February 2010 - Boost-users

FW: [serialization] Polymorphic serialization with polymorphic archives problem...
by Bogdan 21 Feb '10

21 Feb '10

Hi Damien, Thank you for your quick reply. I believe I followed the rules: 1. polymorphic_derived1 and polymorphic_derived2 do include the serialization of the base class via "ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(polymorphic_base); " 2. there is no usage of BOOST_CLASS_EXPORT ( and there shouldn't be any: according to the documentation, in a dll setup one must declare BOOST_CLASS_EXPORT_KEY in the headers containing the classes to be serialized and BOOST_CLASS_EXPORT_IMPLEMENT in the .cpp files). In my example, there are exactly three declarations of BOOST_CLASS_EXPORT_KEY: one in polymorphic_base.hpp, and two in polymorphic_derived2.hpp one for polymorphic_derived1 and another for polymorphic_derived2. Similarly, there are only three usages of BOOST_CLASS_EXPORT_IMPLEMENT. 3. for deeper hierarchies where every class can be potentially serialized, one should probably register all the classes and not just the most derived children. I have the feeling that the type of deployment (dll vs exe) is the crux of the problem. For that, I created four different scenarios with the same source files and I got the following results: 1. all files in one exe with the serialization library linked statically - WORKS AS EXPECTED. 2. all files in one exe with the serialization library linked as a dll - WORKS AS EXPECTED. 3. serialization files in a separate dll. Both the main executable and my dll link with the dll version of the serialization library: main.exe my_serialization.dll boost_serialization.dll my_serialization.dll boost_serialization.dll Builds OK but FAILS at runtime , at run time I get a C++ exception BEFORE main() in basic_serializer_map.cpp around the line 48: 'archive_exception::multiple_code_instantiation with the message "code instantiated in more than one module - polymorphic_base"' 4. serialization files in a separate dll. Both the main executable and my dll link with the static version of the serialization library: main.exe my_serialization.dll boost_serialization.lib my_serialization.dll boost_serialization.lib Builds OK but FAILS at runtime while trying to serialize with the following exception thrown in oserializer.hpp(line 424):struct polymorphic::save(): 'unregistered void cast class polymorphic_derived1<-polymorphic_base in function 'int __cdecl main(int,char *[])'' The source code in the scenarios above is identical with the exception of dllexport/dllimport declaration needed for dlls. Whenever the serialization code is relegated to a different library it seems there are problems with boost serialization: - if boost is linked as a static lib into a user dll, the class serializers do not get registered at all with their associated map singleton. - if boost is linked as a dynamic lib into a user dll, the class serializers register twice with the map singleton of the polymorphic base archive. I don't want to add them here but I can provide any of the projects above to those interested. Thank you all, Bogdan ============================================================================ ============== > Hi, > I have the same scenario, and it's not a problem. > If i understand (my english is poor, sorry) well. > But there is differences: > - I use GCC compilers (but boost is portable). > - I use static linking. > Probably this differences should not have consequences on the result. > I didn't read your code... Had you follow this rules ? > - Register child class (a simple way is using the BOOST_CLASS_EXPORT > macro). > - In the serialize method of your child class, call the > serialization of parent's class (optional). I use > BOOST_SERIALIZATION_BASE_OBJECT's macro. > > If you register child class it should be ok... > Regards, > Damien. > >

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non-blocking read
by David Kaplan 21 Feb '10

