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[boost::asio] Wait for multiple async_read()'s
by Adam Zegelin 28 Jan '17

28 Jan '17

Hi, I'm writing a boost::asio application that communicates with multiple streams. I'd like to write data to these streams then wait for everyone to reply before performing computation on the resulting data. What is the best way to implement this? The route I've ventured down involves me calling async_write() on each stream, with the callback hander executing async_read(). But this where I'm stuck. What is the best way to execute one final hander once all read operations have completed? One solution I've found, though it feels "un-asio" is to pass the use_future option as the hander for the reads. The result is futures for each read, which I can then place into a list<future>, and have an additional io_service.post()'ed handler call get() on these futures. The only issue with this is that I must call io_service.run() from more than one thread, since the handler calling get() blocks — otherwise I can potentially deadlock the whole application. Another alternative I can think of is that the function that schedules all the async_writes knows ahead-of-time the number of reads that need to be completed. Each async_read() handler would put its results into a shared list and then, if the list's size is equal to the expected number of results, fires the "completion" handler. While easy enough to implement, this seems fraught with issues. If there is more than one thread calling io_service.run(), then access to the shared list has to be synchronised. Also, it doesn't seem very generic — I have a number of places where this write n, read n, execute (or is it map, reduce?) pattern needs to happen, and I'd prefer a solution that was write one, worked everywhere. Any help would be appreciated. - Adam

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[Parameter] Warnings from Preprocessor
by Phillip Seaver 27 Jan '17

27 Jan '17

I recently updated to 1.63 from 1.57, and I'm now getting warnings from usages of BOOST_PARAMETER_MEMBER_FUNCTION on Windows (msvc-12.0) like: warning C4003: not enough actual parameters for macro 'BOOST_PP_SEQ_DETAIL_EMPTY_SIZE' warning C4003: not enough actual parameters for macro 'BOOST_PP_SEQ_DETAIL_IS_NOT_EMPTY' The code appears to be working, but since it's used in headers, I get a lot of warnings. Here's one of the usages: BOOST_PARAMETER_MEMBER_FUNCTION((Revision_t), CreateForegroundWhite, tag, (optional (imgclass, (Class_t), ClassPrint) (fromimage, (bool), true) (blackasgray, (bool), false) )) Should I be concerned about the warnings? Any way to get rid of them? Thanks, Phillip

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Fwd: compiling boost for windows 32 on ubuntu 64 machine
by Jack Kumba 27 Jan '17

27 Jan '17

Hello, I'm trying to compile boost for windows 32-bit on my ubuntu-64 but I'm not able to. what I do is as follows: - I created a file called user-config.jam in my ubuntu home directory and had put the below in it using gcc : : "i686-w64-mingw32-g++" - then, i run ./bootstrap.sh --with-libraries=filesystem --prefix=/home/jagdish/ commelec_api/installation_dirs/boost - and then, b2 toolset=gcc target-os=windows - finally, i see the following error messages: https://thepasteb.in/p/ y8h6q5Qq1yzcO Did someone encounter the same error messages or can tell me why I'm seeing them? Thanks, Kja

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Re: [Boost-users] NEWBIE: Undefined references: How do I find the library that resolves an undefined reference - Expanded with log example and hope for a general solution
by JENNINGS, LYNN M NH-03 USAF AFMC 517 SMXS/MXDPB 26 Jan '17

