boost log to print source code file name and line

Question

I'm using Boost(1.55.0) Logging in my C++ application. I have been able to generate log of this format

[2014-Jul-15 10:47:26.137959]: <debug>  A regular message

I want to be able to add source file name and line number where the log is generated.

[2014-Jul-15 10:47:26.137959]: <debug> [filename:line_no] A regular message

example:

[2014-Jul-15 10:47:26.137959]: <debug> [helloworld.cpp : 12] A regular message

Source Code:

#include <boost/log/core.hpp>
#include <boost/log/trivial.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/sinks/text_file_backend.hpp>
#include <boost/log/utility/setup/file.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
#include <boost/log/sources/severity_logger.hpp>
#include <boost/log/sources/record_ostream.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/support/date_time.hpp>
#include <boost/log/attributes/attribute.hpp>
#include <boost/log/attributes/attribute_cast.hpp>
#include <boost/log/attributes/attribute_value.hpp>
#include <boost/make_shared.hpp>
#include <boost/property_tree/ptree.hpp>

namespace logging = boost::log;
namespace src = boost::log::sources;
namespace sinks = boost::log::sinks;
namespace keywords = boost::log::keywords;

void init()
{
    logging::add_file_log
    (
        keywords::file_name = "sample_%N.log",                                        /*< file name pattern >*/
        keywords::rotation_size = 10*1024*1204,                                 /*< rotate files every 10 MiB... >*/
        keywords::time_based_rotation = sinks::file::rotation_at_time_point(0, 0, 0), /*< ...or at midnight >*/
        keywords::format =
        (
            boost::log::expressions::stream
                << boost::log::expressions::format_date_time< boost::posix_time::ptime >("TimeStamp", "%Y-%m-%d_%H:%M:%S.%f")
                << ": <" << boost::log::trivial::severity << "> "
                << boost::log::expressions::smessage
        )
    );
}

int main(int, char*[])
{
    init();
    logging::add_common_attributes();

    using namespace logging::trivial;
    src::severity_logger< severity_level > lg;

    BOOST_LOG_SEV(lg, debug) << "A regular message";
    return 0;
}

Answer 1

As user2943014 pointed out, using scopes prints the line number where you opened that scope, not the line number where you emitted a log message using BOOST_LOG_SEV.

You can use attributes to log the line numbers etc at the place you actually logged.

Register global attributes in your logging initialization function:

using namespace boost::log;
core::get()->add_global_attribute("Line", attributes::mutable_constant<int>(5));
core::get()->add_global_attribute("File", attributes::mutable_constant<std::string>(""));
core::get()->add_global_attribute("Function", attributes::mutable_constant<std::string>(""));

Setting these attributes in your logging macro:

#define logInfo(methodname, message)                          \
  LOG_LOCATION;                                               \
  BOOST_LOG_SEV(_log, boost::log::trivial::severity_level::trace) << message

#define LOG_LOCATION                            \
  boost::log::attribute_cast<boost::log::attributes::mutable_constant<int>>(boost::log::core::get()->get_global_attributes()["Line"]).set(__LINE__); \
  boost::log::attribute_cast<boost::log::attributes::mutable_constant<std::string>>(boost::log::core::get()->get_global_attributes()["File"]).set(__FILE__); \
  boost::log::attribute_cast<boost::log::attributes::mutable_constant<std::string>>(boost::log::core::get()->get_global_attributes()["Function"]).set(__func__);

Not exactly beautiful, but it works and it was a long way for me. It's a pity boost doesn't offer this feature out of the box.

Answer 2

As Horus pointed out, you can use attributes to log file and line numbers. However it is best to avoid using multi-statements macros to avoid problems with expressions like this:

if (something)
   LOG_FILE_LINE(debug) << "It's true"; // Only the first statement is conditional!

