May 2012 - Boost-users - lists.preview.boost.org

[asio] documentation example, bind semantics
by John M. Dlugosz 03 May '12

03 May '12

In boost_asio/tutorial/tutdaytime3.html, the code shown is: void handle_accept(tcp_connection::pointer new_connection, const boost::system::error_code& error) { and is called via a function object: boost::bind(&tcp_server::handle_accept, this, new_connection, boost::asio::placeholders::error) I get after my coworkers I'm mentoring in the area of C++ skills to pass smart pointers by const-ref not by value, since the atomic inc/dec is very costly. I believe that a boost::function (and now std::function) will hold the object by value even if the function being bound declares it as reference, and the INVOKE phase will bind the parameter to the stored copy in the function object. So handle_accept can and should be declared as using a const tcp_connection::pointer& as well, right? Is there any reason not to? —John

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[Boost.Integer] On Win32, boost::uint_t<65>::fast has 64 bits?
by Scott Meyers 03 May '12

03 May '12

The type yielded by boost::uint_t<N>::fast seems pretty clear: "The easiest-to-manipulate, built-in, unsigned integral type with at least N bits." But when I run the following program, which prints the number of bits in the type returned by boost::uint_t<65>::fast (i.e., a type with at least 65 bits), I get 64. #include <iostream> #include <climits> #include <boost/integer.hpp> int main() { std::cout << "boost::uint_t<65>::fast has " << CHAR_BIT * sizeof(boost::uint_t<65>::fast) << " bits\n"; } I get the same results with VC10, VC11 beta, and gcc 4.7 on Win32 with Boost 1.49. I must be doing something wrong, right? But what? Thanks, Scott

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Fusion warning cleanup
by Belcourt, Kenneth 03 May '12

03 May '12

Hi, Could these (and other) auto generated headers be emitted so they don't trigger these sorts of warnings? We get these warnings with multiple compilers. Thanks. -- Noel Belcourt CC-1 crayc++: WARNING File = /scratch1/kbelco/boost/boost/status/../boost/fusion/tuple/detail/preprocessed/tuple_fwd.hpp, Line = 21 The source file does not end with a new-line character. #endif ^ CC-1 crayc++: WARNING File = /scratch1/kbelco/boost/boost/status/../boost/fusion/tuple/detail/preprocessed/make_tuple.hpp, Line = 21 The source file does not end with a new-line character. #endif ^ CC-1 crayc++: WARNING File = /scratch1/kbelco/boost/boost/status/../boost/fusion/tuple/detail/preprocessed/tuple_tie.hpp, Line = 21 The source file does not end with a new-line character. #endif ^

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[Range] Predicate type checking.
by Robert Jones 02 May '12

02 May '12

I'm pretty sure I'm have a 'Doh!' moment here, but why does this compile? Surely the last line of main is gibberish; the value type of m is pair, not S, so int_from_S is not a valid function? #include <boost/range.hpp> #include <boost/range/adaptor/transformed.hpp> #include <map> struct S { S( ) { } int i; }; int int_from_S( S s ) { return s.i; } int main( ) { std::map<unsigned, S> m; m[0]=S(); m | boost::adaptors::transformed(int_from_S); } Thx, - Rob.

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config. how to check if std::shared_ptr & std::scoped_ptr availability?
by niXman 02 May '12

02 May '12

Hello! I need to check if std::shred_ptr & std::scoped_ptr availability. I read boost.config and found: http://www.boost.org/doc/libs/1_49_0/libs/config/doc/html/boost_config/boos… But in this list don't exist macro that I need. Ideas? Thanks. -- Regards, niXman

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multiarray sub_array
by Petros 01 May '12

