March 2015 - Boost-users - lists.preview.boost.org

Re: [Boost-users] [heap] Mix use of size_t and size_type
by Cheng Mo 12 Mar '15

12 Mar '15

>Hi, >While reading d_ary_heap.hpp from the heap library I was surprised to >see a mix of size_t and size_type variables in an index computation >(https://github.com/boostorg/heap/blob/master/include/boost/heap/d_ary_heap.…): > size_type last_child_index(size_type index) const > { > const size_t first_index = first_child_index(index); > const size_type last_index = (std::min)(first_index + D - 1, >size() - 1); > return last_index; > } >Isn't this a typo? >-- >Matthias Hi Matthias: I am not really reading d_ary_heap.hpp actually. As my experiences the size_type is used as the parameter in template programming. It's not a confirmed type and it is depended on what you transmit the value of type while you build template function. It could be "int, short, unsigned things even the customized type". It seems to be confirmed during compiling. In another hand, size_t is used "typedef", it is as a definition and will be confirmed during preprocessing. It has could be unsigned int, not always, but often. I hope it is helpful. 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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[Filesystem] Issue about current_path() function, is it removed ?
by Cheng Mo 12 Mar '15

12 Mar '15

Hi all: I have found there have been no "current_path()" in filesystem scope, isn't ? Is there any other function instead it What if I want to get the current_path value ? current_path() 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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Re: [Boost-users] [heap] Mix use of size_t and size_type
by Cheng Mo 12 Mar '15

12 Mar '15

Hi Ben: >> It could be "int, short, unsigned things even the customized type". It >> seems to be confirmed during compiling. >> In another hand, size_t is used "typedef", it is as a definition and >> will be confirmed during preprocessing. > As a typedef, compile time, after the preprocessor. Thanks for that. I had mistake about this before. 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 1.57.0 Message Queue Remove
by SPONZA Cristiano (MM) 11 Mar '15

11 Mar '15

Hi, about this topic I would have two questions. The scenario is simple: 1 sender and 1 receiver sharing a boost message queue. Q1: If the sender removes the queue by the function remove("myQueue") how can the receiver to be aware the queue no longer exists? In my implementation the receiver uses the function timed_receive(...) and if the sender removes the queue the function returns false, since timeout is reached. The problem, in my case, is that the receiver cannot tell if the queue has been deleted or the sender is not sending messages anymore. Q2: I experience a different behavior of the receiver depending on the language, C or C++. Actually I created two receivers: recv.c and recv.cpp. The sender is written in C++. The operations sequence is the following: Sender: - creates the queue "myQueue" - writes some messages - removes the queue - terminates Receiver: - loops reading message on the queue "myQueue", applying timeout Sender: - restarts - creates the queue "myQueue" - ... When the sender terminates, the receiver keeps to try reading. The queue has been removed, so the timed_receive(...) function goes in timeout. When I restart the sender, the C++ receiver properly resumes reading the messages . With the C version, instead, the receiver is not able to resume and the receive function keeps going in timeout. Why the C++ version resumes while the C doesn't? If the sender terminates leaving the queue as it is and then restarts, the C receiver resumes properly. Unfortunately the implementation requires that if the sender has to terminate for any reason, the queue must be removed. I hope I've been clear enough. Thank you very much. ________________________________ VISITA IL NOSTRO NUOVO SITO WEB! - VISIT OUR NEW WEB SITE! www.magnetimarelli.com Confidential Notice: This message - including its attachments - may contain proprietary, confidential and/or legally protected information and is intended solely for the use of the designated addressee(s) above. If you are not the intended recipient be aware that any downloading, copying, disclosure, distribution or use of the contents of the above information is strictly prohibited. If you have received this communication by mistake, please forward the message back to the sender at the email address above, delete the message from all mailboxes and any other electronic storage medium and destroy all copies. Disclaimer Notice: Internet communications cannot be guaranteed to be safe or error-free. Therefore we do not assure that this message is complete or accurate and we do not accept liability for any errors or omissions in the contents of this message.

