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[Variant] Odd linker errors that somehow involve boost::variant
by James Madison 19 Jan '09

19 Jan '09

[NOTE : this is using boost v1.32. I am forced to use this version] In the code I am trying to compile I have a boost variant defined as: boost::variant<int, char, double, std::string, ACE_Time_Value> and it is used in several different ways. This project compiles and links fine using debug settings, essentially the -g flag in gcc, however whenever I try to compile without that flag I get the following error, repeated hundreds of times: `.gnu.linkonce.t._ZNSt3mapIiN5boost7variantIicdSs14ACE_Time_ValueNS0_6detail7variant5void_ES5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_EESt4lessIiESaISt4pairIKiS6_EEEixERSA_' referenced in section `.gnu.linkonce.r._ZNSt3mapIiN5boost7variantIicdSs14ACE_Time_ValueNS0_6detail7variant5void_ES5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_EESt4lessIiESaISt4pairIKiS6_EEEixERSA_' of ./src/geneva/infra/messaging/ResponseMsg.o: defined in discarded section `.gnu.linkonce.t._ZNSt3mapIiN5boost7variantIicdSs14ACE_Time_ValueNS0_6detail7variant5void_ES5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_S5_EESt4lessIiESaISt4pairIKiS6_EEEixERSA_' of ./src/geneva/infra/messaging/ResponseMsg.o Google is not helping diagnose the problem at all. I am wondering if anyone here can point me in the right direction.

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Problem with shared_ptr
by Germán Diago 18 Jan '09

18 Jan '09

What's wrong with this code? When I push_back ptr to the vector, it pushes 0 instead of the value contained in ptr (which I checked and is non-zero). std::vector<boost::shared_ptr<BaseClass> > baseobjects = get_base_objects(path); std::vector<boost::shared_ptr<DerivedClass> > result(get_base_objects.size()); BOOST_FOREACH (boost::shared_ptr<BaseClass> en, baseobjects) { boost::shared_ptr<DerivedClass> ptr = boost::dynamic_pointer_cast<DerivedClass>(en); //Error when push_back. Instead of ptr, I get 0 result.push_back(ptr); } Thanks.

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combining asio::serial_port with iostreams::stream
by Christoph Gysin 18 Jan '09

