- Boost - lists.boost.org

singleton design plan
by Jason Hise 03 Aug '05

03 Aug '05

This message is an in depth description of my current design plan for a new singleton library, which I hope to complete and schedule for review by boost in the coming year. I would appreciate any comments, questions, or suggestions regarding this plan before I begin work on the code. Specifically, I would like to know if there are any important issues that this design fails to address, or difficulties with the interface that would turn away potential users. (My old singleton library, which was not accepted by boost, is available at http://tinyurl.com/6qvrd. It was rejected primarily because it failed to adequately address concerns related to multi threading and dlls.) Thus far, my high level design plan looks like this: The creator_policy defines fundamental pointer, const_pointer, and reference types. These hold references to a creator policy instance which maintains the singleton internally, so that the pointer types can always see and access the state of the single instance. This way, pointers to the singleton instance are not invalidated when the state of the singleton changes. The creator_policy defines create, replace, and destroy methods, as well as methods to generate instances of the various pointer types. Create only creates the instance if it does not already exist, destroy only destroys the instance if it does exist, and replace makes sure any existing instance is destroyed before attempting creation. Thus far, I hope to support the following creators: -------------------------------------------------------------------------------- in_place_creator creates/destroys inside an aligned_storage POD interface: create ( [ctor params] ); replace ( [ctor params] ); destroy ( ); pros: no memory allocation/deallocation ever required constructor params can be easily specified cons: automatic creation, when it occurs, always uses the default constructor singleton cannot be created as a derived type useful for simple, user defined singleton classes -------------------------------------------------------------------------------- source_sink_creator owns fixed source and sink functors, specified with template parameters interface: create ( ); replace ( ); destroy ( ); pros: source can return a derived type automatic creation uses source rather than default construction cons: source and sink cannot be set or changed at runtime constructor arguments cannot be specified by calling code useful for singleton types provided by untouchable code, which may require calling special functions to get pointers to instances -------------------------------------------------------------------------------- dynamic_source_sink_creator owns dynamic source and sink functors interface: create ( [source[, sink]] ); replace ( [source[, sink]] ); destroy ( [source[, sink]] ); pros: source can return a derived type automatic creation uses source rather than default construction source and sink can optionally be changed at run time source and sink can change functor types when they are set (example: from function pointer to lambda expression) cons: specifying constructor parameters to pass is non-trivial dynamic memory allocation and virtual functions must be used to store the functors in order to allow for different functor types at runtime, thus creation is more expensive and can potentially fail useful for a singleton which needs to take the forms of unspecified derived types and is frequently destroyed and created via some type of factory -------------------------------------------------------------------------------- The lifetime_policy owns and wraps the creator policy, and provides pointer and reference types which wrap those belonging to the creator. It also provides functions to generate instances of the various pointer types, and provides a function to access the creator_policy instance. The unmanaged lifetime simply typedefs the underlying pointer and reference types, and thus results in no overhead. The longevity_lifetime and lifo_lifetime behave similarly, but handle scheduling of automated destruction when any of the pointer generation methods are called. The dependency_lifetime will wrap the internal pointer types to perform reference counting (the reference count itself will be stored in the lifetime_policy instance). The timeout_lifetime will manage a separate thread that releases the instance when it finishes counting down. It will also wrap the internal pointer types to reset the timer when a pointer is dereferenced, and reset and lock the timer while any references exist. The threading_policy owns and serializes access to the lifetime_policy. It also has a function to get access to the lifetime_policy instance, and provides pointer, const_pointer, and reference types which wrap and forward to the lifetime's corresponding types. For the single_threaded policy, these pointer types are simply typedefs of the lifetime's pointer types, resulting in no overhead, and the function