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[Log] fork safety and core::set_logging_enabled(false)
by Алексей Филиппов 11 Mar '15

11 Mar '15

Hi, I am developing a project which executes some non-trivial code after fork and before exec. This code contains logging statements "BOOST_LOG_TRIVIAL(..)". I know that Boost.Log is not safe to use in child created by fork, but it this particular case it is fine to just disable logging in child process to make it safe. However I would prefer to keep these logging statements and disable logging somehow else, like setting some global flag. There is a boost::log::core::set_logging_enabled() function which seems to be the solution to this problem. Documentation says: "Setting this status to false allows you to completely wipe out any logging activity, including filtering and generation of attribute values." Unfortunately there is no note about fork safety. The question is: Is it safe to use it to disable logging in child process, even if application will try to execute log statements? Below is simple code sample. ---- #include <boost/log/trivial.hpp> #include <sys/wait.h> #include <unistd.h> void f(const char *const key) { BOOST_LOG_TRIVIAL(info) << "Some logic: " << key; } int main() { BOOST_LOG_TRIVIAL(info) << "Begin of app"; f("main"); const pid_t pid = fork(); if (pid < 0) _exit(127); if (pid > 0) { // parent BOOST_LOG_TRIVIAL(info) << "Child: " << pid; f("after-fork main"); } else { // child boost::log::core::get()->set_logging_enabled(false); // logging by other functions, is it safe? f("after-fork child"); _exit(0); } int stat_loc; const pid_t rpid = ::wait(&stat_loc); BOOST_LOG_TRIVIAL(info) << "End of app, reaped " << rpid; } ---- Any help would be greatly appreciated, Aleksey

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Syslog Message Field
by Michael Peters 11 Mar '15

11 Mar '15

A question for those who are familiar with the Logging/Syslog functions in boost. I am currently experimenting with boost 1_57_0. Compiling with MSVC++ 12.0 I am using the example for syslog https://github.com/boostorg/log/blob/master/example/syslog/main.cpp Relevant Example Code Snippet sink->set_formatter ( expr::format("syslog.exe: %1%: %2%") % expr::attr< unsigned int >("RecordID") % expr::smessage ); // We'll have to map our custom levels to the syslog levels sinks::syslog::custom_severity_mapping< severity_levels > mapping("Severity"); mapping[normal] = sinks::syslog::info; mapping[warning] = sinks::syslog::warning; mapping[error] = sinks::syslog::critical; sink->locked_backend()->set_severity_mapper(mapping); // Set the remote address to sent syslog messages to sink->locked_backend()->set_target_address("localhost"); // Add the sink to the core logging::core::get()->add_sink(sink); // Add some attributes too logging::core::get()->add_global_attribute("RecordID", attrs::counter< unsigned int >()); // Do some logging src::severity_logger< severity_levels > lg(keywords::severity = normal); BOOST_LOG_SEV(lg, normal) << "A syslog record with normal level"; BOOST_LOG_SEV(lg, warning) << "A syslog record with warning level"; BOOST_LOG_SEV(lg, error) << "A syslog record with error level"; For some reason the Timestamp and Source machine name is being added to the start of Message field. So the syslog message field looks something like this: Mar 10 23:23:47 pluto syslog.exe: 0: A syslog record with normal level When I would expect the message field to look like this: syslog.exe: 0: A syslog record with normal level I have tested with both Kiwi Syslog and Syslog Watcher software for Windows on different PC’s running different OS’s and both behave in the same way. All other devices that log to the Syslog server correctly format the message field. Is there a hidden attribute (source machine name and timestamp) that I am not aware of that is being added to the message text? Is the Syslog server software perhaps receiving what it considers to be an incorrectly formatted message and is therefore corrupting the message field? Any suggestions / thoughts on what to check would be appreciated. Mike

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[Interprocess] Using existing containers after grow()
by Malko 10 Mar '15

