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Compile errors with boost::mpl::if on MinGW/Msys
by Kevin Jenkins 03 Sep '08

03 Sep '08

Hi, I'm trying to use typedef typename boost::mpl::if_ to choose between two structures, both with identical function names, so I can choose which function to call based on the template parameter type. The code works fine on Visual Studio 2005. But in MinGW/MSys it returns: RPC3_Boost.h:203: error: template argument 2 is invalid RPC3_Boost.h:203: error: template argument 3 is invalid RPC3_Boost.h:203: error: ISO C++ forbids declaration of `type' with no type This is with boost_1_35_0. I've cut out as much code as I can: struct ReadBitstream { static void apply(RakNet::BitStream &bitStream, RakNet::BitStream* t) {/* ... */} }; template <typename T> struct ReadPtr { static inline void apply(RakNet::BitStream &bitStream, const char *&t) {applyStr(bitStream, (char *&) t);} }; template< typename T > struct DoRead { typedef typename boost::mpl::if_< boost::is_convertible<T*,RakNet::BitStream*>, typename ReadBitstream, typename ReadPtr<T> >::type type; }; To call the function, I use: DoRead< boost::remove_pointer<T>::type >::type::apply(* (args.bitStream),&t); Thanks in advance for any help. The whole file is here if you need to see more code: https://raknetjenkinsso.svn.sourceforge.net/svnroot/raknetjenkinsso/trunk/D…

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set help
by Kurt Kohler 03 Sep '08

03 Sep '08

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[Serialization] binary archive 1.75 times larger than source data
by Sebastian.Karlsson＠mmorpgs.org 03 Sep '08

03 Sep '08

Hi, So I've got most of my serialization working now, the only problem now is that it's still largely inefficent. The resulting binary file is 1.75 times larger than the sourcer XML file which I parse from. This is probably a lot due to the fact that I still default tracking and version everything. What I'd love to do however is to specify on a archive by archive basis if I want tracking / versioning. In fact, isn't this what one would normally want to do? When you specify tracking on a class by class basis you have no idea if there will be multiple pointer to the same object of that type. I found the no_tracking which I found a reference to from 2006 on this very mailing list, however it still doesn't seem to affect at least archive size ( haven't checked deserialization timings for it ). When I take a look at the deserialization the binary archive seems to store identifiers for types as their straight up string versions. This also seems largely inefficient, is there a reason for why this can't just be a hash? Also, is binary archives streaming or do they wait until the entire archive is loaded? Basically I'm wondering what would be the fastest possible archive one could create if one doesn't care about portability. // Sebastian Karlsson

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boost::filesystem: removing directory recursively?
by Ákos Maróy 03 Sep '08

03 Sep '08

Is there an easy / elegant way to remove directory contents recursively using boost::filesystem? I see that there's a create_directories() convenience function, but there's no such convenience function for removing a directory and all its contents. moreover, recursive_directory_iterator() does not return an iterator that contains the directory contens in the order suitable for removal :( I wonder if there's an easy / elegant way to do this? Akos

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[bind] [lambda] making lambda::bind work
by Peter Barker 03 Sep '08

03 Sep '08

Hello, I've got some code that works ok with boost::bind and I'm trying to make it work with lambda::bind but am getting compilation errors. Why not leave it as-is? Just above the problem area of code I have another lambda expression and because I've already introduced lambda's _1 placeholder into the current scope and didn't want ambiguities arising so want to convert it over. I'm using VC++ 7.1 (2003) and Boost 1.35.0. I've created a stripped down test program to show the compilation problem: #include <algorithm> #include <memory> #include <string> #include <vector> #include <boost/bind.hpp> #include <boost/utility.hpp> #include <boost/lambda/bind.hpp> #include <boost/lambda/lambda.hpp> class GridItem : boost::noncopyable { public: bool AddOption(const char* item,bool unique = true) { // implementation code omitted! return true; } }; void GoodOldBoostBind() { std::auto_ptr<GridItem> item(new GridItem()); std::vector<std::string> options; std::for_each(options.begin(),options.end(), boost::bind(GridItem::AddOption,boost::ref(item),boost::bind(std::string::c_str,_1),true)); } void LambdaBind() { std::auto_ptr<GridItem> item(new GridItem()); std::vector<std::string> options; using namespace boost::lambda; using boost::lambda::_1; std::for_each(options.begin(),options.end(), bind(GridItem::AddOption,boost::ref(item),bind(std::string::c_str,_1),true)); // COMPILE ERROR ON ABOVE } int main() { } The error is: c:\releases\lib\boost\boost_1_35_0\include\boost\bind.hpp(338) : error C2664: 'R boost::_mfi::mf2<R,T,A1,A2>::operator ()<std::auto_ptr<_Ty>>(const U &,A1,A2) const' : cannot convert parameter 2 from 'boost::lambda::lambda_functor<T>' to 'const char *' with [ R=bool, T=GridItem, A1=const char *, A2=bool, _Ty=GridItem, U=std::auto_ptr<GridItem> ] and [ T=boost::lambda::lambda_functor_base<boost::lambda::action<2,boost::lambda::function_action<2>>,boost::tuples::tuple<const boost::lambda::detail::bind_traits<const char *(__thiscall std::basic_string<char,std::char_traits<char>,std::allocator<char>>::* const )(void) const>::type,const boost::lambda::detail::bind_traits<const boost::lambda::placeholder1_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type>> ] No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called Can anyone help with this? Thanks, Pete

