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Question and idea for smart pointers
by Ion Gaztañaga 07 Jan '05

07 Jan '05

Hello to all, While developing the Boost Shmem library I needed to be independent of the pointer types (raw or smart), so I started looking for those functions in Boost. As I've seen an overloaded "get_pointer" function returns a raw pointer from a generic pointer, and I've made the same with the relative offset_ptr from Boost Shmem. But to treat all types of pointer generically I needed to obtain from a generic pointer a pointer to other type of the same class. I've solved this defining in my smart pointer an internal type following the STL allocator rebind mechanism: /*!Obtains offset_ptr <OtherType> from offset_ptr*/ template<typename OtherType> struct pointer_to_type { typedef my_smart_ptr<OtherType> type; }; and the structs: template <typename Ptr, typename NewValueType> struct pointer_to_other { typedef typename Ptr::template pointer_to_type<NewValueType>::type type; }; template <typename T, typename NewValueType> struct pointer_to_other<T*, NewValueType> { typedef NewValueType *type; }; so that the user can generically write: typedef pointer_to_other<NewType>(my_smart_ptr)::type new_pointer_t; and obtain a pointer of the same class (smart pointer or raw pointer) to other type. My question is, do you find this mechanism useful to include it in boost in a general way, and if so, is there another way of doing this without modifying existing classes (for example, if I want use these mechanism with shared_ptr)? Regards, /Ion

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patch: 3 bugs in pool.hpp
by Paul Du Bois 07 Jan '05

07 Jan '05

Please ignore my previous patch, if it ever made it through to the list. I have found 3 bugs in pool::release_memory(). I am under a bit of deadline pressure, so I'm sorry that I don't have the tuits to supply a tested patch for the tests :-). A tentative patch that fixes the bugs is appended, but it's only gotten the lightest of testing. I've tried to make the changes small, but the function is complicated enough that I'm afraid it's "no obvious bugs" rather than "obviously no bugs". Test case 1: ... block N all free Memory leak: blocks 0-(N-1) will be lost from the block list, because prev isn't being updated correctly. Test case 2: block 0 some non-free block 1 no free block 2 all free block 2 will not be deallocated, because prev_free is erroneously advanced too many times. There are other failure modes of this sort, but this is the simplest. Test case 3 (theoretical; the others happened to me block 0 some non-free ... block N (last block) chunks 0-m are free, and m+1 to the end are non-free Thus, m is the end of the freelist Crash: trying to call nextof(0).

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cvs tarball
by Toon Knapen 07 Jan '05

07 Jan '05

I'm looking for a tarball of the current CVS HEAD. Metacomm apparantly provides one for the 1.32 release, but not for the head (or am I wrong?) and the tarball on sourceforge is corrupt (I saw that David reported the sourceforge tarball to be corrupt on 14/oct/2004) toon

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FYI: Improved GMane Archive Search
by David Abrahams 06 Jan '05

06 Jan '05

Lars Magne Ingebrigtsen, the man behind GMane, recently told me about a new search facility: "<URL: http://rain.gmane.org/> -- it's a Xapian-powered search. It's still in beta, and recent articles aren't in its index. You can advertise it, but it's likely to be out of commission now and then as the Xapian people work on it." Now you know all. It does seem to be wicked fast. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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Boost General Interest mailing list
by Jon Kalb 06 Jan '05

06 Jan '05

Boosters, This messages announces the Boost General Interest mailing list, called Boost-Interest. This list is a moderated low-traffic announcement-only list of interest to the Boost community. On topic messages will include announcements of books, magazine articles, papers, talks, seminars, products, tools, events, or conferences on advanced uses of C++, generic/generative/meta-programming, and, of course, the Boost libraries. Off topic will be discussion of any kind and job postings. Yes, this is an opt-in list for announcements, but it is a moderated list and the moderators make you two promises. This list will be low volume and all messages will be on-topic (as defined by the charter above). Subscribe or unsubscribe at the Boost-Interest home page: http://lists.boost.org/mailman/listinfo.cgi/boost-interest Anyone may post to this list, but due to the high potential for abuse, each message is individually moderated. Please anticipate some delays in posting and understand that the list moderators have the final say on what is or is not on-topic. -- Jon Kalb Boost-Interest Moderator Kalb(a)LibertySoft.com

