December 2009 - Boost-users

Boost.Interfaces
by Jerry Jeremiah 08 Dec '09

08 Dec '09

Hello, I was looking at the Go language that Google just announced and I was thinking that these "interfaces" were cool. So I found these emails from the Boost users group from 2008: http://archives.free.net.ph/message/20080120.235150.027a4293.en.html http://archives.free.net.ph/message/20080201.165555.eb39994f.en.html It sounds like Jonathon intended to submit a proposal for his library in 2008 but I can't find anything about what happened after that. All I have is http://www.coderage.com/interfaces/ which was last updated 2005. I tried emailing him directly via the email address on that page but there was no answer. Does anyone know if there is a newer version than the 2005 zip file on that page? His Boost user list emails imply that there is one with changes in 2008 and that it was going to be submitted for review so if someone could point me in the right direction I would appreciate it. Jerry

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usage of bcp
by Geoff Hilton 08 Dec '09

08 Dec '09

Hello, I've been reconsidering the use of bcp to import boost code into a public-facing portion of our api for intrusive_ptr, I've read the documentation somewhat, and tried using the command as follows: C:\Program Files\boost\boost_1_41_0\>bcp intrusive_ptr ../../intrusive_ptr This seems to fail as it brings up the usage screen instead of producing anything useful, how can I get it to work correctly? even going into the boost subdirectory and pointing to a destination of /int_ptr gave the same result. Also, I read about a way to rename the namespaces/defines in boost to limit/prevent clashing with client code, how do I go about triggering this? Thanks very much, Geoff

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Newbie question
by Vadim Ryvchin 08 Dec '09

08 Dec '09

Hello, I have a problem with interruption of threads. I have one function that I want to run in two different threads with different parameters. When one of the function's instances finishes it stops the other instance. I can't change the function's code, but I can write wrapper to it. My problem is in stopping the other thread. Using timed_join I find which thread is finished, but I can't find a good solution for stopping the second one. How should I use interrupt method correctly or suggest me for correct thread stopping function. BTW, I can't just leave the other thread to run, it's very high CPU consumer. Thank you all.

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Re: [Boost-users] thread_group::interrupt_all is not reliable
by Stonewall Ballard 08 Dec '09

08 Dec '09

I think I found the cause of this problem. It seems that the caller of interrupt_all should be holding the mutex associated with the condition on which the threads are waiting. This gave me the clue to try that: <http://www.opengroup.org/onlinepubs/009695399/functions/pthread_cond_broadc…> > The pthread_cond_broadcast() or pthread_cond_signal() functions may be called by a thread whether or not it currently owns the mutex that threads calling pthread_cond_wait() or pthread_cond_timedwait() have associated with the condition variable during their waits; however, if predictable scheduling behavior is required, then that mutex shall be locked by the thread calling pthread_cond_broadcast() or pthread_cond_signal(). thread::interrupt() calls pthread_cond_broadcast in pthread/thread.cpp. Although "predictable scheduling" doesn't seem like it should include a failure to wake up, taking the mutex around the call to thread_pool::interrupt_all() appears to be 100% reliable. I can patch my app to do that, but I don't think there's a general solution. The documentation should include a note that thread::interrupt() isn't reliable unless the caller is holding the mutex associated with the condition variable on which the interrupted thread is waiting. Of course, this could be a bug in the OS X pthreads implementation as well. - Stoney > I've discovered that under circumstances apparently related to timing > and load, sending interrupt_all to a thread_group when all the threads > are waiting on a boost::condition_variable leaves one thread waiting > about 1/3 of the time. This is with boost 1_40_0 running on Mac OS X > 10.6.2, with 32-bit boost libraries. Boost uses the posix thread > system here. > I boiled my app down to some test code that runs as a command-line > app. It's a bit longer than I'd like, but this configuration seems to > be necessary to invoke the problem. The test uses a queue to pass > "tasks" from the main thread to worker threads, and another queue to > pass "results" back to the main thread. The problem is most apparent > when all the tasks are finished and the queue empties, so that all the > worker threads are waiting on the input queue when the main thread > sends interrupt_all. > > I've looked at the waiting thread in a debugger when this happens, and > found that it has been interrupted, but is still waiting on the > condition. It looks like it just got missed by the interrupt_all. This > is more likely to happen when there are a lot of worker threads (16, > or one per core in my testing). > > The test code is parked at <http://sb.org/ThreadTest.zip>, 20KB. It's > an XCode 3.2 project, but the five source files could be readily > compiled and run in any Unix environment. > > I don't see any errors in the code that could cause these failures. > There is a work-around, which is to interrupt the waiting thread > again. This required a modified version of thread_group so I could do > a timed_join_all on it. > > I welcome any suggestions about what could be wrong here, or ways to > simplify the test to make it more suitable for a bug report. > > - Stoney -- Stonewall Ballard stoney(a)sb.org http://stoney.sb.org/