through which the lifetime_policy instance is accessed just returns a raw pointer to it. For the multi_threaded policy, pointer types perform locking before forwarding to lifetime pointer types, and the reference type acts as a lock throughout it's existence. The mutex is stored inside the threading_policy instance. The function which returns a pointer to the lifetime_policy instance returns a smart pointer which serializes access. A storage_policy determines how instances of the threading_policy are stored (and because these instances contain instances of the other policies, this indirectly controls how all of the policy instances are stored). static_storage stores policy instances directly as global variables, which is fine for singletons that are not required to have a specific lifetime with regard to other singletons. These global variables will be set up in such a way that it will be guaranteed that any automatic destruction takes place before the policy bundle is destroyed. group_storage allows multiple singletons to have their policies stored in a master group. No policies in this group are destroyed until all automated destruction that will be performed by any members of the group has completed. This way, if destructors of some of the singletons in this group trigger re-creation of other singletons in the same group, the policies needed to recreate the singletons are guaranteed to still exist. dll_storage requires linking with singleton.dll, and stores instances in a special exported manager singleton to ensure unique singleton instances across dll boundaries. All policy instances of this type are guaranteed to be destroyed only after all automated destruction has taken place. A singleton class exists, which takes a singleton type and a name tag as template parameters. The name will have a default type called 'unnamed'. This name parameter enables using multiple singleton instances of the same type. Policies are traits of the name specified, so using the default name 'unnamed' results in using the default policies. Policies can be specified by declaring a name as an undefined struct, and then specializing the desired policy traits for that name. The singleton class contains three pointer types, which wrap those of the threading policy. These are strong_pointer, lazy_pointer, and weak_pointer. strong_pointer attempts automatic creation of the singleton instance if it does not exist when the pointer is first created, and also attempts automatic creation if needed any time it is dereferenced. lazy_pointer only attempts automatic creation when dereferenced, and weak_pointer will never create the instance automatically. For the lifo_lifetime, a strong_pointer can be used to specify a dependency of some singleton B on some singleton A by having B own a strong_pointer to A. This will ensure that A is created before B and destroyed after B. Const versions of these three pointer types will also exist. Creation, destruction, and non-const member functions will not be allowed to be called through these const pointer types. A single reference type will exist which will be the result of dereferencing any pointer type via the unary * operator. const_pointers return const qualified references. Pointers only perform temporary locking (if the threading policy supports locking) when a member function is called via the -> operator or when a create or destroy operation is invoked. References lock the singleton throughout their entire lifetime, and thus can be used to make a series of operations on the singleton instance atomic. A reference provides an implicit conversion to a raw reference of the singleton's type (which comes back const if the reference is const). Create and destroy can only be called on non-const references. Typical code will access a singleton instance by creating one of the above pointer types and calling member functions through it via the -> operator. Ex: singleton < MyType, SomeName >::lazy_pointer ptr; ptr->DoSomething ( ); -------------------------------------------------------------------------------- I plan to sneak an improved version of the null developed by Scott Meyers in with this code in a header called boost/null.hpp, and use it in the singleton's implementation. It will be defined as follows: namespace boost { const class { private: void operator & ( ) const; public: #ifndef BOOST_NO_MEMBER_TEMPLATES // provide conversion to any pointer type template < typename Class, typename Type > operator Type Class::* ( ) const { return 0; } template < typename Type > operator Type * ( ) const { return 0; } #else //provide conversion to int if member templates are not supported operator int ( ) const { return 0; } #endif//BOOST_NO_MEMBER_TEMPLATES } null; } #undef NULL #define NULL (::boost::null) -------------------------------------------------------------------------------- Any and all comments or suggestions on this plan are welcomed. Potential problems are much easier to address at design time than after the code is written. -Jason

