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How to set std :: ios_base flags like std :: left in boost log 2.0?

I have an application that makes extensive use of boost log 2.0. Now I would like to set some default flags for this application, for example std::setprecision(std::numeric_limits<double>::digits10 + 1), std::scientificand std::left. But how do I do this? One approach is to create a logger at the very beginning of my main function and create a dummy log message. This constantly sets the necessary flags. But is there a better way to do this?

change in response to: "The OP shall show the actual code."

I have a global singleton Logging called L:

class L{
public:
  enum severity_level
  {
      dddebug,
      ddebug,
      debug,
      control,
      iiinfo,
      iinfo,
      info,
      result,
      warning,
      error,
      critical
  };

  typedef boost::log::sources::severity_channel_logger<
      severity_level, // the type of the severity level
      std::string // the type of the channel name
  > logger_t;
  typedef boost::log::sinks::synchronous_sink< boost::log::sinks::text_ostream_backend > text_sink;
  boost::shared_ptr< text_sink > sink_;

  static L& get();
  static boost::shared_ptr<text_sink> sink();
  static double t0();
  static double tElapsed();
private:
  L();
  double t0_p;
  static std::string tElapsedFormat();

  L(const L&) = delete;
  void operator=(const L&) = delete;
};

, MPI MPI. :

#include "log.h"

#include <iomanip>
#include <limits>
#include <fstream>
#include <boost/log/attributes/function.hpp>
#include <boost/smart_ptr/shared_ptr.hpp>
#include <boost/smart_ptr/make_shared_object.hpp>
#include <boost/log/core.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/sources/severity_channel_logger.hpp>
#include <boost/log/sinks/sync_frontend.hpp>
#include <boost/log/sinks/text_ostream_backend.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>


namespace logging = boost::log;
namespace src = boost::log::sources;
namespace expr = boost::log::expressions;
namespace sinks = boost::log::sinks;
namespace attrs = boost::log::attributes;
namespace keywords = boost::log::keywords;

#include "mpiwrap.h"
#include <mpi.h>

BOOST_LOG_ATTRIBUTE_KEYWORD(t, "Time", std::string)
BOOST_LOG_ATTRIBUTE_KEYWORD(rank, "Rank", int)
BOOST_LOG_ATTRIBUTE_KEYWORD(channel, "Channel", std::string)
BOOST_LOG_ATTRIBUTE_KEYWORD(severity, "Severity", L::severity_level)

L::L():
  sink_(boost::make_shared< text_sink >()),
  t0_p(MPI_Wtime())
{

  sink_->locked_backend()->add_stream(
    boost::make_shared< std::ofstream >("log." + std::to_string(MpiWrap::getRank())));

  sink_->set_formatter
  (
    expr::stream
      << "< "
      << t << " "
      << "[p:" << rank << "] "
      << "[c:" << channel << "] "
      << "[s:" << severity << "] "
      << expr::smessage
  );

  logging::core::get()->add_sink(sink_);

  logging::core::get()->set_filter(

       (channel == "ChannelName1" && severity >= dddebug)
    || (channel == "ChannelName2" && severity >= info)
    || (channel == "ChannelName3" && severity >= result)

  );

  // Add attributes
  logging::core::get()->add_global_attribute("Time", attrs::make_function(&tElapsedFormat));
  logging::core::get()->add_global_attribute("Rank", attrs::constant<int>(MpiWrap::getRank()));
}

L& L::get(){
  static L instance;
  return instance;
}

boost::shared_ptr<L::text_sink> L::sink(){
  return get().sink_;
}

double L::t0(){
  return get().t0_p;
}

double L::tElapsed(){
  return MPI_Wtime() - t0();
}

std::string L::tElapsedFormat(){
  std::stringstream ss;
  const int prec = std::numeric_limits<double>::digits10;
  ss << std::setw(prec + 2 + 6) << std::left << std::setprecision(prec) << tElapsed();
  return ss.str();
}

std::ostream& operator<< (std::ostream& strm, L::severity_level level)
{
    static const char* strings[] =
    {
        "DBG3",
        "DBG2",
        "DBG1",
        "CTRL",
        "INF3",
        "INF2",
        "INF1",
        "RSLT",
        "WARN",
        "ERRR",
        "CRIT"
    };

    if (static_cast< std::size_t >(level) < sizeof(strings) / sizeof(*strings))
        strm << strings[level];
    else
        strm << static_cast< int >(level);

    return strm;
}

: logger_t (typedef for boost::log::sources::severity_channel_logger<severity_level, std::string>)

class A {
public:
    logger_t logger;
    //other stuff here
    void function_which_does_logging();
};

