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Re: [Boost-users] [asio] wrap lambda async_receive call
by Cheng Mo 25 Mar '15

25 Mar '15

Hi Gravin: >The compiler will build the code for a lambda only once regardless of >how many times it's called. But it also won't let you create a >recursive lambda, which is what you would need if you wanted to have a >read operation repeat itself when it completes (which is the most common >case). I supposed that which would be built once durning compiling time but multi time in running time, wasn't it ? It will implement every time when async_xxx be invoded. Although I was not do test for proving that. >Well, actually that's not quite true -- you can type-erase a lambda via >std::function or similar and then call it recursively. But AFAIK you >can only do this when capturing by reference, and you can't safely do >that with a locally declared lambda when making async calls. So it's >not really useful in this context. Private member function or std::function type various and transmitted as reference could be better in this case. >> It's better that build a function object in static. What do you think ? >Function objects have a similar lifetime issue, and making one static is >potentially dangerous if you could have multiple operations or >connections running concurrently. It's usually simplest to use a >private method of the containing class, which is what most of the >example code does. You are right, the static is dangerous in multiple op and concurrence, Thanks. (If you really want to hide it from clients of your class, then use the PIMPL idiom.) Cheer~ 程墨 PBI―北京加维通讯电子技术有限公司地址：北京市海淀区西北旺镇丰智东路3号院邮编：100094 Mail: mcheng(a)pbicn.com

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[Boost Graph Library][Serialization] adjacency_list serialization crashes.
by Hardik Soni 23 Mar '15

23 Mar '15

Hi All, I am facing a core dump while serializing adjacency_list class object of BGL. I am using <boost/graph/adj_list_serialize.hpp> file for serialization. Following is the stack trace. I have highlighted the types used for boost::adjacency_list on frame number 19. I am using bundled property method to assign property to nodes and vertices. I tried with no_poperty, the outcome was the same. Does anyone have any idea, why is it crashing? The exception name is "output stream error". #0 0x0000003908e359e9 in raise () from /lib64/libc.so.6 #1 0x0000003908e370f8 in abort () from /lib64/libc.so.6 #2 0x000000390d660565 in __gnu_cxx::__verbose_terminate_handler() () from /lib64/libstdc++.so.6 #3 0x000000390d65e6c6 in ?? () from /lib64/libstdc++.so.6 #4 0x000000390d65e6f3 in std::terminate() () from /lib64/libstdc++.so.6 #5 0x000000390d65e91f in __cxa_throw () from /lib64/libstdc++.so.6 #6 0x000000000040de72 in boost::serialization::throw_exception<boost::archive::archive_exception> (e=...) at /usr/local/include/boost/serialization/throw_exception.hpp:36 #7 0x000000000040dce7 in boost::archive::basic_text_oprimitive<std::ostream>::save_impl<int> (this=0x7fffffffd5b0, t=@0x7fffffffd188: 6) at /usr/local/include/boost/archive/basic_text_oprimitive.hpp:122 #8 0x000000000040dc24 in boost::archive::basic_text_oprimitive<std::ostream>::save<int> (this=0x7fffffffd5b0, t=@0x7fffffffd188: 6) at /usr/local/include/boost/archive/basic_text_oprimitive.hpp:176 #9 0x000000000040db91 in boost::archive::xml_oarchive_impl<boost::archive::xml_oarchive>::save<int> (this=0x7fffffffd580, t=@0x7fffffffd188: 6) at /usr/local/include/boost/archive/xml_oarchive.hpp:75 #10 0x000000000040daeb in boost::archive::save_access::save_primitive<boost::archive::xml_oarchive, int> (ar=..., t=@0x7fffffffd188: 6) at /usr/local/include/boost/archive/detail/oserializer.hpp:88 #11 0x000000000040d9d1 in boost::archive::detail::save_non_pointer_type<boost::archive::xml_oarchive>::save_primitive::invoke<int> (ar=..., t=@0x7fffffffd188: 6) at /usr/local/include/boost/archive/detail/oserializer.hpp:232 #12 0x000000000040d595 in boost::archive::detail::save_non_pointer_type<boost::archive::xml_oarchive>::invoke<int> (ar=..., t=@0x7fffffffd188: 6) at /usr/local/include/boost/archive/detail/oserializer.hpp:308 #13 0x000000000040cccb in boost::archive::save<boost::archive::xml_oarchive, int const> (ar=..., t=@0x7fffffffd188: 6) at /usr/local/include/boost/archive/detail/oserializer.hpp:525 #14 0x000000000040c678 in boost::archive::detail::common_oarchive<boost::archive::xml_oarchive>::save_override<int const> (this=0x7fffffffd580, t=@0x7fffffffd188: 6) at /usr/local/include/boost/archive/detail/common_oarchive.hpp:69 #15 0x000000000040be67 in boost::archive::basic_xml_oarchive<boost::archive::xml_oarchive>::save_override<int> (this=0x7fffffffd580, t=...) at /usr/local/include/boost/archive/basic_xml_oarchive.hpp:112 #16 0x000000000040b5bc in boost::archive::detail::interface_oarchive<boost::archive::xml_oarchive>::operator<< <boost::serialization::nvp<int> const> (this=0x7fffffffd580, t=...) at /usr/local/include/boost/archive/detail/interface_oarchive.hpp:63 #17 0x000000000040b021 in boost::serialization::save<boost::archive::xml_oarchive, boost::vecS, boost::vecS, boost::directedS, std::string, std::string, std::string, boost::listS> (ar=..., graph=...) at /usr/local/include/boost/graph/adj_list_serialize.hpp:48 #18 0x000000000040aa65 in boost::serialization::free_saver<boost::archive::xml_oarchive, boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS, std::string, std::string, std::string, boost::listS> >::invoke (ar=..., t=..., file_version=0) at /usr/local/include/boost/serialization/split_free.hpp:45 #19 0x000000000040a6e2 in boost::serialization::split_free<boost::archive::xml_oarchive, boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS, std::string, std::string, std::string, boost::listS > > (ar=..., t=..., file_version=0) at /usr/local/include/boost/serialization/split_free.hpp:74 #20 0x000000000040a2cf in boost::serialization::serialize<boost::archive::xml_oarchive, boost::vecS, boost::vecS, boost::directedS, std::string, std::string, std::string, boost::listS> (ar=..., graph=..., file_version=0) at /usr/local/include/boost/graph/adj_list_serialize.hpp:109 Thanks, Hardik Soni

