February 2009 - Boost - lists.preview.boost.org

[thread] Why is thread_interrupted not derived from thread_exception or std::exception?
by Boris Schaeling 07 Feb '09

07 Feb '09

Why is thread_interrupted not derived from thread_exception or std::exception? It might easily slip through a try/catch-block, and if I hadn't looked up the header file now it might have slipped through mine. Boris

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[thread_pool|range_ex|bind] Extrange behaviour with fibonacci example and parallel_sort
by vicente.botet 07 Feb '09

07 Feb '09

Hi, I have tried to do a parallel_sort using the Boost.ThreadPool library and I get some realy extrange. I have copied the fibonacci example and adapted it to do a parallel sort. See attached file. When I set the defines FIBO this works some times, don't finish others and crash the others. I have added some traces (define COUT) and I get better results but not always correct. I suspected that the threads in the thread pool needs to be stoped. I have added a pool shutdown but nothing changes. Oliver, could you take a look? When I define X_SORT the compilation even do not finish. What is wrong on my definition of parallel_sort? Am I using boost:bind incorrectly? Is there some issue with binding function templates? Can some one help me? Thanks in advance, Vicente P.S. I'm using Boost 1.37 + The file compiles only with the lates version of the Boost.Range library http://www.boostpro.com/vault/index.php?action=downloadfile&filename=range_… and the Boost.ThreadPool version 17 http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost-… $ gcc --version gcc (GCC) 3.4.4 (cygming special, gdc 0.12, using dmd 0.125) Copyright (C) 2004 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Debug session $ gdb x_sort2 GNU gdb 6.8.0.20080328-cvs (cygwin-special) Copyright (C) 2008 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "i686-pc-cygwin"... (gdb) help List of classes of commands: aliases -- Aliases of other commands breakpoints -- Making program stop at certain points data -- Examining data files -- Specifying and examining files internals -- Maintenance commands obscure -- Obscure features running -- Running the program stack -- Examining the stack status -- Status inquiries support -- Support facilities tracepoints -- Tracing of program execution without stopping the program user-defined -- User-defined commands Type "help" followed by a class name for a list of commands in that class. Type "help all" for the list of all commands. Type "help" followed by command name for full documentation. Type "apropos word" to search for commands related to "word". Command name abbreviations are allowed if unambiguous. (gdb) run Starting program: /home/Vicente/SVN/bin.v2/vbe_interthreads/libs/interthreads/te st/x_sort2.test/gcc-3.4.4/debug/link-static/threading-multi/x_sort2.exe [New thread 3056.0x128] [New thread 3056.0x68c] std::sort: reverse 0..100000 0.05 s [New thread 3056.0xfe4] [New thread 3056.0x1c8] 55 Program exited normally. (gdb) run Starting program: /home/Vicente/SVN/bin.v2/vbe_interthreads/libs/interthreads/te st/x_sort2.test/gcc-3.4.4/debug/link-static/threading-multi/x_sort2.exe [New thread 4028.0xd48] [New thread 4028.0xef4] std::sort: reverse 0..100000 0.03 s [New thread 4028.0x9ec] [New thread 4028.0x5bc] [New thread 4028.0x3bc] [Switching to thread 4028.0x3bc] Quit (gdb) run The program being debugged has been started already. Start it from the beginning? (y or n) y Starting program: /home/Vicente/SVN/bin.v2/vbe_interthreads/libs/interthreads/te st/x_sort2.test/gcc-3.4.4/debug/link-static/threading-multi/x_sort2.exe [New thread 2220.0x4dc] [New thread 2220.0xe58] std::sort: reverse 0..100000 0.05 s [New thread 2220.0x9b0] [New thread 2220.0x778] [New thread 2220.0x264] Program received signal SIGINT, Interrupt. [Switching to thread 2220.0x264] 0x7c87635d in KERNEL32!GetConsoleCharType (Quit (gdb) run The program being debugged has been started already. Start it from the beginning? (y or n) y Starting program: /home/Vicente/SVN/bin.v2/vbe_interthreads/libs/interthreads/te st/x_sort2.test/gcc-3.4.4/debug/link-static/threading-multi/x_sort2.exe [New thread 3964.0xf40] [New thread 3964.0xedc] std::sort: reverse 0..100000 0.05 s [New thread 3964.0x320] [New thread 3964.0xe44] [New thread 3964.0x544] [Switching to thread 3964.0x544] Quit (gdb) q The program is running. Exit anyway? (y or n) y Vicente@viboes1 ~/SVN/bin.v2/vbe_interthreads/libs/interthreads/test/x_sort2.tes t/gcc-3.4.4/debug/link-static/threading-multi $ gdb x_sort2 GNU gdb 6.8.0.20080328-cvs (cygwin-special) Copyright (C) 2008 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "i686-pc-cygwin"... (gdb) run Starting program: /home/Vicente/SVN/bin.v2/vbe_interthreads/libs/interthreads/te st/x_sort2.test/gcc-3.4.4/debug/link-static/threading-multi/x_sort2.exe [New thread 1076.0x31c] [New thread 1076.0x9b8] std::sort: reverse 0..100000 0.05 s [New thread 1076.0xaec] [New thread 1076.0xdc0] 19239 [unknown (0xDC0)] x_sort2 1076 _cygtls::handle_exceptions: Exception: ST ATUS_ACCESS_VIOLATION 59227 [unknown (0xDC0)] x_sort2 1076 open_stackdumpfile: Dumping stack trace t o x_sort2.exe.stackdump Program received signal SIGSEGV, Segmentation fault. [Switching to thread 1076.0xdc0] 0x610b6132 in pthread_cond::~pthread_cond () from /usr/bin/cygwin1.dll (gdb) run The program being debugged has been started already. Start it from the beginning? (y or n) y Starting program: /home/Vicente/SVN/bin.v2/vbe_interthreads/libs/interthreads/te st/x_sort2.test/gcc-3.4.4/debug/link-static/threading-multi/x_sort2.exe [New thread 1876.0x8dc] [New thread 1876.0x938] std::sort: reverse 0..100000 0.05 s [New thread 1876.0x624] [New thread 1876.0xe28] 55 Program exited normally. (gdb) run Starting program: /home/Vicente/SVN/bin.v2/vbe_interthreads/libs/interthreads/te st/x_sort2.test/gcc-3.4.4/debug/link-static/threading-multi/x_sort2.exe [New thread 3240.0xef8] [New thread 3240.0xfb8] std::sort: reverse 0..100000 0.05 s [New thread 3240.0x5d4] [New thread 3240.0xe04] [New thread 3240.0x884] [Switching to thread 3240.0x884] Quit (gdb) q The program is running. Exit anyway? (y or n) y

