February 2010 - Boost-users - lists.preview.boost.org

Re: [Boost-users] [serialization] Polymorphic serialization with polymorphic archives problem...
by Bogdan 23 Feb '10

23 Feb '10

> Bogdan wrote: > > > 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"' > > This would indicate that the serialization for polymorphic_base is included in BOTH the > mainline and the DLL. Check that the serialization function is NOT an inline definition. > the polymorphic_base.cpp should only be needed when compiling the DLL. > > option 1 > > include serialization definition for polymorphic_base in my_serialization.dll > > option 2 > > include serialization definition for polymorphic_base in it's own dll. > > > > 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 *[])'' > > This is probably failing due to the compiler stripping out code not explicitly referred to. > Since it's not referrred to, the linking doesn't include it from the library. ==================================================== Hello Robert, Thank you for your reply. The serialization functions are not inline: their bodies are defined inside the DLL. I did the following experiments: - I skipped manually the registration exception in the debugger and it turns out that all the serialized classes have their serializers registered twice. - if in the main function I do not call serialize/deserialize, the program runs ok; I agree with you, the program doesn't do anything but it proves that the registration is triggered by the actual usage of the serialization functionality and not by any eventual inline. I am under the impression I followed all the directions in the documentation and yet I keep hitting that glitch. Thank you, Bogdan PS. As for the case where boost serialization links as a static inside a user DLL, it fails, indeed, due to the compile stripping out code. Is there a workaround for this you would suggest?

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flyweight: lazy initialization
by Johannes Brunen 23 Feb '10

23 Feb '10

Hello, Is it possible to initialize a flyweight lazy or better on user request? I have the problem that I have a custom allocator that is not ready to run before main. Currently, the flyweight initialization is performed on init of the fleiweight_core static_initilaizer member. This scheme does outrule the usage of the flyweight utility in my application. Any help would be appreciated. Best, Johannes ____________ Virus checked by G DATA AntiVirusKit Version: AVF 19.736 from 21.02.2010 Virus news: www.antiviruslab.com

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fusion result_of::at<Seq, N>::type doesn't return the type I expect
by Hicham Mouline 23 Feb '10

23 Feb '10

Hi, This code prints double and 0 where I would expect is_same to print 1. msvc2008, boost trunk #include <iostream> #include <boost/type_traits/is_same.hpp> #include <boost/mpl/range_c.hpp> #include <boost/mpl/distance.hpp> #include <boost/mpl/vector.hpp> #include <boost/mpl/find.hpp> #include <boost/fusion/include/mpl.hpp> #include <boost/fusion/include/size.hpp> #include <boost/fusion/include/at.hpp> #include <boost/fusion/include/for_each.hpp> #include <boost/fusion/include/adapt_struct.hpp> struct p { double f0; double f1; double f2; unsigned int f3; unsigned int f4; unsigned int f5; unsigned int f6; }; /// macro required to be at global namespace BOOST_FUSION_ADAPT_STRUCT( p, (double, f0) (double, f1) (double, f2) (unsigned int, f3) (unsigned int, f4) (unsigned int, f5) (unsigned int, f6) ) typedef boost::mpl::vector<double, unsigned int> dtt; typedef boost::fusion::result_of::at_c<p,0>::type t0; int main() { std::cout<< typeid(t0).name() <<std::endl; std::cout<< boost::is_same< t0, double >::value <<std::endl; return 0; } I am certain I am missing something obvious, rds,

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shared_ptr and polymorphism
by Abderrahmane Madani 23 Feb '10

23 Feb '10

Just a little problem that I can't fix. Suppose that I have these four classes class B {}; class D1: public B {}; class D2: public B {}; class E: public D1 {}; this test: void foo(D1 *) {} void foo(D2 *) {} int main() { E *e = new E; foo(e); return 0; } work just fine but this one void foo(shared_ptr<D1>) {} void foo(shared_ptr<D2>) {} int main() { shared_ptr<E> e(new E); foo(e); return 0; } the compiler say that the foo(boost::shared_ptr<E>&)' is ambiguous. Please, can someone help me to understand why and how can I fix this problem without changing the functions name. Thanks Boost 1.35 GCC 4.4.1 regards

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[filesystem] wpath and fopen() on windows
by Paul 23 Feb '10

23 Feb '10

Hi, What is the best way for me to use boost::filesystem::wpath with a 3rd party C library that expects a const char* filename, on Windows? On linux, its simple: my_file.to_external_string() but on windows that gives me a wide-character string. So far the only thing I can think of is to roll my own wstring --> UTF8 conversion function, but I'm not even sure that is correct (will fopen() work with UTF-8 encoded filenames on windows?). thanks, Paul

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Optional XML serialization
by Paul 23 Feb '10

23 Feb '10

Hi, I use xml_woarchive and xml_wiarchive for reading/writing configuration files. It seems work work well for me, but now I'd like to see if I can do more with it... is it possible to load an XML serialized file, but completely IGNORE a subtree of the XML file if desired? eg template <class Archive> void load( Archive & ar, MyConfig & c, const unsigned int version ) { ar >> make_nvp("standard",c.standard); if (some_global_flag_or_whatever) ar >> make_nvp("advanced", c.advanced); else ar.skip("advanced"); // key bit } The motivation is that I want to "register modules" (in my app) that can read/write their configuration in an XML configuration file. But if the module is not registered, I want to skip that part of the configuration file and move on. I figure since the XML format is like a tree, it might/should be possible to ignore an entire segment of the tree. Is it possible? In a related note, the "class_id" bits in xml archives seems to make it difficult for users to hand-edit the XML file... Are these tags required? thanks, Paul

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asio newbie: picking a free port number
by Avi Bahra 23 Feb '10