01 May '12

Hi, I want to be able to create an array view on a subset of a multi_array(MA)’s dimensions. So, say I have a MA of dimension M and I want to choose N (N <M) dimensions of it which I put on a boost::array. Say, I want to keep the entire range for each dimension. Is there a way to do this in a general fashion, i.e. w/out the use of the subscript operator on the indices object ? The documentation mentions something like : typedef boost::multi_array< double, 3 > Grid3D; typedef Grid3D::size_type size_type; typedef Grid3D::index index; typedef Grid3D::index_range index_range; typedef Grid3D::array_view<2>::type Slice2D; index_range r1; //( 0, iMax); index_range r3; //( 0, kMax); Grid3D::index_gen indices; Slice2D sliceJ2 = grid[indices [r1] [2] [r3] ]; but this is not sufficient for a generic construction. And also, what is the difference between array_view and subarray ? Thank you very much in advance, Petros

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fatal error C1001 with VS2010, boost 1.49, and shared_ptr.hpp
by Phillip Hellewell 01 May '12

01 May '12

I'm upgrading to boost 1.49 and getting this fatal error while compiling a source file that uses shared_ptr: 1>C:\mycomps\base\target\dependency\include\boost/smart_ptr/shared_ptr.hpp(362): fatal error C1001: An internal error has occurred in the compiler. 1> (compiler file 'msc1.cpp', line 1420) 1> To work around this problem, try simplifying or changing the program near the locations listed above. 1> Please choose the Technical Support command on the Visual C++ 1> Help menu, or open the Technical Support help file for more information Line 362 of shared_ptr.hpp is: shared_ptr( shared_ptr<Y> && r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() ) Looks like the compiler is crashing with an access violation; any suggestions other than wait for a patch from Microsoft? I don't want to have to disable features like BOOST_HAS_RVALUE_REFS or BOOST_SP_NO_SP_CONVERTIBLE, but that may be my only choice :( Thanks, Phillip

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async_read_some
by Christer Borgqvist 01 May '12

01 May '12

Hi, Im playing around with the /boost_asio/example/http/server3 and using POST method. The bytes_transferred is 231, but thats only the header and ends with \r\n\r\n, need to read the rest. Sometimes i get bytes_transferred to 1032, the right amount of data, sometimes i get bytes_transferred = 231, but if i print the buffer_ i have all the 1032 bytes. Is it right that the bytes in the buffer_ and the bytes_transferred is not the same? appreciate any help. /christer void connection::handle_read(const boost::system::error_code& e, std::size_t bytes_transferred) { if (!e) { boost::tribool result; boost::tie(result, boost::tuples::ignore) = request_parser_.parse( request_, buffer_.data(), buffer_.data() + bytes_transferred); if (result) { request_handler_.handle_request(request_, reply_); boost::asio::async_write(socket_, reply_.to_buffers(), strand_.wrap( boost::bind(&connection::handle_write, shared_from_this(), boost::asio::placeholders::error))); } else if (!result) { reply_ = reply::stock_reply(reply::bad_request); boost::asio::async_write(socket_, reply_.to_buffers(), strand_.wrap( boost::bind(&connection::handle_write, shared_from_this(), boost::asio::placeholders::error))); } else { socket_.async_read_some(boost::asio::buffer(buffer_), strand_.wrap( boost::bind(&connection::handle_read, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred))); } }

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Use boost::shared_ptr with boost::adaptors
by tolik levchik 01 May '12

01 May '12

The following code gives me segfault. But if `foo_ptr` is `foo*` it works fine. #include <vector> #include <boost/range/adaptor/indirected.hpp> #include <boost/range/adaptor/transformed.hpp> #include <boost/range/algorithm/for_each.hpp> #include <boost/bind.hpp> #include <boost/shared_ptr.hpp> struct foo{ foo(int _i): i(_i){} virtual void bar() const{ std::cout << "foo::bar::i " << i << std::endl; } int i; }; typedef boost::shared_ptr<foo> foo_ptr; //typedef foo* foo_ptr; foo_ptr trasform(int i){ return foo_ptr(new foo(i)); } int main(){ std::vector<int> vec; vec.push_back(1); using namespace boost::adaptors; using boost::bind; boost::for_each(vec | transformed(bind(&trasform, _1)) | indirected, bind(&foo::bar, _1)); } Is it expected behavior of adaptors ?

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