August 2007 - Boost-users - lists.preview.boost.org

[Boost][Serialization] Possible Bug in Optional.hpp
by Marc Viala 22 Aug '07

22 Aug '07

I've downloaded recently the version Boost 1.34.1 and performed some tests on ours applications integrating Boost components. During theses tests, I've tried to deserialize some XML archives generated w/ Boost 1.33.1 including some boost::optional<> instances and I've observed that the Visual C++ 7.1 IDE emits run-time checks in the load<boost::optional<>>() @ line 60 in file boost/serialization/optional.hpp. template<class Archive, class T> void load( Archive & ar, boost::optional<T> & t, const unsigned int /*version*/ ){ bool tflag; ar >> boost::serialization::make_nvp("initialized", tflag); if (tflag){ unsigned int v; if(3 < ar.get_library_version()){ ar >> make_nvp("item_version", v); } detail::stack_construct<Archive, T> aux(ar, v); ^^^^^^^^^^^^^^^^^^^^^^^^ Here Run-Time Check Failure #3 - The variable 'v' is being used without being defined. ar >> boost::serialization::make_nvp("value", aux.reference()); t.reset(aux.reference()); } else { t.reset(); } } Is it possible to avoid this run-time check by a preinitialisation of the local variable "v"? Is it a Bug? Best regards, Used Configurations: Windows XP Boost 1.34.1 (through Boost Installer w/ DLL libraries) Marc Viala

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Re: [Boost-users] Serialization newbie needs help
by Dominick Layfield 22 Aug '07

22 Aug '07

>> > Obviously, I can just switch to a different serialization library >> > (e.g. s11n). > > I believe that library also has serialization of pointers Darn it! Foiled at every turn! :-) If that is the case, maybe you might consider updating/clarifying the "Overview -> Other implementations" section of the docs. There you imply that s11n doesn't do this. (Maybe it didn't back when you wrote the docs.) >> But as much as possible, I would like to stick with >> > whatever is most "standard". And as part of the Boost family, I'm >> > guessing that boost::serialization is top dog here. Would that be >> > right? Is this library included in any of the proposed C++ >> > standards (TR2, C++0x)? > > This serialization library will never be part of any C++ standard. Oh. That's disappointing. Why not? Too much bureaucracy involved? > Because normally one doesn't want to change data while its being saved > one will typically have something like the following in his program. > > FileSave(const MyData & md){ > // create archive > oa << md; // no need for "const cast" because md is already "const" > ... > } Okay. That makes a lot of sense. Let me ask another newbie question, about how to get data in and out of an archive. I have to work with legacy C-based code that delivers/accepts data in a char* buffer. My code to serialize data into and out of this buffer is both convoluted and inefficient. It looks something like this: my_class mc; void read_from_cbuffer(const char* buf, const size_t buf_sz) { std::string buf_str(buf, buf_sz); std::istringstream iss(buf_str); boost::archive::text_iarchive ia(iss); ia >> mc; } void write_to_cbuffer(char** buf_p, size_t* buf_sz_p) { std::ostringstream oss; boost::archive::text_oarchive oa(oss); oa << mc; *buf_p = new char[oss.str().size()]; memcpy(*buf_p, oss.str().c_str(), oss.str().size()); *buf_sz_p = oss.str().size(); } Any suggestions about how this can be done better? Thanks, -- Dominick

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Boost 1.34.1 + MinGW + STLport5-dll
by Johannes Barop 22 Aug '07

22 Aug '07

Hello, I'm trying to build Boost 1.34.1 with MinGW and STLport5. With no success. I created a user-config.jam in my home directory with following content: <snip> using stlport : 5.1 : "C:\\MinGW\\STLport-5.1.3\\stlport" "C:\\MinGW\\STLport-5.1.3\\lib" ; </snip> Then I tryed to build Boost with the following command line: bjam --toolset=gcc stage stdlib=stlport runtime-link=shared Which gave me a lots of errors. See here: http://nopaste.php-quake.net/2727 Any ideas what might be wrong? Cheers, Johannes

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Subject : [Multi-index] -- using a hashed unique index that is not part of the hashed value
by Oliver Kania 22 Aug '07

