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Re: [boost] [date_time] Time zone improvements
by Rutger ter Borg 07 Feb '09

07 Feb '09

Jeff Garland wrote: > Very cool :-) One question -- is there a portable solution where a user > could deploy a files onto a Windows system or is it a Unix only solution? Portable, big endian binary files. The variant I'm proposing is also based on the POSIX standard http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html: "TZ This variable shall represent timezone information. The contents of the environment variable named TZ shall be used by the [snip] functions, and by various utilities, to override the default timezone. The value of TZ has one of the two forms (spaces inserted for clarity): :characters or: std offset dst offset, rule " The second variant is what's currently in Boost.Date_Time as Posix Time Zone, having a direct specification of the time zone. I'll be talking about the first variant, containing :characters. Although this is implementaiton specific, most POSIX-compatible systems have implemented the Zoneinfo database for this variant, e.g., Linux-based systems, many BSDs, Mac OS X, etc. The :characters point to any other zoneinfo-compatible binary file, either with an absolute or relative path. A natural step for changing Boost.Date_Time would be to make changes such that the Posix Time Zone supports both formats. I.e., variant 1) posix_time_zone( ":/etc/localtime" ); or posix_time_zone( ":/usr/share/zoneinfo/Europe/Amsterdam" ); variant 2) posix_time_zone( "EST-5EDT,M4.1.0,M10.5.0" ); I think both should work as it is from the same standard, and seems to be a natural and consistent starting point to look at changing the interface. Do you agree? > Actually, I believe the abstract timezone is able to support this, but > there > isn't a concrete implementation. It would be great to have the concrete > implementation to prove out the abstraction (obviously from the text below > you think there needs to be changes). As far as I can tell, the abstract time zone class currently is not able to represent variant 1): the abstract zone class is geared towards a single-lined definition of a time zone, whereas variant 1) may be regarded as a series of definitions, i.e., a map of < transition_time_point_in_utc, { gmt_offset, abbreviation, is_dst, ... } > looking up utc_to_local is a matter of doing a lower_bound search on the transition time points. The right-hand side of the map above is widely implemented with a struct called ttinfo. A proposal from my side would be to change the abstract time zone class in such way that it is able to represent both variants. The easiest approach here is probably to introduce the ttinfo structure, and make the current library working with that. variant 1): has a map of transition points, returns a (pointer to a) ttinfo structure. May hold more than 2 different ttinfo structures. variant 2): always has 2 ttinfo structures (std/dst). Uses dst-calculations/functions to lookup the transitions point, returns the right (pointer to a) ttinfo structure. What do you think? Cheers, Rutger

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[filesystem] relative path from arbitrary file system location?
by Kenny Riddile 07 Feb '09

07 Feb '09

Is there any existing functionality for getting a relative path from a full path, where the desired relative path is relative to an arbitrary directory path? If not, I'm assuming I would just have to walk up both full paths until I find their intersection...etc

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[who's using boost] matlap!
by Thorsten Ottosen 07 Feb '09

07 Feb '09

Hi follow boosters, I'm just installing matlap 2008, and looked in the bin/win32 directory. It contains nothing less than boost_date_time-vc80-mt-1_34_1.dll boost_filesystem-vc80-mt-1_34_1.dll boost_graph-vc80-mt-1_34_1.dll boost_iostreams-vc80-mt-1_34_1.dll boost_prg_exec_monitor-vc80-mt-1_34_1.dll boost_program_options-vc80-mt-1_34_1.dll boost_regex-vc80-mt-1_34_1.dll boost_serialization-vc80-mt-1_34_1.dll boost_signals-vc80-mt-1_34_1.dll boost_unit_test_framework-vc80-mt-1_34_1.dll boost_wave-vc80-mt-1_34_1.dll boost_wserialization-vc80-mt-1_34_1.dll :-) best regards Thorsten

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[New Feature Suggestion] Fast RTTI Implementation
by 류인환 07 Feb '09

07 Feb '09

Hello there. Let me introduce the fast rtti system. Many other library and system(ex. game engines) has there own rtti system. But normally their rtti system consume Big O(n) for dynamic casting another type. So, I implemented fast rtti Big O(1) time consuming rtti system. I used bit signature for class inhertance hierarchy expression. Thanks for reviewing my mail and source code

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[filesystem] : basic_path : Feature request
by Rob 06 Feb '09

06 Feb '09

Whilst using filesystem::path (v1.37) , I found I wanted the following functionality: Typedefs added for reference and const_reference and a push_back function, as follows typedef string_type& reference; typedef const string_type& const_reference; inline void push_back(const_reference path) { *this /= path; } This would allow use of std::back_inserter with stl algorithms such as Boost::filesystem::path src("dir1/./dir2"); Boost::filesystem::path target; Std::remove_copy(src.begin(), src.end(), std::back_inserter(target), "."); I would also like to see pop_back() but this may not be as simple to implement, I'll have to check the code Rob PS - My first post so I hope I'm on the right list, right message format, etc.

