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

weak_ptr copying causes destruction
by Travis Gockel 13 Jun '12

13 Jun '12

The copy constructor for weak_ptr constructs px like so: px(r.lock().get()) Why do it this way and not just: px(r.px) This introduces a somewhat unexpected race in that the shared_ptr obtained with lock() can be the last outstanding shared_ptr and the object can be destroyed during this copy. It is certainly not a *bug* in the smart_ptr library, but the behavior is unexpected and quite inconvenient. I assume there is a reason for calling lock() and not just copying the pointer and I would like to know what it is. Thanks, Travis Gockel Chief λ Combinator

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[boost-build] linking against pre-built libraries
by Jarosław Bober 13 Jun '12

13 Jun '12

Hello, What I'm trying to accomplish is to link against pre-built boost library that lives in $BOOST_ROOT/stage/lib, but the default naming convention comes with a boost version at the end: boost_unit_test_framework-vc80-mt-gd-1_47.lib I don't want to hardcode the exact name because some clients use older version of boost. unfortunatelly I cannot do something like this (or maybe I'm wrong): exe myExe : some.cpp /boost//unit_test_framework because that would build test library and I want to prevent that. I want to keep variants and compiler version in the name so --layout=system and --layout=tagged does not help me either. One solution would be to get rid of the boost version suffix(prefferable) and second would be to read BOOST_VERSION from boost/Jamroot and append that to the name of a library file, because I don't want clients to hardcode their boost version in jamfiles manually. How do I do that? Regards

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[property_tree] number of sections in an inifile
by Sean Farrow 13 Jun '12

13 Jun '12

Hi: If I have defined: boost::property_tree::ptree IniTree; What is the correct way to determine how many sections there are in an ini file. Should I use count, max_size, m_children or size? Any help appreciated. Cheers Sean.

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[MPL] mpl::at for AssociativeSequence
by dariomt＠gmail.com 13 Jun '12

13 Jun '12

Hi list, I'm trying to use the version of mpl::at with three template parameters, as specified here ( http://www.boost.org/doc/libs/1_46_0/libs/mpl/doc/refmanual/at.html) But I'm getting a compiler error saying 'boost::mpl::at' : too many template arguments. What am I doing wrong? #include <boost/mpl/map.hpp> #include <boost/mpl/at.hpp> #include <boost/mpl/size.hpp> #include <boost/mpl/empty.hpp> #include <boost/type_traits/is_same.hpp> using namespace boost; using namespace boost::mpl; typedef map< pair<int,unsigned> , pair<char,unsigned char> , pair<long_<5>,char[17]> , pair<int[42],bool> > m; BOOST_MPL_ASSERT_RELATION( size<m>::value, ==, 4 ); BOOST_MPL_ASSERT_NOT(( empty<m> )); BOOST_MPL_ASSERT(( is_same< at<m,int>::type, unsigned > )); BOOST_MPL_ASSERT(( is_same< at<m,long_<5> >::type, char[17] > )); BOOST_MPL_ASSERT(( is_same< at<m,int[42]>::type, bool > )); BOOST_MPL_ASSERT(( is_same< at<m,long>::type, void_ > )); BOOST_MPL_ASSERT(( is_same< at<m,long,void_>::type, void_ > )); // fails!

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question for use filesystem in vc++ with PPL
by young 12 Jun '12

12 Jun '12

I have question for use filesystem in vc++ with PPL. The code is listed here: #include <ppl.h> #include <boost/filesystem.hpp> namespace fs = boost::filesystem; std::vector<std::string> vFiles; fs::path path(dir); fs::directory_iterator end_dir; Concurrency::parallel_for((fs::directory_iterator) (path), end_dir, [&](fs::directory_iterator it) { if(!(fs::is_directory(it->status()))) { vFiles.push_back(it->path().filename().string()); } }); But it build failed with message: Eerror C2653: 'fs' : is not a class or namespace name what is wrong? I use Visual Studio 2010. -- View this message in context: http://boost.2283326.n4.nabble.com/question-for-use-filesystem-in-vc-with-P… Sent from the Boost - Users mailing list archive at Nabble.com.

