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

A question about "prim_minimum_spanning_tree.hpp"
by 王伟 06 Sep '10

06 Sep '10

Hi, I'm studying MST algorithms in GPU recently.I need BGL implementation as coparison,But I have a problem in using prim_minimum_spanning_tree.hpp.The problem is:when I use large input(e.g. >1M),there's a "segmnetation error" problem.But when the input(e.g. 1K) is small,the result is noproblem. I haven't found know the reason yet.My complier is gcc 4.1.2,OS is RHEL5. Help would be appreciated. Thanks in advance. Wang wei The complete code is in the attachment.

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cstdint.hpp on MSVC inconsitency ?
by joel falcou 05 Sep '10

05 Sep '10

In cstdint.hpp, the logic is that , if sizeof(long) == 4 then int32_t = long elseif sizeof(int) == 4 then int32_t = int. However, boost::detail::int_least_helper assumes sizeof(long) > sizeof(int). The consequence is that int_t<32>::fast is not the same as int32_t on MSVC while MSVC always garantee that int == long. Is there any rationale we missed or should I try to fix that as it currently prevent nT2 from compiling on MSVC . Regards

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How to disable the check or the error after checking for ICU (for regex lib) when building boost ?
by Timothy Madden 05 Sep '10

05 Sep '10

Hello I get the following message when compiling boost from trunk: 1>Building the Boost C++ Libraries. 1>has_icu_test.cpp 1>libs\regex\build\has_icu_test.cpp(12) : fatal error C1083: Cannot open include file: 'unicode/uversion.h': No such file or directory 1>Performing configuration checks 1> - has_icu builds : no Although the build succeeds (as this is a test) Visual Studio recognizes the error in the output and stops compiling the project and reports the build as failed. Is there a way for me to suppress this message ? Or this test ? Attempting to redirect output with &>outfile.txt do not work as the error messages still gets output in VS. Are there and build options to disable this check ? Thank you, Timothy Madden

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[BGL] Segmentation fault in clear_vertex
by Daniel Trebbien 02 Sep '10

