July 2008 - Boost-users - lists.boost.org

boost interprocess
by Marc Magrans de Abril 16 Jul '08

16 Jul '08

Dear colleagues, I have been testing the boost interprocess library for two months in my spare time... everything looked ok until now. Perhaps I am doing something wrong, so be patient. As you can see in the code, I am trying to use the offset_ptr within a class named OffsetPtrClass. However, if I try to allocate the int inside the OffsetPtrClass cnstructor I'll get a segmentation fault in the getter (either the MASTER or the SLAVE forked processes). I a running on Linux kernel 2.6.16 and g++ 3.4.xx. What I am doing wrong? Thanks for your help, marc #include <iostream> #include <unistd.h> #include <boost/interprocess/managed_shared_memory.hpp> #include <boost/interprocess/offset_ptr.hpp> namespace ip=boost::interprocess; class OffsetPtrClass { public: OffsetPtrClass():myint_(0) { //If we allocate the int here we get a segmentation fault!! // //ip::managed_shared_memory segment(ip::open_only,"MySharedSegment"); //myint_ = static_cast<int*>(segment.allocate(sizeof(int))); } ~OffsetPtrClass() { } void setMyint(const int& myint) { *myint_ = myint; } int getMyint() { int myint = *myint_; return myint; } ip::offset_ptr<int> myint_; }; int main( int argc, char* argv[] ) { std::string shName("MySharedSegment"); pid_t pid = fork(); if (pid == 0) { try { std::cout << "CHILD: getpid() = " << getpid() << std::endl; std::cout << "CHILD: press return to continue..." <<std::endl; getchar(); ip::managed_shared_memory segment(ip::open_only, shName.c_str()); std::cout << "CHILD: Retrieving OffsetPtrClass 'optr' instance: " << std::endl; std::pair<OffsetPtrClass*, std::size_t> res; res = segment.find<OffsetPtrClass> ("optr"); assert(res.second == 1); OffsetPtrClass& optr =*(res.first); std::cout << "CHILD: 'optr'::getMyint() = " << optr.getMyint() << std::endl; std::cout << "CHILD: 'optr'::SetMyint(100)" << std::endl; optr.setMyint(100); } catch (...) { std::cerr << "CHILD: Something failed..." << std::endl; throw; } } else if (pid <0){ std::cerr << "---program.cc: Failed to fork" << std::endl; exit(1); } else { std::cout << "PARENT: getpid() = " << getpid() << std::endl; ip::shared_memory_object::remove(shName.c_str()); try{ std::cout << "PARENT: creating segment" << std::endl; ip::managed_shared_memory segment(ip::create_only, shName.c_str(), 65536); std::cout << "PARENT: creating OffsetPtrClass 'optr' instance" << std::endl; OffsetPtrClass& optr = *(segment.construct<OffsetPtrClass>("optr")()); //If we allocate the int here we do not have a segmentation fault optr.myint_ = static_cast<int*>(segment.allocate(sizeof(int))); std::cout << "PARENT: 'optr'::SetMyint(333)" << std::endl; optr.setMyint(333); std::cout << "PARENT: 'optr'::getMyint() = " << optr.getMyint() << std::endl; std::cout << "PARENT: 'optr'::*myint_() = " << *(optr.myint_) << std::endl; std::cout << "PARENT: press return to continue..." <<std::endl; getchar(); std::cout << "PARENT: 'optr'::getMyint() = " << optr.getMyint() << std::endl; } catch(...){ std::cerr << "PARENT:something failed... Everything is destroyed" << std::endl; throw; } std::cout << "PARENT: Shared memory destroyed" << std::endl; } }

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Re: [Boost-users] Boost serialization: is there a way to perform selective read
by Pavlo Korzhyk 16 Jul '08