26 Jan '17

Thanks again Andy! I am sending this note to thank Andy for his gracious help and to document the resolution for future newbies. Andy's suggestion to "nm -Cg" the boost.log directories was just what I needed! (Sorry, I should have remembered the -C option when I got nothing but garbage.) What I found was that the header files I use, generate a reference to ...::v2s_mt_nt5::..., while the libraries only define the namespace with ...::v2_mt_nt5::... For example, my code has the following: #include <boost\log\core.hpp> #include <boost\log\trivial.hpp> #include <boost\log\expressions.hpp> #include <boost\log\utility\setup\file.hpp> #include <boost\log\utility\setup\common_attributes.hpp> namespace logging = boost::log ; namespace src = boost::log::sources ; namespace keywords= logging::keywords ; namespace sinks = boost::log::sinks ; void init_logger() { logging::add_file_log( "sample.log", keywords::rotation_size = 10 * 1024 * 1024, keywords::time_based_rotation = sinks::file::rotation_at_time_point(0,0,0), keywords::format = "[%TimeStamp%]: %Message%", keywords::auto_flush=true ) ; logging::core::get()->set_filter (logging::trivial::severity >= logging::trivial::info ) ; logging::core::get()->add_global_attribute("TimeStamp", boost::log::attributes::local_clock()); } ... I compiled with the following command from my makefile: cc -g -DCPU=PENTIUM -DMC68000 -DDoing2VxWorks -IC:\boost -I../source -I../include -MMD -MP -c -o obj\logLib.o logLib.cpp Which I built with the following command from my makefile: cc -g -DCPU=PENTIUM -DMC68000 -DDoing2VxWorks -IC:\boost -I../source -I../include -MMD -MP -c -o obj\logLib.o logLib.cpp gfortran -o unit01test.exe obj\unit01test.o ..\mcpmain\obj\rtinit.o ..\mcpmain\obj\bite2.o ..\mcpmain\obj\bmain.o ..\mcpmain\obj\keypm2.o ..\mcpmain\obj\ksvc.o ..\mcpmain\obj\scen1.o ..\mcpmain\obj\disup.o ..\mcpmain\obj\idisup.o ..\mcpmain\obj\keyin.o ..\mcpmain\obj\disdr.o ..\mcpmain\obj\led_task.o ..\mcpmain\obj\spip_task.o ..\mcpmain\obj\iff_task.o ..\mcpmain\obj\inmsgmgr.o ..\mcpmain\obj\cppmainUnit01Test.o ..\runhistory\obj\rhlog_api.o ..\utilities\obj\main2aux.o ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\logLib.o ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\msgQlib.o ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\pciConfigLib.o ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\semLib.o ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\sharedMemLib.o ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\sockLib.o ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\sysLib.o ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\taskLib.o ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\wdLib.o -LC:\boost\stage\lib -lboost_log_setup-mgw48-mt-d-1_61 -lboost_log-mgw48-mt-d-1_61 -lboost_thread-mgw48-mt-d-1_61 -lboost_system-mgw48-mt-d-1_61 -LC:\Windows\SysWOW\en-US -lws2_32 -lstdc++ -lboost_log_setup-mgw48-mt-d-1_61 -lboost_log-mgw48-mt-d-1_61 which gives me the error: ../../vxWorksLib/vxWorksLib/vxWorks/source/obj\logLib.o: In function `Z11init_loggerv': c:\1PortMUTES2MinGW\ProjectRepository-Build\vxWorksLib\vxWorksLib\vxWorks\source/logLib.cpp:16: undefined reference to `boost::log::v2s_mt_nt5::sinks::file::rotation_at_time_point::rotation_at_time_point(unsigned char, unsigned char, unsigned char)' But when I check the nm output, I find the following ::v2_mt_nt5:: namespace defined in all of the various forms of the Boost log libraries: d000608.o: U _head_libboost_log_mgw48_mt_d_1_61_dll 00000000 I _imp___ZNK5boost3log9v2_mt_nt55sinks4file25rotation_at_time_intervalclEv 00000000 T boost::log::v2_mt_nt5::sinks::file::rotation_at_time_interval::operator()() const I built my boost libraries using the directions for a MinGW build. I built my code using the same MinGW framework. However, I found the reason for the two conflicting name spaces, v2_mt_nt5 and v2s_mt_nt5 at: http://www.boost.org/doc/libs/1_56_0/libs/log/doc/html/log/rationale/namesp… The magic key is to recognize the <linkage> name space. I resolved most of my Boost log problem by adding -DBOOST_ALL_DYN_LINK to the compile operation. The correct compile command is: cc -g -DCPU=PENTIUM -DMC68000 -DDoing2VxWorks - DBOOST_ALL_DYN_LINK -IC:\boost -I../source -I../include -MMD -MP -c -o obj\logLib.o logLib.cpp Note that I was able to resolve my remaining errors where gcc just listed the mangled symbol by grep'ing the library file.