02 Sep '10

I am attempting to modify my implementation of the Stoer–Wagner min-cut algorithm to modify the input graph. In the code sample below, t and s are vertex_descriptors that were calculated by a call to boost::detail::stoer_wagner_phase: boost::tie(s, t, w) = boost::detail::stoer_wagner_phase(g, assignments, weights, pq); assert(s != t); // ... std::multimap<vertex_descriptor, edge_descriptor> sOutEdges; BGL_FORALL_OUTEDGES_T(s, e, g, UndirectedGraph) { const vertex_descriptor u = target(e, g); if (t != u) { sOutEdges.insert(std::make_pair(u, e)); } } BGL_FORALL_OUTEDGES_T(t, e, g, UndirectedGraph) { const vertex_descriptor u = target(e, g); const weight_type eWeight = get(weights, e); typename std::multimap<vertex_descriptor, edge_descriptor>::iterator sOutEdgesIt, sOutEdgesEnd; boost::tie(sOutEdgesIt, sOutEdgesEnd) = sOutEdges.equal_range(u); if (sOutEdgesIt != sOutEdgesEnd) { for(; sOutEdgesIt != sOutEdgesEnd; ++sOutEdgesIt) { put(weights, sOutEdgesIt->second, get(weights, sOutEdgesIt->second) + eWeight); } } else if (t != u) { // need to update e to set the source to s edge_descriptor ePrime; boost::tie(ePrime, boost::tuples::ignore) = add_edge(s, u, g); put(weights, ePrime, eWeight); } } clear_vertex(t, g); The segmentation fault occurs in the call to clear_vertex, but does not occur if I comment out the line that adds an edge to the graph g. The type of g, by the way, is: boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS, boost::no_property, boost::property<boost::edge_weight_t, int> > Why does adding an edge between vertices s and target(e, g), both of which are not equal to t, cause a segmentation fault? For reference, gdb says that the fault occurs on line 999 of boost/graph/detail/adjacency_list.hpp: // O(E/V * E/V) template <class Config> inline void clear_vertex(typename Config::vertex_descriptor u, undirected_graph_helper<Config>& g_) { typedef typename Config::global_edgelist_selector EdgeListS; BOOST_STATIC_ASSERT((!is_same<EdgeListS, vecS>::value)); typedef typename Config::graph_type graph_type; typedef typename Config::edge_parallel_category Cat; graph_type& g = static_cast<graph_type&>(g_); typename Config::OutEdgeList& el = g.out_edge_list(u); typename Config::OutEdgeList::iterator ei = el.begin(), ei_end = el.end(); for (; ei != ei_end; ++ei) { detail::erase_from_incidence_list (g.out_edge_list((*ei).get_target()), u, Cat()); g.m_edges.erase((*ei).get_iter()); *// line 999* } g.out_edge_list(u).clear(); } Program received signal SIGSEGV, Segmentation fault. std::_List_node_base::unhook (this=0x3d7a38) at ../../../../gcc-4.4.0/libstdc++-v3/src/list.cc:134 134 ../../../../gcc-4.4.0/libstdc++-v3/src/list.cc: No such file or director y. in ../../../../gcc-4.4.0/libstdc++-v3/src/list.cc (gdb) bt #0 std::_List_node_base::unhook (this=0x3d7a38) at ../../../../gcc-4.4.0/libstdc++-v3/src/list.cc:134 #1 0x0045fa26 in std::list<boost::list_edge<unsigned int, boost::property<boost ::edge_weight_t, int, boost::no_property> >, std::allocator<boost::list_edge<uns igned int, boost::property<boost::edge_weight_t, int, boost::no_property> > > >: :_M_erase (this=0x22fa9c, __position=...) at c:/mingw/bin/../lib/gcc/mingw32/4.4.0/include/c++/bits/stl_list.h:1424 #2 0x0045fa0c in std::list<boost::list_edge<unsigned int, boost::property<boost ::edge_weight_t, int, boost::no_property> >, std::allocator<boost::list_edge<uns igned int, boost::property<boost::edge_weight_t, int, boost::no_property> > > >: :erase (this=0x22fa9c, __position=...) at c:/mingw/bin/../lib/gcc/mingw32/4.4.0/include/c++/bits/list.tcc:111 #3 0x00413ec9 in boost::clear_vertex<boost::detail::adj_list_gen<boost::adjacen cy_list<boost::listS, boost::vecS, boost::undirectedS, boost::no_property, boost ::property<boost::edge_weight_t, int, boost::no_property>, boost::no_property, b oost::listS>, boost::vecS, boost::listS, boost::undirectedS, boost::no_property, boost::property<boost::edge_weight_t, int, boost::no_property>, boost::no_prope rty, boost::listS>::config> (u=5, g_=...) at c:/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../../include/boost/graph/det ail/adjacency_list.hpp:999 #4 0x0041b0cc in boost::detail::stoer_wagner_min_cut<boost::adjacency_list<boos t::listS, boost::vecS, boost::undirectedS, boost::no_property, boost::property<b oost::edge_weight_t, int, boost::no_property>, boost::no_property, boost::listS> , boost::adj_list_edge_property_map<boost::undirected_tag, int, int&, unsigned i nt, boost::property<boost::edge_weight_t, int, boost::no_property>, boost::edge_ weight_t>, boost::associative_property_map<std::map<int, bool, std::less<int>, s td::allocator<std::pair<int const, bool> > > >, boost::shared_array_property_map <unsigned int, boost::vec_adj_list_vertex_id_map<boost::no_property, unsigned in t> >, boost::d_ary_heap_indirect<unsigned int, 4u, boost::shared_array_property_ map<unsigned int, boost::vec_adj_list_vertex_id_map<boost::no_property, unsigned int> >, boost::shared_array_property_map<int, boost::vec_adj_list_vertex_id_map <boost::no_property, unsigned int> >, std::greater<int>, std::vector<unsigned in t, std::allocator<unsigned int> > > > (g=..., weights=..., parities=..., assignments=..., pq=...) ...