10 Mar '15

Hi, I am having some difficulties understanding the relationship between allocators for containers and grow(). Let's say I create a vector (whatever type) in shmem, then I unmap everything and proceed to grow the shmem from 1MB to 2MB and remap. I can now access my old vector and start adding new entries. What I am unsure about is: would this vector be able to create new entries until the whole 2MB are allocated, or would it stop at 1? I have not seen anywhere in the docs any warning about the need to construct new containers after a grow, so I assume my vector can grow up to to 2MB now. Then my question is: how does it know that now it can grow up to 2MB if the allocator I passed on construction was instantiated from a segment_manager that knew about a shmem of size 1MB? Is there somewhere in shared memory a segment_manager-like object that stores info about the shmem itself (and can I access it in my code)? Any help would be greatly appreciated, Malko

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[heap] Mix use of size_t and size_type
by Matthias Meulien 09 Mar '15

09 Mar '15

Hi, While reading d_ary_heap.hpp from the heap library I was surprised to see a mix of size_t and size_type variables in an index computation (https://github.com/boostorg/heap/blob/master/include/boost/heap/d_ary_heap.…): size_type last_child_index(size_type index) const { const size_t first_index = first_child_index(index); const size_type last_index = (std::min)(first_index + D - 1, size() - 1); return last_index; } Isn't this a typo? -- Matthias

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[boost.geometry] buffer distance strategies
by gchlebus 09 Mar '15

09 Mar '15

Hi, I am wondering whether it would be possible to achieve anisotropic buffering (distances in neg x, pos x, neg y, pos y can have different values) of a polygon using the buffer function with custom-implemented distance strategy. What I want to achieve is presented on the figure 2-b in the following paper: http://itcnt05.itc.nl/agile_old/Conference/mallorca2002/proceedings/posters… I would be grateful to hear from you whether it is doable, and if positive, how one could implement such a custom distance strategy. Best, -- View this message in context: http://boost.2283326.n4.nabble.com/boost-geometry-buffer-distance-strategie… Sent from the Boost - Users mailing list archive at Nabble.com.

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multi_index: iterator_to complexity
by Matwey V. Kornilov 09 Mar '15

09 Mar '15

Hi, The following two calls have constant complexity (according to docs) for all indices: iterator iterator_to(const value_type& x); const_iterator iterator_to(const value_type& x) const; As far as I understand, the single way to reach the constant complexity in searching by pointer is to store the objects in continuous memory area. Is it correct?

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Flood of messages when building with boost_serialization
by Tony Camuso 09 Mar '15

