February 2011 - Boost-users

Visual Studio 2010 Building Error
by Abdullah García 14 Feb '11

14 Feb '11

Hi, I have been working previously with Visual Studio 2008 and I haven't had any problem with my actual code. I needed to migrate my whole solution to Visual Studio 2010 and now I get the following error: - error C2664: 'boost::shared_ptr<T>::shared_ptr(boost::shared_ptr<T> &&)' : cannot convert parameter 1 from 'std::tr1::shared_ptr<_Ty>' to 'boost::shared_ptr<T> &&' Do you have any clue or advice on how to solve it? Greetings! -- Abdullah García

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TTI library updated in the sandbox to version 1.3
by Edward Diener 13 Feb '11

13 Feb '11

I have updated the TTI library in the sandbox 'tti' directory to version 1.3. The TTI library, which is an abbreviation for the 'Type Traits Introspection' library, allows a programmer to introspect at compile time the inner elements of a C++ type. The introspection process depends on specifying the name of the inner element by different macros for different types of elements, and then using a generated metafunction to determine whether that element exists within the enclosing type. The inner elements which can be introspected are type, class template, member data, member function, static member data, and static member function. With this update no functionality in the library has changed, but names have changed. The major change is that the library has been Boostified for possible review. 1) The update changes the library to use the Boost naming conventions. 2) The names of the main header files have been shortened and changed to 'tti.hpp' and 'tti_vm.hpp' respectively. 3) The macros in the library now start with BOOST_TTI. 4) The main namespace is now boost::tti. 5) Other filenames now follow Boost filename convention. 6) The documentation is distributed in both HTML and PDF format with indexes, and can be regenerated. 7) The variadic macro support in the library only works with the latest version 1.3+ of the variadic_maco_data library in the sandbox. The TTI library is based on the type_traits_ext portion of the Concept Traits Library, with improvements and additions, and also reproduces functionality ( without changing existing code ), for the purposes of completeness, from Boost.MPL regarding introspection of types and templates. The purpose of the library is to provide a consistent set of interfaces for doing compile-time introspection of a type, which other template metaprogrammers can use in their code. If you are at all interested in compile-time introspection of types, please take a look at the functionality of this library. There is a readme.txt in the top-level directory, for anyone browsing the sandbox. There is a build.txt file in the doc subdirectory for building the documentation and running the tests. The documentation is also included as part of the sandbox files for those who can not build the docs. The library has been tested and works with gcc 3.4.2, 3.4.5, 4.3.0, 4.4.0, 4.5.0-1, 4.5.2-1 and VC++ 8.0, 9.0, 10.0. It may also work with other compilers. Questions, comments, suggestions, and bug reports are all welcome.

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[asio] Run-time error with asio::streambuf
by Dylan Klomparens 13 Feb '11

13 Feb '11

I've experienced problems using asio::streambuf and am hoping someone can tell me if I'm using the class incorrectly. When I run this example code it segfaults. Why? To make things more confusing, this code works on Windows (Visual Studio 2008), but does not work on Linux (with gcc 4.4.1). -- Dylan #include <boost/asio.hpp> using namespace std; int main() { boost::asio::streambuf Stream; // Put 4 bytes into the streambuf... int SetValue = 0xaabbccdd; Stream.sputn(reinterpret_cast<const char*>(&SetValue), sizeof(SetValue)); // Consume 3 of the bytes... Stream.consume(3); cout << Stream.size() << endl; // should output 1 // Get the last byte... char GetValue; // -------------------------- The next line segfaults the program -------------------------- Stream.sgetn(reinterpret_cast<char*>(&GetValue), sizeof(GetValue)); cout << Stream.size() << endl; // should output 0 return 0; }

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Extra copy construction in boost::as_literal
by Sergey Nozhenko 13 Feb '11