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compressed fusion::vector?
by Cory Nelson 01 Sep '10

01 Sep '10

Hello, Is there a compressed fusion::vector that minimizes the size if the types passed in are empty, like compressed_pair? Thanks! -- Cory Nelson http://int64.org

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Using Boost.MPI with gather , data becomes overwritten after gather operation
by hgc-01134＠hkedcity.net wong 01 Sep '10

01 Sep '10

Hi, I am trying to use Boost.MPI to do a very simple program that 1. Processes from different ranks do a gather operation 2. The gather operation will gather the CoProcessInfo ( which is just a data structure of rank# and hostname) into a vector 3. After the gather operation, Rank 0 will print the CoProcessInfo one by one in the vector. ------------------------------------------------------------------------------------------------------------------------------------------------------ My testing environment consists of TWO virtual machine ( each of the machine has two cores ): Centos 5.5 mpich2 Boost.mpich2 Boost 1.41 mpiexec ------------------------------------------------------------------------------------------------------------------------------------------------------ The expected output of the program should be something like ( just an example order of ranks ): Host VM1, Rank 0 Host VM1, Rank 1 Host VM2, Rank 2 Host VM2, Rank 3 ---------------------------------------------------------------------------------------------------------------------------------------------------------- However, I got something like: ( just an example order of ranks ), the hostname is incorrect after gather operation ( three VM2 appears!) Host VM1, Rank 0 Host VM2, Rank 1 Host VM2, Rank 2 Host VM2, Rank 3 I found that each process CAN correctly found out the hostname and rank#, however, the data will become a bit like overwritten, after the gather operation. Thank you very much. ------------------------------------------- Source Code ------------------------------------------------------------------- #include <boost/asio/ip/host_name.hpp> #include <iostream> #include <vector> #include <string> #include <boost/mpi/environment.hpp> #include <boost/mpi/communicator.hpp> #include <boost/mpi.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <sstream> #include <fstream> using namespace std; namespace mpi = boost::mpi; class CoProcessInfo { private: string hostname; int rank; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int /* version */) { ar & hostname & rank; } public: CoProcessInfo() { hostname = boost::asio::ip::host_name(); rank = 0; } void setRank(int _rank) { rank = _rank; } string getHostname() const { return hostname; } int getRank() const { return rank; } }; int main(int argc, char* argv[]) { int myrank; mpi::environment env(argc, argv); mpi::communicator world; myrank = world.rank(); CoProcessInfo localInfo; localInfo.setRank( myrank ); std::vector<CoProcessInfo> coProcInfo; mpi::gather(world, localInfo, coProcInfo, 0); if( myrank == 0 ){ for (std::vector<CoProcessInfo>::const_iterator it = coProcInfo.begin(); it !=coProcInfo.end(); ++it) { cout << endl << " Host : " << it->getHostname() << " , Rank : " << it->getRank() << endl; } } return 0; } ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Regards, Joseph

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boost::addressof
by Stanisław Findeisen 31 Aug '10