09 Mar '15

Using Fedora 21 64 bit gcc 4.9.2 Qt Creator 3.2.1 Qt 5.3.2 When I run make from the command line, all is well. $ g++ -Wall -c kabi-serial.cpp -lboost_serialization ### no errors ### Even if I build the whole project from the command line, there are no errors. $ g++ -Wall -o kabi-parser -x c kabi.c -x c checksum.c -x c++ kabi-node.cpp -x c++ kabi-serial.cpp -lboost_serialization -lsparse However, when I build it from Qt, I get the following compiler output. I understand the "unused parameter" message, as I'm not using versioning in my serialization implementation. I haven't tried executing the serialization code, yet, but I wonder if it will even execute properly, given the nature of the messages. The rest of the code executes fine. The serialization code is very simple and follows the messages. 20:38:17: Starting: "/usr/bin/make" kabi-serial.o g++ -c -pipe -g -Wall -W -fPIE -I/home/tcamuso/Qt5.3.2/5.3/gcc_64/mkspecs/linux-g++ -I../../kabi -I../src/sparse -I../src/sparse -I. -o kabi-serial.o ../src/kabi-serial.cpp In file included from ../src/kabi-serial.cpp:14:0: ../src/kabi-serial.h: In instantiation of 'void Cqnodelist::serialize(Archive&, unsigned int) [with Archive = boost::archive::text_oarchive]': /usr/include/boost/serialization/access.hpp:118:9: required from 'static void boost::serialization::access::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive; T = Cqnodelist]' /usr/include/boost/serialization/serialization.hpp:69:69: required from 'void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive; T = Cqnodelist]' /usr/include/boost/serialization/serialization.hpp:128:27: required from 'void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive; T = Cqnodelist]' /usr/include/boost/archive/detail/oserializer.hpp:152:5: required from 'void boost::archive::detail::oserializer<Archive, T>::save_object_data(boost::archive::detail::basic_oarchive&, const void*) const [with Archive = boost::archive::text_oarchive; T = Cqnodelist]' /usr/include/boost/archive/detail/oserializer.hpp:101:1: required from 'class boost::archive::detail::oserializer<boost::archive::text_oarchive, Cqnodelist>' /usr/include/boost/archive/detail/oserializer.hpp:253:13: [ skipping 2 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ] /usr/include/boost/archive/detail/oserializer.hpp:314:44: required from 'static void boost::archive::detail::save_non_pointer_type<Archive>::invoke(Archive&, T&) [with T = Cqnodelist; Archive = boost::archive::text_oarchive]' /usr/include/boost/archive/detail/oserializer.hpp:525:24: required from 'void boost::archive::save(Archive&, T&) [with Archive = boost::archive::text_oarchive; T = Cqnodelist]' /usr/include/boost/archive/detail/common_oarchive.hpp:69:40: required from 'void boost::archive::detail::common_oarchive<Archive>::save_override(T&, int) [with T = Cqnodelist; Archive = boost::archive::text_oarchive]' /usr/include/boost/archive/basic_text_oarchive.hpp:80:9: required from 'void boost::archive::basic_text_oarchive<Archive>::save_override(T&, int) [with T = Cqnodelist; Archive = boost::archive::text_oarchive]' /usr/include/boost/archive/detail/interface_oarchive.hpp:63:9: required from 'Archive& boost::archive::detail::interface_oarchive<Archive>::operator<<(T&) [with T = Cqnodelist; Archive = boost::archive::text_oarchive]' ../src/kabi-serial.cpp:42:9: required from here ../src/kabi-serial.h:54:50: warning: unused parameter 'version' [-Wunused-parameter] void serialize(Archive & ar, const unsigned int version) ^ 20:38:17: The process "/usr/bin/make" exited normally. 20:38:17: Elapsed time: 00:00. ------------- source code ---------------------- #include <boost/serialization/vector.hpp> #include <boost/archive/text_oarchive.hpp> using namespace std; namespace boost { namespace serialization { class Cqnodelist { public: friend class boost::serialization::access; Cqnodelist(){} vector<int>qnodelist; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & qnodelist; } }; void kb_write_list () { Cqnodelist ql; ofstream ofs("kabi-list.dat"); { boost::archive::text_oarchive oa(ofs); oa << ql; } } } // namespace serialization } // namespace boost

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multi_index: thread safety
by Matwey V. Kornilov 08 Mar '15

08 Mar '15

Hi, I have a multi_index container and would like to make concurrent READs. Is it thread-safe? I mean that there could be mutable members inside the object, so calling formally const functions leaded to concurrent writes.

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Call for Papers Meeting C++ 2015
by Jens Weller 05 Mar '15

05 Mar '15

Hello boost community! I'd like to inform you that the call for papers for this years Meeting C++ conference is running! It will end at April 5th, boost related talks are very welcome! This years conference will be again at the Andels Hotel in Berlin, on the 4th and 5th december. It will feature 2 keynotes and 4 Tracks a 7 Talks, this years theme track is "embedded and IoT". There is again also a student program, which will be announced later. Call for Papers: http://meetingcpp.com/index.php/newsreader/items/call-for-papers-for-meetin… Announcement: http://meetingcpp.com/index.php/newsreader/items/announcing-meeting-c-2015.… kind regards, Jens Weller

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Boost integration with VxWorks
by Hashemian, Mehdi 04 Mar '15

04 Mar '15

Hello, May the Maintainer please kindly contact me? I need help to investigate how to provide an official port of Boost for VxWorks Operating Systems so that it works out of the box. Best Regards, Mehdi Hashemian, Product Manager, Wind River

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Statechart serialization
by mbrodeur65 04 Mar '15

04 Mar '15

Hi, I'm looking for a solution to serialize boost::statechart objects. I'm aware that this feature is on the statechart library todo list but was wondering if there are any workaround to achieve this with the latest boost release (1.34) ? thanks for your help ! mbrodeur65 -- View this message in context: http://www.nabble.com/Statechart-serialization-tf4131326.html#a11749139 Sent from the Boost - Users mailing list archive at Nabble.com.

