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[thread] C++11 once_flag enabled when constexpr is not available
by Andrey Semashev 05 Mar '13

05 Mar '13

Hi, Vicente! I see you applied my patch for call_once but you seem to forgot to disable the C++11 call_once interface when the compiler does not support constexpr. Was that intentional or you just missed it? Anyway, please find the patch attached.

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[locale] Composing asymmetric locale for character encoding conversion
by Andrey Semashev 05 Mar '13

05 Mar '13

Hi, Suppose I have a logging application that writes log records in wide (wchar_t, UTF-16) and narrow (char, UTF-8) encodings and I want these logs to be stored in a UTF-16LE encoded file. For simplicity, let's assume that I write log files with std::wofstream. Now, the standard says that the file stream buffer is supposed to convert wide characters to byte sequences using the locale imbued into the buffer. However, it seems that the locale should be the same as the one imbued into the stream (basic_ostream::imbue makes sure of that). What this leads to is that in order to achieve my goal the locale should be able to convert narrow characters of UTF-8 to wide characters of UTF-16 and wide characters of UTF-16 to narrow characters representing byte sequence of UTF16LE. Is it possible to make such an asymmetric locale with Boost.Locale? Or maybe there is another way of doing this? An additional question. Is it possible to to achieve my goal with std::ofstream (as opposed to std::wofstream)? I have a very strong suspicion that the answer is no because the narrow characters will pass on unconverted to the file instead of being translated from UTF-8 to UTF-16LE, but maybe I'm missing something. Thank you.

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[coroutine] documentation comment
by Brian Wood 05 Mar '13

05 Mar '13

I wrote about this last month on Boost users but there wasn't a reply. I have a comment about a sentence on this page: http://www.boost.org/doc/libs/1_53_0/libs/coroutine/doc/html/coroutine/intr… "The principal difference between coroutines and routines is that a coroutine enables explicit suspend and resume their progress via additional operations by preserving local state ..." I'm wondering if it would be helpful to change that to this: The principal difference between coroutines and routines is that coroutines enable explicit suspend and resume of their progress via additional operations by preserving local state ... Shalom Brian Wood Ebenezer Enterprises http://webEbenezer.net (651) 251-9384

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[tweener] Preliminary Submission
by Julien Jorge 05 Mar '13

05 Mar '13

Hello, I would like to propose the Boost.Tweener library for preliminary submission. The purpose of the Boost.Tweener library is to provide solutions to interpolate the intermediate values between two given values during a time interval. Various easing functions can be applied to control the computation of the intermediate values. I felt the need of such a library while developing games but I have also seen this need in various animation softwares. The library provides the following functionalities: - Interpolation is done on the value of a given variable or using an user-provided callback function, - The interpolated values are computed using a predefined easing function or any user-provided function respecting the contract, - Several tweeners can easily be executed simultaneously or in a row, - The type of the interpolated values are user defined. Please follow this link to download a Zip of the library: http://sourceforge.net/projects/libclaw/files/boost/boost-tweener-rc1.tar.g… Can you check that the library works as expected or tell me what should be fixed before submitting for review? There are various example programs in the archive. Regards, Julien Jorge

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[thread] boost::thread and thread safety annotations
by Wladimir 04 Mar '13

04 Mar '13

Hello, The Clang C++ compiler project is currently working on a thread safety analyzer. By making use of so-called thread safety annotations within the source code, several problems with synchronization primitives can be found statically. For example: usage of a data structure without acquiring its guarding lock. See here for an overview of the available attributes: http://clang.llvm.org/docs/LanguageExtensions.html#threadsafety It is customary to use these attributes by defining macros, for compatibility: http://www.mail-archive.com/linuxkernelnewbies@googlegroups.com/msg01455.ht… At one time, it was also supposed to end up in G++, but this was abandoned in favor of clang (see http://gcc.gnu.org/wiki/ThreadSafetyAnnotation) But at least the annotations are fairly standardized. I think it would be useful to add these annotations to boost::thread, so that projects using that library can make use of the static checking. As I understand it, is only a matter of marking data structures that serve as lock/scoped_lock (such as boost::mutex, boost::recursive_mutex, ...), and methods that act upon the lock with the appropriate attributes. Any interest in this? Regards, Wladimir

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[thread] barrier::wait() not marked as interruption_point
by Oliver Kowalke 04 Mar '13

04 Mar '13

In the documentation (1.53 beta) barrier::wait() is not marked as interruption-point nor that it will throw thread_interrupted if thread blocked inside barrier::wait() if it gets interrupted. Because barrier::wait() calls condition_variable::wait() and condition_variable::wait() is a interruption-point barrier::wait() should it be too - or do I miss something? Oliver