23 Feb '10

I am writing a simple client/server program which will only run on Unix boxes (linux, HP-UX, AIX). By manually choosing the port number,everything works ok. Whenever I get an "Address in use" i choose a different number. I want to free clients of this program from having to do this. >From googling around it appears that there is way of the OS, to pick a free port number. i.e by binding to port 0, sock.bind(('', 0))/ sock.getsockname()[1] Is there any boost:asio recommended way of doing this ? Is there any way of completely abstracting out the use of port numbers from an end users perspective using boost asio ? i.e so that client/server agree on a free port number behind the scenes. Any help appreciated. Best regards, Ta, Avi

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[mpl] bind help sought
by Manfred Doudar 23 Feb '10

23 Feb '10

Hi, I need to be explicit about a function call, but unsure quite how to make it work, cut down example follows: struct M { static void foo() { ... } }; struct R { static void foo() { ... } }; struct Func { typedef void result_type; template <typename T, typename U> result_type operator()(U& u) const { T::foo(); // call on either M or R // do something with 'u' } }; int main(int argc, char** argv) { using namespace boost::mpl; typedef vector<M, R> vec; Func f; Object instance; for_each<vec>(boost::bind(&Func::operator()<XXX, Object>, boost::ref(f), instance) ); return 0; } Question is, what goes in at XXX above? I was thinking something along the lines of: boost::mpl::bind<boost::mpl::_1> ..but well, that doesn't work. All help appreciated. Cheers, -- Manfred

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[proto] Problem using BOOST_PROTO_AUTO
by Manjunath Kudlur 23 Feb '10

23 Feb '10

I have the following program to print out the arguments of a function call expression. It works fine when I directly call the grammar on the expression like so : foo_tostr()(f(a,b,c)). However, if I assign the expression to a variable pr using BOOST_PROTO_AUTO and call foo_tostr()(pr), I get error of the form "conversion from ‘boost::fusion::... to non-scalar type .... requested". Can someone let me know what I am doing wrong? #include <iostream> #include <boost/proto/proto.hpp> #include <boost/proto/proto_typeof.hpp> #include <sstream> #include <string> using namespace std; namespace proto = boost::proto; unsigned ids; struct var { unsigned id; var() { id = ++ids; } }; struct foo {}; typedef proto::terminal<var>::type Var; typedef proto::terminal<foo>::type Foo; struct _var_tostr : proto::callable { typedef string result_type; result_type operator()(var const &v) const { stringstream sout; sout << "v" << v.id << " "; return sout.str(); } result_type operator()(foo const &v) const { stringstream sout; sout << "foo("; return sout.str(); } }; struct var_tostr : proto::or_< proto::when<proto::terminal<var>, _var_tostr(proto::_value)> > {}; struct str_plus : std::plus<std::string>, proto::callable {}; struct foo_tostr : proto::or_ < proto::when<proto::function<proto::terminal<foo>, proto::vararg<proto::terminal<var> > >, proto::fold<proto::functional::pop_front(proto::_expr), string(), str_plus(proto::_state, var_tostr)> > > {}; int main() { Var a, b, c; Foo f; #define COPY_AND_PRINT #ifdef COPY_AND_PRINT BOOST_PROTO_AUTO(pr, (f(a,b,c))); cout << foo_tostr()(pr) << endl; #else cout << foo_tostr()(f(a,b,c)) << endl; #endif } -- Manjunath

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[proto] vararg expressions to string
by Manjunath Kudlur 23 Feb '10

23 Feb '10

I am trying understand the use of proto::fold to handle vararg expressions. As an experiment, I am trying to convert expressions of the form foo(a,b,c) to a string of the form "foo(a,b,c)". I currently have the following code where I treat the vararg expression as a fusion sequence and convert each parameter to a string using appropriate grammar. In the operator() of _foo_tostr, I have a case for each length of the vararg expression. Please let me know if there are better ways of doing this. #include <iostream> #include <boost/proto/proto.hpp> #include <boost/fusion/container/list/cons.hpp> #include <boost/fusion/include/cons.hpp> #include <boost/fusion/include/transform.hpp> #include <sstream> #include <string> using namespace std; namespace proto = boost::proto; namespace fusion = boost::fusion; unsigned ids; struct var { unsigned id; var() { id = ++ids; } }; struct foo {}; typedef proto::terminal<var>::type Var; typedef proto::terminal<foo>::type Foo; struct _var_tostr : proto::callable { typedef string result_type; result_type operator()(var const &v) const { stringstream sout; sout << "v" << v.id; return sout.str(); } }; struct var_tostr : proto::or_< proto::when<proto::terminal<var>, _var_tostr(proto::_value)> > {}; struct _foo_tostr : proto::callable { typedef string result_type; template<typename T> result_type operator()(T const &e) const { stringstream sout; sout << "foo("; if(fusion::size(e) == 1) { sout << ")"; } else if(fusion::size(e) == 2) { sout << var_tostr()(fusion::at_c<1>(e)) << ")"; } else if(fusion::size(e) == 3) { sout << var_tostr()(fusion::at_c<1>(e)) << ", " << var_tostr()(fusion::at_c<2>(e)) << ")"; } else if(fusion::size(e) == 4) { sout << var_tostr()(fusion::at_c<1>(e)) << ", " << var_tostr()(fusion::at_c<2>(e)) << ", " << var_tostr()(fusion::at_c<3>(e)) << ")"; } return sout.str(); } }; struct foo_tostr : proto::or_ < proto::when<proto::function<proto::terminal<foo>, proto::vararg<proto::terminal<var> > >, _foo_tostr(proto::_expr)> > {}; int main() { Var a, b, c; Foo f; cout << foo_tostr()(f(a,b,c)) << endl; }

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