November 2016 - Boost-users

How to wrap boost::log class to user?
by Bruce 14 Nov '16

14 Nov '16

Hi, I am coding a project and I use boost::log. I need to supply the log function to user, but I don't want the user use boost::log directly. I want to wrap the boost::log into my class. But I still want to keep the << cascade feature. Basically, I need to implement a MyLogger class, which support: MyLogger(info) << bla bla bla; MyLogger(trace) << bla bla bla; and in the operator << function, I can use: BOOST_LOG_SEV macro. I don't know how to implement the operator << in MyLogger class. Can anybody helps me, Thanks.

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How to use boost::log to setup multiple logger?
by 刘宝良 13 Nov '16

13 Nov '16

Hi, I want to use boost::log to setup 3 logger for different purpose. Not one logger to have multiple output file. And I also want one logger to have one file output and a GUI output to be viewed by the end user. How to do it? -Bruce

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boost::filesystem::path::iterator and libstdc++ std::search
by Oleksandr Senkovych 11 Nov '16

11 Nov '16

Hi guys. Several days ago I've faced a strange issue with boost::filesystem::path::iterator - it segfaults when used in some STL algorithms. Here's a sample code that crashes: http://melpon.org/wandbox/permlink/58aIbfJWeGgMKMdF I looked at the issue a little bit and discovered that the reason for that is this part of iterator code: const path& dereference() const { return m_element; } So when using std::search libstdc++ has to convert binary predicate to unary for later use in std::find_if: __first1 = std::__find_if(__first1, __last1, __gnu_cxx::__ops::__iter_comp_iter(__predicate, __first2)); It does this by capturing dereferenced value of second iterator (__first2 in a piece of code above) but since iterator is passed by-value, this wrapper holds dangling reference to local member of iterator.m_element. Now according to C++ standard part 24.2.1 [iterator.requirements.general]: 10. Destruction of an iterator may invalidate pointers and references previously obtained from that iterator. So this looks like a violation of a standard by libstdc++ library. Unfortunately I couldn't get my account registered at https://gcc.gnu.org/bugzilla/ and was not able to file a bug, so can I ask you to help me with it?

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boost::filesystem::native
by Christopher J. Pisz 10 Nov '16

10 Nov '16

I did a Google search to see how to check if a given path is valid, preferably using boost. It brought me here: http://stackoverflow.com/questions/10426671/how-to-check-if-path-is-valid-i… Great! I say to myself. I then Google up the boost doc here: http://www.boost.org/doc/libs/1_62_0/libs/filesystem/doc/portability_guide.… I then write myself a test: #include <iostream> #include <sstream> #include <boost/filesystem.hpp> int main() { const std::string test1 = "D:\\Programing Projects\\Git Workspace\\Common\\x64\\Debug"; const std::string test2 = "D:\Programing Projects\\Git Workspace\\Common\\x64\\Debug\\"; const std::string test3 = "D:/Programing Projects/Git Workspace/Common/x64/Debug"; const std::string test4 = "D:/Programing Projects/Git Workspace/Common/x64/Debug/"; if (!boost::filesystem::native(test1)) { std::cout << "Boost says the following path is not valid for the native operating system: " << test1 << std::endl; } if (!boost::filesystem::native(test2)) { std::cout << "Boost says the following path is not valid for the native operating system: " << test2 << std::endl; } if (!boost::filesystem::native(test3)) { std::cout << "Boost says the following path is not valid for the native operating system: " << test3 << std::endl; } if (!boost::filesystem::native(test4)) { std::cout << "Boost says the following path is not valid for the native operating system: " << test4 << std::endl; } return 0; } The Test's Output: Boost says the following path is not valid for the native operating system: D:\Programing Projects\Git Workspace\Common\x64\Debug Boost says the following path is not valid for the native operating system: D:Programing Projects\Git Workspace\Common\x64\Debug\ Boost says the following path is not valid for the native operating system: D:/Programing Projects/Git Workspace/Common/x64/Debug Boost says the following path is not valid for the native operating system: D:/Programing Projects/Git Workspace/Common/x64/Debug/ What is wrong with that path that it says it is not valid for my native Windows 10 operating system?