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try_numeric_convert (akin to try_lexical_convert)
by Chris Franz 23 Mar '15

23 Mar '15

We're using the new try_lexical_convert function in our code so we can encapsulate errors in the standard manner used in our project. A counterpart for numeric_cast would be useful. Is any such thing in the works?

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Re: [Boost-users] [range] functor defined result_type with no &, causing temporary variable warnings on VS
by Nick Stokes 23 Mar '15

23 Mar '15

This question is a followup from a multi_index discussion at http://lists.boost.org/boost-users/2015/03/84028.php. Joaquin explained the situation very accurately, so I am including his explanation following my summary below for context (I hope this does not constitute top posting :) In summary the problem is: struct Foo { int i; } struct GetIntMem { typedef int result_type; const int& operator()(const Foo& f) const { return f.i ; } }; aFooRange | boost::adaptors::transformed( GetIntMem() ); yields "warning C4172: returning address of local variable or temporary" in VS 2012 and 2013, with Boost 1.49. There is no warning with Boost 1.56. Is this construct safe with Boost 1.49? In the context of multi_index, the key extractor type is the "GetIntMem". Please see below for details. On Fri, Mar 20, 2015 at 5:33 AM, Joaquin M Lopez Munoz <joaquin(a)tid.es> wrote: > > Please don't top-post: > > http://www.boost.org/community/policy.html#quoting > > Sure. Sorry. Thanks for the link, useful info. > So, to sum up the top-posted chain of posts of yours, > boost::multi_index::member<Class,Type,PtrToMember> publicizes its > result type as > > typedef Type result_type; > > yet its call operator overloads return Type& or const Ttype&, and this > results in some warnings in VS 12 / Boost 1.49 when used in combination > with boost::adaptors::transform. > > So, whatever the problem is, it does not belong in Boost.MultiIndex, > since member merely defines result_type in accordance with the > requirements of the Key Extractor model: > > http://www.boost.org/libs/multi_index/doc/reference/ > key_extraction.html#key_extractors > > I mean, defining result_type in whatever way (or not defining it > at all) is not an error per se; it is Boost.Range assumptions on > this typedef that might be problematic. Unfortunately, the documentation > for boost::adaptors::tranform(rng,fun) > > http://www.boost.org/libs/range/doc/html/range/reference/ > adaptors/reference/transformed.html > > do not mention what the requirements on fun are, whether it is > mandatory that a result_type be present and how this is handled by > Boost.Range. I suggest you initiate a new discussion with [range] > in the subject line showing the problem you found. I suspect this > is related to boost:result_of > > http://www.boost.org/libs/utility/utility.htm#result_of > > which Boost.Range seems to use internally, but only the author can > tell. Also, if the problem does not show in Boost 1.56 you might be > encouraged to simply upgrade and move on. > > Thanks Joaquin. I could not describe the problem any better than what you have above, so I hope you don't mind that I re-purposed this thread. The question is possibly is rather moot at this point, as the issue does not manifest in Boost 1.56 (possibly earlier). However, it'd be interesting to understand why, and at least make sure using 1.49 this way is safe (I am stuck with that version for the time being). Thanks very much if you followed along this far, and sorry as I fear this post ended up more convoluted that it needs to be :P Nick