13 Feb '11

Hi, Looking at the code generated by MSVC++ 2008 from a call to boost::algorithms::replace_all with std::wstrings as arguments I came across this remarkable piece of work: === cut === ; 109 : return range_detail::make_range( r, range_detail::is_char_ptr(r) ); xor eax, eax push -1 mov WORD PTR $T115029[esp+44], ax push eax mov eax, edi lea ecx, DWORD PTR $T115029[esp+44] mov DWORD PTR $T115029[esp+68], 7 mov DWORD PTR $T115029[esp+64], 0 call ?assign@?$basic_string@_WU?$char_traits@_W@std@@V?$allocator... cmp DWORD PTR $T115029[esp+60], 8 jb SHORT $LN52@as_literal mov ecx, DWORD PTR $T115029[esp+40] push ecx call ??3@YAXPAX@Z ; operator delete ... === cut === Checked it with g++ -O2 and found that it produced something similar: === cut === 109:.../boost/boost/range\as_literal.hpp **** return range_detail::make_range( r, range_detail::is_char_ptr(r) ); leal 168(%esp), %ebx movl %ebx, 4(%esp) leal 164(%esp), %eax movl %eax, (%esp) call __ZNSbIwSt11char_traitsIwESaIwEEC1ERKS2_ movl 168(%esp), %eax movl %eax, 44(%esp) movl -12(%eax), %edx movl %edx, 52(%esp) movl 164(%esp), %eax leal -12(%eax), %ebx cmpl $__ZNSbIwSt11char_traits..._Rep20_S_empty_rep_storageE, %ebx jne L412 L284: ... L412: movl 8(%ebx), %eax leal -1(%eax), %edx movl %edx, 8(%ebx) testl %eax, %eax jg L284 leal 188(%esp), %eax movl %eax, 4(%esp) movl %ebx, (%esp) call __ZNSbIwSt11char_traitsIwESaIwEE4_Rep10_M_destroyERKS1_ jmp L284 === cut === I.e., even with the optimization turned on, a call to "inline" function template< class T > inline long is_char_ptr( T /* r */ ) { return 0L; } in boost/range/as_literal.hpp causes the creation of a temporary copy of every string passed to boost::as_literal. :( I believe it would have been better to define that function as template< class T > inline long is_char_ptr(const T& /* r */ ) { return 0L; } Serge

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[graph] edge container for fast indexing by (bundled) property
by al.zatv 13 Feb '11

13 Feb '11

Hello! I have a question about Graph library. Let say I have a tree. Nodes of it are english letters. For example, A-->B-->X-->C, +-->A +-->D-->X I want to find sub-node of any node, by specifying the letter. Is it possible? For example, I'am in node B. And I want to find edge and node, by just saying "give me sub-node from B to the letter D". Looks like I have to write own EdgeContainer? Now I did it silly check every sub-node: *** typedef adjacency_list<listS,listS,bidirectionalS,NodeData> Lattice; typedef Lattice::vertex_descriptor VertexDesc; typedef Lattice::edge_descriptor EdgeDesc; std::tuple<bool,VertexDesc,EdgeDesc> get_sub_letter(const VertexDesc &n,char letter,const Lattice &lat) { auto outs=out_edges(n,lat); auto it=outs.first; for (;it!=outs.second;++it) { VertexDesc targetNode=target(*it,lat); if (lat[targetNode].letter==letter) return std::make_tuple(true,targetNode,*it); } return std::make_tuple(false,5,n,*it); } ***

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[fusion][docs] is_sequence *isnt* true for std::vector ?
by Martin Elzen 12 Feb '11

12 Feb '11

Hi all. I've been looking thru the documentation at boost.org to try to understand Boost.Spirit. That documentation refers to Boost.Fusion, and at http://www.boost.org/doc/libs/1_45_0/libs/fusion/doc/html/fusion/support/is… there's something I think needs clarification (at the very least), or is mistaken. The first line of the last paragraph of that page contains the following line:BOOST_MPL_ASSERT_NOT(( traits::is_sequence< std::vector<int> > )); I don't understand. How can a std::vector *not* be considered a sequence? Martin

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boost::iostreams output filter doesn't work
by John Hendrix 11 Feb '11

11 Feb '11

Hi all, I desire to use boost::iostream input and output filters. I cannot make the "Filter Usage Examples" (para2.2.2) shown here () to work. the following, as far as I can tell, is exactly the same "Ordinary OutputFilter" example shown at (http://tinyurl.com/45bur3o) struct toupper_filter { typedef char char_type; typedef boost::iostreams::output_filter_tag category; template<typename Sink> bool put(Sink& snk, char c) { return boost::iostreams::put(snk, toupper((unsigned char) c)); } }; the following code is modeled on the code at para2.2.2, "Filter Usage Examples": int main(int argc, char *argv[]) { // read my_input.txt and save uppercase version of text into datastore.txt std::ifstream pt_input; pt_input.open("my_input.txt"); std::ostringstream oss; oss << pt_input.rdbuf(); // oss now contains the text stored in input text boost::iostreams::filtering_ostream out_stream; // the following line is expected to transform the input text to uppercase. // instead it causes no text to appear in the output file. If the following line of // code is commented-out then contents of "my_input.txt" is placed in "datastore.txt". out_stream.push(toupper_filter()); out_stream.push(boost::iostreams::file_sink("datastore.txt")); out_stream.write( oss.str().c_str(), oss.str().length()); out_stream.flush(); } I am obviously doing not adding the toupper_filter into the filter chain correctly. Can anyone point out what I am doing wrong? many thanks