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feature request: program_options: generate OS dependent options
by Hicham Mouline 08 Dec '09

08 Dec '09

Hello, Following the discussion in http://lists.boost.org/boost-users/2009/12/54327.php, let me then request that the feature be implemented in program_options. The 2 systems that I know a little about are POSIX(thanks Ovanes) and Windows: .POSIX: Typically, the command line would options with the '-' being the delimiter, like for the 'ls' program on a linux system: ls --help .... -a, --all do not ignore entries starting with . -A, --almost-all do not list implied . and .. --author with -l, print the author of each file -b, --escape print octal escapes for nongraphic characters --block-size=SIZE use SIZE-byte blocks --help print this .... .Windows dir /?: Typically, the '/' is the delimiter. ... /B Uses bare format (no heading information or summary). ... So in fact, I have 2 feature requests :-) : 1. Detect automatically the OS platform and the appropriate delimiter ( / or - or -- ) for win or POSIX 2. Detect the special option (help) that dislays the usage, which is /? on windows and --help on POSIX, and treat it symbolically in the user code calling program_options, ie not having to test for the "help" string as shown in the tutorial. I can create the trac tickets if preferred, Regards,

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boost serialisation file size comparison
by Avi Bahra 08 Dec '09

08 Dec '09

I have written some test for the different kind of serialization archives in my application. In the test below the only difference is the kind of archive used ( and use of ios::binary for the binary streams) ANode:: ...test_node_tree_persistence_text file_size: 4014 ANode:: ...test_node_tree_persistence_binary file_size: 5351 ANode:: ...test_node_tree_persistence_portable_binary file_size: 2878 What I don't understand is why should the binary archive serialization file size be larger than text ? -- Best regards, Ta, Avi

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program_options
by Hicham Mouline 08 Dec '09

08 Dec '09

For command-line options, I understand from what I read so far that the options should be like --option_name=value There is a system(I believe it is gnu) which has the long and short versions of options, like -h and --help Also, on winxxx systems, usually the command line options are indicated with a / like /? or /x /X .... Is it possible to tune program_options to choose the platform's default way of treating options? Regards,

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Review Wizard report for December 2009
by John Phillips 08 Dec '09