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Re: [Boost-users] [asio] wrap lambda async_receive call
by Cheng Mo 23 Mar '15

23 Mar '15

Hi Gavin: >Having said this, using lambdas can get tricky in real-world code, as >it's common to want to start the same read operation when the first >completes, and so on. Just like you said, will the code build a lambda expression when async_read() invoked ? So that "[=](const error_code& ec, size_t count" will be built servial times, it is kind of lavish for contructing the lambda expression, isn't ? It's better that build a function object in static. What do you think ? Cheers~ Cheer~ 程墨 PBI―北京加维通讯电子技术有限公司地址：北京市海淀区西北旺镇丰智东路3号院邮编：100094 Mail: mcheng(a)pbicn.com

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New Iterator Concepts deprecated?
by Peter Johansson 22 Mar '15

22 Mar '15

Hi boosters, I've been looking into the New Iterator Concepts http://www.boost.org/doc/libs/1_57_0/libs/iterator/doc/new-iter-concepts.ht… and then I found this comment on boost trac https://svn.boost.org/trac/boost/ticket/1296 where dave seven years ago wrote: "/the new categories are a dead-end as the standard has lifted the reference requirement on forward iterators, so I don't plan to implement anything like this. I actually plan to deprecate the new categories./" This was seven years ago and I can't see anything about that the concepts have been deprecated, so I just wonder if this statement still holds or did the standard take back the reference requirement? Cheers, -- Peter Johansson

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Boost.Locale Examples doesn't runs in VS2010
by Sarvagya Pant 22 Mar '15

22 Mar '15

I have been trying to learn Boost.Locale Module. Consider http://www.boost.org/doc/libs/1_55_0/libs/locale/doc/html/conversions_8cpp-… example. The code gets successfully compiled but when I try to run it, it gives the error Unhandled exception at 0x74d34b32 in LearningCPP.exe: Microsoft C++ exception: std::bad_cast at memory location 0x00a6fa48.. I have attached the stack-trace of the program also. Here it is: KernelBase.dll!74d34b32() [Frames below may be incorrect and/or missing, no symbols loaded for KernelBase.dll] KernelBase.dll!74d34b32() > msvcr100d.dll!_nh_malloc_dbg(unsigned int nSize, int nhFlag, int nBlockUse, const char * szFileName, int nLine) Line 302 + 0x1d bytes C++ msvcr100d.dll!malloc(unsigned int nSize) Line 56 + 0x15 bytes C++ LearningCPP.exe!std::use_facet<boost::locale::converter<char> >(const std::locale & _Loc) Line 526 C++ LearningCPP.exe!boost::locale::to_upper<char>(const char * str, const std::locale & loc) Line 225 + 0x9 bytes C++ LearningCPP.exe!main() Line 170 + 0xc4 bytes C++ LearningCPP.exe!__tmainCRTStartup() Line 555 + 0x19 bytes C LearningCPP.exe!mainCRTStartup() Line 371 C kernel32.dll!75268543() ntdll.dll!776bac69() ntdll.dll!776bac3c() Did anyone faced this issue when using Boost.Locale in Visual Studio 2010? If so, how do I resolve this issue? *PS:* I have used option Use Unicode Character Set under the Character Set option of Visual Studio. I believe the libraries are correctly linked too. -- *sarvagya*

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boost::property_tree::ptree with write_xml
by Uthpal Urubail 21 Mar '15

21 Mar '15

All, I am looking got the help with xml writer using property tree. My requirement is to write a user defined comment (in below example /*comment*/) in every line of XML file. Example: /*comment*/<debug> /*comment*/ <filename>debug.log</filename> /*comment*/ <modules> /*comment*/ <module>Finance</module> /*comment*/ <module>Admin</module> /*comment*/ <module>HR</module> /*comment*/ </modules> /*comment*/ <level>2</level> /*comment*/</debug> Can someone help me in solving the above? Any help on this would be highly appreciated. boost::property_tree::xml_writer_settings<std::string> w(' ', 4); write_xml(os, pt,w); Regards, UJ