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[Phoenix] using container algorithms
by Paul Heil 12 Jun '12

12 Jun '12

have a Visual Studio 2008 C++03 application using boost 1.49 phoenix. I would like to define a boost::function to remove an element from a list. For example: #include <boost/phoenix.hpp> #include <boost/function.hpp> #include <boost/phoenix/stl/container.hpp> #include <boost/phoenix/stl/algorithm/transformation.hpp> #include <algorithm> #include <list> int main() { namespace bp = boost::phoenix; namespace bpa = boost::phoenix::arg_names; std::list< int > a; boost::function< void( int ) > RemoveFromList = bp::remove( bp::ref( a ), bpa::arg1 ); return 0; } but I get a series of compiler errors on my RemoveFromList definition. Error 1 error C2504: 'boost::phoenix::impl::remove::result<Sig>' : base class undefined \boost\utility\result_of.hpp 80 Error 2 error C2039: 'type' : is not a member of 'boost::result_of<F>' \boost\phoenix\core\detail\preprocessed\function_eval_10.hpp 121 Error 3 error C2146: syntax error : missing ';' before identifier 'type' \boost\phoenix\core\detail\preprocessed\function_eval_10.hpp 122 Error 4 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int \boost\phoenix\core\detail\preprocessed\function_eval_10.hpp 122 Error 5 error C2602: 'boost::phoenix::detail::function_eval::result<Sig>::type' is not a member of a base class of 'boost::phoenix::detail::function_eval::result<Sig>' \boost\phoenix\core\detail\preprocessed\function_eval_10.hpp 122 Error 6 error C2868: 'boost::phoenix::detail::function_eval::result<Sig>::type' : illegal syntax for using-declaration; expected qualified-name \boost\phoenix\core\detail\preprocessed\function_eval_10.hpp 122 A similar function AddToList compiles cleanly: boost::function< void( int ) > AddToList = bp::push_back( bp::ref( a ), bpa::arg1 ); This also works correctly (but is much less elegant): boost::function< void( int ) > RemoveFromList = bp::bind( &std::remove< std::list< int >::iterator, int >, a.begin(), a.end(), bpa::arg1 ); What is the correct way to use the boost.phoenix.remove function? Thanks

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time conversion
by young 11 Jun '12

11 Jun '12

I would like to convert utc time to local time. I found 2 headers which confuse me. #include <boost/date_time/local_time_adjustor.hpp> #include <boost/date_time/c_local_time_adjustor.hpp> which one to use? c_local_adjustor or local_adjustor? what is the difference? -- View this message in context: http://boost.2283326.n4.nabble.com/time-conversion-tp4631162.html Sent from the Boost - Users mailing list archive at Nabble.com.

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[Nowide] Formal Review Request
by Artyom Beilis 11 Jun '12

11 Jun '12

Hello, I'd like to ask to add Boost.Nowide to review queue: Boost.Nowide is a library implemented by Artyom Beilis that make cross platform Unicode aware programming easier. The library provides an implementation of standard C and C++ library functions, such that their inputs are UTF-8 aware on Windows without requiring to use Wide API. Sources: http://cppcms.com/files/nowide/ Docs: http://cppcms.com/files/nowide/html/ Git: git://cppcms.git.sourceforge.net/gitroot/cppcms/nowide Thank You Very Much! Artyom Beilis -------------- CppCMS - C++ Web Framework: http://cppcms.com/ CppDB - C++ SQL Connectivity: http://cppcms.com/sql/cppdb/

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[filesystem] converting boost::filesystem::wofstream to std::ostream
by Sean Farrow 10 Jun '12

10 Jun '12

Hi: I have a library that takes a function taking an std::ostream &. Is it possible to convert a boost::filesystem::wofstream to an std::ostream. Any help appreciated. Cheers Sean.

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question about boost pointer
by young 10 Jun '12

10 Jun '12

I have question about boost pointer. If I define a pointer by using: boost::shared_ptr<int> p; How to use p to get next int? In classic c++ pointer, I could use *(p+1). How to do it in Boost? -- View this message in context: http://boost.2283326.n4.nabble.com/question-about-boost-pointer-tp4631069.h… Sent from the Boost - Users mailing list archive at Nabble.com.

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