31 Aug '10

Hi! In the latest boost release (1.44) boost::addressof is defined as follows (boost/utility/addressof.hpp): namespace detail { template<class T> struct addr_impl_ref { T & v_; inline addr_impl_ref( T & v ): v_( v ) {} inline operator T& () const { return v_; } private: addr_impl_ref & operator=(const addr_impl_ref &); }; template<class T> struct addressof_impl { static inline T * f( T & v, long ) { return reinterpret_cast<T*>( &const_cast<char&>(reinterpret_cast<const volatile char &>(v))); } static inline T * f( T * v, int ) { return v; } }; } // namespace detail template<class T> T * addressof( T & v ) { #if defined( __BORLANDC__ ) && BOOST_WORKAROUND( __BORLANDC__, BOOST_TESTED_AT( 0x610 ) ) return boost::detail::addressof_impl<T>::f( v, 0 ); #else return boost::detail::addressof_impl<T>::f( boost::detail::addr_impl_ref<T>( v ), 0 ); #endif } Q1: What is volatile in the cast needed for? Q2: Could anyone please explain to me what are the 2nd parameters in each of the f functions in struct addressof_impl for? Q3: What is struct addr_impl_ref::operator T& () const ??! I understand it is there to get called when passing addr_impl_ref<T>(v) instead of v to addressof_impl<T>::f, but I've never seen such a thing before. I would understand T& struct addr_impl_ref::operator(), or something, but this one is different. Sorry if this is a newbie question. Q4: I can see that in 1.34.1 boost::addressof was much more simple: // VC7 strips const from nested classes unless we add indirection here # if BOOST_WORKAROUND(BOOST_MSVC, == 1300) template<class T> struct _addp { typedef T * type; }; template <typename T> typename _addp<T>::type # else template <typename T> T* # endif addressof(T& v) { return reinterpret_cast<T*>( &const_cast<char&>(reinterpret_cast<const volatile char &>(v))); } so I wonder what was the problem with this design?... -- http://eisenbits.homelinux.net/~stf/ OpenPGP: DFD9 0146 3794 9CF6 17EA D63F DBF5 8AA8 3B31 FE8A Like Hardship, Risk & Challenge? --- Follow Jesus!!

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Creating a thread and blocking its execution
by Jean-Sebastien Stoezel 31 Aug '10

31 Aug '10

Hello, I use boost::thread as follow: mp_Thread = new boost::thread(boost::bind(CSubsystem::TaskWrapper, this)); to create a thread in an initialization method. I observe that this thread gets to run before my initialization method has completed its execution. I would like to create a thread from this initialization method, and wait for it to execute until the whole initialization process it done. Is it possible to create a thread in suspended mode, and then release it once the system is ready? Or do I need to use a synchronization mechanism like a semaphore to release it? Jean-Sebastien

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Does BOOST ASIO HTTP support 1.1
by Manna Patri 31 Aug '10

31 Aug '10

Hi, Looking at the boost::asio:: http server I am very much interested to have it in my application server.However before proceeding further I would like to know does HTTP server implmentation supports HTTP 1.1 ? Looking at the example available under HTTP client it seems "HTTP 1.0" is sent across in header as part of HTTP message. And to my curoisity when I modifeid the client code to send "HTTP 1.1" that also worked. Reply in this regard is appreciated. Thanks. Manna

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Re: [Boost-users] Boost.Serialization: Restoring object state(preventcreation of a new object)?
by ray＠maya-studio.com 31 Aug '10

31 Aug '10

> That's likely something else entirely. We'd have to see more code. Forget my previous post, the exception was due to mixed up ofstream and ifstream... Just to resume - if I have a list of pointers to the objects (all derived from the same base class) and I'd like to serialize them through a reference, a code like this would be needed: // List of pointers A a; B b; // Derived from A C c; // Derived from C std::list<A*> list; list.push_back(&a); // Base list.push_back(&b); // Derived list.push_back(&c); // Derived ... // Save std::ofstream ofs("c:/test.xml"); boost::archive::xml_oarchive oa(ofs); BOOST_FOREACH(A* pA, list) { if (dynamic_cast<B*>(pA)) { B& b = *static_cast<B*>(pA); oa & BOOST_SERIALIZATION_NVP(b); } else if (dynamic_cast<C*>(pA)) { C& c = *pA; BOOST_SERIALIZATION_NVP(c); } else { A& a = *pA; BOOST_SERIALIZATION_NVP(a); } } Am I right?