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Re: [boost] [lexical_cast] A suggestion
by Anders Dalvander 07 Feb '09

07 Feb '09

> some bashing snipped... Why not compromise? 1. Make the lexical_cast changes for optional that Andrew Troschinetz suggested. 2. Add the following convert_to.hpp file: #include <boost/lexical_cast.hpp> #include <boost/optional.hpp> namespace boost { template <typename Target, typename Source> inline Target convert_to(const Source& arg) { return lexical_cast< optional<Target> >(arg).get_value_or(Target()); } template <typename Target, typename Source> inline Target convert_to(const Source& arg, const Target& fallback) { return lexical_cast< optional<Target> >(arg).get_value_or(fallback); } } 3. Use convert_to instead of lexical_cast. 4. Everyone happy? Regards, Anders Dalvander

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[config] [random] usage of BOOST_NO_MEMBER_TEMPLATE_FRIENDS
by Steven Watanabe 07 Feb '09

07 Feb '09

AMDG Boost.Random uses BOOST_NO_MEMBER_TEMPLATE_FRIENDS to decide whether it is safe to define the stream operators. #if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) template<class CharT, class Traits> friend std::basic_ostream<CharT,Traits>& operator<<(std::basic_ostream<CharT,Traits>& os, const uniform_int& ud); template<class CharT, class Traits> friend std::basic_istream<CharT,Traits>& operator>>(std::basic_istream<CharT,Traits>& is, uniform_int& ud); #endif However, the documentation of BOOST_NO_MEMBER_TEMPLATE_FRIENDS says that BOOST_NO_MEMBER_TEMPLATE_FRIENDS is defined if the compiler doesn't support template<class P> friend class frd; It seems from https://svn.boost.org/trac/boost/ticket/1068 that these do not correspond exactly. Are there any compilers that we still care about, that don't support this use of friend? Also, it sounds to me like the use of BOOST_NO_OPERATORS_IN_NAMESPACE is wrong because it is documented as "Compiler requires inherited operator friend functions to be defined at namespace scope" and there is no inheritance here. Is this right? In Christ, Steven Watanabe

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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

2 1

Coverity Static Code Analysis
by Michael Fawcett 05 Feb '09

05 Feb '09

Purely out of curiosity, how come Boost isn't at Rung 1 in the Coverity Scan Ladder? http://scan.coverity.com/ Boost and Boost.Build are both listed in Rung 0, so it appears that the only step left is selecting a Boost/Coverity liaison. http://scan.coverity.com/newproj.html --Michael Fawcett

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[svn] sandbox access
by Kasra 05 Feb '09

05 Feb '09

Hi, I have requested a svn access to the sandbox for my crypto library. However, I haven't received my e-mail's reply yet. How long should I expect to wait?? With Best Regards Mr. Kasra Nassiri Department of Mathematics & Computer Science Imperial College London

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[build] Using 'distcc' with bjam
by Dean Michael Berris 04 Feb '09

04 Feb '09

Hi Everyone, Has anybody tried using distcc instead of GCC with Boost.Build and Boost.Jam? Thanks in advance. -- Dean Michael C. Berris Software Engineer, Friendster, Inc.