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Bus Error 10 on Mac OS
by Vinay Kumar 04 Mar '15

04 Mar '15

Hi, We are using boost libraries(version 1.56.0) in our application(32bit application). Our application crashes only Mac OS(10.8) platform with Bus Error 10. $gdb ./ourapp core.xxx GNU gdb 6.3.50-20050815 (Apple version gdb-1705) (Fri Jul 1 10:50:06 UTC 2011) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-apple-darwin"...Reading symbols for shared li braries ........ done Core was generated by `./ourapp'. Reading symbols for shared libraries . done Reading symbols for shared libraries ........................................... ................................................................................ ............ done #0 0x98218aa2 in __semwait_signal () (gdb) bt #0 0x98218aa2 in __semwait_signal () #1 0x9821875e in _pthread_cond_wait () #2 0x9821a3f8 in pthread_cond_wait$UNIX2003 () #3 0x0000f1f1 in std::_Rb_tree<std::string, std::string, std::_Identity<std::string>, std::less<std::string>, std::allocator<std::string> >::_M_erase () #4 0x0000b6f4 in ?? () #5 0x000025a1 in ?? () #6 0x0000af63 in ?? () #7 0x00002035 in ?? () (gdb) t 2 (gdb) bt #0 0x98218aa2 in __semwait_signal () #1 0x9821875e in _pthread_cond_wait () #2 0x9821a3f8 in pthread_cond_wait$UNIX2003 () #3 0x0000f1f1 in std::_Rb_tree<std::string, std::string, std::_Identity<std::string>, std::less<std::string>, std::allocator<std::string> >::_M_erase () #4 0x0000b6f4 in ?? () #5 0x00016206 in boost::exception_detail::set_info<boost::exception_detail::clone_impl<boost::exception_detail::bad_alloc_> > () #6 0x0001ce4e in std::vector<std::string, std::allocator<std::string> >::_M_insert_aux () #7 0x0001cdb9 in std::vector<std::string, std::allocator<std::string> >::_M_insert_aux () #8 0x0001cd1c in std::vector<std::string, std::allocator<std::string> >::_M_insert_aux () #9 0x0001caaf in std::vector<std::string, std::allocator<std::string> >::_M_insert_aux () #10 0x001dba1b in boost::this_thread::get_id () #11 0x001db13c in boost::this_thread::get_id () #12 0x0087866e in icu_44::ServiceListener::~ServiceListener () #13 0x98218259 in _pthread_start () #14 0x982180de in thread_start () Can anybody explain the root cause of the problem? This crash happens only on Mac OS. While building boost libraries on Mac OS, do we need to set any extra flags? NOTE: Our application runs successfully on other platforms without any problem. Regards,Vinay

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[gsoc15] Boost will be a mentoring org for 2015
by Niall Douglas 03 Mar '15

03 Mar '15

Dear Boost. I am very pleased to report that Boost has been accepted as a GSoC org for 2015. Student applications begin on Monday March 16th, in just under two weeks, and last ten days until Friday March 27th. If you haven't added your proposal ideas to https://svn.boost.org/trac/boost/wiki/SoC2015, now is the time to do so. If you would like to add your name to the ten other mentors who have made themselves available this summer, please do get in contact. Niall and Boris --- Boost C++ Libraries Google Summer of Code 2015 admin https://svn.boost.org/trac/boost/wiki/SoC2015

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Re: [Boost-users] [Asio] run_one does not seem to run signal handler but run does
by Robert Valkenburg 02 Mar '15