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multi_array: error: expected primary-expression before ‘)’
by Valmor de Almeida 31 Aug '10

31 Aug '10

Hello, I am trying from the multi_array web site doc: typedef boost::multi_array<double,3> array_type; array_type A(boost::extents[3][4][2],boost::fortran_storage_order); and getting the following compile-time error: g++ img2hermes2dmsh.cpp In function ‘int main()’: error: expected primary-expression before ‘)’ token Any insights? I am using boost-1.41 on gentoo linux. Thanks, -- Valmor

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download question
by Stanisław Findeisen 31 Aug '10

31 Aug '10

Hi What are the file checksums? -- http://eisenbits.homelinux.net/~stf/ OpenPGP: DFD9 0146 3794 9CF6 17EA D63F DBF5 8AA8 3B31 FE8A Like Hardship, Risk & Challenge? --- Follow Jesus!!

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Comparing boost bind object with a pointer to member function
by jej 31 Aug '10

31 Aug '10

Hello, Is is possible to compare a pointer to member function with a function object returned by boost bind? I have a class with several different functions; for each member function I use boost bind to bind the function object to several args. At the point where I want call the function object, I would like to check which member function it's been bound to, and decide whether or no it should be executed. For example, I would like the second comparison in the code snippet below to return "Bind match." For any other member function of foo it should return "Bind not match." Thanks. int main(int, char**) { Data d(1, 2); Foo fx, fy; //typedef void (Foo::*foofunctwo_t)(const Data&); //foofunctwo_t del1 = &Foo::FuncTwo; boost::function<void (Foo*, const Data&)> bf(&Foo::FuncTwo); if(bf == &Foo::FuncTwo) { cout << "match" <<endl; } else { cout << "no match" << endl; } boost::function<void (const Data&)> boundfunc = boost::bind(&Foo::FuncTwo, &fx, _1); if(boundfunc == &Foo::FuncTwo) { cout << "Bind match" << endl; } else { cout << "Bind not match" << endl; } return 0; }; -- View this message in context: http://old.nabble.com/Comparing-boost-bind-object-with-a-pointer-to-member-… Sent from the Boost - Users mailing list archive at Nabble.com.

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Overloading boost::for_each()
by Jeremiah Willcock 31 Aug '10

31 Aug '10

There are several container types (such as typical deque implementations, if you have access to their internals) that can have for_each() implemented for them in a way that is faster than using iterators and a generic for_each() function. Is there a way to take advantage of that in Boost.Range, such as by overloading boost::for_each()? Is there some kind of Iterable concept that doesn't require actual iterators or allows them to be slow? Would it be worthwhile to add one? Are there any other techniques that would be useful instead, such as always calling for_each() unqualified in my code and using ADL to find custom versions (like is done for swap)? I am not interested in making Boost.Range algorithms use this new concept, but there are places in my own code that could use for_each() rather than explicit loops if that was faster. Thank you for any answers or advice. -- Jeremiah Willcock

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asio HTTP client example always returns error 400
by G S 31 Aug '10

31 Aug '10

Hi all. I copied the boost::asio HTTP client example code: http://live.boost.org/doc/libs/1_39_0/doc/html/boost_asio/example/http/clie… and just replaced the argv stuff with a hard-coded domain name and "index.html". It appears to make the socket connection OK, but the response to the request is 400 ("bad request"). Is there something wrong with this request? boost::asio::streambuf request; std::ostream request_stream(&request); request_stream << "GET " << "index.html" << " HTTP/1.0\r\n"; request_stream << "Host: " << "musicobsession.com" << "\r\n"; request_stream << "Accept: */*\r\n"; request_stream << "Connection: close\r\n\r\n"; It doesn't matter what host I use (as long is it's real). Thanks for any insight!