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[python] Expose a struct with a std::vector<std::string> member
by Tiago Coutinho 04 Feb '09

04 Feb '09

Hello all, I am new to boost::python. I have access to a C++ library which I want to expose to python using boost. One of the structs I want to expose is something like: #include <vector> struct ExampleStruct { std::vector<std::string> elements; }; I would like to expose this class but I like to avoid having to write a wrapper that would inefficiently have to copy the vector contents to a boost::python::list member. Is there a way to do this? Thank you very much in advance Cheers Tiago

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[mpl]iter_fold_if use of apply1 instead of iter_apply1 maybe bug?
by Larry Evans 04 Feb '09

04 Feb '09

The following code line: https://svn.boost.org/trac/boost/browser/trunk/boost/mpl/iter_fold_if.hpp#L… shows apply1<Predicate,Iterator>; however, shouldn't this be iter_apply1<Predicate,Iterators> because, just from the name, Iterator is an iterator and needs to be deref'ed. Also, the previous line: not_< is_same<Iterator,LastIterator> > further suggests that Iterator is actually an iterator. I know it works presently; however, I really don't understand why.

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Any real-world need for static_cast_iterator, const_cast_iterator, dynamic_cast_iterator?
by Nigel Stewart 04 Feb '09

04 Feb '09

In addition to the specialised adaptors in the boost iterator library, does it make any sense to add: static_cast_iterator const_cast_iterator dynamic_cast_iterator ...iterator adaptors providing embedded static_cast<>, const_cast<> or dynamic_cast<> when dereferencing? (Rather than just throwing them straight on the scrap heap...) - Nigel ---------------------------------------------- template<typename T, typename I> class static_cast_iterator : public boost::transform_iterator < T (*)(const typename I::reference), I > { private: typedef typename I::reference F; typedef typename boost::transform_iterator< T (*)(const F), I> B; public: static_cast_iterator() {} static_cast_iterator(const I &i) : B(i,&doCast) {} operator const I &() const { return B::base(); } static_cast_iterator &operator++() { B::operator++(); return *this; } static_cast_iterator &operator--() { B::operator--(); return *this; } private: static T doCast(const F val) { return static_cast<T>(val); } }; template<typename I> class const_cast_iterator : public boost::transform_iterator < typename boost::remove_const<typename I::reference>::type (*)(const typename I::reference), I > { private: typedef typename I::reference F; typedef typename boost::remove_const<F>::type T; typedef typename boost::transform_iterator< T (*)(const F), I> B; BOOST_STATIC_ASSERT(boost::is_const<F>::value); BOOST_STATIC_ASSERT(!boost::is_const<T>::value); public: const_cast_iterator() {} const_cast_iterator(const I &i) : B(i,&doCast) {} operator const I &() const { return B::base(); } const_cast_iterator &operator++() { B::operator++(); return *this; } const_cast_iterator &operator--() { B::operator--(); return *this; } private: static T doCast(const F val) { return const_cast<T>(val); } }; template<typename T, typename I> class dynamic_cast_iterator : public boost::transform_iterator < T (*)(const typename I::reference), I > { private: typedef typename I::reference F; typedef typename boost::transform_iterator< T (*)(const F), I> B; BOOST_STATIC_ASSERT(boost::is_pointer<F>::value || boost::is_reference<F>::value); BOOST_STATIC_ASSERT(boost::is_pointer<T>::value || boost::is_reference<T>::value); public: dynamic_cast_iterator() {} dynamic_cast_iterator(const I &i) : B(i,&doCast) {} operator const I &() const { return B::base(); } dynamic_cast_iterator &operator++() { B::operator++(); return *this; } dynamic_cast_iterator &operator--() { B::operator--(); return *this; } private: static T doCast(const F val) { return dynamic_cast<T>(val); } };

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warnings from gcc-4.3.3 -Wall
by John Salmon 04 Feb '09