02 Mar '15

Thanks for the clarification, On Mon, Mar 2, 2015 at 11:29 AM, Gavin Lambert <gavinl(a)compacsort.com> wrote: > > "One handler" does not necessarily mean "one application code handler". > Many high-level async operations are actually composed internally of a > sequence of lower-level operations. As such, it may require multiple > internal handler calls before your user-level handler is actually called. > > From your output, it appears that it your case it actually requires two > handler calls to actually invoke your application handler. However you > should not rely on this as it may change if the internals of Asio change or > if some other condition in your execution environment changes. Ok, so this explains the 6, and also explains the 1 for the run_one() test (i.e. my handler did not get invoked). I added run_one() a second time (with reset() in between) and my handler was invoked and count equals 1 as expected . > > run_one() is intended to be called in a loop with other "idle" work -- but > using run() is preferred whenever you can just post the extra work to the > io_service anyway. Ok, this is helpful. > > Note that an async_wait is a single-shot thing anyway -- if you didn't call > async_wait again in your handler then it would only catch the signal once, > if that's what you're trying to do. Yes. This was only a small test program to help me understand ASIO better. I was trying to use CTRL C was a mechanism to introduce a console event (also looked at posix::stream_descriptor) into the mix of socket (android) and serial port (arduino) events. thanks again.

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[msm] Stuck in pseudo exit
by Chrisopher Vogl 02 Mar '15

02 Mar '15

Hi all, I have got a sub state machine (called Calibrate) which is exited via a pseudo exit on an event called Ev_Exit. The event is triggered on the return of a synchronous D-Bus call. So far everything works fine. Now I wanted to use an async D-Bus call and trigger the event in the finished-handler of the asynchronous D-Bus call. I can see that the event is released and that the transition into the pseudo exit takes place but the control is not given back to the outer state machine, i.e. the following transition in the outer state machine is not executed: Row < Calibrate::exit_pt<PseudoExit> , Ev_Exit , CheckNFC , none , none >, Instead I get the log output that there is no transition for event Ev_Exit in the sub machine: user.notice tm-calibration: void hale::tmop::Calibration_::Calibrate_::CheckKconst::on_exit(const Event&, FSM&) [with Event = hale::tmop::Ev_Exit; FSM = boost::msm::back::state_machine<hale::tmop::Calibration_::Calibrate_>] user.notice tm-calibration: void hale::tmop::PseudoExit::on_entry(const Event&, FSM&) [with Event = hale::tmop::Ev_Exit; FSM = boost::msm::back::state_machine<hale::tmop::Calibration_::Calibrate_>] user.notice tm-calibration: void hale::tmop::Calibration_::Calibrate_::no_transition(const Event&, FSM&, int) [with FSM = boost::msm::back::state_machine<hale::tmop::Calibration_::Calibrate_>; Event = hale::tmop::Ev_Exit], No transition from state I get the same behaviour when I try to use Glib's signal_timeout() to generate timeout events in a sub machine. Then the sub machine gets also stuck in the pseudo exit. I'm using boost 1.53. The program is not multi-threaded and I'm using Glib's main loop. Part of transition table in sub machine called Calibrate: ... Row < CheckKconst , Ev_Exit , PseudoExit , none , is_exit_ok >, Row < CheckKconst , Ev_Exit , ShowDesc , showImpError , is_exit_error >, ... with enum ExitReason { EXIT_REASON_NONE, EXIT_REASON_OK, EXIT_REASON_TIMEOUT, EXIT_REASON_ERROR }; struct Ev_Exit { ExitReason exitReason_; std::string message_; int code_; Ev_Exit() : exitReason_( EXIT_REASON_NONE ), code_( 0 ) {} Ev_Exit( ExitReason exitReason, std::string message = "", int code = 0 ) : exitReason_( exitReason ), message_( message ), code_( code ) {} template <class Event> Ev_Exit( Event const& ) : exitReason_( EXIT_REASON_NONE ), code_( 0 ) {} }; struct is_exit_ok { template <class EVT, class FSM, class SourceState, class TargetState> bool operator()( EVT const& evt, FSM& fsm, SourceState& ss, TargetState& ts ) { return evt.exitReason_ == EXIT_REASON_OK; } }; struct PseudoExit : public msm::front::exit_pseudo_state<Ev_Exit> { template <class Event,class FSM> void on_entry( Event const& evt, FSM& fsm ) {} template <class Event,class FSM> void on_exit( Event const& evt, FSM& fsm ) {} };