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Re: [boost] [persistent] Library preview: Persistent
by Stefan Strasser 04 Mar '13

04 Mar '13

Am 04.03.2013 16:52, schrieb Jarrad Waterloo: > So if your library is in need, which it is, than release it, preferably > to boost under the boost license. You can always improve, add on latter. > You may solicit architecture and requirements from the list to increase > its usefulness and minimize rewrites. If you can't provide enough > manpower to complete it or even if you can, than solicit help. If four > people throughout the world can get it done in half the time of one > person than WOO HOO! There are many who would like to contribute from > the beginning, which also can't hurt acceptance. The important thing is > to have a vision, preferably shared, and to release something usable, > useful and working, as quickly as possible before interest dries up and > in a timely manner. > > Thanks for your remarks! Specifically for Persistent: > Have you considered an MVCC [option] where there are no updates from a > users perspective but are rather inserts; This sacrifices hard drive > space for a lock free/low lock database. yes, the entire storage backend is based on MVCC [1]. there currently is no lock-based option. objects are MVCC in memory for concurrency (see section "concurrent transactions" [2]), and on disk to achieve atomic updates. when an update is safely synced to disk the old object versions are discarded. I haven't written much about the backend in the documentation for two reasons: the interface is most important, and I actually don't think it would get used much in the long term. as much as I try to make it safe and efficient, a backend using an industrially proven storage engine like BerkeleyDB or SQLite would almost always be preferred, if the stored data has any value. I've written more about this in a previous reply to Klaim-Joël Lamotte in this thread. Would you like to share anything on the architecture of the interface? > Since you in some ways may be competing against relational databases by > making a object oriented database, maybe equivalent administrative > functionality are in order such as import and export into some textual > representations. > On a related note, ways to access system information such external > id/OIDS, timestamps, version numbers via an API for tooling and maybe > querying purposes > ?File format specifications? this and much more is certainly needed for database applications. but since we don't have the resources to implement an industrial-strength storage engine, my approach was to provide one "black-box" implementation for applications that would have used (boost.)serialization or other files otherwise, and provide resource managers using external databases later on. > > Concerning my interest, why haven't you given this to me two years ago, > how much longer must I wait. [Ha Ha Ha] *pointing to the copyright notice* :p Regards, Stefan [1] http://en.wikipedia.org/wiki/Multiversion_concurrency_control [2] https://svn.boost.org/svn/boost/sandbox/persistent/libs/persistent/doc/html…

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Is there interest in a collection of call stack utilities?
by Aurelian Melinte 04 Mar '13

04 Mar '13

Hello, I have a collection of debugging/diagnostic utilities to inspect the run-time call stack and to resolve symbol information. The tools are currently C++11 code and support GNU-Linux and Windows. An overview is available at https://freeshell.de//~amelinte/call_stack_usage.html Is there interest for potential inclusion in boost? Thanks, Aurelian

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[persistent] Library preview: Persistent
by Stefan Strasser 04 Mar '13

04 Mar '13

Hi everyone, I'm thinking about finishing a library that was proposed a couple of years ago. It was pretty far along, and there is documentation available in the sandbox (somewhat outdated): https://svn.boost.org/svn/boost/sandbox/persistent/libs/persistent/doc/html… It is a library with the goal of storing C++ objects on disk, with an interface that is as close as possible to accessing regular C++ objects in memory. A very simple example could look like this: shared_loc<person> p=...; { transaction tx; p->name="..."; p->address="..."; tx.commit(); } It is based on Boost.Serialization, but automatically maintains a consistent state on disk (ACID transactions), which can be updated incrementally. Part of its code was moved to a library named Transact to work alongside other transactional resources (like memory) and is available in the sandbox: https://svn.boost.org/svn/boost/sandbox/transaction/boost/transact/ I'd like to know whether the boost community is still interested in such a library, and I suppose there are quite a few new people here so your comments are welcome as well. Thank You!

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[thread] why is 'thread_group' in 'boost/thread/detail'?
by pavel 03 Mar '13

03 Mar '13

as of 1.53 the docs say the 'thread_group' class is included by this instruction: #include <boost/thread/thread_group.hpp> http://www.boost.org/doc/libs/1_53_0/doc/html/thread/thread_management.html… whereas the actual file is not in the 'boost/thread', but accidentally is in 'boost/thread/detail' is that intentional? -- Pavel P.S. if you notice a grammar mistake or weird phrasing in my message please point it out

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