8 20

[signals] Signals 1.33 dylib crashes when used with Xcode
by Chiedo Acholonu 02 Aug '05

02 Aug '05

I'm using boost 1.33 and recently tried to build the signals dll using the darwin toolset. I then created a simple Xcode project called TestSignals to test it was working correctly. The project only contains the maximum.cpp example file (/boost-root/libs/signals/examples/maximum.cpp) linked against the signals dynamic library. The project builds just fine, but when I run the app, Xcode crashes with: "TestSignals has exited due to signal 10 (SIGBUS)." Here is a piece of the crash log (I can send the full log on request): --- Exception: EXC_BAD_ACCESS (0x0001) Codes: KERN_PROTECTION_FAILURE (0x0002) at 0x00000000 Thread 0 Crashed: 0 maximum.ob 0x0040c844 std::less<int>::operator()(int const&, int const&) const + 48 (stl_function.h:227) --- I tried using different example files, and they all crash. The library is built multithreaded and I do define BOOST_SIGNALS_DYN_LINK in my project. I'm running on Tiger 10.4.2 using Xcode 2.1. Has anyone tried this or run into a similar problem? Thanks, Chiedo

1 0

singleton, dlls, and shared memory
by Jason Hise 02 Aug '05

02 Aug '05

I was researching how to ensure that a singleton has only one instance within a loaded dll and came up with this: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/ba… The page has a lot of information, and while most of it makes a decent amount of sense, a good deal of it is still unfamiliar territory for me. So I have a few of questions. A) Security Attributes. How important are they? Is it ok to just use null for this parameter, or should I be researching this structure and its effects in depth? B) Size of shared memory. It appears that the 'pseudo file' being used as shared memory is fixed in size and thus I have to guess how much I might need at compile time. Is there a way to resize this file if need be? C) Allocating and deallocating the memory. Is there existing code out there that takes a buffer of memory like this and manages malloc/free like calls to it (possibly wrapping the functionality in a std allocator) or do I need to roll my own? -Jason

1 0

[Boost-bugs] [ boost-Patches-1249809 ] Minor spell errors on lambda_functor_base.hpp header
by SourceForge.net 02 Aug '05

02 Aug '05

Patches item #1249809, was opened at 2005-08-01 22:57 Message generated for change (Settings changed) made by urzuga You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=307586&aid=1249809&group_… Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: None >Status: Closed Resolution: Fixed Priority: 5 Submitted By: Duilio J. Protti (dprotti) Assigned to: Nobody/Anonymous (nobody) Summary: Minor spell errors on lambda_functor_base.hpp header Initial Comment: Attached is the patch with the corresponding corrections. The patch is not just for /boost/lambda/detail/lambda_functor_base.hpp file, but also for lambda_fwd.hpp. Bye, Duilio Protti. ---------------------------------------------------------------------- Comment By: Jaakko Järvi (urzuga) Date: 2005-08-02 20:49 Message: Logged In: YES user_id=284669 Fixed ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=307586&aid=1249809&group_… ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ Boost-bugs mailing list Boost-bugs(a)lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/boost-bugs

1 0

[Boost-bugs] [ boost-Patches-1249809 ] Minor spell errors on lambda_functor_base.hpp header
by SourceForge.net 02 Aug '05

02 Aug '05

Patches item #1249809, was opened at 2005-08-01 22:57 Message generated for change (Comment added) made by urzuga You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=307586&aid=1249809&group_… Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: None Status: Open >Resolution: Fixed Priority: 5 Submitted By: Duilio J. Protti (dprotti) Assigned to: Nobody/Anonymous (nobody) Summary: Minor spell errors on lambda_functor_base.hpp header Initial Comment: Attached is the patch with the corresponding corrections. The patch is not just for /boost/lambda/detail/lambda_functor_base.hpp file, but also for lambda_fwd.hpp. Bye, Duilio Protti. ---------------------------------------------------------------------- >Comment By: Jaakko Järvi (urzuga) Date: 2005-08-02 20:49 Message: Logged In: YES user_id=284669 Fixed ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=307586&aid=1249809&group_… ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ Boost-bugs mailing list Boost-bugs(a)lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/boost-bugs