21 Feb '10

I'm trying to implement a non_blocking read as follows (based on some code on the net): void util::net::set_result(optional<boost::system::error_code>* a, boost::system::error_code b) { a->reset(b); } template <typename MutableBufferSequence> optional<boost::system::error_code> util::net::read_non_blocking(ip::tcp::socket *sock, const MutableBufferSequence& buffers, int timeoutSec) { optional<boost::system::error_code> timer_result; deadline_timer timer(sock->io_service()); timer.expires_from_now(boost::posix_time::seconds(timeoutSec)); timer.async_wait(boost::bind(set_result, &timer_result, _1)); optional<boost::system::error_code> read_result; async_read(*sock, buffers, boost::bind(set_result, &read_result, _1)); sock->io_service().reset(); while (sock->io_service().run_one()) { if (read_result) timer.cancel(); else if (timer_result) { sock->cancel(); throw system_error(boost::system::error_code(errc::timed_out, get_generic_category())); } } return read_result; } I call the code as follows: util::net::read_non_blocking(Module::_socket, buffer(buf, 4), 1); (_socket is a ptr of type tcp::socket) However I'm having problems linking: undefined reference to `boost::optional<boost::system::error_code> util::net::read_non_blocking<boost::asio::mutable_buffers_1>(boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >*, boost::asio::mutable_buffers_1 const&, int) Also, what will this code return exacty?

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Memory tools
by Bo Jensen 21 Feb '10

21 Feb '10

For a multi threaded project I need to be able to closely monitor memory stats such as memory usage, number of allocations etc. Of course I could overload new/delete, but do boost have such memory tools or do you know of other libraries that has this feature ? Any suggestions ? Sorry if this is slightly off-topic.

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Can't asio::write when len > 14
by David Kaplan 21 Feb '10

21 Feb '10

I can't seem to write to my tcp socket with boost::asio any buffer with len > 14: uint8_t tmp[20]; int len = 20; asio::write(_socket, buffer(tmp, len)); if len > 14, it will always only return 14 bytes written! If len < 14, it writes correctly. What's going on?

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[program_options] allow_guessing issue
by Filip Konvička 21 Feb '10

21 Feb '10

Hi, I've just upgraded to boost 1.42 from 1.40, and it seems that the new feature 'allow_guessing', a default setting, breaks my existing code. I have two options: "lang" and "lang-dir", the first obviously a prefix of the other, and when my program is run with "--lang=en_US --lang-dir=.", the first argument is interpreted as "lang-dir". Even though the documentation says somewhere that one argument should not be a prefix of another with 'allow_guessing' on, this is a breaking change and should be put in a big red box somewhere on the front page :-) If the change is intended to be kept for the future, it would be wise to detect the problem by examining the options, rather than wait until another problem occurs (in my case, the runtime exception is 'multiple_options' when the user uses both options, and - much worse! - the option gets misinterpreted without a warning if he only uses the shorter option). Cheers, Filip

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[program_options] allow_guessing compatibility issue
by Filip Konvička 21 Feb '10

21 Feb '10

Hi, I've just upgraded to boost 1.42 from 1.40, and it seems that the new feature 'allow_guessing', a default setting, breaks my existing code. I have two options: "lang" and "lang-dir", the first obviously a prefix of the other, and when my program is run with "--lang=en_US --lang-dir=.", the first argument is interpreted as "lang-dir". Even though the documentation says somewhere that one argument should not be a prefix of another with 'allow_guessing' on, this is a breaking change and should be put in a big red box somewhere on the front page :-) If the change is intended to be kept for the future, it would be wise to detect the problem by examining the options, rather than wait until another problem occurs (in my case, the runtime exception is 'multiple_options' when the user uses both options, and - much worse! - the option gets misinterpreted without a warning if he only uses the shorter option). Cheers, Filip

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[multi_array] std::swap and subarray
by Sergey Mitsyn 21 Feb '10

21 Feb '10

Hello! I've got somehow unexpected behaviour of std::swap with multi_array's subarray. For example, given a 2x2 multi_array: boost::multi_array<double, 2> a; a.resize( boost::extents[2][2] ); for (int i = 0; i < 2; ++i) for (int j = 0; j < 2; ++j) a[i][j] = (i+1)*10 + j+1; std::swap( a[0], a[1] ); for (int i = 0; i < 2; ++i) { for (int j = 0; j < 2; ++j) std::cout << a[i][j] << " "; std::cout << std::endl; } With msvc 2008 + boost 1.42, one of the rows overwrites the other and the output is: 21 22 21 22 The fastest hacky solution i've came is this: namespace std { template <typename TValue, int K> void swap( boost::detail::multi_array::sub_array<TValue, K> &lhs, boost::detail::multi_array::sub_array<TValue, K> &rhs) { boost::multi_array<TValue, K> tmp = lhs; lhs = rhs; rhs = tmp; } } // namespace std Now, the rows are properly swapped and the output is: 21 22 11 12 Well, probably that's not a problem for now, but I dunno if it's a bug or std::swap is not supported - coundn't find anything about this. ---------------- Sergey Mitsyn.