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Re: [Boost-users] Generating Multinomial Random Numbers
by Stephan Kitchovitch 11 Feb '11

11 Feb '11

Thanks Steven, > The binomial_distribution implementation in the current release is very slow for large n. > I've written a replacement that should be reasonably fast. It will be released in 1.47. Do you know for roughly what range of n the binomial_distribution provided becomes very slow? It would be useful to know whether computing for, say, n approx. 10 or 100 would be efficient. I need to generate from a multinomial for a stochastic simulation. n is unlikely to be very large, however this generation (as well as some based on the gamma distribution) will need to be done at every time step and thousands of simulations would need to be executed. For this reason I would like to make this generation step as efficient as possible. Will it be a while before version 1.47 is released? Cheers, Stephan

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Re: [Boost-users] [Serialization] Registering containers ofuser-provided types
by Vivek 11 Feb '11

11 Feb '11

Robert Ramey wrote: > The rub here is your requirement that it be exported through a base class pointer. That's exactly right. The library stores user-defined types and returns them to user code, but doesn't know what those types are ahead of time, hence the need to serialize via base pointers. As it is, the BOOST_EXPORT_* macros require I know the types even before compile time (i.e. at the time of writing the library code)... I basically need a way of registering the type at a point between when I've written the code and when it is compiled (which I guess only comes up as an issue for those writing libraries). That would be the way to do it. However, someone proposed a solution > to this problem and uploaded it as a track item. I found it intriguing, > But I decided not to implement it to keep the library from getting > any more complicated than it already is. You might want to > paste this proposed enhancement into your own code. Do you have a ticket number or link for this?

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Boost::Asio on ARMV5TE
by Peter Meyer 11 Feb '11

11 Feb '11

Hi, i've wrote a litte proxy using boost::asio (boost 1.45). Program runs well on Intel (Linux kernel 2.6.35.10 and gcc 4.5.1). Same code cross compiled for ARMV5TE (Linux 2.6.24.4 and GCC 4.1.2 or GCC 3.4.3) crashes always at the same point. Stacktrace looks like this Program terminated with signal 11, Segmentation fault. #0 0x400e3e20 in ?? () (gdb) backtrace #0 0x400e3e20 in ?? () #1 0x0001cfb0 in boost::asio::detail::posix_mutex::lock (this=0x7d) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/posix_mutex.hpp:52 #2 0x0001cfe6 in scoped_lock (this=0xbe8a98d0, m=@0x7d) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/scoped_lock.hpp:36 #3 0x00069bf4 in boost::asio::detail::epoll_reactor::run (this=0x191538, block=true, ops=@0xbe8a994c) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/impl/epoll_reactor.ipp:275 #4 0x0006a06c in boost::asio::detail::task_io_service::do_one (this=0x1914e0, lock=@0xbe8a99d4, this_idle_thread=0xbe8a9990) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/impl/task_io_service.ipp:264 #5 0x0006a33c in boost::asio::detail::task_io_service::run (this=0x1914e0, ec=@0xbe8a9a0c) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/detail/impl/task_io_service.ipp:130 #6 0x0006a426 in boost::asio::io_service::run (this=0xbe8a9bc4) at /usr/armv5tel-redhat-linux-gnueabi/sys-root/usr/local/include/boost/asio/impl/io_service.ipp:57 #7 0x00073504 in proxy::Server::run (this=0xbe8a9bb4) at server.cpp:71 #8 0x0004e2a4 in main (argc=3, argv=0xbe8a9da4) at proxy.cpp:111 It looks like the internal epoll_events data structure (descriptior_state) is corrupted. Any advice is welcome. With best regards Peter ------------------------------------------------------------------------------------

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