1 0

[Announcement] LCSD'05 Call for papers, extended deadline
by jarvi 02 Aug '05

02 Aug '05

The following call for papers should be of interest to many in the Boost community. For more information, see http://lcsd05.cs.tamu.edu Posting the announcement has been approved by Boost moderators. Best, Jaakko Järvi ----------------------------------------------------------------------- LIBRARY-CENTRIC SOFTWARE DESIGN - LCSD'05 Workshop, on Sunday, October 16, 2005 at the Object-Oriented Programming, Systems, Languages and Applications (OOPSLA'05) conference in San Diego, California, October 16-20, 2005 ----------------------------------------------------------------------- CALL FOR PAPERS --- EXTENDED DEADLINE The deadline for submission has been extended to Aug 07, 2005. ----------------------------------------------------------------------- Libraries are central to all major scientific, engineering, and business areas, yet the design, implementation, and use of libraries are underdeveloped arts. This workshop is one of the first steps in the process of placing all aspects of libraries on a sound technical and scientific basis through research into fundamental issues and documentation of best practices. A software library is an organized collection of code with associated tools supporting programming in general or in specific domains, usually united by a specified set of principles and conventions. Most libraries are aimed at the use by several people and in different environments. The areas of software library research include * Design and implementation of libraries * Program and system design based on libraries * Libraries supporting specific application domains, such as biology and banking * Evolution, refactoring, and maintenance of libraries * Empirical studies of library use * Performance of libraries, including benchmarking and library-based optimizations * Design of language facilities and tools in support of library definition and use * Validation, debugging, and testing of libraries * Extensibility, parameterization, and customization * Distribution of libraries * Specification of libraries and their semantics * Usability for library users and developers * Assessing quality of libraries * Documentation and teaching of libraries * Creating and supporting communities of library users * Using several libraries in combination We invite the submission of extended abstracts on software library research, including, but not limited to, the above list of topics. The extended abstracts should address issues important to libraries as a field, i.e., describe ideas or techniques that can be reused for libraries across problem domains and/or languages; they should refrain from merely describing a particular library, no matter how novel the choice of domain. As an additional criterion, the extended abstracts are reviewed against suitability for a journal publication of the corresponding full paper. For uniformity, authors should use the latest ACM SIGS conference style file (option 1) at http://www.acm.org/sigs/pubs/proceed/template.html. Submissions should be limited to 10 pages in this style. Accepted extended abstracts will be posted on the workshop's Web site prior to the workshop, and collected in a proceedings published as a Rensselaer Polytechnic Institute tech report. Authors of selected papers will be invited to submit a full paper for a special issue of a journal, to be announced later. IMPORTANT DATES Aug 7 Submission of extended abstracts (extended from Jul 31) Sep 9 Notification of acceptance Oct 4 Final version posted on workshop Web site Oct 16 Workshop SUBMISSION PROCEDURE For details of the electronic submission procedure, see the workshop's Web site, http://lcsd05.cs.tamu.edu. ORGANIZERS * David Musser, Rensselaer Polytechnic Institute * Andrew Lumsdaine, Indiana University * Jaakko Jarvi, Texas A&M University * Sibylle Schupp, Chalmers University of Technology * Todd Veldhuizen, Indiana University * Jeremy Siek, Rice University Primarily, the email address lcsd05(a)cs.tamu.edu should be used for questions addressed to the organizers. PROGRAM COMMITTEE * Uwe Assmann, Technical University of Dresden * Matt Austern, Google Inc. * Herve Broennimann, Polytechnic University * Antonio Cisternino, University of Pisa * Jack Dongarra, University of Tennessee * Ulrich Eisenecker, University of Leipzig * Rob Fowler, HiPerSoft, Rice University * Calvin Lin, University of Texas at Austin * Anthony Simons, University of Sheffield * Alex Stepanov, Adobe Systems Inc. * Bjarne Stroustrup, Texas A&M and AT&T Labs * Don Syme, Microsoft Research * Frank Tip, IBM Research In addition, the organizers will serve as program committee members. WORKSHOP GOALS AND ACTIVITIES The workshop establishes a scientific forum for presenting original research in the design, implementation, and evaluation of software libraries. Other major activities include the identification of open questions specific to library research and the discussion of a strategic plan for establishing library research as a field. The outcome of the workshop is a combination of research contributions and specific next steps for improving the infrastructure for library research. Participants are expected to read the accepted submissions beforehand. The technical presentations, although based on the accepted papers, should not provide mere summaries of the papers. Instead, authors are encouraged to use their presentation slots (20 + 10 mins) to bring up topics for discussion. The technical presentations are mixed with scientific and organizational discussions. The discussions aim at furthering the topics of the presentations, thus their agenda will be publicly discussed among the participants and then posted on the website of the workshop. All participants are expected to come prepared with their tentative answers or thoughts. The full-day workshop starts with a keynote talk for the stimulation of discussion and concludes with a plenary discussion that decides the specific next steps for improving the infrastructure for library research. FOR MORE INFORMATION AND UPDATES please visit the workshop's Web site, http://lcsd05.cs.tamu.edu.