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boostcpp.jam: No such file or directory
by JIA Pei 26 Jan '17

26 Jan '17

Hi, all: It seems boost has changed a lot in building? I strictly followed boost *Getting Started on Windows* but when I tried to install boost using command *b2 *. I got the following error messages: D:\boost_1_63_0>C:\boost\bin\b2.exe --build-dir=C:\boost toolset=msvc > --build-type=complete stage > *boostcpp.jam: No such file or directory* > Jamroot:137: in modules.load > ERROR: rule "boostcpp.set-version" unknown in module > "Jamfile<D:\boost_1_63_0>". > D:/boost_1_63_0/tools/build/src/build\project.jam:325: in load-jamfile > D:/boost_1_63_0/tools/build/src/build\project.jam:64: in load > D:/boost_1_63_0/tools/build/src/build\project.jam:145: in project.find > D:/boost_1_63_0/tools/build/src\build-system.jam:535: in load > D:\boost_1_63_0\tools\build\src/kernel\modules.jam:295: in import > D:\boost_1_63_0\tools\build\src/kernel/bootstrap.jam:139: in boost-build > D:\boost_1_63_0\boost-build.jam:17: in module scope > D:\boost_1_63_0> Did anybody meet this issue as well? Most of the time, I work under Linux, which seems to be more convenient.... Cheers -- Pei JIA, Ph.D. Email: jp4work(a)gmail.com cell in Canada: +1 778-863-5816 cell in China: +86 186-8244-3503 Welcome to Vision Open http://www.visionopen.com

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Re: [Boost-users] NEWBIE: Undefined references: How do I find the library that resolves an undefined reference - Expanded with log example and hope for a general solution
by JENNINGS, LYNN M NH-03 USAF AFMC 517 SMXS/MXDPB 26 Jan '17

26 Jan '17

Thanks Richard and Andy for the timely response! Andy's answers provides the perfect example of my dilemma. When Andy said to check the MSDN documentation for ms742213, I quickly found that I needed the Ws2_32.lib library, which I was able to solve my issue. However, I also have the following: 1. boost::log::add_log_file(...) with a sinks::file::rotation_at_time_point(...) 2. boost::random::random_device range; I made a guess with the log and added boost_log_setup_mgw48-mt-d-1_61 and boost_log_ mgw48-mt-d-1_61, but these libraries didn't resolve my issue. When I check the boost documentation (I realize that many of the boost additions just require header files, which the examples are careful to specify. I figure this must require a library because I am getting an undefined error.), there were many mentions of a library, but I couldn't find where the name of the library was specified! So I hope there is a general way to determine the name of the boost library so I do not need to keeping asking about particular undefined errors. In the past, I have been able to google the undefined error and find the library reference, but Thanks again for all of your help! -----Original Message----- On 1/24/2017 3:44 PM, Richard Hodges wrote: > That would be the winsock library. > > https://msdn.microsoft.com/en-us/library/ms740673.aspx > > > > On 24 January 2017 at 20:33, JENNINGS, LYNN M NH-03 USAF AFMC 517 > SMXS/MXDPB <lynn.jennings_at_[hidden]> wrote: > >> NEWBIE question: Undefined references: How do I find the library that >> resolves an undefined reference. For example, the output for the gcc >> linker running in MinGW shows: >> >> C:/boost/boost/asio/detail/impl/winsock_init.ipp:39: Undefined reference >> to `WSAStartup_at_8' >> >> I have googled the documentation a number of ways, but I cannot find the >> library that will resolve this error. I am sure that this is a common >> problem. Please point me to the documentation so I can fix this and the >> undefined references. >> >> Thanks! In the future, you can check Microsoft's documentation [1] for info on their functions. I searched for "WSAStartup", and found [2]. At the bottom of that page is a "Requirements" box, which tells you the library it's in. Andy 1. http://msdn.microsoft.com 2. https://msdn.microsoft.com/en-us/library/windows/desktop/ms742213(v=vs.85).…