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boost::regex problem
by Silvio Reis Junior 03 Sep '08

03 Sep '08

Hello folks! I'm trying to work with boost::regex but I'm stuck. I wrote the following code: //------------------------------------------------------------------- int main( int argc, CHAR* argv[] ) { boost::regex RegEx( "(eth\\d)" ); if ( boost::regex_match( "dsjkadhjksadjks eth1: ssgdsdhjasgdjg", RegEx ) ) { printf( "Found.\n" ); } return 0; } I tested the expression with Expresso and it's correct although it doesn't work in the code above. Is there something missing? My best regards Silvio

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[boost.asio] string iterator not dereferencable using message in async_send_to
by John Urberg 03 Sep '08

03 Sep '08

I'm using async_send_to to send multicast messages. When I try to send data in a std::string, I always get a 'string iterator not dereferencable' assertion failure. I'm using boost 1.35 and VC9. Here's the code: // instance variable string buffer; // code in method buffer = BuildHailMessage(); socket.async_send_to( boost::asio::buffer(buffer), endpoint, boost::bind( &MulticastServer::HandleSendTo, this, boost::asio::placeholders::error)); I've also tried using char* buffer, dynamically allocating it based on the message length and then use std::copy to copy the std::string into the buffer, but I get heap corruption assertions when trying to delete [] it. The only way I've gotten this to work is using a fixed char[] buffer. Is there a way I can use a std::string with async_send_to? Do I need to use a different type of asio::buffer class? Thanks, John

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Function pointers vs boost.function
by Kurt Kohler 03 Sep '08