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phoenix 1.55 no-arg mem function fails
by MM 20 Mar '15

20 Mar '15

#include <boost/phoenix/phoenix.hpp> struct Foo { const int& bar() const { return i; } int i; }; int main() { Foo f; const int& ir = boost::phoenix::bind(&Foo::bar, f)(); } The above fails to compile. linux g++492 -std=c++11 -c 1.cpp When bar() has a single int arg for e.g., boost::phoenix::bind(&Foo::bar, f, 5)(); succeeds. The error: In file included from /usr/include/boost/phoenix/bind/bind_member_variable.hpp:13:0, from /usr/include/boost/phoenix/bind.hpp:17, from /usr/include/boost/phoenix/phoenix.hpp:17, from 1.cpp:1: /usr/include/boost/phoenix/bind/detail/member_variable.hpp: In instantiation of ‘struct boost::phoenix::detail::member_variable<const int&() const, const int& (Foo::*)() const>’: /usr/include/boost/proto/make_expr.hpp:77:16: required from ‘struct boost::proto::detail::protoify<boost::phoenix::detail::member_variable<const int&() const, const int& (Foo::*)() const>, boost::proto::domainns_::basic_default_domain>’ /usr/include/boost/proto/detail/preprocessed/make_expr_.hpp:70:9: required from ‘struct boost::proto::detail::make_expr_<boost::phoenix::detail::tag::function_eval, boost::proto::domainns_::basic_default_domain, boost::phoenix::detail::member_variable<const int&() const, const int& (Foo::*)() const>, Foo, void, void, void, void, void, void, void, void, void>’ /usr/include/boost/proto/make_expr.hpp:185:13: required from ‘struct boost::proto::result_of::make_expr<boost::phoenix::detail::tag::function_eval, boost::proto::domainns_::basic_default_domain, boost::phoenix::detail::member_variable<const int&() const, const int& (Foo::*)() const>, Foo, void, void, void, void, void, void, void, void, void>’ /usr/include/boost/phoenix/core/preprocessed/expression_10.hpp:84:13: required from ‘struct boost::phoenix::expr_ext<boost::phoenix::actor, boost::phoenix::detail::tag::function_eval, boost::phoenix::detail::member_variable<const int&() const, const int& (Foo::*)() const>, Foo, void, void, void, void, void, void, void, void, void>’ /usr/include/boost/phoenix/core/preprocessed/expression_10.hpp:24:12: required from ‘struct boost::phoenix::expr<boost::phoenix::detail::tag::function_eval, boost::phoenix::detail::member_variable<const int&() const, const int& (Foo::*)() const>, Foo, void, void, void, void, void, void, void, void, void>’ /usr/include/boost/phoenix/core/detail/preprocessed/function_eval_10.hpp:7:561: required from ‘struct boost::phoenix::detail::expression::function_eval<boost::phoenix::detail::member_variable<const int&() const, const int& (Foo::*)() const>, Foo, void, void, void, void, void, void, void, void, void>’ /usr/include/boost/phoenix/bind/bind_member_variable.hpp:37:5: required by substitution of ‘template<class RT, class ClassT> const typename boost::phoenix::detail::expression::function_eval<boost::phoenix::detail::member_variable<RT, RT ClassT::*>, ClassT>::type boost::phoenix::bind(RT ClassT::*, ClassT&) [with RT = const int&() const; ClassT = Foo]’ 1.cpp:11:52: required from here /usr/include/boost/phoenix/bind/detail/member_variable.hpp:50:17: error: forming reference to qualified function type ‘const int&() const’ RT& operator()(Class& obj) const ^ /usr/include/boost/phoenix/bind/detail/member_variable.hpp:59:23: error: forming reference to qualified function type ‘const int&() const’ RT const& operator()(Class const& obj) const ^ /usr/include/boost/phoenix/bind/detail/member_variable.hpp:68:17: error: forming reference to qualified function type ‘const int&() const’ RT& operator()(Class* obj) const ^ /usr/include/boost/phoenix/bind/detail/member_variable.hpp:74:23: error: forming reference to qualified function type ‘const int&() const’ RT const& operator()(Class const* obj) const Rds,

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phoenix: c++11
by MM 20 Mar '15

20 Mar '15

Hello Are there plans to add emplace_back to the stl part of phoenix? MM

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