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Boost.ASIO stuck on some requests?
by Matthieu Brucher 09 Nov '16

09 Nov '16

Hi, I have an app that serves different clients and it is based on Boost.ASIO. My current issue is that if the first client is fast enough (a continuous fast loop with Python module requests), then the other clients may time out with no good reason when trying to connect. Is there a way of figuring out who is actually waiting on who? Maybe the clients are starved because of an issue on their box, or there is an issue in ASIO that serves always the first connection? Or is it Windows? I tried multithreading the server, but that didn't help, and a run with VTune Amplifier shows me that the app is mainly waiting. But if I add a 100ms sleep between requests, then everything is fine. But this is not an acceptable solution, as the clients in real life will want to launch requests all the time. Regards, Matthieu Brucher -- Information System Engineer, Ph.D. Blog: http://blog.audio-tk.com/ LinkedIn: http://www.linkedin.com/in/matthieubrucher

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[boost][process] Formal review results
by Antony Polukhin 09 Nov '16

09 Nov '16

The Boost.Process library is accepted. Congratulations to Klemens, and thanks to everybody who reviewed the library! The votes were as follows: + Johannes - Niall Douglas +/- Tom Kent +/- Nat Goodspeed + Paul A. Bristow +/- Bjorn Reese + Edward Diener + Boris Schäling +/- Raphaël Londeix + Klaim - Joël Lamotte Legend: + accept - decline +/- accept conditionally Separate thanks to Gavin Lambert for providing a solution to deadlocking problem. Additional thanks to Nat Goodspeed, Niall Douglas, Gavin Lambert, Raphaël Londeix and Bjorn Reese for spending significant amount of time on discussing, reviewing or testing the library. -- Quick review summary -- During the review multiple technical issues were raised and as far as I know, Klemens already working on them. The biggest win of the review - is a fix for possible deadlock with pipes. The most controversial part of the library is it's interface. Many comments were addressing: * passing arguments * starting process right in `system(...)` function Current approaches have benefits and drawbacks, other approaches have different benefits and drawbacks. At this point some people agree that the current approach is the lesser evil. Reviewers also wished to have better/richer documentation. P.S.: Please continue with the discussion and report issues that would help to improve the library. -- Best regards, Antony Polukhin

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Visual Studio "15" Preview Update 5 configuration
by csiga.biga＠aol.com 09 Nov '16

09 Nov '16

Hi fellow users! This is my first message to this list, so take it easy if something’s not right. I wanted to build Boost with the latest Visual Studio spin, dubbed „15” Update 5 (RC coming sometime in November), but the configuration scripts do not quite work. Because _MSC_VER is 1910, I get the unkown compiler pragma warning, but what is more vexing, is that the configuration is not right, I get compilation errors in boost::functional, because std::unary_function has been deprecated since C++11, and VS „15” has removed this function from the STL. The _MSC_FULL_VER is 191024516, and I wanted to use the new toolset, because it has significantly improved in terms of conformance, most notably support for generalized constexpr. (See full list in the link) Can someone help with patching the configuration scripts? I would rather not start defining things to get deprecated features into scope again, but if nothing else works as a hotfix, than so be it. Thanks in advance, Máté

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Help in calculating the size of a boost::unordered_map
by Ram 07 Nov '16

07 Nov '16

Hi, I would like to calculate the size of my filled up boost::unordered_map including the house keeping. I was thinking of sizeof(boost:unordered_map mymap). I asked this question on stackoverflow but they say that wont help. Can somebody tell me an easy way to find the size including the housekeeping that it takes? The boost::unordered_map stores a std::string as the key and a pointer to my class object as the value. Thanks, Ram

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An Asio based header-only asynchronous MySQL client library
by Cheng Lian 07 Nov '16

07 Nov '16

Hey all, Here is an Asio based header-only asynchronous MySQL client library called Amy (*A*synchronous *My*SQL). https://github.com/liancheng/amy In short, this library enables you to work with MySQL in both asynchronous and blocking ways. Links to examples are included in the README file. Haven't got time and energy to write comprehensive documents, though. The interesting thing is that, I wrote this library years ago as an exercise, open sourced it, and then basically forgot about it. However, recently an European developer contacted me and said that they used it in one of their game projects in production and it was "amazing". So I decided to spend some time to polish it a little bit and send it out here to see whether there are anyone else who are interested in it. Please let me know what you think about it. Thanks! Best, Cheng

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Problem compiling a code that uses Boost
by Fernando E Alva Manchego 04 Nov '16

04 Nov '16

Hello, I'm trying to compile a code that uses boost. The code is this one: http://people.eng.unimelb.edu.au/tcohn/t3.html The version of boost installed in the machine is: 1.41 The machine where I'm running this code is a Scientific Linux release 6.8 (Carbon). The detailed error message that I get can be seen here: http://pastebin.com/ADj4j6k0 Basically, the errors messages are like this: undefined reference to `boost::program_options::options_description::options_description(...) undefined reference to `boost::program_options::validation_error::get_template(...) -lboost_program_options is in the compilation line. And I've checked using 'locate' that /usr/lib64 (as appears in the compilation line) contains: /usr/lib64/libboost_program_options-mt.so /usr/lib64/libboost_program_options-mt.so.5 /usr/lib64/libboost_program_options.so /usr/lib64/libboost_program_options.so.5 I would really appreciate any help you could help me with this error. Best, Fernando

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