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[serialization] Polymorphic serialization with polymorphic archives problem...
by Bogdan 21 Feb '10

21 Feb '10

Hi all, I am unable to use the following functionality in boost 1.42 built with Visual Studio 2008: - serialize/deserialize a derived class via a base class pointer using polymorphic archives. - the class serialization is implemented in a DLL using a base polymorphic archive. - the actual serialization is performed in a separate executable (linked with the DLL above); in that executable I use a polymorphic text archive. The documentation states this scenario is legitimate; however none of the tests shipped with boost demonstrates it (there are examples either about polymorphic classes or polymorphic archives but no test combining both). The example proving my point is a variation of the test using test_dll_exported.cpp and polymorphic_derived2.cpp where I removed the template-based archives defeating the purpose of polymorphic archives. My example throws an exception before main(), complaining the serializers try to register twice with the archive map singleton of the polymorphic base class. I described the same issue in the thread "[serialization] Can one deserialize a derived classes via pointers to the base class using polymorphic archives in a DLL context?" I posted in gmane.comp.lib.boost.devel where I provided more implementation details. Robert Ramey has graciously replied with a series of suggestions; unfortunately my example seems to have fulfilled all the conditions he mentioned. So, my question is: has anyone been able to run successfully a scenario similar to the one I described? Thank you, Bogdan ============================================================================ ====== I am enclosing a bare-bone example containing 8 files in two project files plus one solution file. My environment setup contains: _CL_=/D_HAS_ITERATOR_DEBUGGING#0 /D_SECURE_SCL#0 /wd4996 /wd4503 /DBOOST_ALL_NO_LIB BOOST_HOME=C:\_APP_\boost_1_42_0 Boost header files are installed under %BOOST_HOME%\include while the libraries are installed under %BOOST_HOME%\lib. I used Boost libraries (multi-threaded DLL versions) built with no automatic dependencies (note /DBOOST_ALL_NO_LIB above). Their names are boost_serialization-mt.lib and boost_serialization-mt-gd.lib for Release/Debug configurations, respectively. The PropertyPages/ConfigurationProperties/Debugging/Environment contains: PATH=$(BOOST_HOME)\lib;$(PATH) used while debugging.

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[Fusion] documentation - bad link [Phoenix] Related question
by OvermindDL1 21 Feb '10

21 Feb '10

On the documentation page: http://www.boost.org/doc/libs/1_42_0/libs/fusion/doc/html/fusion/functional… Search for the sentence near the bottom of: The library provides both a strictly typed and a generic variant for this transformation. The latter should be used in combination with Boost.Functional/Forward to attack The Forwarding Problem. The words "Boost.Functional/Forward" are a link pointing to: http://www.boost.org/libs/functional/forward/doc/html/index.html However, that link does not exist, and I tried searching through: http://www.boost.org/libs/functional/ But I could not find anything that even had the word "forward" in it through any sub-link (courtesy of google, also searched in 1_41_0). Where is this documentation that Fusion is pointing to? Also, why does Phoenix2 not use the Fusion fused/unfused/etc... to support passing constants like the integer 42 directly to an actor? Is there some limitation that would not make it work, or...?

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MPL. Nested Lambdas
by dilas dilas 21 Feb '10

21 Feb '10

Please, tell me if one can write nested lambda expressions like " template<class Result, class Seq, class Elem> struct pairs: bm::fold<Seq, Result, bm::push_back<_1,bm::pair<Elem, _2 > > >{}; template<class Seq1, class Seq2> struct AllPairs: bm::fold<Seq1, bm::vector<>, pairs<_1,Seq2,_2> >{}; " without using intermediate metafunctions.

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