18 Jan '09

Hi boost users I'm a newbie to boost trying to use a serial port as an iostream. While searching the archives I found a post by Rob Desbois (2008-01-18 13:02) trying to achive the same. Unfortunately the solution wasn't posted. This is what I got so far: #include <boost/asio.hpp> #include <boost/iostreams/stream.hpp> class serial_device { public: typedef char char_type; typedef boost::iostreams::bidirectional_device_tag category; serial_device(boost::asio::io_service& io_service, const std::string& port, int baudrate = 9600) : serial_port(io_service, port) { typedef boost::asio::serial_port_base spb; serial_port.set_option(spb::baud_rate(baudrate)); }; std::streamsize read(char* buf, std::streamsize n) { boost::asio::read(serial_port, boost::asio::buffer(buf, n)); } std::streamsize write(const char* buf, std::streamsize n) { boost::asio::write(serial_port, boost::asio::buffer(buf, n)); } private: boost::asio::serial_port serial_port; }; int main(void) { boost::asio::io_service io_service; serial_device serial(io_service, "/dev/ttyS0", 115200); //boost::iostreams::stream<serial_device> s(serial); } If I uncomment the last line it fails to compile: g++ -lboost_iostreams-mt -lboost_system-mt -lboost_thread-mt iostream.cpp -o iostream /usr/include/boost/noncopyable.hpp: In copy constructor 'boost::asio::basic_io_object<boost::asio::serial_port_service>::basic_io_object(const boost::asio::basic_io_object<boost::asio::serial_port_service>&)': /usr/include/boost/asio/basic_io_object.hpp:30: instantiated from 'boost::iostreams::stream<Device, Tr, Alloc>::stream(Device&, int, int) [with Device = serial_device, Tr = std::char_traits<char>, Alloc = std::allocator<char>]' iostream.cpp:36: instantiated from here /usr/include/boost/noncopyable.hpp:27: error: 'boost::noncopyable_::noncopyable::noncopyable(const boost::noncopyable_::noncopyable&)' is private /usr/include/boost/asio/basic_io_object.hpp:30: error: within this context /usr/include/boost/noncopyable.hpp: In copy constructor 'boost::asio::detail::reactive_descriptor_service<boost::asio::detail::epoll_reactor<false> >::implementation_type::implementation_type(const boost::asio::detail::reactive_descriptor_service<boost::asio::detail::epoll_reactor<false> >::implementation_type&)': /usr/include/boost/noncopyable.hpp:27: error: 'boost::noncopyable_::noncopyable::noncopyable(const boost::noncopyable_::noncopyable&)' is private /usr/include/boost/asio/detail/reactive_descriptor_service.hpp:47: error: within this context /usr/include/boost/asio/basic_io_object.hpp: In copy constructor 'boost::asio::basic_io_object<boost::asio::serial_port_service>::basic_io_object(const boost::asio::basic_io_object<boost::asio::serial_port_service>&)': /usr/include/boost/asio/basic_io_object.hpp:30: note: synthesized method 'boost::asio::detail::reactive_descriptor_service<boost::asio::detail::epoll_reactor<false> >::implementation_type::implementation_type(const boost::asio::detail::reactive_descriptor_service<boost::asio::detail::epoll_reactor<false> >::implementation_type&)' first required here /usr/include/boost/asio/basic_serial_port.hpp: In copy constructor 'boost::asio::basic_serial_port<boost::asio::serial_port_service>::basic_serial_port(const boost::asio::basic_serial_port<boost::asio::serial_port_service>&)': /usr/include/boost/asio/basic_serial_port.hpp:51: note: synthesized method 'boost::asio::basic_io_object<boost::asio::serial_port_service>::basic_io_object(const boost::asio::basic_io_object<boost::asio::serial_port_service>&)' first required here iostream.cpp: In copy constructor 'serial_device::serial_device(const serial_device&)': iostream.cpp:5: note: synthesized method 'boost::asio::basic_serial_port<boost::asio::serial_port_service>::basic_serial_port(const boost::asio::basic_serial_port<boost::asio::serial_port_service>&)' first required here /usr/include/boost/iostreams/stream.hpp: In constructor 'boost::iostreams::stream<Device, Tr, Alloc>::stream(Device&, int, int) [with Device = serial_device, Tr = std::char_traits<char>, Alloc = std::allocator<char>]': /usr/include/boost/iostreams/stream.hpp:129: note: synthesized method 'serial_device::serial_device(const serial_device&)' first required here make: *** [iostream] Error 1 Could anyone please explain what I'm doing wrong? Thanks, Chris -- echo mailto: NOSPAM !#$.'<*>'|sed 's. ..'|tr "<*> !#:2" org@fr33z3

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[program_options] Can you use position-sensitive parameters?
by Adam Nielsen 18 Jan '09

18 Jan '09

Hi all, I can't find anything in the docs that tells me whether this is possible without writing custom parsers etc. so if anyone knows whether this can be done please let me know. I'd like to be able to use position-sensitive parameters. For example, a program to work with .zip files: zip --rename=one.bin:alpha.bin --add=one.bin --rename=one.bin:beta.bin Using this example, the initial --rename would need to be acted upon first, before -add (otherwise one.bin would get overwritten) and likewise the last --rename must be acted upon after -add, otherwise the wrong file (or no file) would be renamed. If I use normal string vectors the order of the parameters will be lost so this won't work. Is this sort of parsing possible with program_options? Thanks, Adam.

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shared_ptr custom deleter implementation
by Zachary Turner 18 Jan '09

18 Jan '09

I'm trying to write a class lazy<T>, the skeleton of which is as follows: template<class T> class lazy { public: template<class F> lazy(F fetcher) //Store fetcher somehow { } T get() { if (!cache) cache = fetch(); //Access fetcher from constructor in a type-safe way return cache.get(); } private: optional<T> cache; }; My problem is how to store / access the fetch function in a type safe way. The reason I titled this message how I did is because I see that shared_ptr does almost exactly the same thing with its deleter. But I'm still kind of new to the whole metaprogramming thing and having a little difficulty really getting my head around how it works. I guess there is some general "pattern" that applies in both of these cases as well as any other case where you want to store some value, the type of which is deduced by the constructor, and then later accessing that value in a type safe way. This message could probably have been equally well fitting in a general C++ forum, but since this is a problem that seems to arise really frequently in boost and other code using heavy templates, I guess I'm in pretty good company here as well. The following seems close to a solution: template<class T> class lazy_impl_base { virtual T fetch() = 0; }; template<class T, class F> class lazy_impl : public lazy_impl_base<T> { // etc }; and then storing a lazy_impl_base<T>* in lazy<T>. But there are strange compiler warnings, and I fear I will encounter subtle errors when I attempt to use it with functors, binders, and other non trivial "functions". Can anyone offer some guidance here? Maybe a quick high level overview of how shared_ptr and other boost libraries solve this problem, or even an implementation of lazy that works :P