L::logger_t A::logger(boost::log::keywords::channel = "ClassA");

void A::function_which_does_logging(){
    //do non logging related stuff
    BOOST_LOG_SEV(logger, L::result) << "the error is: " << 0.1234567890;
    //do non logging related stuff
}

,

int main(){
    L::logger_t logger(boost::log::keywords::channel = "init");
    BOOST_LOG_SEV(logger, L::critical) << "setting up logger" << std::scientific << std::setprecision(std::numeric_limits<double>::digits10 + 1);

    //do stuff
}
+4
2

@rhashimoto , / . , BOOST_LOG_SEV, , :

#define LOG_SCIENTIFIC(logger, sev) (BOOST_LOG_SEV(logger, sev) << std::scientific)

BOOST_LOG_SEV, . , , . BOOST_LOG_SEV, , . boost/log/sources/severity_feature.hpp BOOST_LOG_SEV :

//! An equivalent to BOOST_LOG_STREAM_SEV(logger, lvl)
#define BOOST_LOG_SEV(logger, lvl) BOOST_LOG_STREAM_SEV(logger, lvl)

BOOST_LOG_STREAM_SEV API , BOOST_LOG_SEV :

#define BOOST_LOG_SEV(logger, lvl) (BOOST_LOG_STREAM_SEV(logger, lvl) << std::scientific)

, , . , , , .

+5

, , . , , , (record_ostream.hpp record_ostream.cpp).

Boost Log , stream_provider. stream_provider - ( ) ostream . ostream - , . , Boost Log, , - - .

, . , :

static double f(double x) {
   BOOST_LOG(my_logger::get()) << "called f with " << x;
   return x;
}

int main() {
   BOOST_LOG(my_logger::get()) << std::scientific << "format flag";
   BOOST_LOG(my_logger::get()) << "top level " << f(0.01);
   return 0;
}

:

[2014-04-27 14:16:39.832008] [0x000007fff7a1c631] [info]    format flag
[2014-04-27 14:16:39.832616] [0x000007fff7a1c631] [info]    called f with 0.01
[2014-04-27 14:16:39.832630] [0x000007fff7a1c631] [info]    top level 1.000000e-02

, ( ) , ( ) . , , .

, @WilliamKunkel () - , . Boost, Boost 1.55:

#include <iomanip>

#define BOOST_LOG_DYN_LINK
#include <boost/log/sources/global_logger_storage.hpp>
#include <boost/log/sources/logger.hpp>
#include <boost/log/sources/record_ostream.hpp>

typedef boost::log::sources::logger logger_t;
BOOST_LOG_INLINE_GLOBAL_LOGGER_DEFAULT(my_logger, logger_t)

namespace boost {
   namespace log {
      namespace aux {
         template<>
         BOOST_FORCEINLINE record_pump<logger_t> make_record_pump(logger_t& lg, record& rec)
         {
            auto rp = record_pump<logger_t>(lg, rec);
            rp.stream() << std::scientific;
            return rp;
         }
      }
   }
}

int main() {
   BOOST_LOG(my_logger::get()) << "Logging number " << 0.01;
   return 0;
}

- , . , , , std::scientific, .

, Boost Log . .

, - boost::log::basic_formatting_stream, :

basic_formatting_ostream std::basic_ostream, operator<< , std::basic_ostream. basic_formatting_ostream operator<< .

, , , , -- operator<<.

+4

Source: https://habr.com/ru/post/1536618/

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