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[log] cost of record instantiation
by Matthias Vallentin 31 Aug '10

31 Aug '10

Hello, I am trying to understand the cost of log record instantiation. Say I have a global severity logger with several levels, of which the debug level produces a lot of output and record creation is expensive. Because the overhead should only incur when actually logging in debug mode, I would like to know how costly the level check is. That is, in the following code // The custom logger class here accommodates multiple severity // loggers for different facilities. #define LOG(level, facility) \ BOOST_LOG_SEV(global::logger->get(facility), level) LOG(debug, core) << ... some expensive construction would the stream expression be instantiated regardless of the logging level, yet simple be discarded when being in level lower than debug? (I am asking because I recall they are not streamed in a lazy fashion.) If this is the case, preventing the construction of the stream expression would need a different logging mechanism, e.g., /// Expensive logging when in Debug mode. #ifdef DEBUG #define LOGD(facility) \ LOG(log::debug, facility) #endif // Not being compiled. LOGD(core) << ... some expensive constrution However, this design does not have a uniform approach to logging, which makes it less attractive. Any thoughts? Matthias

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[Boost.DateTime][Boost.Python] Year out of valid range error when streaming via Python module
by SamuelG 31 Aug '10

31 Aug '10

This problem occurs at a higher level but I've tried to strip it back. I've reproduced this problem GCC 4.3.4, Python 2.6.5 and Boost 1.41.0 32bit and 64bit Debians/Ubuntu. The problem does not seem to happen on Windows XP. I have embedded the Python interpreter in the attached http://old.nabble.com/file/p29579563/run_python.cpp run_python.cpp . When running this with the attached script http://old.nabble.com/file/p29579563/test.py test.py and which uses a test module http://old.nabble.com/file/p29579563/test_date_time.cpp test_date_time.cpp , the following Boost.DateTime error occurs: $ run_python test.py out() - entry out() - to_simple_string(): 2010-Aug-31 14:30:33.439172000 out() - manual format: 2010-Aug-31 14509:17:19.172000 out() - oss.str(): 2010-Aug-31 14509:17:19.172000 out() - now: Traceback (most recent call last): File "test.py", line 6, in <module> test_date_time.output() IndexError: Year is out of valid range: 1400..10000 However, when running the same script via python it is fine: $ python test.py out() - entry out() - to_simple_string(): 2010-Aug-31 14:30:31.208160000 out() - manual format: 2010-Aug-31 14:30:31.208160000 out() - oss.str(): 2010-Aug-31 14:30:31.208160000 out() - now: 2010-Aug-31 14:30:31.208160000 out() - exit Note that the time stamp in the first example is corrupt. Note also that the valid range error does not occur when using the date and time facets manually but when streaming the ptime object to std::cerr. The problem first arose for me when using Boost.Log with separate Python modules via *both* run_python and /usr/bin/python. See http://sourceforge.net/projects/boost-log/forums/forum/710022/topic/3748054 http://sourceforge.net/projects/boost-log/forums/forum/710022/topic/3748054 For this simple case, /usr/bin/python seems okay but the run_python error is identical to what happens in our proper application (where Boost.Log is used and multiple Python modules loaded). Has anyone witnessed similar behaviour? Or can they please test my example out? Thanks for any help, Sam -- View this message in context: http://old.nabble.com/-Boost.DateTime--Boost.Python--Year-out-of-valid-rang… Sent from the Boost - Users mailing list archive at Nabble.com.

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Re: [Boost-users] boost::asio SSL connection thru proxy server
by Kumar, Akhilesh 31 Aug '10

31 Aug '10

Hi All, Considering that nobody replied my question I am wondering if anybody who has knowledge of this kind of problem has seen my previous message/question. I really need help on this issue if anybody has any thought on this pls. reply. Thanks, Akhilesh Kumar From: Kumar, Akhilesh Sent: Monday, August 23, 2010 5:10 PM To: 'boost-users(a)lists.boost.org' Subject: boost::asio SSL connection thru proxy server Hi, I am writing a boost socket client using boost::asio to do secure HTTP (HTTPS) communication. I Implemented my client based on the code sample based on (http://www.boost.org/doc/libs/1_39_0/doc/html/boost_asio/example/ssl/client…) with little changes as I am using sync socket. My client woks fine, when I am connecting to server directly, but I am not sure what changes I need to make when my communication going thru proxy. The unsecure connection(HTTP) work fine thru proxy, and here is what I do for unsecure connection, 1. Initialize boost socket(IO service and other stuff). 2. Resolve and Connect to Proxy server. 3. Start writing to actual server(HTTP send request). 4. Start uploading/downloading. 5. Close Socket. But I can't use this above procedure for (SSL) secure connection as I need to do handshaking with the server before I can write anything if my understanding is correct. Can somebody give me some pointer or code sample or step I need to do when I am doing secure connection thru proxy server. Just to clarify Microsoft WinInet does do (secure) HTTPS connection thru same proxy fine. If providing my code sample I am using for SSL might help understand the problem I can provide that. Thanks in advance for any help. Akhilesh Kumar