You can do better creating a macro that leverages the underlying behavior of the Boost Log library. For example, BOOST_LOG_SEV is:

#define BOOST_LOG_SEV(logger, lvl) BOOST_LOG_STREAM_SEV(logger, lvl)
#define BOOST_LOG_STREAM_SEV(logger, lvl)\
    BOOST_LOG_STREAM_WITH_PARAMS((logger), (::boost::log::keywords::severity = (lvl)))

Using BOOST_LOG_STREAM_WITH_PARAMS you can set and get more attributes, like this:

// New macro that includes severity, filename and line number
#define CUSTOM_LOG(logger, sev) \
   BOOST_LOG_STREAM_WITH_PARAMS( \
      (logger), \
         (set_get_attrib("File", path_to_filename(__FILE__))) \
         (set_get_attrib("Line", __LINE__)) \
         (::boost::log::keywords::severity = (boost::log::trivial::sev)) \
   )

// Set attribute and return the new value
template<typename ValueType>
ValueType set_get_attrib(const char* name, ValueType value) {
   auto attr = logging::attribute_cast<attrs::mutable_constant<ValueType>>(logging::core::get()->get_thread_attributes()[name]);
   attr.set(value);
   return attr.get();
}

// Convert file path to only the filename
std::string path_to_filename(std::string path) {
   return path.substr(path.find_last_of("/\\")+1);
}

The complete source code is:

#include <boost/log/trivial.hpp>
#include <boost/log/sources/severity_logger.hpp>
#include <boost/log/utility/setup/file.hpp>
#include <boost/log/utility/setup/console.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
#include <boost/log/attributes/mutable_constant.hpp>
#include <boost/date_time/posix_time/posix_time_types.hpp>
#include <boost/log/support/date_time.hpp>
#include <boost/log/attributes/mutable_constant.hpp>

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

// New macro that includes severity, filename and line number
#define CUSTOM_LOG(logger, sev) \
   BOOST_LOG_STREAM_WITH_PARAMS( \
      (logger), \
         (set_get_attrib("File", path_to_filename(__FILE__))) \
         (set_get_attrib("Line", __LINE__)) \
         (::boost::log::keywords::severity = (boost::log::trivial::sev)) \
   )

// Set attribute and return the new value
template<typename ValueType>
ValueType set_get_attrib(const char* name, ValueType value) {
   auto attr = logging::attribute_cast<attrs::mutable_constant<ValueType>>(logging::core::get()->get_thread_attributes()[name]);
   attr.set(value);
   return attr.get();
}

// Convert file path to only the filename
std::string path_to_filename(std::string path) {
   return path.substr(path.find_last_of("/\\")+1);
}

void init() {
   // New attributes that hold filename and line number
   logging::core::get()->add_thread_attribute("File", attrs::mutable_constant<std::string>(""));
   logging::core::get()->add_thread_attribute("Line", attrs::mutable_constant<int>(0));

   logging::add_file_log (
    keywords::file_name = "sample.log",
    keywords::format = (
     expr::stream
      << expr::format_date_time<boost::posix_time::ptime>("TimeStamp", "%Y-%m-%d_%H:%M:%S.%f")
      << ": <" << boost::log::trivial::severity << "> "
      << '['   << expr::attr<std::string>("File")
               << ':' << expr::attr<int>("Line") << "] "
      << expr::smessage
    )
   );
   logging::add_common_attributes();
}

int main(int argc, char* argv[]) {
   init();
   src::severity_logger<logging::trivial::severity_level> lg;

   CUSTOM_LOG(lg, debug) << "A regular message";
   return 0;
}

This generate a log like this:

2015-10-15_15:25:12.743153: <debug> [main.cpp:61] A regular message

Answer 3

Define

namespace attrs = boost::logging::attributes;
namespace expr = boost::logging::expressions;

Add

<< expr::format_named_scope("Scope", keywords::format = "[%f:%l]")

to your keywords::format = (...) in init.

Then add

logging::core::get()->add_global_attribute("Scope", attrs::named_scope());

after add_common_attributes() in main.

Then just before the BOOST_LOG_SEV line add BOOST_LOG_NAMED_SCOPE("whatever").

BOOST_LOG_NAMED_SCOPE("whatever") creates a "scope" named "whatever". The scope is implemented by a unused variable that contains the scope name and the file and the line where the scope was defined.

The format_named_scope line specifies how a scope should be formatted in the log line. %f is the file, %l is the line and %n is the scope name.

Note that the file line that appears in the log record is the line where the macro BOOST_LOG_NAMED_SCOPE appears and not the line of the BOOST_LOG_SEV macro.

I am not aware of simple method to record the file and line without using the BOOST_LOG_NAMED_SCOPE.