1 0

Re: [boost] [mpl] as_sequence< X< Y > > instantiates typedefs in X< Y >
by Andreas Huber 02 Aug '05

02 Aug '05

--- Brian Braatz <brianb(a)rmtg.com> wrote: > Suggestion: > > is there some way in your design you can get away with deriving > from the > incomplete type to "de-incomplete" it? I don't understand. You can't inherit from an incomplete type. Regards, -- Andreas Huber When replying by private email, please remove the words spam and trap from the address shown in the header.

1 0

Boost regression notification (2005-08-02)
by Douglas Gregor 02 Aug '05

02 Aug '05

Boost regression test failures ------------------------------ Report time: 2005-08-02T15:32:20Z This report lists all regression test failures on release platforms. Detailed report: http://engineering.meta-comm.com/boost-regression/CVS-RC_1_33_0/developer/i… 0 failure in 0 library:

4 3

[iostreams] problem with building library
by Alexey Bakhvalov 02 Aug '05

02 Aug '05

I am trying to build Boost RC1 and I have problem if I enable zlib and bzip2 support for IOStreams library. I am using Boost.Build system and I get the following error during the build process: unknown dependent target <@boost!libs!iostreams!build>libboost_bzip2.lib The build is executed from Boost root directory using .bat-file of the following contents: set NO_BZIP2=0 set NO_ZLIB=0 set ZLIB_SOURCE=.\external\zlib123 set ZLIB_INCLUDE=.\external\zlib123 set BZIP2_SOURCE=.\external\bzip2-1.0.3 set BZIP2_INCLUDE=.\external\bzip2-1.0.3 set TOOLS=vc-7_1 bjam install Am I doing something wrong or it's a problem of the build system? Alexey Bakhvalov

3 3

[tokenizer] offset_separator does not behave as docs state it does
by Bart 02 Aug '05

02 Aug '05

The docs for the offset_separator state the following regarding the breturnpartiallast construction parameter: "For example the string "122501" with offsets (2,2,4) ... With it set to false, it will parse to 12 25 and then will stop because there are only 2 characters left in the sequence instead of the 4 that should have been there." This leads me to believe, the string "1225011" (3 chars in last part) should also stop parsing after the first two tokens and ignore the third. It does not. Using the following example (compiled against current cvs)... int main(){ using namespace std; using namespace boost; string s = "1225199"; int offsets[] = {2,2,4}; offset_separator f(offsets, offsets+3, false, false); tokenizer<offset_separator> tok(s,f); for(tokenizer<offset_separator>::iterator beg=tok.begin(); beg!=tok.end();++beg){ cout << *beg << "\n"; } } Output is: 12 25 199 I think it should be just: 12 25 Thanks, Bart

1 0