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Re: [Boost-users] Boost.Serialization: Restoring object state (preventcreation of a new object)?
by ray＠maya-studio.com 30 Aug '10

30 Aug '10

>> Just avoid serialization through a pointer, serialize either the >> object or a reference to the object. Thanks, Robert. Serializing through a reference seems to be the only viable solution in my case. However, I'm not able to make it work (I didn't find any specific information about references in the library documentation - except for member variables) . For example: A a; ... A& aRef = a; ia & BOOST_SERIALIZATION_NVP(aRef);; // Throws an exception in load_override

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[parameter] Using named parameter types in return type
by Jeremiah Willcock 30 Aug '10

30 Aug '10

In BOOST_PARAMETER_FUNCTION, one argument to specify is the return type of the function. How do I refer to the types deduced for the named parameters in the return type? I am creating a factory function for a class template (similar to std::make_pair) and would like to use named parameters for it. I did not see any obvious way to do this in the documentation. Is there a way? A documented name for the ArgPack? I am using C++0x so it would be OK to have a solution that requires that. -- Jeremiah Willcock

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Re: [Boost-users] [filesystem] Using filesystem library from Boost version 1.44 on Cygwin 1.7
by Clarke, Carus V 30 Aug '10

30 Aug '10

> Date: Mon, 30 Aug 2010 08:36:49 -0700 > From: Steven Watanabe <watanabesj(a)gmail.com> > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] [filesystem] Using filesystem library from > Boost version 1.44 on Cygwin 1.7 > Message-ID: <4C7BD011.6010707(a)providere-consulting.com> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > AMDG > > Clarke, Carus V wrote: > > Steven Watanabe wrote: > >> Your code doesn't appear to print this last line. > > > > You are right. I added the last line after pasting in the > code. Here it is: > > > > boost_fs::file_status st = boost_fs::status(path, ec); > > <snip> > > std::cout << "Does file exist? " << boost_fs::exists(st) > << std::endl; > > return 0; > > } > > > > Is there anything I can do to make this work? > > > > It looks like stat is setting errno to ENOENT. > Do you get the same behavior if the file exists before > starting the program? > > In Christ, > Steven Watanabe > Yes, the behavior is the same whether the program writes the file or if the file had been previously written. Thanks, Carus V. (Bud) Clarke carus.v.clarke(a)boeing.com

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Boost.Serialization: Restoring object state (prevent creation of a new object)?
by ray＠maya-studio.com 30 Aug '10

30 Aug '10

If an object is serialized (saved) from a pointer, the loading part automatically creates (instantiates) a new object. However, there are situations when the object is already created and all we need is to restore its state. The following code demonstrates one possible - although not elegant - solution using a temporary object:#include <fstream> #include <iostream> #include <boost/archive/xml_iarchive.hpp> #include <boost/archive/xml_oarchive.hpp> #include <boost/serialization/string.hpp> #include <boost/serialization/export.hpp> class A { public: A() : m_val(100) { } int m_val; private: friend class boost::serialization::access; template <typename Archive> void serialize(Archive &ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(m_val); } }; int main(int argc, char* argv[]) { A *a = new A(); // Save the object { std::ofstream os("d:/test.xml"); boost::archive::xml_oarchive oa(os); // Save from pointer oa & BOOST_SERIALIZATION_NVP(a); } // Change the object state a->m_val = 200; // Restore the state { std::ifstream is("d:/test.xml"); boost::archive::xml_iarchive ia(is); A* aTemp; ia & BOOST_SERIALIZATION_NVP(aTemp); a->m_val = aTemp->m_val; // Copy object state assert(a->m_val == 100); delete aTemp; } } Here is my question: Is there some more convenient way to restore the object state? In other words, is it possible to prevent creation of a new object and just 'populate' an existing object?