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circular_buffer: rotate() vs erase_begin() for scalars
by Robert Dailey 25 Jan '17

25 Jan '17

I'm using circular_buffer to represent a FIFO queue of bytes: boost::circular_buffer<std::uint8_t> m_queue; When I read bytes from the "front", I simply do: m_queue.erase_begin(num_read_bytes); I do so because the documentation for erase_begin() specifically mentions constant time performance for scalar types since no destructor needs to be called. However, I feel that rotate() better expresses what I'm trying to do. Is there a reason to prefer one over the other for scalar types?

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C++Now / BoostCon 2017 -- Call For Submissions
by Michael Caisse 23 Jan '17

23 Jan '17

This is a quick reminder that the C++Now 2017 Call For Submissions is *open*. All submissions must be made by February 3rd. For more information, see http://cppnow.org/

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How to build Boost with Clang/libc++ and NOT link against libstdc++?
by Deniz Bahadir 20 Jan '17

20 Jan '17

Hi guys, I am struggling with building the Boost (1.58.0) libraries with Clang (3.8) and libc++ (on Ubuntu 16.04). I am able to build the Boost libraries using Clang and flags "-std=c++14 -stdlib=libc++", however, I noticed that several libraries are still linked against GCC's standard-library "libstdc++". I then tried adding the flag "-lc++abi" (later I tried "-Wl,-lc++abi") to Boost.Build options "cxxflags" and "linkflags" to explicitly link against "libc++abi". With no luck. Several boost-libraries are still linked against "libstdc++". Does anyone know how and why this link-dependency gets added and how to get rid of them? Does it come in through some other link-dependencies? At least none of them seem to link to "libstdc++"? The Boost shared-libraries that link to "libstdc++" are: libboost_chrono-clang38-mt-1_58_0.so.1.58.0 libboost_context-clang38-mt-1_58_0.so.1.58.0 libboost_coroutine-clang38-mt-1_58_0.so.1.58.0 libboost_date_time-clang38-mt-1_58_0.so.1.58.0 libboost_filesystem-clang38-mt-1_58_0.so.1.58.0 libboost_graph-clang38-mt-1_58_1.so.0.58.0 libboost_iostreams-clang38-mt-1_58_0.so.1.58.0 libboost_locale-clang38-mt-1_58_0.so.1.58.0 libboost_log-clang38-mt-1_58_0.so.1.58.0 libboost_log_setup-clang38-mt-1_58_0.so.1.58.0 libboost_math_tr1-clang38-mt-1_58_0.so.1.58.0 libboost_math_tr1f-clang38-mt-1_58_0.so.1.58.0 libboost_math_tr1l-clang38-mt-1_58_0.so.1.58.0 libboost_program_options-clang38-mt-1_58_0.so.1.58.0 libboost_python-clang38-mt-1_58_0.so.1.58.0 libboost_random-clang38-mt-1_58_0.so.1.58.0 libboost_regex-clang38-mt-1_58_0.so.1.58.0 libboost_signals-clang38-mt-1_58_0.so.1.58.0 libboost_thread-clang38-mt-1_58_0.so.1.58.0 libboost_timer-clang38-mt-1_58_0.so.1.58.0 libboost_unit_test_framework-clang38-mt-1_58_0.so.1.58.0 libboost_wave-clang38-mt-1_58_0.so.1.58.0 The once that are fine and do not link against "libstdc++" are: libboost_atomic-clang38-mt-1_58_0.so.1.58.0 libboost_container-clang38-mt-1_58_0.so.1.58.0 libboost_math_c99-clang38-mt-1_58_0.so.1.58.0 libboost_math_c99f-clang38-mt-1_58_0.so.1.58.0 libboost_math_c99l-clang38-mt-1_58_0.so.1.58.0 libboost_serialization-clang38-mt-1_58_0.so.1.58.0 libboost_system-clang38-mt-1_58_0.so.1.58.0 libboost_wserialization-clang38-mt-1_58_0.so.1.58.0 Interestingly, all