08 Dec '09

All, Please check the report below and let Ron and I know if there are any issues so we can correct them before putting it on the web site. Pay especial attention to the need for many qualified and interested Review Managers. John ============================================== Review Wizard Status Report for December 2009 ============================================== News ==== Polygon Library Accepted Boost 1.40 Released New Libraries: None Revised Libraries: Accumulators, Asio, Circular Buffer, Filesystem, Foreach, Function, Fusion, Hash, Interprocess, Intrusive, MPL, Program Options, Proto, Python, Serialization, Unordered, Xpressive Geometry Library Accepted Boost 1.41 Released New Libraries: Property Tree Revised Libraries: DateTime, Filesystem, Iostreams, Math, Multi-index Containers, Proto, Python, Regex, Spirit, System, Thread, Unordered, Utility, Wave, Xpressive MSM Library Review Underway Constrained Value Review - Review Result still Pending Older Issues ============ The Time Series Library, accepted in August 2007, has not yet been submitted to SVN. The Floating Point Utilities Library, has not yet been submitted to SVN. It is slated to be integrated with the Boost.Math library. The Switch Library, accepted provisionally in January 2008, has not yet been submitted for mini-review and full acceptance. The Phoenix Library, accepted provisionally in September 2008, has not yet been submitted for mini-review and full acceptance. For libraries that are still waiting to get into SVN, please get them ready and into the repository. The developers did some great work making the libraries, so don't miss the chance to share that work with others. General Announcements ===================== As always, we need experienced review managers. The review queue has been growing substantially but we have had few volunteers, so manage reviews if possible and if not please make sure to watch the review schedule and participate. Please take a look at the list of libraries in need of managers and check out their descriptions. In general review managers are active boost participants or library contributors. If you can serve as review manager for any of them, email Ron Garcia or John Phillips, "garcia at osl dot iu dot edu" and "phillips at mps dot ohio-state dot edu" respectively. We are also suffering from a lack of reviewers. While we all understand time pressures and the need to complete paying work, the strength of Boost is based on the detailed and informed reviews submitted by you. A recent effort is trying to secure at least five people who promise to submit reviews as a precondition to starting the review period. Consider volunteering for this and even taking the time to create the review as early as possible. No rule says you can only work on a review during the review period. A link to this report will be posted to www.boost.org. If you would like us to make any modifications or additions to this report before we do that, please email Ron or John. If you're a library author and plan on submitting a library for review in the next 3-6 months, send Ron or John a short description of your library and we'll add it to the Libraries Under Construction below. We know that there are many libraries that are near completion, but we have hard time keeping track all of them. Please keep us informed about your progress. The included review queue isn't a classic queue. It is more an unordered list of the libraries awaiting review. As such, any library in the queue can be reviewed once the developer is ready and a review manager works with the wizards and the developer to schedule a review. It is not FIFO. Review Queue ============ * Lexer * Shifted Pointer * Logging * Log * Join * Pimpl * Task * Endian * Conversion * Sorting * GIL.IO * AutoBuffer * String Convert * Move * Containers * Interval Containers * Type Traits Extensions * Interthreads * Bitfield * Lockfree -------------------- Lexer ----- :Author: Ben Hanson :Review Manager: Eric Neibler :Download: `Boost Vault <http://boost-consulting.com/vault/index.php?action=downloadfile&filename=bo…>`__ :Description: A programmable lexical analyser generator inspired by 'flex'. Like flex, it is programmed by the use of regular expressions and outputs a state machine as a number of DFAs utilising equivalence classes for compression. Shifted Pointer --------------- :Author: Phil Bouchard :Review Manager: Needed :Download: `Boost Vault <http://www.boost-consulting.com/vault/index.php?&direction=0&order=&directo…>`__ :Description: Smart pointers are in general optimized for a specific resource (memory usage, CPU cycles, user friendliness, ...) depending on what the user need to make the most of. The purpose of this smart pointer is mainly to allocate the reference counter (or owner) and the object itself at the same time so that dynamic memory management is simplified thus accelerated and cheaper on the memory map. Logging ------- :Author: John Torjo :Review Manager: Gennadiy Rozental :Download: http://torjo.com/log2/ :Description: Used properly, logging is a very powerful tool. Besides aiding debugging/testing, it can also show you how your application is used. The Boost Logging Library allows just for that, supporting a lot of scenarios, ranging from very simple (dumping all to one destination), to very complex (multiple logs, some enabled/some not, levels, etc). It features a very simple and flexible interface, efficient filtering of messages, thread-safety, formatters and destinations, easy manipulation of logs, finding the best logger/filter classes based on your application's needs, you can define your own macros and much more! Log --- :Author: Andrey Semashev :Review Manager: Needed :Download: `Boost Vault <http://tinyurl.com/cm9lum>`__ :Description: The library is aimed to help adding logging features to applications. It provides out-of-box support for many widely used capabilities, such as formatting and filtering based on attributes, sending logs to a syslog server or to Windows Event Log, or simply storing logs into files. It also provides basic support for the library initialization from a settings file. The library can also be used for a wider range of tasks and implement gathering and processing statistical information or notifying user about application events. Join ---- :Author: Yigong Liu :Review Manager: Needed :Download: http://channel.sourceforge.net/ :Description: Join is an asynchronous, message based C++ concurrency library based on join calculus. It is applicable both to multi-threaded applications and to the orchestration of asynchronous, event-based applications. It follows Comega's design and implementation and builds with Boost facilities. It provides a high level