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[Asio] run_one does not seem to run signal handler but run does
by Robert Valkenburg 01 Mar '15

01 Mar '15

Hi, I am reasonably new to Boost.Asio. Below is a short test program to catch CNTR C. It nearly works as i would have expected. #include <iostream> #include <boost/version.hpp> #define BOOST_ASIO_ENABLE_HANDLER_TRACKING #include <boost/asio.hpp> namespace asio = boost::asio; #define GCC_VERSION (__GNUC__*10000 + __GNUC_MINOR__*100 + __GNUC_PATCHLEVEL__ ) struct Sig_handler { Sig_handler(int& count, asio::signal_set& signals) : count_(count), signals_(signals) {} void operator()(const boost::system::error_code& ec, int signal_number) { if (!ec) { count_++; std::cout << "signal: " << signal_number << std::endl; if (count_ < 3) signals_.async_wait( Sig_handler(count_, signals_)); } else { std::cout << "Sig_handler error" << std::endl; } } int& count_; asio::signal_set& signals_; }; int main() { std::cout << "test_asio_sig starting " << std::endl; std::cout << "GCC VERSION " << GCC_VERSION << std::endl; std::cout << "BOOST VERSION " << BOOST_VERSION << std::endl; asio::io_service io_service; asio::signal_set signals(io_service, SIGINT); int count = 0; std::cout << "count " << count << std::endl; signals.async_wait( Sig_handler(count, signals) ); size_t num_handlers = io_service.run(); // size_t num_handlers = io_service.run_one(); // <<== NOTE std::cout << "num handlers " << num_handlers << std::endl; std::cout << "count " << count << std::endl; std::cout << "test_asio_sig finishing " << std::endl; } Here is the output after pressing CNTR C 3 times [robert@localhost misc]$ ./test_asio_sig test_asio_sig starting GCC VERSION 40902 BOOST VERSION 105700 count 0 @asio|1425176527.462503|0*1|signal_set@0x7fffcd9139b8.async_wait ^C(a)asio|1425176530.453067|>1|ec=system:0,signal_number=2 signal: 2 @asio|1425176530.453092|1*2|signal_set@0x7fffcd9139b8.async_wait @asio|1425176530.453102|<1| ^C(a)asio|1425176533.749159|>2|ec=system:0,signal_number=2 signal: 2 @asio|1425176533.749187|2*3|signal_set@0x7fffcd9139b8.async_wait @asio|1425176533.749191|<2| ^C(a)asio|1425176548.261061|>3|ec=system:0,signal_number=2 signal: 2 @asio|1425176548.261092|<3| num handlers 6 count 3 test_asio_sig finishing @asio|1425176548.261116|0|signal_set@0x7fffcd9139b8.cancel [robert@localhost misc]$ I don't understand why io_service.run() says 6 handlers where invoked but otherwise it seems OK. Now if i replace io_service.run() with io_service.run_one() i expected the handler to be invoked once when CNTR C is pressed. Here is the output [robert@localhost misc]$ ./test_asio_sig test_asio_sig starting GCC VERSION 40902 BOOST VERSION 105700 count 0 @asio|1425176928.548934|0*1|signal_set@0x7fffe64b8398.async_wait ^Cnum handlers 1 count 0 test_asio_sig finishing @asio|1425176930.187377|0|signal_set@0x7fffe64b8398.cancel @asio|1425176930.187411|~1| [robert@localhost misc]$ This suggests one handler was invoked which is what i might have expected. This does not have a line with >1 indicating entering the handler and there is no output from the handler and count remains at 0. Could someone help me to understand this. [ I am using Fedora 21, gcc 4.9.2, x86_64, boost 1.57 ] kind regards

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