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[type_traits] request for decayed<T>::type
by Thorsten Ottosen 06 Jan '05

06 Jan '05

Hi, The following trait is supposed to make it easier to forward arguments in generic code and in particular string literals. For example, I will use it when I update boost.assign to use const T& arguments instead of T arguments. It could also be used to make a better version of std::make_pair(): template< class F, class S > inline std::pair< typename decayed<F>::type, typename decayed<S>::type > make_pair( const F& f, const S& s ) { return std::pair< typename decayed<F>::type, typename decayed<S>::type >( f, s ); } Any thoughts from the type_traits authors? Do anybody mind if I add this to the cvs and make some docs for the type-traits library? br -Thorsten begin 666 decayed.cpp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` end

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Boost Shmem BoostBook Help uploaded to Boost Files
by Ion Gaztañaga 06 Jan '05

06 Jan '05

Hello to all, I've just uploaded the Boost Shmem library help to Boost Files section (Boost.Shmem.2005-01-04.help.zip) so anyone can have a look and see what the library does without building the documentation. The documentation is in BoostBook format. Feel free to comment, regards, /Ion

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Archive stuck?
by Gennadiy Rozental 06 Jan '05

06 Jan '05

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Re: Singleton
by Dave Handley 06 Jan '05

06 Jan '05

> Does it make any sense to use a template allocator parameter, like the > standard container types, to control creation and destruction of my > instance, or are new and delete sufficient? Singleton creation is an interesting issue - Loki provides a number of different creation policies, including creating using new, malloc, or creating statically. Implementing them with a policy template. > Is there any other functionality that should be added? Specifically, > is it sufficient to enforce that singletons are created in a specific > order before main and destroyed in the reverse order after main (using > dependency instances), or should I provide some way to support > alternate lifetimes (ex: create on first reference to instance)? Ordering of Singletons is, in my opinion, one of the most important issues with Singletons. It is almost certainly insufficient in most applications to create in a specific order, and delete in reverse order. One reason for this is start-up performance - you don't want every Singleton to have to create at startup (necessarily). Another reason can be memory efficiency. Loki again provides a number of policies including a Phoenix Singleton and a Longevity managed singleton. I personally tend to use Longevity managed singletons linked to the at_exit function. Nevertheless, there are some additional things that I would like to see - for example, a phoenix singleton that could be created and destroyed more than once during a program run could be useful - either explicitly or even if not used for a while. Also, allowing thread-safety as an option is also crucial. > Is there any interest in adding this library to Boost? I would love to see a robust implementation of a Singleton in Boost. Whenever I start a software project, almost without exception I tend to add both Boost and Loki to the project - it would be great if I could add only Boost. I have to say however, that a more general library which implemented a variety of design patterns (like Loki) would be even better. For example: 1) Singleton 2) Visitor - like Loki implementing both a conventional cyclic visitor, and an acyclic visitor. 3) Composite 4) Abstract Factory 5) etc. etc. I've written my own templatised composite (available on codeproject.com) implementing a number of different iteration strategies (deep iteration, shallow iteration, typed iteration, etc.) and would be more than willing to throw that into the melting pot if there was some interest in putting together a library of design patterns for Boost. I've also written an acyclic visitor, like Loki but with a key change in the way that a failed visit is handled - in Loki if the visitor cannot visit a particular type of node, the default action is handled by a template in the base class of the visitable hierarchy. This in my view is flawed, and the default action should actually be handled by the visitor if required - this keeps the concept of action and data separated in accordance with the original visitor design pattern. This would probably need some work if it was to go into any attempt at a design patterns library. Dave Handley

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g++ STL/MPL conflicts?
by Arkadiy Vertleyb 06 Jan '05

06 Jan '05

Hi all, I was porting my older stuff into Boost 1.32, and it went fine with VC71. However, using g++ 3.3, I ran into a lot of naming conflicts between STL and MPL algoritms, such as find_if, copy_if, etc. From looking into previous posts, I can see that tis relates to a combination of problems in the g++ STL, such as using unqualified calls, and ADL not working correctly. Does anybody know if the problem was fixed in later versions of GCC? Thanks, Arkadiy

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