Improvements

• Upgraded to the latest and greatest fmt library version 5.3.0.

• New API for default logger spdlog::trace(..), spdlog::debug(..), spdlog::info(..), etc. For convenience, spdlog now creates a default global logger (to stdout, colored and multithreaded). It can be used easily by calling spdlog::info(..), spdlog::debug(..), etc directly without any preparations.

  It's instance can be replaced to any other logger (shared_ptr):

  spdlog::set_default_logger(some_other_logger);
  spdlog::info("Use the new default logger");
  

• Alignment support in log patterns. Each pattern flag can be aligned by prepending a width number(upto 128). Use-(left align) or = (center align) to control the align side:

  align	meaning	example	result
  %<width><flag>	Align to the right	%8l	"    info"
  %-<width><flag>	Align to the left	%-8l	"info    "
  %=<width><flag>	Align to the center	%=8l	"  info  "

• Support for logging source filename, line number, and function name (thanks @possiblyhuman for contributing to this effort)

  flag	meaning	example
  %@	Source file and line (use SPDLOG_TRACE(..),SPDLOG_INFO(...) etc.)	my_file.cpp:123
  %s	Source file (use SPDLOG_TRACE(..),SPDLOG_INFO(...) etc.)	my_file.cpp
  %#	Source line (use SPDLOG_TRACE(..),SPDLOG_INFO(...) etc.)	123
  %!	Source function (use SPDLOG_TRACE(..),SPDLOG_INFO(...) etc. see tweakme for pretty-print)	my_func

• Support for compile time check of log levels using #define SPDLOG_ACTIVE_LEVEL <level>. Use LOG_TRACE(..), LOG_DEBUG(..), LOG_INFO(..), etc. to enable. Those macros check at compile time the log level and translate to empty statement if the log level is not high enough. Even if a log macro evaluate to a log call, the macro will check at runtime the level before evaluating its arguments. So for example the following won't evaluate some_costly_function() because the logger's level is error:

  #define SPDLOG_ACTIVE_LEVEL SPDLOG_LEVEL_DEBUG
  #include "spdlog/spdlog.h"
   ..
   spdlog::set_level(error);
   SPDLOG_DEBUG("Some costly arg: {}", some_costly_function());
  

• CMake improvements. Thanks @dpacbach (85b4d7c, f5dc166 ).

• Numerous small performance optimizations.

• Global option that disables global registration of loggers set_automatic_registration(bool). Thanks @pabloariasal (#892).

• Optimize logging of C strings by using string_view to avoid unnecessary copy. Thanks @peergynt (cb71fea0f6c9bb5722ca59e9b7917328217cfe5d).

• Use google benchmark to test latencies.

Fixes

• logger::error_handler() should be const (#881, thanks @shoreadmin for reporting)
• Cleanup header file: remove log_msg.h include from fmt_helper.h. Thanks @peergynt (1b391ccd062e013f6e0a991a3f37c3ce31eab87d)
• Fix log_msg constructor doesn't initialize all fields (#888. Thanks @curiouserrandy for reporting).
• Change log_msg&& to log_msg& params. Thanks @rwen2012 (794a636dd3cebd59e49ef3a0bfaf8bfffc729bdd)
• Fix typo in Android example. Thanks @ZaMaZaN4iK (f5a27250b1c701bb3317fa2ad6332fd893f26ab1)
• Fix Compiling error VS2017 #902 (Thanks @JaNurz for reprting).
• Fix thread id is prefixed with zeros #908 (Thanks @klrakiranpradeep for reporting).
• Fix OSX build. Thanks @DanielChabrowski (c7f42d1a4a1fe94ad11031a00858abdce2385cb2).
• Fix and optimize usage of fmt::internal::count_digits(..) for better support 32/64 bits. Thanks @DanielChabrowski (c7f42d1a4a1fe94ad11031a00858abdce2385cb2, f1ab6feba2fcd7d05aae8022787eeb76dbef41eb).
• Better handling of rotation errors (b64e4464a77caca658982b8fe919db05c4f29f36).
• Fix exceptions on file size calculation on Windows XP x64 and Windows Server 2003 x64. Thanks @lestera (#926).
• Do not attempt to default operator= when it is implicitly deleted. Thanks @dpacbach (63a475d88c2bf5be21bf6abd4a487909862e97de).
• Make an implicit cast from int --> uint32_t explicit. Thanks @dpacbach (a6152ebadd676d7f5a3a50e49eb995aa05d97112).
• Enable testing in the Travis config file. Thanks @dpacbach (f5dc16603ee97b77f9945e29b4f4864afdde2652).
• Fix the text alignment in the example. Thanks @bzindovic (d6086da4856df510657ffe4ef6b894e902b4b83).
• Fix typos. Thanks @peergynt (ce8cf1e152b3b51f4121f6b58ddcf3797090a1f4).
• Fix handling of external fmt lib in cmake. Thanks @cneumann (084bc72d90ccc829b8605297cbef4ef6cc3093b9).
• Fix VC WinRT compilation. Thanks @taniey for reporting (@948).
• Fix typo in file_helper.h. Thanks @brridder (fb702f989ff7141c71712e9d2c6a3fd642f7c206).