libraries are also linked against "libc++abi" except for: libboost_atomic-clang38-mt-1_58_0.so.1.58.0 libboost_container-clang38-mt-1_58_0.so.1.5 For completeness, my build-command is this: cd /home/jenkins/workspace/Pipeline_Boost/sources/boost_1_58_0 LINK_LIBCXXABI="-Wl,-lc++abi" COMMON_COMPILER_FLAGS="-m64 -fpic -fdiagnostics-color=always -O3" CFLAGS="$COMMON_COMPILER_FLAGS" CXXFLAGS="$COMMON_COMPILER_FLAGS -std=c++14 -stdlib=libc++ -isystem/usr/include/libcxxabi $LINK_LIBCXXABI" CC=/usr/bin/clang-3.8 CXX=/usr/bin/clang++-3.8 /home/jenkins/workspace/Pipeline_Boost@3/clang38/build/boost-build/b2 -j1 -q \ --build-dir=/home/jenkins/workspace/Pipeline_Boost@3/clang38/build/boost \ --build-type=minimal --layout=versioned address-model=64 install \ --prefix=/home/jenkins/workspace/Pipeline_Boost@3/clang38/installed/opt/BENOCS/clang38 \ --libdir=/home/jenkins/workspace/Pipeline_Boost@3/clang38/installed/opt/BENOCS/clang38/lib/x86_64-linux-gnu \ dll-path==/opt/BENOCS/clang38/lib/x86_64-linux-gnu \ toolset=clang-3.8 \ cflags="$CFLAGS" CXXFLAGS="$CXXFLAGS" \ linkflags="-Wl,--as-needed $LINK_LIBCXXABI" For the environment-variable LINK_LIBCXXABI I tried "-lc++abi" as well and also tried providing it only in the cxxflags or the linkflags or both (as above). I would be happy, if anyone could explain that behavior or could even provide a workaround/fix for me, so that "libstdc++" is no longer linked. Thanks, Deniz PS: BTW, does anyone know if it is correct, that shared libraries (in general) that are linked against "libc++abi" do always also link to "libgcc_s"? (What is it for?) -- BENOCS GmbH Dipl.-Inform. Deniz Bahadir Winterfeldtstr. 21 10781 Berlin Germany Phone: +49 - 30 / 577 0004-22 Email: deniz.bahadir(a)benocs.com www.benocs.com Board of Management: Michael Wolz, Dr.-Ing. Oliver Holschke, Dr.-Ing. Ingmar Poese Commercial Register: Amtsgericht Bonn HRB 19378

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Fwd: Boost coroutine/context libraries
by Gregory Laird 20 Jan '17

20 Jan '17

--------------- Forwarded message (begin) Subject: Boost coroutine/context libraries From: Gregory Laird <glaird(a)northgatebowl.com> Date: Tue, 17 Jan 2017 17:10:57 -0800 Newsgroup: gmane.comp.lib.boost.user I am trying to write a cooperative task scheduler in c++ and I have discovered the boost context and coroutine libraries. I have written these sorts of schedulers many times in assembly language so I appreciate the issues in the methodology. I have written lots of c code but am less versed in c++. I have been trying to find some straightforward examples of the libraries use without a lot of extraneous c++ language elements (e.g. binds, lambdas, etc.). I did find one example http://stackoverflow.com/questions/11716291/boost-context-class that is very nice, but it will not compile now with the current boost library. I get an error saying that boost::context::fcontext_t has been removed from the public api. Could someone direct me to some examples that demonstrate the context or coroutine functionality that would be easier to understand. I want to write a scheduler that is very similar to the example listed above where coroutines yeild back to a main caller which then chooses the next coroutine to continue its processing. Thanks. --------------- Forwarded message (end)

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