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Using Boost::Thread in DLL fails on LoadLibrary
by Michael Mzik 06 Feb '09

06 Feb '09

Hi there, I am rather new to Boost and this is my first trouble (win32 debug): I am using Boost::Thread inside a DLL which is loaded by my main program via LoadLibrary(..), but doing so leads to a "Debug Assertion" in "dllinit.cpp" (only in debug configuration!). my DLL links with: #pragma comment( lib, "libboost_thread-vc80-mt-gdp-1_37" ) #pragma comment( lib, "libboost_date_time-vc80-mt-gdp-1_37" ) #pragma comment( lib, "stlportstld.5.0" ) with preprocessor defines: _STLP_DEBUG BOOST_ALL_DYN_LINK BOOST_THREAD_USE_DLL BOOST_LIB_DIAGNOSTIC I am using STLport 5.0.1 and I have boost compiled successfully against STLport (at least I hope so..), I am not using pthreads. No release/debug DLL mixups, all DLLs are available (I checked with the dependency walker). The only thing that bugs me is that there is no "libboost_thread-vc80-mt-gdp-1_37.DLL" generated during boost-build.. but honestly I havent the smallest clue whats going wrong.. Hopefully anyone of you can help me out.. thank a lot in advance and greetings, Michael

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[pool] an O(1) implementation of object_pool::destroy()
by Ben Muzal 06 Feb '09

06 Feb '09

I was looking at object_pool and noticed that there is a way to make object_pool::destroy() an O(1) operation instead of an O(n) operation. If I understand the problem correctly, object_pool::destroy() is O(n) because it keep the free list sorted. It keeps the free list sorted so that object_pool::~object_pool() runs in O(n) time instead of in O(n^2) time. However, I believe there is an implementation of object_pool::~object_pool() that will run in O(n) time without requiring a sorted free list. My suggestion is that ~object_pool() could use a mark-sweep strategy: It would first step through the free list and mark each free chunk as such. It would then go back and examine each chunk in the pool and call the destructor on the ones not marked as free. The each chunk's 'next' pointer could be used to store the marked-as-free flag so that no extra memory is needed. This may be related to Ticket #290. A similar mark-sweep method could be used for pool::release_memory(). The free list would have to be reconstructed afterworlds but that is also easy. Just step back through all of the chunks and connect the ones that are marked as free. While I am on the subject of the pool library, I would also like to see a pool constructor that allows the user to set the initial size of the pool and whether or not the pool was allowed to grow. This would be very useful for the memory limited, real time environments in which memory pools are popular. Any thoughts on these suggestions? If asked, I could help work on an implementation. --Ben

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[threads] API Design Question
by Alexander Bernauer 06 Feb '09

06 Feb '09

Hello Why is it, that the wait and timed_wait functions of the condition_variable class do not encapsulate the problem of spurious wakeups? I wonder whether there are good reasons. I have seen libraries which do so. Do they miss a corner case? For illustration here is a sketch of a wrapper class ---8<--- class save_condition_variable { public: save_condition_variable() : waiting(0), wakeup(0) { } void notify_one() { if (wakeup < waiting) { ++wakeup; } cond.notify_one(); } void notify_all() { wakeup = waiting; cond.notify_all(); } void wait(unique_lock<mutex>& lock) { ++waiting; do { cond.wait(lock) } while (wakeup==0); --waiting; --wakeup; } bool timed_wait(unique_lock<mutex>& lock, system_time const& abs_time) { ++waiting; bool res = true; while(wakeup==0 and res) { res = cond.timed_wait(lock, abs_time); } --waiting; if (res) --wakeup; return res; } private: condition_variable cond; int waiting; int wakeup; }; --->8--- Having the spurious wakeup problem handled by the library is a significant increase of comfort for both developers and maintainers. regards Alex

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support for gcc hidden visibility in shared libraries
by Stjepan Rajko 06 Feb '09

06 Feb '09

Hello, Many (almost all?) linked boost libraries don't work as shared libraries when compiled with the -fvisibility=hidden switch on gcc version>=4. I am wondering whether there is interest in making them work under these circumstances, as it might not be too hard to do, and there seems to be some benefit to it. To my limited understanding, making a symbol visible in a shared library using, say, __attribute__ ((visibility("default"))) on gcc, is analogous to using __declspec(dllexport) on windows. Many boost libraries already use macros that apply __declspec(dllexport) on windows - so these macros could set to expand to __attribute__ ((visibility("default"))) on gcc. Even better, a boost-wide macro could be added to the config headers. More information on this can be found here: http://gcc.gnu.org/wiki/Visibility Just to note, I have very limited understanding of compiling/linking and I might not have a full grasp of everything involved here. Also, my only reason for thinking that -fvisibility=hidden should be supported is that for a long time now, I haven't been able to use boost shared libraries on my os x platform, and only now I realized that the reason for this is that I had stuck -fvisibility=hidden in my user-config.jam a long time ago to suppress some warnings. Nonetheless, it seems like there are benefits to supporting it that go beyond preventing people like me from accidentally shooting themselves in the foot. Kind regards, Stjepan

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Boost Lambda Expressions Serialization
by Emad Soroush 06 Feb '09

06 Feb '09

Hello there, I am using boost lambda library to show some type of expressions. I am trying to send the lambda expression remotely. Is there anyway to serialized the boost lambda expression? I am aware of the Boost:Serialization library, but it doesn't seem be able to serialize expressions Thanks Emad

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