concurrency API with asynchronous methods, synchronous methods, and chords which are "join-patterns" defining the synchronization, asynchrony, and concurrency. Pimpl ----- :Author: Vladimir Batov :Review Manager: Needed :Download: | `Boost Vault <http://www.boost-consulting.com/vault/index.php?action=downloadfile&filenam…>`__ | http://www.ddj.com/cpp/205918714 (documentation) :Description: The Pimpl idiom is a simple yet robust technique to minimize coupling via the separation of interface and implementation and then implementation hiding. This library provides a convenient yet flexible and generic deployment technique for the Pimpl idiom. It's seemingly complete and broadly applicable, yet minimal, simple and pleasant to use. Task ----------- :Author: Oliver Kowalke :Review Manager: Needed :Download: `Boost Vault <http://www.boostpro.com/vault/index.php?action=downloadfile&filename=bo…>`__ :Description: Formerly called Thread Pool The library provides: - thread creation policies: determines the management of worker threads: - fixed set of threads in pool - create workerthreads on demand (depending on context) - let worker threads ime out after certain idle time - channel policies: manages access to queued tasks: - bounded channel with high and low watermark for queuing tasks - unbounded channel with unlimited number of queued tasks - rendezvous syncron hand-over between producer and consumer threads - queueing policy: determines how tasks will be removed from channel: - FIFO - LIFO - priority queue (attribute assigned to task) - smart insertions and extractions (for instance remove oldest task with certain attribute by newst one) - tasks can be chained and lazy submit of taks is also supported (thanks to Braddocks future library). - returns a task object from the submit function. The task it self can be interrupted if its is cooperative (means it has some interruption points in its code -> ``this_thread::interruption_point()`` ). Endian ------ :Author: Beman Dawes :Review Manager: Needed :Download: http://mysite.verizon.net/beman/endian-0.10.zip :Description: Conversion ---------- :Author: Vicente Botet :Review Manager: Needed :Download: `Boost Vault <http://www.boostpro.com/vault/index.php?action=downloadfile&filename=co…>`__ :Description: Generic explicit conversion between unrelated types. Boost.Conversion provides: * a generic ``convert_to`` function which can be specialized by the user to make explicit conversion between unrelated types. * a generic ``assign_to`` function which can be specialized by the user to make explicit assignation between unrelated types. * conversion between ``std::complex`` of explicitly convertible types. * conversion between ``std::pair`` of explicitly convertible types. * conversion between ``boost::optional`` of explicitly convertible types. * conversion between ``boost::rational`` of explicitly convertible types. * conversion between ``boost::interval`` of explicitly convertible types. * conversion between ``boost::chrono::time_point`` and ``boost::ptime``. * conversion between ``boost::chrono::duration`` and ``boost::time_duration``. Sorting ------- :Author: Steven Ross :Review Manager: Needed :Download: `Boost Vault <http://www.boostpro.com/vault/index.php?action=downloadfile&filename=al…>`__ :Description: A grouping of 3 templated hybrid radix/comparison-based sorting algorithms that provide superior worst-case and average-case performance to std::sort: integer_sort, which sorts fixed-size data types that support a rightshift (default of >>) and a comparison (default of <) operator. float_sort, which sorts standard floating-point numbers by safely casting them to integers. string_sort, which sorts variable-length data types, and is optimized for 8-bit character strings. All 3 algorithms have O(n(k/s + s)) runtime where k is the number of bits in the data type and s is a constant, and limited memory overhead (in the kB for realistic inputs). In testing, integer_sort varies from 35% faster to 8X as fast as std::sort, depending on processor, compiler optimizations, and data distribution. float_sort is roughly 7X as fast as std::sort on x86 processors. string_sort is roughly 2X as fast as std::sort. GIL.IO ------ :Author: Christian Henning :Review Manager: Needed :Download: `GIL Google Code Vault <http://gil-contributions.googlecode.com/files/rc2.zip>`__ :Description: I/O extension for boost::gil which allows reading and writing of/in various image formats ( tiff, jpeg, png, etc ). This review will also include the Toolbox extension which adds some common functionality to gil, such as new color spaces, algorithms, etc. AutoBuffer ---------- :Author: Thorsten Ottosen :Review Manager: Needed :Download: `Here <http://www.cs.aau.dk/~nesotto/boost/auto_buffer.zip>`__ :Description: Boost.AutoBuffer provides a container for efficient dynamic, local buffers. Furthermore, the container may be used as an alternative to std::vector, offering greater flexibility and sometimes better performance. String Convert -------------- :Author: Vladimir Batov :Review Manager: Needed :Download: `Boost Vault <http://www.boostpro.com/vault/index.php?action=downloadfile&filename=bo…>`__ :Description: The library takes the approach of boost::lexical_cast in the area of string-to-type and type-to-string conversions, builds on the past boost::lexical_cast experience and advances that conversion functionality further to additionally provide: * throwing and non-throwing conversion-failure behavior; * support for the default value to be returned when conversion fails; * two types of the conversion-failure check -- basic and better/safe; * formatting support based on the standard I/O Streams and the standard (or user-defined) I/O Stream-based manipulators (like std::hex, std::scientific, etc.); * locale support; * support for boost::range-compliant char and wchar_t-based string containers; * no DefaultConstructibility requirement for the Target type; * consistent framework to uniformly incorporate any type-to-type conversions. It is an essential tool with applications making extensive use of configuration files or having to process/prepare considerable amounts of data in, say, XML, etc. Move ---------------- :Author: Ion Gaztanaga :Review Manager: Needed :Download: http://svn.boost.org/svn/boost/sandbox/move/ and online documentation at http://svn.boost.org/svn/boost/sandbox/move/libs/move/doc/html/index.html :Description: In C++0x, move semantics are implemented with the introduction of rvalue references. They allow us to implement move() without verbosity or runtime overhead. Boost.Move is a library that offers tools to implement those move semantics not only in compilers with rvalue references but also in compilers conforming to C++03. Containers ------------------ :Author: Ion Gaztanaga :Review Manager: Needed :Download: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost.… and online documentation at http://svn.boost.org/svn/boost/sandbox/move/libs/container/doc/html/index.h… :Description: Boost.Container library implements several well-known containers, including STL containers. The aim of the library is to offers advanced features not present in standard containers or to offer the latest standard draft features for compilers that comply with C++03. Interval Containers Library ------------------------- :Author: Joachim Faulhaber :Review Manager: Needed :Description: The Interval Template Library (Itl) provides intervals and two kinds of interval containers: Interval_sets and interval_maps. Interval_sets and maps can be used just as sets or maps of elements. Yet they are much more space and time efficient when the elements occur in contiguous chunks: intervals. This is obviously the case in many problem domains, particularly in fields that deal with problems related to date and time. Interval containers allow for intersection with interval_sets to work with segmentation. For instance you might want to intersect an interval container with a grid of months and then iterate over those months. Finally interval_maps provide aggregation on associated values, if added intervals overlap with intervals that are stored in the interval_map. This feature is called aggregate on overlap. It is shown by example: :: typedef set<string> guests; interval_map<time, guests> party; guests mary; mary.insert("Mary"); guests harry; harry.insert("Harry"); party += make_pair(interval<time>::rightopen(20:00, 22:00),mary); party += make_pair(interval<time>::rightopen_(21:00, 23:00),harry); // party now contains [20:00, 21:00)->{"Mary"} [21:00, 22:00)->{"Harry","Mary"} //guest sets aggregated on overlap [22:00, 23:00)->{"Harry"} As can be seen from the example an interval_map has both a decompositional behavior (on the time dimension) as well as a accumulative one (on the associated values). Type Traits Extensions -------------------------- :Author: Frédéric Bron :Review Manager: Needed :Download: https://svn.boost.org/trac/boost/browser/sandbox/type_traits :Description: The purpose of the addition is to add type traits to detect if types T and U are comparable in the sens of <, <=, >, >=, == or != operators, i.e. if t<u has a sens when t is of type T and u of type U (same for <=, >, >=, ==, !=). The following traits are added: is_equal_to_comparable<T,U> is_greater_comparable<T,U> is_greater_equal_comparable<T,U> is_less_comparable<T,U> is_less_equal_comparable<T,U> is_not_equal_to_comparable<T,U> The names are based on the corresponding names of the standard template library (<functional> header, section 20.3.3 of the standard). The code has the following properties: * returns true if t<u is meaningful and returns a value convertible to bool * returns false if t<u is meaningless. * fails with compile time error if t<u is meaningful and returns void (a possibility to avoid compile time error would be to return true with an operator, trick but this has little sens as returning false would be better) InterThreads ------------------- :Author: Vicente J. Botet Escriba :Review Manager: Needed :Download: `Boost Vault <http://www.boostpro.com/vault/index.php?action=downloadfile&filename=in…>`__ :Description: Boost.InterThreads extends Boost.Threads adding some features: * thread decorator: thread_decorator allows to define setup/cleanup functions which will be called only once by thread: setup before the thread function and cleanup at thread exit. * thread specific shared pointer: this is an extension of the thread_specific_ptr providing access to this thread specific context from other threads. As it is shared the stored pointer is a shared_ptr instead of a raw one. * thread keep alive mechanism: this mechanism allows to detect threads that do not prove that they are alive by calling to the keep_alive_point regularly. When a thread is declared dead a user provided function is called, which by default will abort the program. * thread tuple: defines a thread groupe where the number of threads is know statically and the threads are created at construction time. * set_once: a synchonizer that allows to set a variable only once, notifying to the variable value to whatever is waiting for that. * thread_tuple_once: an extension of the boost::thread_tuple which allows to join the thread finishing the first, using for that the set_once synchronizer. * thread_group_once: an extension of the boost::thread_group which allows to join the thread finishing the first, using for that the set_once synchronizer. (thread_decorator and thread_specific_shared_ptr) are based on the original implementation of threadalert written by Roland Schwarz. Boost.InterThreads extends Boost.Threads adding thread setup/cleanup decorator, thread specific shared pointer, thread keep alive mechanism and thread tuples. Bitfield --------------- :Author: Vicente J. Botet Escriba :Review Manager: Needed :Download: https://svn.boost.org/svn/boost/sandbox/bitfield with documentation available at https://svn.boost.org/svn/boost/sandbox/bitfield/libs/bitfield/doc/index.ht… :Description: Portable bitfields traits. Boost.Bitfield consists of: * a generic bitfield traits class providing generic getter and setter methods. * a BOOST_BITFIELD_DCL macro making easier the definition of the bitfield traits and the bitfield getter and setter functions. Lockfree ------------------ :Author: Tim Blechmann :Review Manager: Needed :Description: boost.lockfree provides implementations of lock-free data structures. lock-free data structures can be accessed by multiple threads without the necessity of blocking synchronization primitives such as guards. lock-free data structures can be used in real-time systems, where blocking algorithms may lead to high worst-case execution times, to avoid priority inversion, or to increase the scalability for multi-processor machines. boost.lockfree provides: * boost::lockfree::fifo, a lock-free fifo queue * boost::lockfree::stack, a lock-free stack the code is available from the boost vault: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost_… and from my personal git repository: git://tim.klingt.org/boost_lockfree.git http://tim.klingt.org/git?p=boost_lockfree.git the documentation is available at: http://tim.klingt.org/boost_lockfree/ Libraries under development =========================== Please let us know of any libraries you are currently developing that you intend to submit for review. See https://svn.boost.org/trac/boost/wiki/LibrariesUnderConstruction for a current listing of libraries under development.

