; } // boost Replacing is_null() with the implicit "bool" converter is not a syntactic sugar. It's very much idiomatic along the same lines as "a + b" is better than "a.add(b)". I'd probably look at deploying Boost.Range functionality as I see many constructors working with ranges. With that caveat I think I am all willing to abandon my original (a very lonely BTW) position and run over to the happy 'yes' campers. Thanks, Vladimir.

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Re: [boost] [UUID] Code for UUIDs as PODs and other changes
by Scott McMurray 06 Dec '08

06 Dec '08

On Sat, Dec 6, 2008 at 14:07, Roman Yakovenko <roman.yakovenko(a)gmail.com> wrote: > On Sat, Dec 6, 2008 at 11:10 AM, Scott McMurray <me22.ca+boost(a)gmail.com> wrote: >> I remarked the other day that a UUID has a well-defined, portable >> binary format, so I took a bit of time to rearrange things to make the >> UUID class a POD and make more use of the generators idea. Along the >> way I made a few other changes. >> >> I've uploaded the result (with updated docs) to the vault as >> uuid_alt_v13_pod.zip : >> http://www.boostpro.com/vault/index.php?action=downloadfile&filename=uuid_a… >> >> Some elaboration follows below. Comments appreciated. > > Hi. Very nice implementation. I have few question: > Thanks, though most of the implementation credit still goes to Andy. > 1. Why variant() and version() are member function of class uuid? I > think they should be free functions. > Either way would work, obviously. I thought of them as properties of the UUID, rather than some computed thing, but that's an iffy difference, so for normal encapsulation justifications it may better to make them non-member. > 2. May be it is better to introduce "native_generator" which is cross platform? > There is actually a typedef for that. I figured that it would be better to keep the implementations separate and conditionally compile the typedef, rather than try to mix the 2 (or more, if other platforms) implementations into one. That said, strategies would also work nicely for that, and would allow cross-platform specification of which UUID version you'd like, too...

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[shared_ptr] Two suggestions for the aliasing constructor
by Clive Jones 06 Dec '08

06 Dec '08

1) An aliasing constructor that takes an rvalue reference Motivating example: in my code I have a utility function... template <typename T, typename Y> boost::shared_ptr<T> shared_ptr_to_member(const boost::shared_ptr<Y> &ptr, T Y::*ptr_to_member) { return boost::shared_ptr<T>(ptr, &(ptr.get()->*ptr_to_member)); } ...which seems to me a prime candidate for having an overload that takes an rvalue reference. The implementation would be very simple, by direct analogy with the existing aliasing constructor and rvalue constructor. template< class Y > shared_ptr( shared_ptr<Y> && r, T * p ): px( p ), pn() // never throws { pn.swap( r.pn ); r.px = 0; } 2) Refactor the pointer_cast functions to use the aliasing constructor The pointer casting functions were implemented before the aliasing constructor was available; using it, simpler implementation is possible. For example, rewriting static_pointer_cast as: template<class T, class U> shared_ptr<T> static_pointer_cast(shared_ptr<U> const & r) { return shared_ptr<T>(r, static_cast<T *>(r.get())); } ...allows the removal of boost::detail::static_cast_tag and the shared_ptr constructor that accepts it. Regards, --Clive.

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