04 Feb '09

I recently upgraded to gcc/4.3 and started seeing warnings from gcc-4.3.3 -Wall suggesting parentheses around && within ||. It would be great if boost/1.38 could repair these by adding a few pairs of parentheses before the final release. N.B. I did not do an exhaustive compilation of everything in boost with gcc -Wall. The three cases below are the ones that my code base just happens to hit. Thanks, John Salmon /proj/desres/root/Linux/x86_64/boost/1_37_0-14/Release/include/boost/tuple/tuple_comparison.hpp:73: warning: suggest parentheses around && within || /proj/desres/root/Linux/x86_64/boost/1_37_0-14/Release/include/boost/iostreams/filter/symmetric.hpp:126: warning: suggest parentheses around && within || /proj/desres/root/Linux/x86_64/boost/1_37_0-14/Release/include/boost/iostreams/detail/streambuf/indirect_streambuf.hpp:285: warning: suggest parentheses around && within ||

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[mpl] holder class for types with external linkage (similar to integral contants)
by klaus triendl 04 Feb '09

04 Feb '09

Recently, I've been in need of a holder class for strings with external linkage but I didn't find an mpl datatype that could wrap an externally defined entity. Instead of creating a quick solution working for my needs I thought the mpl library could benefit from a generic holder class similar to the integral constant holders. <code> template<typename T, T N> struct external_c { // make it a nullary metafunction typedef external_c type; typedef T value_type; // correct? requirements? typedef integral_c_tag tag; // can't make a static compile time constant but only a static // function static value_type value() { return N; } // implicitly convertible to its runtime type value operator value_type() const { return this->value(); } }; // e.g. extern const char string1[]; const char string1[] = "string1"; extern const std::string string2; const std::string string2("string2"); int main() { external_c<const char* const, string1> x1; external_c<const std::string&, string2> x2; std::cout << x1 << "\n"; std::cout << x2.value() << "\n"; return 0; } </code> The name 'external_c' is just a quick idea and would have to be changed anyway with c++09's possibility to use types with internal linkage in template programming. Would it be reasonable to integrate this into the mpl? Any comments? Klaus Triendl

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[Serialization] Need help with binary archive deserialization error
by George van Venrooij 04 Feb '09

04 Feb '09

Hi, I just ran into an issue with serialization which is very peculiar. When serializing a complex class structure to an archive all goes well without errors. However, when trying to read back the data it works with all xml and text archive types, but when using binary archives I get an archive exception while loading. The exception occurs while loading an array of 3 doubles. From what I can make up out of the code, the archive says there are 20 bytes to load, while the library expects 24. Apparently I'm doing something that has no effect for text-based serialization, but does for binary. Since I didn't find any posts or tickets for this issue I assume I have made a mistake somewhere, only I have been looking for hours and cannot seem to find it. So any suggestions on where to look would be welcome, even the obvious ones ;-) Regards, George van Venrooij

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[interprocess] Severe bug in sp_counted_impl.hpp!
by Lars Hagström 04 Feb '09

04 Feb '09

Hi, I believe that there is a bug in sp_counted_impl_pd::destroy(). Currently the method looks like this: void destroy() // nothrow { //Self destruction, so get a copy of the allocator //(in the future we could move it) this_allocator a_copy(*this); BOOST_ASSERT(a_copy == *this); this_pointer this_ptr (this); //Do it now! scoped_ptr<this_type, scoped_ptr_dealloc_functor<this_allocator> > (this_ptr, a_copy); typedef typename this_allocator::value_type value_type; detail::get_pointer(this_ptr)->~value_type(); } What I think is wrong is on the deallocator functor line. I believe that it should read scoped_ptr<this_type, scoped_ptr_dealloc_functor<this_allocator> > DEALLOCATOR(this_ptr, a_copy); The missing thing is the name for the scoped_ptr instance (the one I called DEALLOCATOR, to make it stand out). And since the name is missing it will become an anonymous instance, which will be destroyed *before* the destructor is called on this_ptr. The upshot is that with the bug we deallocate the memory and then call the destructor, rather than the opposite. If you're unlucky some other thread/process has allocated that memory for some other use, and you will then be running the destructor on that instead... I'm writing a ticket on this as well, just so it doesn't get overlooked. (If I'm wrong about all this my face will be red for a while...) Cheers Lars

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boost serialization and alignment
by meir shoham 04 Feb '09

04 Feb '09

Hi, When I'm setting struct member alignment as 1 BYTE in visual studio 2005 project environment (C++), I receive alignment error coming from boost serialization library (STATIC_ASSERT) at compilation time. This problem does not happen when I wrap the structures containing the boost serialization template methods using #pragma pack(push,1) and #pragms pack(pop). I'm using boost only to serialize/deserialize strctures and classes to/from XML. Is there a problem for boost serialization library to handle alignment other then the default one? Thanks, Meir

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