22 Aug '07

Hello, what I basically want to do is using multi-index like a hashmap. I want to use vector<long> as key. However, all the examples I found are using member-fields of the values or the values themselves as key. Is it not possible to use multi-index like a hash_map<value,key> where the key is independent of the value type ? If yes, could someone please provide an example ? regards, Oliver

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Re: [Boost-users] boost bind beginner throw problem
by Taglioretti Roberto 22 Aug '07

22 Aug '07

From: "Peter Dimov" > The following program works for me with VC 7.1. > #include <boost/bind.hpp> > struct Error {}; > struct X { void test( int i ) throw( Error ) {}}; > int main() > { > X obj; > boost::bind( &X::test, obj, _1 ); >} I try to compile your example, theese are the error messages on my VC 7.1: C:\sviluppo\r2\boost\build\1.34.1\include\boost\lambda\detail\bind_functions.hpp(544): error C2553: no legal conversion of return value to return type 'type' "const boost::lambda::lambda_functor<T>" with [ T=boost::lambda::lambda_functor_base<boost::lambda::action<4,boost::lambda::function_action<4>>,boost::tuples::tuple<const boost::lambda::detail::bind_traits<void (__thiscall SVLCompiler::Analysis::* const )(SVLCompiler::Analysis::Iteratorp_t,SVLCompiler::Analysis::Iteratorp_t)>::type,const boost::lambda::detail::bind_traits<SVLCompiler::Analysis *const >::type,const boost::lambda::detail::bind_traits<const boost::lambda::placeholder1_type>::type,const boost::lambda::detail::bind_traits<const boost::lambda::placeholder2_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type>> ] C:\sviluppo\r2\boost\build\1.34.1\include\boost\lambda\detail\bind_functions.hpp(544): error C2664: "boost::lambda::lambda_functor<T>::lambda_functor(const boost::lambda::lambda_functor<T> &)": impossibile convertire il parametro 1 da "boost::lambda::lambda_functor_base<Act,Args>" a "const boost::lambda::lambda_functor<T> &" with [ T=boost::lambda::lambda_functor_base<boost::lambda::action<4,boost::lambda::function_action<4>>,boost::tuples::tuple<const boost::lambda::detail::bind_traits<void (__thiscall SVLCompiler::Analysis::* const )(SVLCompiler::Analysis::Iteratorp_t,SVLCompiler::Analysis::Iteratorp_t)>::type,const boost::lambda::detail::bind_traits<SVLCompiler::Analysis *const >::type,const boost::lambda::detail::bind_traits<const boost::lambda::placeholder1_type>::type,const boost::lambda::detail::bind_traits<const boost::lambda::placeholder2_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type>> ] and [ Act=boost::lambda::action<4,boost::lambda::function_action<4>>, Args=boost::tuples::tuple<const boost::lambda::detail::bind_traits<void (__thiscall SVLCompiler::Analysis::* const )(SVLCompiler::Analysis::Iteratorp_t,SVLCompiler::Analysis::Iteratorp_t) throw(SVLCompiler::Analysis::Error_check)>::type,const boost::lambda::detail::bind_traits<SVLCompiler::Analysis *const >::type,const boost::lambda::detail::bind_traits<const boost::lambda::placeholder1_type>::type,const boost::lambda::detail::bind_traits<const boost::lambda::placeholder2_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type, I hope you can help me :-( -- Roberto Taglioretti *sono affetto da discromatopsia, per favore evitate l'invio di mail o allegati colorati* *I have dyschromatopsia, please do not send coloured text or email and attach* Aderite al progetto SETI: http://setiweb.ssl.berkeley.edu/team_display.php?teamid=30233

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boost::spirit
by Christer Borgqvist 22 Aug '07

22 Aug '07

Hello Boost Experts I'm using the BDS 2006 and trying to use the spirit library like this #include <boost/spirit.hpp> in my function string hex="0x1F"; unsigned int value; parse( hex.c_str() , hex_p[assign_a(value)] ); // i get following compiler error [C++ Error] closures.hpp(238): E2299 Cannot generate template specialization from 'impl::closure_frame_holder<FrameT>' thanks for any help //Christer

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Bug in shared_array
by Hansi Hansi 22 Aug '07