03 Sep '08

I have some code that uses pointers to member functions (not boost.function). It compiles and works fine. But when I tried to convert the code to use boost.function, I got a mess of errors. I know I'm doing something wrong, but I have no idea what it is. A clue would be greatly appreciated. Here's a reduced test case. #include <boost/function.hpp> struct X { double f(double x) { return x; } double g(double x) { return -x; } //typedef boost::function<double (double)> ftype; typedef double (X::*ftype)(double); double call(ftype func, double x) { //return func(x); return (this->*func)(x); } }; int main(int argc, char *argv[]) { X x; x.call(&X::f, 1.0); // Error occurs here x.call(&X::g, 2.0); } It compiles as it appears above, but if I switch the typedef and return statements to their commented versions, I get the following errors: if g++ -DHAVE_CONFIG_H -I. -I/home/kohler/Projects/test/trunk/src -I.. -O0 -Wall -g3 -MT test.0 -MD -MP -MF ".deps/test.Tpo" -c -o test.o /home/kohler/Projects/test/trunk/src/test.cpp; then mv -f ".deps/test.Tpo" ".deps/test.Po"; else rm -f ".deps/test.Tpo"; exit 1; fi /usr/include/boost/function/function_template.hpp: In static member function 'static R boost::detail::function::function_obj_invoker1<FunctionObj, R, T0>::invoke(boost::detail::function::function_buffer&, T0) [with FunctionObj = boost::_mfi::mf1<double, X, double>, R = double, T0 = double]': /usr/include/boost/function/function_template.hpp:368: instantiated from 'void boost::detail::function::basic_vtable1<R, T0, Allocator>::init(FunctionObj, boost::detail::function::function_obj_tag) [with FunctionObj = boost::_mfi::mf1<double, X, double>, R = double, T0 = double, Allocator = std::allocator<void>]' /usr/include/boost/function/function_template.hpp:298: instantiated from 'void boost::detail::function::basic_vtable1<R, T0, Allocator>::init(F) [with F = boost::_mfi::mf1<double, X, double>, R = double, T0 = double, Allocator = std::allocator<void>]' /usr/include/boost/function/function_template.hpp:339: instantiated from 'void boost::detail::function::basic_vtable1<R, T0, Allocator>::init(MemberPtr, boost::detail::function::member_ptr_tag) [with MemberPtr = double (X::*)(double), R = double, T0 = double, Allocator = std::allocator<void>]' /usr/include/boost/function/function_template.hpp:298: instantiated from 'void boost::detail::function::basic_vtable1<R, T0, Allocator>::init(F) [with F = double (X::*)(double), R = double, T0 = double, Allocator = std::allocator<void>]' /usr/include/boost/function/function_template.hpp:277: instantiated from 'boost::detail::function::basic_vtable1<R, T0, Allocator>::basic_vtable1(F) [with F = double (X::*)(double), R = double, T0 = double, Allocator = std::allocator<void>]' /usr/include/boost/function/function_template.hpp:655: instantiated from 'void boost::function1<R, T0, Allocator>::assign_to(Functor) [with Functor = double (X::*)(double), R = double, T0 = double, Allocator = std::allocator<void>]' /usr/include/boost/function/function_template.hpp:513: instantiated from 'boost::function1<R, T0, Allocator>::function1(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type) [with Functor = double (X::*)(double), R = double, T0 = double, Allocator = std::allocator<void>]' /usr/include/boost/function/function_template.hpp:753: instantiated from 'boost::function<R ()(T0), Allocator>::function(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type) [with Functor = double (X::*)(double), R = double, T0 = double, Allocator = std::allocator<void>]' /home/kohler/Projects/test/trunk/src/test.cpp:21: instantiated from here /usr/include/boost/function/function_template.hpp:134: error: no match for call to '(boost::_mfi::mf1<double, X, double>) (double&)' /usr/include/boost/bind/mem_fn_template.hpp:160: note: candidates are: R boost::_mfi::mf1<R, T, A1>::operator()(T*, A1) const [with R = double, T = X, A1 = double] /usr/include/boost/bind/mem_fn_template.hpp:179: note: R boost::_mfi::mf1<R, T, A1>::operator()(T&, A1) const [with R = double, T = X, A1 = double] g++ -v Using built-in specs. Target: i486-linux-gnu Configured with: ../src/configure -v --enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.2 --program-suffix=-4.2 --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr --enable-targets=all --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu Thread model: posix gcc version 4.2.3 (Ubuntu 4.2.3-2ubuntu7)

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transform_view: question about boilerplate code
by Zeljko Vrba 02 Sep '08

02 Sep '08

I have succeeded in writing the following transform functor: typedef bf::map<bf::pair<net, unsigned>, bf::pair<pin, unsigned> > Map; typedef bf::vector<unsigned, unsigned> Pair; struct Map2Pair { template<typename Sig> struct result; template<typename U> struct result<Map2Pair(U)> : remove_reference<T::second_type> { }; template<typename T> typename T::second_type operator()(T t) const { return t.second; } }; I have tested it, it works. The result magic has been copied from the transform_view example in the documentation and adjusted for the proper return type. Where can I read a bit more about result conventions? In particular, how does the template<typename U> struct result<Map2Pair(U)> : remove_reference<T::second_type> { }; specialization work when Map2Pair is a struct, and it doesn't even have a constructor! Even worse, why does it work at all when T is not in the scope of the template (.. because it's never used?) Yes, it is not used, the following functor also works: struct Map2Pair { template<typename T> typename T::second_type operator()(T t) const { return t.second; } }; When and how is the above version preferred than the simpler version?

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[Boost.Asio] service_name/port inconsistency
by Vjekoslav Brajkovic 02 Sep '08

02 Sep '08

Hi. When designing server-client model, one has to use boost::asio::ip::tcp::endpoint and boost::asio::ip::tcp::resolver::query respectively. What I am confused about is that query accepts std::string& service as a parameter whereas endpoint only accepts unsigned short. When writing code, it is really easy to get confused which constructor takes string and which short. I would appreciate is somebody could tell me if there is a way to create a server side component using integer as a service. - V

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