16 Jul '08

> It's not there. boost::archive works sequentially on a stream and that's > it, so if you need to skip large portions of data you will have to > divide your data into multiple files and/or multiple chunks in one > stream. I did the latter and it works fine if you build some kind of > meta-information structure on where chunks begin and end. This enables > you to seek a specific chunk of data and process that with an archive. > > In any case, if you want to improve performance of your app use > (portable) binary instead of xml archives! You could take a look at http://code.google.com/p/hiberlite It will do what you need storing objects in sqlite database. There were no new releases for a couple of months, but I'll return to this project in a week. And there are _already_ enough features to solve the "selective access" problem. Yours sincerely, Pavlo Korzhyk ICQ#155870780

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boost.program_options - passing string or vector<string>
by Aljaz 16 Jul '08

16 Jul '08

Hello I want to use boost.program_options to parse commands for my program (console application) What I want to do is to be able to pass std::vector<std::string> of arguments or std::string (line) to parse_command_line(ac, av, desc); instead of char *argv, int argc. How is that possible? I've been looking at basic_command_line_parser class but couldnt figure out how it would be possible to do that, since converting string/vector of strings to array of char pointers would be really stupid. Many thanks for help Aljaz

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SVN tree : Issue with libstdcpp3.hpp
by Mathieu Peyréga 16 Jul '08

16 Jul '08

Hello, starting from line 66, I can find : #if defined(__GLIBCXX__) || (defined(__GLIBCPP__) && __GLIBCPP__>=20020514) // GCC >= 3.1.0 # define BOOST_STD_EXTENSION_NAMESPACE __gnu_cxx # define BOOST_HAS_SLIST # define BOOST_HAS_HASH # define BOOST_SLIST_HEADER <ext/slist> # if defined(__GLIBCXX__) && __GLIBCXX__ < 20071018 // GCC <= 4.3.0 # define BOOST_HASH_SET_HEADER <ext/hash_set> # define BOOST_HASH_MAP_HEADER <ext/hash_map> # else # define BOOST_HASH_SET_HEADER <backward/hash_set> # define BOOST_HASH_MAP_HEADER <backward/hash_map> # endif #endif on ubuntu 8.04 (64 bits) the 4.2.3 gcc version define __GLIBCXX__ as #define __GLIBCXX__ 20080329 so boost code prevents from using the ext headers when the backward headre do not exist (on my system)... Shouldn't the < be a > ? regards, Mathieu -- http://www.incub.net/

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serialization - How to retain protected access of non-default ctors
by George Verdad 16 Jul '08

16 Jul '08

Hi All, I am getting compiler errors using mingw 3.4.5 on the code below: error: `BaseClass::BaseClass(const std::string&)' is protected I tried to declare as friend the load_construct_data() override in BaseClass but gave me the following error: error: call of overloaded load_constuct_data(..) is ambiguous. What am I doing wrong? TIA, Gvv ... #include <boost/serialization/base_object.hpp> #include <boost/serialization/export.hpp> #include <boost/serialization/shared_ptr.hpp> #include <boost/serialization/list.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> template <class T> void Serialize(const T& t, std::string& OutData) { std::ostringstream ArchiveStream; boost::archive::text_oarchive Archive(ArchiveStream); Archive << t; OutData = ArchiveStream.str(); } template <class T> void Deserialize(T& t, const std::string& InData) { std::istringstream ArchiveStream(InData); boost::archive::text_iarchive Archive(ArchiveStream); Archive >> t; } class BaseClass : private boost::noncopyable { public: virtual ~BaseClass() {} const std::string& GetName() const { return Name; } protected: BaseClass(const std::string& name) : Name(name) {} private: std::string Name; template<class Archive> void serialize(Archive& ar, const unsigned int version) { ar & Name; } friend class boost::serialization::access; }; typedef boost::shared_ptr<BaseClass> BaseClassPtr; class DerivedClass : public BaseClass { public: DerivedClass(const std::string& name) : BaseClass(name) {} private: template<class Archive> void serialize(Archive& ar, const unsigned int version) { ar & boost::serialization::base_object<BaseClass>(*this); } friend class boost::serialization::access; }; BOOST_CLASS_EXPORT(DerivedClass) namespace boost { namespace serialization { template<class Archive> inline void save_construct_data(Archive& ar, const BaseClass* t, const unsigned int version) { ar << t->GetName(); } template<class Archive> inline void load_construct_data(Archive& ar, BaseClass* t, const unsigned int version) { std::string name; ar >> name; ::new(t)BaseClass(name); } template<class Archive> inline void save_construct_data(Archive& ar, const DerivedClass* t, const unsigned int version) { ar << t->GetName(); } template<class Archive> inline void load_construct_data(Archive& ar, DerivedClass* t, const unsigned int version) { std::string name; ar >> name; ::new(t)DerivedClass(name); } } } int main() { BaseClassPtr b(new DerivedClass("My name is gvv")); std::string data; std::cout << "Serialize" << std::endl; Serialize(b,data); std::cout << data << std::endl; b.reset(); std::cout << "Deserialize" << std::endl; Deserialize(b,data); std::cout << b->GetName() << std::endl; return 0; }