22 Aug '07

Hello, I think I have found an bug in the shared_array implementation in version 1.34.1 for VC8.0. I hope that this is the right location to post this and that one fixes this file. I think that the implementation needs this: #elif defined( _MANAGED ) static void unspecified_bool( this_type*** ) { } typedef void (*unspecified_bool_type)( this_type*** ); operator unspecified_bool_type() const // never throws { return px == 0? 0: unspecified_bool; } it is the same implementation as used in shared_ptr. If I don't have this I get during the call a buffer overrun. Best regards Hansjörg __________________________________________________________________________ Erweitern Sie FreeMail zu einem noch leistungsstärkeren E-Mail-Postfach! Mehr Infos unter http://produkte.web.de/club/?mc=021131

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Re: [Boost-users] Serialization newbie needs help
by Dominick Layfield 21 Aug '07

21 Aug '07

"Robert Ramey" <ramey(a)rrsd.com> wrote: > Actually, I've considered reviewing all the email in this list and > summarizing > the results in a section "Hints and Troubleshooting Tips". I think this > is useful and necessary and useful, but I just havent gotten around to it. That sounds ideal. > > But if you could provide me an example of when pointer serialization > > shines, > > then I would say "Aha! Now I understand why Robert went to so much > > trouble to make this work.", and I could be at peace with the world > > again! :-) > > LOL - I haven't had time to make any real apps lately. So... no example at all? My problem is that I just don't see when pointer serialization would be a big win. But I can't tell if I just have a limited perspective. That's why I was genuinely hoping that you could provide a concrete example. Naturally, a system that "just works" no matter what structure is thrown at it sounds very enticing. However, as you have acknowledged, the system is not foolproof, and user gotchas remain. One way to eliminate the gotchas would be to reduce the scope of the library. Clearly, this is unlikely to happen, as (i) you've invested a lot of time and effort getting the pointer magic to work, and (ii) there are probably a lot of applications out there that would break if you did so. I for one would certainly appreciate a simplified version which omitted the pointer magic, and thus removed the const trap and similar issues. If I want to set up pointers within an object, then I can do so manually using the type-specific load()/save() functions. Obviously, I can just switch to a different serialization library (e.g. s11n). But as much as possible, I would like to stick with whatever is most "standard". And as part of the Boost family, I'm guessing that boost::serialization is top dog here. Would that be right? Is this library included in any of the proposed C++ standards (TR2, C++0x)? > > BTW, I don't want to sound like I'm bashing your library, so let me > > end with a compliment. I think the symmetric design of serialize(), > > with the same function used for both input and output, is one of the > > prettiest > > idioms I've seen in years. > > And that's the one thing I didn't do - I believe I "borrowed" it from Jens > Maurer. Hah! Ooops. Well, that compliment backfired! ;-) Let's try again: I *really* appreciate the built-in support for all the STL container classes. So far, these have "just worked" perfectly for me. Nice work! > One tiny point. I'm aware that the "const" trap is annoying. But I've > become > convinced that the annoyance is small compared to the hassles it saves me > and users from. I suspect that those who have a problem with aren't in the > habit of using "const" everywhere they can. It does seem bizarre to have to const-cast an object just so that it can be output. I presume that the majority of objects that are to be serialized are not intrinsically constant, so this needs to be done the majority of the time. And it looks dangerous. What does the const-cast actually mean in this context? I assume it means: "I promise that no other thread is going to modify the object (or anything its pointers point to) while the serialize() operation is pending. Is that correct? If so, then shouldn't it be solved explicitly with concurrent programming primitives (i.e. mutexes or similar)? -- Dominick

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An easy one
by Panayiotis 21 Aug '07

21 Aug '07

Hello, what is the equivalent of: void foo(int array[]) for boost::array? Thanks, Panayiotis

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Can Python "httplib" module be directly embedded in C++ ?
by Raja Cherukuri 21 Aug '07

21 Aug '07

Hello, I am trying to use python to do my XML post ? Can I do this by directly calling import on the httplib like this and setting parameters ? ex: boost::python::object http_module((boost::python::handle<>(boost::python::borrowed(PyImport_Ad dModule("httplib"))))); boost::python::<....some kind of python compile time...interface...> h = < some kind of cast...> http_module.HTTP("http://www.abc.com"); h.putrequest('POST', selector) h.putheader('content-type', content_type) h.putheader('content-length', str(len(body))) h.endheaders() h.send(body) Or should the actual code for this object reside in a text file and I should call exec_file ? Thanks in Advance. - Raja

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