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Optionally enforce const correctness in argument dependent lookup
by er 18 Jan '09

18 Jan '09

Hi All, The example below illustrates my intent, but obviously it's not the right approach... so I'm hoping someone has a suggestion. template<typename X> struct enforce_constness{ typedef add_reference<const X> type; }; template<template<typename> class T = enforce_constness> struct A{ template<typename X> void operator()(typename T<X>::type x)const{ // Under default I'd like const X& }; } X x; A<> a; a(x); no match for call to (A<T>)(X&)

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problem with boost::is_same
by Zachary Turner 18 Jan '09

18 Jan '09

I have a question about the following code: typedef void(intArrayParamFunc)(int[]); typedef void(intPtrParamFunc)(int*); BOOST_STATIC_ASSERT((boost::is_same<intArrayParamFunc,intPtrParamFunc>::value)); BOOST_STATIC_ASSERT((boost::is_same<int*,int[]>::value)); cout << typeid(intArrayParamFunc).name() << endl; cout << typeid(intPtrParamFunc).name() << endl; cout << typeid(int*).name() << endl; cout << typeid(int[]).name() << endl; The first assert compiles but the second fails, which means that boost::is_same<> thinks that int* and int[] are different, but void(int[]) and void(int*) are the same. Why is this? The typeids print out the following: void __cdecl(int * const) void __cdecl(int *) int * int [0] I'm using Visual Studio 2008. I notice that typeid tells me that intArrayParamFunc is void(int* const). So why does boost::is_same<> compare them equal? Surely void(int* const) should not be the same type as void(int*). Unless this is just some obscure language subtlety I'm not aware of. So is this a bug in boost::is_same<>, a bug in my compiler, or no bugs at all and everything is working perfectly?

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[date_time] Error compiling greg_month with Intel C++ 11.0
by Remko Tronçon 17 Jan '09

17 Jan '09

Hi, I'm having a problem compiling greg_month.cpp with Intel C++ 11.0. I used bcp to create a local version of boost 1.37.0. When I run icc -I. -c libs/date_time/src/gregorian/greg_month.cpp I get: (0) internal error: backend signals (and nothing more). Is this a known problem? It works fine with other compilers, and the rest of boost compiles fine for me with ICC as well. thanks, Remko

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Serialization on Mac Followup
by Brandon Aubie 17 Jan '09

17 Jan '09

I have gotten everything working correctly now. The first time when I installed boost, I downloaded the source, did the regular configure, make, install into /usr/local. I then tried using MacPorts to install Boost 1.37 and this time, using the MacPorts installation, everything is working fine!

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[boost][iostreams] Crash when using bzip2 codec
by Marc Viala 17 Jan '09

17 Jan '09

Hi, During our migration from Boost 1.34.1 to Boost 1.37.0 we are facing a bug in bzip2 codec (boost::iostreams::bzip2_compressor & boost::iostreams::bzip2_compressor). To demonstrate it, you will find hereafter a code snippet: #include <fstream> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/combine.hpp> #include <boost/iostreams/filter/bzip2.hpp> #include <boost/iostreams/filter/gzip.hpp> #include <boost/iostreams/filter/zlib.hpp> void main() { using namespace boost::iostreams ; // Run smoothly { filtering_stream<bidirectional> chain ; chain.push(combine(gzip_decompressor(), gzip_compressor())) ; chain.push(std::fstream("test.gz", std::ios::binary|std::ios::out)) ; chain << "test" ; } // Run smoothly { filtering_stream<bidirectional> chain ; chain.push(combine(zlib_decompressor(), zlib_compressor())) ; chain.push(std::fstream("test.zip", std::ios::binary|std::ios::out)) ; chain << "test" ; } // Crash in bzip2_decompressor_impl::close { filtering_stream<bidirectional> chain ; chain.push(combine(bzip2_decompressor(), bzip2_compressor())) ; chain.push(std::fstream("test.bz2", std::ios::binary|std::ios::out)) ; chain << "test" ; } } The crash in bzip2_decompressor_impl::close is due to an access violation @ line 359 in boost/iostreams/filter/bzip2.hpp. For the other codec, zlib & gzip, everything runs smoothly. Set-up: Boost 1.37.0 Windows XP SP3 Visual C++ 7.1 Bzip2 Library 1.0.5 With Boost 1.34.1 the bzip2 codec seems to run smoothly. Is there any work around for this codec w/ Boost 1.37.0? Thanks in advance. Best regards, Marc Viala

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