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[preprocessor] BOOST_PP_IF with BOOST_PP_SEQ_ENUM as then-argument
by Maximilian Matthe 16 Jul '08

16 Jul '08

Hello! #define seq (int)(int) BOOST_PP_IF(1, BOOST_PP_SEQ_ENUM(seq), BOOST_PP_EMTPY) does not expand to what i want: it should be int, int . G++ gives the following error: test.cpp:20:1: macro "BOOST_PP_IIF" passed 4 arguments, but takes just 3 BOOST_PP_IIF which is logical, because SEQ_ENUM expands to int, int and so if gets 4 arguments. I tried to surround SEQ_ENUM with IDENTITY but it's the same problem. Only surrounding SEQ_ENUM with () works, but then I have the () in the code, which I do not want. How can I solve this problem? Max

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Basic Conversion to Boost Graph Library Data Structure
by Lex Fridman 16 Jul '08

16 Jul '08

I know that what I'm asking is in the documentation, but I haven't been able to figure it out from just looking through it on a couple passes. I would like to convert my graph adjacency list to the BGL adjacency_list. Each node is represented with the Node data structure, and so is each edge. I also have "global" properties for the graph as a whole. So here are the three data structures my graph uses: GraphNode { int foo; double bar; } GraphEdge { double weight; bool fun; } GraphGlobals { string graphName; } How do I declare an adjacency_list that will uses these representations of the node, edge, and global parameters? Thanks. -- View this message in context: http://www.nabble.com/Basic-Conversion-to-Boost-Graph-Library-Data-Structur… Sent from the Boost - Users mailing list archive at Nabble.com.

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Boost serialization: is there a way to perform selective read
by ari vol 16 Jul '08

16 Jul '08

Hey, I would like to know whether there is a way to preform selective read using Boost serialization, thus reading serialized instance with its id/key. The implementation that i know is saving instances to a file and then loading them all according to the saving order. Is there a way to read only one selected instance from the file. Thanks, -Ariella

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Facilities for view
by Peng Yu 16 Jul '08

16 Jul '08

Hi, I'm wondering if there is any facility to help define view in boost. There is view for static types http://www.boost.org/doc/libs/1_35_0/libs/fusion/doc/html/fusion/view.html. And there is a package to help define iterators http://www.boost.org/doc/libs/1_35_0/libs/iterator/doc/index.html. Due to the similarity between view and iterator, I'm wondering if there is a similar package for view? Thanks, Peng

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Beginner design question
by Hansi 16 Jul '08

16 Jul '08

Hello, I have to make a library which provides a few classes with different implementation. This classes should have a common interface. Normally I would use derived classes from the common interface, but this classes should be really fast. What is the best way to provide a common interface and to not have the overhead of polymorphic classes? Best regards Hansjörg

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