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[filesystem] Using filesystem library from Boost version 1.44 on Cygwin 1.7
by Clarke, Carus V 30 Aug '10

30 Aug '10

Date: Fri, 27 Aug 2010 15:39:29 -0700 From: Steven Watanabe <watanabesj(a)gmail.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [filesystem] Using filesystem library from Boost version 1.44 on Cygwin 1.7 Message-ID: <4C783EA1.4070400(a)providere-consulting.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed AMDG Clarke, Carus V wrote: > I have been using the filesystem library from Boost version 1.43 on a Cygwin 1.7.6-1 platform without any problems. The library was built using the Cygwin version of GCC 4.3.4. The library from the 1.44 version of Boost compiles compiles o.k., but the functions that access files no longer work. This appears to be true for both versions 2 and 3 of the library. Below is a simple program that runs o.k. with the Boost version 1.43 version of the library. The program runs but can not read the file status using Boost version 1.44. This program also works fine when built using MSVC 9.0 and Boost version 1.44. > > //-------------------- > > <snip> > > int main() > { > <snip> > std::cout << "Error code message: " << ec.message() << std::endl; > return 0; > } > > //-------------------- > > This program's output on my system is shown below. The file 'foo' is written by the program and does actually exist. > > For version 2: > > boost::filesystem library version is v2 > Checking status of file foo... > Error code value: 0 > Error code message: The operation completed successfully > Does file exist? false > Your code doesn't appear to print this last line. In Christ, Steven Watanabe ------------------------------ You are right. I added the last line after pasting in the code. Here it is: boost_fs::file_status st = boost_fs::status(path, ec); <snip> std::cout << "Does file exist? " << boost_fs::exists(st) << std::endl; return 0; } Is there anything I can do to make this work? Thanks, Carus V. (Bud) Clarke carus.v.clarke(a)boeing.com ------------------------------

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[parameter] Weird behavior with bools
by Ryan McConnehey 30 Aug '10

30 Aug '10

I'm new to the parameter library and started with a simple example to get my feet wet. The first problem I'm having is with type restriction. The "name" variable is being restricted to a boolean type. This doesn't seem to be enforced since I can pass this variable a value of 15 and get this same value out. Currently my output has "name = 15" and I expected the output to be "name = 1". Did I not correctly enforce the type? The second problem is with the default value of my variable. I thought if the variable wasn't used then the third parameter, in the declaration, is used for instantiation of that variable. I thought that meant I could do this "m_name(args[_name])". The compiler gives an error saying the operator[] can't deduce the arguments. What did I not do that would allow this behavior. Thank you for your time in helping me out. Ryan BOOST_PARAMETER_NAME(name) struct myclass_impl { template <class ArgumentPack> myclass_impl(ArgumentPack const& args) : m_name(args[_name | false]) //: m_name(args[_name]) //gives a compile error { std::cout << "name = " << m_name << std::endl; } private: int m_name; }; struct myclass : public myclass_impl { BOOST_PARAMETER_CONSTRUCTOR( myclass, (myclass_impl), tag , (optional (name, (bool), bool(false)))) // no semicolon }; int main(int argc, char* argv[]) { myclass x(_name = 15); return 0; }

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Can I fstat or get the file date/time for a file stream ?
by Timothy Madden 30 Aug '10

30 Aug '10

Hello Is there a way to stat or to get file last accessed time from an opened std::fstream or boost::filesystem::fstream or a boost::iostreams::stream ? Or is there a way to get the underlaying file descriptor (or a FILE *) from a fstream so I can call POSIX fstat ? Thank you, Timothy Madden

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