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[Date_Time] reliability and high resolution when getting system time
by John Beauport 08 Dec '09

08 Dec '09

For middleware purposes we have been looking at using Boost as our date/time library. It seems to cover most of our requirements. Now it has been brought to our attention that one of our requirements would be to be able to get the system time at a high resolution. Although using solely the high performance counter is a solution to this, it has its flaws. We have read an article that gives a solution that overcomes some of the problems inherent to using the performance counters, and combines/synchronizes these counters with system time to achieve better resolution. The following is a link to the article that tackles the subject (on Windows): http://msdn.microsoft.com/en-us/magazine/cc163996.aspx Has solving this type of issue been considered in Date_Time? Is it worth looking into? With these questions, I am trying to avoid venturing in something that may have already been experimented with and concluded on. I have noticed in the boost::date_time code that there is the microsec_clock::local_time() call that should provide high resolution time, but in looking at the code I do not quite understand how that is achieved with accuracy. I am trying to understand the file_time_to_microseconds() function in filetime_functions.hpp, and I have difficulty to understand how counting microseconds difference from Jan-01-1601 to Jan-01-1970 comes into play in counting the microseconds from epoch to "now". Can someone clarify this? I thank you in advance for taking the time to answer my few questions. Kind Regards, John

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Waiting for multiple events
by Vadim Guchenko 07 Dec '09

07 Dec '09

Hello, All! I want to do something like this: Wrapper wrapper(final_handler); w_handler1 = wrapper.wrap(handler1); ... w_handlerN = wrapper.wrap(handlerN); where the final_handler() must be invoked as soon as all the wrapped handlers handler1() ... handlerN() are invoked through w_handler1() ... w_handlerN() in any order. Is there any existing Boost tool for that? -- Best regards, Vadim Guchenko [yhw at relost dot net].

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